WorldWideScience

Sample records for optical communications group

  1. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    The CMS Communications Group, established at the start of 2010, has been busy in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure There are now 55 CMS Centres worldwide that are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin, is the centre of the CMS offline and computing operations, hosting dedicated analysis efforts such as during the CMS Heavy Ion lead-lead running. With a majority of CMS sub-detectors now operating in a “shifterless” mode, many monitoring operations are now routinely performed from there, rather than in the main Control Room at P5. The CMS Communications Group, CERN IT and the EVO team are providing excellent videoconferencing support for the rapidly-increasing number of CMS meetings. In parallel, CERN IT and ...

  2. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2010-01-01

    The CMS Communications Group, established at the start of 2010, has been strengthening the activities in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure The Communications Group has invested a lot of effort to support the operations needs of CMS. Hence, the CMS Centres where physicists work on remote CMS shifts, Data Quality Monitoring, and Data Analysis are running very smoothly. There are now 55 CMS Centres worldwide, up from just 16 at the start of CMS data-taking. The latest to join are Imperial College London, the University of Iowa, and the Università di Napoli. The CMS Centre@CERN in Meyrin, which is now full repaired after the major flooding at the beginning of the year, has been at the centre of CMS offline and computing operations, most recently hosting a large fraction of the CMS Heavy Ion community during the lead-lead run. A number of sub-detector shifts can now take pla...

  3. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    The CMS Communications Group has been busy in all three areas of its responsibility: (1) Communications Infrastructure, (2) Information Systems, and (3) Outreach and Education. Communications Infrastructure The 55 CMS Centres worldwide are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin, is the centre of the CMS Offline and Computing operations, and a number of subdetector shifts can now take place there, rather than in the main Control Room at P5. A new CMS meeting room has been equipped for videoconferencing in building 42, next to building 40. Our building 28 meeting room and the facilities at P5 will be refurbished soon and plans are underway to steadily upgrade the ageing equipment in all 15 CMS meeting rooms at CERN. The CMS evaluation of the Vidyo tool indicates that it is not yet ready to be considered as a potential replacement for EVO. The Communications Group provides the CMS-TV (web) cha...

  4. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2010-01-01

    The recently established CMS Communications Group, led by Lucas Taylor, has been busy in all three of its main are areas of responsibility: Communications Infrastructure, Information Systems, and Outreach and Education Communications Infrastructure The damage caused by the flooding of the CMS Centre@CERN on 21st December has been completely repaired and all systems are back in operation. Major repairs were made to the roofs, ceilings and one third of the floor had to be completely replaced. Throughout these works, the CMS Centre was kept operating and even hosted a major press event for first 7 TeV collisions, as described below. Incremental work behind the scenes is steadily improving the quality of the CMS communications infrastructure, particularly Webcasting, video conferencing, and meeting rooms at CERN. CERN/IT is also deploying a pilot service of a new videoconference tool called Vidyo, to assess whether it might provide an enhanced service at a lower cost, compared to the EVO tool currently in w...

  5. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2011-01-01

    Communications Infrastructure The 55 CMS Centres worldwide are well used by physicists working on remote CMS shifts, Computing operations, data quality monitoring, data analysis and outreach. The CMS Centre@CERN in Meyrin is particularly busy at the moment, hosting about 50 physicists taking part in the heavy-ion data-taking and analysis. Three new CMS meeting room will be equipped for videoconferencing in early 2012: 40/5B-08, 42/R-031, and 28/S-029. The CMS-TV service showing LHC Page 1, CMS Page 1, etc. (http://cmsdoc.cern.ch/cmscc/projector/index.jsp) is now also available for mobile devices: http://cern.ch/mcmstv. Figure 12: Screenshots of CMS-TV for mobile devices Information Systems CMS has a new web site: (http://cern.ch/cms) using a modern web Content Management System to ensure content and links are managed and updated easily and coherently. It covers all CMS sub-projects and groups, replacing the iCMS internal pages. It also incorporates the existing CMS public web site (http:/...

  6. COMMUNICATIONS GROUP

    CERN Multimedia

    L. Taylor

    2012-01-01

      Outreach and Education We are fortunate that our research has captured the public imagination, even though this inevitably puts us under the global media spotlight, as we saw with the Higgs seminar at CERN in December, which had 110,000 distinct webcast viewers. The media interest was huge with 71 media organisations registering to come to CERN to cover the Higgs seminar, which was followed by a press briefing with the DG and Spokespersons. This event resulted in about 2,000 generally positive stories in the global media. For this seminar, the CMS Communications Group prepared up-to-date news and public material, including links to the CMS results, animations and event displays [http://cern.ch/go/Ch8thttp://cern.ch/go/Ch8t]. There were 44,000 page-views on the CMS public website, with the Higgs news article being by far the most popular item. CMS event displays from iSpy are fast becoming the iconic media images, featuring on numerous major news outlets (BBC, CNN, MSN...) as well as in the sci...

  7. A novel QC-LDPC code based on the finite field multiplicative group for optical communications

    Science.gov (United States)

    Yuan, Jian-guo; Xu, Liang; Tong, Qing-zhen

    2013-09-01

    A novel construction method of quasi-cyclic low-density parity-check (QC-LDPC) code is proposed based on the finite field multiplicative group, which has easier construction, more flexible code-length code-rate adjustment and lower encoding/decoding complexity. Moreover, a regular QC-LDPC(5334,4962) code is constructed. The simulation results show that the constructed QC-LDPC(5334,4962) code can gain better error correction performance under the condition of the additive white Gaussian noise (AWGN) channel with iterative decoding sum-product algorithm (SPA). At the bit error rate (BER) of 10-6, the net coding gain (NCG) of the constructed QC-LDPC(5334,4962) code is 1.8 dB, 0.9 dB and 0.2 dB more than that of the classic RS(255,239) code in ITU-T G.975, the LDPC(32640,30592) code in ITU-T G.975.1 and the SCG-LDPC(3969,3720) code constructed by the random method, respectively. So it is more suitable for optical communication systems.

  8. The application of the extending symmetry group approach in optical soliton communication

    International Nuclear Information System (INIS)

    Ruan Hangyu; Li Huijun; Chen Yixin

    2005-01-01

    A systematic method which is based on the classical Lie group reduction is used to find the novel exact solution of the nonlinear Schroedinger equation (NLS) with distributed dispersion, nonlinearity and gain or loss. We study the transformations between the standard NLS equation and the NLS equations with distributed dispersion, nonlinearity and gain or loss. Appropriate solitary wave solutions can be applied to discuss soliton propagation in optical fibres, and the amplification and compression of pulses in optical fibre amplifiers

  9. Advanced digital optical communications

    CERN Document Server

    Binh, Le Nguyen

    2015-01-01

    This book provides a fundamental understanding of digital communication applications in optical communication technologies. Emphasizing operation principles versus mathematical analysis, the Second Edition includes new coverage of superchannel optical transmission systems, metropolitan and long-haul optical systems and networks, and Nyquist pulse shaping and high spectral efficiency of optical transmission systems, as well as new homework problems and examples. Featuring theoretical foundations as well as practical case studies, the text focuses on enhancements to digital technologies that are

  10. Fibre-optic communications

    CERN Document Server

    Lecoy, Pierre

    2010-01-01

    This book describes in a comprehensive manner the components and systems of fiber optic communications and networks. The first section explains the theory of multimode and single-mode fibers, then the technological features, including manufacturing, cabling, and connecting. The second section describes the various components (passive and active optical components, integrated optics, opto-electronic transmitters and receivers, and optical amplifiers) used in fiber optic systems. Finally, the optical transmission system design is explained, and applications to optical networks and fiber optic se

  11. Communication in Organizational Groups

    OpenAIRE

    Monica RADU

    2007-01-01

    Organizational group can be defined as some persons between who exist interactive connections (functional, communication, affective, normative type). Classification of these groups can reflect the dimension, type of relationship or type of rules included. Organizational groups and their influence over the individual efficiency and the efficiency of the entire group are interconnected. Spontaneous roles in these groups sustain the structure of the relationship, and the personality of each indi...

  12. Construction method of QC-LDPC codes based on multiplicative group of finite field in optical communication

    Science.gov (United States)

    Huang, Sheng; Ao, Xiang; Li, Yuan-yuan; Zhang, Rui

    2016-09-01

    In order to meet the needs of high-speed development of optical communication system, a construction method of quasi-cyclic low-density parity-check (QC-LDPC) codes based on multiplicative group of finite field is proposed. The Tanner graph of parity check matrix of the code constructed by this method has no cycle of length 4, and it can make sure that the obtained code can get a good distance property. Simulation results show that when the bit error rate ( BER) is 10-6, in the same simulation environment, the net coding gain ( NCG) of the proposed QC-LDPC(3 780, 3 540) code with the code rate of 93.7% in this paper is improved by 2.18 dB and 1.6 dB respectively compared with those of the RS(255, 239) code in ITU-T G.975 and the LDPC(3 2640, 3 0592) code in ITU-T G.975.1. In addition, the NCG of the proposed QC-LDPC(3 780, 3 540) code is respectively 0.2 dB and 0.4 dB higher compared with those of the SG-QC-LDPC(3 780, 3 540) code based on the two different subgroups in finite field and the AS-QC-LDPC(3 780, 3 540) code based on the two arbitrary sets of a finite field. Thus, the proposed QC-LDPC(3 780, 3 540) code in this paper can be well applied in optical communication systems.

  13. Optical Communications Channel Combiner

    Science.gov (United States)

    Quirk, Kevin J.; Quirk, Kevin J.; Nguyen, Danh H.; Nguyen, Huy

    2012-01-01

    NASA has identified deep-space optical communications links as an integral part of a unified space communication network in order to provide data rates in excess of 100 Mb/s. The distances and limited power inherent in a deep-space optical downlink necessitate the use of photon-counting detectors and a power-efficient modulation such as pulse position modulation (PPM). For the output of each photodetector, whether from a separate telescope or a portion of the detection area, a communication receiver estimates a log-likelihood ratio for each PPM slot. To realize the full effective aperture of these receivers, their outputs must be combined prior to information decoding. A channel combiner was developed to synchronize the log-likelihood ratio (LLR) sequences of multiple receivers, and then combines these into a single LLR sequence for information decoding. The channel combiner synchronizes the LLR sequences of up to three receivers and then combines these into a single LLR sequence for output. The channel combiner has three channel inputs, each of which takes as input a sequence of four-bit LLRs for each PPM slot in a codeword via a XAUI 10 Gb/s quad optical fiber interface. The cross-correlation between the channels LLR time series are calculated and used to synchronize the sequences prior to combining. The output of the channel combiner is a sequence of four-bit LLRs for each PPM slot in a codeword via a XAUI 10 Gb/s quad optical fiber interface. The unit is controlled through a 1 Gb/s Ethernet UDP/IP interface. A deep-space optical communication link has not yet been demonstrated. This ground-station channel combiner was developed to demonstrate this capability and is unique in its ability to process such a signal.

  14. Free space optical communication

    CERN Document Server

    Kaushal, Hemani; Kar, Subrat

    2017-01-01

    This book provides an in-depth understanding of free space optical (FSO) communication with a particular emphasis on optical beam propagation through atmospheric turbulence. The book is structured in such a way that it provides a basic framework for the beginners and also gives a concise description from a designer’s perspective. The book provides an exposure to FSO technology, fundamental limitations, design methodologies, system trade-offs, acquisition, tracking and pointing (ATP) techniques and link-feasibility analysis. The contents of this book will be of interest to professionals and researchers alike. The book may also be used as a textbook for engineering coursework and professional training.

  15. Quantum Secure Group Communication.

    Science.gov (United States)

    Li, Zheng-Hong; Zubairy, M Suhail; Al-Amri, M

    2018-03-01

    We propose a quantum secure group communication protocol for the purpose of sharing the same message among multiple authorized users. Our protocol can remove the need for key management that is needed for the quantum network built on quantum key distribution. Comparing with the secure quantum network based on BB84, we show our protocol is more efficient and securer. Particularly, in the security analysis, we introduce a new way of attack, i.e., the counterfactual quantum attack, which can steal information by "invisible" photons. This invisible photon can reveal a single-photon detector in the photon path without triggering the detector. Moreover, the photon can identify phase operations applied to itself, thereby stealing information. To defeat this counterfactual quantum attack, we propose a quantum multi-user authorization system. It allows us to precisely control the communication time so that the attack can not be completed in time.

  16. OPTICAL WIRELESS COMMUNICATION SYSTEM

    Directory of Open Access Journals (Sweden)

    JOSHUA L.Y. CHIENG

    2016-02-01

    Full Text Available The growing demand of bandwidth in this modern internet age has been testing the existing telecommunication infrastructures around the world. With broadband speeds moving towards the region of Gbps and Tbps, many researches have begun on the development of using optical wireless technology as feasible and future methods to the current wireless technology. Unlike the existing radio frequency wireless applications, optical wireless uses electromagnetic spectrums that are unlicensed and free. With that, this project aim to understand and gain better understanding of optical wireless communication system by building an experimental and simulated model. The quality of service and system performance will be investigated and reviewed. This project employs laser diode as the propagation medium and successfully transferred audio signals as far as 15 meters. On its quality of service, results of the project model reveal that the bit error rate increases, signal-to-noise ratio and quality factor decreases as the link distance between the transmitter and receiver increases. OptiSystem was used to build the simulated model and MATLAB was used to assist signal-to-noise ratio calculations. By comparing the simulated and experimental receiver’s power output, the experimental model’s efficiency is at 66.3%. Other than the system’s performance, challenges and factors affecting the system have been investigated and discussed. Such challenges include beam divergence, misalignment and particle absorption.

  17. Enhancing Social Communication Between Groups

    NARCIS (Netherlands)

    T. Stevens; P. Hughes (Peter); D. Williams; I. Craigie; I. Kegel; P.S. Cesar Garcia (Pablo Santiago); A.J. Jansen (Jack); M.F. Usrsu; M. Frantzis; N. Farber; M. Lutzky; S. Vogel

    2010-01-01

    htmlabstractThis paper describes a prototype software platform that supports advanced communications services, specifically services enabling effective group-to-group communications with a social purpose, between remote homes. The architecture, the individual components, their interfaces, and the

  18. Optical space communication: An overview

    International Nuclear Information System (INIS)

    Jain, V.K.

    1994-01-01

    In this paper, importance of the optical space communication has been highlighted. Its merits and demerits over the conventional microwave system has been presented. In contrast to coherent systems, use of an optical preamplifier in direct detection system has been emphasized. Status of some of the ongoing/future space communication projects has been given. (author). 9 refs, 5 figs

  19. Communicating to heterogeneous target groups

    DEFF Research Database (Denmark)

    Pedersen, Karsten

    very often have to communicate to rather heterogeneous target groups that have little more in common than a certain geographical habitat. That goes against most schoolbook teaching in the field of communication, but is none the less the terms with which that kind of communication has to live...

  20. Fibre optic communication key devices

    CERN Document Server

    Grote, Norbert

    2017-01-01

    The book gives an in-depth description of key devices of current and next generation fibre optic communication networks. Devices treated include semiconductor lasers, optical amplifiers, modulators, wavelength filters and other passives, detectors, all-optical switches, but relevant properties of optical fibres and network aspects are included as well. The presentations include the physical principles underlying the various devices, technologies used for their realization, typical performance characteristics and limitations, but development trends towards more advanced components are also illustrated. This new edition of a successful book was expanded and updated extensively. The new edition covers among others lasers for optical communication, optical switches, hybrid integration, monolithic integration and silicon photonics. The main focus is on Indium phosphide-based structures but silicon photonics is included as well. The book covers relevant principles, state-of-the-art implementations, status of curren...

  1. Transceiver optics for interplanetary communications

    Science.gov (United States)

    Roberts, W. T.; Farr, W. H.; Rider, B.; Sampath, D.

    2017-11-01

    In-situ interplanetary science missions constantly push the spacecraft communications systems to support successively higher downlink rates. However, the highly restrictive mass and power constraints placed on interplanetary spacecraft significantly limit the desired bandwidth increases in going forward with current radio frequency (RF) technology. To overcome these limitations, we have evaluated the ability of free-space optical communications systems to make substantial gains in downlink bandwidth, while holding to the mass and power limits allocated to current state-of-the-art Ka-band communications systems. A primary component of such an optical communications system is the optical assembly, comprised of the optical support structure, optical elements, baffles and outer enclosure. We wish to estimate the total mass that such an optical assembly might require, and assess what form it might take. Finally, to ground this generalized study, we should produce a conceptual design, and use that to verify its ability to achieve the required downlink gain, estimate it's specific optical and opto-mechanical requirements, and evaluate the feasibility of producing the assembly.

  2. Optical fiber communications

    CERN Document Server

    Keiser, Gerd

    2008-01-01

    The fourth edition of this popular text and reference book presents the fundamental principles for understanding and applying optical fiber technology to sophisticated modern telecommunication systems. Optical-fiber-based telecommunication networks have become a major information-transmission-system, with high capacity links encircling the globe in both terrestrial and undersea installations. Numerous passive and active optical devices within these links perform complex transmission and networking functions in the optical domain, such as signal amplification, restoration, routing, and switching. Along with the need to understand the functions of these devices comes the necessity to measure both component and network performance, and to model and stimulate the complex behavior of reliable high-capacity networks.

  3. Communication from ST Group

    CERN Document Server

    TS Department

    2008-01-01

    Please note that owing the preparations for the Open Days, the FM Group will not able to handle specific requests for waste collection from 2nd to 6th of April, nor removal or PC transport requests between the 31 March and 11 April. We kindly ask you to plan the collection of all types of waste and any urgent transport of office furniture or PCs before 31 March. Waste collection requests must be made by contacting FM Support on 77777 or at the e-mail address mailto:Fm.Support@cern.ch; removal of office furniture or PC transport requests must be made using the EDH ‘Transport request’ form (select "Removals" or "PC transport" from the drop-down menu). For any question concerning the sorting of waste, please consult the following web site: http://dechets-waste.web.cern.ch/dechets-waste/ Thank you for your understanding and collaboration. TS/FM Group

  4. Communication from ST Group

    CERN Multimedia

    TS Department

    2008-01-01

    In order to prepare the organization of the Open Days, please note that FM Group will not able to take into account either specific requests for waste collection from 2nd to 6th of April, either removal or PC transport requests between the 31st and the 11th of March. We kindly ask you to plan the collection of any type of waste and the urgent transport of office furniture or PC before the 31st of March. Waste collection requests shall be formulated contacting FM Support at 77777 or at the email address mailto:Fm.Support@cern.ch; removal of office furniture or PC transport requests must be made using the EDH ‘Transport request’ form selecting the "Removals" or the "PC transport" category from the drop-down menu. For any question concerning the waste sorting, please consult the following web address: http://dechets-waste.web.cern.ch/dechets-waste/. Thank you for your understanding and collaboration. TS/FM Group

  5. Optical Communication over Plastic Optical Fibers Integrated Optical Receiver Technology

    CERN Document Server

    Atef, Mohamed

    2013-01-01

    This book presents high-performance data transmission over plastic optical fibers (POF) using integrated optical receivers having good properties with multilevel modulation, i.e. a higher sensitivity and higher data rate transmission over a longer plastic optical fiber length. Integrated optical receivers and transmitters with high linearity are introduced for multilevel communication. For binary high-data rate transmission over plastic optical fibers, an innovative receiver containing an equalizer is described leading also to a high performance of a plastic optical fiber link. The cheap standard PMMA SI-POF (step-index plastic optical fiber) has the lowest bandwidth and the highest attenuation among multimode fibers. This small bandwidth limits the maximum data rate which can be transmitted through plastic optical fibers. To overcome the problem of the plastic optical fibers high transmission loss, very sensitive receivers must be used to increase the transmitted length over POF. The plastic optical fiber li...

  6. Fiber-optic communication systems

    CERN Document Server

    Agrawal, Govind P

    2010-01-01

    This book provides a comprehensive account of fiber-optic communication systems. The 3rd edition of this book is used worldwide as a textbook in many universities. This 4th edition incorporates recent advances that have occurred, in particular two new chapters. One deals with the advanced modulation formats (such as DPSK, QPSK, and QAM) that are increasingly being used for improving spectral efficiency of WDM lightwave systems. The second chapter focuses on new techniques such as all-optical regeneration that are under development and likely to be used in future communication systems. All othe

  7. Fibre Optic Communication Key Devices

    CERN Document Server

    Grote, Norbert

    2012-01-01

    The book gives an in-depth description of the key devices of current and next generation fibre optic communication networks. In particular, the book covers devices such as semiconductor lasers, optical amplifiers, modulators, wavelength filters, and detectors but the relevant properties of optical fibres as well. The presentations include the physical principles underlying the various devices, the technologies used for the realization of the different devices, typical performance characteristics and limitations, and development trends towards more advanced components are also illustrated. Thus the scope of the book spans relevant principles, state-of-the-art implementations, the status of current research and expected future components.

  8. Optical wireless communications for micromachines

    Science.gov (United States)

    O'Brien, Dominic C.; Yuan, Wei Wen; Liu, Jing Jing; Faulkner, Grahame E.; Elston, Steve J.; Collins, Steve; Parry-Jones, Lesley A.

    2006-08-01

    A key challenge for wireless sensor networks is minimizing the energy required for network nodes to communicate with each other, and this becomes acute for self-powered devices such as 'smart dust'. Optical communications is a potentially attractive solution for such devices. The University of Oxford is currently involved in a project to build optical wireless links to smart dust. Retro-reflectors combined with liquid crystal modulators can be integrated with the micro-machine to create a low power transceiver. When illuminated from a base station a modulated beam is returned, transmitting data. Data from the base station can be transmitted using modulation of the illuminating beam and a receiver at the micro-machine. In this paper we outline the energy consumption and link budget considerations in the design of such micro-machines, and report preliminary experimental results.

  9. Phase-Modulated Optical Communication Systems

    CERN Document Server

    Ho, Keang-Po

    2005-01-01

    Fiber-optic communication systems have revolutionized our telecommunication infrastructures – currently, almost all telephone land-line, cellular, and internet communications must travel via some form of optical fibers. In these transmission systems, neither the phase nor frequency of the optical signal carries information – only the intensity of the signal is used. To transmit more information in a single optical carrier, the phase of the optical carrier must be explored. As a result, there is renewed interest in phase-modulated optical communications, mainly in direct-detection DPSK signals for long-haul optical communication systems. When optical amplifiers are used to maintain certain signal level among the fiber link, the system is limited by amplifier noises and fiber nonlinearities. Phase-Modulated Optical Communication Systems surveys this newly popular area, covering the following topics: The transmitter and receiver for phase-modulated coherent lightwave systems Method for performance analysis o...

  10. All-optical virtual private network and ONUs communication in optical OFDM-based PON system.

    Science.gov (United States)

    Zhang, Chongfu; Huang, Jian; Chen, Chen; Qiu, Kun

    2011-11-21

    We propose and demonstrate a novel scheme, which enables all-optical virtual private network (VPN) and all-optical optical network units (ONUs) inter-communications in optical orthogonal frequency-division multiplexing-based passive optical network (OFDM-PON) system using the subcarrier bands allocation for the first time (to our knowledge). We consider the intra-VPN and inter-VPN communications which correspond to two different cases: VPN communication among ONUs in one group and in different groups. The proposed scheme can provide the enhanced security and a more flexible configuration for VPN users compared to the VPN in WDM-PON or TDM-PON systems. The all-optical VPN and inter-ONU communications at 10-Gbit/s with 16 quadrature amplitude modulation (16 QAM) for the proposed optical OFDM-PON system are demonstrated. These results verify that the proposed scheme is feasible. © 2011 Optical Society of America

  11. The Holy Grail of quantum optical communication

    International Nuclear Information System (INIS)

    García-Patrón, Raúl; Navarrete-Benlloch, Carlos; Lloyd, Seth; Shapiro, Jeffrey H.; Cerf, Nicolas J.

    2014-01-01

    Optical parametric amplifiers together with phase-shifters and beamsplitters have certainly been the most studied objects in the field of quantum optics. Despite such an intensive study, optical parametric amplifiers still keep secrets from us. We will show how they hold the answer to one of the oldest problems in quantum communication theory, namely the calculation of the optimal communication rate of optical channels

  12. Practical impact of group communication theory

    OpenAIRE

    Schiper, A.

    2003-01-01

    Practical impact of group communication theory Andre Schiper Group communication is an important topic in fault-tolerant distributed applications. The paper summarizes the main contributions of practical importance that contributed to our current understanding of group communication. These contributions are classified into ''abstractions'' and ''specifications'', ''paradigms'', ''system models'', ''algorithms'', and ''theoretical results''. Some open issues are discussed at the end of the ...

  13. Essentials of modern optical fiber communication

    CERN Document Server

    Noé, Reinhold

    2016-01-01

    This is a concise introduction into optical fiber communication. It covers important aspects from the physics of optical wave propagation and amplification to the essentials of modulation formats and receivers. The combination of a solid coverage of necessary fundamental theory with an in-depth discussion of recent relevant research results enables the reader to design modern optical fiber communication systems. The book serves both graduate students and professionals. It includes many worked examples with solutions for lecturers. For the second edition, Reinhold Noé made many changes and additions throughout the text so that this concise book presents the essentials of optical fiber communication in an easy readable and understandable way.

  14. Free Space Optical Communication for Tactical Operations

    Science.gov (United States)

    2016-09-01

    higher energy level to a lower energy level. The photons are focused to optical lenses before transmission into the air medium. The primary purpose...Security of a free space optical transmission . (n.d.). SONA Optical Wireless , [Online]. Available: http://htcbn.com/HTC_Profile_CD/fSONA/APPNOTE...almost always require on-the-move wireless communications. Radio frequency (RF) communication is used to fill the gap, but RF systems are hard pressed to

  15. Diffractive optical elements for space communication terminals

    OpenAIRE

    Herzig, Hans-Peter; Ehbets, Peter; Teijido, Juan M.; Weible, Kenneth J.; Heimbeck, Hans-Joerg

    2007-01-01

    The potential of diffractive optical elements for advanced laser communication terminals has been investigated. Applications include beam shaping of high- power laser diode arrays, optical filter elements for position detection and hybrid (refractive/diffractive) elements. In addition, we present a design example of a miniaturized terminal including diffractive optics.

  16. Atmospheric free-space coherent optical communications with adaptive optics

    Science.gov (United States)

    Ting, Chueh; Zhang, Chengyu; Yang, Zikai

    2017-02-01

    Free-space coherent optical communications have a potential application to offer last mile bottleneck solution in future local area networks (LAN) because of their information carrier, information security and license-free status. Coherent optical communication systems using orthogonal frequency division multiplexing (OFDM) digital modulation are successfully demonstrated in a long-haul tens Giga bits via optical fiber, but they are not yet available in free space due to atmospheric turbulence-induced channel fading. Adaptive optics is recognized as a promising technology to mitigate the effects of atmospheric turbulence in free-space optics. In this paper, a free-space coherent optical communication system using an OFDM digital modulation scheme and adaptive optics (FSO OFDM AO) is proposed, a Gamma-Gamma distribution statistical channel fading model for the FSO OFDM AO system is examined, and FSO OFDM AO system performance is evaluated in terms of bit error rate (BER) versus various propagation distances.

  17. Fiber Optic Communications Technology. A Status Report.

    Science.gov (United States)

    Hull, Joseph A.

    Fiber optic communications (communications over very pure glass transmission channels of diameter comparable to a human hair) is an emerging technology which promises most improvements in communications capacity at reasonable cost. The fiber transmission system offers many desirable characteristics representing improvements over conventional…

  18. Optical Filter Assembly for Interplanetary Optical Communications

    Science.gov (United States)

    Chen, Yijiang; Hemmati, Hamid

    2013-01-01

    Ground-based, narrow-band, high throughput optical filters are required for optical links from deep space. We report on the development of a tunable filter assembly that operates at telecommunication window of 1550 nanometers. Low insertion loss of 0.5 decibels and bandwidth of 90 picometers over a 2000 nanometers operational range of detectors has been achieved.

  19. Optical smart card using semipassive communication.

    Science.gov (United States)

    Glaser, I; Green, Shlomo; Dimkov, Ilan

    2006-03-15

    An optical secure short-range communication system is presented. The mobile unit (optical smart card) of this system utilizes a retroreflector with an optical modulator, using light from the stationary unit; this mobile unit has very low power consumption and can be as small as a credit card. Such optical smart cards offer better security than RF-based solutions, yet do not require physical contact. Results from a feasibility study model are included.

  20. Full-duplex optical communication system

    Science.gov (United States)

    Shay, Thomas M. (Inventor); Hazzard, David A. (Inventor); Horan, Stephen (Inventor); Payne, Jason A. (Inventor)

    2004-01-01

    A method of full-duplex electromagnetic communication wherein a pair of data modulation formats are selected for the forward and return data links respectively such that the forward data electro-magnetic beam serves as a carrier for the return data. A method of encoding optical information is used wherein right-hand and left-hand circular polarizations are assigned to optical information to represent binary states. An application for an earth to low earth orbit optical communications system is presented which implements the full-duplex communication and circular polarization keying modulation format.

  1. Deep space optical communication via relay satellite

    Science.gov (United States)

    Dolinar, S.; Vilnrotter, V.; Gagliardi, R.

    1981-01-01

    The application of optical communications for a deep space link via an earth-orbiting relay satellite is discussed. The system uses optical frequencies for the free-space channel and RF links for atmospheric transmission. The relay satellite is in geostationary orbit and contains the optics necessary for data processing and formatting. It returns the data to earth through the RF terrestrial link and also transmits an optical beacon to the satellite for spacecraft return pointing and for the alignment of the transmitting optics. Future work will turn to modulation and coding, pointing and tracking, and optical-RF interfacing.

  2. The handbook of optical communication networks

    CERN Document Server

    Ilyas, Mohammad

    2003-01-01

    The Handbook of Optical Communication Networks presents comprehensive, up-to-date technical information on integrated, state-of-the-art optical networks. Beginning with an in-depth intoduction to the field, top international authorities explore every major aspect of optical networks, from basic concepts to research grade material. Their discussions cover all of the essential topics, including protocols, resource management, routing and wavelength assignment in WDM networks, connection management, survivability, enabling technologies, and future trends.

  3. High Spectral Density Optical Communication Technologies

    CERN Document Server

    Nakazawa, Masataka; Miyazaki, Tetsuya

    2010-01-01

    The latest hot topics of high-spectral density optical communication systems using digital coherent optical fibre communication technologies are covered by this book. History and meaning of a "renaissance" of the technology, requirements to the Peta-bit/s class "new generation network" are also covered in the first part of this book. The main topics treated are electronic and optical devices, digital signal processing including forward error correction, modulation formats as well as transmission and application systems. The book serves as a reference to researchers and engineers.

  4. Fiber optic communications fundamentals and applications

    CERN Document Server

    Kumar, Shiva

    2014-01-01

    Fiber-optic communication systems have advanced dramatically over the last four decades, since the era of copper cables, resulting in low-cost and high-bandwidth transmission. Fiber optics is now the backbone of the internet and long-distance telecommunication. Without it we would not enjoy the benefits of high-speed internet, or low-rate international telephone calls. This book introduces the basic concepts of fiber-optic communication in a pedagogical way. The important mathematical results are derived by first principles rather than citing research articles. In addition, physical interpre

  5. Scalable and Anonymous Group Communication with MTor

    Directory of Open Access Journals (Sweden)

    Lin Dong

    2016-04-01

    Full Text Available This paper presents MTor, a low-latency anonymous group communication system. We construct MTor as an extension to Tor, allowing the construction of multi-source multicast trees on top of the existing Tor infrastructure. MTor does not depend on an external service to broker the group communication, and avoids central points of failure and trust. MTor’s substantial bandwidth savings and graceful scalability enable new classes of anonymous applications that are currently too bandwidth-intensive to be viable through traditional unicast Tor communication-e.g., group file transfer, collaborative editing, streaming video, and real-time audio conferencing.

  6. Multilevel Modulation formats for Optical Communication

    DEFF Research Database (Denmark)

    Jensen, Jesper Bevensee

    2008-01-01

    This thesis studies the use of multilevel modulation formats for optical communication systems. Multilevel modulation is an attractive method of increasing the spectral efficiency of optical communication systems. Various modulation formats employing phase modulation, amplitude modulation...... or a combination of the two have been studied. The use of polarization multiplexing (PolMux) to double the bit rate has also been investigated. The impact of transmission impairments such as chromatic dispersion, self phase modulation and cross phase modulation has been investigated. The feasibility of multilevel...... modulation for network oriented scenarios has been demonstrated....

  7. DSA for Secured Optical Communication

    International Nuclear Information System (INIS)

    Shojaei, A.A.; Amiri, I.S.

    2011-01-01

    Novel system of dark soliton array (DSA) for secured communication is proposed. The DSA are obtained by using a series micro ring resonators where the input wavelengths of λ 1 = 1516 nm, λ 2 = 1518 nm and λ 3 =1520 nm propagate inside the system and finally will be multiplexed. For security applications, the DSA can be tuned and amplified. The use of DSA for high capacity can be realized by using proposed secured system. (author)

  8. The new Education and Communication group

    CERN Multimedia

    Patrice Loïez

    2003-01-01

    Since the start of the year, CERN's communication teams have been brought together under one umbrella for the sake of greater coherence and better coordination. The new Education and Communication group in Education and Technology Transfer division is led by James Gillies, former Editor of the CERN Courier. EC group comprises four sections: Events and Sponsoring, External Communication, Publications, and Visits and Educational Programmes. Its goal is to inform not only the general public but also the community of CERN staff, physicists and teachers about the research, events, innovations and major decisions of the Organization. Photo 01: The new Education and Communication group with ETT division leader Juan-Antonio Rubio (back row, centre).

  9. Gigahertz Optical Data Transmitters for Laser Communications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Wireless optical communication systems have gone through considerable development in the past few years, as optical components have experiences important technologic...

  10. OPTICAL COMMUNICATION: Simulation of autosoliton optical pulses in high-speed fibreoptic communication systems

    Science.gov (United States)

    Latkin, A. I.

    2005-03-01

    The propagation of a pulse in a fibreoptic communication link with periodically included regenerators — nonlinear optical loop mirrors, is studied. The autosoliton propagation regime of the optical pulse is revealed. It is shown that the inclusion of a ring mirror to the communication link leads to a substantial increase in the transmission distance of the pulse at a small negative average dispersion in the link.

  11. Numerical modelling of multimode fibre-optic communication lines

    Energy Technology Data Exchange (ETDEWEB)

    Sidelnikov, O S; Fedoruk, M P [Novosibirsk State University, Novosibirsk (Russian Federation); Sygletos, S; Ferreira, F [Aston University, England, Birmingham, B4 7ET (United Kingdom)

    2016-01-31

    The results of numerical modelling of nonlinear propagation of an optical signal in multimode fibres with a small differential group delay are presented. It is found that the dependence of the error vector magnitude (EVM) on the differential group delay can be reduced by increasing the number of ADC samples per symbol in the numerical implementation of the differential group delay compensation algorithm in the receiver. The possibility of using multimode fibres with a small differential group delay for data transmission in modern digital communication systems is demonstrated. It is shown that with increasing number of modes the strong coupling regime provides a lower EVM level than the weak coupling one. (fibre-optic communication lines)

  12. Radio Science from an Optical Communications Signal

    Science.gov (United States)

    Moision, Bruce; Asmar, Sami; Oudrhiri, Kamal

    2013-01-01

    NASA is currently developing the capability to deploy deep space optical communications links. This creates the opportunity to utilize the optical link to obtain range, doppler, and signal intensity estimates. These may, in turn, be used to complement or extend the capabilities of current radio science. In this paper we illustrate the achievable precision in estimating range, doppler, and received signal intensity of an non-coherent optical link (the current state-of-the-art for a deep-space link). We provide a joint estimation algorithm with performance close to the bound. We draw comparisons to estimates based on a coherent radio frequency signal, illustrating that large gains in either precision or observation time are possible with an optical link.

  13. Optical wireless communications an emerging technology

    CERN Document Server

    Capsoni, Carlo; Ghassemlooy, Zabih; Boucouvalas, Anthony; Udvary, Eszter

    2016-01-01

    This book focuses on optical wireless communications (OWC), an emerging technology with huge potential for the provision of pervasive and reliable next-generation communications networks. It shows how the development of novel and efficient wireless technologies can contribute to a range of transmission links essential for the heterogeneous networks of the future to support various communications services and traffic patterns with ever-increasing demands for higher data-transfer rates. The book starts with a chapter reviewing the OWC field, which explains different sub-technologies (visible-light, ultraviolet (UV) and infrared (IR) communications) and introduces the spectrum of application areas (indoor, vehicular, terrestrial, underwater, intersatellite, deep space, etc.). This provides readers with the necessary background information to understand the specialist material in the main body of the book, which is in four parts. The first of these deals with propagation modelling and channel characterization of ...

  14. Optical wireless communication in data centers

    Science.gov (United States)

    Arnon, Shlomi

    2018-01-01

    In the last decade data centers have become a crucial element in modern human society. However, to keep pace with internet data rate growth, new technologies supporting data center should develop. Integration of optical wireless communication (OWC) in data centers is one of the proposed technologies as augmented technology to the fiber network. One implementation of the OWC technology is deployment of optical wireless transceiver on top of the existing cable/fiber network as extension to the top of rack (TOR) switch; in this way, a dynamic and flexible network is created. Optical wireless communication could reduce energy consumption, increase the data rate, reduce the communication latency, increase flexibility and scalability, and reduce maintenance time and cost, in comparison to extra fiber network deployment. In this paper we review up to date literature in the field, propose an implementation scheme of OWC network, discuss ways to reduce energy consumption by parallel link communication and report preliminary measurement result of university data center environment.

  15. Learning to communicate risk information in groups

    Directory of Open Access Journals (Sweden)

    Hsuchi Ting

    2008-12-01

    Full Text Available Despite vigorous research on risk communication, little is known about the social forces that drive these choices. Erev, Wallsten, and Neal (1991 showed that forecasters learn to select verbal or numerical probability estimates as a function of which mode yields on average the larger group payoffs. We extend the result by investigating the effect of group size on the speed with which forecasters converge on the better communication mode. On the basis of social facilitation theory we hypothesized that small groups induce less arousal and anxiety among their members than do large groups when performing new tasks, and therefore that forecasters in small groups will learn the better communication mode more quickly. This result obtained in Experiment 1, which compared groups of size 3 to groups of size 5 or 6. To test whether social loafing rather than social facilitation was mediating the effects, Experiment 2 compared social to personal feedback holding group size constant at 3 members. Learning was faster in the personal feedback condition, suggesting that social facilitation rather than loafing underlay the results.

  16. Discovery deep space optical communications (DSOC) transceiver

    Science.gov (United States)

    Roberts, W. Thomas

    2017-02-01

    NASA's 22 cm diameter Deep Space Optical Communications (DSOC) Transceiver is designed to provide a bidirectional optical link between a spacecraft in the inner solar system and an Earth-based optical ground station. This design, optimized for operation across a wide range of illumination conditions, is focused on minimizing blinding from stray light, and providing reliable, accurate attitude information to point its narrow communication beam accurately to the future location of the ground terminal. Though our transceiver will transmit in the 1550 nm waveband and receive in the 1064 nm waveband, the system design relies heavily on reflective optical elements, extending flexibility to be modified for use at different wavebands. The design makes use of common path propagation among transmit, receive and pointing verification optical channels to maintain precise alignment among its components, and to naturally correct for element misalignment resulting from launch or thermal element perturbations. This paper presents the results of trade studies showing the evolution of the design, unique operational characteristics of the design, elements that help to maintain minimal stray light contamination, and preliminary results from development and initial testing of a functional aluminum test model.

  17. Soliton coding for secured optical communication link

    CERN Document Server

    Amiri, Iraj Sadegh; Idrus, Sevia Mahdaliza

    2015-01-01

    Nonlinear behavior of light such as chaos can be observed during propagation of a laser beam inside the microring resonator (MRR) systems. This Brief highlights the design of a system of MRRs to generate a series of logic codes. An optical soliton is used to generate an entangled photon. The ultra-short soliton pulses provide the required communication signals to generate a pair of polarization entangled photons required for quantum keys. In the frequency domain, MRRs can be used to generate optical millimetre-wave solitons with a broadband frequency of 0?100 GHz. The soliton signals are multi

  18. Scalable Optical-Fiber Communication Networks

    Science.gov (United States)

    Chow, Edward T.; Peterson, John C.

    1993-01-01

    Scalable arbitrary fiber extension network (SAFEnet) is conceptual fiber-optic communication network passing digital signals among variety of computers and input/output devices at rates from 200 Mb/s to more than 100 Gb/s. Intended for use with very-high-speed computers and other data-processing and communication systems in which message-passing delays must be kept short. Inherent flexibility makes it possible to match performance of network to computers by optimizing configuration of interconnections. In addition, interconnections made redundant to provide tolerance to faults.

  19. Nonverbal communication in the focus-group

    Directory of Open Access Journals (Sweden)

    Alina Simona TECĂU

    2015-12-01

    Full Text Available In the process of analysing the information obtained through focus group qualitative marketing research, a very important source of data is represented by non-verbal communication. Although the literature reveals an abundance of published material that describes how data obtained through focus group should be analysed, one of the least addressed issue is the interpretation of signals from participants: gestures, posture, dynamic and rhythm of speech or even the silence. This Article addresses precisely aspects of non-verbal communication in the focus group's and although not intended to examine in detail the results of a focus group, it shows how some of signals transmitted by participants of such research have been analysed and interpreted.

  20. Machine learning techniques for optical communication system optimization

    DEFF Research Database (Denmark)

    Zibar, Darko; Wass, Jesper; Thrane, Jakob

    In this paper, machine learning techniques relevant to optical communication are presented and discussed. The focus is on applying machine learning tools to optical performance monitoring and performance prediction.......In this paper, machine learning techniques relevant to optical communication are presented and discussed. The focus is on applying machine learning tools to optical performance monitoring and performance prediction....

  1. NASA's current activities in free space optical communications

    Science.gov (United States)

    Edwards, Bernard L.

    2017-11-01

    NASA and other space agencies around the world are currently developing free space optical communication systems for both space-to-ground links and space-to-space links. This paper provides an overview of NASA's current activities in free space optical communications with a focus on Near Earth applications. Activities to be discussed include the Lunar Laser Communication Demonstration, the Laser Communications Relay Demonstration, and the commercialization of the underlying technology. The paper will also briefly discuss ongoing efforts and studies for Deep Space optical communications. Finally the paper will discuss the development of international optical communication standards within the Consultative Committee for Space Data Systems.

  2. Spherical transceivers for ultrafast optical wireless communications

    Science.gov (United States)

    Jin, Xian; Hristovski, Blago A.; Collier, Christopher M.; Geoffroy-Gagnon, Simon; Born, Brandon; Holzman, Jonathan F.

    2016-02-01

    Optical wireless communications (OWC) offers the potential for high-speed and mobile operation in indoor networks. Such OWC systems often employ a fixed transmitter grid and mobile transceivers, with the mobile transceivers carrying out bi-directional communication via active downlinks (ideally with high-speed signal detection) and passive uplinks (ideally with broad angular retroreflection and high-speed modulation). It can be challenging to integrate all of these bidirectional communication capabilities within the mobile transceivers, however, as there is a simultaneous desire for compact packaging. With this in mind, the work presented here introduces a new form of transceiver for bi-directional OWC systems. The transceiver incorporates radial photoconductive switches (for high-speed signal detection) and a spherical retro-modulator (for broad angular retroreflection and high-speed all-optical modulation). All-optical retromodulation are investigated by way of theoretical models and experimental testing, for spherical retro-modulators comprised of three glasses, N-BK7, N-LASF9, and S-LAH79, having differing levels of refraction and nonlinearity. It is found that the spherical retro-modulator comprised of S-LAH79, with a refractive index of n ≍ 2 and a Kerr nonlinear index of n2 ≍ (1.8 ± 0.1) × 10-15 cm2/W, yields both broad angular retroreflection (over a solid angle of 2π steradians) and ultrafast modulation (over a duration of 120 fs). Such transceivers can become important elements for all-optical implementations in future bi-directional OWC systems.

  3. Communication with diode laser: short distance line of sight communication using fiber optics

    International Nuclear Information System (INIS)

    Mirza, A.H.

    1999-01-01

    The objective of this project is to carry audio signal from transmitting station to a short distance receiving station along line of sight and also communication through fiber optics is performed, using diode laser light as carrier. In this project optical communication system, modulation techniques, basics of laser and causes of using diode laser are discussed briefly. Transmitter circuit and receiver circuit are fully described. Communication was performed using pulse width modulation technique. Optical fiber communication have many advantages over other type of conventional communication techniques. This report contains the description of optical fiber communication and compared with other communication systems. (author)

  4. Fiber optical parametric amplifiers in optical communication systems

    Science.gov (United States)

    Marhic (†), Michel E; Andrekson, Peter A; Petropoulos, Periklis; Radic, Stojan; Peucheret, Christophe; Jazayerifar, Mahmoud

    2015-01-01

    The prospects for using fiber optical parametric amplifiers (OPAs) in optical communication systems are reviewed. Phase-insensitive amplifiers (PIAs) and phase-sensitive amplifiers (PSAs) are considered. Low-penalty amplification at/or near 1 Tb/s has been achieved, for both wavelength- and time-division multiplexed formats. High-quality mid-span spectral inversion has been demonstrated at 0.64 Tb/s, avoiding electronic dispersion compensation. All-optical amplitude regeneration of amplitude-modulated signals has been performed, while PSAs have been used to demonstrate phase regeneration of phase-modulated signals. A PSA with 1.1-dB noise figure has been demonstrated, and preliminary wavelength-division multiplexing experiments have been performed with PSAs. 512 Gb/s have been transmitted over 6,000 km by periodic phase conjugation. Simulations indicate that PIAs could reach data rate x reach products in excess of 14,000 Tb/s × km in realistic wavelength-division multiplexed long-haul networks. Technical challenges remaining to be addressed in order for fiber OPAs to become useful for long-haul communication networks are discussed. PMID:25866588

  5. Optical wireless communications: Theory and applications

    Science.gov (United States)

    Aminikashani, Mohammadreza

    This dissertation focuses on optical communications having recently attracted sig- nificant attentions as a promising complementary technique for radio frequency (RF) in both short- and long-range communications. These systems offer signifi- cant technical and operational advantages such as higher capacity, virtually unlim- ited reuse, unregulated spectrum and robustness to electromagnetic interference. Optical wireless communication (OWC) can be used both indoors and outdoors. Part of the dissertation contains novel results on terrestrial free-space optical (FSO) communications. FSO communication is a line-of sight technique that uses lasers for high rate wireless communication over distances up to several kilometers. In comparison to RF counterparts, a FSO link has a very high optical bandwidth available, allowing aggregate data rates on the order of Tera bits per second (1 Tera bits per second is 1000 Giga bites per second). However, FSO suffers limitations. The major limitation of the terrestrial FSO communication systems is the atmo- spheric turbulence, which produces fluctuations in the irradiance of the transmitted optical beam, as a result of random variations in the refractive index through the link. The existence of atmospheric-induced turbulence degrades the performance of FSO links particularly with a transmission distance longer than 1 kilometer. The identification of a tractable probability density function (pdf) to describe at- mospheric turbulence under all irradiance fluctuation regimes is crucial in order to study the reliability of a terrestrial FSO system. This dissertation addresses this daunting problem and proposes a novel statistical model that accurately de- scribes turbulence-induced fading under all irradiance conditions and unifies most of the proposed statistical models derived until now in the literature. The proposed model is important for the research community working on FSO communications because it allows them to fully capitalize

  6. Acquisition and tracking for underwater optical communications

    Science.gov (United States)

    Williams, Andrew J.; Laycock, Leslie L.; Griffith, Michael S.; McCarthy, Andrew G.; Rowe, Duncan P.

    2017-10-01

    There is a growing requirement to transfer large volumes of data between underwater platforms. As seawater is transmissive in the visible band, underwater optical communications is an active area of interest since it offers the potential for power efficient, covert and high bandwidth datalinks at short to medium ranges. Short range systems have been successfully demonstrated using sources with low directionality. To realise higher data rates and/or longer ranges, the use of more efficient directional beams is required; by necessity, these must be sufficiently aligned to achieve the required link margin. For mobile platforms, the acquisition and tracking of each node is therefore critical in order to establish and maintain an optical datalink. This paper describes work undertaken to demonstrate acquisition and tracking in a 3D underwater environment. A range of optical sources, beam steering technologies, and tracking sensors have been assessed for suitability. A novel scanning strategy exploiting variable beam divergence was developed to provide robust acquisition whilst minimising acquisition time. A prototype system was assembled and demonstrated in a large water tank. This utilised custom quadrant detectors based on Silicon PhotoMultiplier (SiPM) arrays for fine tracking, and a Wide Field of View (WFoV) sCMOS camera for link acquisition. Fluidic lenses provided dynamic control of beam divergence, and AC modulation/filtering enabled background rejection. The system successfully demonstrated robust optical acquisition and tracking between two nodes with only nanowatt received optical powers. The acquisition time was shown to be dependent on the initial conditions and the transmitted optical power.

  7. Optical communication beyond orbital angular momentum

    CSIR Research Space (South Africa)

    Trichili, A

    2016-06-01

    Full Text Available :27674 | DOI: 10.1038/srep27674 www.nature.com/scientificreports Optical communication beyond orbital angular momentum Abderrahmen Trichili1, Carmelo Rosales-Guzmán2, Angela Dudley2,3, Bienvenu Ndagano2, Amine Ben Salem1, Mourad Zghal1,4 & Andrew Forbes2 Mode....rosalesguzman@wits.ac.za) received: 29 March 2016 Accepted: 24 May 2016 Published: 10 June 2016 OPEN www.nature.com/scientificreports/ 2Scientific RepoRts | 6:27674 | DOI: 10.1038/srep27674 Results Consider a LG mode in cylindrical coordinates, at its waist plane (z = 0), described...

  8. An Experimental Comparison of Remote Procedure Call and Group Communication

    NARCIS (Netherlands)

    Kaashoek, M.F.; Tanenbaum, A.S.; Verstoep, C.

    1992-01-01

    This paper suggests that a distributed system should support two communication paradigms: Remote Procedure Call (RPC) and group communication. The former is used for point-to-point communication; the latter is used for one-to-many communication. We demonstrate that group communication is an

  9. Free Space Optical Communication in the Military Environment

    Science.gov (United States)

    2014-09-01

    Charles River [6]. Even much earlier than Paul Revere’s ride, optical communication had developed into the semaphore or optical telegraph. The...forms of basic optical communication that are still commonplace today include semaphore flags and signal lamps utilized by navies around the world

  10. Optimal optical communication terminal structure for maximizing the link budget

    Science.gov (United States)

    Huang, Jian; Jiang, Dagang; Deng, Ke; Zhang, Peng

    2015-02-01

    Ordinary inter-satellite optical includes at least three optical paths for acquisition, tracking and communication, the three optical paths work simultaneously and share the received power. An optimal structure of inter-satellite optical communication terminal with single working optical path at each of working stages of acquisition and communication is introduced. A space optical switch based on frustrated total internal reflection effect is applied to switch the received laser power between the acquisition sensor and the communication sensor between the stages of acquisition and communication, this is named as power fusion which means power is transferred for shutting down unused optical path. For the stages of tracking and communication, a multiple cells sensor is used to accomplish the operation of tracking while communication, this is named as function fusion which means accomplishing multiple functions by one device to reduce the redundant optical paths. For optical communication terminal with single working path structure, the total received laser power would be detected by one sensor for each different stages of acquisition, tracking and communication, the link budget would be maximized, and this design would help to enlarge the system tolerance and reduce the acquisition time.

  11. Exotic Optical Beam Classes for Free-Space Communication

    Science.gov (United States)

    2016-03-24

    wandering of an optical vortex is one of the significant problems with the application of vortex beams to FSO applications. From a geometrical optics ...AFRL-AFOSR-VA-TR-2016-0131 Exotic optical beam classes for free-space communication Greg Gbur UNIVERSITY OF NOTH CAROLINA AT CHARLOTTE Final Report...12-2015 4. TITLE AND SUBTITLE Exotic optical beam classes for free-space communication 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-13-1-0009 5c

  12. Commercialization and Standardization Progress Towards an Optical Communications Earth Relay

    Science.gov (United States)

    Edwards, Bernard L.; Israel, David J.

    2015-01-01

    NASA is planning to launch the next generation of a space based Earth relay in 2025 to join the current Space Network, consisting of Tracking and Data Relay Satellites in space and the corresponding infrastructure on Earth. While the requirements and architecture for that relay satellite are unknown at this time, NASA is investing in communications technologies that could be deployed to provide new communications services. One of those new technologies is optical communications. The Laser Communications Relay Demonstration (LCRD) project, scheduled for launch in 2018 as a hosted payload on a commercial communications satellite, is a critical pathfinder towards NASA providing optical communications services on the next generation space based relay. This paper will describe NASA efforts in the on-going commercialization of optical communications and the development of inter-operability standards. Both are seen as critical to making optical communications a reality on future NASA science and exploration missions. Commercialization is important because NASA would like to eventually be able to simply purchase an entire optical communications terminal from a commercial provider. Inter-operability standards are needed to ensure that optical communications terminals developed by one vendor are compatible with the terminals of another. International standards in optical communications would also allow the space missions of one nation to use the infrastructure of another.

  13. The formation of group norms in computer-mediated communication

    NARCIS (Netherlands)

    Postmes, T; Spears, R; Lea, M

    The formation of group norms in computer-mediated communication (CMC) was examined among students who used e-mail as part of a course. A network analysis of group structures revealed that (a) content and form of communication is normative, group norms defining communication patterns within groups,

  14. Raman amplification in optical communication systems

    DEFF Research Database (Denmark)

    Kjær, Rasmus

    2008-01-01

    Fiber Raman amplifiers are investigated with the purpose of identifying new applications and limitations for their use in optical communication systems. Three main topics are investigated, namely: New applications of dispersion compensating Raman amplifiers, the use Raman amplification to increase...... fiberbaserede Raman-forstærkere med henblik på at identificere både deres begrænsninger og nye anvendelsesmuligheder i optiske kommunikationssystemer. En numerisk forstærkermodel er blevet udviklet for bedre at forstå forstærkerens dynamik, dens gain- og støjbegrænsninger. Modellen bruges til at forudsige...... forstærkerens statiske og dynamiske egenskaber, og det eftervises at dens resultater er i god overensstemmelse med eksperimentelle forstærkermålinger. Dispersions-kompenserende fiber er på grund af sin store udbredelse og fiberens høje Raman gain effektivitet et meget velegnet Raman gain-medium. Tre nye...

  15. Nonclassical lightstates in optical communication schemes

    International Nuclear Information System (INIS)

    Mattle, K. U.

    1997-11-01

    The present thesis is a result in theoretical and experimental work on quant information and quant communication. The first part describes a new high intense source for polarization entangled photon pairs. The high quality of the source is clearly demonstrated by violating a Bell-inequality in less than 5 minutes with 100 standard deviations. This new source is a genius tool for new experiments in the field of fundamental physics as well as applied physics. The next chapter shows an experimental implementation of an optical dense quantum coding scheme. The combination of Bell-state generation and analysis of this entangled states leads to a new nonclassical communication scheme, where the channel capacity is enhanced. A single two state photon can be used for coding and decoding 1.58 bit instead of 1 bit for classical two state systems. The following chapter discusses two photon interference effects for two independent light sources. In an experiment two independent fluorescence pulses show this kind of interference effects. The fifth chapter describes 3-photon interference effects. This nonclassical interference effect is the elementary process for the quantum teleportation scheme. In this scheme an unknown particle state is transmitted from A to B without sending the particle itself. (author)

  16. Optical fiber communication — An overview

    Indian Academy of Sciences (India)

    This paper deals with the historical development of optical communication systems and their failures initially. Then the different generations in optical fiber communication along with their features are discussed. Some aspects of total internal reflection, different types of fibers along with their size and refractive index profile, ...

  17. Creating Feedback Channels With Optical Communications For Information Operations (IO)

    Science.gov (United States)

    2016-06-01

    amphibious operations. Optical communications technologies, direct marketing principles , and current IO shortfalls are explored to determine whether...technology. First, these concepts are applied to show covert amphibious operations. Optical communications technologies, direct marketing principles , and...power, as per Appendix A. A major portion of the marketing campaign comes in the form of advertising. The correlating principles of advertising in

  18. Monolithically integrated quantum dot optical modulator with Semiconductor optical amplifier for short-range optical communications

    Science.gov (United States)

    Yamamoto, Naokatsu; Akahane, Kouichi; Umezawa, Toshimasa; Kawanishi, Tetsuya

    2015-04-01

    A monolithically integrated quantum dot (QD) optical gain modulator (OGM) with a QD semiconductor optical amplifier (SOA) was successfully developed. Broadband QD optical gain material was used to achieve Gbps-order high-speed optical data transmission, and an optical gain change as high as approximately 6-7 dB was obtained with a low OGM voltage of 2.0 V. Loss of optical power due to insertion of the device was also effectively compensated for by the SOA section. Furthermore, it was confirmed that the QD-OGM/SOA device helped achieve 6.0-Gbps error-free optical data transmission over a 2.0-km-long photonic crystal fiber. We also successfully demonstrated generation of Gbps-order, high-speed, and error-free optical signals in the >5.5-THz broadband optical frequency bandwidth larger than the C-band. These results suggest that the developed monolithically integrated QD-OGM/SOA device will be an advantageous and compact means of increasing the usable optical frequency channels for short-reach communications.

  19. Nonlinear Fourier transform for dual-polarization optical communication system

    OpenAIRE

    Gaiarin, Simone

    2018-01-01

    New services and applications are causing an exponential increase in the internet traffic. In a few years, the current fiber-optic communication system infrastructure will not be able to meet this demand because fiber nonlinearity dramatically limits the information transmission rate. Eigenvalue communication is considered an emerging paradigm in fiber-optic communications that could potentially overcome these limitations. It relies on a mathematical technique called “inverse scattering trans...

  20. Systems and methods for free space optical communication

    Science.gov (United States)

    Harper, Warren W [Benton City, WA; Aker, Pamela M [Richland, WA; Pratt, Richard M [Richland, WA

    2011-05-10

    Free space optical communication methods and systems, according to various aspects are described. The methods and systems are characterized by transmission of data through free space with a digitized optical signal acquired using wavelength modulation, and by discrimination between bit states in the digitized optical signal using a spectroscopic absorption feature of a chemical substance.

  1. Privacy enhanced group communication in clinical environment

    Science.gov (United States)

    Li, Mingyan; Narayanan, Sreeram; Poovendran, Radha

    2005-04-01

    Privacy protection of medical records has always been an important issue and is mandated by the recent Health Insurance Portability and Accountability Act (HIPAA) standards. In this paper, we propose security architectures for a tele-referring system that allows electronic group communication among professionals for better quality treatments, while protecting patient privacy against unauthorized access. Although DICOM defines the much-needed guidelines for confidentiality of medical data during transmission, there is no provision in the existing medical security systems to guarantee patient privacy once the data has been received. In our design, we address this issue by enabling tracing back to the recipient whose received data is disclosed to outsiders, using watermarking technique. We present security architecture design of a tele-referring system using a distributed approach and a centralized web-based approach. The resulting tele-referring system (i) provides confidentiality during the transmission and ensures integrity and authenticity of the received data, (ii) allows tracing of the recipient who has either distributed the data to outsiders or whose system has been compromised, (iii) provides proof of receipt or origin, and (iv) can be easy to use and low-cost to employ in clinical environment.

  2. 77 FR 65713 - Certain Optoelectronic Devices for Fiber Optic Communications, Components Thereof, and Products...

    Science.gov (United States)

    2012-10-30

    ... Fiber Optic Communications, Components Thereof, and Products Containing the Same; Notice of Institution... certain optoelectronic devices for fiber optic communications, components thereof, and products containing... optoelectronic devices for fiber optic communications, components thereof, and products containing the same that...

  3. Beaconless Pointing for Deep-Space Optical Communication

    Science.gov (United States)

    Swank, Aaron J.; Aretskin-Hariton, Eliot; Le, Dzu K.; Sands, Obed S.; Wroblewski, Adam

    2016-01-01

    Free space optical communication is of interest to NASA as a complement to existing radio frequency communication methods. The potential for an increase in science data return capability over current radio-frequency communications is the primary objective. Deep space optical communication requires laser beam pointing accuracy on the order of a few microradians. The laser beam pointing approach discussed here operates without the aid of a terrestrial uplink beacon. Precision pointing is obtained from an on-board star tracker in combination with inertial rate sensors and an outgoing beam reference vector. The beaconless optical pointing system presented in this work is the current approach for the Integrated Radio and Optical Communication (iROC) project.

  4. The Impact of a Group Communication Course on Veterinary Medical Students' Perceptions of Communication Competence and Communication Apprehension.

    Science.gov (United States)

    Kedrowicz, April A

    2016-01-01

    This paper explores the impact of a group communication course on veterinary medical students' perceptions of communication competence and communication anxiety. Students enrolled in the Group Communication in Veterinary Medicine course completed the Personal Report of Communication Apprehension and the Communicative Competence Scale at the beginning (Time 1) and end (Time 2) of the semester. Results show that first-year veterinary students' self-perceptions of communication competence increased and their self-reported levels of communication apprehension decreased across multiple contexts from Time 1 to Time 2. This research provides support for experiential communication training fostering skill development and confidence.

  5. Causal Relationships between Communication Confidence, Beliefs about Group Work, and Willingness to Communicate in Foreign Language Group Work

    Science.gov (United States)

    Fushino, Kumiko

    2010-01-01

    This article reports on the causal relationships between three factors in second language (L2) group work settings: communication confidence (i.e., confidence in one's ability to communicate), beliefs about group work, and willingness to communicate (WTC). A questionnaire was administered to 729 first-year university students in Japan. A model…

  6. OPALS: A COTS-based Tech Demo of Optical Communications

    Science.gov (United States)

    Oaida, Bogdan

    2012-01-01

    I. Objective: Deliver video from ISS to optical ground terminal via an optical communications link. a) JPL Phaeton/Early Career Hire (ECH) training project. b) Implemented as Class-D payload. c) Downlink at approx.30Mb/s. II. Flight System a) Optical Head Beacon Acquisition Camera. Downlink Transmitter. 2-axis Gimbal. b) Sealed Container Laser Avionics Power distribution Digital I/O board III. Implementation: a) Ground Station - Optical Communications Telescope Laboratory at Table Mountain Facility b) Flight System mounted to ISS FRAM as standard I/F. Attached externally on Express Logistics Carrier.

  7. Optical Techniques for Millimeter-Wave Phased Array Communications Antennas

    National Research Council Canada - National Science Library

    Edge, Colin

    1998-01-01

    The scope of this program was to study the application of optical techniques to signal distribution and beamforming networks in phased array antennas for Army mobile tactical communications systems...

  8. Mode-Locked Semiconductor Lasers for Optical Communication Systems

    DEFF Research Database (Denmark)

    Yvind, Kresten; Larsson, David; Oxenløwe, Leif Katsuo

    2005-01-01

    We present investigations on 10 and 40 GHz monolithic mode-locked lasers for applications in optical communications systems. New all-active lasers with one to three quantum wells have been designed, fabricated and characterized....

  9. Devices and Control Strategies for AD HOC Optical Communications Networks

    National Research Council Canada - National Science Library

    Baillieul, John; Bifano, Thomas G

    2006-01-01

    ... (both hardware and operational concepts) that we plan to develop in initiating an ambitious program of research to develop a radical new technology for high-bandwidth, stealthy communication over free-space optical links...

  10. High Data Rate Optical Wireless Communications Based on Ultraviolet Band

    KAUST Repository

    Sun, Xiaobin

    2017-01-01

    Optical wireless communication systems based on ultraviolet (UV)-band has a lot inherent advantages, such as low background solar radiation, low device dark noise. Besides, it also has small restrictive requirements for PAT (pointing, acquisition

  11. Vibration Isolation Platform for Long Range Optical Communications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Optical communication links provide higher data transfer rates with lower mass, power, and volume than conventional radio-frequency links. For deep space...

  12. Demographic diversity, communication and learning behaviour in healthcare groups

    NARCIS (Netherlands)

    Curseu, P.L.

    2013-01-01

    An integrative model of group learning was tested in a sample of 40 healthcare groups (434 respondents), and the results show that age diversity reduces the frequency of face-to-face communication whereas educational diversity reduces the frequency of virtual communication in healthcare groups.

  13. All-optical signal processing data communication and storage applications

    CERN Document Server

    Eggleton, Benjamin

    2015-01-01

    This book provides a comprehensive review of the state-of-the art of optical signal processing technologies and devices. It presents breakthrough solutions for enabling a pervasive use of optics in data communication and signal storage applications. It presents presents optical signal processing as solution to overcome the capacity crunch in communication networks. The book content ranges from the development of innovative materials and devices, such as graphene and slow light structures, to the use of nonlinear optics for secure quantum information processing and overcoming the classical Shannon limit on channel capacity and microwave signal processing. Although it holds the promise for a substantial speed improvement, today’s communication infrastructure optics remains largely confined to the signal transport layer, as it lags behind electronics as far as signal processing is concerned. This situation will change in the near future as the tremendous growth of data traffic requires energy efficient and ful...

  14. Application of Beyond Bound Decoding for High Speed Optical Communications

    DEFF Research Database (Denmark)

    Li, Bomin; Larsen, Knud J.; Vegas Olmos, Juan José

    2013-01-01

    This paper studies the application of beyond bound decoding method for high speed optical communications. This hard-decision decoding method outperforms traditional minimum distance decoding method, with a total net coding gain of 10.36 dB.......This paper studies the application of beyond bound decoding method for high speed optical communications. This hard-decision decoding method outperforms traditional minimum distance decoding method, with a total net coding gain of 10.36 dB....

  15. Machine learning concepts in coherent optical communication systems

    DEFF Research Database (Denmark)

    Zibar, Darko; Schäffer, Christian G.

    2014-01-01

    Powerful statistical signal processing methods, used by the machine learning community, are addressed and linked to current problems in coherent optical communication. Bayesian filtering methods are presented and applied for nonlinear dynamic state tracking. © 2014 OSA.......Powerful statistical signal processing methods, used by the machine learning community, are addressed and linked to current problems in coherent optical communication. Bayesian filtering methods are presented and applied for nonlinear dynamic state tracking. © 2014 OSA....

  16. Applications of expectation maximization algorithm for coherent optical communication

    DEFF Research Database (Denmark)

    Carvalho, L.; Oliveira, J.; Zibar, Darko

    2014-01-01

    In this invited paper, we present powerful statistical signal processing methods, used by machine learning community, and link them to current problems in optical communication. In particular, we will look into iterative maximum likelihood parameter estimation based on expectation maximization...... algorithm and its application in coherent optical communication systems for linear and nonlinear impairment mitigation. Furthermore, the estimated parameters are used to build the probabilistic model of the system for the synthetic impairment generation....

  17. Silicon-based optical integrated circuits for terabit communication networks

    International Nuclear Information System (INIS)

    Svidzinsky, K K

    2003-01-01

    A brief review is presented of the development of silicon-based optical integrated circuits used as components in modern all-optical communication networks with the terabit-per-second transmission capacity. The designs and technologies for manufacturing these circuits are described and the problems related to their development and application in WDM communication systems are considered. (special issue devoted to the memory of academician a m prokhorov)

  18. Demographic diversity, communication and learning behaviour in healthcare groups.

    Science.gov (United States)

    Curşeu, Petru Lucian

    2013-01-01

    An integrative model of group learning was tested in a sample of 40 healthcare groups (434 respondents), and the results show that age diversity reduces the frequency of face-to-face communication whereas educational diversity reduces the frequency of virtual communication in healthcare groups. Frequency of communication (both face-to-face and virtual), in turn, positively impacts on the emergence of trust and psychological safety, which are essential drivers of learning behaviours in healthcare groups. Additional results show that average educational achievement within groups is conducive for communication frequency (both face-to-face and virtual), whereas mean age within groups has a negative association with the use of virtual communication in healthcare groups. Copyright © 2012 John Wiley & Sons, Ltd.

  19. Secure Group Communications for Large Dynamic Multicast Group

    Institute of Scientific and Technical Information of China (English)

    Liu Jing; Zhou Mingtian

    2003-01-01

    As the major problem in multicast security, the group key management has been the focus of research But few results are satisfactory. In this paper, the problems of group key management and access control for large dynamic multicast group have been researched and a solution based on SubGroup Secure Controllers (SGSCs) is presented, which solves many problems in IOLUS system and WGL scheme.

  20. Enhancing Optical Communications with Brand New Fibers

    DEFF Research Database (Denmark)

    Morioka, Toshio; Awaji, Yoshinari; Ryf, Roland

    2012-01-01

    Optical fibers have often been considered to offer effectively infinite capacity to support the rapid traffic growth essential to our information society. However, as demand has grown and technology has developed, we have begun to realize that there is a fundamental limit to fiber capacity of ~ 100...... Tb/s per fiber for systems based on conventional single-core single-mode optical fiber as the transmission medium. This limit arises from the interplay of a number of factors including the Shannon limit, optical fiber nonlinearities, the fiber fuse effect, as well as optical amplifier bandwidth...... new fibers for space-division multiplexing and mode-division multiplexing....

  1. European IST-programme roadmap for Optical Communications

    DEFF Research Database (Denmark)

    Ackaert, Ann; Demeester, Piet; Lagasse, Paul

    2003-01-01

    On the basis of European IST project results in the field of photonics, the OPTIMIST thematic network has produced a roadmap for optical communications. This work is described in the present article which provides scenarios for the evolution of the optical network in the coming 10 years. Predicta...

  2. Power Budget Analysis of Fiber Optics Communication Links Along ...

    African Journals Online (AJOL)

    With the development of optical fiber communication system most telecommunication companies now prefer to use optical fiber transmission medium for higher information bandwidth. The design of such a system involves many aspects such as the type of source to be used, the kind of fiber to be employed and detector.

  3. Two mode optical fiber in space optics communication

    Science.gov (United States)

    Hampl, Martin

    2017-11-01

    In our contribution we propose to use of a two-mode optical fiber as a primary source in a transmitting optical head instead of the laser diode. The distribution of the optical intensity and the complex degree of the coherence on the output aperture of the lens that is irradiated by a step-index weakly guiding optical fiber is investigated. In our treatment we take into account weakly guided modes with polarization corrections to the propagation constant and unified theory of second order coherence and polarization of electromagnetic beams.

  4. Interactive educational technologies as a method of communicative competency development of optical and fiber optic communication systems specialists

    Science.gov (United States)

    Matveeva, Tatiana U.; Osadchiy, Igor S.; Husnutdinova, Marina N.

    2017-04-01

    The article examines the process of formation of communicative competencies of optic and fiber optic communication systems specialists; the role of communicative competencies is examined in the structure of professionally important skills, together with the contents of professional activity. The stages of empirical research into formation of communicative competencies have been presented, and the values of statistical reliability of data have been provided. The model of formation of communicative competency using interactive technology has been developed based on the research done, and main stages of model implementation and motives of formation of communicative competency have been highlighted. A scheme of "Communicative competence as a base of future success" training session has been suggested as one of the basic interactive technologies. Main components of education that are used during the stages of the training cycle have been examined. The statistical data on the effectiveness of use of interactive educational technologies has been presented; it allowed development of communicative competency of specialists in the field of optical and fiber optic communication system.

  5. Soliton-based ultra-high speed optical communications

    Indian Academy of Sciences (India)

    All these facts are the outcome of research on optical solitons in fibers in spite of the fact that the commonly used RZ format is not always called a soliton format. The overview presented here attempts to incorporate the role of soliton-based communications research in present day ultra-high speed communications.

  6. Semiconductor Mode-Locked Lasers for Optical Communication Systems

    DEFF Research Database (Denmark)

    Yvind, Kresten

    2003-01-01

    The thesis deals with the design and fabrication of semiconductor mode-locked lasers for use in optical communication systems. The properties of pulse sources and characterization methods are described as well as requirements for application in communication systems. Especially, the importance of...

  7. Nonlinear Fourier transform for dual-polarization optical communication system

    DEFF Research Database (Denmark)

    Gaiarin, Simone

    communication is considered an emerging paradigm in fiber-optic communications that could potentially overcome these limitations. It relies on a mathematical technique called “inverse scattering transform” or “nonlinear Fourier transform (NFT)” to exploit the “hidden” linearity of the nonlinear Schrödinger...

  8. Indoor optical wireless communication system using beam-steering by cascaded diffractive optical elements

    NARCIS (Netherlands)

    Oh, C.W.; Tangdiongga, E.; Koonen, A.M.J.; García-Blanco, S.M.; Boller, Kl.J.; Sefunc, M.A.; Geuzebroek, D.

    2014-01-01

    While the radio spectrum continues to struggle with a soaring bandwidth demand, the optical spectrum promises virtually unlimited license-free bandwidth. We report the feasibility of high-capacity point-to-point links for indoor optical wireless communication with cascaded diffractive optical

  9. Novel 2D-sequential color code system employing Image Sensor Communications for Optical Wireless Communications

    Directory of Open Access Journals (Sweden)

    Trang Nguyen

    2016-06-01

    Full Text Available The IEEE 802.15.7r1 Optical Wireless Communications Task Group (TG7r1, also known as the revision of the IEEE 802.15.7 Visible Light Communication standard targeting the commercial usage of visible light communication systems, is of interest in this paper. The paper is mainly concerned with Image Sensor Communications (ISC of TG7r1; however, the major challenge facing ISC, as addressed in the Technical Consideration Document (TCD of TG7r1, is Image Sensor Compatibility among the variety of different commercial cameras on the market. One of the most challenging but interesting compatibility requirements is the need to support the verified presence of frame rate variation. This paper proposes a novel design for 2D-sequential color code. Compared to a QR-code-based sequential transmission, the proposed design of 2D-sequential code can overcome the above challenge that it is compatible with different frame rate variations and different shutter operations, and has the ability to mitigate the rolling effect as well as the rotating effect while effectively minimizing transmission overhead. Practical implementations are demonstrated and a performance comparison is presented.

  10. Polarization tracking system for free-space optical communication, including quantum communication

    Science.gov (United States)

    Nordholt, Jane Elizabeth; Newell, Raymond Thorson; Peterson, Charles Glen; Hughes, Richard John

    2018-01-09

    Quantum communication transmitters include beacon lasers that transmit a beacon optical signal in a predetermined state of polarization such as one of the states of polarization of a quantum communication basis. Changes in the beacon polarization are detected at a receiver, and a retarder is adjusted so that the states of polarization in a received quantum communication optical signal are matched to basis polarizations. The beacon and QC signals can be at different wavelengths so that the beacon does not interfere with detection and decoding of the QC optical signal.

  11. Quantum communication network utilizing quadripartite entangled states of optical field

    International Nuclear Information System (INIS)

    Shen Heng; Su Xiaolong; Jia Xiaojun; Xie Changde

    2009-01-01

    We propose two types of quantum dense coding communication networks with optical continuous variables, in which a quadripartite entangled state of the optical field with totally three-party correlations of quadrature amplitudes is utilized. In the networks, the exchange of information between any two participants can be manipulated by one or two of the remaining participants. The channel capacities for a variety of communication protocols are numerically calculated. Due to the fact that the quadripartite entangled states applied in the communication systems have been successfully prepared already in the laboratory, the proposed schemes are experimentally accessible at present.

  12. mCell: Facilitating Mobile Communication of Small Groups

    OpenAIRE

    Mikko T. Tarkiainen; Jonna Häkkilä; Jan Blom; Merja Haveri; Jyri Virtanen

    2008-01-01

    Mobile communication technology offers a potential platform for new types of communication applications. Here, we describe the development and experiences with a mobile group communication application, mCell, that runs on a mobile phone. We present the underlying design implications, the application implementation, and a user study, where three groups used the application for one month. The findings of the user study reveal general user experiences with the application and show different patt...

  13. Short Communications Strength Properties and Groups of Major ...

    African Journals Online (AJOL)

    Short Communications Strength Properties and Groups of Major Commercial Timbers Grown in Kenya. ... The strength groups developed revealed that most species in Kenya are suitable for heavy engineering works and building construction. ... strength properties, commercial timber, physical and mechanical properties

  14. Teaching Small Group Communication: The Do Good Project

    Science.gov (United States)

    Minei, Elizabeth M.

    2016-01-01

    This paper focuses on the parameters of a semester-long project called the "Do Good" project, geared towards developing small group communication skills in undergraduate students. This project highlights participation in a social engagement project that allows students to bridge concepts learned in small group communication lectures…

  15. Security Analysis of Accountable Anonymous Group Communication in Dissent

    Science.gov (United States)

    2013-01-31

    instance, group discussion forums or instant messaging. Misbehaving users may abuse this anonymity to disrupt communication, however, and existing...Abstract Users often wish to communicate anonymously on the Internet using, for instance, group discussion forums or instant messaging. Misbehaving users may...personal reprisal (Stein 2003). Yet anonymity makes it difficult to trace or exclude misbehaving participants (Davenport 2002). Online proto- cols

  16. Iterative Decoding for an Optical CDMA based Laser communication System

    International Nuclear Information System (INIS)

    Kim, Jin Young; Kim, Eun Cheol; Cha, Jae Sang

    2008-01-01

    An optical CDMA(code division multiple access)based Laser communication system has attracted much attention since it requires minimal optical Laser signal processing and it is virtually delay free, while from the theoretical point of view, its performance depends on the auto and cross correlation properties of employed sequences. Various kinds of channel coding schemes for optical CDMA based Laser communication systems have been proposed and analyzed to compensate nonideal channel and receiver conditions in impaired photon channels. In this paper, we propose and analyze an iterative decoding of optical CDMA based Laser communication signals for both shot noise limited and thermal noise limited systems. It is assumed that optical channel is an intensity modulated (IM)channel and direct detection scheme is employed to detect the received optical signal. The performance is evaluated in terms of bit error probability and throughput. It is demonstrated that the BER and throughput performance is substantially improved with interleaver length for a fixed code rate and with alphabet size of PPM (pulse position modulation). Also, the BER and throughput performance is significantly enhanced with the number of iterations for decoding process. The results in this paper can be applied to the optical CDMA based Laser communication network with multiple access applications

  17. Iterative Decoding for an Optical CDMA based Laser communication System

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Young; Kim, Eun Cheol [Kwangwoon Univ., Seoul (Korea, Republic of); Cha, Jae Sang [Seoul National Univ. of Technology, Seoul (Korea, Republic of)

    2008-11-15

    An optical CDMA(code division multiple access)based Laser communication system has attracted much attention since it requires minimal optical Laser signal processing and it is virtually delay free, while from the theoretical point of view, its performance depends on the auto and cross correlation properties of employed sequences. Various kinds of channel coding schemes for optical CDMA based Laser communication systems have been proposed and analyzed to compensate nonideal channel and receiver conditions in impaired photon channels. In this paper, we propose and analyze an iterative decoding of optical CDMA based Laser communication signals for both shot noise limited and thermal noise limited systems. It is assumed that optical channel is an intensity modulated (IM)channel and direct detection scheme is employed to detect the received optical signal. The performance is evaluated in terms of bit error probability and throughput. It is demonstrated that the BER and throughput performance is substantially improved with interleaver length for a fixed code rate and with alphabet size of PPM (pulse position modulation). Also, the BER and throughput performance is significantly enhanced with the number of iterations for decoding process. The results in this paper can be applied to the optical CDMA based Laser communication network with multiple access applications.

  18. All-Optical Regeneration System for Optical Wavelength Division Multiplexed Communication Systems

    DEFF Research Database (Denmark)

    2014-01-01

    The invention relates to an all-optical regeneration system for regeneration of optical wavelength division multiplexed WDM data signals in an optical WDM communication system. The system comprises a WDM-to-Optical time domain multiplexing OTDM, WDM-to-OTDM, converter, capable of converting....... The system additionally comprises an OTDM-to-WDM converter for converting the output OTDM data signal to an output WDM data signal. An input of the all-optical regenerator unit is in optical communication with an output of the WDM-to-OTDM converter, and an output of the all-optical regenerator unit...... an input WDM data signal comprising multiple wavelength channels into an input OTDM data signal comprising multiple time multiplexed time channels. The system further comprises an all-optical regenerator unit being configured for regenerating the input OTDM data signal into an output OTDM data signal...

  19. Digital optical processing of optical communications: towards an Optical Turing Machine

    Science.gov (United States)

    Touch, Joe; Cao, Yinwen; Ziyadi, Morteza; Almaiman, Ahmed; Mohajerin-Ariaei, Amirhossein; Willner, Alan E.

    2017-01-01

    Optical computing is needed to support Tb/s in-network processing in a way that unifies communication and computation using a single data representation that supports in-transit network packet processing, security, and big data filtering. Support for optical computation of this sort requires leveraging the native properties of optical wave mixing to enable computation and switching for programmability. As a consequence, data must be encoded digitally as phase (M-PSK), semantics-preserving regeneration is the key to high-order computation, and data processing at Tb/s rates requires mixing. Experiments have demonstrated viable approaches to phase squeezing and power restoration. This work led our team to develop the first serial, optical Internet hop-count decrement, and to design and simulate optical circuits for calculating the Internet checksum and multiplexing Internet packets. The current exploration focuses on limited-lookback computational models to reduce the need for permanent storage and hybrid nanophotonic circuits that combine phase-aligned comb sources, non-linear mixing, and switching on the same substrate to avoid the macroscopic effects that hamper benchtop prototypes.

  20. Digital optical processing of optical communications: towards an Optical Turing Machine

    Directory of Open Access Journals (Sweden)

    Touch Joe

    2017-01-01

    Full Text Available Optical computing is needed to support Tb/s in-network processing in a way that unifies communication and computation using a single data representation that supports in-transit network packet processing, security, and big data filtering. Support for optical computation of this sort requires leveraging the native properties of optical wave mixing to enable computation and switching for programmability. As a consequence, data must be encoded digitally as phase (M-PSK, semantics-preserving regeneration is the key to high-order computation, and data processing at Tb/s rates requires mixing. Experiments have demonstrated viable approaches to phase squeezing and power restoration. This work led our team to develop the first serial, optical Internet hop-count decrement, and to design and simulate optical circuits for calculating the Internet checksum and multiplexing Internet packets. The current exploration focuses on limited-lookback computational models to reduce the need for permanent storage and hybrid nanophotonic circuits that combine phase-aligned comb sources, non-linear mixing, and switching on the same substrate to avoid the macroscopic effects that hamper benchtop prototypes.

  1. Hybrid electronic/optical synchronized chaos communication system.

    Science.gov (United States)

    Toomey, J P; Kane, D M; Davidović, A; Huntington, E H

    2009-04-27

    A hybrid electronic/optical system for synchronizing a chaotic receiver to a chaotic transmitter has been demonstrated. The chaotic signal is generated electronically and injected, in addition to a constant bias current, to a semiconductor laser to produce an optical carrier for transmission. The optical chaotic carrier is photodetected to regenerate an electronic signal for synchronization in a matched electronic receiver The system has been successfully used for the transmission and recovery of a chaos masked message that is added to the chaotic optical carrier. Past demonstrations of synchronized chaos based, secure communication systems have used either an electronic chaotic carrier or an optical chaotic carrier (such as the chaotic output of various nonlinear laser systems). This is the first electronic/optical hybrid system to be demonstrated. We call this generation of a chaotic optical carrier by electronic injection.

  2. Spectrum Scarcity and Free Space Optical Communications

    KAUST Repository

    Alouini, Mohamed-Slim

    2014-01-01

    Exact and asymptotic studies of the average error probability of wireless communication systems over generalized fading channels have been extensively pursued over the last two decades. In contrast, studies and results dealing with the channel

  3. Development of the Free-space Optical Communications Analysis Software (FOCAS)

    Science.gov (United States)

    Jeganathan, M.; Mecherle, G.; Lesh, J.

    1998-01-01

    The Free-space Optical Communications Analysis Software (FOCAS) was developed at the Jet Propulsion Laboratory (JPL) to provide mission planners, systems engineers and communications engineers with an easy to use tool to analyze optical communications link.

  4. Initial Characterization of Optical Communications with Disruption-Tolerant Network Protocols

    Science.gov (United States)

    Schoolcraft, Joshua; Wilson, Keith

    2011-01-01

    Disruption-tolerant networks (DTNs) are groups of network assets connected with a suite of communication protocol technologies designed to mitigate the effects of link delay and disruption. Application of DTN protocols to diverse groups of network resources in multiple sub-networks results in an overlay network-of-networks with autonomous data routing capability. In space environments where delay or disruption is expected, performance of this type of architecture (such as an interplanetary internet) can increase with the inclusion of new communications mediums and techniques. Space-based optical communication links are therefore an excellent building block of space DTN architectures. When compared to traditional radio frequency (RF) communications, optical systems can provide extremely power-efficient and high bandwidth links bridging sub-networks. Because optical links are more susceptible to link disruption and experience the same light-speed delays as RF, optical-enabled DTN architectures can lessen potential drawbacks and maintain the benefits of autonomous optical communications over deep space distances. These environment-driven expectations - link delay and interruption, along with asymmetric data rates - are the purpose of the proof-of-concept experiment outlined herein. In recognizing the potential of these two technologies, we report an initial experiment and characterization of the performance of a DTN-enabled space optical link. The experiment design employs a point-to-point free-space optical link configured to have asymmetric bandwidth. This link connects two networked systems running a DTN protocol implementation designed and written at JPL for use on spacecraft, and further configured for higher bandwidth performance. Comparing baseline data transmission metrics with and without periodic optical link interruptions, the experiment confirmed the DTN protocols' ability to handle real-world unexpected link outages while maintaining capability of

  5. Mediated Intercultural Communication Barrier in No Drama Zone! Group

    OpenAIRE

    Lizal, Valentino

    2015-01-01

    This research study aimed to describe the mediated intercultural communication barriers in the No Drama Zone! group. This study is a qualitative descriptive type of research, with case study method. By doing in depth interview and observation, researcher found two barriers that generates other barriers in the group's mediated intercultural communication. The two big barriers were: language and physical barriers. Language barriers in this group generated two barriers, emotional barrier and pe...

  6. Advanced Secure Optical Image Processing for Communications

    Science.gov (United States)

    Al Falou, Ayman

    2018-04-01

    New image processing tools and data-processing network systems have considerably increased the volume of transmitted information such as 2D and 3D images with high resolution. Thus, more complex networks and long processing times become necessary, and high image quality and transmission speeds are requested for an increasing number of applications. To satisfy these two requests, several either numerical or optical solutions were offered separately. This book explores both alternatives and describes research works that are converging towards optical/numerical hybrid solutions for high volume signal and image processing and transmission. Without being limited to hybrid approaches, the latter are particularly investigated in this book in the purpose of combining the advantages of both techniques. Additionally, pure numerical or optical solutions are also considered since they emphasize the advantages of one of the two approaches separately.

  7. Optical rangefinding applications using communications modulation technique

    Science.gov (United States)

    Caplan, William D.; Morcom, Christopher John

    2010-10-01

    A novel range detection technique combines optical pulse modulation patterns with signal cross-correlation to produce an accurate range estimate from low power signals. The cross-correlation peak is analyzed by a post-processing algorithm such that the phase delay is proportional to the range to target. This technique produces a stable range estimate from noisy signals. The advantage is higher accuracy obtained with relatively low optical power transmitted. The technique is useful for low cost, low power and low mass sensors suitable for tactical use. The signal coding technique allows applications including IFF and battlefield identification systems.

  8. Teaching Small Group Communication: A Do Good Project

    Directory of Open Access Journals (Sweden)

    Elizabeth M. Minei, PhD

    2016-08-01

    Full Text Available This paper focuses on the parameters of a semester-long project called the “Do Good” project, geared towards developing small group communication skills in undergraduate students. This project highlights participation in a social engagement project that allows students to bridge concepts learned in small group communication lectures (e.g., team dynamics, project management, conflict resolution, decision making, leadership with community outreach. Included are an overview of the project, and examples for how each component both challenges students’ ability to communicate in groups and provides motivation that foster students’ ability to link in-class knowledge with practical, real world application.

  9. Active optical cable for intrasatellite communications

    Science.gov (United States)

    Blasco, J.; Cano, D.; Navasquillo, O.; Esteban, M. A.

    2017-11-01

    DAS Photonics and Airbus Defence and Space (Spain) have been working for more than six years in the concept of an Active Optical Cable (AOC) for copper cable substitution. The main advantages that AOC offers are significant mass and size saving, better flexibility and routing of the cable and immunity to EMI.

  10. Per-Pixel, Dual-Counter Scheme for Optical Communications

    Science.gov (United States)

    Farr, William H.; Bimbaum, Kevin M.; Quirk, Kevin J.; Sburlan, Suzana; Sahasrabudhe, Adit

    2013-01-01

    Free space optical communications links from deep space are projected to fulfill future NASA communication requirements for 2020 and beyond. Accurate laser-beam pointing is required to achieve high data rates at low power levels.This innovation is a per-pixel processing scheme using a pair of three-state digital counters to implement acquisition and tracking of a dim laser beacon transmitted from Earth for pointing control of an interplanetary optical communications system using a focal plane array of single sensitive detectors. It shows how to implement dim beacon acquisition and tracking for an interplanetary optical transceiver with a method that is suitable for both achieving theoretical performance, as well as supporting additional functions of high data rate forward links and precision spacecraft ranging.

  11. Reinforcing Visual Grouping Cues to Communicate Complex Informational Structure.

    Science.gov (United States)

    Bae, Juhee; Watson, Benjamin

    2014-12-01

    In his book Multimedia Learning [7], Richard Mayer asserts that viewers learn best from imagery that provides them with cues to help them organize new information into the correct knowledge structures. Designers have long been exploiting the Gestalt laws of visual grouping to deliver viewers those cues using visual hierarchy, often communicating structures much more complex than the simple organizations studied in psychological research. Unfortunately, designers are largely practical in their work, and have not paused to build a complex theory of structural communication. If we are to build a tool to help novices create effective and well structured visuals, we need a better understanding of how to create them. Our work takes a first step toward addressing this lack, studying how five of the many grouping cues (proximity, color similarity, common region, connectivity, and alignment) can be effectively combined to communicate structured text and imagery from real world examples. To measure the effectiveness of this structural communication, we applied a digital version of card sorting, a method widely used in anthropology and cognitive science to extract cognitive structures. We then used tree edit distance to measure the difference between perceived and communicated structures. Our most significant findings are: 1) with careful design, complex structure can be communicated clearly; 2) communicating complex structure is best done with multiple reinforcing grouping cues; 3) common region (use of containers such as boxes) is particularly effective at communicating structure; and 4) alignment is a weak structural communicator.

  12. Research on Retro-reflecting Modulation in Space Optical Communication System

    Science.gov (United States)

    Zhu, Yifeng; Wang, Guannan

    2018-01-01

    Retro-reflecting modulation space optical communication is a new type of free space optical communication technology. Unlike traditional free space optical communication system, it applys asymmetric optical systems to reduce the size, weight and power consumption of the system and can effectively solve the limits of traditional free space optical communication system application, so it can achieve the information transmission. This paper introduces the composition and working principle of retro-reflecting modulation optical communication system, analyzes the link budget of this system, reviews the types of optical system and optical modulator, summarizes this technology future research direction and application prospects.

  13. Small-Group Discourse: Establishing a Communication-Rich Classroom

    Science.gov (United States)

    Quebec Fuentes, Sarah

    2013-01-01

    Establishing a communication-rich classroom can be difficult. This article describes the process and findings of a practitioner action research study addressing the question of how teachers can interact with their students while they are working in groups to encourage and enhance student-to-student communication. Recommended research-based teacher…

  14. Research progress of free space coherent optical communication

    Science.gov (United States)

    Tan, Zhenkun; Ke, Xizheng

    2018-02-01

    This paper mainly introduces the research progress of free space coherent optical communication in Xi'an University of Technology. In recent years, the research on the outer modulation technology of the laser, free-space-to-fiber coupling technique, the design of transmitting and receiving optical antenna, adaptive optical technology with or without wave-front sensor, automatic polarization control technology, frequency stabilization technology, heterodyne detection technology and high speed signal processing technology. Based on the above related research, the digital signal modulation, transmission, detection and data recovery are realized by the heterodyne detection technology in the free space optical communication system, and finally the function of smooth viewing high-definition video is realized.

  15. High-speed photodetectors in optical communication system

    Science.gov (United States)

    Zhao, Zeping; Liu, Jianguo; Liu, Yu; Zhu, Ninghua

    2017-12-01

    This paper presents a review and discussion for high-speed photodetectors and their applications on optical communications and microwave photonics. A detailed and comprehensive demonstration of high-speed photodetectors from development history, research hotspots to packaging technologies is provided to the best of our knowledge. A few typical applications based on photodetectors are also illustrated, such as free-space optical communications, radio over fiber and millimeter terahertz signal generation systems. Project supported by the Preeminence Youth Fund of China (No. 61625504).

  16. Ring resonator systems to perform optical communication enhancement using soliton

    CERN Document Server

    Amiri, Iraj Sadegh

    2014-01-01

    The title explain new technique of secured and high capacity optical communication signals generation by using the micro and nano ring resonators. The pulses are known as soliton pulses which are more secured due to having the properties of chaotic and dark soliton signals with ultra short bandwidth. They have high capacity due to the fact that ring resonators are able to generate pulses in the form of solitons in multiples and train form. These pulses generated by ring resonators are suitable in optical communication due to use the compact and integrated rings system, easy to control, flexibi

  17. Research on optic antenna of space laser communication networking

    Science.gov (United States)

    Meng, Li-Xin; Li, Long; Zhang, Li-zhong; Zhao, Shan-shan; Jiang, Hui-lin

    2013-08-01

    With the highlights of the high transmission rate, large capacity, strong anti-interference and anti-capture ability, good security and small light, space laser communication becomes an important hotspot. At present, the focus of research of the laser communication system is point to point communication structure. However, from the application point of view, both the realization of space laser communication among multiple points and the establishment of the information transmission network can really have the practical value. Aiming at the problem of space laser communication network, this article puts forward the general idea about optical antenna to achieve multiple tracking goals at the same time. Through the analysis of the optical antenna, and the comparing of the current commonly used mirror driving mechanism, a new mirror driving mechanism is designed. The azimuth motion, containing circular grating feedback, is driven by torque motor,voice coil motor of fan produces pitch motion that has fan-shaped grating feedback, so that compression of the structure size to improve the efficiency of the reflector assembly. Through the establishment of the driving mechanism and the kinematic model of 3D entity, the relationship between the single drive azimuth and pitch angle following the angle of incident light is explained. The biggest ideal view area affecting the optical antenna is obtained by the simulation analysis of the kinematics model using MATLAB. The several factors of field overlap area and blind area offers a theoretical basis for structure optimization and control system for the subsequent optical antenna design.

  18. Method and apparatus for optical communication by frequency modulation

    Science.gov (United States)

    Priatko, Gordon J.

    1988-01-01

    Laser optical communication according to this invention is carried out by producing multi-frequency laser beams having different frequencies, splitting one or more of these constituent beams into reference and signal beams, encoding information on the signal beams by frequency modulation and detecting the encoded information by heterodyne techniques. Much more information can be transmitted over optical paths according to the present invention than with the use of only one path as done previously.

  19. An Optical Receiver Post Processing System for the Integrated Radio and Optical Communications Software Defined Radio Test Bed

    Science.gov (United States)

    Nappier, Jennifer M.; Tokars, Roger P.; Wroblewski, Adam C.

    2016-01-01

    The Integrated Radio and Optical Communications (iROC) project at the National Aeronautics and Space Administrations (NASA) Glenn Research Center is investigating the feasibility of a hybrid radio frequency (RF) and optical communication system for future deep space missions. As a part of this investigation, a test bed for a radio frequency (RF) and optical software defined radio (SDR) has been built. Receivers and modems for the NASA deep space optical waveform are not commercially available so a custom ground optical receiver system has been built. This paper documents the ground optical receiver, which is used in order to test the RF and optical SDR in a free space optical communications link.

  20. An Optical Receiver Post-Processing System for the Integrated Radio and Optical Communications Software Defined Radio Test Bed

    Science.gov (United States)

    Nappier, Jennifer M.; Tokars, Roger P.; Wroblewski, Adam C.

    2016-01-01

    The Integrated Radio and Optical Communications (iROC) project at the National Aeronautics and Space Administration's (NASA) Glenn Research Center is investigating the feasibility of a hybrid radio frequency (RF) and optical communication system for future deep space missions. As a part of this investigation, a test bed for a radio frequency (RF) and optical software defined radio (SDR) has been built. Receivers and modems for the NASA deep space optical waveform are not commercially available so a custom ground optical receiver system has been built. This paper documents the ground optical receiver, which is used in order to test the RF and optical SDR in a free space optical communications link.

  1. Sex Role Identity, Communication Skills, and Group Popularity

    OpenAIRE

    Loredana Ivan

    2017-01-01

    Using two groups of undergraduate students (N = 71) the present paper argues about the importance of sex role identity (Bem, 1981) as a potential predictor of group popularity. The results show that participants with psychological androgine identity tend to use better their communication skills and become popular among their peers. Contray to previous studies (e.g. Hall, 1984; Saarni, 1999) focused on gender gap in communication skills, the current study emphasis on the importance of the sex ...

  2. Quantum dot devices for optical communications

    DEFF Research Database (Denmark)

    Mørk, Jesper

    2005-01-01

    -low threshold currents and amplifiers with record-high power levels. In this tutorial we will review the basic properties of quantum dots, emphasizing the properties which are important for laser and amplifier applications, as well as devices for all-optical signal processing. The high-speed properties....... The main property of semiconductor quantum dots compared to bulk material or even quantum well structures is the discrete nature of the allowed states, which means that inversion of the medium can be obtained for very low electron densities. This has led to the fabrication of quantum dot lasers with record...

  3. Acemind new indoor full duplex optical wireless communication prototype

    Science.gov (United States)

    Bouchet, Olivier; Perrufel, Micheline; Topsu, Suat; Guan, Hongyu

    2016-09-01

    For over a century and Mr. Guglielmo Marconi invention, systems using radio waves have controlled over wireless telecommunication solutions; from Amplitude Modulation (AM) radio products to satellite communications for instance. But beyond an increasingly negative opinion face to radio waves and radio spectrum availability more and more reduced; there is an unprecedented opportunity with LED installation in displays and lighting to provide optical wireless communication solutions. As a result, technologically mature solutions are already commercially available for services such as Location Based Services (LBS), broadcast diffusion or Intelligent Transport Services (ITS). Pending finalization of the standard review process IEEE 802.15.7 r1, our paper presents the results of the European collaborative project named "ACEMIND". It offers an indoor bilateral optical wireless communication prototype having the following characteristics: use of the existing electrical infrastructure, through judicious combination with Light Fidelity (LiFi), Power Line Communication (PLC) and Ethernet to reduce the implementation cost. We propose a bilateral optical wireless communication even when the light is switched off by using Visible Light Communication (VLC) and Infra-Red Communication (IRC) combined to a remote optical switch. Dimensionally optimized LiFi module is presented in order to offer the possibility for integration inside a laptop. Finally, there is operational mechanism implementation such as OFDM/DMT to increase throughput. After the introduction, we will present the results of a market study from Orange Labs customers about their opinion on LiFi components. Then we will detail the LiFi prototype, from the physical layer aspect to MAC layer before concluding on commercial development prospects.

  4. Breakthrough Science Enabled by Smallsat Optical Communication

    Science.gov (United States)

    Gorjian, V.

    2017-12-01

    The recent NRC panel on "Achieving Science with Cubesats" found that "CubeSats have already proven themselves to be an important scientific tool. CubeSats can produce high-value science, as demonstrated by peer-reviewed publications that address decadal survey science goals." While some science is purely related to the size of the collecting aperture, there are plentiful examples of new and exciting experiments that can be achieved using the relatively inexpensive Cubesat platforms. We will present various potential science applications that can benefit from higher bandwidth communication. For example, on or near Earth orbit, Cubesats could provide hyperspectral imaging, gravity field mapping, atmospheric probing, and terrain mapping. These can be achieved either as large constellations of Cubesats or a few Cubesats that provide multi-point observations. Away from the Earth (up to 1AU) astrophysical variability studies, detections of solar particles between the Earth and Venus, mapping near earth objects, and high-speed videos of the Sun will also be enabled by high bandwidth communications.

  5. Optical Fiber for High-Power Optical Communication

    Directory of Open Access Journals (Sweden)

    Kenji Kurokawa

    2012-09-01

    Full Text Available We examined optical fibers suitable for avoiding such problems as the fiber fuse phenomenon and failures at bends with a high power input. We found that the threshold power for fiber fuse propagation in photonic crystal fiber (PCF and hole-assisted fiber (HAF can exceed 18 W, which is more than 10 times that in conventional single-mode fiber (SMF. We considered this high threshold power in PCF and HAF to be caused by a jet of high temperature fluid penetrating the air holes. We showed examples of two kinds of failures at bends in conventional SMF when the input power was 9 W. We also observed the generation of a fiber fuse under a condition that caused a bend-loss induced failure. We showed that one solution for the failures at bends is to use optical fibers with a low bending loss such as PCF and HAF. Therefore, we consider PCF and HAF to be attractive solutions to the problems of the fiber fuse phenomenon and failures at bends with a high power input.

  6. Kansas Communication and Instruction System through Fiber-Optic Transmission.

    Science.gov (United States)

    Kansas State Dept. of Education, Topeka.

    Schools and communities will restructure as they move into the next decade. The success of this restructuring will be dependent upon access to and sharing of quality teaching and information through an expanded communication system. One of the major two-way interactive technologies is the fiber-optic cable: a delivery system that will provide…

  7. Underwater Optical Wireless Communications, Networking, and Localization: A Survey

    KAUST Repository

    Saeed, Nasir; Celik, Abdulkadir; Al-Naffouri, Tareq Y.; Alouini, Mohamed-Slim

    2018-01-01

    Underwater wireless communications can be carried out through acoustic, radio frequency (RF), and optical waves. Compared to its bandwidth limited acoustic and RF counterparts, underwater optical wireless communications (UOWCs) can support higher data rates at low latency levels. However, severe aquatic channel conditions (e.g., absorption, scattering, turbulence, etc.) pose great challenges for UOWCs and significantly reduce the attainable communication ranges, which necessitates efficient networking and localization solutions. Therefore, we provide a comprehensive survey on the challenges, advances, and prospects of underwater optical wireless networks (UOWNs) from a layer by layer perspective which includes: 1) Potential network architectures; 2) Physical layer issues including propagation characteristics, channel modeling, and modulation techniques 3) Data link layer problems covering link configurations, link budgets, performance metrics, and multiple access schemes; 4) Network layer topics containing relaying techniques and potential routing algorithms; 5) Transport layer subjects such as connectivity, reliability, flow and congestion control; 6) Application layer goals and state-of-the-art UOWN applications, and 7) Localization and its impacts on UOWN layers. Finally, we outline the open research challenges and point out the future directions for underwater optical wireless communications, networking, and localization research.

  8. Free Space Optics Communication for Mobile Military Platforms

    Science.gov (United States)

    2003-12-01

    Federal Communications Commission FDA Food and Drug Administration FOV Field-of-View FSO Free Space Optics FWHM Full Width at Half Maximum Gbps...Physique et de Métrologie des Oscillateurs (LPMO) du CNRS UPR3203, associé à l’Université de Franche -Comté, 15 March 2002 [Schenk 2000] H. Schenk

  9. Underwater Optical Wireless Communications, Networking, and Localization: A Survey

    KAUST Repository

    Saeed, Nasir

    2018-02-28

    Underwater wireless communications can be carried out through acoustic, radio frequency (RF), and optical waves. Compared to its bandwidth limited acoustic and RF counterparts, underwater optical wireless communications (UOWCs) can support higher data rates at low latency levels. However, severe aquatic channel conditions (e.g., absorption, scattering, turbulence, etc.) pose great challenges for UOWCs and significantly reduce the attainable communication ranges, which necessitates efficient networking and localization solutions. Therefore, we provide a comprehensive survey on the challenges, advances, and prospects of underwater optical wireless networks (UOWNs) from a layer by layer perspective which includes: 1) Potential network architectures; 2) Physical layer issues including propagation characteristics, channel modeling, and modulation techniques 3) Data link layer problems covering link configurations, link budgets, performance metrics, and multiple access schemes; 4) Network layer topics containing relaying techniques and potential routing algorithms; 5) Transport layer subjects such as connectivity, reliability, flow and congestion control; 6) Application layer goals and state-of-the-art UOWN applications, and 7) Localization and its impacts on UOWN layers. Finally, we outline the open research challenges and point out the future directions for underwater optical wireless communications, networking, and localization research.

  10. A COTS RF Optical Software Defined Radio for the Integrated Radio and Optical Communications Test Bed

    Science.gov (United States)

    Nappier, Jennifer M.; Zeleznikar, Daniel J.; Wroblewski, Adam C.; Tokars, Roger P.; Schoenholz, Bryan L.; Lantz, Nicholas C.

    2016-01-01

    The Integrated Radio and Optical Communications (iROC) project at the National Aeronautics and Space Administration (NASA) is investigating the merits of a hybrid radio frequency (RF) and optical communication system for deep space missions. In an effort to demonstrate the feasibility and advantages of a hybrid RFOptical software defined radio (SDR), a laboratory prototype was assembled from primarily commercial-off-the-shelf (COTS) hardware components. This COTS platform has been used to demonstrate simultaneous transmission of the radio and optical communications waveforms through to the physical layer (telescope and antenna). This paper details the hardware and software used in the platform and various measures of its performance. A laboratory optical receiver platform has also been assembled in order to demonstrate hybrid free space links in combination with the transmitter.

  11. The 2004 Latsis Symposium: Quantum optics for Communication and Computing

    CERN Multimedia

    2004-01-01

    1-3 March 2004 Ecole Polytechnique Fédérale de Lausanne Auditoire SG1 The field of Quantum Optics covers topics that extend from basic physical concepts, regarding the quantum description of light, matter, and light-matter interaction, to the applications of these concepts in future information and communication technologies. This field is of primary importance for science and society for two reasons. Firstly, it brings a deeper physical understanding of the fundamental aspects of modern quantum physics. Secondly, it offers perspectives for the invention and implementation of new devices and systems in the fields of communications, information management and computing. The themes that will be addressed in the Latsis Symposium on Quantum Optics are quantum communications, quantum computation, and quantum photonic devices. The objective of the symposium is to give an overview of this fascinating and rapidly evolving field. The different talks will establish links between new fundamental c...

  12. The 2004 Latsis Symposium: Quantum optics for Communication and Computing

    CERN Multimedia

    2004-01-01

    1-3 March 2004 Ecole Polytechnique Fédérale de Lausanne Auditoire SG1 The field of Quantum Optics covers topics that extend from basic physical concepts, regarding the quantum description of light, matter, and light-matter interaction, to the applications of these concepts in future information and communication technologies. This field is of primary importance for science and society for two reasons. Firstly, it brings a deeper physical understanding of the fundamental aspects of modern quantum physics. Secondly, it offers perspectives for the invention and implementation of new devices and systems in the fields of communications, information management and computing. The themes that will be addressed in the Latsis Symposium on Quantum Optics are quantum communications, quantum computation, and quantum photonic devices. The objective of the symposium is to give an overview of this fascinating and rapidly evolving field. The different talks will establish links between new fundamental...

  13. The 2004 Latsis Symposium: Quantum optics for Communication and Computing

    CERN Multimedia

    2004-01-01

    1-3 March 2004 Ecole Polytechnique Fédérale de Lausanne Auditoire SG1 The field of Quantum Optics covers topics that extend from basic physical concepts, regarding the quantum description of light, matter, and light-matter interaction, to the applications of these concepts in future information and communication technologies. This field is of primary importance for science and society for two reasons. Firstly, it brings a deeper physical understanding of the fundamental aspects of modern quantum physics. Secondly, it offers perspectives for the invention and implementation of new devices and systems in the fields of communications, information management and computing. The themes that will be addressed in the Latsis Symposium on Quantum Optics are quantum communications, quantum computation, and quantum photonic devices. The objective of the symposium is to give an overview of this fascinating and rapidly evolving field. The different talks will establish links between new fundamental ...

  14. Invited Article: Visualisation of extreme value events in optical communications

    Science.gov (United States)

    Derevyanko, Stanislav; Redyuk, Alexey; Vergeles, Sergey; Turitsyn, Sergei

    2018-06-01

    Fluctuations of a temporal signal propagating along long-haul transoceanic scale fiber links can be visualised in the spatio-temporal domain drawing visual analogy with ocean waves. Substantial overlapping of information symbols or use of multi-frequency signals leads to strong statistical deviations of local peak power from an average signal power level. We consider long-haul optical communication systems from this unusual angle, treating them as physical systems with a huge number of random statistical events, including extreme value fluctuations that potentially might affect the quality of data transmission. We apply the well-established concepts of adaptive wavefront shaping used in imaging through turbid medium to detect the detrimental phase modulated sequences in optical communications that can cause extreme power outages (rare optical waves of ultra-high amplitude) during propagation down the ultra-long fiber line. We illustrate the concept by a theoretical analysis of rare events of high-intensity fluctuations—optical freak waves, taking as an example an increasingly popular optical frequency division multiplexing data format where the problem of high peak to average power ratio is the most acute. We also show how such short living extreme value spikes in the optical data streams are affected by nonlinearity and demonstrate the negative impact of such events on the system performance.

  15. The Finite Heisenberg-Weyl Groups in Radar and Communications

    Directory of Open Access Journals (Sweden)

    Calderbank AR

    2006-01-01

    Full Text Available We investigate the theory of the finite Heisenberg-Weyl group in relation to the development of adaptive radar and to the construction of spreading sequences and error-correcting codes in communications. We contend that this group can form the basis for the representation of the radar environment in terms of operators on the space of waveforms. We also demonstrate, following recent developments in the theory of error-correcting codes, that the finite Heisenberg-Weyl groups provide a unified basis for the construction of useful waveforms/sequences for radar, communications, and the theory of error-correcting codes.

  16. Applications of plastic optical fiber in communication

    Science.gov (United States)

    Tayahi, Moncef Ben

    In this thesis, we report the results of our theoretical and experimental studies of large core polymer fibers. This relatively low loss and high bandwidth plastic optical fiber (POF) potentially have important applications in LAN. We measured the power penalty due to modal noise. We also developed a model to calculate the signal to noise ratio (SNR) and the bit error rate (BER) floor just by knowing the coupling coefficient in the mode selective loss being considered. The calculated bandwidth using the WKB approximation was found to be 0.44 GHz per 100 m, which is much lower than the measured bandwidth of 3 GHz per 100 m. This discrepancy was explained by the presence of strong mode coupling in POFs. We studied distortions products in CATV systems. Composite second order (CSO) and composite triple beat (CTB) for different channels were measured using a spectrum analyzer and adjustable band pass filter. Since the CSO and the CTB did not meet the CATV standard, a predistortion circuit was used to minimize CSO and CTB products produced by the laser. The predistortion circuit provides a signal comprising multiple subcarrier signals substantially equal in magnitude and opposite in phase to those associated with the nonlinear transfer function of the laser being deployed. The RF signal is split into a primary branch that has a time delayed portion (80% of the RF signal), the secondary branch (10% of the RF signal) is where the second order products are generated with a 180 °phase shift from the fundamental, and the last remaining 10% of the RF signal is where the third order distortion products are generated with a 180 °phase shift from the fundamental. The output signal is taken as the summation of three signals processed by the branch circuits and coupled to the directly to the laser to be linearized. Finally, using cyclic transparent optical polymer (CYTOP), a perfluorinated graded index fiber, different transmission characteristics were investigated. CYTOP fiber

  17. Communication and Social Exchange Processes in Community Theater Groups

    Science.gov (United States)

    Kramer, Michael W.

    2005-01-01

    This study explores the communication experiences of two volunteer groups involved in the production of community theater musicals. Based on social exchange theory, it examined what group members perceived to be the positive benefits (primarily meeting people and having an opportunity to perform) and the negative costs (primarily disorganization,…

  18. Spectrum Scarcity and Free Space Optical Communications

    KAUST Repository

    Alouini, Mohamed-Slim

    2014-01-06

    Exact and asymptotic studies of the average error probability of wireless communication systems over generalized fading channels have been extensively pursued over the last two decades. In contrast, studies and results dealing with the channel capacity in these environments have been more scarce. In the first part of this talk, we present a generic moment generating function-based approach for the exact computation of the channel capacity in such kind of environments. The resulting formulas are applicable to systems having channel state information (CSI) at the receiver and employing maximal-ratio combining or equal-gain combining multichannel reception. The analysis covers the case where the combined paths are not necessarily independent or identically distributed. In all cases, the proposed approach leads to an expression of the ergodic capacity involving a single finite-range integral, which can be easily computed numerically. In the second part of the talk, we focus on the asymptotic analysis of the capacity in the high and low signal-to-noise ratio (SNR) regimes. More specifically, we offer new simple closed-form formulas that give an intuitive understanding of the capacity behavior at these two extreme regimes. Our characterization covers not only the case where the CSI is available only at the receiver but also the case where the CSI is available at both the transmitter and receiver.

  19. Digital Signal Processing for Optical Coherent Communication Systems

    DEFF Research Database (Denmark)

    Zhang, Xu

    spectrum narrowing tolerance 112-Gb/s DP-QPSK optical coherent systems using digital adaptive equalizer. The demonstrated results show that off-line DSP algorithms are able to reduce the bit error rate (BER) penalty induced by signal spectrum narrowing. Third, we also investigate bi...... wavelength division multiplex (U-DWDM) optical coherent systems based on 10-Gbaud QPSK. We report U-DWDM 1.2-Tb/s QPSK coherent system achieving spectral efficiency of 4.0-bit/s/Hz. In the experimental demonstration, digital decision feed back equalizer (DFE) algorithms and a finite impulse response (FIR......In this thesis, digital signal processing (DSP) algorithms are studied to compensate for physical layer impairments in optical fiber coherent communication systems. The physical layer impairments investigated in this thesis include optical fiber chromatic dispersion, polarization demultiplexing...

  20. 78 FR 16296 - Certain Optoelectronic Devices for Fiber Optic Communications, Components Thereof, and Products...

    Science.gov (United States)

    2013-03-14

    ... Fiber Optic Communications, Components Thereof, and Products Containing Same; Commission Determination... United States after importation of certain optoelectronic devices for fiber optic communications... Fiber IP (Singapore) Pte. Ltd. of Singapore (``Avago Fiber IP''); Avago General IP and Avago...

  1. Experimental multiplexing of quantum key distribution with classical optical communication

    International Nuclear Information System (INIS)

    Wang, Liu-Jun; Chen, Luo-Kan; Ju, Lei; Xu, Mu-Lan; Zhao, Yong; Chen, Kai; Chen, Zeng-Bing; Chen, Teng-Yun; Pan, Jian-Wei

    2015-01-01

    We demonstrate the realization of quantum key distribution (QKD) when combined with classical optical communication, and synchronous signals within a single optical fiber. In the experiment, the classical communication sources use Fabry-Pérot (FP) lasers, which are implemented extensively in optical access networks. To perform QKD, multistage band-stop filtering techniques are developed, and a wavelength-division multiplexing scheme is designed for the multi-longitudinal-mode FP lasers. We have managed to maintain sufficient isolation among the quantum channel, the synchronous channel and the classical channels to guarantee good QKD performance. Finally, the quantum bit error rate remains below a level of 2% across the entire practical application range. The proposed multiplexing scheme can ensure low classical light loss, and enables QKD over fiber lengths of up to 45 km simultaneously when the fibers are populated with bidirectional FP laser communications. Our demonstration paves the way for application of QKD to current optical access networks, where FP lasers are widely used by the end users

  2. Radiation resistance characteristics of optical communication system for single mode

    International Nuclear Information System (INIS)

    Ohe, Masamoto; Chigusa, Yoshiki; Kyodo, Tomohisa; Tanaka, Gohtaro; Watanabe, Hajime; Okamoto, Shin-ichi; Yamamoto, Takao.

    1988-01-01

    Optical communication has been utilized also for nuclear power stations and fuel reporocessing plants. As the sufficient safety countermeasures are required there, the amount of information becomes enormous, therefore, optical communication, by which the required space is expected to be reduced, becomes more important. Also in the application to submarine cables, attention must be paid to the radiation resistance as there are the effects of potassium contained in large amount in seawater and uranium deposits in sea bottom. Therefore, the reliability of the components of optical communication systems against radiation becomes a problem. In this study, single mode optical fibers and transmission and receipt modules were selected, and high dose rate irradiation supposing the case of using in a cell and low dose rate, long time irradiation supposing the case of submarine cables were carried out to evaluate the radiation resistance characteristics. The fibers tested were SiO 2 core/F-SiO 2 clad type and GeO 2 -SiO 2 core/SiO 2 clad type. The characteristics of increasing loss in irradiation and restoration after irradiation of the former type were superior to those of the latter type. The output of a receipt module was normal during irradiation, and the output power of a transmission module decreases, but other problems did not arise. (K.I.)

  3. Nuclear post-accident communication: reflections of CODIR-PA's 'Communication' work group (GT8)

    International Nuclear Information System (INIS)

    2010-01-01

    This document briefly presents the approach adopted in France to define a communication doctrine to be applied in a post-accident situation, to make practical recommendations to actors, and to develop practical tools (speech elements). It evokes the main themes dealt with (such as safety culture, communication, etc.) by a specific work group

  4. LDPC-PPM Coding Scheme for Optical Communication

    Science.gov (United States)

    Barsoum, Maged; Moision, Bruce; Divsalar, Dariush; Fitz, Michael

    2009-01-01

    In a proposed coding-and-modulation/demodulation-and-decoding scheme for a free-space optical communication system, an error-correcting code of the low-density parity-check (LDPC) type would be concatenated with a modulation code that consists of a mapping of bits to pulse-position-modulation (PPM) symbols. Hence, the scheme is denoted LDPC-PPM. This scheme could be considered a competitor of a related prior scheme in which an outer convolutional error-correcting code is concatenated with an interleaving operation, a bit-accumulation operation, and a PPM inner code. Both the prior and present schemes can be characterized as serially concatenated pulse-position modulation (SCPPM) coding schemes. Figure 1 represents a free-space optical communication system based on either the present LDPC-PPM scheme or the prior SCPPM scheme. At the transmitting terminal, the original data (u) are processed by an encoder into blocks of bits (a), and the encoded data are mapped to PPM of an optical signal (c). For the purpose of design and analysis, the optical channel in which the PPM signal propagates is modeled as a Poisson point process. At the receiving terminal, the arriving optical signal (y) is demodulated to obtain an estimate (a^) of the coded data, which is then processed by a decoder to obtain an estimate (u^) of the original data.

  5. Optical intersatellite links - Application to commercial satellite communications

    Science.gov (United States)

    Paul, D.; Faris, F.; Garlow, R.; Inukai, T.; Pontano, B.; Razdan, R.; Ganz, Aura; Caudill, L.

    1992-01-01

    Application of optical intersatellite links for commercial satellite communications services is addressed in this paper. The feasibility of commercialization centers around basic issues such as the need and derived benefits, implementation complexity and overall cost. In this paper, commercialization of optical ISLs is assessed in terms of the services provided, systems requirements and feasibility of appropriate technology. Both long- and short-range ISLs for GEO-GEO, GEO-LEO and LEO applications are considered. Impact of systems requirements on the payload design and use of advanced technology in reducing its mass, power, and volume requirements are discussed.

  6. Video semaphore decoding for free-space optical communication

    Science.gov (United States)

    Last, Matthew; Fisher, Brian; Ezekwe, Chinwuba; Hubert, Sean M.; Patel, Sheetal; Hollar, Seth; Leibowitz, Brian S.; Pister, Kristofer S. J.

    2001-04-01

    Using teal-time image processing we have demonstrated a low bit-rate free-space optical communication system at a range of more than 20km with an average optical transmission power of less than 2mW. The transmitter is an autonomous one cubic inch microprocessor-controlled sensor node with a laser diode output. The receiver is a standard CCD camera with a 1-inch aperture lens, and both hardware and software implementations of the video semaphore decoding algorithm. With this system sensor data can be reliably transmitted 21 km form San Francisco to Berkeley.

  7. Cross-correlation interference effects in multiaccess optical communications

    Science.gov (United States)

    Peterson, G. D.; Gardner, C. S.

    1981-03-01

    An analysis is presented of the cross correlation between user codes in an optical code-division multiple-access communication system. The system model is a multiaccess satellite repeater, where the uplink and downlink channels are direct-detection optical-polarization modulation links. The error probability is obtained in terms of the cross correlation between the intended and interfering user codes. It is demonstrated that the system error rate can be minimized by the use of code sequences in which the normalized second moment of the cross correlation between codes is small.

  8. Optical fiber communication systems with Matlab and Simulink models

    CERN Document Server

    Binh, Le Nguyen

    2014-01-01

    ""This book adds an aspect of programming and simulation not so well developed in other books. It is complete in this sense and enables directly linking the physics of optical components and systems to realistic results.""-Martin Rochette, Associate Professor, McGill University, Quebec, Canada""…this will be an excellent textbook since it has all new development and information on optical communication systems…I think this book can easily replace many other textbooks in this field.""-Massoud Moussavi, California State Polytechnic University-Pomona""The book is well written. It describes the fu

  9. An Introduction to Free-space Optical Communications

    Directory of Open Access Journals (Sweden)

    H. Henniger

    2010-06-01

    Full Text Available Over the last two decades free-space optical communication (FSO has become more and more interesting as an adjunct or alternative to radio frequency communication. This article gives an overview of the challenges a system designer has to consider while implementing an FSO system. Typical gains and losses along the path from the transmitter through the medium to the receiver are introduced in this article. Detailed discussions of these topics can be found in this special issue of the Radioengineering Journal.

  10. Architectural Options for a Future Deep Space Optical Communications Network

    Science.gov (United States)

    Edwards, B. L.; Benjamin, T.; Scozzafava, J.; Khatri, F.; Sharma, J.; Parvin, B.; Liebrecht, P. E.; Fitzgerald, R. J.

    2004-01-01

    This paper provides an overview of different options at Earth to provide Deep Space optical communication services. It is based mainly on work done for the Mars Laser Communications Demonstration (MLCD) Project, a joint project between NASA's Goddard Space Flight Center (GSFC), the Jet Propulsion Laboratory, California Institute of Technology (JPL), and the Massachusetts Institute of Technology Lincoln Laboratory (MIT/LL). It also reports preliminary conclusions from the Tracking and Data Relay Satellite System Continuation Study at GSFC. A lasercom flight terminal will be flown on the Mars Telecommunications Orbiter (MTO) to be launched by NASA in 2009, and will be the first high rate deep space demonstration of this revolutionary technology.

  11. An Array of Optical Receivers for Deep-Space Communications

    Science.gov (United States)

    Vilnrotter, Chi-Wung; Srinivasan, Meera; Andrews, Kenneth

    2007-01-01

    An array of small optical receivers is proposed as an alternative to a single large optical receiver for high-data-rate communications in NASA s Deep Space Network (DSN). Because the telescope for a single receiver capable of satisfying DSN requirements must be greater than 10 m in diameter, the design, building, and testing of the telescope would be very difficult and expensive. The proposed array would utilize commercially available telescopes of 1-m or smaller diameter and, therefore, could be developed and verified with considerably less difficulty and expense. The essential difference between a single-aperture optical-communications receiver and an optical-array receiver is that a single-aperture receiver focuses all of the light energy it collects onto the surface of an optical detector, whereas an array receiver focuses portions of the total collected energy onto separate detectors, optically detects each fractional energy component, then combines the electrical signal from the array of detector outputs to form the observable, or "decision statistic," used to decode the transmitted data. A conceptual block diagram identifying the key components of the optical-array receiver suitable for deep-space telemetry reception is shown in the figure. The most conspicuous feature of the receiver is the large number of small- to medium-size telescopes, with individual apertures and number of telescopes selected to make up the desired total collecting area. This array of telescopes is envisioned to be fully computer- controlled via the user interface and prediction-driven to achieve rough pointing and tracking of the desired spacecraft. Fine-pointing and tracking functions then take over to keep each telescope pointed toward the source, despite imperfect pointing predictions, telescope-drive errors, and vibration caused by wind.

  12. Performance of Cat's Eye Modulating Retro-Reflectors for Free-Space Optical Communications

    National Research Council Canada - National Science Library

    Rabinovich, W. S; Goetz, P. G; Mahon, R; Swingen, L; Murphy, J; Gilbreath, G. C; Binari, S; Waluschka, E

    2004-01-01

    Modulating retro-reflectors (MRR) couple passive optical retro-reflectors with electro-optic modulators to allow free-space optical communication with a laser and pointing/acquisition/tracking system required on only one end of the link...

  13. Communication as group process media of aircrew performance

    Science.gov (United States)

    Kanki, B. G.; Foushee, H. C.

    1989-01-01

    This study of group process was motivated by a high-fidelity flight simulator project in which aircrew performance was found to be better when the crew had recently flown together. Considering recent operating experience as a group-level input factor, aspects of the communication process between crewmembers (Captain and First Officer), were explored as a possible mediator to performance. Communication patterns were defined by a speech act typology adapted for the flightdeck setting and distinguished crews that had previously flown together (FT) from those that had not flown together (NFT). A more open communication channel with respect to information exchange and validation and greater First Officer participation in task-related topics was shown by FT crews while NFT crews engaged in more non-task discourse, a speech mode less structured by roles and probably serving a more interpersonal function. Relationships between the speech categories themselves, representing linguistic, and role-related interdependencies provide guidelines for interpreting the primary findings.

  14. Principles of optical fibre communication techniques: Noncoherent and coherent

    International Nuclear Information System (INIS)

    Jain, V.K.

    1990-01-01

    In this paper a brief historical description of optical fibre communication system (OFCS) has been presented and the main characteristics of the basic components used in it are summarized. Introduction of noncoherent and coherent (homodyne and heterodyne) system is given. In coherent OFCS, source linewidth requirement, phase and polarization - diversity and combined phase and polarization - diversity receivers are described. (author). 16 refs, 8 figs, 1 tab

  15. International standards for optical wireless communications: state-of-the-art and future directions

    Science.gov (United States)

    Marciniak, Marian

    2017-10-01

    As the number of active OWC installations is growing fast, the standards for compatibility of co-existing neighbouring systems are being developed. The paper addresses the Laser Safety (IEC standards), ITU-T Study Group 15 standards (G.640 Co-location longitudinally compatible interfaces for free space optical systems), ITU-Radiocommunication Sector standards (P.1817-1 Propagation data required for the design of terrestrial free-space optical links), and the IEEE Work in Progress - standardization activity on Visible Light Communications. International standards of FSO communications have been reviewed and discussed. ITU, IEC, and IEEE International standards for Free-Space Optical links have been reviewed. The system reliability and availability as well as security issues will be addressed as well in the talk.

  16. New generation of devices for all-optical communications

    International Nuclear Information System (INIS)

    Glesk, I.; Runser, R.J.; Prucnal, P.R.

    2001-01-01

    To increase the transmission capacity of future communication networks is becoming very critical. This task can only be accomplished by taking advantage of optical networks where multiplexing techniques such as Dense Wavelength Division Multiplexing (DWDM) and Optical Time Division Multiplexing (OTDM) are employed. To avoid electronic bottlenecks a whole new generation of ultrafast devices is needed. To fulfill these needs a new class of all optical devices has been proposed and developed. By taking advantage of the nonlinear dynamics in semiconductor optical amplifiers in combination with the fiber interferometers a new generation of ultrafast all-optical de multiplexers and wavelength converters has been demonstrated. Other switching technologies are also promising for the future. The latest technologies in the area of micro machining have created very attractive low cost MEMS. Recently announced use of bubble technology for all-optical switching might also lead to the development of next generation large scale switching fabrics. This paper is an overview of the recent development in these areas. (authors)

  17. The present moment and implicit communication in group psychotherapy.

    Science.gov (United States)

    Ulman, Kathleen Hubbs

    2011-04-01

    The importance of the concepts of present moment and implicit communication to group psychotherapy is discussed in relation to the articles by Gans and by Counselman and Abernethy and to the life work of Anne Alonso. Clinical examples are used to illustrate the discussion.

  18. Robust free-space optical communication for indoor information environment

    Science.gov (United States)

    Nakada, Toyohisa; Itoh, Hideo; Kunifuji, Susumu; Nakashima, Hideyuki

    2003-10-01

    The purpose of our study is to establish a robust communication, while keeping security and privacy, between a handheld communicator and the surrounding information environment. From the viewpoint of low power consumption, we have been developing a reflectivity modulating communication module composed of a liquid crystal light modulator and a corner-reflecting mirror sheet. We installed a corner-reflecting sheet instead of light scattering sheet in a handheld videogame machine with a display screen with a reflection-type liquid crystal. Infrared (IR) LED illuminator attached next to the IR camera of a base station illuminates all the room, and the terminal send their data to the base station by switching ON and OFF of the reflected IR beam. Intensity of reflected light differs with the position and the direction of the terminal, and sometimes the intensity of OFF signal at a certain condition is brighter than that of ON signal at another condition. To improve the communication quality, use of machine learning technique is a possibility of the solution. In this paper, we compare various machine learning techniques for the purpose of free space optical communication, and propose a new algorithm that improves the robustness of the data link. Evaluation using an actual free-space communication system is also described.

  19. Optical signal processing techniques and applications of optical phase modulation in high-speed communication systems

    Science.gov (United States)

    Deng, Ning

    In recent years, optical phase modulation has attracted much research attention in the field of fiber optic communications. Compared with the traditional optical intensity-modulated signal, one of the main merits of the optical phase-modulated signal is the better transmission performance. For optical phase modulation, in spite of the comprehensive study of its transmission performance, only a little research has been carried out in terms of its functions, applications and signal processing for future optical networks. These issues are systematically investigated in this thesis. The research findings suggest that optical phase modulation and its signal processing can greatly facilitate flexible network functions and high bandwidth which can be enjoyed by end users. In the thesis, the most important physical-layer technology, signal processing and multiplexing, are investigated with optical phase-modulated signals. Novel and advantageous signal processing and multiplexing approaches are proposed and studied. Experimental investigations are also reported and discussed in the thesis. Optical time-division multiplexing and demultiplexing. With the ever-increasing demand on communication bandwidth, optical time division multiplexing (OTDM) is an effective approach to upgrade the capacity of each wavelength channel in current optical systems. OTDM multiplexing can be simply realized, however, the demultiplexing requires relatively complicated signal processing and stringent timing control, and thus hinders its practicability. To tackle this problem, in this thesis a new OTDM scheme with hybrid DPSK and OOK signals is proposed. Experimental investigation shows this scheme can greatly enhance the demultiplexing timing misalignment and improve the demultiplexing performance, and thus make OTDM more practical and cost effective. All-optical signal processing. In current and future optical communication systems and networks, the data rate per wavelength has been approaching

  20. Data acquisition remote node powered over the communications optical fiber

    International Nuclear Information System (INIS)

    Batista, Antonio J.N.; Sousa, Jorge; Gonçalves, Bruno

    2015-01-01

    Large nuclear fusion reactors, like ITER, will have harsh electromagnetic environments nearby the machine. Foreseeing the necessity for special data acquisition remote nodes, on difficult access locations and as close as possible to the experimental devices, motivated the system design. The architecture is based on the power-over-fiber technology recent advancements and respective implementation aim is to attain a proof of concept for the fusion technology field and others, e.g., high energy physics, industry, etc. The design intends the replacement of traditional copper cables and power supplies, vulnerable to electromagnetic interference, by the communications optical fiber of the data acquisition remote node. Optical fibers provide galvanic isolation, immunity to noisy electromagnetic environments and simultaneously can supply power to the remote node electronics. System architecture uses a laser power converter (array of photovoltaic cells) to convert the laser light, from the optical fiber, into electricity. The generated electrical power is enough for powering the remote node electronics and optoelectronics, such as an ADC, a low power FPGA and an optical transmitter. The laser power converter is also used as the communications receiver and from which the acquisition clock is recovered, providing synchronism between remote data acquisition nodes. Descriptions of the system architecture, tested implementations and future improvements are presented.

  1. Advanced MEMS systems for optical communication and imaging

    International Nuclear Information System (INIS)

    Horenstein, M N; Sumner, R; Freedman, D S; Datta, M; Kani, N; Miller, P; Stewart, J B; Cornelissen, S

    2011-01-01

    Optical communication and adaptive optics have emerged as two important uses of micro-electromechanical (MEMS) devices based on electrostatic actuation. Each application uses a mirror whose surface is altered by applying voltages of up to 300 V. Previous generations of adaptive-optic mirrors were large (∼1 m) and required the use of piezoelectric transducers. Beginning in the mid-1990s, a new class of small MEMS mirrors (∼1 cm) were developed. These mirrors are now a commercially available, mature technology. This paper describes three advanced applications of MEMS mirrors. The first is a mirror used for corona-graphic imaging, whereby an interferometric telescope blocks the direct light from a distant star so that nearby objects such as planets can be seen. We have developed a key component of the system: a 144-channel, fully-scalable, high-voltage multiplexer that reduces power consumption to only a few hundred milliwatts. In a second application, a MEMS mirror comprises part of a two-way optical communication system in which only one node emits a laser beam. The other node is passive, incorporating a retro-reflective, electrostatic MEMS mirror that digitally encodes the reflected beam. In a third application, the short (∼100-ns) pulses of a commercially-available laser rangefinder are returned by the MEMS mirror as a digital data stream. Suitable low-power drive systems comprise part of the system design.

  2. Rejuvenating direct modulation and direct detection for modern optical communications

    Science.gov (United States)

    Che, Di; Li, An; Chen, Xi; Hu, Qian; Shieh, William

    2018-02-01

    High-speed transoceanic optical fiber transmission using direct modulation (DM) and direct detection (DD) was one of the most stirring breakthroughs for telecommunication in 1990s, which drove the internet as a global phenomenon. However, the later evolution of optical coherent communications in 2000s gradually took over the long-haul applications, due to its superior optical spectral efficiency. Nowadays, DM-DD systems are dominant mainly in cost- and power-sensitive short-reach applications, because of its natural characteristics-the simplicity. This paper reviews the recent advances of DM-DD transceivers from both hardware and signal processing perspectives. It introduces a variety of modified DM and/or DD systems for 3 application scenarios: very-short-reach interconnect with little fiber channel impact; single or a few spans of fiber transmission up to several hundred km; and distance beyond the 2nd scenario. Besides the DM-DD and multi-dimension DM-DD with polarization diversity, this paper focuses on how to rejuvenate traditional DM and DD technologies in order to bridge the transmission application gap between DM-DD and coherent transceivers, using technologies such as dispersion compensation, signal field recovery from the intensity-only DD receiver, and complex direct modulation with coherent detection. More than 30 years since the birth, DM and DD still hold indispensable roles in modern optical communications.

  3. Plastic optical fiber serial communications link for distributed control system

    Science.gov (United States)

    Saxena, Piyush; Sharangpani, K. K.; Vora, H. S.; Nakhe, S. V.; Jain, R.; Shenoy, N. M.; Bhatnagar, R.; Shirke, N. D.

    2001-09-01

    One of the most common interface for communications specified is RS 232C standard. Though widely accepted, RS232 has limited transmission speed, range and networking capabilities. RS 422 standard overcomes limitations by using differential signal lines. In automation of the operation of gas discharge lasers, multiple processors are used for control of lasers, cooling system, vacuum system etc. High EMI generated by lasers interfere through galvanic transmission or by radiation over the length of cables, and hang up operation of processors or control PC. A serial communications link was designed eliminating copper transmission media, using plastic optical fiber cables and components, to connect local controllers with the master PC working on RS232 protocols. The paper discusses the design and implementation of a high ly reliable EMI harden serial communications link.

  4. Advancing Unmanned Aircraft Sensor Collection and Communication Capabilities with Optical Communications

    Science.gov (United States)

    Lukaczyk, T.

    2015-12-01

    Unmanned aircraft systems (UAS) are now being used for monitoring climate change over both land and seas. Their uses include monitoring of cloud conditions and atmospheric composition of chemicals and aerosols due to pollution, dust storms, fires, volcanic activity and air-sea fluxes. Additional studies of carbon flux are important for various ecosystem studies of both marine and terrestrial environments specifically, and can be related to climate change dynamics. Many measurements are becoming more complex as additional sensors become small enough to operate on more widely available small UAS. These include interferometric radars as well as scanning and fan-beam lidar systems which produce data streams even greater than those of high resolution video. These can be used to precisely map surfaces of the earth, ocean or ice features that are important for a variety of earth system studies. As these additional sensor capabilities are added to UAS the ability to transmit data back to ground or ship monitoring sites is limited by traditional wireless communication protocols. We describe results of tests of optical communication systems that provide significantly greater communication bandwidths for UAS, and discuss both the bandwidth and effective range of these systems, as well as their power and weight requirements both for systems on UAS, as well as those of ground-based receiver stations. We justify our additional use of Delay and Disruption Tolerant Networking (DTN) communication protocols with optical communication methods to ensure security and continuity of command and control operations. Finally, we discuss the implications for receiving, geo-referencing, archiving and displaying data streams from sensors communicated via optical communication to better enable real-time anomaly detection and adaptive sampling capabilities using multiple UAS or other unmanned or manned systems.

  5. Coherent optical communication detection device based on modified balanced optical phase-locked loop

    Science.gov (United States)

    Zhang, Bo; Sun, Jianfeng; Xu, Mengmeng; Li, Guangyuan; Zhang, Guo; Lao, Chenzhe; He, Hongyu; Lu, Zhiyong

    2017-08-01

    In the field of satellite communication, space laser communication technology is famous for its high communication rate, good confidentiality, small size, low power consumption and so on. The design of coherent optical communication detection device based on modified balanced optical phase-locked loop (OPLL) is presented in the paper. It combined by local oscillator beam, modulator, voltage controlled oscillator, signal beam, optical filter, 180 degree hybrid, balanced detector, loop filter and signal receiver. Local oscillator beam and voltage controlled oscillator trace the phase variation of signal beam simultaneously. That taking the advantage of voltage controlled oscillator which responses sensitively and tunable local oscillator laser source with large tuning range can trace the phase variation of signal beam rapidly and achieve phase locking. The demand of the phase deviation is very low, and the system is easy to adjust. When the transmitter transmits the binary phase shift keying (BPSK) signal, the receiver can demodulate the baseband signal quickly, which has important significance for the free space coherent laser communication.

  6. Laser guide stars for optical free-space communications

    Science.gov (United States)

    Mata-Calvo, Ramon; Bonaccini Calia, Domenico; Barrios, Ricardo; Centrone, Mauro; Giggenbach, Dirk; Lombardi, Gianluca; Becker, Peter; Zayer, Igor

    2017-02-01

    The German Aerospace Center (DLR) and the European Southern Observatory (ESO) performed a measurement campaign together in April and July 2016 at Teide-Observatory (Tenerife), with the support of the European Space Agency (ESA), to investigate the use of laser guide stars (LGS) in ground to space optical communications. Atmospheric turbulence causes strong signal fluctuations in the uplink, due to scintillation and beam wander. In space communications, the use of the downlink channel as reference for pointing and for pre-distortion adaptive optics is limited by the size of the isokinetic and isoplanatic angle in relation to the required point-ahead angle. Pointing and phase errors due to the decorrelation between downward and upward beam due to the point-ahead angle may have a severe impact on the required transmit power and the stability of the communications link. LGSs provide a self-tailored reference to any optical ground-to-space link, independently of turbulence conditions and required point-ahead angle. In photon-starved links, typically in deep-space scenarios, LGSs allow dedicating all downlink received signal to communications purposes, increasing the available link margin. The scope of the joint DLR-ESO measurement campaign was, first, to measure the absolute value of the beam wander (uplink-tilt) using a LGS, taking a natural star as a reference, and, second, to characterize the decrease of correlation between uplink-tilt and downlink-tilt with respect to the angular separation between both sources. This paper describes the experiments performed during the measurement campaigns, providing an overview of the measured data and the first outcomes of the data post-processing.

  7. Design issues for semi-passive optical communication devices

    Science.gov (United States)

    Glaser, I.

    2007-09-01

    Optical smart cards are devices containing a retro-reflector, light modulator, and some computing and data storage capabilities to affect semi-passive communication. They do not produce light; instead they modulate and send back light received from a stationary unit. These devices can replace contact-based smart cards as well as RF based ones for applications ranging from identification to transmitting and validating data. Since their transmission is essentially focused on the receiving unit, they are harder to eavesdrop than RF devices, yet need no physical contact or alignment. In this paper we explore optical design issues of these devices and estimate their optical behavior. Specifically, we analyze how these compact devices can be optimized for selected application profiles. Some of the key parameters addressed are effective light efficiency (how much modulated signal can be received by the stationary unit given the amount of light it transmits), range of tilt angles (angle between device surface normal to the line connecting the optical smart card with the stationary unit) through which the device would be effective, and power requirements of the semi-passive unit. In addition, issues concerning compact packaging of this device are discussed. Finally, results of the analysis are employed to produce a comparison of achievable capabilities of these optical smart cards, as opposed to alternative devices, and discuss potential applications were they can be best utilized.

  8. Review of optical wireless communications for data centers

    Science.gov (United States)

    Arnon, Shlomi

    2017-10-01

    A data center (DC) is a facility either physical or virtual, for running applications, searching, storage, management and dissemination of information known as cloud computing, which consume a huge amount of energy. A DC includes thousands of servers, communication and storage equipment and a support system including an air conditioning system, security, monitoring equipment and electricity regulator units. Data center operators face the challenges of meeting exponentially increasing demands for network bandwidth without unreasonable increases in operation and infrastructure cost. In order to meet the requirements of moderate increase in operation and infrastructure cost technology, a revolution is required. One way to overcome the shortcomings of traditional static (wired) data center architectures is use of a hybrid network based on fiber and optical wireless communication (OWC) or free space optics (FSO). The OWC link could be deployed on top of the existing cable/fiber network layer, so that live migration could be done easily and dynamically. In that case the network topology is flexible and adapts quickly to changes in traffic, heat distribution, power consumption and characteristics of the applications. In addition, OWC could provide an easy way to maintain and scale up data centers. As a result total cost of ownership could be reduced and the return on investment could be increased. In this talk we will review the main OWC technologies applicable for data centers, indicate how energy could be saved using OWC multichannel communication and discuss the issue of OWC pointing accuracy for data center scenario.

  9. Nantenna for Standard 1550 nm Optical Communication Systems

    Directory of Open Access Journals (Sweden)

    Waleed Tariq Sethi

    2016-01-01

    Full Text Available Nanoscale transmission and reception technologies will play a vital role and be part of the next generation communication networks. This applies for all application fields including imaging, health, biosensing, civilian, and military communications. The detection of light frequency using nanooptical antennas may possibly become a good competitor to the semiconductor based photodetector because of the simplicity of integration, cost, and inherent capability to detect the phase and amplitude instead of power only. In this paper, authors propose simulated design of a hexagonal dielectric loaded nantenna (HDLN and explore its potential benefits at the standard optical C-band (1550 nm. The proposed nantenna consists of “Ag-SiO2-Ag” structure, consisting of “Si” hexagonal dielectric with equal lengths fed by “Ag” nanostrip transmission line. The simulated nantenna achieves an impedance bandwidth of 3.7% (190.9 THz–198.1 THz and a directivity of 8.6 dBi, at a center frequency of 193.5 THz, covering most of the ITU-T standard optical transmission window (C-band. The hexagonal dielectric nantenna produces HE20δ modes and the wave propagation is found to be end-fire. The efficiency of the nantenna is proven via numerical expressions, thus making the proposed design viable for nanonetwork communications.

  10. Monolithically integrated quantum dot optical modulator with semiconductor optical amplifier for thousand and original band optical communication

    Science.gov (United States)

    Yamamoto, Naokatsu; Akahane, Kouichi; Umezawa, Toshimasa; Matsumoto, Atsushi; Kawanishi, Tetsuya

    2016-04-01

    A monolithically integrated quantum dot (QD) optical gain modulator (OGM) with a QD semiconductor optical amplifier (SOA) was successfully developed with T-band (1.0 µm waveband) and O-band (1.3 µm waveband) QD optical gain materials for Gbps-order, high-speed optical data generation. The insertion loss due to coupling between the device and the optical fiber was effectively compensated for by the SOA section. It was also confirmed that the monolithic QD-OGM/SOA device enabled >4.8 Gbps optical data generation with a clear eye opening in the T-band. Furthermore, we successfully demonstrated error-free 4.8 Gbps optical data transmissions in each of the six wavelength channels over a 10-km-long photonic crystal fiber using the monolithic QD-OGM/SOA device in multiple O-band wavelength channels, which were generated by the single QD gain chip. These results suggest that the monolithic QD-OGM/SOA device will be advantageous in ultra-broadband optical frequency systems that utilize the T+O-band for short- and medium-range optical communications.

  11. Design and Implementation of Secure and Reliable Communication using Optical Wireless Communication

    Science.gov (United States)

    Saadi, Muhammad; Bajpai, Ambar; Zhao, Yan; Sangwongngam, Paramin; Wuttisittikulkij, Lunchakorn

    2014-11-01

    Wireless networking intensify the tractability in the home and office environment to connect the internet without wires but at the cost of risks associated with stealing the data or threat of loading malicious code with the intention of harming the network. In this paper, we proposed a novel method of establishing a secure and reliable communication link using optical wireless communication (OWC). For security, spatial diversity based transmission using two optical transmitters is used and the reliability in the link is achieved by a newly proposed method for the construction of structured parity check matrix for binary Low Density Parity Check (LDPC) codes. Experimental results show that a successful secure and reliable link between the transmitter and the receiver can be achieved by using the proposed novel technique.

  12. High Data Rate Optical Wireless Communications Based on Ultraviolet Band

    KAUST Repository

    Sun, Xiaobin

    2017-10-01

    Optical wireless communication systems based on ultraviolet (UV)-band has a lot inherent advantages, such as low background solar radiation, low device dark noise. Besides, it also has small restrictive requirements for PAT (pointing, acquisition, and tracking) because of its high atmospheric scattering with molecules and aerosols. And these advantages are driving people to explore and utilize UV band for constructing and implementing a high-data-rate, less PAT communication links, such as diffuse-line-of-sight links (diffuse-LOS) and non-line-of-sight (NLOS). The responsivity of the photodetector at UV range is far lower than that of visible range, high power UV transmitters which can be easily modulated are under investigation. These factors make it is hard to realize a high-data-rate diffuse-LOS or NLOS UV communication links. To achieve a UV link mentioned above with current devices and modulation schemes, this thesis presents some efficient modulation schemes and available devices for the time being. Besides, a demonstration of ultraviolet-B (UVB) communication link is implemented utilizing quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM). The demonstration is based on a 294-nm UVB-light-emitting-diode (UVB-LED) with a full-width at half-maximum (FWHM) of 9 nm, and according to the measured L-I-V curve, we set the bias voltage as 7V for maximum the ac amplitude and thus get a high signal-noise-ratio (SNR) channel, and the light output power is 190 μW with such bias voltage. Besides, there is a unique silica gel lens on top of the LED to concentrate the beam. A -3-dB bandwidth of 29 MHz was measured and a high-speed near-solar-blind communication link with a data rate of 71 Mbit/s was achieved using 8-QAM-OFDM at perfect alignment, and 23.6 Mbit/s using 2-QAM-OFDM when the angle subtended by the pointing direction of the UVB-LED and photodetector (PD) is 12 degrees, thus establishing a diffuse-line-of-sight (LOS) link

  13. InP on SOI devices for optical communication and optical network on chip

    Science.gov (United States)

    Fedeli, J.-M.; Ben Bakir, B.; Olivier, N.; Grosse, Ph.; Grenouillet, L.; Augendre, E.; Phillippe, P.; Gilbert, K.; Bordel, D.; Harduin, J.

    2011-01-01

    For about ten years, we have been developing InP on Si devices under different projects focusing first on μlasers then on semicompact lasers. For aiming the integration on a CMOS circuit and for thermal issue, we relied on SiO2 direct bonding of InP unpatterned materials. After the chemical removal of the InP substrate, the heterostructures lie on top of silicon waveguides of an SOI wafer with a separation of about 100nm. Different lasers or photodetectors have been achieved for off-chip optical communication and for intra-chip optical communication within an optical network. For high performance computing with high speed communication between cores, we developed InP microdisk lasers that are coupled to silicon waveguide and produced 100μW of optical power and that can be directly modulated up to 5G at different wavelengths. The optical network is based on wavelength selective circuits with ring resonators. InGaAs photodetectors are evanescently coupled to the silicon waveguide with an efficiency of 0.8A/W. The fabrication has been demonstrated at 200mm wafer scale in a microelectronics clean room for CMOS compatibility. For off-chip communication, silicon on InP evanescent laser have been realized with an innovative design where the cavity is defined in silicon and the gain localized in the QW of bonded InP hererostructure. The investigated devices operate at continuous wave regime with room temperature threshold current below 100 mA, the side mode suppression ratio is as high as 20dB, and the fibercoupled output power is {7mW. Direct modulation can be achieved with already 6G operation.

  14. Fast-steering solutions for cubesat-scale optical communications

    Science.gov (United States)

    Kingsbury, R. W.; Nguyen, T.; Riesing, K.; Cahoy, K.

    2017-11-01

    We describe the design of a compact free-space optical communications module for use on a nanosatellite and present results from a detailed trade study to select an optical fine steering mechanism compatible with our stringent size, weight and power (SWaP) constraints. This mechanism is an integral component of the compact free-space optical communications system that is under development at the MIT Space Systems Laboratory [1]. The overall goal of this project is to develop a laser communications (lasercom) payload that fits within the SWaP constraints of a typical ``3U'' CubeSat. The SWaP constraints for the entire lasercom payload are 5 cm × 10 cm × 10 cm, 600 g and 10W. Although other efforts are underway to qualify MEMS deformable mirrors for use in CubeSats [2], there has been very little work towards qualifying tip-tilt MEMS mirrors [3]. Sec. II provides additional information on how the fast steering mechanism is used in our lasercom system. Performance requirements and desirable traits of the mechanism are given. In Sec. III we describe the various types of compact tip-tilt mirrors that are commercially available as well as the justification for selecting a MEMS-based device for our application. Sec. IV presents an analysis of the device's transfer function characteristics and ways of predicting this behavior that are suitable for use in the control processor. This analysis is based upon manufacturer-provided test data which was collected at standard room conditions. In the final section, we describe on-going work to build a testbed that will be used to measure device performance in a thermal chamber.

  15. Application of spinal code for performance improvement in free-space optical communications

    Science.gov (United States)

    Saiki, Naoya; Okamoto, Eiji; Takenaka, Hideki; Toyoshima, Morio

    2017-09-01

    In recent years, the demand for high-capacity communication has grown, and fiber-optic transmission is being used in wired communications to meet this demand. Similarly, free-space optics (FSO), which is an optical wireless communication technology that uses laser light, has attracted much attention and has been considered as a suitable alternative to satisfy this demand in wireless communications. Free-space optical communication uses a hundred THz frequency band and allows for high-speed and radio-regulation free transmission, which may provide a solution for the current shortage of radio frequency bands.

  16. Some Protocols For Optical-Fiber Digital Communications

    Science.gov (United States)

    Yeh, Cavour; Gerla, Mario

    1989-01-01

    One works best in heavy traffic, another, in light traffic. Three protocols proposed for digital communications among stations connected by passive taps to pair of uni-directional optical-fiber buses. Mediate round-robin, bounded-delay access to buses by all stations and particularly suited to fast transmission. Partly because transmission medium passive (no relay stations) and partly because protocols distribute control of network among all stations with provision for addition and deletion of stations (no control stations), communication network able to resist and recover from failures. Implicit token propagates in one direction on one bus and in opposite direction on other bus, minimizing interval of silence between end of one round and beginning of next.

  17. Optical antenna for a visible light communications receiver

    Science.gov (United States)

    Valencia-Estrada, Juan Camilo; García-Márquez, Jorge; Topsu, Suat; Chassagne, Luc

    2018-01-01

    Visible Light Communications (VLC) receivers adapted to be used in high transmission rates will eventually use either, high aperture lenses or non-linear optical elements capable of converting light arriving to the receiver into an electric signal. The high aperture lens case, reveals a challenge from an optical designers point-of-view. As a matter of fact, the lens must collect a wide aperture intensity flux using a limited aperture as its use is intended to portable devices. This last also limits both, lens thickness and its focal length. Here, we show a first design to be adapted to a VLC receiver that take these constraints into account. This paper describes a method to design catadioptric and monolithic lenses to be used as an optical collector of light entering from a near point light source as a spherical fan L with a wide acceptance angle α° and high efficiency. These lenses can be mass produced and therefore one can find many practical applications in VLC equipped devices. We show a first design for a near light source without magnification, and second one with a detector's magnification in a meridional section. We utilize rigorous geometric optics, vector analysis and ordinary differential equations.

  18. Diversity Order Results for MIMO Optical Wireless Communications

    KAUST Repository

    Sapenov, Yerzhan; Chaaban, Anas; Rezki, Zouheir; Abdallah, Mohamed; Qaraqe, Khalid; Alouini, Mohamed-Slim

    2017-01-01

    An optical wireless multiple-input multiple-output (MIMO) communication system employing intensity-modulation direct-detection (IM/DD) is considered. The maximal diversity order of the channel is characterized by studying the outage probability. Then, spatial repetition coding (RC) is shown to be diversity-optimal as it achieves the channel’s maximal diversity order. This diversity order is given by a simple expression which is suitable for any channel statistics of practical interest. The results are specialized to some practical channel statistics, and numerical results are provided to verify the results.

  19. Diversity Order Results for MIMO Optical Wireless Communications

    KAUST Repository

    Sapenov, Yerzhan

    2017-09-21

    An optical wireless multiple-input multiple-output (MIMO) communication system employing intensity-modulation direct-detection (IM/DD) is considered. The maximal diversity order of the channel is characterized by studying the outage probability. Then, spatial repetition coding (RC) is shown to be diversity-optimal as it achieves the channel’s maximal diversity order. This diversity order is given by a simple expression which is suitable for any channel statistics of practical interest. The results are specialized to some practical channel statistics, and numerical results are provided to verify the results.

  20. Planets as background noise sources in free space optical communications

    Science.gov (United States)

    Katz, J.

    1986-01-01

    Background noise generated by planets is the dominant noise source in most deep space direct detection optical communications systems. Earlier approximate analyses of this problem are based on simplified blackbody calculations and can yield results that may be inaccurate by up to an order of magnitude. Various other factors that need to be taken into consideration, such as the phase angle and the actual spectral dependence of the planet albedo, in order to obtain a more accurate estimate of the noise magnitude are examined.

  1. Laser Communications and Fiber Optics Lab Manual. High-Technology Training Module.

    Science.gov (United States)

    Biddick, Robert

    This laboratory training manual on laser communications and fiber optics may be used in a general technology-communications course for ninth graders. Upon completion of this exercise, students achieve the following goals: match concepts with laser communication system parts; explain advantages of fiber optic cable over conventional copper wire;…

  2. The Big Information and Communication Groups in the World

    Directory of Open Access Journals (Sweden)

    José Rebelo

    2010-01-01

    Full Text Available The present article addresses the form major world information and communication groups operate, based on strategies of verticalisation of activities that encompass the distinct media segments – newspapers and magazines, television and radio – and stretch to the new technologies, namely telecommunications and Internet access services. Operating through a vertical system, these groups work as a network system by establishing association or merger agreements, protocols to strengthen their commercial relations, and through interpersonal connections. Their corresponding capitals tend to disperse and their ownership is constantly changing, particularly thanks to the involvement of pension funds, which do not disregard the opportunity of alienating property whenever the profit obtained justifies it.Both directly, thanks to the strength of their own products – “global products” that inundate the world market, and indirectly, through the influence they have on others around them, the leading information and communication groups are a decisive factor in the speeding up of the processes of naturalization, the fixing of stereotypes, and in putting on the agenda the topics that will cross through public space.It is undeniable that the advent and massive spread of the new technologies pose a serious threat to the homogenization and the media standardization carried out by the major groups. However, there are still issues that call for moderation when analyzing this issue. Firstly, the power public authorities still detain, especially in non-democratic countries, to interrupt the circulation of contents. Secondly, the attack launched by the large information and communication groups in order to occupy online space themselves. Thirdly, the excess of information flow and the difficulty associated with the need to select and verify.

  3. Handbook of fiber optic data communication a practical guide to optical networking

    CERN Document Server

    DeCusatis, Casimer

    2008-01-01

    The third edition of this Handbook provides a comprehensive, easy to use guide to the field of optical fiber data communications. Written by experts in the industry from major companies such as IBM, Cisco and Nortel, the Handbook is a key reference for optical fiber technology, networking, protocols, applications, manufacturing, and future directions. It includes chapters on all the major industry standards, written by the same experts who developed them.This edition contains new material on transceiver form factors (QSFP, SFP +, XFP, X2), manufacturing standards, including JEDEC and R

  4. The intergroup protocols: Scalable group communication for the internet

    Energy Technology Data Exchange (ETDEWEB)

    Berket, Karlo [Univ. of California, Santa Barbara, CA (United States)

    2000-12-04

    Reliable group ordered delivery of multicast messages in a distributed system is a useful service that simplifies the programming of distributed applications. Such a service helps to maintain the consistency of replicated information and to coordinate the activities of the various processes. With the increasing popularity of the Internet, there is an increasing interest in scaling the protocols that provide this service to the environment of the Internet. The InterGroup protocol suite, described in this dissertation, provides such a service, and is intended for the environment of the Internet with scalability to large numbers of nodes and high latency links. The InterGroup protocols approach the scalability problem from various directions. They redefine the meaning of group membership, allow voluntary membership changes, add a receiver-oriented selection of delivery guarantees that permits heterogeneity of the receiver set, and provide a scalable reliability service. The InterGroup system comprises several components, executing at various sites within the system. Each component provides part of the services necessary to implement a group communication system for the wide-area. The components can be categorized as: (1) control hierarchy, (2) reliable multicast, (3) message distribution and delivery, and (4) process group membership. We have implemented a prototype of the InterGroup protocols in Java, and have tested the system performance in both local-area and wide-area networks.

  5. Optical wireless communications to OC-768 and beyond

    Science.gov (United States)

    Medved, David B.; Davidovich, Leonid

    2001-10-01

    Laser and LED-based wireless communication systems are currently providing license-free interconnection for broadband voice, data and video transport. These systems allow for the immediate, reliable and low-cost extension of copper and fiber-based networks to any end user, providing efficient First Mile bypass access to high data rate backbone networks at speeds ranging from T-1 voice to full throughput ATM at 155 Mbps and up to Gigabit Ethernet. These wireless optical beams constitute a Virtual Fiber in the air, providing the capabilities of fiber in situations where wired connectivity is unavailable, impractical, expensive or slow-to-implement, while achieving a combination of low cost, speed and reliability that cannot be matched by microwave, mm wave, spread spectrum or other competing (actually complementary) wireless technologies. The carrier frequency of the optical beam is about 10,000 times higher than the highest frequencies used by the millimeter wave technology. By means of Wavelength Division Multiplexing more than 1000 independent data channels can be projected into the air on a single beam thus providing a potential bandwidth ten million times that of any RF solution. The twin barriers of physics and regulatory bureaucracy to this essentially infinite wireless bandwidth are thus eliminated by this Virtual Fiber. As user density and individual bandwidth needs escalate, the optical wireless will be the preferred medium of choice in both network and cellular interconnection. A mesh topology which integrates our optical wireless systems with the latest Optical Access switches and routing equipment will be described using case study examples from Japan to South America. As the Bandwidth Blowout continues to push the limits of electronics and especially in the case of DWDM (Dense Wavelength Division Multiples), the conventional optical wireless solutions are no longer feasible. Instead of using f.o. transceivers to convert photons to electrons and thence

  6. 'Group value foresight' - Treating the nuclear interest in IVO Group Communications

    International Nuclear Information System (INIS)

    Heininen-Ojanpera, Marke

    1999-01-01

    Fortum is a new international energy group formed through the combination of the IVO Group and the Neste Group, two Finnish industrial groups with extensive operations in the energy sector in the Nordic countries and certain other countries throughout the world. IVO Group uses almost all fuels to generate electricity: nuclear, hydro, gas, oil, coal, peat, biomass, municipal waste, wind and solar. The main capacity is generated by nuclear, coal and water but gas, particularly in cogeneration, has been expected to grow. The major challenge in communicating is to find a balanced way of dealing with this variety so that the messages will be open and objective and, at the same time, not harming unnecessarily any of the generation forms in business terms. Moreover, new business procedures are welcome. The majority of the communicating issues deal with either competition or environmental questions under the threat of bad publicity and more strict regulatory controls. From the beginning, one of the working groups was responsible for defining the issues and sorting out the weak signals related to nuclear energy. In terms of corporate communications, special nuclear policies and messages have been worked out each year. For many reasons, the earlier nuclear policies and communication agendas have been unnecessarily strongly emphasising the nuclear option only. Today, the Group Value Foresight process, among others, has helped IVO to find the correct weighting of any nuclear issue and option in relation to other major forms of generation and related issues. The policies and messages have become more reasonable and more sensitive to changing situations in the market and in relation to public perception. There is less and less need for presenting the nuclear option in public with a quivering voice of offended authority

  7. Thin film technologies for optoelectronic components in fiber optic communication

    Science.gov (United States)

    Perinati, Agostino

    1998-02-01

    'The Asian Routes Towards the Global Information Society' and 'Towards a Strategic Planning for the Global Information Society' will be the forum themes of 'Asia Telecom 97' and 'Telecom Interactice 97' events respectively, to be held by the International Telecommunication Union (ITU) in order to further telecommunication development around the world. International telecommunications network affects our life by keeping us in touch, bringing us world news and underpinning the global economy. Global tele-economy, global information infrastructure, global information society terms are more and more used to indicate the evolution towards an information- driven world where the access to information, communication and technologies is essential to the economic and social development in every country. Telecommunication industry can strongly contribute to this evolution together with broadcasting and computer industry, and fiber optic communications are expected to continue to grow up and share a relevant part of the total telecom market. In 1995 telecom market shown a 3.8 percent worldwide investment growth reaching a 545 billion value. According to 'Kessler Marketing Intelligence (KMI) Corp.' analysis of fiberoptics and multimedia market the amount of cabled fiber installed in U.S. will be around 11 million fiber-km in 1997 and 15 million fiber-km are predicted in the year 2000. Between 1995 and 1998 the undersea industry is estimated to deal with 13.9 billion as additional undersea cable systems investment in the global telecom network. In China beside satellite telecom stations and digital microwave systems 22 fiber optic backbones have been realized and another 23 systems are expected to be built in the Ninth Five-Year National Plan (1996 to approximately 2000) with a total length of nearly 30,000 sheat-km. The study, Fiber and Fiberoptic Cable Markets in China, recently released by KMI Corp. shows that fiber optic cable installation by MPT and other network operators

  8. Self-Homodyne Detection in Optical Communication Systems

    Directory of Open Access Journals (Sweden)

    Benjamin J. Puttnam

    2014-05-01

    Full Text Available We review work on self-homodyne detection (SHD for optical communication systems. SHD uses a transmitted pilot-tone (PT, originating from the transmitter laser, to exploit phase noise cancellation at a coherent receiver and to enable transmitter linewidth tolerance and potential energy savings. We give an overview of SHD performance, outlining the key contributors to the optical signal-to-noise ratio penalty compared to equivalent intradyne systems, and summarize the advantages, differences and similarities between schemes using polarization-division multiplexed PTs (PDM-SHD and those using space-division multiplexed PTs (SDM-SHD. For PDM-SHD, we review the extensive work on the transmission of advanced modulation formats and techniques to minimize the trade-off with spectral efficiency, as well as recent work on digital SHD, where the SHD receiver is combined with an polarization-diversity ID front-end receiver to provide both polarization and modulation format alignment. We then focus on SDM-SHD systems, describing experimental results using multi-core fibers (MCFs with up to 19 cores, including high capacity transmission with broad-linewidth lasers and experiments incorporating SDM-SHD in networking. Additionally, we discuss the requirement for polarization tracking of the PTs at the receiver and path length alignment and review some variants of SHD before outlining the future challenges of self-homodyne optical transmission and gaps in current knowledge.

  9. Simulation of autosoliton optical pulses in high-speed fibreoptic communication systems

    International Nuclear Information System (INIS)

    Latkin, A I

    2005-01-01

    The propagation of a pulse in a fibreoptic communication link with periodically included regenerators - nonlinear optical loop mirrors, is studied. The autosoliton propagation regime of the optical pulse is revealed. It is shown that the inclusion of a ring mirror to the communication link leads to a substantial increase in the transmission distance of the pulse at a small negative average dispersion in the link. (optical communication)

  10. Electro-optical design for efficient visual communication

    Science.gov (United States)

    Huck, Friedrich O.; Fales, Carl L.; Jobson, Daniel J.; Rahman, Zia-ur

    1995-03-01

    Visual communication, in the form of telephotography and television, for example, can be regarded as efficient only if the amount of information that it conveys about the scene to the observer approaches the maximum possible and the associated cost approaches the minimum possible. Elsewhere we have addressed the problem of assessing the end-to-end performance of visual communication systems in terms of their efficiency in this sense by integrating the critical limiting factors that constrain image gathering into classical communication theory. We use this approach to assess the electro-optical design of image-gathering devices as a function of the f number and apodization of the objective lens and the aperture size and sampling geometry of the photodetection mechanism. Results show that an image-gathering device that is designed to optimize information capacity performs similarly to the human eye. For both, the performance approaches the maximum possible, in terms of the efficiency with which the acquired information can be transmitted as decorrelated data, and the fidelity, sharpness, and clarity with which fine detail can be restored.

  11. Trained neurons-based motion detection in optical camera communications

    Science.gov (United States)

    Teli, Shivani; Cahyadi, Willy Anugrah; Chung, Yeon Ho

    2018-04-01

    A concept of trained neurons-based motion detection (TNMD) in optical camera communications (OCC) is proposed. The proposed TNMD is based on neurons present in a neural network that perform repetitive analysis in order to provide efficient and reliable motion detection in OCC. This efficient motion detection can be considered another functionality of OCC in addition to two traditional functionalities of illumination and communication. To verify the proposed TNMD, the experiments were conducted in an indoor static downlink OCC, where a mobile phone front camera is employed as the receiver and an 8 × 8 red, green, and blue (RGB) light-emitting diode array as the transmitter. The motion is detected by observing the user's finger movement in the form of centroid through the OCC link via a camera. Unlike conventional trained neurons approaches, the proposed TNMD is trained not with motion itself but with centroid data samples, thus providing more accurate detection and far less complex detection algorithm. The experiment results demonstrate that the TNMD can detect all considered motions accurately with acceptable bit error rate (BER) performances at a transmission distance of up to 175 cm. In addition, while the TNMD is performed, a maximum data rate of 3.759 kbps over the OCC link is obtained. The OCC with the proposed TNMD combined can be considered an efficient indoor OCC system that provides illumination, communication, and motion detection in a convenient smart home environment.

  12. Electro-Optical Design for Efficient Visual Communication

    Science.gov (United States)

    Huck, Friedrich O.; Fales, Carl L.; Jobson, Daniel J.; Rahman, Zia-Ur

    1995-01-01

    Visual communication, in the form of telephotography and television, for example, can be regarded as efficient only if the amount of information that it conveys about the scene to the observer approaches the maximum possible and the associated cost approaches the minimum possible. Elsewhere we have addressed the problem of assessing the end to end performance of visual communication systems in terms of their efficiency in this sense by integrating the critical limiting factors that constrain image gathering into classical communications theory. We use this approach to assess the electro-optical design of image gathering devices as a function of the f number and apodization of the objective lens and the aperture size and sampling geometry of the phot-detection mechanism. Results show that an image gathering device that is designed to optimize information capacity performs similarly to the human eye. For both, the performance approaches the maximum possible, in terms of the efficiency with which the acquired information can be transmitted as decorrelated data, and the fidelity, sharpness, and clearity with which fine detail can be restored.

  13. Efficient Weibull channel model for salinity induced turbulent underwater wireless optical communications

    KAUST Repository

    Oubei, Hassan M.; Zedini, Emna; Elafandy, Rami T.; Kammoun, Abla; Ng, Tien Khee; Alouini, Mohamed-Slim; Ooi, Boon S.

    2017-01-01

    Recent advances in underwater wireless optical communications necessitate a better understanding of the underwater channel. We propose the Weibull model to characterize the fading of salinity induced turbulent underwater wireless optical channels

  14. Automatic modulation format recognition for the next generation optical communication networks using artificial neural networks

    Science.gov (United States)

    Guesmi, Latifa; Hraghi, Abir; Menif, Mourad

    2015-03-01

    A new technique for Automatic Modulation Format Recognition (AMFR) in next generation optical communication networks is presented. This technique uses the Artificial Neural Network (ANN) in conjunction with the features of Linear Optical Sampling (LOS) of the detected signal at high bit rates using direct detection or coherent detection. The use of LOS method for this purpose mainly driven by the increase of bit rates which enables the measurement of eye diagrams. The efficiency of this technique is demonstrated under different transmission impairments such as chromatic dispersion (CD) in the range of -500 to 500 ps/nm, differential group delay (DGD) in the range of 0-15 ps and the optical signal tonoise ratio (OSNR) in the range of 10-30 dB. The results of numerical simulation for various modulation formats demonstrate successful recognition from a known bit rates with a higher estimation accuracy, which exceeds 99.8%.

  15. de Sitter group as a symmetry for optical decoherence

    International Nuclear Information System (INIS)

    Baskal, S; Kim, Y S

    2006-01-01

    Stokes parameters form a Minkowskian 4-vector under various optical transformations. As a consequence, the resulting two-by-two density matrix constitutes a representation of the Lorentz group. The associated Poincare sphere is a geometric representation of the Lorentz group. Since the Lorentz group preserves the determinant of the density matrix, it cannot accommodate the decoherence process through the decaying off-diagonal elements of the density matrix, which yields to an increase in the value of the determinant. It is noted that the O(3, 2) de Sitter group contains two Lorentz subgroups. The change in the determinant in one Lorentz group can be compensated by the other. It is thus possible to describe the decoherence process as a symmetry transformation in the O(3, 2) space. It is shown also that these two coupled Lorentz groups can serve as a concrete example of Feynman's rest of the universe

  16. Detailed temporal structure of communication networks in groups of songbirds.

    Science.gov (United States)

    Stowell, Dan; Gill, Lisa; Clayton, David

    2016-06-01

    Animals in groups often exchange calls, in patterns whose temporal structure may be influenced by contextual factors such as physical location and the social network structure of the group. We introduce a model-based analysis for temporal patterns of animal call timing, originally developed for networks of firing neurons. This has advantages over cross-correlation analysis in that it can correctly handle common-cause confounds and provides a generative model of call patterns with explicit parameters for the influences between individuals. It also has advantages over standard Markovian analysis in that it incorporates detailed temporal interactions which affect timing as well as sequencing of calls. Further, a fitted model can be used to generate novel synthetic call sequences. We apply the method to calls recorded from groups of domesticated zebra finch (Taeniopygia guttata) individuals. We find that the communication network in these groups has stable structure that persists from one day to the next, and that 'kernels' reflecting the temporal range of influence have a characteristic structure for a calling individual's effect on itself, its partner and on others in the group. We further find characteristic patterns of influences by call type as well as by individual. © 2016 The Authors.

  17. 75 FR 49527 - Caps Visual Communications, LLC; Black Dot Group; Formerly Known as Caps Group Acquisition, LLC...

    Science.gov (United States)

    2010-08-13

    ... DEPARTMENT OF LABOR Employment and Training Administration [TA-W-74,195] Caps Visual Communications, LLC; Black Dot Group; Formerly Known as Caps Group Acquisition, LLC Chicago, IL; Amended... of Caps Visual Communications, LLC, Black Dot Group, formerly known as Caps Group Acquisition, LLC...

  18. Optical performance monitoring in high-speed optical fiber communication systems

    Science.gov (United States)

    Yu, Changyuan; Yang, Jing; Hu, Junhao; Zhang, Banghong

    2011-11-01

    Optical performance monitoring (OPM) becomes an attractive topic as the rapid growth of data rate in optical communication networks. It provides improved operation of the high capacity optical transmission systems. Among the various impairments, chromatic dispersion (CD) is one of major factors limiting the transmission distance in high-speed communication systems. Polarization-mode dispersion (PMD) also becomes a degrading effect in the system with data rate larger than 40 Gbit/s. In this paper, we summarize several CD and PMD monitoring methods based on RF spectrum analysis and delay-tap sampling. By using a narrow band fiber Bragg grating (FBG) notch filter, centered at 10 GHz away from the optical carrier, 10-GHz RF power can be used as a CD-insensitive PMD monitoring signal. By taking the 10-GHz RF power ratio of non-filtered and filtered signal, PMD-insensitive CD monitoring can be achieved. If the FBG notch filter is placed at optical carrier, the RF clock power ratio between non-filtered and filtered signal is also a PMDinsensitive CD monitoring parameter, which has larger RF power dynamic range and better measurement resolution. Both simulation and experiment results show that the proposed methods are efficient on measuring CD and PMD values in 57-Gbit/s D8PSK systems. Delay-tap sampling is another efficient method of measuring residual CD. Amplitude ratio of asynchronous delay-tap sampling plot decreases with CD monotonously, and the amplitude ratio can be obtained by using low bandwidth balanced receiver. The simulated results show that our method is efficient on residual CD measurement in 50-Gbit/s 50% RZ DQPSK systems with a 12-GHz balanced receiver. Since no modification on the transmitter or receiver is required, the proposed scheme is simple and cost effective.

  19. Possible existence of optical communication channels in the brain

    Science.gov (United States)

    Kumar, Sourabh; Boone, Kristine; Tuszyński, Jack; Barclay, Paul; Simon, Christoph

    2016-11-01

    Given that many fundamental questions in neuroscience are still open, it seems pertinent to explore whether the brain might use other physical modalities than the ones that have been discovered so far. In particular it is well established that neurons can emit photons, which prompts the question whether these biophotons could serve as signals between neurons, in addition to the well-known electro-chemical signals. For such communication to be targeted, the photons would need to travel in waveguides. Here we show, based on detailed theoretical modeling, that myelinated axons could serve as photonic waveguides, taking into account realistic optical imperfections. We propose experiments, both in vivo and in vitro, to test our hypothesis. We discuss the implications of our results, including the question whether photons could mediate long-range quantum entanglement in the brain.

  20. Experimental demonstration of MIMO-OFDM underwater wireless optical communication

    Science.gov (United States)

    Song, Yuhang; Lu, Weichao; Sun, Bin; Hong, Yang; Qu, Fengzhong; Han, Jun; Zhang, Wei; Xu, Jing

    2017-11-01

    In this paper, we propose and experimentally demonstrate a multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) underwater wireless optical communication (UWOC) system, with a gross bit rate of 33.691 Mb/s over a 2-m water channel using low-cost blue light-emitting-diodes (LEDs) and 10-MHz PIN photodiodes. The system is capable of realizing robust data transmission within a relatively large reception area, leading to relaxed alignment requirement for UWOC. In addition, we have compared the system performance of repetition coding OFDM (RC-OFDM), Alamouti-OFDM and multiple-input single-output OFDM (MISO-OFDM) in turbid water. Results show that the Alamouti-OFDM UWOC is more resistant to delay than the RC-OFDM-based system.

  1. Optical soliton communication using ultra-short pulses

    CERN Document Server

    Sadegh Amiri, Iraj

    2015-01-01

    This brief analyzes the characteristics of a microring resonator (MRR) to perform communication using ultra-short soliton pulses. The raising of nonlinear refractive indices, coupling coefficients and radius of the single microring resonator leads to decrease in input power and round trips wherein the bifurcation occurs. As a result, bifurcation or chaos behaviors are seen at lower input power of 44 W, where the nonlinear refractive index is n2=3.2×10−20 m2/W. Using a decimal convertor system, these ultra-short signals can be converted into quantum information. Results show that multi solitons with FWHM and FSR of 10 pm and 600 pm can be generated respectively. The multi optical soliton with FWHM and FSR of 325 pm and 880 nm can be incorporated with a time division multiple access (TDMA) system wherein the transportation of quantum information is performed.

  2. Data transmission with twisted light through a free-space to fiber optical communication link

    International Nuclear Information System (INIS)

    Brüning, Robert; Duparré, Michael; Ndagano, Bienvenu; McLaren, Melanie; Forbes, Andrew; Schröter, Siegmund; Kobelke, Jens

    2016-01-01

    Mode division multiplexing (MDM), where information is transmitted in the spatial modes of light, is mooted as a future technology with which to transmit large bits of information. However, one of the key issues in optical communication lies in connecting free-space to optical fiber networks, otherwise known as the ‘last mile’ problem. This is particularly problematic for MDM as the eigenmodes of free-space and fibers are in general not the same. Here we demonstrate a data transmission scheme across a free-space and fiber link using twisted light in the form of Laguerre–Gaussian (LG) azimuthal modes. As a proof-of-principle we design and implement a custom fiber where the supported LG modes can be grouped into five non-degenerate sets, and successfully transmit a gray-scale image across the composite link using one mode from each group, thereby ensuring minimal crosstalk. (letter)

  3. Emotions facilitate the communication of ambiguous group memberships.

    Science.gov (United States)

    Tskhay, Konstantin O; Rule, Nicholas O

    2015-12-01

    It is well known that emotions intersect with obvious social categories (e.g., race), influencing both how targets are categorized and the emotions that are read from their faces. Here, we examined the influence of emotional expression on the perception of less obvious group memberships for which, in the absence of obvious and stable physical markers, emotion may serve as a major avenue for group categorization and identification. Specifically, we examined whether emotions are embedded in the mental representations of sexual orientation and political affiliation, and whether people may use emotional expressions to communicate these group memberships to others. Using reverse correlation methods, we found that mental representations of gay and liberal faces were characterized by more positive facial expressions than mental representations of straight and conservative faces (Study 1). Furthermore, participants were evaluated as expressing more positive emotions when enacting self-defined "gay" and "liberal" versus "straight" and "conservative" facial expressions in the lab (Study 2). In addition, neutral faces morphed with happiness were perceived as more gay than when morphed with anger, and when compared to unmorphed controls (Study 3). Finally, we found that affect facilitated perceptions of sexual orientation and political affiliation in naturalistic settings (Study 4). Together, these studies suggest that emotion is a defining characteristic of person construal that people tend to use both when signaling their group memberships and when receiving those signals to categorize others. (c) 2015 APA, all rights reserved).

  4. Communicating about overdiagnosis: Learning from community focus groups on osteoporosis.

    Directory of Open Access Journals (Sweden)

    Ray Moynihan

    Full Text Available Overdiagnosis is considered a risk associated with the diagnosis of osteoporosis-as many people diagnosed won't experience harm from the condition. As yet there's little evidence on community understanding of overdiagnosis outside cancer- where it is an established risk of some screening programs-or effective ways to communicate about it. We examined community understanding around overdiagnosis of osteoporosis, to optimise communication strategies about this problem.Using a qualitative design we recruited a community sample of women, 50-80 years, from the Gold Coast community around Bond University, Australia, using random digit dialing, and conducted 5 focus groups with 41 women. A discussion guide and 4-part presentation were developed and piloted, with independent review from a consumer and clinical experts. Initial discussion had 4 segments: osteoporosis; bone density vs. other risk factors; medication; and overdiagnosis. The second half included the 4 short presentations and discussions on each. Analysis used Framework Analysis method. Initially participants described osteoporosis as bone degeneration causing some fear, demonstrated imprecise understanding of overdiagnosis, had a view osteoporosis couldn't be overdiagnosed as bone scans provided "clear cut" results, expressed belief in early diagnosis, and interest in prevention strategies enabling control. Following presentations, participants expressed some understanding of overdiagnosis, preference for describing osteoporosis as a "risk factor" not "disease", concern about a poor risk-benefit ratio for medications, and surprise and unease the definition of osteoporosis decided bone density of young women was "normal", without age adjustment. Limitations include English-speaking backgrounds of the sample and complex materials.Our findings suggest a gap between community expectations and how experts sometimes arbitrarily set low diagnostic thresholds which label those at risk as "diseased

  5. Optimal training sequences for indoor wireless optical communications

    International Nuclear Information System (INIS)

    Wang, Jun-Bo; Jiao, Yuan; Song, Xiaoyu; Chen, Ming

    2012-01-01

    Since indoor wireless optical communication (WOC) systems can offer several potential advantages over their radio frequency counterparts, there has been a growing interest in indoor WOC systems. Influenced by the complicated optical propagation environment, there exist multipath propagation phenomena. In order to eliminate the effect of multipath propagation, much attention should be concentrated on the channel estimation in indoor WOC systems. This paper investigates optimal training sequences (TSs) for estimating a channel impulse response in indoor WOC systems. Based on the Cramer–Rao bound (CRB) theorem, an explicit form of search criterion is found. Optimum TSs are obtained and tabulated by computer search for different channel responses and TS lengths. Measured by mean square error (MSE) performance, channel estimation errors are also investigated. Simulation results show that the MSE of the channel estimator at the receiver can be reduced significantly by using the optimized TS set. Moreover, the longer the TS, the better the MSE performance that can be obtained when the channel order is fixed. (paper)

  6. Dust Effect on The Performance of Optical Wireless Communication System

    Directory of Open Access Journals (Sweden)

    Fadel Abdul-Zahra Murad

    2017-11-01

    Full Text Available In this paper wireless optical communication system (FSO is designed through the use of software (Optisystem . The paper also study  the effect of atmospheric dust on the performance of communication system (FSO, the effect of dust concentration on the visibility by taking a different concentrations of dust (9, 20, 40, 60, 80 100, 120 gm / month / m2 . The effect of the visibility on the attenuation of dust concentration on each of these concentrations , and calculate attenuation of dust for the  wavelengths  (784 nm, 1550 nm. The Paper also deals with effect of the transmitted laser  power on the transmitter range (propagation distance where five different values of transmitted laser power (10mw, 20mw, 30mw, 40mw, 50mw are taken  and the study calculates the maximum transmitter range of  each value of the transmitted power under the influence of attenuation atmospheric dust concentrations for each concentration of dust used and also for the two wavelengths (1550nm, 784nm.

  7. Biomimetric sentinel reef structures for optical sensing and communications

    Science.gov (United States)

    Fries, David; Hutcheson, Tim; Josef, Noam; Millie, David; Tate, Connor

    2017-05-01

    Traditional artificial reef structures are designed with uniform cellular architectures and topologies and do not mimic natural reef forms. Strings and ropes are a proven, common fisheries and mariculture construction element throughout the world and using them as artificial reef scaffolding can enable a diversity of ocean sensing, communications systems including the goal of sentinel reefs. The architecture and packaging of electronics is key to enabling such structures and systems. The distributed sensor reef concept leads toward a demonstrable science-engineering-informed framework for 3D smart habitat designs critical to stock fish development and coastal monitoring and protection. These `nature-inspired' reef infrastructures, can enable novel instrumented `reef observatories' capable of collecting real-time ecosystem data. Embedding lighting and electronic elements into artificial reef systems are the first systems conceptualized. This approach of bringing spatial light to the underwater world for optical sensing, communication and even a new breed of underwater robotic vehicle is an interdisciplinary research activity which integrates principles of electronic packaging, and ocean technology with art/design.

  8. Fast QC-LDPC code for free space optical communication

    Science.gov (United States)

    Wang, Jin; Zhang, Qi; Udeh, Chinonso Paschal; Wu, Rangzhong

    2017-02-01

    Free Space Optical (FSO) Communication systems use the atmosphere as a propagation medium. Hence the atmospheric turbulence effects lead to multiplicative noise related with signal intensity. In order to suppress the signal fading induced by multiplicative noise, we propose a fast Quasi-Cyclic (QC) Low-Density Parity-Check (LDPC) code for FSO Communication systems. As a linear block code based on sparse matrix, the performances of QC-LDPC is extremely near to the Shannon limit. Currently, the studies on LDPC code in FSO Communications is mainly focused on Gauss-channel and Rayleigh-channel, respectively. In this study, the LDPC code design over atmospheric turbulence channel which is nether Gauss-channel nor Rayleigh-channel is closer to the practical situation. Based on the characteristics of atmospheric channel, which is modeled as logarithmic-normal distribution and K-distribution, we designed a special QC-LDPC code, and deduced the log-likelihood ratio (LLR). An irregular QC-LDPC code for fast coding, of which the rates are variable, is proposed in this paper. The proposed code achieves excellent performance of LDPC codes and can present the characteristics of high efficiency in low rate, stable in high rate and less number of iteration. The result of belief propagation (BP) decoding shows that the bit error rate (BER) obviously reduced as the Signal-to-Noise Ratio (SNR) increased. Therefore, the LDPC channel coding technology can effectively improve the performance of FSO. At the same time, the BER, after decoding reduces with the increase of SNR arbitrarily, and not having error limitation platform phenomenon with error rate slowing down.

  9. Optical Fiber Assemblies for Space Flight from the NASA Goddard Space Flight Center, Photonics Group

    Science.gov (United States)

    Ott, Melanie N.; Thoma, William Joe; LaRocca, Frank; Chuska, Richard; Switzer, Robert; Day, Lance

    2009-01-01

    The Photonics Group at NASA Goddard Space Flight Center in the Electrical Engineering Division of the Advanced Engineering and Technologies Directorate has been involved in the design, development, characterization, qualification, manufacturing, integration and anomaly analysis of optical fiber subsystems for over a decade. The group supports a variety of instrumentation across NASA and outside entities that build flight systems. Among the projects currently supported are: The Lunar Reconnaissance Orbiter, the Mars Science Laboratory, the James Webb Space Telescope, the Express Logistics Carrier for the International Space Station and the NASA Electronic Parts. and Packaging Program. A collection of the most pertinent information gathered during project support over the past year in regards to space flight performance of optical fiber components is presented here. The objective is to provide guidance for future space flight designs of instrumentation and communication systems.

  10. BER Performance of Stratified ACO-OFDM for Optical Wireless Communications over Multipath Channel

    OpenAIRE

    Gebeyehu, Zelalem Hailu; Langat, Philip Kibet; Maina, Ciira Wa

    2018-01-01

    In intensity modulation/direct detection- (IM/DD-) based optical OFDM systems, the requirement of the input signal to be real and positive unipolar imposes a reduction of system performances. Among previously proposed unipolar optical OFDM schemes for optical wireless communications (OWC), asymmetrically clipped optical OFDM (ACO-OFDM) and direct current biased optical OFDM (DCO-OFDM) are the most accepted ones. But those proposed schemes experience either spectral efficiency loss or energy e...

  11. A COTS RF/Optical Software Defined Radio for the Integrated Radio and Optical Communications Test Bed

    Science.gov (United States)

    Nappier, Jennifer M.; Zeleznikar, Daniel J.; Wroblewski, Adam C.; Tokars, Roger P.; Schoenholz, Bryan L.; Lantz, Nicholas C.

    2017-01-01

    The Integrated Radio and Optical Communications (iROC) project at the National Aeronautics and Space Administration (NASA) is investigating the merits of a hybrid radio frequency (RF) and optical communication system for deep space missions. In an effort to demonstrate the feasibility and advantages of a hybrid RF/Optical software defined radio (SDR), a laboratory prototype was assembled from primarily commercial-off-the-shelf (COTS) hardware components. This COTS platform has been used to demonstrate simultaneous transmission of the radio and optical communications waveforms through to the physical layer (telescope and antenna). This paper details the hardware and software used in the platform and various measures of its performance. A laboratory optical receiver platform has also been assembled in order to demonstrate hybrid free space links in combination with the transmitter.

  12. Research of the self-healing technologies in the optical communication network of distribution automation

    Science.gov (United States)

    Wang, Hao; Zhong, Guoxin

    2018-03-01

    Optical communication network is the mainstream technique of the communication networks for distribution automation, and self-healing technologies can improve the in reliability of the optical communication networks significantly. This paper discussed the technical characteristics and application scenarios of several network self-healing technologies in the access layer, the backbone layer and the core layer of the optical communication networks for distribution automation. On the base of the contrastive analysis, this paper gives an application suggestion of these self-healing technologies.

  13. PMD compensation in fiber-optic communication systems with direct detection using LDPC-coded OFDM.

    Science.gov (United States)

    Djordjevic, Ivan B

    2007-04-02

    The possibility of polarization-mode dispersion (PMD) compensation in fiber-optic communication systems with direct detection using a simple channel estimation technique and low-density parity-check (LDPC)-coded orthogonal frequency division multiplexing (OFDM) is demonstrated. It is shown that even for differential group delay (DGD) of 4/BW (BW is the OFDM signal bandwidth), the degradation due to the first-order PMD can be completely compensated for. Two classes of LDPC codes designed based on two different combinatorial objects (difference systems and product of combinatorial designs) suitable for use in PMD compensation are introduced.

  14. Smart Video Communication for Social Groups - The Vconect Project

    NARCIS (Netherlands)

    M. Ursu; P. Stollenmayer; D. Williams; P. Torres; P.S. Cesar Garcia (Pablo Santiago); N. Farber; E. Geelhoed

    2014-01-01

    htmlabstractThis article introduces the Vconect project. Vconect (Video Communications for Networked Communities) is a collaborative European research and development project dealing with high-quality enriched video as a medium for mass communication within social communities. The technical

  15. The real symplectic groups quantum mechanics and optics

    International Nuclear Information System (INIS)

    Arvind; Mukunda, N.

    1995-01-01

    We present a utilitarian review of the family of matrix groups Sp(2n,R), in a form suited to various applications both in optics and quantum mechanics. We contrast these groups and their geometry with the much more familiar Euclidean and unitary geometries. Both the properties of finite group elements and of the Lie algebra are studied, and special attention is paid to the so-called unitary metaplectic representation of Sp(2n,R). Global decomposition theorems, interesting subgroups and their generators are described. Turning to n-mode quantum systems, we define and study their variance matrices in general states, the implications of the Heisenberg uncertainty principles, and developed a U(n)-invariant squeezing criterion. The particular properties of Wigner distributions and Gaussian pure state wavefunctions under Sp(2n,R) action are delineated. (author). 22 refs

  16. Spectral space-time coding for optical communications through a multimode fiber

    NARCIS (Netherlands)

    Alonso, A.; Berghmans, F.; Thienpont, H.; Danckaert, J.; Desmet, L.

    2001-01-01

    We propose a method for coding the mode structure of a multimode optical fiber by spectral coding mixed with space-time modulation. With this system we can improve the data carrying capacity of a multimode fiber for optical communications and optical interconnects, and encode and decode the

  17. A cost-performance model for ground-based optical communications receiving telescopes

    Science.gov (United States)

    Lesh, J. R.; Robinson, D. L.

    1986-01-01

    An analytical cost-performance model for a ground-based optical communications receiving telescope is presented. The model considers costs of existing telescopes as a function of diameter and field of view. This, coupled with communication performance as a function of receiver diameter and field of view, yields the appropriate telescope cost versus communication performance curve.

  18. Analysis of large optical ground stations for deep-space optical communications

    Science.gov (United States)

    Garcia-Talavera, M. Reyes; Rivera, C.; Murga, G.; Montilla, I.; Alonso, A.

    2017-11-01

    Inter-satellite and ground to satellite optical communications have been successfully demonstrated over more than a decade with several experiments, the most recent being NASA's lunar mission Lunar Atmospheric Dust Environment Explorer (LADEE). The technology is in a mature stage that allows to consider optical communications as a high-capacity solution for future deep-space communications [1][2], where there is an increasing demand on downlink data rate to improve science return. To serve these deep-space missions, suitable optical ground stations (OGS) have to be developed providing large collecting areas. The design of such OGSs must face both technical and cost constraints in order to achieve an optimum implementation. To that end, different approaches have already been proposed and analyzed, namely, a large telescope based on a segmented primary mirror, telescope arrays, and even the combination of RF and optical receivers in modified versions of existing Deep-Space Network (DSN) antennas [3][4][5]. Array architectures have been proposed to relax some requirements, acting as one of the key drivers of the present study. The advantages offered by the array approach are attained at the expense of adding subsystems. Critical issues identified for each implementation include their inherent efficiency and losses, as well as its performance under high-background conditions, and the acquisition, pointing, tracking, and synchronization capabilities. It is worth noticing that, due to the photon-counting nature of detection, the system performance is not solely given by the signal-to-noise ratio parameter. To start with the analysis, first the main implications of the deep space scenarios are summarized, since they are the driving requirements to establish the technical specifications for the large OGS. Next, both the main characteristics of the OGS and the potential configuration approaches are presented, getting deeper in key subsystems with strong impact in the

  19. Quantum Limits of Space-to-Ground Optical Communications

    Science.gov (United States)

    Hemmati, H.; Dolinar, S.

    2012-01-01

    For a pure loss channel, the ultimate capacity can be achieved with classical coherent states (i.e., ideal laser light): (1) Capacity-achieving receiver (measurement) is yet to be determined. (2) Heterodyne detection approaches the ultimate capacity at high mean photon numbers. (3) Photon-counting approaches the ultimate capacity at low mean photon numbers. A number of current technology limits drive the achievable performance of free-space communication links. Approaching fundamental limits in the bandwidth-limited regime: (1) Heterodyne detection with high-order coherent-state modulation approaches ultimate limits. SOA improvements to laser phase noise, adaptive optics systems for atmospheric transmission would help. (2) High-order intensity modulation and photon-counting can approach heterodyne detection within approximately a factor of 2. This may have advantages over coherent detection in the presence of turbulence. Approaching fundamental limits in the photon-limited regime (1) Low-duty cycle binary coherent-state modulation (OOK, PPM) approaches ultimate limits. SOA improvements to laser extinction ratio, receiver dark noise, jitter, and blocking would help. (2) In some link geometries (near field links) number-state transmission could improve over coherent-state transmission

  20. Development of a Handheld Line Information Reader and Generator for Efficient Management of Optical Communication Lines.

    Science.gov (United States)

    Lee, Jaeyul; Kwon, Hyungwoo; Song, Jaewon; Jeon, Mansik; Kim, Jeehyun

    2017-08-24

    A handheld line information reader and a line information generator were developed for the efficient management of optical communication lines. The line information reader consists of a photo diode, trans-impedance amplifier, voltage amplifier, microcontroller unit, display panel, and communication modules. The line information generator consists of a laser diode, laser driving circuits, microcontroller unit, and communication modules. The line information reader can detect the optical radiation field of the test line by bending the optical fiber. To enhance the sensitivity of the line information reader, an additional lens was used with a focal length of 4.51 mm. Moreover, the simulation results obtained through BeamPROP ® software from Synopsys, Inc. demonstrated a stronger optical radiation field of the fiber due to a longer transmission wavelength and larger bending angle of the fiber. Therefore, the developed devices can be considered as useful tools for the efficient management of optical communication lines.

  1. A Trace-Driven Analysis of Wireless Group Communication Mechanisms

    Directory of Open Access Journals (Sweden)

    Surendar Chandra

    2012-08-01

    Full Text Available Wireless access is increasingly ubiquitous while mobile devices that use them are resource rich. These trends allow wireless users to collaborate with each other. We investigate various group communication paradigms that underly collaboration applications. We synthesize durations when members collaborate using wireless device availability traces. Wireless users operate from a variety of locations. Hence, we analyzed the behavior of wireless users in universities, corporations, conference venues, and city-wide hotspots. We show that the availability durations are longer in corporations followed by university and then in hotspots. The number of simultaneously available wireless users is small in all the scenarios. The session lengths are becoming smaller while the durations between sessions are becoming larger. We observed user churn in all the scenarios. We show that synchronous mechanisms require less effort to maintain update synchronicity among the group members. However, distributed mechanisms require a large number of replicas in order to propagate updates among the users. For asynchronous mechanisms, we show that pull-based mechanisms naturally randomize the times when updates are propagated and thus achieve better performance than push based mechanisms.We develop an adaptive approach that customizes the update frequency using the last session duration and show that this mechanism exhibits good performance when the required update frequency intervals are large. We also show that for a given number of gossips, it is preferable to propagate updates to all available nodes rather than increasing the frequency while correspondingly reducing the number of nodes to propagate updates.We develop a middleware to illustrate the practicality of our approach.

  2. Scheduling algorithm for data relay satellite optical communication based on artificial intelligent optimization

    Science.gov (United States)

    Zhao, Wei-hu; Zhao, Jing; Zhao, Shang-hong; Li, Yong-jun; Wang, Xiang; Dong, Yi; Dong, Chen

    2013-08-01

    Optical satellite communication with the advantages of broadband, large capacity and low power consuming broke the bottleneck of the traditional microwave satellite communication. The formation of the Space-based Information System with the technology of high performance optical inter-satellite communication and the realization of global seamless coverage and mobile terminal accessing are the necessary trend of the development of optical satellite communication. Considering the resources, missions and restraints of Data Relay Satellite Optical Communication System, a model of optical communication resources scheduling is established and a scheduling algorithm based on artificial intelligent optimization is put forwarded. According to the multi-relay-satellite, multi-user-satellite, multi-optical-antenna and multi-mission with several priority weights, the resources are scheduled reasonable by the operation: "Ascertain Current Mission Scheduling Time" and "Refresh Latter Mission Time-Window". The priority weight is considered as the parameter of the fitness function and the scheduling project is optimized by the Genetic Algorithm. The simulation scenarios including 3 relay satellites with 6 optical antennas, 12 user satellites and 30 missions, the simulation result reveals that the algorithm obtain satisfactory results in both efficiency and performance and resources scheduling model and the optimization algorithm are suitable in multi-relay-satellite, multi-user-satellite, and multi-optical-antenna recourses scheduling problem.

  3. The communication of "pure" group-based anger reduces tendencies toward intergroup conflict because it increases out-group empathy.

    Science.gov (United States)

    de Vos, Bart; van Zomeren, Martijn; Gordijn, Ernestine H; Postmes, Tom

    2013-08-01

    The communication of group-based anger in intergroup conflict is often associated with destructive conflict behavior. However, we show that communicating group-based anger toward the out-group can evoke empathy and thus reduce intergroup conflict. This is because it stresses the value of maintaining a positive long-term intergroup relationship, thereby increasing understanding for the situation (in contrast to the communication of the closely related emotion of contempt). Three experiments demonstrate that the communication of group-based anger indeed reduces destructive conflict intentions compared with (a) a control condition (Experiments 1-2), (b) the communication of group-based contempt (Experiment 2), and (c) the communication of a combination of group-based anger and contempt (Experiments 2-3). Moreover, results from all three experiments reveal that empathy mediated the positive effect of communicating "pure" group-based anger. We discuss the implications of these findings for the theory and practice of communicating emotions in intergroup conflicts.

  4. How Cultural Differences Affect Written and Oral Communication: The Case of Peer Response Groups.

    Science.gov (United States)

    Nelson, Gayle L.

    1997-01-01

    Peer response groups contribute to students' effectiveness as writers in any field, but cultural differences in communication affect interactions within the group. Culture-based dimensions on which communication may differ include individualism/collectivism, power distance, concept of "face," and communication style. Recommendations are…

  5. Secure communications of CAP-4 and OOK signals over MMF based on electro-optic chaos.

    Science.gov (United States)

    Ai, Jianzhou; Wang, Lulu; Wang, Jian

    2017-09-15

    Chaos-based secure communication can provide a high level of privacy in data transmission. Here, we experimentally demonstrate secure signal transmission over two kinds of multimode fiber (MMF) based on electro-optic intensity chaos. High-quality synchronization is achieved in an electro-optic feedback configuration. Both 5  Gbit/s carrier-less amplitude/phase (CAP-4) modulation and 10  Gbit/s on-off key (OOK) signals are recovered efficiently in electro-optic chaos-based communication systems. Degradations of chaos synchronization and communication system due to mismatch of various hardware keys are also discussed.

  6. Impact of Various Parameters on the Performance of Inter-aircraft Optical Wireless Communication Link

    Science.gov (United States)

    Singh, Mehtab

    2017-12-01

    Optical wireless communication (OWC) systems also known as Free space optics (FSO) are capable of providing high channel bandwidth, high data transmission rates, low power consumption, and high security. OWC links are being considered in different applications such as inter-satellite links, terrestrial links, and inter-aircraft communication links. This paper investigates the impact of different system parameters such as transmission power level, operating wavelength, transmitter pointing error angle, bit transmission rate, atmospheric attenuation, antenna aperture diameter, geometric losses, the responsivity of the photodetector, and link range on the performance of inter-aircraft optical wireless communication link.

  7. Multi-wavelength time-coincident optical communications system and methods thereof

    Science.gov (United States)

    Lekki, John (Inventor); Nguyen, Quang-Viet (Inventor)

    2009-01-01

    An optical communications transmitter includes a oscillator source, producing a clock signal, a data source, producing a data signal, a modulating circuit for modulating the clock signal using the data signal to produce modulating signals, optical drivers, receiving the modulating signals and producing optical driving signals based on the modulating signals and optical emitters, producing small numbers of photons based on the optical driving signals. The small numbers of photons are time-correlated between at least two separate optical transmission wavelengths and quantum states and the small number of photons can be detected by a receiver to reform the data signal.

  8. FAA and NASA UTM Research Transition Team: Communications and Navigation (CN) Working Group (WCG) Kickoff Meeting

    Science.gov (United States)

    Jung, Jaewoo; Larrow, Jarrett

    2017-01-01

    This is NASA FAA UTM Research Transition Team Communications and Navigation working group kick off meeting presentation that addresses the followings. Objectives overview Overall timeline and scope Outcomes and expectations Communication method and frequency of meetings Upcoming evaluation Next steps.

  9. Using Telestrations™ to Illustrate Small Group Communication Principles

    Science.gov (United States)

    Fedesco, Heather Noel

    2014-01-01

    This single class activity described here: (1) illustrates the importance of interdependence in groups; (2) can be used to measure group productivity and performance; (3) can encourage groups to engage in group learning; and (4) can facilitate group cohesion for newly formed groups. Students will be working in groups for the majority of their…

  10. Laser communication experiments between Sota and Meo optical ground station

    Science.gov (United States)

    Artaud, G.,; Issler, J.-L.; Védrenne, N.; Robert, C.; Petit, C.; Samain, E.; Phung, D.-H.; Maurice, N.; Toyoshima, M.; Kolev, D.

    2017-09-01

    Optical transmissions between earth and space have been identified as key technologies for future high data rate transmissions between satellites and ground. CNES is investigating the use of optics both for High data rate direct to Earth transfer from observation satellites in LEO, and for future telecommunications applications using optics for the high capacity Gateway link.

  11. A comparison of clinical communication skills between two groups of ...

    African Journals Online (AJOL)

    a comprehensive clinical model and a “golden thread” for communication skills in the ... sity, South Africa, based on the primary ..... Planning: shared decision making ... Explanation and planning. Incorporate clinical reasoning skills. Develop.

  12. The Interactive Dimension of Communication: The Pragmatics of the Palo Alto Group

    OpenAIRE

    Codruţa Porcar; Cristian Hainic

    2011-01-01

    Our paper proposes to analyze from a semiotic perspective the process of communication as conceived within the Palo Alto Group. We will firstly show that, as a result of the Group's critiques and revisions of the linear or mechanistic theories of communication, new perspectives are brought about for the essential axes of transformation within communication: we do not communicate as from a distinct atom to another, through an isolated channel, but through parts which are equal to the whole, th...

  13. Performance analysis of an adaptive optics system for free-space optics communication through atmospheric turbulence.

    Science.gov (United States)

    Wang, Yukun; Xu, Huanyu; Li, Dayu; Wang, Rui; Jin, Chengbin; Yin, Xianghui; Gao, Shijie; Mu, Quanquan; Xuan, Li; Cao, Zhaoliang

    2018-01-18

    The performance of free-space optics communication (FSOC) is greatly degraded by atmospheric turbulence. Adaptive optics (AO) is an effective method for attenuating the influence. In this paper, the influence of the spatial and temporal characteristics of turbulence on the performance of AO in a FSOC system is investigated. Based on the Greenwood frequency (GF) and the ratio of receiver aperture diameter to atmospheric coherent length (D/r 0 ), the relationship between FSOC performance (CE) and AO parameters (corrected Zernike modes number and bandwidth) is derived for the first time. Then, simulations and experiments are conducted to analyze the influence of AO parameters on FSOC performance under different GF and D/r 0 . The simulation and experimental results show that, for common turbulence conditions, the number of corrected Zernike modes can be fixed at 35 and the bandwidth of the AO system should be larger than the GF. Measurements of the bit error rate (BER) for moderate turbulence conditions (D/r 0  = 10, f G  = 60 Hz) show that when the bandwidth is two times that of GF, the average BER is decreased by two orders of magnitude compared with f G /f 3dB  = 1. These results and conclusions can provide important guidance in the design of an AO system for FSOC.

  14. Modeling and Performance Analysis of 10 Gbps Inter-satellite Optical Wireless Communication Link

    Science.gov (United States)

    Singh, Mehtab

    2017-12-01

    Free-space optical (FSO) communication has the advantages of two of the most predominant data transmission technologies - optical fiber communication and wireless communication. Most of the technical aspects of FSO are similar to that of optical fiber communication, with major difference in the information signal propagation medium which is free space in case of FSO rather than silica glass in optical fiber communication. One of the most important applications of FSO is inter-satellite optical wireless communication (IsOWC) links which will be deployed in the future in space. The IsOWC links have many advantages over the previously existing microwave satellite communication technologies such as higher bandwidth, lower power consumption, low cost of implementation, light size, and weight. In this paper, modeling and performance analysis of a 10-Gbps inter-satellite communication link with two satellites separated at a distance of 1,200 km has been done using OPTISYSTEM simulation software. Performance has been analyzed on the basis of quality factor, signal to noise ratio (SNR), and total power of the received signal.

  15. The effect of jitter on the performance of space coherent optical communication system with Costas loop

    Science.gov (United States)

    Li, Xin; Hong, Yifeng; Wang, Jinfang; Liu, Yang; Sun, Xun; Li, Mi

    2018-01-01

    Numerous communication techniques and optical devices successfully applied in space optical communication system indicates a good portability of it. With this good portability, typical coherent demodulation technique of Costas loop can be easily adopted in space optical communication system. As one of the components of pointing error, the effect of jitter plays an important role in the communication quality of such system. Here, we obtain the probability density functions (PDF) of different jitter degrees and explain their essential effect on the bit error rate (BER) space optical communication system. Also, under the effect of jitter, we research the bit error rate of space coherent optical communication system using Costas loop with different system parameters of transmission power, divergence angle, receiving diameter, avalanche photodiode (APD) gain, and phase deviation caused by Costas loop. Through a numerical simulation of this kind of communication system, we demonstrate the relationship between the BER and these system parameters, and some corresponding methods of system optimization are presented to enhance the communication quality.

  16. Characterization of the Marine Atmosphere for Free-Space Optical Communication

    National Research Council Canada - National Science Library

    Thomas, Linda M. Wasiczko; Moore, Christopher I; Burris, Harris R; Suite, Michele; Stell, Mena; Murphy, James; Gilbreath, G. C; Rabinovich, William; Scharpf, William

    2006-01-01

    The Chesapeake Bay Detachment of the Naval Research Laboratory (NRL-CBD) provides an ideal environment for characterizing the effects of the marine atmosphere on free space optical communication links...

  17. Near-Infrared Wireless Optical Communication with Particulates In-Suspension over the Underwater Channel

    KAUST Repository

    Lee, It Ee; Guo, Yong; Ng, Tien Khee; Park, Kihong; Alouini, Mohamed-Slim; Ooi, Boon S.

    2017-01-01

    We demonstrate a gigabit near-infrared-based underwater wireless optical communication link using an 808-nm laser diode to mitigate the particle scattering effect in turbid medium. An improvement in the error performance is observed with increasing

  18. 375-nm ultraviolet-laser based non-line-of-sight underwater optical communication

    KAUST Repository

    Sun, Xiaobin; Cai, Wenqi; Alkhazragi, Omar; Ooi, Ee-Ning; He, Hongsen; Chaaban, Anas; Shen, Chao; Oubei, Hassan M.; Khan, Mohammed Zahed Mustafa; Ng, Tien Khee; Alouini, Mohamed-Slim; Ooi, Boon S.

    2018-01-01

    For circumventing the alignment requirement of line-of-sight (LOS) underwater wireless optical communication (UWOC), we demonstrated a non-line-of-sight (NLOS) UWOC link adequately enhanced using ultraviolet (UV) 375-nm laser. Path loss was chosen

  19. Near-Infrared Wireless Optical Communication with Particulates In-Suspension over the Underwater Channel

    KAUST Repository

    Lee, It Ee

    2017-05-08

    We demonstrate a gigabit near-infrared-based underwater wireless optical communication link using an 808-nm laser diode to mitigate the particle scattering effect in turbid medium. An improvement in the error performance is observed with increasing concentrations.

  20. On the performance of free-space optical communication systems with multiuser diversity

    KAUST Repository

    Yang, Liang; Gao, Xiqi; Alouini, Mohamed-Slim

    2014-01-01

    Free space optical (FSO) communication has become a cost-effective method to provide high data rates. However, the turbulence-induced fading limits its application to short range applications. To address this, we propose a multiuser diversity (MD

  1. Implementing a Near-Optimal Optical Receiver for Inter-Planetary Communication

    Data.gov (United States)

    National Aeronautics and Space Administration — Proposal Objective: Interplanetary communications signals are inherently weak at the receiver. In fact, for a desired data rate the received optical pulses may...

  2. Superconducting Nanowire Single Photon Detectors for High-Data-Rate Deep-Space Optical Communication

    Data.gov (United States)

    National Aeronautics and Space Administration — High data rate deep space optical communication (DSOC) links for manned and unmanned space exploration have been identified by NASA as a critical future capability,...

  3. Subcarrier MPSK/MDPSK modulated optical wireless communications in lognormal turbulence

    KAUST Repository

    Song, Xuegui; Yang, Fan; Cheng, Julian; Alouini, Mohamed-Slim

    2015-01-01

    Bit-error rate (BER) performance of subcarrier Mary phase-shift keying (MPSK) and M-ary differential phase-shift keying (MDPSK) is analyzed for optical wireless communications over the lognormal turbulence channels. Both exact BER and approximate

  4. Highly Sensitive Photon Counting Detectors for Deep Space Optical Communications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — A new type of a photon-counting photodetector is proposed to advance the state-of the-art in deep space optical communications technology. The proposed detector...

  5. Evaluation of coherence interference in optical wireless communication through multiscattering channels.

    Science.gov (United States)

    Kedar, Debbie; Arnon, Shlomi

    2006-05-10

    Optical wireless communication has been the subject of much research in recent years because of the increasing interest in laser satellite-ground links and urban optical wireless communication. The major sources of performance degradation have been identified as the spatial, angular, and temporal spread of the propagating beam when the propagation channel is multiscattering, resulting in reduced power reception and intersignal interference, as well as turbulence-induced scintillations and noise due to receiver circuitry and background illumination. However, coherence effects due to multipath interference caused by a scattering propagation channel do not appear to have been treated in detail in the scientific literature. We attempt a theoretical analysis of coherence interference in optical wireless communication through scattering channels and try to quantify the resultant performance degradation for different media. We conclude that coherence interference is discernible in optical wireless communication through scattering channels and is highly dependent on the microscopic nature of the propagation medium.

  6. NASA Laser Communications with Adaptive Optics and Linear Mode Photon Counting, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — In this effort, the Optical Sciences Company (tOSC) and Raytheon Vision Systems (RVS) will team to provide NASA with a long range laser communications system for...

  7. Detection and Symbol Synchronization for Multiple-bit Per Photon Optical Communications

    Science.gov (United States)

    Marshall, W. K.

    1985-01-01

    Methods of detection and synchronization in a highly efficient direct detection optical communication system are reported. Results of measurements on this moderate-rate demonstration system capable of transmitting 2.5 bits/detected photon in low-background situations indicate that symbol slot synchronization is not a problem, and that a simple symbol detection scheme is adequate for this situation. This system is a candidate for interplanetary optical communications.

  8. A Cluster Based Group Signature Mechanism For Secure Vanet Communication

    Directory of Open Access Journals (Sweden)

    Navjot Kaur

    2015-08-01

    Full Text Available Vehicular adhoc network is one of the recent area of research to administer safety to human lives controlling of messages and in disposal of messages to users and passengers. VANETs allows communication of moving vehicular nodes. Movement of nodes leads in changing network size and scenario. Whenever a new node joins the network there is a threat of malicious node attack. So we need an environment that is secure and trust worthy. Therefore a new cluster based secure technique is proposed where cluster head is responsible for providing communication between the vehicular nodes. Performance parameters used in this paper are message drop ratio packet delay ratio and verification time.

  9. Using Group Communication to Implement a Fault-Tolerant Directory Service

    NARCIS (Netherlands)

    Kaashoek, M.F.; Tanenbaum, A.S.; Verstoep, C.

    1993-01-01

    Group communication is an important paradigm for building distributed applications. This paper discusses a fault-tolerant distributed directory service based on group communication, and compares it with the previous design and implementation based on remote procedure call. The group directory

  10. Power Transmission by Optical Fibers for Component Inherent Communication

    Directory of Open Access Journals (Sweden)

    Michael Dumke

    2010-02-01

    Full Text Available The use of optical fibers for power transmission has been investigated intensely. An optically powered device combined with optical data transfer offers several advantages compared to systems using electrical connections. Optical transmission systems consist of a light source, a transmission medium and a light receiver. The overall system performance depends on the efficiency of opto-electronic converter devices, temperature and illumination dependent losses, attenuation of the transmission medium and coupling between transmitter and fiber. This paper will summarize the state of the art for optically powered systems and will discuss reasons for negative influences on efficiency. Furthermore, an outlook on power transmission by the use of a new technology for creating polymer optical fibers (POF via micro dispensing will be given. This technology is capable to decrease coupling losses by direct contacting of opto-electronic devices.

  11. Data transmission techniques for short-range optical fiber and wireless communication links

    DEFF Research Database (Denmark)

    Pham, Tien Thang

    The research work described in this thesis is devoted to experimental investigation of techniques for cost-effective high-speed optical communications supporting both wired and wireless services. The main contributions of this thesis have expanded the state-of-the-art in two main areas: high......-speed optical/wireless integration and advanced modulation formats for intensity modulation with direct detection (IM/DD) optical systems. Regarding optical/wireless integration, this thesis focuses on integration of broadband ultra-wide band (UWB) and 60-GHz band wireless systems into optical fiber access...... networks to distribute wireless services in personal area networks (PANs). Photonic technologies to generate and distribute gigabit UWB and 60-GHz-band signals are proposed and demonstrated. Two novel methods are proposed and demonstrated to optically generate Federal Communications Commission (FCC...

  12. An Assessment of the Feasibility of Optical Command Post Communication

    National Research Council Canada - National Science Library

    Downs, Alan

    1997-01-01

    ...., changing the frequency at which the basic combat radio operates). This study addresses taking advantage of the higher bandwidth available in the optical portion of the electromagnetic spectrum...

  13. Statistical simulation of information transfer through non-line-of-sight atmospheric optical communication channels

    Science.gov (United States)

    Tarasenkov, M. V.; Belov, V. V.; Poznakharev, E. S.

    2017-11-01

    Impulse response of non-line-of-sight atmospheric communication channels at wavelengths of 0.3, 0.5, and 0.9 μm are compared for the case in which the optical axes of the receiver and laser radiation lie in the plane perpendicular to the Earth's surface. The most efficient communication channel depending on the base distance is determined. For a wavelength of 0.5 μm and a concrete variant of the transceiving part of the communication system, the limiting communication range and the limiting repetition frequency of pulses that can be transmitted through the communication channel are estimated.

  14. Underwater wireless optical communications: From system-level demonstrations to channel modelling

    KAUST Repository

    Oubei, Hassan M.

    2018-01-09

    In this paper, we discuss about recent experimental advances in underwater wireless optical communications (UWOC) over various underwater channel water types using different modulation schemes as well as modelling and describing the statistical properties of turbulence-induced fading in underwater wireless optical channels using laser beam intensity fluctuations measurements.

  15. Fiber-Optic Communication Links Suitable for On-Board Use in Modern Aircraft

    Science.gov (United States)

    Nguyen, Hung; Ngo, Duc; Alam, Mohammad F.; Atiquzzaman, Mohammed; Sluse, James; Slaveski, Filip

    2004-01-01

    The role of the Advanced Air Transportation Technologies program undertaken at the NASA Glenn Research Centers has been focused mainly on the improvement of air transportation safety, with particular emphasis on air transportation communication systems in on-board aircraft. The conventional solutions for digital optical communications systems specifically designed for local/metro area networks are, unfortunately, not capable of transporting the microwave and millimeter RF signals used in avionics systems. Optical networks capable of transporting RF signals are substantially different from the standard digital optical communications systems. The objective of this paper is to identify a number of different communication link architectures for RF/fiber optic transmission using a single backbone fiber for carrying VHF and UHF RF signals in the aircraft. To support these architectures, two approaches derived from both hybrid RF-optical and all-optical processing methodologies are discussed with single and multiple antennas for explicitly transporting VHF and UHF signals, while the relative merits and demerits of each architecture are also addressed. Furthermore, the experimental results of wavelength division multiplexing (WDM) link architecture from our test-bed platform, configured for aircraft environment to support simultaneous transmission of multiple RF signals over a single optical fiber, exhibit no appreciable signal degradation at wavelengths of both 1330 and 1550 nm, respectively. Our measurements of signal to noise ratio carried out for the transmission of FM and AM analog modulated signals at these wavelengths indicate that WDM is a fiber optic technology which is potentially suitable for avionics applications.

  16. Free Space Optical (FSO) Communications, Towards the Speeds of Wireline Networks

    KAUST Repository

    Alouini, Mohamed-Slim

    2015-01-01

    in the recent past, is not anymore a viable solution to fulfill the demand for more wireless applications and higher data rates. Among the many proposed solutions, optical wireless communication or free-space optical (FSO) systems have gained an increasing

  17. Applications of photonic crystal fibers in optical communications - What is in the future?

    DEFF Research Database (Denmark)

    Bjarklev, Anders Overgaard; Lin, Chinlon

    2005-01-01

    Superior control of guiding properties in photonic-crystal fibers led to several interesting applications in optical communications ranging from nonlinear optical signal processing to high-power fiber amplifiers. This paper will review recent developments and discuss the future possibilities....

  18. Efficient Weibull channel model for salinity induced turbulent underwater wireless optical communications

    KAUST Repository

    Oubei, Hassan M.

    2017-12-13

    Recent advances in underwater wireless optical communications necessitate a better understanding of the underwater channel. We propose the Weibull model to characterize the fading of salinity induced turbulent underwater wireless optical channels. The model shows an excellent agreement with the measured data under all channel conditions.

  19. 16-level differential phase shift keying (D16PSK) in direct detection optical communication systems

    DEFF Research Database (Denmark)

    Sambaraju, R.; Tokle, Torger; Jensen, J.B.

    2006-01-01

    Optical 16-level differential phase shift keying (D16PSK) carrying four bits for every symbol is proposed for direct detection optical communication systems. Transmitter and receiver schematics are presented, and the receiver sensitivity is discussed. We numerically investigate the impact...

  20. Theories in Developing Oral Communication for Specific Learner Group

    Science.gov (United States)

    Hadi, Marham Jupri

    2016-01-01

    The current article presents some key theories most relevant to the development of oral communication skills in an Indonesian senior high school. Critical analysis on the learners' background is employed to figure out their strengths and weaknesses. The brief overview of the learning context and learners' characteristic are used to identify which…

  1. Technology, Talk, and Time: Patterns of Group Communication and Identity

    Science.gov (United States)

    Dahl, Laura Brown

    2015-01-01

    The effective use of technology is increasingly important in many fields where online and digital communication, collaboration, and production have become more prevalent. Although it is clear that many higher education students come into the classroom with skills involved with consuming technology, they often are much less capable of producing…

  2. Information and Communication Technologies : A World Bank Group Strategy

    OpenAIRE

    World Bank

    2002-01-01

    Information and communication technologies provide the basis for increasing and applying knowledge in the private and public sectors. Countries with strong information infrastructures that employ innovative information technology applications, have many advantages for sustained economic growth and social development. This book is, primarily, a business strategy which explains the World Ban...

  3. FINDING FOSSIL GROUPS: OPTICAL IDENTIFICATION AND X-RAY CONFIRMATION

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Eric D. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Rykoff, Eli S. [E.O. Lawrence Berkeley National Lab, 1 Cyclotron Rd., Berkeley, CA 94720 (United States); Dupke, Renato A. [Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109 (United States); Mendes de Oliveira, Claudia; Proctor, Robert N. [Departamento de Astronomia, Instituto de Astronomia, Geofisica e Ciencias Atmosfericas da Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, 05508-090 Sao Paulo (Brazil); Lopes de Oliveira, Raimundo [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Caixa Postal 369, 13560-970 Sao Carlos, SP (Brazil); Garmire, Gordon P. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Koester, Benjamin P. [Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States); McKay, Timothy A., E-mail: milleric@mit.edu [Department of Physics, University of Michigan, 450 Church St., Ann Arbor, MI 48109 (United States)

    2012-03-10

    We report the discovery of 12 new fossil groups (FGs) of galaxies, systems dominated by a single giant elliptical galaxy and cluster-scale gravitational potential, but lacking the population of bright galaxies typically seen in galaxy clusters. These FGs, selected from the maxBCG optical cluster catalog, were detected in snapshot observations with the Chandra X-ray Observatory. We detail the highly successful selection method, with an 80% success rate in identifying 12 FGs from our target sample of 15 candidates. For 11 of the systems, we determine the X-ray luminosity, temperature, and hydrostatic mass, which do not deviate significantly from expectations for normal systems, spanning a range typical of rich groups and poor clusters of galaxies. A small number of detected FGs are morphologically irregular, possibly due to past mergers, interaction of the intra-group medium with a central active galactic nucleus (AGN), or superposition of multiple massive halos. Two-thirds of the X-ray-detected FGs exhibit X-ray emission associated with the central brightest cluster galaxy (BCG), although we are unable to distinguish between AGN and extended thermal galaxy emission using the current data. This sample representing a large increase in the number of known FGs, will be invaluable for future planned observations to determine FG temperature, gas density, metal abundance, and mass distributions, and to compare to normal (non-fossil) systems. Finally, the presence of a population of galaxy-poor systems may bias mass function determinations that measure richness from galaxy counts. When used to constrain power spectrum normalization and {Omega}{sub m}, these biased mass functions may in turn bias these results.

  4. Continuous variable multipartite entanglement and optical implementations of quantum communication networks

    International Nuclear Information System (INIS)

    Lian Yimin; Xie Changde; Peng Kunchi

    2007-01-01

    A variety of optical quantum information networks based on the multipartite entanglement of amplitude and phase quadratures of an electromagnetic field have been proposed and experimentally realized in recent years. The multipartite entanglement of optical continuous variables provides flexible and reliable quantum resources for developing unconditional quantum information networks. In this paper, we review the generation schemes of the multipartite entangled states of optical continuous quantum variables and some applications in the quantum communication networks with emphasis on the experimental implementations

  5. LEO-to-ground optical communications using SOTA (Small Optical TrAnsponder) - Payload verification results and experiments on space quantum communications

    Science.gov (United States)

    Carrasco-Casado, Alberto; Takenaka, Hideki; Kolev, Dimitar; Munemasa, Yasushi; Kunimori, Hiroo; Suzuki, Kenji; Fuse, Tetsuharu; Kubo-Oka, Toshihiro; Akioka, Maki; Koyama, Yoshisada; Toyoshima, Morio

    2017-10-01

    Free-space optical communications have held the promise of revolutionizing space communications for a long time. The benefits of increasing the bitrate while reducing the volume, mass and energy of the space terminals have attracted the attention of many researchers for a long time. In the last few years, more and more technology demonstrations have been taking place with participants from both the public and the private sector. The National Institute of Information and Communications Technology (NICT) in Japan has a long experience in this field. SOTA (Small Optical TrAnsponder) was the last NICT space lasercom mission, designed to demonstrate the potential of this technology applied to microsatellites. Since the beginning of SOTA mission in 2014, NICT regularly established communication using the Optical Ground Stations (OGS) located in the Headquarters at Koganei (Tokyo) to receive the SOTA signals, with over one hundred successful links. All the goals of the SOTA mission were fulfilled, including up to 10-Mbit/s downlinks using two different wavelengths and apertures, coarse and fine tracking of the OGS beacon, space-to-ground transmission of the on-board-camera images, experiments with different error correcting codes, interoperability with other international OGS, and experiments on quantum communications. The SOTA mission ended on November 2016, more than doubling the designed lifetime of 1-year. In this paper, the SOTA characteristics and basic operation are explained, along with the most relevant technological demonstrations.

  6. Digital semaphore: technical feasibility of QR code optical signaling for fleet communications

    OpenAIRE

    Lucas, Andrew R.

    2013-01-01

    Approved for public release; distribution is unlimited In recent decades, optical LOS communications such as flag semaphore or flashing light have atrophied to the point where, if they are required, U.S. Naval forces are at a distinct disadvantage. RF communications have become critical to nearly all operations, but this capability comes at the cost of disclosing the location of operations. Depending on the platform, these RF communications can become a critical vulnerability. EMCON attemp...

  7. The analysis of an optical fibre communication system using laser ...

    African Journals Online (AJOL)

    Such techniques include electrical and optical dispersion compensation, optical and electrical pulse shaping, and modifications of the fibre dispersion profiles. Some of these techniques and methods have resulted into very effective but expensive systems, and it has been difficult to adopt them. Others have resulted into ...

  8. System concepts and design examples for optical communication with planetary spacecraft

    Science.gov (United States)

    Lesh, James R.

    Systems concepts for optical communication with future deep-space (planetary) spacecraft are described. These include not only the optical transceiver package aboard the distant spacecraft, but the earth-vicinity optical-communications receiving station as well. Both ground-based, and earth-orbiting receivers are considered. Design examples for a number of proposed or potential deep-space missions are then presented. These include an orbital mission to Saturn, a Lander and Rover mission to Mars, and an astronomical mission to a distance of 1000 astronomical units.

  9. Feasibility of infrared Earth tracking for deep-space optical communications.

    Science.gov (United States)

    Chen, Yijiang; Hemmati, Hamid; Ortiz, Gerry G

    2012-01-01

    Infrared (IR) Earth thermal tracking is a viable option for optical communications to distant planet and outer-planetary missions. However, blurring due to finite receiver aperture size distorts IR Earth images in the presence of Earth's nonuniform thermal emission and limits its applicability. We demonstrate a deconvolution algorithm that can overcome this limitation and reduce the error from blurring to a negligible level. The algorithm is applied successfully to Earth thermal images taken by the Mars Odyssey spacecraft. With the solution to this critical issue, IR Earth tracking is established as a viable means for distant planet and outer-planetary optical communications. © 2012 Optical Society of America

  10. Concurrent System Engineering and Risk Reduction for Dual-Band (RF/optical) Spacecraft Communications

    Science.gov (United States)

    Fielhauer, Karl, B.; Boone, Bradley, G.; Raible, Daniel, E.

    2012-01-01

    This paper describes a system engineering approach to examining the potential for combining elements of a deep-space RF and optical communications payload, for the purpose of reducing the size, weight and power burden on the spacecraft and the mission. Figures of merit and analytical methodologies are discussed to conduct trade studies, and several potential technology integration strategies are presented. Finally, the NASA Integrated Radio and Optical Communications (iROC) project is described, which directly addresses the combined RF and optical approach.

  11. Nonlinear effects in ultralong semiconductor optical amplifiers for optical communications. Physics and applications

    Energy Technology Data Exchange (ETDEWEB)

    Runge, Patrick

    2010-10-19

    The presented work discusses physical properties of ultralong semiconductor optical amplifiers (UL-SOAs) and some of their possible applications in optical communication systems. At the beginning of this thesis the analytical framework for the optical properties of UL-SOAs is presented. Based on this theoretical description, a numerical simulation model is derived used for the investigation of this thesis. To obtain from the simulation model realistic results the important properties of UL-SOAs have to be included, e.g., being the saturation of the main part of the device. In this saturated part of the device, fast intraband effects dominate over the slow interband effects. The intention of UL-SOAs is to make use of these pronounced fast intraband effects in applications. Due to the short relaxation times of the fast intraband effects, they can be used for high-speed signal processing (>20 GBaud). With the help of an additional continuous wave (CW) signal propagating with the data signal in the UL-SOA, the capability for all-optical signal processing with 100 Gbit/s on-off keying RZ-50% pseudo random bit sequence signals has been demonstrated in this thesis. With an optimised device under proper driving conditions, bit pattern effects are negligible compared to the degradation due to amplified spontaneous emission. The suppression of the bit pattern effects can be ascribed to the additional CW signal operating as a holding beam. Investigations of the UL-SOA's driving condition showed that the data signal's extinction ratio (ER) can be regenerated if the two input signals are co-polarised and the data signal has a shorter wavelength than the CW signal. These two and other driving conditions have indicated, that parametric amplification due to four-wave mixing (FWM) (Bogatov-like effect) is the reason for the ER improvement. Moreover, due to the additional CW signal, all-optical wavelength conversion (AOWC) is possible which can be combined with the ER

  12. Crisis Communication Competence in Co-Producing Safety with Citizen Groups

    Directory of Open Access Journals (Sweden)

    Anne Laajalahti

    2016-03-01

    Full Text Available The aim of this article is to explore interpersonal communication competence needed by crisis communication and management experts when co-operating with citizen groups in response to emergencies. Moreover, the purpose is to understand how response organizations can further develop this crisis communication competence and so contribute to the functioning of response networks. The research task is approached qualitatively by eliciting crisis communication and management experts’ (n = 33 perceptions of the interpersonal communication competence response organizations needs when co-operating with citizen groups. The data were gathered via an international online questionnaire using a method referred to as “thematic writing” and consist of written responses to open-ended questions on what constitutes the core of crisis communication competence and what aspects of it need more attention. The research findings indicate that co-producing safety with citizen groups demands crisis communication competence related to message production, message reception, and interaction between experts and citizen groups. In addition, the findings clarify what areas of crisis communication competence need to be further developed to facilitate co-operation between experts and citizen groups. However, the authors suggest that crisis communication competence should not be seen solely as a characteristic of individual crisis communicators but approached as a networked and co-created area of competence.

  13. Stereo multiplexing for direct detected optical communication systems

    NARCIS (Netherlands)

    Gaete, O.; Coelho, L.D.; Spinnler, B.; Al Fiad, M.S.A.S.; Jansen, S.L.; Hanik, N.

    2009-01-01

    We propose a novel technique that allows simultaneous detection of two modulated optical sub-carriers. A proof-of-principle experiment is described and subsequently the performance at high data rates (111Gb/s) is assessed by simulations.

  14. Ionospheric effects on terrestrial communications: Working Group 3 overview

    Czech Academy of Sciences Publication Activity Database

    Laštovička, Jan; Bourdillon, A.

    2004-01-01

    Roč. 47, 2/3 (2004), s. 1269-1277 ISSN 1593-5213. [Final Meeting COST271 Action. Effects of the upper atmosphere on terrestrial and Earth-space communications (EACOS). Abingdon, 26.08.2004-27.08.2004] R&D Projects: GA MŠk OC 271.10; GA AV ČR IBS3012007 Institutional research plan: CEZ:AV0Z3042911 Keywords : ionospheric reflection * telecommunications * gravity waves * planetary waves Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.413, year: 2004 http://www.annalsofgeophysics.eu/index.php/annals/article/view/3299/3345

  15. Analyzing Effective Communication in Mathematics Group Work: The Role of Visual Mediators and Technical Terms

    Science.gov (United States)

    Ryve, Andreas; Nilsson, Per; Pettersson, Kerstin

    2013-01-01

    Analyzing and designing productive group work and effective communication constitute ongoing research interests in mathematics education. In this article we contribute to this research by using and developing a newly introduced analytical approach for examining effective communication within group work in mathematics education. By using data from…

  16. MMIC front-ends for optical communication systems

    DEFF Research Database (Denmark)

    Petersen, Anders Kongstad

    1993-01-01

    Two different types of optical front-end MMIC amplifiers for a 2.5-Gb/s coherent heterodyne optical receiver are presented. A bandwidth of 6-12 GHz has been obtained for a tuned front-end and 3-13 GHz for a distributed front-end. An input noise current density of 5-15 pA/√Hz has been obtained for...

  17. Application of Nanophotonic Devices in High Speed Optical Communications

    DEFF Research Database (Denmark)

    Vukovic, Dragana

    All-optical signal processing has attracted a significant research interest in the past decade as it might become competitive with electronics in terms of compactness, energy consumption, and reliability. Furthermore it might solve the current bandwidth mismatch between optical transmission...... linear and nonlinear impairments, which accumulate along the link and limit the reach of the system. These impairments need to be compensated. Since four-wave mixing provides phase conjugation of the converted signal, dispersion and nonlinearity distortion accumulated during transmission can...

  18. Information theory and its application to optical communication

    NARCIS (Netherlands)

    Willems, F.M.J.

    2017-01-01

    The lecture focusses on the foundations of communication which were developed within the field of information theory. Enumerative shaping techniques and the so-called squareroot transform will be discussed in detail.

  19. A Compact, Low Power Pulsed Optical Communication System for Spacecraft

    Data.gov (United States)

    National Aeronautics and Space Administration — The goal of this project is to reduce the power required for high bandwidth, deep space laser communications systems. Our concept will encode data in the time delay...

  20. Optical Non-Orthogonal Multiple Access for Visible Light Communication

    OpenAIRE

    Marshoud, Hanaa; Muhaidat, Sami; Sofotasios, Paschalis C.; Hussain, Sajjad; Imran, Muhammad Ali; Sharif, Bayan S.

    2017-01-01

    The proliferation of mobile Internet and connected devices, offering a variety of services at different levels of performance, represents a major challenge for the fifth generation wireless networks and beyond. This requires a paradigm shift towards the development of key enabling techniques for the next generation wireless networks. In this respect, visible light communication (VLC) has recently emerged as a new communication paradigm that is capable of providing ubiquitous connectivity by c...

  1. Reggio Emilia Inspired Learning Groups: Relationships, Communication, Cognition, and Play

    Science.gov (United States)

    Hong, Seong Bock; Shaffer, LaShorage; Han, Jisu

    2017-01-01

    A key aspect of the Reggio Emilia inspired curriculum is a learning group approach that fosters social and cognitive development. The purpose of this paper is to investigate how a Reggio Emilia inspired learning group approach works for children with and without disabilities. This study gives insight into how to form an appropriate learning group…

  2. Communication Network Integration and Group Uniformity in a Complex Organization.

    Science.gov (United States)

    Danowski, James A.; Farace, Richard V.

    This paper contains a discussion of the limitations of research on group processes in complex organizations and the manner in which a procedure for network analysis in on-going systems can reduce problems. The research literature on group uniformity processes and on theoretical models of these processes from an information processing perspective…

  3. Optical Amplication for Terabit-per-Second Ultra-High Speed Communication Systems

    DEFF Research Database (Denmark)

    Lali-Dastjerdi, Zohreh

    The present thesis is concerned with fiber optical parametric amplification and regeneration for high-speed optical communication systems. Fiber optical parametric amplifiers (FOPAs) have multi-functional applications depending on their implementation in optical systems. Based on a few femtosecond...... and saturation effect in order to assess the degradation of the amplified signal. In a very good agreement with the performed experiments, it is shown that the noise transferred to the signal can be effectively suppressed by operating in the saturation regime. The amplification of short few picosecond...

  4. Communication Network Architectures Based on Ethernet Passive Optical Network for Offshore Wind Power Farms

    Directory of Open Access Journals (Sweden)

    Mohamed A. Ahmed

    2016-03-01

    Full Text Available Nowadays, with large-scale offshore wind power farms (WPFs becoming a reality, more efforts are needed to maintain a reliable communication network for WPF monitoring. Deployment topologies, redundancy, and network availability are the main items to enhance the communication reliability between wind turbines (WTs and control centers. Traditional communication networks for monitoring and control (i.e., supervisory control and data acquisition (SCADA systems using switched gigabit Ethernet will not be sufficient for the huge amount of data passing through the network. In this paper, the optical power budget, optical path loss, reliability, and network cost of the proposed Ethernet Passive Optical Network (EPON-based communication network for small-size offshore WPFs have been evaluated for five different network architectures. The proposed network model consists of an optical network unit device (ONU deployed on the WT side for collecting data from different internal networks. All ONUs from different WTs are connected to a central optical line terminal (OLT, placed in the control center. There are no active electronic elements used between the ONUs and the OLT, which reduces the costs and complexity of maintenance and deployment. As fiber access networks without any protection are characterized by poor reliability, three different protection schemes have been configured, explained, and discussed. Considering the cost of network components, the total implementation expense of different architectures with, or without, protection have been calculated and compared. The proposed network model can significantly contribute to the communication network architecture for next generation WPFs.

  5. Preface to the special issue on ;Optical Communications Exploiting the Space Domain;

    Science.gov (United States)

    Wang, Jian; Yu, Siyuan; Li, Guifang

    2018-02-01

    The demand for high capacity optical communications will continue to be driven by the exponential growth of global internet traffic. Optical communications are about the exploitation of different physical dimensions of light waves, including complex amplitude, frequency (or wavelength), time, polarization, etc. Conventional techniques such as wavelength-division multiplexing (WDM), time-division multiplexing (TDM) and polarization-division multiplexing (PDM) have almost reached their scalability limits. Space domain is the only known physical dimension left and space-division multiplexing (SDM) seems the only option to further scale the transmission capacity and spectral efficiency of optical communications. In recent years, few-mode fiber (FMF), multi-mode fiber (MMF), multi-core fiber (MCF) and few-mode multi-core fiber (FM-MCF) have been widely explored as promising candidates for fiber-based SDM. The challenges for SDM include efficient (de)multiplexer, amplifiers, and multiple-input multiple-output (MIMO) digital signal processing (DSP) techniques. Photonic integration will also be a key technology to SDM. Meanwhile, free-space and underwater optical communications have also exploited the space domain to increase the transmission capacity and spectral efficiency. The challenges include long-distance transmission limited by propagation loss, divergence, scattering and turbulence. Very recently, helically phased light beams carrying orbital angular momentum (OAM) have also seen potential applications both in free-space, underwater and fiber-based optical communications. Actually, different mode bases such as linearly polarized (LP) modes and OAM modes can be employed for SDM. Additionally, SDM could be used in chip-scale photonic interconnects and data center optical interconnects. Quantum processing exploiting the space domain is of great interest. The information capacity limit and physical layer security in SDM optical communications systems are important

  6. Multi-carrier transmission for hybrid radio frequency with optical wireless communications

    Science.gov (United States)

    Wang, Gang; Chen, Genshe; Shen, Dan; Pham, Khanh; Blasch, Erik; Nguyen, Tien M.

    2015-05-01

    Radio frequency (RF) wireless communication is reaching its capacity to support large data rate transmissions due to hardware constraints (e.g., silicon processes), software strategies (e.g., information theory), and consumer desire for timely large file exchanges (e.g., big data and mobile cloud computing). A high transmission rate performance must keep pace with the generated huge volumes of data for real-time processing. Integrated RF and optical wireless communications (RF/OWC) could be the next generation transmission technology to satisfy both the increased data rate exchange and the communications constraints. However, with the promising benefits of RF/OWC, challenges remain to fully develop hybrid RF with wireless optical communications such as uniform waveform design for information transmission and detection. In this paper, an orthogonal frequency division multiplexing (OFDM) transmission scheme, which widely employed in RF communications, is developed for optical communications. The traditional high peak-to-average power ratio (PAPR) in OFDM is reduced to improve system performance. The proposed multi-carrier waveform is evaluated with a frequency-selective fading channel. The results demonstrate that bit error rate (BER) performance of our proposed optical OFDM transmission technique outperforms the traditional OWC on-off keying (OOK) transmission scheme.

  7. Performance of Group Communication Over Ad-Hoc Networks

    National Research Council Canada - National Science Library

    Mosko, Marc; Garcia-Luna-Aceves, J. J

    2002-01-01

    ... through a network of cluster trees, where a spanning tree joins groups of fully connected nodes. Through numerical analysis and simulations in GloMoSim, we show throughput, goodput, and loss rates for reliable and unreliable networks...

  8. Quantum ratchets for quantum communication with optical superlattices

    International Nuclear Information System (INIS)

    Romero-Isart, Oriol; Garcia-Ripoll, Juan Jose

    2007-01-01

    We propose to use a quantum ratchet to transport quantum information in a chain of atoms trapped in an optical superlattice. The quantum ratchet is created by a continuous modulation of the optical superlattice which is periodic in time and in space. Though there is zero average force acting on the atoms, we show that indeed the ratchet effect permits atoms on even and odd sites to move along opposite directions. By loading the optical lattice with two-level bosonic atoms, this scheme permits us to perfectly transport a qubit or entangled state imprinted in one or more atoms to any desired position in the lattice. From the quantum computation point of view, the transport is achieved by a smooth concatenation of perfect swap gates. We analyze setups with noninteracting and interacting particles and in the latter case we use the tools of optimal control to design optimal modulations. We also discuss the feasibility of this method in current experiments

  9. Optics Communications: Special issue on Polymer Photonics and Its Applications

    Science.gov (United States)

    Zhang, Ziyang; Pitwon, Richard C. A.; Feng, Jing

    2016-03-01

    In the last decade polymer photonics has witnessed a tremendous boost in research efforts and practical applications. Polymer materials can be engineered to exhibit unique optical and electrical properties. Extremely transparent and reliable passive optical polymers have been made commercially available and paved the ground for the development of various waveguide components. Advancement in the research activities regarding the synthesis of active polymers has enabled devices such as ultra-fast electro-optic modulators, efficient white light emitting diodes, broadband solar cells, flexible displays, and so on. The fabrication technology is not only fast and cost-effective, but also provides flexibility and broad compatibility with other semiconductor processing technologies. Reports show that polymers have been integrated in photonic platforms such as silicon-on-insulator (SOI), III-V semiconductors, and silica PLCs, and vice versa, photonic components made from a multitude of materials have been integrated, in a heterogeneous/hybrid manner, in polymer photonic platforms.

  10. Statistics of errors in fibre communication lines with a phase-modulation format and optical phase conjugation

    International Nuclear Information System (INIS)

    Shapiro, Elena G; Fedoruk, Mikhail P

    2011-01-01

    Analytical formulas are derived to approximate the probability density functions of 'zero' and 'one' bits in a linear communication channel with a binary format of optical signal phase modulation. Direct numerical simulation of the propagation of optical pulses in a communication line with optical phase conjugation is performed. The results of the numerical simulation are in good agreement with the analytical approximation. (fibreoptic communication lines)

  11. Patients’ perspectives on antenatal group consultations: Identifying communicative strengths and weaknesses

    DEFF Research Database (Denmark)

    Jensen, Matilde Nisbeth; Fage-Butler, Antoinette Mary

    Introduction and objectives: The doctor-patient dyad has constituted the main paradigmatic relationship in Western medicine, and provided a central focus for health communication research and clinical teaching endeavors. With new technologies, other constellations are enabled, such as patient......-patient communication, which is increasingly taking place in online patient communities. One novel offline setting which can support patient-patient communication is the group consultation where an individual healthcare professional and a group of patients engage. The purpose of this study is to investigate how patient......-patient communication unfolds in a group consultation with a midwife in order to identify its communicative strengths and weaknesses. Methods: Using a sequential multi-methods design, we performed eight individual interviews with pregnant women from a Danish antenatal clinic about their experiences of two group...

  12. The impact of LED transfer function nonlinearity on high-speed optical wireless communications based on discrete-multitone modulation

    NARCIS (Netherlands)

    Inan, B.; Lee, S.C.J.; Randel, S.; Neokosmidis, L.; Koonen, A.M.J.; Walewski, J.

    2009-01-01

    The nonlinear dependence of the optical power from white LEDs on the applied driving current and its impact on discrete-multitone modulation was investigated by use of numerical simulations for the case of optical wireless communications.

  13. Next-Generation NASA Earth-Orbiting Relay Satellites: Fusing Optical and Microwave Communications

    Science.gov (United States)

    Israel, David J.; Shaw, Harry

    2018-01-01

    NASA is currently considering architectures and concepts for the generation of relay satellites that will replace the Tracking and Data Relay Satellite (TDRS) constellation, which has been flying since 1983. TDRS-M, the last of the second TDRS generation, launched in August 2017, extending the life of the TDRS constellation beyond 2030. However, opportunities exist to re-engineer the concepts of geosynchronous Earth relay satellites. The needs of the relay satellite customers have changed dramatically over the last 34 years since the first TDRS launch. There is a demand for greater bandwidth as the availability of the traditional RF spectrum for space communications diminishes and the demand for ground station access grows. The next generation of NASA relay satellites will provide for operations that have factored in these new constraints. In this paper, we describe a heterogeneous constellation of geosynchronous relay satellites employing optical and RF communications. The new constellation will enable new optical communications services formed by user-to-space relay, space relay-to-space relay and space relay-to-ground links. It will build upon the experience from the Lunar Laser Communications Demonstration from 2013 and the Laser Communications Relay Demonstration to be launched in 2019.Simultaneous to establishment of the optical communications space segment, spacecraft in the TDRS constellation will be replaced with RF relay satellites with targeted subsets of the TDRS capabilities. This disaggregation of the TDRS service model will allow for flexibility in replenishing the needs of legacy users as well as addition of new capabilities for future users. It will also permit the U.S. government access to launch capabilities such as rideshare and to hosted payloads that were not previously available.In this paper, we also explore how the next generation of Earth relay satellites provides a significant boost in the opportunities for commercial providers to the

  14. Next-Generation NASA Earth-Orbiting Relay Satellites: Fusing Microwave and Optical Communications

    Science.gov (United States)

    Israel, David J.

    2018-01-01

    NASA is currently considering architectures and concepts for the generation of relay satellites that will replace the Tracking and Data Relay Satellite (TDRS) constellation, which has been flying since 1983. TDRS-M, the last of the second TDRS generation, launched in August 2017, extending the life of the TDRS constellation beyond 2030. However, opportunities exist to re-engineer the concepts of geosynchronous Earth relay satellites. The needs of the relay satellite customers have changed dramatically over the last 34 years since the first TDRS launch. There is a demand for greater bandwidth as the availability of the traditional RF spectrum for space communications diminishes and the demand for ground station access grows. The next generation of NASA relay satellites will provide for operations that have factored in these new constraints. In this paper, we describe a heterogeneous constellation of geosynchronous relay satellites employing optical and RF communications. The new constellation will enable new optical communications services formed by user-to-space relay, space relay-to-space relay and space relay-to-ground links. It will build upon the experience from the Lunar Laser Communications Demonstration from 2013 and the Laser Communications Relay Demonstration to be launched in 2019.Simultaneous to establishment of the optical communications space segment, spacecraft in the TDRS constellation will be replaced with RF relay satellites with targeted subsets of the TDRS capabilities. This disaggregation of the TDRS service model will allow for flexibility in replenishing the needs of legacy users as well as addition of new capabilities for future users. It will also permit the U.S. government access to launch capabilities such as rideshare and to hosted payloads that were not previously available. In this paper, we also explore how the next generation of Earth relay satellites provides a significant boost in the opportunities for commercial providers to the

  15. Study of optimum methods of optical communication. [accounting for the effects of the turbulent atmosphere and quantum mechanics

    Science.gov (United States)

    Harger, R. O.

    1974-01-01

    Abstracts are reported relating to the techniques used in the research concerning optical transmission of information. Communication through the turbulent atmosphere, quantum mechanics, and quantum communication theory are discussed along with the results.

  16. Bandwidth enhancement of wireless optical communication link using a near-infrared laser over turbid underwater channel

    KAUST Repository

    Lee, It Ee; Guo, Yujian; Ng, Tien Khee; Park, Kihong; Alouini, Mohamed-Slim; Ooi, Boon S.

    2017-01-01

    Underwater wireless optical communication (UWOC) has been widely studied as a promising alternative to establish reliable short-range marine communication links. Microscopic particulates suspended in various ocean, harbor and natural waters

  17. Error statistics during the propagation of short optical pulses in a high-speed fibreoptic communication line

    International Nuclear Information System (INIS)

    Shapiro, E G

    2008-01-01

    Simple analytic expressions are derived to approximate the bit error rate for data transmission through fibreoptic communication lines. The propagation of optical pulses is directly numerically simulated. Analytic estimates are in good agreement with numerical calculations. (fibreoptic communication)

  18. Optical fibers with low nonlinearity and low polarization-mode dispersion for terabit communications

    Science.gov (United States)

    Baghdadi, J. A.; Safaai-Jazi, A.; Hattori, H. T.

    2001-07-01

    Refractive-index nonlinearities have negligible effect on the performance of short-haul fiber-optic communication links utilizing electronic repeaters. However, in long links, nonlinearities can cause severe signal degradations. To mitigate nonlinear effects, a new generation of fibers, referred to as large effective-area fibers, have been introduced in recent years. This paper reviews the latest research and development work on these fibers conducted by several research groups around the world. Attention is focused on a class of large effective-area fibers that are based on a depressed-core multiple-cladding design. Another important issue in long-haul and high capacity fiber optic systems is the polarization-mode dispersion (PMD) which has been recognized as a serious limiting factor. In this paper, an improved fiber design is proposed which, in addition to providing large effective-area and low bending loss, eliminates PMD due to elliptical deformation in the single-mode wavelength region. Furthermore, this design is allowed to provide a small chromatic dispersion about few ps/ nm km , in order to overcome four-wave mixing effects.

  19. Temporal Probabilistic Constellation Shaping for WDM Optical Communication Systems

    DEFF Research Database (Denmark)

    Yankov, Metodi Plamenov; Forchhammer, Søren

    2016-01-01

    Finite state machine sources transmitting QPSK are studied as input to WDM optical fiber systems with ideal distributed Raman amplification. The probabilities of successive constellation symbols are shaped for nonlinear transmission and gains of around 500km (5-10%) are demonstrated...

  20. Temporal Probabilistic Constellation Shaping for WDM Optical Communication Systems

    OpenAIRE

    Yankov, Metodi Plamenov; Forchhammer, Søren

    2016-01-01

    Finite state machine sources transmitting QPSK are studied as input to WDM optical fiber systems with ideal distributed Raman amplification. The probabilities of successive constellation symbols are shaped for nonlinear transmission and gains of around 500km (5-10%) are demonstrated

  1. Soliton-based ultra-high speed optical communications

    Indian Academy of Sciences (India)

    lightwave may be expressed by a modulation amplitude ¯E(z,t) of the optical electric field. E(z,t). E(z,t) = 1. 2. ¯E(z ... the lightwaves is important to minimize the pulse deformation even in case of the digital formats. ...... Pure Appl. Math. 21, 467 ...

  2. Opto-mechanical design and gravity-deformation analysis on optical telescope in laser communication system

    Science.gov (United States)

    Fu, Sen; Du, Jindan; Song, Yiwei; Gao, Tianyu; Zhang, Daqing; Wang, Yongzhi

    2017-11-01

    In space laser communication, optical antennas are one of the main components and the precision of optical antennas is very high. In this paper, it is based on the R-C telescope and it is carried out that the design and simulation of optical lens and supporting truss, according to the parameters of the systems. And a finite element method (FEM) was used to analyze the deformation of the optical lens. Finally, the Zernike polynomial was introduced to fit the primary mirror with a diameter of 250mm. The objective of this study is to determine whether the wave-front aberration of the primary mirror can meet the imaging quality. The results show that the deterioration of the imaging quality caused by the gravity deformation of primary and secondary mirrors. At the same time, the optical deviation of optical antenna increase with the diameter of the pupil.

  3. A Measure of the Personal Perception of In-group Communication about Social Objects

    OpenAIRE

    João Wachelke

    2016-01-01

    The aim of the study was to create a measure of group communication on social objects. An instrument was elaborated, and validity evidence was sought for two topics. The participants were 803 undergraduate students. For both topics, the instrument was adequate to the theoretical structure of three factors: communication frequency; importance of group opinion; similarity with group opinion. Other than presenting satisfactory indexes and precision, the instrument discriminated parti...

  4. Optimized optical wireless channel for indoor and intra-vehicle communications: power distribution and SNR analysis

    Science.gov (United States)

    Shaaban, Rana; Faruque, Saleh

    2018-01-01

    Light emitting diodes - LEDs are modernizing the indoor illumination and replacing current incandescent and fluorescent lamps rapidly. LEDs have multiple advantages such as extremely high energy efficient, longer lifespan, and lower heat generation. Due to the ability to switch to different light intensity at a very fast rate, LED has given rise to a unique communication technology (visible light communication - VLC) used for high speed data transmission. By studying various kinds of commonly used VLC channel analysis: diffuse and line of sight channels, we presented a simply improved indoor and intra-vehicle visible light communication transmission model. Employing optical wireless communications within the vehicle, not only enhance user mobility, but also alleviate radio frequency interference, and increase efficiency by lowering the complexity of copper cabling. Moreover, a solution to eliminate ambient noise caused by environmental conditions is examined by using optical differential receiver. The simulation results show the improved received power distribution and signal to noise ratio - SNR.

  5. Self-reverse-biased solar panel optical receiver for simultaneous visible light communication and energy harvesting.

    Science.gov (United States)

    Shin, Won-Ho; Yang, Se-Hoon; Kwon, Do-Hoon; Han, Sang-Kook

    2016-10-31

    We propose a self-reverse-biased solar panel optical receiver for energy harvesting and visible light communication. Since the solar panel converts an optical component into an electrical component, it provides both energy harvesting and communication. The signal component can be separated from the direct current component, and these components are used for communication and energy harvesting. We employed a self-reverse-biased receiver circuit to improve the communication and energy harvesting performance. The reverse bias on the solar panel improves the responsivity and response time. The proposed system achieved 17.05 mbps discrete multitone transmission with a bit error rate of 1.1 x 10-3 and enhanced solar energy conversion efficiency.

  6. 850-nm hybrid fiber/free-space optical communications using orbital angular momentum modes

    DEFF Research Database (Denmark)

    Jurado-Navas, Antonio; Tatarczak, Anna; Lu, Xiaofeng

    2015-01-01

    Light beams can carry orbital angular momentum (OAM) associated to the helicity of their phasefronts. These OAM modes can be employed to encode information onto a laser beam for transmitting not only in a fiber link but also in a free-space optical (FSO) one. Regarding this latter scenario, FSO...... communications are considered as an alternative and promising mean complementing the traditional optical communications in many applications where the use of fiber cable is not justified. This next generation FSO communication systems have attracted much interest recently, and the inclusion of beams carrying OAM...... modes can be seen as an efficient solution to increase the capacity and the security in the link. In this paper, we discuss an experimental demonstration of a proposal for next generation FSO communication system where a light beam carrying different OAM modes and affected by M turbulence is coupled...

  7. Design of an Electro-Optic Modulator for High Speed Communications

    Science.gov (United States)

    Espinoza, David

    The telecommunications and computer technology industries have been requiring higher communications speeds at all levels for devices, components and interconnected systems. Optical devices and optical interconnections are a viable alternative over other traditional technologies such as copper-based interconnections. Latency reductions can be achieved through the use of optical interconnections. Currently, a particular architecture for optical interconnections is being studied at the University of Colorado at Boulder in the EMT/NANO project, called Broadcast Optical Interconnects for Global Communication in Many-Core Chip Multiprocessor. As with most types of networks, including optical networks, one of the most important components are modulators. Therefore adequate design and fabrication techniques for modulators contribute to higher modulation rates which lead to improve the efficiency and reductions in the latency of the optical network. Electro-optical modulators are presented in this study as an alternative to achieve this end. In recent years, nonlinear optical (NLO) materials have been used for the fabrication of high-speed electro-optical modulators. Polymers doped with chromophores are an alternative among NLO materials because they can develop large electro-optic coefficients and low dielectric constants. These two factors are critical for achieving high-speed modulation rates. These polymer-based electro-optical modulators can be fabricated using standard laboratory techniques, such as polymer spin-coating onto substrates, UV bleaching to achieve a refractive index variation and poling techniques to align the chromophores in cured polymers. The design of the electro-optic modulators require the use of the optical parameters of the materials to be used. Therefore the characterization of these materials is a required previous step. This characterization is performed by the fabrication of chromophores-doped polymer samples and conducting transmission and

  8. GGOS working group on ground networks and communications

    Science.gov (United States)

    Pearlman, M.; Altamimi, Z.; Beck, N.; Forsberg, R.; Gurtner, W.; Kenyon, S.; Behrend, D.; Lemoine, F. G.; Ma, C.; Noll, C. E.; hide

    2005-01-01

    Activities of this Working Group include the investigation of the status quo and the development of a plan for full network integration to support improvements in terrestrial reference frame establishment and maintenance, Earth orientation and gravity field monitoring, precision orbit determination, and other geodetic and gravimetric applications required for the long-term observation of global change. This integration process includes the development of a network of fundamental stations with as many co-located techniques as possible, with precisely determined intersystem vectors. This network would exploit the strengths of each technique and minimize the weaknesses where possible. This paper discusses the organization of the working group, the work done to date, and future tasks.

  9. Fiber optical sensing on-board communication satellites

    Science.gov (United States)

    Hurni, A.; Lemke, N. M. K.; Roner, M.; Obermaier, J.; Putzer, P.; Kuhenuri Chami, N.

    2017-11-01

    Striving constantly to reduce mass, AIT effort and overall cost of the classical point-to-point wired temperature sensor harness on-board telecommunication satellites, OHB System (formerly Kayser-Threde) has introduced the Hybrid Sensor Bus (HSB) system. As a future spacecraft platform element, HSB relies on electrical remote sensor units as well as fiber-optical sensors, both of which can serially be connected in a bus architecture. HSB is a modular measurement system with many applications, also thanks to the opportunities posed by the digital I²C bus. The emphasis, however, is on the introduction of fiber optics and especially fiber-Bragg grating (FBG) temperature sensors as disruptive innovation for the company's satellite platforms. The light weight FBG sensors are directly inscribed in mechanically robust and radiation tolerant fibers, reducing the need for optical fiber connectors and splices to a minimum. Wherever an FBG sensor shall be used, the fiber is glued together with a corresponding temperature transducer to the satellites structure or to a subsystem. The transducer is necessary to provide decoupling of mechanical stress, but simultaneously ensure a high thermal conductivity. HSB has been developed in the frame of an ESA-ARTES program with European and German co-funding and will be verified as flight demonstrator on-board the German Heinrich Hertz satellite (H2Sat). In this paper the Engineering Model development of HSB is presented and a Fiber-optical Sensor Multiplexer for a more flexible sensor bus architecture is introduced. The HSB system aims at telecommunication satellite platforms with an operational life time beyond 15 years in geostationary orbit. It claims a high compatibility in terms of performance and interfaces with existing platforms while it was designed with future applications with increased radiation exposure already in mind. In its basic configuration HSB consists of four modules which are the Power Supply Unit, the HSB

  10. Optics and communication technology major of physics undergraduate degree at King Mongkut's Institute of Technology Ladkrabang

    Science.gov (United States)

    Buranasiri, Prathan

    2014-09-01

    A physics undergraduate degree major in optics and communication technology has been offered at King Mongkut's Institute of Technology Ladkrabang (KMITL), Bangkok, Thailand. There are nine required three credit hour courses including two laboratory courses plus a number of selections in optics and communication based technology courses. For independent thinking and industrial working skills, nine credit hours of research project, practical training or overseas studies are included for selection in the final semester. Students are encouraged to participate in international conferences and professional organizations. Recently the program, with support from SPIE and OSA, has organized its first international conference on photonic solutions 2013 (ICPS 2013).

  11. High phase noise tolerant pilot-tone-aided DP-QPSK optical communication systems

    DEFF Research Database (Denmark)

    Zhang, Xu; Pang, Xiaodan; Deng, Lei

    2012-01-01

    In this paper we experimentally demonstrate a novel, high phase-noise tolerant, optical dual polarization (DP) quadrature phase-shift keying (QPSK) communication system based on pilot-tone-aided phase noise cancellation (PNC) algorithm. Vertical cavity surface emitting lasers (VCSELs) with approx......In this paper we experimentally demonstrate a novel, high phase-noise tolerant, optical dual polarization (DP) quadrature phase-shift keying (QPSK) communication system based on pilot-tone-aided phase noise cancellation (PNC) algorithm. Vertical cavity surface emitting lasers (VCSELs...

  12. Experimental teaching reforms of optical fiber communication based on general education

    Science.gov (United States)

    Lan, L.; Liu, S.; Zhou, J. H.; Peng, Z. M.

    2017-08-01

    It's necessary that higher education experimental teaching reforms on the basis of general education. This paper put forward the experimental teaching reform mode of optical fiber communication in the context of general education. With some reform measures such as improving the experimental content, enriching the experimental style, modifying the experimental teaching method, and adjusting the evaluation method of experimental teaching, the concept of general education is put throughout the experimental teaching of optical fiber communication. In this way, it facilitates the development of students and improvement of experimental teaching quality.

  13. Optimization of Wireless Optical Communication System Based on Augmented Lagrange Algorithm

    International Nuclear Information System (INIS)

    He Suxiang; Meng Hongchao; Wang Hui; Zhao Yanli

    2011-01-01

    The optimal model for wireless optical communication system with Gaussian pointing loss factor is studied, in which the value of bit error probability (BEP) is prespecified and the optimal system parameters is to be found. For the superiority of augmented Lagrange method, the model considered is solved by using a classical quadratic augmented Lagrange algorithm. The detailed numerical results are reported. Accordingly, the optimal system parameters such as transmitter power, transmitter wavelength, transmitter telescope gain and receiver telescope gain can be established, which provide a scheme for efficient operation of the wireless optical communication system.

  14. Simultaneous measurement of group refractive index and thickness of optical samples using optical coherence tomography

    International Nuclear Information System (INIS)

    Cheng, Hsu-Chih; Liu, Yi-Cheng

    2010-01-01

    Optical coherence tomography (OCT), based on a Michelson interferometer and utilizing low coherence light as the optical source, is a novel technique for the noninvasive imaging of optical scattering media. A simple OCT scheme based on a 3x3 fiber coupler is presented for the simultaneous measurement of the refractive index and thickness of optical samples. The proposed system enables the refractive index and thickness to be determined without any prior knowledge of the sample parameters and is characterized by a simple and compact configuration, a straightforward measurement procedure, and a low cost. The feasibility of the proposed approach is demonstrated experimentally using BK7 and B270 optical glass samples.

  15. Application condition of optical communication technique in the nuclear power plants

    International Nuclear Information System (INIS)

    Sakurai, Jun

    1999-01-01

    As the optical communication technique can process rapidly a lot of information and exclude perfectly error action due to noise, it is adopted gradually to commercial and company communications (containing operational managements in large scale facilities) in worldwide scale in stead of conventional communication technique (containing operational controls and measurements). In application to the nuclear power plants, as forming not only change in properties but also deterioration due to radiation damage in many cases of exposure to various types of radiations such as neutron, gamma-ray, and so forth in difference with conventional using environment, its using range is limited at present. In future, development of optical fibers or elements with excellent high temperature and radiation resistances usable stably at reactor core for a long time is essential. The regular application of the optical communication technique at the nuclear power plants begins just now, which is an expected field for future large development. And, for the old nuclear power plant in present operation, substitution to the optical communication technique in accompany with replace of appliances at periodical inspections will also be conducted. Its response is already required rapidly in the Tokyo Electric Power Co., Ltd.. (G.K.)

  16. Optical Fiber Connection Navigation System Using Visible Light Communication in Central Office with Economic Evaluation

    Science.gov (United States)

    Waki, Masaki; Uruno, Shigenori; Ohashi, Hiroyuki; Manabe, Tetsuya; Azuma, Yuji

    We propose an optical fiber connection navigation system that uses visible light communication for an integrated distribution module in a central office. The system realizes an accurate database, requires less skilled work to operate and eliminates human error. This system can achieve a working time reduction of up to 88.0% compared with the conventional work without human error for the connection/removal of optical fiber cords, and is economical as regards installation and operation.

  17. High-Speed Optical Wide-Area Data-Communication Network

    Science.gov (United States)

    Monacos, Steve P.

    1994-01-01

    Proposed fiber-optic wide-area network (WAN) for digital communication balances input and output flows of data with its internal capacity by routing traffic via dynamically interconnected routing planes. Data transmitted optically through network by wavelength-division multiplexing in synchronous or asynchronous packets. WAN implemented with currently available technology. Network is multiple-ring cyclic shuffle exchange network ensuring traffic reaches its destination with minimum number of hops.

  18. Configuring Web-based Media for Communication in Dispersed Project Groups

    DEFF Research Database (Denmark)

    Scheepers, Rens; Nicolajsen, Hanne Westh

    2006-01-01

    meetings, telephone) are not always viable options. Instead, computer-based communication media such as email, project intranets and extranets become surrogate conduits for day-to-day project communication and exchange of project-related content. We examined the effect of different media configurations......We studied how project groups in a pharmaceutical organization communicate project content. The project groups are geographically dispersed, and operate in different time zones. In such project environments, synchronous or geographically bounded modes of communication channels (e.g., face to face...... on the nature of content created by the project groups. We found that configuration decisions, notably the responsibility for content provision and who had access to content, influenced medium choice and the nature of communication taking place via the medium. More substantive content resulted when content...

  19. Obstacle evasion in free-space optical communications utilizing Airy beams

    Science.gov (United States)

    Zhu, Guoxuan; Wen, Yuanhui; Wu, Xiong; Chen, Yujie; Liu, Jie; Yu, Siyuan

    2018-03-01

    A high speed free-space optical communication system capable of self-bending signal transmission around line-of-sight obstacles is proposed and demonstrated. Airy beams are generated and controlled to achieve different propagating trajectories, and the signal transmission characteristics of these beams around the obstacle are investigated. Our results confirm that, by optimising their ballistic trajectories, Airy beams are able to bypass obstacles with more signal energy and thus improve the communication performance compared with normal Gaussian beams.

  20. Multi-Aperture Digital Coherent Combining for Free-Space Optical Communication Receivers

    Science.gov (United States)

    2016-04-21

    emulated by a cascade of fiber beam splitters . Fig. 4(a) depicts the transmitter, which consisted of two cascaded Mach- Zehnder modulators (MZMs) that...Sons, Inc., Hoboken, New Jersey, 2006). 5. D. O. Caplan, "Laser communication transmitter and receiver design ," J. Opt. Fiber. Commun. 4(4-5), 225...and A. E. Willner, eds. (Elsevier, 2013). 7. S. B. Alexander, Optical Communication Receiver Design (SPIE, 1997). 8. D. M. Boroson, "A survey of

  1. A review on channel models in free space optical communication systems

    Science.gov (United States)

    Anbarasi, K.; Hemanth, C.; Sangeetha, R. G.

    2017-12-01

    Free Space Optical communication (FSO) is a wireless communication technology which uses light to transmit the data in free space. FSO has advantages like unlicensed spectrum and higher bandwidth. In this paper FSO system merits and demerits, challenges in FSO, and various channel models are discussed. To mitigate the turbulence in FSO the mitigation techniques like relaying, diversity schemes and adopting different modulation techniques used in different channels are discussed and its performance comparison is given.

  2. BRIEF COMMUNICATIONS: Optically pumped ultraviolet BR2 laser

    Science.gov (United States)

    Kamrukov, A. S.; Kozlov, N. P.; Protasov, Yu S.; Ushmarov, E. Yu

    1989-12-01

    A report is given of lasing achieved for the first time in optically pumped molecular bromine (D' 3Π2g→A' 3π2u, λL approx 292 nm). It was pumped by thermal vacuum ultraviolet radiation emitted by plasmadynamic discharges of magnetoplasma compressors, formed directly in the laser active medium. An output energy of ~ 1.1 J was obtained per laser pulse of ~ 5-μs duration from a Br2:Ar approx 1:450 active mixture at a pressure of ~ 4 atm. A comparison was made of the experimental output parameters of optically pumped Br2, I2, and XeF (B-X) lasers when their geometries and excitation energies were identical.

  3. On the passive probing of fiber optic quantum communication channels

    International Nuclear Information System (INIS)

    Korol'kov, A. V.; Katamadze, K. G.; Kulik, S. P.; Molotkov, S. N.

    2010-01-01

    Avalanche photodetectors based on InGaAs:P are the most sensitive and only detectors operating in the telecommunication wavelength range 1.30-1.55 μm in the fiber optic quantum cryptography systems that can operate in the single photon count mode. In contrast to the widely used silicon photodetectors for wavelengths up to 1 μm operating in a waiting mode, these detectors always operate in a gated mode. The production of an electron-hole pair in the process of the absorption of a photon and the subsequent appearance of an avalanche of carriers can be accompanied by the inverse processes of the recombination and emission of photons. Such a backward emission can present a potential serious problem for the stability of fiber optic quantum cryptography systems against passive probing. The results of analyzing the detection of backscattered radiation are reported. The probability of such an emission has been estimated.

  4. Optical Communications With A Geiger Mode APD Array

    Science.gov (United States)

    2016-02-09

    practical performance of a Geiger mode avalanche photodiode ( GM -APD, or Geiger mode APD) array for use in optical com- munications systems. I designed and...signal quality in the first half of the frame. These shorter reset times also did not offer any advantage in the maximum number of counts able to be...pattern was advantageous for the modifications being made in post-processing on the benchmark data. In particular, this allowed post-processing results

  5. Ultra-wideband indoor communications using optical technology

    OpenAIRE

    Mirshafiei, Mehrdad

    2013-01-01

    La communication ultra large bande (UWB) a attiré une énorme quantité de recherches ces dernières années, surtout après la présentation du masque spectral de US Federal Communications Commission (FCC). Les impulsions ultra-courtes permettent de très hauts débits de faible puissance tout en éliminant les interférences avec les systèmes existants à bande étroite. La faible puissance, cependant, limite la portée de propagation des radios UWB à quelques mètres pour la transmission sans fil à l’in...

  6. Multiple-User Quantum Information Theory for Optical Communication Channels

    Science.gov (United States)

    2008-06-01

    to this day. He later encouraged (and trained) me to participate in the Physics Olympiad, which led me to make it through all the levels of selection...optimal, homodyne, and hetero- dyne reception versus transmitter power P , with P0 ≡ 2π~c2L2/ AtAr used for the reference power...the constraints on the available physical resources. In most communication systems, the transfer of information is done by superimposing the

  7. Accurate beacon positioning method for satellite-to-ground optical communication.

    Science.gov (United States)

    Wang, Qiang; Tong, Ling; Yu, Siyuan; Tan, Liying; Ma, Jing

    2017-12-11

    In satellite laser communication systems, accurate positioning of the beacon is essential for establishing a steady laser communication link. For satellite-to-ground optical communication, the main influencing factors on the acquisition of the beacon are background noise and atmospheric turbulence. In this paper, we consider the influence of background noise and atmospheric turbulence on the beacon in satellite-to-ground optical communication, and propose a new locating algorithm for the beacon, which takes the correlation coefficient obtained by curve fitting for image data as weights. By performing a long distance laser communication experiment (11.16 km), we verified the feasibility of this method. Both simulation and experiment showed that the new algorithm can accurately obtain the position of the centroid of beacon. Furthermore, for the distortion of the light spot through atmospheric turbulence, the locating accuracy of the new algorithm was 50% higher than that of the conventional gray centroid algorithm. This new approach will be beneficial for the design of satellite-to ground optical communication systems.

  8. Nurses' perceptions and experiences of communication in the operating theatre: a focus group interview

    Science.gov (United States)

    Nestel, Debra; Kidd, Jane

    2006-01-01

    Abstract Nurses' perceptions and experiences of communication in the operating theatre: a focus group interview Background Communication programmes are well established in nurse education. The focus of programmes is most often on communicating with patients with less attention paid to inter-professional communication or skills essential for working in specialised settings. Although there are many anecdotal reports of communication within the operating theatre, there are few empirical studies. This paper explores communication behaviours for effective practice in the operating theatre as perceived by nurses and serves as a basis for developing training. Methods A focus group interview was conducted with seven experienced theatre nurses from a large London teaching hospital. The interview explored their perceptions of the key as well as unique features of effective communication skills in the operating theatre. Data was transcribed and thematically analysed until agreement was achieved by the two authors. Results There was largely consensus on the skills deemed necessary for effective practice including listening, clarity of speech and being polite. Significant influences on the nature of communication included conflict in role perception and organisational issues. Nurses were often expected to work outside of their role which either directly or indirectly created barriers for effective communication. Perceptions of a lack of collaborative team effort also influenced communication. Conclusion Although fundamental communication skills were identified for effective practice in the operating theatre, there were significant barriers to their use because of confusion over clarity of roles (especially nurses' roles) and the implications for teamwork. Nurses were dissatisfied with several aspects of communication. Future studies should explore the breadth and depth of this dissatisfaction in other operating theatres, its impact on morale and importantly on patient safety

  9. Moving on in life after intensive care--partners' experience of group communication.

    Science.gov (United States)

    Ahlberg, Mona; Bäckman, Carl; Jones, Christina; Walther, Sten; Hollman Frisman, Gunilla

    2015-09-01

    Partners have a burdensome time during and after their partners' intensive care period. They may appear to be coping well outwardly but inside feel vulnerable and lost. Evaluated interventions for partners on this aspect are limited. The aim of this study was to describe the experience of participating in group communication with other partners of former intensive care patients. The study has a descriptive intervention-based design where group communication for partners of former, surviving intensive care unit (ICU) patients was evaluated. A strategic selection was made of adult partners to former adult intensive care patients (n = 15), 5 men and 10 women, aged 37-89 years. Two group communication sessions lasting 2 h were held at monthly intervals with three to five partners. The partners later wrote, in a notebook, about their feelings of participating in group communications. To deepen the understanding of the impact of the sessions, six of the partners were interviewed. Content analysis was used to analyse the notebooks and the interviews. Three categories were identified: (1) Emotional impact, the partners felt togetherness and experienced worries and gratitude, (2) Confirmation, consciousness through insight and reflection and (3) The meeting design, group constellation and recommendation to participate in group communication. Partners of an intensive care patient are on a journey, constantly trying to adapt to the new situation and find new strategies to ever-changing circumstances. Group communications contributed to togetherness and confirmation. To share experiences with others is one way for partners to be able to move forward in life. Group communication with other patients' partners eases the process of going through the burden of being a partner to an intensive care patient. Group communications needs to be further developed and evaluated to obtain consensus and evidence for the best practice. © 2015 British Association of Critical Care Nurses.

  10. Shared reality in intergroup communication: Increasing the epistemic authority of an out-group audience.

    Science.gov (United States)

    Echterhoff, Gerald; Kopietz, René; Higgins, E Tory

    2017-06-01

    Communicators typically tune messages to their audience's attitude. Such audience tuning biases communicators' memory for the topic toward the audience's attitude to the extent that they create a shared reality with the audience. To investigate shared reality in intergroup communication, we first established that a reduced memory bias after tuning messages to an out-group (vs. in-group) audience is a subtle index of communicators' denial of shared reality to that out-group audience (Experiments 1a and 1b). We then examined whether the audience-tuning memory bias might emerge when the out-group audience's epistemic authority is enhanced, either by increasing epistemic expertise concerning the communication topic or by creating epistemic consensus among members of a multiperson out-group audience. In Experiment 2, when Germans communicated to a Turkish audience with an attitude about a Turkish (vs. German) target, the audience-tuning memory bias appeared. In Experiment 3, when the audience of German communicators consisted of 3 Turks who all held the same attitude toward the target, the memory bias again appeared. The association between message valence and memory valence was consistently higher when the audience's epistemic authority was high (vs. low). An integrative analysis across all studies also suggested that the memory bias increases with increasing strength of epistemic inputs (epistemic expertise, epistemic consensus, and audience-tuned message production). The findings suggest novel ways of overcoming intergroup biases in intergroup relations. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  11. Numerical models and experiment of air flow in a simulation box for optical wireless communications

    Directory of Open Access Journals (Sweden)

    Latal Jan

    2016-01-01

    Full Text Available In this article, the authors focused on real measurements of mechanical turbulence generated by ventilators in the simulation box for Optical Wireless Communications. The mechanical turbulences disturb the optical beam that propagates along the central axis of the simulation box. The aim of authors is to show the effect of mechanical turbulence on optical beams at different heights in the simulation box. In the Ansys Fluent, we created numerical models which were then compared with real measurements. Authors compared the real and numerical models according to statistical methods.

  12. Some Practical Issues in the Design and Implementation of Group Communication Services

    National Research Council Canada - National Science Library

    Mishra, Shivakant

    2000-01-01

    The main objective of the proposed research was to investigate four important practical issues in the understanding, design, and implementation of group communication services. These issues were (1) Performance...

  13. Using Electronic Communication Tools in Online Group Activities to Develop Collaborative Learning Skills

    Science.gov (United States)

    Khalil, Hanan; Ebner, Martin

    2017-01-01

    The purpose of this study was to investigate the effect of using synchronous and asynchronous communication tools in online group activities to develop collaborative learning skills. An experimental study was implemented on a sample of faculty of education students in Mansoura University. The sample was divided into two groups, a group studied…

  14. Student laboratory experiments exploring optical fibre communication systems, eye diagrams, and bit error rates

    Science.gov (United States)

    Walsh, Douglas; Moodie, David; Mauchline, Iain; Conner, Steve; Johnstone, Walter; Culshaw, Brian

    2005-06-01

    Optical fibre communications has proved to be one of the key application areas, which created, and ultimately propelled the global growth of the photonics industry over the last twenty years. Consequently the teaching of the principles of optical fibre communications has become integral to many university courses covering photonics technology. However to reinforce the fundamental principles and key technical issues students examine in their lecture courses and to develop their experimental skills, it is critical that the students also obtain hands-on practical experience of photonics components, instruments and systems in an associated teaching laboratory. In recognition of this need OptoSci, in collaboration with university academics, commercially developed a fibre optic communications based educational package (ED-COM). This educator kit enables students to; investigate the characteristics of the individual communications system components (sources, transmitters, fibre, receiver), examine and interpret the overall system performance limitations imposed by attenuation and dispersion, conduct system design and performance analysis. To further enhance the experimental programme examined in the fibre optic communications kit, an extension module to ED-COM has recently been introduced examining one of the most significant performance parameters of digital communications systems, the bit error rate (BER). This add-on module, BER(COM), enables students to generate, evaluate and investigate signal quality trends by examining eye patterns, and explore the bit-rate limitations imposed on communication systems by noise, attenuation and dispersion. This paper will examine the educational objectives, background theory, and typical results for these educator kits, with particular emphasis on BER(COM).

  15. Discussion and group work design in O2O teaching of applied optics: questions, strategies and extending

    Science.gov (United States)

    Li, Xiaotong; Cen, Zhaofeng; Liu, Xiangdong; Zheng, Zhenrong

    2017-08-01

    Applied optics course in Zhejiang University is a National Excellent Resource Sharing Course in China, and the online to offline teaching strategies have been implemented and shared with dozens of universities and colleges in China. Discussion is an important activity in teaching. In this paper our main consideration is designing the discussion questions and group works so as to develop the students' critical thinking, cooperative and sharing spirits, and communication abilities in the cosmopolitan era. Typical questions that connect different chapters and help the students to understand the relationship between each sub-system in both field of view and aperture are given for discussion. We inspire the students to complete group works such as ray trace programming by cooperation and then make presentations. All of these create a circumstance for sharing thoughts and developing intelligence and knowledge. A poll shows that the students pay more attention to optical design than before and have made progress in conversation and cooperation.

  16. Communication constraints, indexical countermeasures, and crew configuration effects in simulated space-dwelling groups

    Science.gov (United States)

    Hienz, Robert D.; Brady, Joseph V.; Hursh, Steven R.; Banner, Michele J.; Gasior, Eric D.; Spence, Kevin R.

    2007-02-01

    Previous research with groups of individually isolated crews communicating and problem-solving in a distributed interactive simulation environment has shown that the functional interchangeability of available communication channels can serve as an effective countermeasure to communication constraints. The present report extends these findings by investigating crew performance effects and psychosocial adaptation following: (1) the loss of all communication channels, and (2) changes in crew configuration. Three-person crews participated in a simulated planetary exploration mission that required identification, collection, and analysis of geologic samples. Results showed that crews developed and employed discrete navigation system operations that served as functionally effective communication signals (i.e., “indexical” or “deictic” cues) in generating appropriate crewmember responses and maintaining performance effectiveness in the absence of normal communication channels. Additionally, changes in crew configuration impacted both performance effectiveness and psychosocial adaptation.

  17. All-optical two-way relaying free-space optical communications for HAP-based broadband backhaul networks

    Science.gov (United States)

    Vu, Minh Q.; Nguyen, Nga T. T.; Pham, Hien T. T.; Dang, Ngoc T.

    2018-03-01

    High-altitude platforms (HAPs) are flexible, non-pollutant and cost-effective infrastructures compared to satellite or old terrestrial systems. They are being researched and developed widely in Europe, USA, Japan, Korea, and so on. However, the current limited data rates and the overload of radio frequency (RF) spectrum are problems which the developers for HAPs are confronting because most of them use RF links to communicate with the ground stations (GSs) or each other. In this paper, we propose an all-optical two-way half-duplex relaying free-space optical (FSO) communication for HAP-based backhaul networks, which connect the base transceiver station (BTS) to the core network (CN) via a single HAP. Our proposed backhaul solution can be deployed quickly and flexibly for disaster relief and for serving users in both urban environments and remote areas. The key subsystem of HAP is an optical regenerate-and-forward (ORF) equipped with an optical hard-limiter (OHL) and an optical XOR gate to perform all-optical processing and help mitigate the background noise. In addition, two-way half-duplex relaying can be provided thanks to the use of network coding scheme. The closed-form expression for the bit error rate (BER) of our proposed system under the effect of path loss, atmospheric turbulence, and noise induced by the background light is formulated. The numerical results are demonstrated to prove the feasibility of our proposed system with the verification by using Monte-Carlo (M-C) simulations.

  18. Optical technologies for data communication in large parallel systems

    International Nuclear Information System (INIS)

    Ritter, M B; Vlasov, Y; Kash, J A; Benner, A

    2011-01-01

    Large, parallel systems have greatly aided scientific computation and data collection, but performance scaling now relies on chip and system-level parallelism. This has happened because power density limits have caused processor frequency growth to stagnate, driving the new multi-core architecture paradigm, which would seem to provide generations of performance increases as transistors scale. However, this paradigm will be constrained by electrical I/O bandwidth limits; first off the processor card, then off the processor module itself. We will present best-estimates of these limits, then show how optical technologies can help provide more bandwidth to allow continued system scaling. We will describe the current status of optical transceiver technology which is already being used to exceed off-board electrical bandwidth limits, then present work on silicon nanophotonic transceivers and 3D integration technologies which, taken together, promise to allow further increases in off-module and off-card bandwidth. Finally, we will show estimated limits of nanophotonic links and discuss breakthroughs that are needed for further progress, and will speculate on whether we will reach Exascale-class machine performance at affordable powers.

  19. Optical technologies for data communication in large parallel systems

    Energy Technology Data Exchange (ETDEWEB)

    Ritter, M B; Vlasov, Y; Kash, J A [IBM T.J. Watson Research Center, Yorktown Heights, NY (United States); Benner, A, E-mail: mritter@us.ibm.com [IBM Poughkeepsie, Poughkeepsie, NY (United States)

    2011-01-15

    Large, parallel systems have greatly aided scientific computation and data collection, but performance scaling now relies on chip and system-level parallelism. This has happened because power density limits have caused processor frequency growth to stagnate, driving the new multi-core architecture paradigm, which would seem to provide generations of performance increases as transistors scale. However, this paradigm will be constrained by electrical I/O bandwidth limits; first off the processor card, then off the processor module itself. We will present best-estimates of these limits, then show how optical technologies can help provide more bandwidth to allow continued system scaling. We will describe the current status of optical transceiver technology which is already being used to exceed off-board electrical bandwidth limits, then present work on silicon nanophotonic transceivers and 3D integration technologies which, taken together, promise to allow further increases in off-module and off-card bandwidth. Finally, we will show estimated limits of nanophotonic links and discuss breakthroughs that are needed for further progress, and will speculate on whether we will reach Exascale-class machine performance at affordable powers.

  20. All-optical control of group velocity dispersion in tellurite photonic crystal fibers.

    Science.gov (United States)

    Liu, Lai; Tian, Qijun; Liao, Meisong; Zhao, Dan; Qin, Guanshi; Ohishi, Yasutake; Qin, Weiping

    2012-12-15

    We demonstrate all-optical control of group velocity dispersion (GVD) via optical Kerr effect in highly nonlinear tellurite photonic crystal fibers. The redshift of the zero-dispersion wavelength is over 307 nm, measured by soliton self-frequency shift cancellation, when the pump peak power of a 1.56 μm femtosecond fiber laser is increased to 11.6 kW. The all-optical control of GVD not only offers a new platform for constructing all-optical-control photonic devices but also promises a new class of experiments in nonlinear fiber optics and light-matter interactions.

  1. Performance Analysis of Free-Space Optical Communication Systems With Multiuser Diversity Over Atmospheric Turbulence Channels

    KAUST Repository

    Yang, Liang; Gao, Xiqi; Alouini, Mohamed-Slim

    2014-01-01

    Free-space optical (FSO) communication has become a cost-effective method to provide high data rates. However, the turbulence-induced fading limits its application to short-range applications. To address this, we propose a multiuser diversity (MD

  2. 78 FR 77166 - Certain Optoelectronic Devices for Fiber Optic Communications, Components Thereof, and Products...

    Science.gov (United States)

    2013-12-20

    ... INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-860] Certain Optoelectronic Devices for Fiber Optic Communications, Components Thereof, and Products Containing the Same; Notice of Request for Statements on the Public Interest AGENCY: U.S. International Trade Commission. ACTION: Notice. SUMMARY...

  3. Replacing the soft-decision FEC limit paradigm in the design of optical communication systems

    NARCIS (Netherlands)

    Alvarado, A.; Agrell, E.; Lavery, D.; Maher, R.; Bayvel, P.

    2016-01-01

    The FEC limit paradigm is the prevalent practice for designing optical communication systems to attain a certain bit error rate (BER) without forward error correction (FEC). This practice assumes that there is an FEC code that will reduce the BER after decoding to the desired level. In this paper,

  4. Information rates and post-FEC BER prediction in optical fiber communications

    NARCIS (Netherlands)

    Alvarado, Alex

    2017-01-01

    Information-theoretic metrics to analyze optical fiber communications systems with binary and nonbinary soft-decision FEC are reviewed. The numerical evaluation of these metrics in both simulations and experiments is also discussed. Ready-to-use closed-form approximations are presented.

  5. Dual-polarization nonlinear Fourier transform-based optical communication system

    DEFF Research Database (Denmark)

    Gaiarin, Simone; Perego, A. M.; da Silva, Edson Porto

    2018-01-01

    communication could potentially overcome these limitations. It relies on a mathematical technique called “nonlinear Fourier transform (NFT)” to exploit the “hidden” linearity of the nonlinear Schrödinger equation as the master model for signal propagation in an optical fiber. We present here the theoretical...

  6. Reduced complexity digital back-propagation methods for optical communication systems

    NARCIS (Netherlands)

    Napoli, A.; Maalej, Z.; Sleiffer, V.A.J.M.; Kuschnerov, M.; Rafique, D.; Timmers, E.; Spinnler, B.; Rahman, T.; Coelho, L.D.; Hanik, N.

    2014-01-01

    Next-generation optical communication systems will continue to push the ( bandwidth $cdot$ distance) product towards its physical limit. To address this enormous demand, the usage of digital signal processing together with advanced modulation formats and coherent detection has been proposed to

  7. GRAS: A Group Reliant Authentication Scheme for V2V Communication in VANET

    Directory of Open Access Journals (Sweden)

    Auxeeliya Jesudoss

    2013-08-01

    Full Text Available Unlike fixed or wired networks, mobile ad-hoc networks pose a number of challenges for peer-to-peer communication due to their dynamic nature. This paper presents a novel framework for vehicleto- vehicle communication controlled and facilitated by a group leader within a group of vehicles. A communication model for a pure ad-hoc network is developed with much concern about the privacy and security of the system, for the ease of effective communication between vehicles with a reduced communication and computational overhead when no fixed infrastructure is present in the roadsides. In the proposed protocol, vehicles within a radio frequency form a group. They elect their leader based on some criteria who is then responsible for generating a group public and private key pair. Each vehicle is equipped with a tamper resistant OBU which is capable of generating public/private keys pairs and also self-certifies the generated keys based on one way hash chaining technique. Any vehicle joins the group communicates the group leader, authenticates itself to obtain the group key. Later, the vehicle uses the group key to send traffic related messages to the group leader who is responsible for batch verifying the authenticity of the message from different sources and one hop broadcast them to reduce the computation overhead on message verification in each vehicle. In addition, our scheme adopts the k-anonymity approach to protect user identity privacy, where an attacker cannot associate a message with the sending vehicle. Extensive analysis and simulations show that the proposed architecture provides an efficient and fully self organized system management for car-to-car communication without the need of any external infrastructure.

  8. Acousto-optic pointing and tracking systems for free-space laser communications

    Science.gov (United States)

    Nikulin, V.; Khandekar, R.; Sofka, J.; Tartakovsky, G.

    2005-08-01

    Implementation of long-range laser communication systems holds great promise for high-bandwidth applications. They are viewed as a technology that in the nearest future will handle most of the "last mile" communication traffic for the individual subscribers, corporate offices, military, and possibly deep space probes. Indeed, lasers allow for concentration of energy within tightly focused beams and narrow spectral interval, thus offering high throughput, information security, weight and size of components and power requirements that could not be matched by RF systems. However, the advantages of optical communication systems come in the same package with several major challenges. In particular, high data rates should be complemented by high-precision wide-bandwidth position control of a laser beam. In many applications the ability to maintain a link is affected by the complex maneuvers performed by mobile communication platforms, resident vibrations, and atmospheric effects. The search for the most effective and reliable way to shape and steer the laser beam is an on-going effort. This paper is focused on the application of acousto-optic technology as an alternative to electro-mechanical devices. With realization that an acousto-optic Bragg cell is only a component of the entire communication system, which should perform complex tasks of acquisition, pointing, and tracking of the remote terminal, we present an attempt to consider this problem from the "systems" point of view.

  9. Methods and Devices for Space Optical Communications Using Laser Beams

    Science.gov (United States)

    Goorjian, Peter M. (Inventor)

    2018-01-01

    Light is used to communicate between objects separated by a large distance. Light beams are received in a telescopic lens assembly positioned in front of a cat's-eye lens. The light can thereby be received at various angles to be output by the cat's-eye lens to a focal plane of the cat's-eye lens, the position of the light beams upon the focal plane corresponding to the angle of the beam received. Lasers and photodetectors are distributed along this focal plane. A processor receives signals from the photodetectors, and selectively signal lasers positioned proximate the photodetectors detecting light, in order to transmit light encoding data through the cat's-eye lens and also through a telescopic lens back in the direction of the received light beams, which direction corresponds to a location upon the focal plane of the transmitting lasers.

  10. Interference-Assisted Techniques for Transmission and Multiple Access in Optical Communications

    Science.gov (United States)

    Guan, Xun

    Optical communications can be in wired or wireless form. Fiber optics communication (FOC) connects transmitters and receivers with optical fiber. Benefiting from its high bandwidth, low cost per volume and stability, it gains a significant market share in long-haul networks, access networks and data centers. Meanwhile, optical wireless communication (OWC) is also emerging as a crucial player in the communication market. In OWC, free-space optical communication (FSO) and visible light communication (VLC) are being studied and commercially deployed extensively. Interference is a common phenomenon in multi-user communication systems. In both FOC and OWC, interference has long been treated as a detrimental effect. However, it could also be beneficial to system applications. The effort of harnessing interference has spurred numerous innovations. Interesting examples are physical-layer network coding (PNC) and non-orthogonal multiple access (NOMA). The first part of this thesis in on the topic of PNC. PNC was firstly proposed in wireless communication to improve the throughput of a two-way relay network (TWRN). As a variation of network coding (NC), PNC turns the common channel interference (CCI) as a natural network coding operation. In this thesis, PNC is introduced into optical communication. Three schemes are proposed in different scenarios. Firstly, PNC is applied to a coherent optical orthogonal frequency division multiplexing (CO-OFDM) system so as to improve the throughput of the multicast network. The optical signal to noise ratio (OSNR) penalty is quite low. Secondly, we investigate the application of PNC in an OFDM passive optical network (OFDM-PON) supporting heterogeneous services. It is found that only minor receiver power penalties are observed to realize PNC-based virtual private networks (VPN), both in the wired service part and the wireless service part in an OFDM-PON with heterogeneous services. Thirdly, we innovate relay-based visible light

  11. 20-meter underwater wireless optical communication link with 15 Gbps data rate

    KAUST Repository

    Shen, Chao

    2016-10-24

    The video streaming, data transmission, and remote control in underwater call for high speed (Gbps) communication link with a long channel length (∼10 meters). We present a compact and low power consumption underwater wireless optical communication (UWOC) system utilizing a 450-nm laser diode (LD) and a Si avalanche photodetector. With the LD operating at a driving current of 80 mA with an optical power of 51.3 mW, we demonstrated a high-speed UWOC link offering a data rate up to 2 Gbps over a 12-meter-long, and 1.5 Gbps over a record 20-meter-long underwater channel. The measured bit-error rate (BER) are 2.8 × 10-5, and 3.0 × 10-3, respectively, which pass well the forward error correction (FEC) criterion. © 2016 Optical Society of America.

  12. High-Capacity Hybrid Optical Fiber-Wireless Communications Links in Access Networks

    DEFF Research Database (Denmark)

    Pang, Xiaodan

    of broadband services access. To realize the seamless convergence between the two network segments, the lower capacity of wireless systems need to be increased to match the continuously increasing bandwidth of fiber-optic systems. The research works included in this thesis are devoted to experimental...... investigations of photonic-wireless links with record high capacities to fulfill the requirements of next generation hybrid optical fiber-wireless access networks. The main contributions of this thesis have expanded the state-of-the-art in two main areas: high speed millimeter-wave (mm-wave) communication links......Integration between fiber-optic and wireless communications systems in the "last mile" access networks is currently considered as a promising solution for both service providers and users, in terms of minimizing deployment cost, shortening upgrading period and increasing mobility and flexibility...

  13. Opals: Mission System Operations Architecture for an Optical Communications Demonstration on the ISS

    Science.gov (United States)

    Abrahamson, Matthew J.; Sindiy, Oleg V.; Oaida, Bogdan V.; Fregoso, Santos; Bowles-Martinez, Jessica N.; Kokorowski, Michael; Wilkerson, Marcus W.; Konyha, Alexander L.

    2014-01-01

    In April of 2014, the Optical PAyload for Lasercomm Science (OPALS) Flight System (FS) launched to the International Space Station (ISS) to demonstrate space-to-ground optical communications. During a planned 90-day baseline mission, the OPALS FS will downlink high quality, short duration videos to the Optical Communications Telescope Laboratory (OCTL) ground station in Wrightwood, California. Interfaces to the ISS payload operations infrastructure have been established to facilitate activity planning, hazardous laser operations, commanding, and telemetry transmission. In addition, internal processes, such as pointing prediction and data processing, satisfy the technical requirements of the mission. The OPALS operations team participates in Operational Readiness Tests (ORTs) with external partners to exercise coordination processes and train for the overall mission. The ORTs have provided valuable insight into operational considerations for the instrument on the ISS.

  14. 20-meter underwater wireless optical communication link with 15 Gbps data rate

    KAUST Repository

    Shen, Chao; Guo, Yong; Oubei, Hassan M.; Ng, Tien Khee; Liu, Guangyu; Park, Kihong; Ho, Kang-Ting; Alouini, Mohamed-Slim; Ooi, Boon S.

    2016-01-01

    The video streaming, data transmission, and remote control in underwater call for high speed (Gbps) communication link with a long channel length (∼10 meters). We present a compact and low power consumption underwater wireless optical communication (UWOC) system utilizing a 450-nm laser diode (LD) and a Si avalanche photodetector. With the LD operating at a driving current of 80 mA with an optical power of 51.3 mW, we demonstrated a high-speed UWOC link offering a data rate up to 2 Gbps over a 12-meter-long, and 1.5 Gbps over a record 20-meter-long underwater channel. The measured bit-error rate (BER) are 2.8 × 10-5, and 3.0 × 10-3, respectively, which pass well the forward error correction (FEC) criterion. © 2016 Optical Society of America.

  15. Mobile free-space optical communications: a feasibility study of various battlefield scenarios

    Science.gov (United States)

    Harris, Alan; Al-Akkoumi, Mouhammad K.; Sluss, James J., Jr.

    2012-06-01

    Free Space Optics (FSO) technology was originally envisioned to be a viable solution for the provision of high bandwidth optical connectivity in the last mile of today's telecommunications infrastructure. Due to atmospheric limitations inherent to FSO technology, FSO is now widely envisioned as a solution for the provision of high bandwidth, temporary mobile communications links. The need for FSO communications links will increase as mobility is introduced to this technology. In this paper, a theoretical solution for adding mobility to FSO communication links is introduced. Three-dimensional power estimation studies are presented to represent mobile FSO transmission under various weather conditions. Three wavelengths, 0.85, 1.55 and 10 um, are tested and compared to illustrate the pros and cons of each source wavelength used for transmission, depending on prevalent weather conditions and atmospheric turbulence conditions. A simulation analysis of the transmission properties of the source wavelengths used in the study is shown.

  16. Non-Mechanical Beam Steering in Free-Space Optical Communication Transceivers

    Science.gov (United States)

    Shortt, Kevin

    Free-space optical communications systems are a rapidly growing field as they carry many of the advantages of traditional fibre-based communications systems without the added investment of installing complex infrastructure. Moreover, these systems are finding key niches in mobile platforms in order to take advantage of the increased bandwidth over traditional RF systems. Of course, the inevitable problem of tracking arises when dealing with mobile stations. To compound the problem in the case of communications to low Earth or geosynchronous orbits, FSOC systems typically operate with tightly confined beams over great distances often requiring pointing accuracies on the order of micro-radians or smaller. Mechanisms such as gimbal mounts and fine-steering mirrors are the usual candidates for platform stabilization, however, these clearly have substantial power requirements and inflate the mass of the system. Spatial light modulators (also known as optical phased arrays), on the other hand, offer a suitable alternative for beam-pointing stabilization. Some of the advantages of spatial light modulators over fine-steering mirrors include programmable multiple simultaneous beams, dynamic focus/defocus and moderate to excellent optical power handling capability. This thesis serves as an investigation into the implementation of spatial light modulators as a replacement for traditional fine-steering mirrors in the fine-pointing subsystem. In particular, pointing accuracy and scanning ability will be highlighted as performance metrics in the context of a variety of communication scenarios. Keywords: Free-space optical communications, beam steering, fine-steering mirror, spatial light modulator, optical phased array.

  17. The JPL optical communications telescope laboratory (OCTL) test bed for the future optical Deep Space Network

    Science.gov (United States)

    Wilson, K. E.; Page, N.; Wu, J.; Srinivasan, M.

    2003-01-01

    Relative to RF, the lower power-consumption and lower mass of high bandwidth optical telecommunications make this technology extremely attractive for returning data from future NASA/JPL deep space probes.

  18. Using Web-Based, Group Communication Systems to Support Case Study Learning at a Distance

    Directory of Open Access Journals (Sweden)

    Liam Rourke

    2002-10-01

    Full Text Available This study explored the capacity of Web-based, group communication systems to support case-based teaching and learning. Eleven graduate students studying at a distance were divided into three groups to collaborate on a case study using either a synchronous voice, an asynchronous voice, or a synchronous text communication system. Participants kept a detailed log of the time they spent on various activities, wrote a 1,500-word reflection on their experience, and participated in a group interview. Analysis of these data reveals that each group supplemented the system that had been assigned to them with additional communication systems in order to complete the project. Each of these systems were used strategically: email was used to share files and arrange meetings, and synchronous voice systems were used to brainstorm and make decisions. Learning achievement was high across groups and students enjoyed collaborating with others on a concrete task.

  19. Group Communication Training for Young People with Combined Visual and Hearing Impairments

    Directory of Open Access Journals (Sweden)

    Khokhlova A. Yu.

    2018-04-01

    Full Text Available The article presents the experience of the communication training for young people with visual and hearing impairments. Boys and girls aged 16–25 with simultaneous hearing and visual impairments of varying severity took part in the group trainings. The variety of means of communication used by them described, conditions of effective training work outlined. The results showed that young people with visual and hearing impairments demonstrate a fairly high level of possession of various means of communication without pronounced additional violations. Communicative needs and preferences in young people with visual and hearing impairments are age-appropriate. Communication training allows the following: to eliminate some of the objective communicative difficulties which are exists in deaf-blind people, to motivate participants to show initiative in communication, to learn new about each other. Also communicative training creates a positive experience of communication with a wider range of people. The most important result is the opportunity to talk about ones feelings in a supportive atmosphere.

  20. Advanced Electrical, Optical and Data Communication Infrastructure Development

    Energy Technology Data Exchange (ETDEWEB)

    Simon Cobb

    2011-04-30

    The implementation of electrical and IT infrastructure systems at the North Carolina Center for Automotive Research , Inc. (NCCAR) has achieved several key objectives in terms of system functionality, operational safety and potential for ongoing research and development. Key conclusions include: (1) The proven ability to operate a high speed wireless data network over a large 155 acre area; (2) Node to node wireless transfers from access points are possible at speeds of more than 50 mph while maintaining high volume bandwidth; (3) Triangulation of electronic devices/users is possible in areas with overlapping multiple access points, outdoor areas with reduced overlap of access point coverage considerably reduces triangulation accuracy; (4) Wireless networks can be adversely affected by tree foliage, pine needles are a particular challenge due to the needle length relative to the transmission frequency/wavelength; and (5) Future research will use the project video surveillance and wireless systems to further develop automated image tracking functionality for the benefit of advanced vehicle safety monitoring and autonomous vehicle control through 'vehicle-to-vehicle' and 'vehicle-to-infrastructure' communications. A specific advantage realized from this IT implementation at NCCAR is that NC State University is implementing a similar wireless network across Centennial Campus, Raleigh, NC in 2011 and has benefited from lessons learned during this project. Consequently, students, researchers and members of the public will be able to benefit from a large scale IT implementation with features and improvements derived from this NCCAR project.

  1. Optical properties of boron-group (V) hexagonal nanowires: DFT ...

    Indian Academy of Sciences (India)

    B Santhibhushan

    Advanced Materials Research Group, CNT Laboratory, ABV-Indian Institute of Information Technology and. Management, Gwalior 474 ... Published online 20 June 2017. Abstract. ... properties are highly dependent on their shape and size.

  2. Group velocity measurement using spectral interference in near-field scanning optical microscopy

    International Nuclear Information System (INIS)

    Mills, John D.; Chaipiboonwong, Tipsuda; Brocklesby, William S.; Charlton, Martin D. B.; Netti, Caterina; Zoorob, Majd E.; Baumberg, Jeremy J.

    2006-01-01

    Near-field scanning optical microscopy provides a tool for studying the behavior of optical fields inside waveguides. In this experiment the authors measure directly the variation of group velocity between different modes of a planar slab waveguide as the modes propagate along the guide. The measurement is made using the spectral interference between pulses propagating inside the waveguide with different group velocities, collected using a near-field scanning optical microscope at different points down the guide and spectrally resolved. The results are compared to models of group velocities in simple guides

  3. A Study of an Optical Lunar Surface Communications Network with High Bandwidth Direct to Earth Link

    Science.gov (United States)

    Wilson, K.; Biswas, A.; Schoolcraft, J.

    2011-01-01

    Analyzed optical DTE (direct to earth) and lunar relay satellite link analyses, greater than 200 Mbps downlink to 1-m Earth receiver and greater than 1 Mbps uplink achieved with mobile 5-cm lunar transceiver, greater than 1Gbps downlink and greater than 10 Mpbs uplink achieved with 10-cm stationary lunar transceiver, MITLL (MIT Lincoln Laboratory) 2013 LLCD (Lunar Laser Communications Demonstration) plans to demonstrate 622 Mbps downlink with 20 Mbps uplink between lunar orbiter and ground station; Identified top five technology challenges to deploying lunar optical network, Performed preliminary experiments on two of challenges: (i) lunar dust removal and (ii)DTN over optical carrier, Exploring opportunities to evaluate DTN (delay-tolerant networking) over optical link in a multi-node network e.g. Desert RATS.

  4. Group consultations in antenatal care: Patients’ perspectives on what patient-patient communication provides

    DEFF Research Database (Denmark)

    Jensen, Matilde Nisbeth; Fage-Butler, Antoinette Mary

    Background and objectives: The group consultation, where a medical professional engages simultaneously with a group of patients, is increasingly being used in healthcare encounters. Its introduction has been associated with two perceived advantages: 1) that it can provide a more economically...... in our understanding of the group consultation. Our specific focus is on interpersonal communication in group consultations, with specific focus on patient-patient communication. This paper presents findings from a research project on pregnant women’s experiences of group consultations with a midwife...... in the Danish setting. Methods: Using a sequential mixed methods design, we first performed a discourse analysis of the written materials provided to the women about the group consultations. In the second step, we interview the women about their experiences of the group consultations. Findings: The analysis...

  5. Teachers and Facebook: using online groups to improve students’ communication and engagement

    NARCIS (Netherlands)

    Rezende Da Cunha Junior, F.; van Kruistum, C.J.; van Oers, B.

    2016-01-01

    This paper reports on how teachers, from different cities in Brazil, used groups on Facebook and how communication between teachers and students was affected by using such groups. This study is framed under the Cultural Historical Activity Theory (CHAT) perspective, and is conceived from a

  6. Teachers and Facebook: Using Online Groups to Improve Students' Communication and Engagement in Education

    Science.gov (United States)

    Rezende da Cunha, Fernando, Jr.; van Kruistum, Claudia; van Oers, Bert

    2016-01-01

    This paper reports on how teachers, from different cities in Brazil, used groups on Facebook and how communication between teachers and students was affected by using such groups. This study is framed under the Cultural Historical Activity Theory (CHAT) perspective, and is conceived from a methodological background that invites participants to…

  7. Group Trust, Communication Media, and Interactivity: Toward an Integrated Model of Online Collaborative Learning

    Science.gov (United States)

    Du, Jianxia; Wang, Chuang; Zhou, Mingming; Xu, Jianzhong; Fan, Xitao; Lei, Saosan

    2018-01-01

    The present investigation examines the multidimensional relationships among several critical components in online collaborative learning, including group trust, communication media, and interactivity. Four hundred eleven university students from 103 groups in the United States responded survey items on online collaboration, interactivity,…

  8. Preparing Students for 21st Century Teamwork: Effective Collaboration in the Online Group Communication Course

    Science.gov (United States)

    Messersmith, Amber S.

    2015-01-01

    Facilitating meaningful interaction among students is a significant challenge of teaching in the online environment. This paper presents a semester-long approach that enables quality interaction among group members within undergraduate online group communication courses while experiencing the challenges of working with geographically dispersed…

  9. Social influence in computer-mediated communication : The effects of anonymity on group behavior

    NARCIS (Netherlands)

    Postmes, T; Spears, R; Sakhel, K; de Groot, D

    2001-01-01

    Two studies examined hypotheses derived from a Social Identity model of Deindividuation Effects (SIDE) as applied to social influence in computer-mediated communication (CMC) in groups. This model predicts that anonymity can increase social influence if a common group identity is salient. In a first

  10. EU-US standards harmonization task group report : feedback to ITS standards development organizations communications.

    Science.gov (United States)

    2012-11-01

    Harmonization Task Groups 1 and 3 (HTG1 and 3) were established by the EU-US International Standards Harmonization Working Group to attempt to harmonize standards (including ISO, CEN, ETSI, IEEE) on security (HTG1) and communications protocols (HTG3)...

  11. EU-US standards harmonization task group report : status of ITS communication standards.

    Science.gov (United States)

    2012-11-01

    Harmonization Task Groups 1 and 3 (HTG1 and 3) were established by the EU-US International Standards Harmonization Working Group to attempt to harmonize standards (including ISO, CEN, ETSI, IEEE) on security (HTG1) and communications protocols (HTG3)...

  12. Crossing the Communication Barrier: Facilitating Communication in Mixed Groups of Deaf and Hearing Students

    Science.gov (United States)

    Marchetti, Carol; Foster, Susan; Long, Gary; Stinson, Michael

    2012-01-01

    Teachers of introductory technical courses such as statistics face numerous challenges in the classroom, including student motivation and mathematical background, and difficulties in interpreting numerical results in context. Cooperative learning through small groups addresses many such challenges, but students for whom spoken English is not their…

  13. Silicon Nanowires for All-Optical Signal Processing in Optical Communication

    DEFF Research Database (Denmark)

    Pu, Minhao; Hu, Hao; Ji, Hua

    2012-01-01

    Silicon (Si), the second most abundant element on earth, has dominated in microelectronics for many decades. It can also be used for photonic devices due to its transparency in the range of optical telecom wavelengths which will enable a platform for a monolithic integration of optics...... and microelectronics. Silicon photonic nanowire waveguides fabricated on silicon-on-insulator (SOI) substrates are crucial elements in nano-photonic integrated circuits. The strong light confinement in nanowires induced by high index contrast SOI material enhances the nonlinear effects in the silicon nanowire core...... such as four-wave mixing (FWM) which is an imperative process for optical signal processing. Since the current mature silicon fabrication technology enables a precise dimension control on nanowires, dispersion engineering can be performed by tailoring nanowire dimensions to realize an efficient nonlinear...

  14. Differential phase-shift keying and channel equalization in free space optical communication system

    Science.gov (United States)

    Zhang, Dai; Hao, Shiqi; Zhao, Qingsong; Wan, Xiongfeng; Xu, Chenlu

    2018-01-01

    We present the performance benefits of differential phase-shift keying (DPSK) modulation in eliminating influence from atmospheric turbulence, especially for coherent free space optical (FSO) communication with a high communication rate. Analytic expression of detected signal is derived, based on which, homodyne detection efficiency is calculated to indicate the performance of wavefront compensation. Considered laser pulses always suffer from atmospheric scattering effect by clouds, intersymbol interference (ISI) in high-speed FSO communication link is analyzed. Correspondingly, the channel equalization method of a binormalized modified constant modulus algorithm based on set-membership filtering (SM-BNMCMA) is proposed to solve the ISI problem. Finally, through the comparison with existing channel equalization methods, its performance benefits of both ISI elimination and convergence speed are verified. The research findings have theoretical significance in a high-speed FSO communication system.

  15. Performance Evaluation of High Speed Multicarrier System for Optical Wireless Communication

    Science.gov (United States)

    Mathur, Harshita; Deepa, T.; Bartalwar, Sophiya

    2018-04-01

    Optical wireless communication (OWC) in the infrared and visible range is quite impressive solution, especially where radio communication face challenges. Visible light communication (VLC) uses visible light over a range of 400 and 800 THz and is a subdivision of OWC technologies. With an increasing demand for use of wireless communications, wireless access via Wi-Fi is facing many challenges especially in terms of capacity, availability, security and efficiency. VLC uses intensity modulation and direct detection (IM/DD) techniques and hence they require the signals to certainly be real valued positive sequences. These constraints pose limitation on digital modulation techniques. These limitations result in spectrum-efficiency or power-efficiency losses. In this paper, we investigate an amplitude shift keying (ASK) based orthogonal frequency division multiplexing (OFDM) signal transmission scheme using LabVIEW for VLC technology.

  16. Uncertainty communication in the Environmental Balance 2005. Results of the User Group Policy Makers

    International Nuclear Information System (INIS)

    Wardekker, J.A.; Van der Sluijs, J.P.; Janssen, P.H.M.

    2006-02-01

    In 2003 recommendations were formulated how to deal with uncertainties in scientific studies. Currently a so-called 'Styleguide for Uncertainty Communication' is under development to report on information about uncertainties. The guide is based on literature survey and knowledge from experts in the field. A group of users of the Dutch Environmental Balance 2005 was set up to communicate and inform about uncertainties with respect to the Balance [nl

  17. The Group Objective Structured Clinical Experience: building communication skills in the clinical reasoning context.

    Science.gov (United States)

    Konopasek, Lyuba; Kelly, Kevin V; Bylund, Carma L; Wenderoth, Suzanne; Storey-Johnson, Carol

    2014-07-01

    Students are rarely taught communication skills in the context of clinical reasoning training. The purpose of this project was to combine the teaching of communication skills using SPs with clinical reasoning exercises in a Group Objective Structured Clinical Experience (GOSCE) to study feasibility of the approach, the effect on learners' self-efficacy and attitude toward learning communication skills, and the effect of providing multiple sources of immediate, collaborative feedback. GOSCE sessions were piloted in Pediatrics and Medicine clerkships with students assessing their own performance and receiving formative feedback on communication skills from peers, standardized patients (SPs), and faculty. The sessions were evaluated using a retrospective pre/post-training questionnaire rating changes in self-efficacy and attitudes, and the value of the feedback. Results indicate a positive impact on attitudes toward learning communication skills and self-efficacy regarding communication in the clinical setting. Also, learners considered feedback by peers, SPs, and faculty valuable in each GOSCE. The GOSCE is an efficient and learner-centered method to attend to multiple goals of teaching communication skills, clinical reasoning, self-assessment, and giving feedback in a formative setting. The GOSCE is a low-resource, feasible strategy for experiential learning in communication skills and clinical reasoning. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  18. Optical Phase Recovery and Locking in a PPM Laser Communication Link

    Science.gov (United States)

    Aveline, David C.; Yu, Nan; Farr, William H.

    2012-01-01

    Free-space optical communication holds great promise for future space missions requiring high data rates. For data communication in deep space, the current architecture employs pulse position modulation (PPM). In this scheme, the light is transmitted and detected as pulses within an array of time slots. While the PPM method is efficient for data transmission, the phase of the laser light is not utilized. The phase coherence of a PPM optical signal has been investigated with the goal of developing a new laser communication and ranging scheme that utilizes optical coherence within the established PPM architecture and photon-counting detection (PCD). Experimental measurements of a PPM modulated optical signal were conducted, and modeling code was developed to generate random PPM signals and simulate spectra via FFT (Fast Fourier Transform) analysis. The experimental results show very good agreement with the simulations and confirm that coherence is preserved despite modulation with high extinction ratios and very low duty cycles. A real-time technique has been developed to recover the phase information through the mixing of a PPM signal with a frequency-shifted local oscillator (LO). This mixed signal is amplified, filtered, and integrated to generate a voltage proportional to the phase of the modulated signal. By choosing an appropriate time constant for integration, one can maintain a phase lock despite long dark times between consecutive pulses with low duty cycle. A proof-of-principle demonstration was first achieved with an RF-based PPM signal and test setup. With the same principle method, an optical carrier within a PPM modulated laser beam could also be tracked and recovered. A reference laser was phase-locked to an independent pulsed laser signal with low-duty-cycle pseudo-random PPM codes. In this way, the drifting carrier frequency in the primary laser source is tracked via its phase change in the mixed beat note, while the corresponding voltage feedback

  19. Nanoscale on-chip all-optical logic parity checker in integrated plasmonic circuits in optical communication range

    Science.gov (United States)

    Wang, Feifan; Gong, Zibo; Hu, Xiaoyong; Yang, Xiaoyu; Yang, Hong; Gong, Qihuang

    2016-01-01

    The nanoscale chip-integrated all-optical logic parity checker is an essential core component for optical computing systems and ultrahigh-speed ultrawide-band information processing chips. Unfortunately, little experimental progress has been made in development of these devices to date because of material bottleneck limitations and a lack of effective realization mechanisms. Here, we report a simple and efficient strategy for direct realization of nanoscale chip-integrated all-optical logic parity checkers in integrated plasmonic circuits in the optical communication range. The proposed parity checker consists of two-level cascaded exclusive-OR (XOR) logic gates that are realized based on the linear interference of surface plasmon polaritons propagating in the plasmonic waveguides. The parity of the number of logic 1s in the incident four-bit logic signals is determined, and the output signal is given the logic state 0 for even parity (and 1 for odd parity). Compared with previous reports, the overall device feature size is reduced by more than two orders of magnitude, while ultralow energy consumption is maintained. This work raises the possibility of realization of large-scale integrated information processing chips based on integrated plasmonic circuits, and also provides a way to overcome the intrinsic limitations of serious surface plasmon polariton losses for on-chip integration applications. PMID:27073154

  20. Nanoscale on-chip all-optical logic parity checker in integrated plasmonic circuits in optical communication range.

    Science.gov (United States)

    Wang, Feifan; Gong, Zibo; Hu, Xiaoyong; Yang, Xiaoyu; Yang, Hong; Gong, Qihuang

    2016-04-13

    The nanoscale chip-integrated all-optical logic parity checker is an essential core component for optical computing systems and ultrahigh-speed ultrawide-band information processing chips. Unfortunately, little experimental progress has been made in development of these devices to date because of material bottleneck limitations and a lack of effective realization mechanisms. Here, we report a simple and efficient strategy for direct realization of nanoscale chip-integrated all-optical logic parity checkers in integrated plasmonic circuits in the optical communication range. The proposed parity checker consists of two-level cascaded exclusive-OR (XOR) logic gates that are realized based on the linear interference of surface plasmon polaritons propagating in the plasmonic waveguides. The parity of the number of logic 1s in the incident four-bit logic signals is determined, and the output signal is given the logic state 0 for even parity (and 1 for odd parity). Compared with previous reports, the overall device feature size is reduced by more than two orders of magnitude, while ultralow energy consumption is maintained. This work raises the possibility of realization of large-scale integrated information processing chips based on integrated plasmonic circuits, and also provides a way to overcome the intrinsic limitations of serious surface plasmon polariton losses for on-chip integration applications.

  1. WINDING METHOD SELECTION FOR TECHNICAL IMPLEMENTATION OF FIBER OPTIC COMMUNICATION LINE FOR HIGH-SPEED OBJECT

    Directory of Open Access Journals (Sweden)

    Vyacheslav A. Loparev

    2017-07-01

    Full Text Available The paper deals with fiber-optical cable winding methods for realization of fiber-optic communication line with high-speed object. We consider possible options of coils for optical cable winding providing mobility of one of the cable ends on an object. It is shown that the choice of a winding process is caused by the need of ensuring the minimum deformation of fiber-optical micro cable in case of separation from a winding body. It is revealed that the minimum tension value and its unevenness are observed when reeling from coils with a rocket form. Design ratios for determination of winding parameters are given. It is shown that reduction of tension unevenness reduces the jumps of internal tension and probability of break and emergence of optical signal local attenuation. Decrease in internal stresses occurs due to the absence of overlapping of the coils of the underlying layers with the overlying ones. To confirm the operability and the possibility of constructive implementation of the selected winding scheme, experiments were carried out to perform rocket and other types of winding with the use of a specially designed machine model. It is shown that the application of line rocket winding enables to achieve stability when reeling a cable during the movement and excludes breaks. Attenuation of optical signal decreases due to the increase in the bend minimum radius. This phenomenon is explained by reduction of the internal stresses causing optical signal attenuation in the place of cable separation from the coil.

  2. Simulating the performance of adaptive optics techniques on FSO communications through the atmosphere

    Science.gov (United States)

    Martínez, Noelia; Rodríguez Ramos, Luis Fernando; Sodnik, Zoran

    2017-08-01

    The Optical Ground Station (OGS), installed in the Teide Observatory since 1995, was built as part of ESA efforts in the research field of satellite optical communications to test laser telecommunication terminals on board of satellites in Low Earth Orbit and Geostationary Orbit. As far as one side of the link is settled on the Earth, the laser beam (either on the uplink or on the downlink) has to bear with the atmospheric turbulence. Within the framework of designing an Adaptive Optics system to improve the performance of the Free-Space Optical Communications at the OGS, turbulence conditions regarding uplink and downlink have been simulated within the OOMAO (Object-Oriented Matlab Adaptive Optics) Toolbox as well as the possible utilization of a Laser Guide Star to measure the wavefront in this context. Simulations have been carried out by reducing available atmospheric profiles regarding both night-time and day-time measurements and by having into account possible seasonal changes. An AO proposal to reduce atmospheric aberrations and, therefore, ameliorate FSO links performance is presented and analysed in this paper

  3. Free Space Optical (FSO) Communications, Towards the Speeds of Wireline Networks

    KAUST Repository

    Alouini, Mohamed-Slim

    2015-01-07

    Rapid increase in the use of wireless services over the last two decades has lead the problem of the radio-frequency (RF) spectrum exhaustion. More specifically, due to this RF spectrum scarcity, additional RF bandwidth allocation, as utilized in the recent past, is not anymore a viable solution to fulfill the demand for more wireless applications and higher data rates. Among the many proposed solutions, optical wireless communication or free-space optical (FSO) systems have gained an increasing interest due to their advantages including higher bandwidth and higher capacity compared to the traditional RF communication systems. This promising technology offers full-duplex Gigabit throughput in certain applications and environment while benefiting from a huge license-free spectrum, immunity to interference, and high security. These features of FSO communication systems potentially enable solving the issues that the RF communication systems face due to the expensive and scarce RF spectrum. The first part of the talk will give an overview of FSO communication systems by offering examples of advantages and application areas of this emerging technology. In the second part of talk, we will focus on some recent results and on-going research directions in the accurate characterization of the performance of FSO systems in the presence of inevitable impairments due to atmospheric turbulence and misalignment between transmitter and receiver.

  4. Málaga statistical distribution: the new universal analytical propagation model for atmospheric optical communications

    DEFF Research Database (Denmark)

    Jurado-Navas, Antonio

    2015-01-01

    in homogeneous, isotropic turbulence. Málaga distribution was demonstrated to have the advantage of unifying most of the proposed statistical models derived until now in the scientific literature in a closed-form and mathematically-tractable expression. Furthermore, it unifies most of the proposed statistical...... models for the irradiance fluctuations derived in the bibliography providing, in addition, an excellent agreement with published plane wave and spherical wave simulation data over a wide range of turbulence conditions (weak to strong). In this communication, reviews of its different features...... scintillation in atmospheric optical communication links under any turbulence conditions...

  5. Optimum LED wavelength for underwater optical wireless communication at turbid water

    Science.gov (United States)

    Rosenkrantz, Etai; Arnon, Shlomi

    2014-10-01

    Underwater optical wireless communication is an emerging technology, which can provide high data rate. High data rate communication is required for applications such as underwater imaging, networks of sensors and swarms of underwater vehicles. These applications pursue an affordable light source, which can be obtained by light emitting diodes (LED). LEDs offer solutions characterized by low cost, high efficiency, reliability and compactness based on off-the-shelf components such as blue and green light emitting diodes. In this paper we present our recent theoretical and experimental results in this field.

  6. Effect of group velocity mismatch on acousto-optic interaction of ultrashort laser pulses

    International Nuclear Information System (INIS)

    Yushkov, K B; Molchanov, V Ya

    2011-01-01

    Equations describing acousto-optic diffraction of ultrashort laser pulses in an anisotropic medium are derived, taking into account the group velocity mismatch of optical eigenmodes. It is shown that the solution of the modified coupled-mode equations taking into account the group delay is characterised by an increase in the pulse duration, a decrease in diffraction efficiency, a change in the shape of the wave packet envelope, as well as by an increase in the width of the transmission function.

  7. An observational study of cross-cultural communication in short-term, diverse professional learning groups

    International Nuclear Information System (INIS)

    Robinson, Leslie; Hogg, Peter; Higgins, Robert

    2014-01-01

    This paper reports the evaluation of a European funded 3-week summer school which took place in 2013 involving 60 staff and students from five universities. The evaluation looked at one group in detail using a qualitative approach to consider whether students and teachers can work together in multicultural groups in order to achieve their goal. Method: One group was observed during 2 two-hour sessions of group activity; at the beginning and end of the summer school task. Video data was analysed using the Rapport Management framework, a model of cross-cultural communication, to determine what motivated this group's interactions. Results: As the group's deadline became imminent ‘face-threatening acts’ (FTAs) were more apparent. These were tolerated in this group because of the development of a strong social bond. There was inequity in participation with members of the group falling into either high- or low-involvement categories. This was also well-tolerated but meant some students may not have gained as much from the experience. The group lacked guidance on managing group dynamics. Conclusion: Cultural differences in communication were not the main threat to multi-cultural working groups. Potential problems can arise from failing to provide the group with a framework for project and team management. An emphasis on ground rules and the allocation of formal roles is important as is the encouragement of socialisation which supports the group during challenging times

  8. Effectiveness of communication strategies for deaf or hard of hearing workers in group settings.

    Science.gov (United States)

    Haynes, Scott

    2014-01-01

    In group settings, background noise and an obstructed view of the speaker are just a few of the issues that can make workplace communication difficult for an individual who is deaf or hard of hearing. Accommodation strategies such as amplification of the speaker's voice or the use of text-based alternatives exist to address these issues. However, recent studies have shown that there are still unmet needs related to workplace communication in group settings for individuals who are deaf or hard of hearing. Identify the most common strategies used by individuals who are deaf or hard of hearing to improve communication in group settings and gauge the perceived effectiveness of those strategies. An online survey was conducted with individuals who self-identified as deaf or hard of hearing. The survey presented specific communication strategies based on three functional approaches (aural/oral, text, visual). The strategies applied to both receptive and expressive communication in five different meeting types ranging in size and purpose. 161 adults (age 22-90 yrs.) with limited hearing ability completed the survey. Text-based strategies were typically the least frequently used strategies in group settings, yet they ranked high in perceived effectiveness for receptive and expressive communication. Those who used an interpreter demonstrated a strong preference for having a qualified interpreter present in the meeting rather than an interpreter acting remotely. For expressive communication, participants in general preferred to use their own voice or signing abilities and ranked those strategies as highly effective. A more accessible workplace for individuals who are deaf or hard of hearing would incorporate more ubiquitous text-based strategy options. Also, qualified interpreters, when used, should be present in the meeting for maximum effectiveness.

  9. System and method that suppresses intensity fluctuations for free space high-speed optical communication

    Science.gov (United States)

    Berman, Gennady P [Los Alamos, NM; Bishop, Alan R [Los Alamos, NM; Nguyen, Dinh C [Los Alamos, NM; Chernobrod, Boris M [Santa Fe, NM; Gorshkov, Vacheslav N [Kiev, UA

    2009-10-13

    A high-speed (Gbps), free space optical communication system is based on spectral encoding of radiation from a wide band light source, such as a laser. By using partially coherent laser beams in combination with a relatively slow photosensor, scintillations can be suppressed by orders of magnitude for distances of more than 10 km. To suppress the intensity fluctuations due to atmospheric turbulence, a source with partial transverse coherence in combination with slow response time photodetector is used. Information is encoded in the spectral domain of a wideband optical source by modulation of spectral amplitudes. A non-coherent light source with wide spectrum (an LED, for example) may be used for high-speed communication over short (less than about a mile) distances.

  10. 20-meter underwater wireless optical communication link with 1.5 Gbps data rate.

    Science.gov (United States)

    Shen, Chao; Guo, Yujian; Oubei, Hassan M; Ng, Tien Khee; Liu, Guangyu; Park, Ki-Hong; Ho, Kang-Ting; Alouini, Mohamed-Slim; Ooi, Boon S

    2016-10-31

    The video streaming, data transmission, and remote control in underwater call for high speed (Gbps) communication link with a long channel length (~10 meters). We present a compact and low power consumption underwater wireless optical communication (UWOC) system utilizing a 450-nm laser diode (LD) and a Si avalanche photodetector. With the LD operating at a driving current of 80 mA with an optical power of 51.3 mW, we demonstrated a high-speed UWOC link offering a data rate up to 2 Gbps over a 12-meter-long, and 1.5 Gbps over a record 20-meter-long underwater channel. The measured bit-error rate (BER) are 2.8 × 10-5, and 3.0 × 10-3, respectively, which pass well the forward error correction (FEC) criterion.

  11. Optimised dispersion management and modulation formats for high speed optical communication systems

    DEFF Research Database (Denmark)

    Tokle, Torger

    2004-01-01

    both narrow spectral width and good transmission properties. The cost of an optical communication system can be lowered by using longer span lengths to reduce the number of amplifier stations. We experimentally study optimum dispersion compensation schemes for systems with 160 km fibre spans made...... modulated signals. In summary, we show that dispersion management using recently developed fibres in combination with advanced modulation formats significantly improves the transmission performance compared to traditional systems. Multi-level phase modulation is demonstrated at bit rates up to 80 Gbit......This thesis studies dispersion management and modulation formats for optical communication systems using per channel bit rates at and above 10 Gbit/s. Novel modulation formats—including recently proposed multilevel phase modulation—are investigated and demonstrated at bit rates up to 80 Gbit/s. New...

  12. FPGA implementation of high-performance QC-LDPC decoder for optical communications

    Science.gov (United States)

    Zou, Ding; Djordjevic, Ivan B.

    2015-01-01

    Forward error correction is as one of the key technologies enabling the next-generation high-speed fiber optical communications. Quasi-cyclic (QC) low-density parity-check (LDPC) codes have been considered as one of the promising candidates due to their large coding gain performance and low implementation complexity. In this paper, we present our designed QC-LDPC code with girth 10 and 25% overhead based on pairwise balanced design. By FPGAbased emulation, we demonstrate that the 5-bit soft-decision LDPC decoder can achieve 11.8dB net coding gain with no error floor at BER of 10-15 avoiding using any outer code or post-processing method. We believe that the proposed single QC-LDPC code is a promising solution for 400Gb/s optical communication systems and beyond.

  13. Optimal operating conditions for external cavity semiconductor laser optical chaos communication system

    International Nuclear Information System (INIS)

    Priyadarshi, S; Pierce, I; Hong, Y; Shore, K A

    2012-01-01

    In optical chaos communications a message is masked in the noise-like broadband output of a chaotic transmitter laser, and message recovery is enabled through the synchronization of the transmitter and the (chaotic) receiver laser. Key issues are to identify the laser operating conditions which provide the highest quality synchronization conditions and those which provide optimized message extraction. In general such operating conditions are not coincident. In this paper numerical simulations are performed with the aim of identifying a regime of operation where the highest quality synchronization and optimizing message extraction efficiency are achieved simultaneously. Use of such an operating regime will facilitate practical deployment of optical chaos communications systems without the need for re-adjustment of laser operating conditions in the field. (paper)

  14. Automated alignment system for optical wireless communication systems using image recognition.

    Science.gov (United States)

    Brandl, Paul; Weiss, Alexander; Zimmermann, Horst

    2014-07-01

    In this Letter, we describe the realization of a tracked line-of-sight optical wireless communication system for indoor data distribution. We built a laser-based transmitter with adaptive focus and ray steering by a microelectromechanical systems mirror. To execute the alignment procedure, we used a CMOS image sensor at the transmitter side and developed an algorithm for image recognition to localize the receiver's position. The receiver is based on a self-developed optoelectronic integrated chip with low requirements on the receiver optics to make the system economically attractive. With this system, we were able to set up the communication link automatically without any back channel and to perform error-free (bit error rate <10⁻⁹) data transmission over a distance of 3.5 m with a data rate of 3 Gbit/s.

  15. Problem Based Learning as a Shared Musical Journey – Group Dynamics, Communication and Creativity

    Directory of Open Access Journals (Sweden)

    Charlotte Lindvang

    2015-06-01

    Full Text Available The focus of this paper is how we can facilitate problem based learning (PBL more creatively. We take a closer look upon the connection between creative processes and social communication in the PBL group including how difficulties in the social interplay may hinder creativity. The paper draws on group dynamic theory, and points out the importance of building a reflexive milieu in the group. Musical concepts are used to illustrate the communicative and creative aspects of PBL and the paper uses the analogy between improvising together and do a project work together. We also discuss the role of the supervisor in a PBL group process. Further we argue that creativity is rooted deep in our consciousness and connected to our ability to work with a flexible mind. In order to enhance the cohesion as well as the creativity of the group a model of music listening as a concrete intervention tool in PBL processes is proposed.

  16. The calculation of average error probability in a digital fibre optical communication system

    Science.gov (United States)

    Rugemalira, R. A. M.

    1980-03-01

    This paper deals with the problem of determining the average error probability in a digital fibre optical communication system, in the presence of message dependent inhomogeneous non-stationary shot noise, additive Gaussian noise and intersymbol interference. A zero-forcing equalization receiver filter is considered. Three techniques for error rate evaluation are compared. The Chernoff bound and the Gram-Charlier series expansion methods are compared to the characteristic function technique. The latter predicts a higher receiver sensitivity

  17. Active photonic sensor communication cable for field application of optical data and power transmission

    Science.gov (United States)

    Suthau, Eike; Rieske, Ralf; Zerna, Thomas

    2014-10-01

    Omitting electrically conducting wires for sensor communication and power supply promises protection for sensor systems and monitored structures against lightning or high voltages, prevention of explosion hazards, and reduction of susceptibility to tampering. The ability to photonically power remote systems opens up the full range of electrical sensors. Power-over-fiber is an attractive option in electromagnetically sensitive environments, particularly for longterm, maintenance-free applications. It can deliver uninterrupted power sufficient for elaborate sensors, data processing or even actuators alongside continuous high speed data communication for remote sensor application. This paper proposes an active photonic sensor communication system, which combines the advantages of optical data links in terms of immunity to electromagnetic interference (EMI), high bandwidth, hardiness against tampering or eavesdropping, and low cable weight with the robustness one has come to expect from industrial or military electrical connectors. An application specific integrated circuit (ASIC) is presented that implements a closed-loop regulation of the sensor power supply to guarantee continuous, reliable data communications while maintaining a highly efficient, adaptive sensor supply scheme. It is demonstrated that the resulting novel photonic sensor communication cable can handle sensors and actuators differing orders of magnitude with respect to power consumption. The miniaturization of the electro-optical converters and driving electronics is as important to the presented development as the energy efficiency of the detached, optically powered sensor node. For this reason, a novel photonic packaging technology based on wafer-level assembly of the laser power converters by means of passive alignment will be disclosed in this paper.

  18. High-dimensional free-space optical communications based on orbital angular momentum coding

    Science.gov (United States)

    Zou, Li; Gu, Xiaofan; Wang, Le

    2018-03-01

    In this paper, we propose a high-dimensional free-space optical communication scheme using orbital angular momentum (OAM) coding. In the scheme, the transmitter encodes N-bits information by using a spatial light modulator to convert a Gaussian beam to a superposition mode of N OAM modes and a Gaussian mode; The receiver decodes the information through an OAM mode analyser which consists of a MZ interferometer with a rotating Dove prism, a photoelectric detector and a computer carrying out the fast Fourier transform. The scheme could realize a high-dimensional free-space optical communication, and decodes the information much fast and accurately. We have verified the feasibility of the scheme by exploiting 8 (4) OAM modes and a Gaussian mode to implement a 256-ary (16-ary) coding free-space optical communication to transmit a 256-gray-scale (16-gray-scale) picture. The results show that a zero bit error rate performance has been achieved.

  19. Digital nonlinearity compensation in high-capacity optical communication systems considering signal spectral broadening effect.

    Science.gov (United States)

    Xu, Tianhua; Karanov, Boris; Shevchenko, Nikita A; Lavery, Domaniç; Liga, Gabriele; Killey, Robert I; Bayvel, Polina

    2017-10-11

    Nyquist-spaced transmission and digital signal processing have proved effective in maximising the spectral efficiency and reach of optical communication systems. In these systems, Kerr nonlinearity determines the performance limits, and leads to spectral broadening of the signals propagating in the fibre. Although digital nonlinearity compensation was validated to be promising for mitigating Kerr nonlinearities, the impact of spectral broadening on nonlinearity compensation has never been quantified. In this paper, the performance of multi-channel digital back-propagation (MC-DBP) for compensating fibre nonlinearities in Nyquist-spaced optical communication systems is investigated, when the effect of signal spectral broadening is considered. It is found that accounting for the spectral broadening effect is crucial for achieving the best performance of DBP in both single-channel and multi-channel communication systems, independent of modulation formats used. For multi-channel systems, the degradation of DBP performance due to neglecting the spectral broadening effect in the compensation is more significant for outer channels. Our work also quantified the minimum bandwidths of optical receivers and signal processing devices to ensure the optimal compensation of deterministic nonlinear distortions.

  20. Energy reduction using multi-channels optical wireless communication based OFDM

    Science.gov (United States)

    Darwesh, Laialy; Arnon, Shlomi

    2017-10-01

    In recent years, an increasing number of data center networks (DCNs) have been built to provide various cloud applications. Major challenges in the design of next generation DC networks include reduction of the energy consumption, high flexibility and scalability, high data rates, minimum latency and high cyber security. Use of optical wireless communication (OWC) to augment the DC network could help to confront some of these challenges. In this paper we present an OWC multi channels communication method that could lead to significant energy reduction of the communication equipment. The method is to convert a high speed serial data stream to many slower and parallel streams and vies versa at the receiver. We implement this concept of multi channels using optical orthogonal frequency division multiplexing (O-OFDM) method. In our scheme, we use asymmetrically clipped optical OFDM (ACO-OFDM). Our results show that the realization of multi channels OFDM (ACO-OFDM) methods reduces the total energy consumption exponentially, as the number of channels transmitted through them rises.

  1. Performance Evaluation of Underwater Wireless Optical Communications Links in the Presence of Different Air Bubble Populations

    KAUST Repository

    Oubei, Hassan M.; Elafandy, Rami T.; Park, Kihong; Ng, Tien Khee; Alouini, Mohamed-Slim; Ooi, Boon S.

    2017-01-01

    We experimentally evaluate the performance of underwater wireless optical communication (UWOC) links in the presence of different air bubbles. Air bubbles of different sizes and densities are generated by using an air pipe in conjunction with a submersible water pump of variable flow rate that help break up large bubbles into smaller bubbles. Received signal intensity measurements show that bubbles significantly degrade the performance of UWOC links. Large bubbles completely obstruct the optical beam and cause a deep fade. However, as the bubble size decreases, the level of deep fade also decreases because the optical beam is less susceptible to complete obstruction and more light reaches the detector. We also show that beam expansion could help mitigate the performance degradation due to the deep fade caused by air bubbles scatters in the channel.

  2. Secured Optical Communications Using Quantum Entangled Two-Photon Transparency Modulation

    Science.gov (United States)

    Kojima, Jun (Inventor); Nguyen, Quang-Viet (Inventor); Lekki, John (Inventor)

    2015-01-01

    A system and method is disclosed wherein optical signals are coded in a transmitter by tuning or modulating the interbeam delay time (which modulates the fourth-order coherence) between pairs of entangled photons. The photon pairs are either absorbed or not absorbed (transparent) by an atomic or molecular fluorescer in a receiver, depending on the inter-beam delay that is introduced in the entangled photon pairs. Upon the absorption, corresponding fluorescent optical emissions follow at a certain wavelength, which are then detected by a photon detector. The advantage of the disclosed system is that it eliminates a need of a coincidence counter to realize the entanglement-based secure optical communications because the absorber acts as a coincidence counter for entangled photon pairs.

  3. Main-Reflector Manufacturing Technology for the Deep Space Optical Communications Ground Station

    Science.gov (United States)

    Britcliffe, M. J.; Hoppe, D. J.

    2001-01-01

    The Deep Space Network (DSN) has plans to develop a 10-m-diameter optical communications receiving station. The system uses the direct detection technique, which has much different requirements from a typical astronomical telescope. The receiver must operate in daylight and nighttime conditions. This imposes special requirements on the optical system to reject stray light from the Sun and other sources. One of the biggest challenges is designing a main-reflector surface that meets these requirements and can be produced at a reasonable cost. The requirements for the performance of the reflector are presented. To date, an aspherical primary reflector has been assumed. A reflector with a spherical reflector has a major cost advantage over an aspherical design, with no sacrifice in performance. A survey of current manufacturing techniques for optical mirrors of this type was performed. Techniques including solid glass, lightweight glass, diamond-turned aluminum, and composite mirrors were investigated.

  4. Performance Evaluation of Underwater Wireless Optical Communications Links in the Presence of Different Air Bubble Populations

    KAUST Repository

    Oubei, Hassan M.

    2017-03-16

    We experimentally evaluate the performance of underwater wireless optical communication (UWOC) links in the presence of different air bubbles. Air bubbles of different sizes and densities are generated by using an air pipe in conjunction with a submersible water pump of variable flow rate that help break up large bubbles into smaller bubbles. Received signal intensity measurements show that bubbles significantly degrade the performance of UWOC links. Large bubbles completely obstruct the optical beam and cause a deep fade. However, as the bubble size decreases, the level of deep fade also decreases because the optical beam is less susceptible to complete obstruction and more light reaches the detector. We also show that beam expansion could help mitigate the performance degradation due to the deep fade caused by air bubbles scatters in the channel.

  5. A flexible receiver with fiber optical parametric amplifier in OCDMA-FSO communication system

    Science.gov (United States)

    Xia, Min; Yuan, Jin-hui; Sang, Xin-zhu; Yin, Xiao-li; Rao, Lan; Yu, Chong-xiu

    2014-11-01

    A new receiver is proposed, which uses the fiber optical parametric amplifier (FOPA) in optical code division multiple access (OCDMA) over free space optic (FSO) communication system. The noise tolerance as the performance index in this receiver is derived. The receiver can not only improve the noise tolerance but also change the pump data conveniently for adapting to the length variation of the coding sequence under a complex and fast-changing weather condition. The influence of different factors on the noise tolerance is analyzed, and a significant improvement of about 18.77 dB for the noise tolerance can be achieved when the pump power and the length of coding sequence are 5 W and 256, respectively.

  6. Future optical communication networks beyond 160 Gbit/s based on OTDM

    Science.gov (United States)

    Prati, Giancarlo; Bogoni, Antonella; Poti, Luca

    2005-01-01

    The virtually unlimited bandwidth of optical fibers has caused a great increase in data transmission speed over the past decade and, hence, stimulated high-demand multimedia services such as distance learning, video-conferencing and peer to peer applications. For this reason data traffic is exceeding telephony traffic, and this trend is driving the convergence of telecommunications and computer communications. In this scenario Internet Protocol (IP) is becoming the dominant protocol for any traffic, shifting the attention of the network designers from a circuit switching approach to a packet switching approach. A role of paramount importance in packet switching networks is played by the router that must implement the functionalities to set up and maintain the inter-nodal communications. The main functionalities a router must implement are routing, forwarding, switching, synchronization, contention resolution, and buffering. Nowadays, opto-electronic conversion is still required at each network node to process the incoming signal before routing that to the right output port. However, when the single channel bit rate increases beyond electronic speed limit, Optical Time Division Multiplexing (OTDM) becomes a forced choice, and all-optical processing must be performed to extract the information from the incoming packet. In this paper enabling techniques for ultra-fast all-optical network will be addressed. First a 160 Gbit/s complete transmission system will be considered. As enabling technique, an overview for all-optical logics will be discussed and experimental results will be presented using a particular reconfigurable NOLM based on Self-Phase-Modulation (SPM) or Cross-Phase-Modulation (XPM). Finally, a rough experiment on label extraction, all-optical switching and packet forwarding is shown.

  7. The Correlation between Interpersonal Communication Skills of Inspection Groups and Their Conflict Management Strategies

    Science.gov (United States)

    Sabanci, Ali; Sahin, Ahmet; Özdemir, Izzet

    2018-01-01

    The purpose of this study was to explore the correlation between interpersonal communication skills and conflict management strategies in the case of inspection groups constituted by a number of inspectors based on the geographical and demographic dispersion of the school population in Turkey. This research was conducted as a survey. The…

  8. Group Communication and Critical Thinking Competence Development Using a Reality-Based Project

    Science.gov (United States)

    Paulson, Edward

    2011-01-01

    The presented merger and acquisition classroom exercise is based on a real yet incomplete transaction transpiring during the period of the class. The approach enables adult students to apply their previously acquired business experience to a strategic analysis project facilitating the development of group communication, critical thinking, and…

  9. Gladwell and Group Communication: Using "The Tipping Point" as a Supplemental Text

    Science.gov (United States)

    Browning, Blair W.

    2011-01-01

    This article describes an activity using Malcolm Gladwell's "The Tipping Point" as a supplemental text in an undergraduate group communication course. This book will help stimulate conversation and promote easy avenues for classroom discussion. In addition to weekly quizzes over each chapter to help facilitate rich classroom discussions, the…

  10. The Referential Function of Internal Communication Groups in Complex Organizations: An Empirical Analysis.

    Science.gov (United States)

    Taylor, James A.; Farace, Richard V.

    This paper argues that people who interact regularly and repetitively among themselves create a conjoint information space wherein common values, attitudes, and beliefs arise through the process of information transmission among the members in the space. Three major hypotheses concerning informal communication groups in organizations were tested…

  11. Communicating the Nature of Science through "The Big Bang Theory": Evidence from a Focus Group Study

    Science.gov (United States)

    Li, Rashel; Orthia, Lindy A.

    2016-01-01

    In this paper, we discuss a little-studied means of communicating about or teaching the nature of science (NOS)--through fiction television. We report some results of focus group research which suggest that the American sitcom "The Big Bang Theory" (2007-present), whose main characters are mostly working scientists, has influenced…

  12. Problembased learning as a shared musical journey - group dynamics, communication and creativity

    DEFF Research Database (Denmark)

    Lindvang, Charlotte; Beck, Bolette Daniels

    2015-01-01

    The focus of this paper is how we can facilitate problem based learning (PBL) more creatively. We take a closer look upon the connection between creative processes and social communication in the PBL group including how difficulties in the social interplay may hinder creativity. The paper draws o...

  13. Free-Space Optical Communications Link at 1550-nm using Multiple-Quantum-Well Modulating Retroreflectors in a Marine Environment

    National Research Council Canada - National Science Library

    Rabinovich, W. S; Mahon, R; Burris, H. R; Gilbreath, G. C; Goetz, P. G; Moore, C. I; Stell, M. F; Vilcheck, M. J; Witkowsky, J. L; Swingen, L

    2005-01-01

    A 1550-nm eye-safe, free-space optical communications link is demonstrated at rates up to 5 Mbits/s over a distance of 2 km in the Chesapeake Bay, using quantum-well-based modulating retroreflectors...

  14. Communication patterns within a group of shelter dogs and implications for their welfare.

    Science.gov (United States)

    Petak, Irena

    2013-01-01

    Keeping shelter dogs in groups provides them with a more socially and physically enriched environment, but eventually it may cause them stress. Understanding dogs' communication could help shelter staff recognize and prevent undesirable communicative patterns and encourage desirable ones. Therefore, the objective of this study was to determine communication patterns in a group of dogs in a shelter. The observed dogs were engaged in different classes of dyadic and group interactions. Certain dogs were frequently initiators of dyadic interactions, and different dogs were the recipients. The predominant form of dyadic interactions was a neutral one, and aggressive behavior was rarely observed. The tendency of certain dogs to interact continuously may represent a nuisance for less social individuals. All of the dogs participated in 3 defined classes of group interactions. At the group level, the dogs frequently interact vocally or olfactorily. A major welfare problem may be very vocal dogs because their vocalizations are noisy and broadcast far-reaching signals. The frequency of some group interactions was reduced by the amount of time the dogs had in the shelter.

  15. Interprofessional communication skills training for serious illness: evaluation of a small-group, simulated patient intervention.

    Science.gov (United States)

    Bays, Alison M; Engelberg, Ruth A; Back, Anthony L; Ford, Dee W; Downey, Lois; Shannon, Sarah E; Doorenbos, Ardith Z; Edlund, Barbara; Christianson, Phyllis; Arnold, Richard W; O'Connor, Kim; Kross, Erin K; Reinke, Lynn F; Cecere Feemster, Laura; Fryer-Edwards, Kelly; Alexander, Stewart C; Tulsky, James A; Curtis, J Randall

    2014-02-01

    Communication with patients and families is an essential component of high-quality care in serious illness. Small-group skills training can result in new communication behaviors, but past studies have used facilitators with extensive experience, raising concerns this is not scalable. The objective was to investigate the effect of an experiential communication skills building workshop (Codetalk), led by newly trained facilitators, on internal medicine trainees' and nurse practitioner students' ability to communicate bad news and express empathy. Trainees participated in Codetalk; skill improvement was evaluated through pre- and post- standardized patient (SP) encounters. The subjects were internal medicine residents and nurse practitioner students at two universities. The study was carried out in anywhere from five to eight half-day sessions over a month. The first and last sessions included audiotaped trainee SP encounters coded for effective communication behaviors. The primary outcome was change in communication scores from pre-intervention to post-intervention. We also measured trainee characteristics to identify predictors of performance and change in performance over time. We enrolled 145 trainees who completed pre- and post-intervention SP interviews-with participation rates of 52% for physicians and 14% for nurse practitioners. Trainees' scores improved in 8 of 11 coded behaviors (p<0.05). The only significant predictors of performance were having participated in the intervention (p<0.001) and study site (p<0.003). The only predictor of improvement in performance over time was participating in the intervention (p<0.001). A communication skills intervention using newly trained facilitators was associated with improvement in trainees' skills in giving bad news and expressing empathy. Improvement in communication skills did not vary by trainee characteristics.

  16. Universal squash model for optical communications using linear optics and threshold detectors

    International Nuclear Information System (INIS)

    Fung, Chi-Hang Fred; Chau, H. F.; Lo, Hoi-Kwong

    2011-01-01

    Transmission of photons through open-air or optical fibers is an important primitive in quantum-information processing. Theoretical descriptions of this process often consider single photons as information carriers and thus fail to accurately describe experimental implementations where any number of photons may enter a detector. It has been a great challenge to bridge this big gap between theory and experiments. One powerful method for achieving this goal is by conceptually squashing the received multiphoton states to single-photon states. However, until now, only a few protocols admit a squash model; furthermore, a recently proven no-go theorem appears to rule out the existence of a universal squash model. Here we show that a necessary condition presumed by all existing squash models is in fact too stringent. By relaxing this condition, we find that, rather surprisingly, a universal squash model actually exists for many protocols, including quantum key distribution, quantum state tomography, Bell's inequality testing, and entanglement verification.

  17. CMOS Receiver Front-ends for Gigabit Short-Range Optical Communications

    CERN Document Server

    Aznar, Francisco; Calvo Lopez, Belén

    2013-01-01

    This book describes optical receiver solutions integrated in standard CMOS technology, attaining high-speed short-range transmission within cost-effective constraints.  These techniques support short reach applications, such as local area networks, fiber-to-the-home and multimedia systems in cars and homes. The authors show how to implement the optical front-end in the same technology as the subsequent digital circuitry, leading to integration of the entire receiver system in the same chip.  The presentation focuses on CMOS receiver design targeting gigabit transmission along a low-cost, standardized plastic optical fiber up to 50m in length.  This book includes a detailed study of CMOS optical receiver design – from building blocks to the system level. Reviews optical communications, including long-haul transmission systems and emerging applications focused on short-range; Explains necessary fundamentals, such as characteristics of a data signal, system requirements affecting receiver design and key par...

  18. The peculiar acceleration of the Local Group as deduced from the optical and IRAS flux dipoles

    International Nuclear Information System (INIS)

    Lahav, O.; Lynden-Bell, D.

    1988-01-01

    The relation between the peculiar acceleration of the Local Group and the surface brightness dipole moments of all-sky optical and IRAS samples is studied. Our revised optical dipole lies within 7 0 of the direction of the Local Group's motion through the Microwave Background Radiation (MBR). The directions of the optical, IRAS and MBR dipoles are all consistent with each other. To analyse the optical dipole we have calculated diameter functions for the UGC and ESO galaxy catalogues from redshift surveys. Most of the optical dipole arises from the Centaurus-Virgo direction and from the 'Local Void' on the opposite side of the sky. The sources of the IRAS dipole are more evenly distributed around the sky. A simple 'shell model', fitted to the variation of the dipoles as a function of flux, suggests that the dipoles arise from galaxies whose recession velocities are smaller than 4000 kms -1 . We find a high Ω 0 value for the IRAS sample and a low one for the optical sample. These results may be reconciled if the optical galaxy distribution is more biased relative to the matter distribution than the IRAS galaxy distribution. (author)

  19. Bio-Optical sensors on Argo Floats. Reports of the international ocean-colour coordinating group

    CSIR Research Space (South Africa)

    Bernard, S

    2011-01-01

    Full Text Available The International Ocean-Colour Coordinating Group (IOCCG) is an international group of experts in the field of satellite ocean colour, acting as a liaison and communication channel between users, managers and agencies in the ocean-colour arena...

  20. Influence of wind speed on free space optical communication performance for Gaussian beam propagation through non Kolmogorov strong turbulence

    International Nuclear Information System (INIS)

    Deng Peng; Yuan Xiuhua; Zeng Yanan; Zhao Ming; Luo Hanjun

    2011-01-01

    In free-space optical communication links, atmospheric turbulence causes fluctuations in both the intensity and the phase of the received signal, affecting link performance. Most theoretical treatments have been described by Kolmogorov's power spectral density model through weak turbulence with constant wind speed. However, several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric turbulence properly, especially through the strong turbulence with variable wind speed, which is known to contribute significantly to the turbulence in the atmosphere. We present an optical turbulence model that incorporates into variable wind speed instead of constant value, a non-Kolmogorov power spectrum that uses a generalized exponent instead of constant standard exponent value 11/3, and a generalized amplitude factor instead of constant value 0.033. The free space optical communication performance for a Gaussian beam wave of scintillation index, mean signal-to-noise ratio , and mean bit error rate , have been derived by extended Rytov theory in non-Kolmogorov strong turbulence. And then the influence of wind speed variations on free space optical communication performance has been analyzed under different atmospheric turbulence intensities. The results suggest that the effects of wind speed variation through non-Kolmogorov turbulence on communication performance are more severe in many situations and need to be taken into account in free space optical communication. It is anticipated that this work is helpful to the investigations of free space optical communication performance considering wind speed under severe weather condition in the strong atmospheric turbulence.

  1. Adaptive optics correction into single mode fiber for a low Earth orbiting space to ground optical communication link using the OPALS downlink.

    Science.gov (United States)

    Wright, Malcolm W; Morris, Jeffery F; Kovalik, Joseph M; Andrews, Kenneth S; Abrahamson, Matthew J; Biswas, Abhijit

    2015-12-28

    An adaptive optics (AO) testbed was integrated to the Optical PAyload for Lasercomm Science (OPALS) ground station telescope at the Optical Communications Telescope Laboratory (OCTL) as part of the free space laser communications experiment with the flight system on board the International Space Station (ISS). Atmospheric turbulence induced aberrations on the optical downlink were adaptively corrected during an overflight of the ISS so that the transmitted laser signal could be efficiently coupled into a single mode fiber continuously. A stable output Strehl ratio of around 0.6 was demonstrated along with the recovery of a 50 Mbps encoded high definition (HD) video transmission from the ISS at the output of the single mode fiber. This proof of concept demonstration validates multi-Gbps optical downlinks from fast slewing low-Earth orbiting (LEO) spacecraft to ground assets in a manner that potentially allows seamless space to ground connectivity for future high data-rates network.

  2. Psychometrics of shared decision making and communication as patient centered measures for two language groups.

    Science.gov (United States)

    Alvarez, Kiara; Wang, Ye; Alegria, Margarita; Ault-Brutus, Andrea; Ramanayake, Natasha; Yeh, Yi-Hui; Jeffries, Julia R; Shrout, Patrick E

    2016-09-01

    Shared decision making (SDM) and effective patient-provider communication are key and interrelated elements of patient-centered care that impact health and behavioral health outcomes. Measurement of SDM and communication from the patient's perspective is necessary in order to ensure that health care systems and individual providers are responsive to patient views. However, there is a void of research addressing the psychometric properties of these measures with diverse patients, including non-English speakers, and in the context of behavioral health encounters. This study evaluated the psychometric properties of 2 patient-centered outcome measures, the Shared Decision-Making Questionnaire-9 (SDM-Q) and the Kim Alliance Scale-Communication subscale (KAS-CM), in a sample of 239 English and Spanish-speaking behavioral health patients. One dominant factor was found for each scale and this structure was used to examine whether there was measurement invariance across the 2 language groups. One SDM-Q item was inconsistent with the configural invariance comparison and was removed. The remaining SDM-Q items exhibited strong invariance, meaning that item loadings and item means were similar across the 2 groups. The KAS-CM items had limited variability, with most respondents indicating high communication levels, and the invariance analysis was done on binary versions of the items. These had metric invariance (loadings the same over groups) but several items violated the strong invariance test. In both groups, the SDM-Q had high internal consistency, whereas the KAS-CM was only adequate. These findings help interpret results for individual patients, taking into account cultural and linguistic differences in how patients perceive SDM and patient-provider communication. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

  3. Near Earth Architectural Options for a Future Deep Space Optical Communications Network

    Science.gov (United States)

    Edwards, B. L.; Liebrecht, P. E.; Fitzgerald, R. J.

    2004-01-01

    In the near future the National Aeronautics and Space Administration anticipates a significant increase in demand for long-haul communications services from deep space to Earth. Distances will range from 0.1 to 40 AU, with data rate requirements in the 1's to 1000's of Mbits/second. The near term demand is driven by NASA's Space Science Enterprise which wishes to deploy more capable instruments onboard spacecraft and increase the number of deep space missions. The long term demand is driven by missions with extreme communications challenges such as very high data rates from the outer planets, supporting sub-surface exploration, or supporting NASA's Human Exploration and Development of Space Enterprise beyond Earth orbit. Laser communications is a revolutionary communications technology that will dramatically increase NASA's ability to transmit information across the solar system. Lasercom sends information using beams of light and optical elements, such as telescopes and optical amplifiers, rather than RF signals, amplifiers, and antennas. This paper provides an overview of different network options at Earth to meet NASA's deep space lasercom requirements. It is based mainly on work done for the Mars Laser Communications Demonstration Project, a joint project between NASA's Goddard Space Flight Center (GSFC), the Jet Propulsion Laboratory, California Institute of Technology (JPL), and the Massachusetts Institute of Technology Lincoln Laboratory (MIT/LL). It reports preliminary conclusions from the Mars Lasercom Study conducted at MIT/LL and on additional work done for the Tracking and Data Relay Satellite System Continuation Study at GSFC. A lasercom flight terminal will be flown on the Mars Telesat Orbiter (MTO) to be launched by NASA in 2009, and will be the first high rate deep space demonstration of this revolutionary technology.

  4. Dember effect photodetectors and the effects of turbulence on free-space optical communication systems

    Science.gov (United States)

    Dikmelik, Yamac

    High-speed free-space optical communication systems have recently utilized components that have been developed for fiber-optic communication systems. The received laser beam in such a system must be coupled into a single-mode fiber at the input of a commercially available receiver module or a wavelength division demultiplexer. However, one effect of propagation through atmospheric turbulence is that the spatial coherence of a laser beam is degraded and the percentage of the available power that can be coupled into the single-mode fiber is limited. This dissertation presents a numerical evaluation of fiber coupling efficiency for laser light distorted by atmospheric turbulence. The results for weak fluctuation conditions provide the level of coupling efficiency that can be expected for a given turbulence strength. In addition, the results show that the link distance must be limited to 400 m under moderate turbulence conditions if the link budget requires a coupling efficiency of 0.1. We also investigate the use of a coherent fiber array as a receiver structure to improve the fiber coupling efficiency of a free-space optical communication system. Our numerical results show that a coherent fiber array that consists of seven subapertures would increase fiber coupling efficiency by a significant amount for representative turbulence conditions and link distances. The use of photo-emf detectors as elements of a wavefront sensor for an adaptive optics system is also considered as an alternative method of reducing the effects of turbulence on a free-space optical communication system. Dember and photo-emf currents are investigated in silicon photoconductive detectors both theoretically and experimentally. Our results show that Dember photocurrents dominate the response of high-purity silicon samples with top surface electrodes to a moving interference pattern. The use of surface electrodes leads to shadowed regions beneath the electrodes and Dember photocurrents appear

  5. Narratives of empowerment and compliance: studies of communication in online patient support groups.

    Science.gov (United States)

    Wentzer, Helle S; Bygholm, Ann

    2013-12-01

    New technologies enable new forms of patient participation in health care. The article discusses whether communication in online patient support groups is a source of individual as well as collective empowerment or to be understood within the tradition of compliance. The discussion is based on a qualitative analysis of patient communication in two online groups on the Danish portal sundhed.dk, one for lung patients and one for women with fertility problems. The object of study is the total sum of postings during a specific period of time - a total of 4301 posts are included. The textmaterial was analyzed according to the textual paradigm of Paul Ricoeur, and the three steps of critical interpretation. Thus, the analysis moves from describing communicative characteristics of the site to a thorough semantic analysis of its narrative structure of construing meaning, interaction and collective identity, and finally as a source of collective action. The meta-narratives of the two groups confirm online patient support groups for individual empowerment, for collective group identity, but not for collective empowerment. The collective identities of patienthood on the two sites are created by the users (patients) through specific styles of communication and interaction, referred to as 'multi-logical narratives'. In spite of the potential of online communities of opening up health care to the critical voice of the public, the analysis points to a synthesis of the otherwise opposite positions of empowerment and compliance in patient care. On a collective level, the site is empowering the individual users to comply with 'doctor's recommendations' as a group. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  6. 2.3 Gbit/s underwater wireless optical communications using directly modulated 520 nm laser diode

    KAUST Repository

    Oubei, Hassan M.; Li, Changping; Park, Kihong; Ng, Tien Khee; Alouini, Mohamed-Slim; Ooi, Boon S.

    2015-01-01

    We experimentally demonstrate a record high-speed underwater wireless optical communication (UWOC) over 7 m distance using on-off keying non-return-to-zero (OOK-NRZ) modulation scheme. The communication link uses a commercial TO-9 packaged pigtailed

  7. A Novel Noise Free Transmission Technique for Designing 100Gb/s Future Generation Optical Communication System

    DEFF Research Database (Denmark)

    Das, Bhagwan; Abdullah, M.F.L.; Pandey, Bishwajeet

    2017-01-01

    Differential Phase Shift Keying (DPSK) techniques are widely used in designing the high-speed communication systems. However, these techniques still need improvement for long haul communication system design. In this paper, high-speed optical signal transmission and reception system is achieved f...

  8. Dispersion compensation of fiber optic communication system with direct detection using artificial neural networks (ANNs)

    Science.gov (United States)

    Maghrabi, Mahmoud M. T.; Kumar, Shiva; Bakr, Mohamed H.

    2018-02-01

    This work introduces a powerful digital nonlinear feed-forward equalizer (NFFE), exploiting multilayer artificial neural network (ANN). It mitigates impairments of optical communication systems arising due to the nonlinearity introduced by direct photo-detection. In a direct detection system, the detection process is nonlinear due to the fact that the photo-current is proportional to the absolute square of the electric field intensity. The proposed equalizer provides the most efficient computational cost with high equalization performance. Its performance is comparable to the benchmark compensation performance achieved by maximum-likelihood sequence estimator. The equalizer trains an ANN to act as a nonlinear filter whose impulse response removes the intersymbol interference (ISI) distortions of the optical channel. Owing to the proposed extensive training of the equalizer, it achieves the ultimate performance limit of any feed-forward equalizer (FFE). The performance and efficiency of the equalizer is investigated by applying it to various practical short-reach fiber optic communication system scenarios. These scenarios are extracted from practical metro/media access networks and data center applications. The obtained results show that the ANN-NFFE compensates for the received BER degradation and significantly increases the tolerance to the chromatic dispersion distortion.

  9. A high-speed 0.35μm CMOS optical communication link

    Science.gov (United States)

    Goosen, Marius E.; Venter, Petrus J.; du Plessis, Monuko; Bogalecki, Alfons W.; Alberts, Antonie C.; Rademeyer, Pieter

    2012-01-01

    The idea of integrating a light emitter and detector in the cost effective and mature technology which is CMOS remains an attractive one. Silicon light emitters, used in avalanche breakdown, are demonstrated to switch at frequencies above 1 GHz whilst still being electrically detected, a three-fold increase on previous reported results. Utilizing novel BEOLstack reflectors and increased array sizes have resulted in an increased power efficiency allowing multi-Mb/s data rates. In this paper we present an all-silicon optical communication link with data rates exceeding 10 Mb/s at a bit error rate of less than 10-12, representing a ten-fold increase over the previous fastest demonstrated silicon data link. Data rates exceeding 40 Mb/s are also presented and evaluated. The quality of the optical link is established using both eye diagram measurements as well as a digital communication system setup. The digital communication system setup comprises the generation of 232-1 random data, 8B/10B encoding and decoding, data recovery and the subsequent bit error counting.

  10. Dispersion compensation in an open-loop all-optical chaotic communication system

    International Nuclear Information System (INIS)

    Liu Hui-Jie; Feng Jiu-Chao; Ren Bin

    2012-01-01

    The optical chaotic communication system using open-loop fiber transmission is studied under strong injection conditions. The optical chaotic communication system with open-loop configuration is studied using fiber transmission under strong injection conditions. The performances of fiber links composed of two types of fiber segments in different dispersion compensation maps are compared by testing the quality of the recovered message with different bit rates and encrypted by chaotic modulation (CM) or chaotic shift keying (CSK). The result indicates that the performance of the pre-compensation map is always worst. Two types of symmetrical maps are identical whatever the encryption method and bit-rate of message are. For the transmitting and the recovering of message of lower bit rate (1 Gb/s), the post-compensation map is the best scheme. However, for the message of higher bit rate (2.5 Gb/s), the parameters in communication system need to be modified properly in order to adapt to the high-speed application. Meanwhile, two types of symmetrical maps are the best scheme. In addition, the CM method is superior to the CSK method for high-speed applications. It is in accordance with the result in a back-to-back configuration system. (general)

  11. Effects of longitudinal small-group learning on delivery and receipt of communication skills feedback.

    Science.gov (United States)

    Chou, Calvin L; Masters, Dylan E; Chang, Anna; Kruidering, Marieke; Hauer, Karen E

    2013-11-01

    Although feedback is a critical component of learning, recent data suggest that learners may discount feedback they receive. The emotional threat inherent in feedback can contribute to its ineffectiveness, particularly for sensitive topics like communication skills. Longitudinal relationships among peers may increase their sense of safety and soften the perceived threat of feedback to allow students to give, receive and potentially more effectively incorporate feedback. We studied the effects of prior shared learning experiences among medical students in the delivery and receipt of feedback on clinical (communication) skills. During a formative clinical skills examination, we divided Year 3 students at a US medical school into two subgroups comprising, respectively, small-group classmates from a 2-year longitudinal pre-clerkship clinical skills course (with prior peer-learning relationships), and peers with no prior shared small-group coursework. Students in both subgroups observed peers in a simulated clinical case and then provided feedback, which was videotaped, transcribed and coded. Feedback recipients also completed a survey on their perceptions of the feedback. Students valued the feedback they received and intended to enact it, regardless of whether they had prior peer-learning relationships. Coding of feedback revealed high specificity. Feedback providers who had prior peer-learning relationships with recipients provided more specific corrective feedback on communication skills than those with no such relationships (p = 0.014); there was no significant difference between subgroups in the provision of reinforcing feedback on communication skills. Year 3 medical student peers can deliver specific feedback on clinical skills; prior peer-learning relationships in pre-clerkship clinical skills courses enrich the provision of specific corrective feedback about communication skills. Feedback between peers with pre-existing peer-learning relationships represents

  12. Three-dimensional imaging of the optic nerve using magnetic resonance angiography. Application to anterior communicating artery aneurysm and craniopharingioma

    International Nuclear Information System (INIS)

    Okuyama, Tohru; Fukuyama, Atsushi; Fukuyama, Koichi; Ikeno, Kunihiro; Araki, Hiroyuki; Okada, Kinya; Sohma, Noriko

    2005-01-01

    The purpose of this investigation was to analyze three-dimensional images of the optic nerve obtained by magnetic resonance angiography (MRA) in cases of anterior communicating artery aneurysm and craniopharingioma. Four ruptured anterior communicating artery aneurysms, five non-ruptured anterior communicating artery aneurysms and two craniopharingiomas were examined. The images were taken using MR/i Hispeed Plus 1.5 T Infinity version, and analyzed by Advantage Work station AW4.1. The routine MR imaging parameters are shown in Table. The imaging time was about 10 minutes. Analysis was made by reformation of images parallel to the optic nerve obtained from the original MRA images. The optic nerve and brain tumor were traced with paintbrush from one sheet to another of the reformed images after subtraction of the blood vessels around the anterior communicating artery in these reformed images, and then three-dimensional images were constructed. Three-dimensional images of the blood vessels were reconstructed from MIP (maximum intensity projection) images using the threshold method. The optic nerve and anterior communicating arterial aneurysm or brain tumor were both observed in the overlapped 3D-SSD (shaded surface display) images. The analysis time was about 15 minutes. Three-dimensional images of the optic nerve and anterior communicating artery aneurysm or brain tumor were able to be made in all cases. As a preoperative investigation for anterior communicating artery aneurysm or suprasellar brain tumor, we considered that three-dimensional imaging of the optic nerve is useful in the operative approach because the optic nerve acts as a merkmal for the anterior communicating aneurysm or brain tumor. (author)

  13. Fundus autofluorescence and optical coherence tomography of congenital grouped albinotic spots.

    Science.gov (United States)

    Kim, David Y; Hwang, John C; Moore, Anthony T; Bird, Alan C; Tsang, Stephen H

    2010-09-01

    The purpose of this study was to describe the findings of fundus autofluores-cence (FAF) and optical coherence tomography in a series of patients with congenital grouped albinotic spots. Three eyes of three patients with congenital grouped albinotic spots were evaluated with FAF and optical coherence tomography imaging to evaluate the nature of the albinotic spots. In all three eyes with congenital grouped albinotic spots, FAF imaging showed autofluorescent spots corresponding to the albinotic spots seen on stereo biomicroscopy. One eye also had additional spots detected on FAF imaging that were not visible on stereo biomicroscopy or color fundus photographs. Fundus autofluorescence imaging of the spots showed decreased general autofluorescence and decreased peripheral autofluorescence surrounding central areas of retained or increased autofluorescence. Optical coherence tomography showed a disruption in signal from the hyperreflective layer corresponding to the inner and outer segment junction and increased signal backscattering from the choroid in the area of the spots. Fluorescein angiography showed early and stable hyperfluorescence of the spots without leakage. In this case series, FAF showed decreased autofluorescence of the spots consistent with focal retinal pigment epithelium atrophy or abnormal material blocking normal autofluorescence and areas of increased autofluorescence suggesting retinal pigment epithelium dysfunction. The findings of optical coherence tomography and fluorescein angiography suggest photoreceptor and retinal pigment epithelium layer abnormalities. Fundus autofluorescence and optical coherence tomography are useful noninvasive diagnostic adjuncts that can aid in the diagnosis of congenital grouped albinotic spots, help determine extent of disease, and contribute to our understanding of its pathophysiology.

  14. New role for communication fibre optic cables in water utility for leak detection on main water pipeline

    OpenAIRE

    Graovac Radojica M.; Marković Dragomir V.

    2015-01-01

    During construction of main water pipeline it is usual practice to lay fibre optic communication cable along water pipe. This cable is one of the up to date communication media which is used for the connection purposes of water control SCADA equipment as well as for establishing of telephone communication between water utility plants. By developing of new electronic equipment known as DTS (Distributed Temperature Sensing) and DAS (Distributed Acoustic Sensing) equipment it has been opened the...

  15. Young patients', parents', and survivors' communication preferences in paediatric oncology: Results of online focus groups

    Directory of Open Access Journals (Sweden)

    Kamps Willem A

    2007-11-01

    Full Text Available Abstract Background Guidelines in paediatric oncology encourage health care providers to share relevant information with young patients and parents to enable their active participation in decision making. It is not clear to what extent this mirrors patients' and parents' preferences. This study investigated communication preferences of childhood cancer patients, parents, and survivors of childhood cancer. Methods Communication preferences were examined by means of online focus groups. Seven patients (aged 8–17, 11 parents, and 18 survivors (aged 8–17 at diagnosis participated. Recruitment took place by consecutive inclusion in two Dutch university oncological wards. Questions concerned preferences regarding interpersonal relationships, information exchange and participation in decision making. Results Participants expressed detailed and multi-faceted views regarding their needs and preferences in communication in paediatric oncology. They agreed on the importance of several interpersonal and informational aspects of communication, such as honesty, support, and the need to be fully informed. Participants generally preferred a collaborative role in medical decision making. Differences in views were found regarding the desirability of the patient's presence during consultations. Patients differed in their satisfaction with their parents' role as managers of the communication. Conclusion Young patients' preferences mainly concur with current guidelines of providing them with medical information and enabling their participation in medical decision making. Still, some variation in preferences was found, which faces health care providers with the task of balancing between the sometimes conflicting preferences of young cancer patients and their parents.

  16. How young people communicate risks of snowmobiling in northern Norway: a focus group study.

    Science.gov (United States)

    Mehus, Grete; Germeten, Sidsel; Henriksen, Nils

    2011-04-01

    This study aims to understand how the risks of snowmobiling are communicated among northern Norwegian youths. Study design. A qualitative design with focus group interviews was chosen. Interviews centred on safety precautions and estimation of risks related to snowmobiling and driving patterns. Eighty-one students (31 girls and 50 boys) aged between 16 and 23 years from 8 high schools were interviewed in 17 focus groups that were segregated by gender. Interview data were analysed using qualitative content analysis. Boys and girls communicated differently about risks. Peer-group conformity appeared stronger among boys than girls. Boys did not spontaneously relate risks to their snowmobile activities, while girls did. Boys focused upon training, coping and balance between control and lack of control while driving. Girls talked about risks, were aware of risks and sought to avoid risky situations, in contrast to boys. Boys' risk communication in groups was about how to manage challenging situations. Their focus overall was on trying to maintain control while simultaneously testing their limits. Three risk categories emerged: those who drive as they ought to (mostly girls), those who occasionally take some risks (boys and girls) and those who are extreme risk-takers (a smaller number of boys). Perceptions of and communication about risk are related to gender, peer group and familiarity with risk-taking when snowmobiling. Northern Norwegian boys' driving behaviour highlights a specific need for risk reduction, but this must also draw upon factors such as acceptance of social and cultural codes and common sense related to snowmobiling.

  17. Cost and Performance Comparison of an Earth-Orbiting Optical Communication Relay Transceiver and a Ground-Based Optical Receiver Subnet

    Science.gov (United States)

    Wilson, K. E.; Wright, M.; Cesarone, R.; Ceniceros, J.; Shea, K.

    2003-01-01

    Optical communications can provide high-data-rate telemetry from deep-space probes with subsystems that have lower mass, consume less power, and are smaller than their radio frequency (RF) counterparts. However, because optical communication is more affected by weather than is RF communication, it requires ground station site diversity to mitigate the adverse effects of inclement weather on the link. An optical relay satellite is not affected by weather and can provide 24-hour coverage of deep-space probes. Using such a relay satellite for the deep-space link and an 8.4-GHz (X-band) link to a ground station would support high-data-rate links from small deep-space probes with very little link loss due to inclement weather. We have reviewed past JPL-funded work on RF and optical relay satellites, and on proposed clustered and linearly dispersed optical subnets. Cost comparisons show that the life cycle costs of a 7-m optical relay station based on the heritage of the Next Generation Space Telescope is comparable to that of an 8-station subnet of 10-m optical ground stations. This makes the relay link an attractive option vis-a-vis a ground station network.

  18. Reliability assessment of fiber optic communication lines depending on external factors and diagnostic errors

    Science.gov (United States)

    Bogachkov, I. V.; Lutchenko, S. S.

    2018-05-01

    The article deals with the method for the assessment of the fiber optic communication lines (FOCL) reliability taking into account the effect of the optical fiber tension, the temperature influence and the built-in diagnostic equipment errors of the first kind. The reliability is assessed in terms of the availability factor using the theory of Markov chains and probabilistic mathematical modeling. To obtain a mathematical model, the following steps are performed: the FOCL state is defined and validated; the state graph and system transitions are described; the system transition of states that occur at a certain point is specified; the real and the observed time of system presence in the considered states are identified. According to the permissible value of the availability factor, it is possible to determine the limiting frequency of FOCL maintenance.

  19. Visible light communication using DC-biased optical filter bank multi-carrier modulation

    KAUST Repository

    Chen, Rui

    2018-03-19

    Filter bank multicarrier (FBMC) has become a promising candidate to replace conventional orthogonal frequency-division multiplexing (OFDM) scheme in 5G technology due to its better spectral confinement which results in a reduced inter-channel interference (ICI). However, the viability of using FBMC in visible light communication has not been verified. In this work we present the first experimental validation of the DC-biased optical filter bank multicarrier (DCO-FBMC) modulation scheme over a free-space optical channel. Under different receiving powers, up to three times bit error rate performance improvement has been achieved using DCO-FBMC with different overlapping factors compared to that of conventional DCO-OFDM.

  20. Confidence range estimate of extended source imagery acquisition algorithms via computer simulations. [in optical communication systems

    Science.gov (United States)

    Chen, CHIEN-C.; Hui, Elliot; Okamoto, Garret

    1992-01-01

    Spatial acquisition using the sun-lit Earth as a beacon source provides several advantages over active beacon-based systems for deep-space optical communication systems. However, since the angular extend of the Earth image is large compared to the laser beam divergence, the acquisition subsystem must be capable of resolving the image to derive the proper pointing orientation. The algorithms used must be capable of deducing the receiver location given the blurring introduced by the imaging optics and the large Earth albedo fluctuation. Furthermore, because of the complexity of modelling the Earth and the tracking algorithms, an accurate estimate of the algorithm accuracy can only be made via simulation using realistic Earth images. An image simulator was constructed for this purpose, and the results of the simulation runs are reported.

  1. Blind third-order dispersion estimation based on fractional Fourier transformation for coherent optical communication

    Science.gov (United States)

    Yang, Lin; Guo, Peng; Yang, Aiying; Qiao, Yaojun

    2018-02-01

    In this paper, we propose a blind third-order dispersion estimation method based on fractional Fourier transformation (FrFT) in optical fiber communication system. By measuring the chromatic dispersion (CD) at different wavelengths, this method can estimation dispersion slope and further calculate the third-order dispersion. The simulation results demonstrate that the estimation error is less than 2 % in 28GBaud dual polarization quadrature phase-shift keying (DP-QPSK) and 28GBaud dual polarization 16 quadrature amplitude modulation (DP-16QAM) system. Through simulations, the proposed third-order dispersion estimation method is shown to be robust against nonlinear and amplified spontaneous emission (ASE) noise. In addition, to reduce the computational complexity, searching step with coarse and fine granularity is chosen to search optimal order of FrFT. The third-order dispersion estimation method based on FrFT can be used to monitor the third-order dispersion in optical fiber system.

  2. Hybrid optical CDMA-FSO communications network under spatially correlated gamma-gamma scintillation

    DEFF Research Database (Denmark)

    Jurado-Navas, Antonio; Raddo, Thiago R.; Garrido-Balsells, José María

    2016-01-01

    In this paper, we propose a new hybrid network solution based on asynchronous optical code-division multiple-access (OCDMA) and free-space optical (FSO) technologies for last-mile access networks, where fiber deployment is impractical. The architecture of the proposed hybrid OCDMA-FSO network...... is thoroughly described. The users access the network in a fully asynchronous manner by means of assigned fast frequency hopping (FFH)-based codes. In the FSO receiver, an equal gain-combining technique is employed along with intensity modulation and direct detection. New analytical formalisms for evaluating...... can successfully achieve error-free ABER levels for the three scenarios considered as long as forward error correction (FEC) algorithms are employed. Therefore, OCDMA-FSO networks can be a prospective alternative to deliver high-speed communication services to access networks with deficient fiber...

  3. Visible light communication using DC-biased optical filter bank multi-carrier modulation

    KAUST Repository

    Chen, Rui; Park, Kihong; Shen, Chao; Ng, Tien Khee; Ooi, Boon S.; Alouini, Mohamed-Slim

    2018-01-01

    Filter bank multicarrier (FBMC) has become a promising candidate to replace conventional orthogonal frequency-division multiplexing (OFDM) scheme in 5G technology due to its better spectral confinement which results in a reduced inter-channel interference (ICI). However, the viability of using FBMC in visible light communication has not been verified. In this work we present the first experimental validation of the DC-biased optical filter bank multicarrier (DCO-FBMC) modulation scheme over a free-space optical channel. Under different receiving powers, up to three times bit error rate performance improvement has been achieved using DCO-FBMC with different overlapping factors compared to that of conventional DCO-OFDM.

  4. Design and performance evaluation of 1-by-64 multimode interference power splitter for optical communications

    DEFF Research Database (Denmark)

    Rasmussen, Thomas; Rasmussen, Jesper Kiel; Povlsen, Jørn Hedegaard

    1995-01-01

    A 1-by-64 multimode interference power splitter in SiO2 has been designed for use in fiber-optics communication systems. The splitter exhibits a minimum loss of 0.5 db and a uniformity of 1.7 dB at a wavelength of 1.55 μm. The polarization sensitivity is below 0.14 dB, the reflection level below...... -55 dB, and the optical bandwidth 30 nm. The fabrication tolerances are ±0.1 mm on the length and ±3.5 μm on the width of the multimode section of the splitter. In comparison with a branching-type splitter it is found that the designed device is approximately 30% shorter than the branching-type device...

  5. Hermitian symmetry free optical-single-carrier frequency division multiple access for visible light communication

    Science.gov (United States)

    Azim, Ali W.; Le Guennec, Yannis; Maury, Ghislaine

    2018-05-01

    Optical-orthogonal frequency division multiplexing (O-OFDM) is an effective scheme for visible light communications (VLC), offering a candid extension to multiple access (MA) scenarios, i.e., O-OFDMA. However, O-OFDMA exhibits high peak-to-average power ratio (PAPR), which exacerbates the non-linear distortions from the light emitting diode (LED). To overcome high PAPR while sustaining MA, optical-single-carrier frequency-division multiple access (O-SCFDMA) is used. For both O-OFDMA and O-SCFDMA, Hermitian symmetry (HS) constraint is imposed in frequency-domain (FD) to obtain a real-valued time-domain (TD) signal for intensity modulation-direct detection (IM-DD) implementation of VLC. Howbeit, HS results in an increase of PAPR for O-SCFDMA. In this regard, we propose HS free (HSF) O-SCFDMA (HSFO-SCFDMA). We compare HSFO-SCFDMA with several approaches in key parameters, such as, bit error rate (BER), optical power penalty, PAPR, quantization, electrical power efficiency and system complexity. BER performance and optical power penalty is evaluated considering multipath VLC channel and taking into account the bandwidth limitation of LED in combination with its optimized driver. It is illustrated that HSFO-SCFDMA outperforms other alternatives.

  6. Orbital-angular-momentum photons for optical communication in non-Kolmogorov atmospheric turbulence

    Science.gov (United States)

    Wei, Mei-Song; Wang, Jicheng; Zhang, Yixin; Hu, Zheng-Da

    2018-06-01

    We investigate the effects of non-Kolmogorov atmospheric turbulence on the transmission of orbital-angular-momentum single photons for different turbulence aberrations in optical communication, via the channel capacity. For non-Kolmogorov model, the characteristics of atmosphere turbulence may be determined by different cases, including the increasing altitude, the mutative index-of-refraction structure constant and the power-law exponent of non-Kolmogorov spectrum. It is found that the influences of low-order aberrations, including Z-tilt, defocus, astigmatism, and coma aberrations, are different and the turbulence Z-tilt aberration plays a more important role in the decay of the signal.

  7. Simple statistical channel model for weak temperature-induced turbulence in underwater wireless optical communication systems

    KAUST Repository

    Oubei, Hassan M.

    2017-06-16

    In this Letter, we use laser beam intensity fluctuation measurements to model and describe the statistical properties of weak temperature-induced turbulence in underwater wireless optical communication (UWOC) channels. UWOC channels with temperature gradients are modeled by the generalized gamma distribution (GGD) with an excellent goodness of fit to the measured data under all channel conditions. Meanwhile, thermally uniform channels are perfectly described by the simple gamma distribution which is a special case of GGD. To the best of our knowledge, this is the first model that comprehensively describes both thermally uniform and gradient-based UWOC channels.

  8. A new LDPC decoding scheme for PDM-8QAM BICM coherent optical communication system

    Science.gov (United States)

    Liu, Yi; Zhang, Wen-bo; Xi, Li-xia; Tang, Xian-feng; Zhang, Xiao-guang

    2015-11-01

    A new log-likelihood ratio (LLR) message estimation method is proposed for polarization-division multiplexing eight quadrature amplitude modulation (PDM-8QAM) bit-interleaved coded modulation (BICM) optical communication system. The formulation of the posterior probability is theoretically analyzed, and the way to reduce the pre-decoding bit error rate ( BER) of the low density parity check (LDPC) decoder for PDM-8QAM constellations is presented. Simulation results show that it outperforms the traditional scheme, i.e., the new post-decoding BER is decreased down to 50% of that of the traditional post-decoding algorithm.

  9. On the performance of free-space optical communication systems with multiuser diversity

    KAUST Repository

    Yang, Liang

    2014-09-01

    Free space optical (FSO) communication has become a cost-effective method to provide high data rates. However, the turbulence-induced fading limits its application to short range applications. To address this, we propose a multiuser diversity (MD) FSO scheme in which the Nth best user is selected and the channel fluctuations can be effectively exploited to produce a selection diversity gain. More specifically, we first present the statistics analysis for the considered system over weak atmospheric turbulence channels. Based on these statistics, the outage probability, bit-error rate performance, and coverage are analyzed.

  10. Subcarrier MPSK/MDPSK modulated optical wireless communications in lognormal turbulence

    KAUST Repository

    Song, Xuegui

    2015-03-01

    Bit-error rate (BER) performance of subcarrier Mary phase-shift keying (MPSK) and M-ary differential phase-shift keying (MDPSK) is analyzed for optical wireless communications over the lognormal turbulence channels. Both exact BER and approximate BER expressions are presented. We demonstrate that the approximate BER, which is obtained by dividing the symbol error rate by the number of bits per symbol, can be used to estimate the BER performance with acceptable accuracy. Through our asymptotic analysis, we derive closed-form asymptotic BER performance loss expression for MDPSK with respect to MPSK in the lognormal turbulence channels. © 2015 IEEE.

  11. Optical code division multiple access secure communications systems with rapid reconfigurable polarization shift key user code

    Science.gov (United States)

    Gao, Kaiqiang; Wu, Chongqing; Sheng, Xinzhi; Shang, Chao; Liu, Lanlan; Wang, Jian

    2015-09-01

    An optical code division multiple access (OCDMA) secure communications system scheme with rapid reconfigurable polarization shift key (Pol-SK) bipolar user code is proposed and demonstrated. Compared to fix code OCDMA, by constantly changing the user code, the performance of anti-eavesdropping is greatly improved. The Pol-SK OCDMA experiment with a 10 Gchip/s user code and a 1.25 Gb/s user data of payload has been realized, which means this scheme has better tolerance and could be easily realized.

  12. Fibercore AstroGain fiber: multichannel erbium doped fibers for optical space communications

    Science.gov (United States)

    Hill, Mark; Gray, Rebecca; Hankey, Judith; Gillooly, Andy

    2014-03-01

    Fibercore have developed AstroGainTM fiber optimized for multichannel amplifiers used in optical satellite communications and control. The fiber has been designed to take full advantage of the photo-annealing effect that results from pumping in the 980nm region. The proprietary trivalent structure of the core matrix allows optimum recovery following radiation damage to the fiber, whilst also providing a market leading Erbium Doped Fiber Amplifier (EDFA) efficiency. Direct measurements have been taken of amplifier efficiency in a multichannel assembly, which show an effective photo-annealing recovery of up to 100% of the radiation induced attenuation through excitation of point defects.

  13. A configurable FPGA FEC unit for Tb/s optical communication

    DEFF Research Database (Denmark)

    Andersen, Jakob Dahl; Larsen, Knud J.; Bering Bøgh, Christian

    2017-01-01

    Decoding of FEC (forward error correction) for optical communication beyond 1 Tb/s is investigated. A configurable single FPGA solution is presented having configurations supporting bit-rates in the range from 40 Gb/s to 1.6 Tb/s. The design allows for trade-offs of bit-rate, footprint, and latency...... within the resources of the FPGA. A proof-of-concept lab experiment at 40 Gb/s was conducted and pre-FEC — post-FEC performance validated with simulated results....

  14. 375-nm ultraviolet-laser based non-line-of-sight underwater optical communication

    KAUST Repository

    Sun, Xiaobin

    2018-05-04

    For circumventing the alignment requirement of line-of-sight (LOS) underwater wireless optical communication (UWOC), we demonstrated a non-line-of-sight (NLOS) UWOC link adequately enhanced using ultraviolet (UV) 375-nm laser. Path loss was chosen as a figure-of-merit for link performance in this investigation, which considers the effects of geometries, water turbidity, and transmission wavelength. The experiments suggest that path loss decreases with smaller azimuth angles, higher water turbidity, and shorter wavelength due in part to enhanced scattering utilizing 375-nm radiation. We highlighted that it is feasible to extend the current findings for long distance NLOS UWOC link in turbid water, such as harbor water.

  15. New role for communication fibre optic cables in water utility for leak detection on main water pipeline

    Directory of Open Access Journals (Sweden)

    Graovac Radojica M.

    2015-01-01

    Full Text Available During construction of main water pipeline it is usual practice to lay fibre optic communication cable along water pipe. This cable is one of the up to date communication media which is used for the connection purposes of water control SCADA equipment as well as for establishing of telephone communication between water utility plants. By developing of new electronic equipment known as DTS (Distributed Temperature Sensing and DAS (Distributed Acoustic Sensing equipment it has been opened the possibility, with this equipment and by utilizing of dedicated optical fibres of optical fibre communication cable as a sensor, to detect leakage point by temperature monitoring or monitoring of acoustic changes along water pipeline (as detection of temperature change of soil at leakage point or detection of acoustic change at leakage point.

  16. Deep-space and near-Earth optical communications by coded orbital angular momentum (OAM) modulation.

    Science.gov (United States)

    Djordjevic, Ivan B

    2011-07-18

    In order to achieve multi-gigabit transmission (projected for 2020) for the use in interplanetary communications, the usage of large number of time slots in pulse-position modulation (PPM), typically used in deep-space applications, is needed, which imposes stringent requirements on system design and implementation. As an alternative satisfying high-bandwidth demands of future interplanetary communications, while keeping the system cost and power consumption reasonably low, in this paper, we describe the use of orbital angular momentum (OAM) as an additional degree of freedom. The OAM is associated with azimuthal phase of the complex electric field. Because OAM eigenstates are orthogonal the can be used as basis functions for N-dimensional signaling. The OAM modulation and multiplexing can, therefore, be used, in combination with other degrees of freedom, to solve the high-bandwidth requirements of future deep-space and near-Earth optical communications. The main challenge for OAM deep-space communication represents the link between a spacecraft probe and the Earth station because in the presence of atmospheric turbulence the orthogonality between OAM states is no longer preserved. We will show that in combination with LDPC codes, the OAM-based modulation schemes can operate even under strong atmospheric turbulence regime. In addition, the spectral efficiency of proposed scheme is N2/log2N times better than that of PPM.

  17. Effects of communication strategy training on EFL students’ performance in small-group discussions

    Directory of Open Access Journals (Sweden)

    Stuart Benson

    2013-10-01

    Full Text Available In recent years, a number of studies have been conducted with regard to communication strategy training and performance on communicative tasks (Lam, 2009; Nakatani, 2010; Naughton, 2006. This study aims to add to the literature by examining how two strategies, clarifying/confirming and extending a conversation, and two methods of teaching the strategies, affected the interactional sequences and overall group discussion performance of EFL students at a university in Japan. Pre and posttreatment small-group discussions were recorded for assessment, and a stimulated recall interview was administered to determine the participants’ perceptions of their learning and language use. Posttest results reveal that the experimental groups that were taught predetermined phrases aimed at clarifying/confirming and extending a conversation employed such phrases more frequently than the control group. However, this employment of phrases did not lead to higher gains in group discussion skills as the control group enjoyed the largest gains from pre to posttest. The researchers consider the findings in light of previous research, and conclude with recommendations for future research on the topic with special regard to research design.

  18. Erbium-based optical coherent transient correlator for the 1.5-micron communication bands

    Science.gov (United States)

    Harris, Todd Louis

    2001-08-01

    Correlators are needed in communications, memory, and signal processing applications to perform cross- correlations for tasks such as address-header decoding for data-packet switching, spread spectrum and code division multiple access communication, associative memory, database searching, and pattern recognition. Correlators based on optical coherent transients, Fourier theory, and holography can potentially perform real-time correlations with multi-phase encoded information at gigahertz bandwidths, a capability conventional electronics lack. The first operation of spatial-spectral holographic correlators in the 1.5-gm communication bands was demonstrated at 1536 nm using Er3+:Y 2SiO5 and the correlator processed multi-phase encoded optical pulses. Real-time decoding of 20-bit binary-phase-shift key encoded address-header pulses is demonstrated using stimulated photon echoes in a phase-matched crossed-beam configuration; this function is required for coherent transient optical data routing and packet switching. Optical 30-symbol quadriphase-shift keyed (QPSK) and binary-phase-shift keyed (BPSK) codes were processed, and the results demonstrated the ability of such correlators to process QPSK codes and BPSK codes with the same apparatus. The high-fidelity correlations exhibit the low sidelobe characteristics expected for the codes used. The 4I15/2 and 4I13/2 crystal field levels of 0.005% Er3+:Y2O3 were measured by absorption and laser excited fluorescence on oriented samples. Site selective fluorescence distinguished transitions of Er3+ in crystallographic sites of C2 and C3i symmetry. The paramagnetic g-tensors for ions in sites of C2 symmetry were measured by orientation dependent Zeeman absorption spectroscopy. For the lowest crystal field level of 4I15/2 the g-tensor principal x-axis in the (100) plane is tipped +2.06° from [001] and principal g-values are: gz = 11.93, gx = 1.603, and gy = 4.711. For the lowest crystal field level of 4I13/2 the g

  19. Electronic Support Groups: An Open Line of Communication in Contested Illness.

    Science.gov (United States)

    Murphy, Michael; Kontos, Nicholas; Freudenreich, Oliver

    Patients with functional somatic syndromes are often difficult to treat. The relationship between doctors and patients can be strained, which limits communication. Instead, patients often communicate with each other over the Internet in electronic support groups. This perspective summarizes studies of patient-to-patient communication over the Internet and uses the concept of contested illness to provide insights into the experiences of patients with functional somatic disorders. Conflict between a patient and their physician is a key feature of functional somatic syndromes. Physicians and patients do not have a shared understanding or appreciation of the patient's experiences. Patients with functional somatic syndromes often value their own embodied experience over medical knowledge. At the same time, they remain deeply invested in finding a "good doctor" who believes that the patient is suffering, agrees with their conception of the cause, and assents to the treatment as directed by the patient. Electronic support groups reinforce these beliefs. Patients may benefit from a compromising, collaborative approach that is realistic about the limitations of medical knowledge. However, physicians should not engage in unsafe treatment practices. Electronic support groups exist for a wide range of illnesses and the issues that rise to the surface in functional somatic syndromes likely occur to some extent with almost every patient. Copyright © 2016 The Academy of Psychosomatic Medicine. Published by Elsevier Inc. All rights reserved.

  20. Using the combination refraction-reflection solid to design omni-directional light source used in underwater wireless optical communication

    Science.gov (United States)

    Rao, Jionghui; Yao, Wenming; Wen, Linqiang

    2015-10-01

    Underwater wireless optical communication is a communication technology which uses laser as an information carrier and transmits data through water. Underwater wireless optical communication has some good features such as broader bandwidth, high transmission rate, better security, anti—interference performance. Therefore, it is promising to be widely used in the civil and military communication domains. It is also suitable for high-speed, short-range communication between underwater mobile vehicles. This paper presents a design approach of omni-directional light source used in underwater wireless optical communication, using TRACEPRO simulation tool to help design a combination solid composed of the lens, conical reflector and parabolic reflector, and using the modulated DPSS green laser in the transmitter module to output the laser beam in small divergence angles, after expanded by the combination refraction-reflection solid, the angle turns into a space divergence angle of 2π, achieving the omni-directional light source of hemisphere space, and test in the air and underwater, the result shows that the effect is fine. This paper analyzes the experimental test in the air and water, in order to make further improvement of the uniformity of light distribution, we optimize the reflector surface parameters of combination refraction-reflection solid and test in the air and water. The result shows that omni-directional light source used in underwater wireless optical communication optimized could achieve the uniformity of light distribution of underwater space divergence angle of 2π. Omni-directional light source used in underwater wireless optical communication designed in this paper has the characteristics of small size and uniformity of light distribution, it is suitable for application between UUVs, AUVs, Swimmer Delivery Vehicles (SDVs) and other underwater vehicle fleet, it realizes point-to-multipoint communications.

  1. Analysis of activity of information inquired group on radioecology and public communication in Ozersk (the town of nuclear industry)

    International Nuclear Information System (INIS)

    Govyrina, E.

    2000-01-01

    The Information Inquiry Group on Radioecology and Public Communication is a branch of the Department of Production Association Mayak. Mayak was formed in 1989. The main tasks as well as main functions of the group are presented. (author)

  2. Group Communication through Computers. Volume 1: Design and Use of the FORUM System. IFF Report R-32.

    Science.gov (United States)

    Vallee, Jacques; And Others

    To explore the feasibility and usefulness of group communication via computer, a system called FORUM was constructed and used in research and management tasks using ARPANET, an international computer network. Working softward and data regarding the dynamics of groups using network communication were developed, and a prototype hardware system for…

  3. 76 FR 13438 - In the Matter of AdAl Group, Inc., Com/Tech Communications Technologies, Inc., Dialog Group, Inc...

    Science.gov (United States)

    2011-03-11

    ... Communications Technologies, Inc., Dialog Group, Inc., Eurogas, Inc., Golden Books Family Entertainment, Inc. (n/k/a GB Holdings Liquidation, Inc.), Information Management Technologies Corporation, Interiors, Inc... accurate information concerning the securities of Com/Tech Communications Technologies, Inc. because it has...

  4. Secure Communications in High Speed Fiber Optical Networks Using Code Division Multiple Access (CDMA) Transmission

    Energy Technology Data Exchange (ETDEWEB)

    Han, I; Bond, S; Welty, R; Du, Y; Yoo, S; Reinhardt, C; Behymer, E; Sperry, V; Kobayashi, N

    2004-02-12

    This project is focused on the development of advanced components and system technologies for secure data transmission on high-speed fiber optic data systems. This work capitalizes on (1) a strong relationship with outstanding faculty at the University of California-Davis who are experts in high speed fiber-optic networks, (2) the realization that code division multiple access (CDMA) is emerging as a bandwidth enhancing technique for fiber optic networks, (3) the realization that CDMA of sufficient complexity forms the basis for almost unbreakable one-time key transmissions, (4) our concepts for superior components for implementing CDMA, (5) our expertise in semiconductor device processing and (6) our Center for Nano and Microtechnology, which is where the majority of the experimental work was done. Here we present a novel device concept, which will push the limits of current technology, and will simultaneously solve system implementation issues by investigating new state-of-the-art fiber technologies. This will enable the development of secure communication systems for the transmission and reception of messages on deployed commercial fiber optic networks, through the CDMA phase encoding of broad bandwidth pulses. CDMA technology has been developed as a multiplexing technology, much like wavelength division multiplexing (WDM) or time division multiplexing (TDM), to increase the potential number of users on a given communication link. A novel application of the techniques created for CDMA is to generate secure communication through physical layer encoding. Physical layer encoding devices are developed which utilize semiconductor waveguides with fast carrier response times to phase encode spectral components of a secure signal. Current commercial technology, most commonly a spatial light modulator, allows phase codes to be changed at rates of only 10's of Hertz ({approx}25ms response). The use of fast (picosecond to nanosecond) carrier dynamics of semiconductors

  5. Patterns of call communication between group-housed zebra finches change during the breeding cycle.

    Science.gov (United States)

    Gill, Lisa F; Goymann, Wolfgang; Ter Maat, Andries; Gahr, Manfred

    2015-10-06

    Vocal signals such as calls play a crucial role for survival and successful reproduction, especially in group-living animals. However, call interactions and call dynamics within groups remain largely unexplored because their relation to relevant contexts or life-history stages could not be studied with individual-level resolution. Using on-bird microphone transmitters, we recorded the vocalisations of individual zebra finches (Taeniopygia guttata) behaving freely in social groups, while females and males previously unknown to each other passed through different stages of the breeding cycle. As birds formed pairs and shifted their reproductive status, their call repertoire composition changed. The recordings revealed that calls occurred non-randomly in fine-tuned vocal interactions and decreased within groups while pair-specific patterns emerged. Call-type combinations of vocal interactions changed within pairs and were associated with successful egg-laying, highlighting a potential fitness relevance of calling dynamics in communication systems.

  6. Communication and Collective Consensus Making in Animal Groups via Mechanical Interactions

    Science.gov (United States)

    Várkonyi, Péter L.

    2011-06-01

    Mechanical constraints have a strong influence on the dynamics and structure of granular aggregations. The contact forces within dense suspensions of active particles may give rise to intriguing phenomena, including anomalous density fluctuations, long-range orientational ordering, and spontaneous pattern formation. Various authors have proposed that these physical phenomena contribute to the ability of animal groups to move coherently. Our systematic numerical simulations confirm that spontaneous interactions of elongated individuals can trigger oriented motion in small groups. They are, however, insufficient in larger ones, despite their significant imprint on the group's internal structure. It is also demonstrated that preferred directions of motion of a minority of group members can be communicated to others solely by mechanical interactions. These findings strengthen the link between pattern formation in active nematics and the collective decision making of social animals.

  7. On the influence of latency estimation on dynamic group communication using overlays

    Science.gov (United States)

    Vik, Knut-Helge; Griwodz, Carsten; Halvorsen, Pål

    2009-01-01

    Distributed interactive applications tend to have stringent latency requirements and some may have high bandwidth demands. Many of them have also very dynamic user groups for which all-to-all communication is needed. In online multiplayer games, for example, such groups are determined through region-of-interest management in the application. We have investigated a variety of group management approaches for overlay networks in earlier work and shown that several useful tree heuristics exist. However, these heuristics require full knowledge of all overlay link latencies. Since this is not scalable, we investigate the effects that latency estimation techqniues have ton the quality of overlay tree constructions. We do this by evaluating one example of our group management approaches in Planetlab and examing how latency estimation techqniues influence their quality. Specifically, we investigate how two well-known latency estimation techniques, Vivaldi and Netvigator, affect the quality of tree building.

  8. 12.5 Gb/s multi-channel broadcasting transmission for free-space optical communication based on the optical frequency comb module.

    Science.gov (United States)

    Tan, Jun; Zhao, Zeping; Wang, Yuehui; Zhang, Zhike; Liu, Jianguo; Zhu, Ninghua

    2018-01-22

    A wide-spectrum, ultra-stable optical frequency comb (OFC) module with 100 GHz frequency intervals based on a quantum dot mode locked (QDML) laser is fabricated by our lab, and a scheme with 12.5 Gb/s multi-channel broadcasting transmission for free-space optical (FSO) communication is proposed based on the OFC module. The output power of the OFC is very stable, with the specially designed circuit and the flatness of the frequency comb over the span of 6 nm, which can be limited to 1.5 dB. Four channel wavelengths are chosen to demonstrate one-to-many channels for FSO communication, like optical wireless broadcast. The outdoor experiment is established to test the bit error rate (BER) and eye diagrams with 12.5 Gb/s on-off keying (OOK). The indoor experiment is used to test the highest traffic rate, which is up to 21 Gb/s for one-hop FSO communication. To the best of our knowledge, this scheme is the first to propose the realization of one-to-many broadcasting transmission for FSO communication based on the OFC module. The advantages of integration, miniaturization, channelization, low power consumption, and unlimited bandwidth of one-to-many broadcasting communication scheme, shows promising results on constructing the future space-air-ground-ocean (SAGO) FSO communication networks.

  9. Improving Continuous-Variable Measurement-Device-Independent Multipartite Quantum Communication with Optical Amplifiers*

    Science.gov (United States)

    Guo, Ying; Zhao, Wei; Li, Fei; Huang, Duan; Liao, Qin; Xie, Cai-Lang

    2017-08-01

    The developing tendency of continuous-variable (CV) measurement-device-independent (MDI) quantum cryptography is to cope with the practical issue of implementing scalable quantum networks. Up to now, most theoretical and experimental researches on CV-MDI QKD are focused on two-party protocols. However, we suggest a CV-MDI multipartite quantum secret sharing (QSS) protocol use the EPR states coupled with optical amplifiers. More remarkable, QSS is the real application in multipartite CV-MDI QKD, in other words, is the concrete implementation method of multipartite CV-MDI QKD. It can implement a practical quantum network scheme, under which the legal participants create the secret correlations by using EPR states connecting to an untrusted relay via insecure links and applying the multi-entangled Greenberger-Horne-Zeilinger (GHZ) state analysis at relay station. Even if there is a possibility that the relay may be completely tampered, the legal participants are still able to extract a secret key from network communication. The numerical simulation indicates that the quantum network communication can be achieved in an asymmetric scenario, fulfilling the demands of a practical quantum network. Additionally, we illustrate that the use of optical amplifiers can compensate the partial inherent imperfections of detectors and increase the transmission distance of the CV-MDI quantum system.

  10. Computer-mediated and face-to-face communication in metastatic cancer support groups.

    Science.gov (United States)

    Vilhauer, Ruvanee P

    2014-08-01

    To compare the experiences of women with metastatic breast cancer (MBC) in computer-mediated and face-to-face support groups. Interviews from 18 women with MBC, who were currently in computer-mediated support groups (CMSGs), were examined using interpretative phenomenological analysis. The CMSGs were in an asynchronous mailing list format; women communicated exclusively via email. All the women were also, or had previously been, in a face-to-face support group (FTFG). CMSGs had both advantages and drawbacks, relative to face-to-face groups (FTFGs), for this population. Themes examined included convenience, level of support, intimacy, ease of expression, range of information, and dealing with debilitation and dying. CMSGs may provide a sense of control and a greater level of support. Intimacy may take longer to develop in a CMSG, but women may have more opportunities to get to know each other. CMSGs may be helpful while adjusting to a diagnosis of MBC, because women can receive support without being overwhelmed by physical evidence of disability in others or exposure to discussions about dying before they are ready. However, the absence of nonverbal cues in CMSGs also led to avoidance of topics related to death and dying when women were ready to face them. Agendas for discussion, the presence of a facilitator or more time in CMSGs may attenuate this problem. The findings were discussed in light of prevailing research and theories about computer-mediated communication. They have implications for designing CMSGs for this population.

  11. Generalized statistical criterion for distinguishing random optical groupings from physical multiple systems

    International Nuclear Information System (INIS)

    Anosova, Z.P.

    1988-01-01

    A statistical criterion is proposed for distinguishing between random and physical groupings of stars and galaxies. The criterion is applied to nearby wide multiple stars, triplets of galaxies in the list of Karachentsev, Karachentseva, and Shcherbanovskii, and double galaxies in the list of Dahari, in which the principal components are Seyfert galaxies. Systems that are almost certainly physical, probably physical, probably optical, and almost certainly optical are identified. The limiting difference between the radial velocities of the components of physical multiple galaxies is estimated

  12. Hybrid microtransmitter for free-space optical spacecraft communication: design, manufacturing, and characterization

    Science.gov (United States)

    Lotfi, Sara; Palmer, Kristoffer; Kratz, Henrik; Thornell, Greger

    2009-02-01

    Optical intra-communication links are investigated by several currently operational qualification missions. Compared with RF communication systems, the optical domain obtains a wider bandwidth, enables miniaturized spacecraft and reduced power consumption. In this project, a microtransmitter is designed and manufactured for formation flying spacecraft with transmission rates of 1 Gbit/s. Simulations in Matlab and Simulink show that a BER of 10-9 can be achieved with aperture sizes of 1 cm and a transmitter output peak power of 12 mW for a distance of 10 km. The results show that the performance of the communication link decreases due to mechanical vibrations in the spacecraft together with a narrow laser beam. A dual-axis microactuator designed as a deflectable mirror has been developed for the laser beam steering where the fabrication is based on a double-sided, bulk micromachining process. The mirror actuates by joints consisting of v-grooves filled with SU-8 polymer. The deflection is controlled by integrated resistive heaters in the joints causing the polymer to expand thermally. Results show that the mirror actuates 20-30° in the temperature interval 25-250°C. Flat Fresnel lenses made of Pyrex 7740 are used to collimate the laser beam. These lenses are simulated in the Comsol software and optimized for a 670 nm red VCSEL. The lenses are manufactured using lithography and reactive ion etching. All tests are made in a normal laboratory environment, but the effect of the space environment is discussed.

  13. UHD Video Transmission over Bi-Directional Underwater Wireless Optical Communication

    KAUST Repository

    Al-Halafi, Abdullah; Shihada, Basem

    2018-01-01

    In this paper, we experimentally demonstrate for the first time a bi-directional underwater wireless optical communication system that is capable of transmitting an ultra high definition real-time video using a downlink channel while simultaneously receiving the feedback messages on the uplink channel. The links extend up to 4.5 m using QPSK, 16-QAM and 64-QAM modulations. The system is built using software defined platforms connected to TO-9 packaged pigtailed 520 nm directly modulated green laser diode (LD) with 1.2 GHz bandwidth as the optical transmitter for video streaming on the downlink, and an avalanche photodiode (APD) module as the downlink receiver. The uplink channel is connected to another pigtailed 450 nm directly modulated blue LD with 1.2 GHz bandwidth as the optical uplink transmitter for the feedback channel, and to a second APD as the uplink receiver. We perform laboratory experiments on different water types. The measured throughput is 15 Mbps for QPSK, and 30 Mbps for both 16-QAM and 64-QAM. We evaluate the quality of the received live video streams using Peak Signal-to-Noise Ratio and achieve values up to 16 dB for 64-QAM when streaming UHD video in harbor II water and 22 dB in clear ocean.

  14. UHD Video Transmission over Bi-Directional Underwater Wireless Optical Communication

    KAUST Repository

    Al-Halafi, Abdullah

    2018-04-02

    In this paper, we experimentally demonstrate for the first time a bi-directional underwater wireless optical communication system that is capable of transmitting an ultra high definition real-time video using a downlink channel while simultaneously receiving the feedback messages on the uplink channel. The links extend up to 4.5 m using QPSK, 16-QAM and 64-QAM modulations. The system is built using software defined platforms connected to TO-9 packaged pigtailed 520 nm directly modulated green laser diode (LD) with 1.2 GHz bandwidth as the optical transmitter for video streaming on the downlink, and an avalanche photodiode (APD) module as the downlink receiver. The uplink channel is connected to another pigtailed 450 nm directly modulated blue LD with 1.2 GHz bandwidth as the optical uplink transmitter for the feedback channel, and to a second APD as the uplink receiver. We perform laboratory experiments on different water types. The measured throughput is 15 Mbps for QPSK, and 30 Mbps for both 16-QAM and 64-QAM. We evaluate the quality of the received live video streams using Peak Signal-to-Noise Ratio and achieve values up to 16 dB for 64-QAM when streaming UHD video in harbor II water and 22 dB in clear ocean.

  15. Experimental Characterization of Close-Emitter Interference in an Optical Camera Communication System.

    Science.gov (United States)

    Chavez-Burbano, Patricia; Guerra, Victor; Rabadan, Jose; Rodríguez-Esparragón, Dionisio; Perez-Jimenez, Rafael

    2017-07-04

    Due to the massive insertion of embedded cameras in a wide variety of devices and the generalized use of LED lamps, Optical Camera Communication (OCC) has been proposed as a practical solution for future Internet of Things (IoT) and smart cities applications. Influence of mobility, weather conditions, solar radiation interference, and external light sources over Visible Light Communication (VLC) schemes have been addressed in previous works. Some authors have studied the spatial intersymbol interference from close emitters within an OCC system; however, it has not been characterized or measured in function of the different transmitted wavelengths. In this work, this interference has been experimentally characterized and the Normalized Power Signal to Interference Ratio (NPSIR) for easily determining the interference in other implementations, independently of the selected system devices, has been also proposed. A set of experiments in a darkroom, working with RGB multi-LED transmitters and a general purpose camera, were performed in order to obtain the NPSIR values and to validate the deduced equations for 2D pixel representation of real distances. These parameters were used in the simulation of a wireless sensor network scenario in a small office, where the Bit Error Rate (BER) of the communication link was calculated. The experiments show that the interference of other close emitters in terms of the distance and the used wavelength can be easily determined with the NPSIR. Finally, the simulation validates the applicability of the deduced equations for scaling the initial results into real scenarios.

  16. Experimental Characterization of Close-Emitter Interference in an Optical Camera Communication System

    Science.gov (United States)

    Chavez-Burbano, Patricia; Rabadan, Jose; Perez-Jimenez, Rafael

    2017-01-01

    Due to the massive insertion of embedded cameras in a wide variety of devices and the generalized use of LED lamps, Optical Camera Communication (OCC) has been proposed as a practical solution for future Internet of Things (IoT) and smart cities applications. Influence of mobility, weather conditions, solar radiation interference, and external light sources over Visible Light Communication (VLC) schemes have been addressed in previous works. Some authors have studied the spatial intersymbol interference from close emitters within an OCC system; however, it has not been characterized or measured in function of the different transmitted wavelengths. In this work, this interference has been experimentally characterized and the Normalized Power Signal to Interference Ratio (NPSIR) for easily determining the interference in other implementations, independently of the selected system devices, has been also proposed. A set of experiments in a darkroom, working with RGB multi-LED transmitters and a general purpose camera, were performed in order to obtain the NPSIR values and to validate the deduced equations for 2D pixel representation of real distances. These parameters were used in the simulation of a wireless sensor network scenario in a small office, where the Bit Error Rate (BER) of the communication link was calculated. The experiments show that the interference of other close emitters in terms of the distance and the used wavelength can be easily determined with the NPSIR. Finally, the simulation validates the applicability of the deduced equations for scaling the initial results into real scenarios. PMID:28677613

  17. Experimental Evaluation of Unicast and Multicast CoAP Group Communication

    Directory of Open Access Journals (Sweden)

    Isam Ishaq

    2016-07-01

    Full Text Available The Internet of Things (IoT is expanding rapidly to new domains in which embedded devices play a key role and gradually outnumber traditionally-connected devices. These devices are often constrained in their resources and are thus unable to run standard Internet protocols. The Constrained Application Protocol (CoAP is a new alternative standard protocol that implements the same principals as the Hypertext Transfer Protocol (HTTP, but is tailored towards constrained devices. In many IoT application domains, devices need to be addressed in groups in addition to being addressable individually. Two main approaches are currently being proposed in the IoT community for CoAP-based group communication. The main difference between the two approaches lies in the underlying communication type: multicast versus unicast. In this article, we experimentally evaluate those two approaches using two wireless sensor testbeds and under different test conditions. We highlight the pros and cons of each of them and propose combining these approaches in a hybrid solution to better suit certain use case requirements. Additionally, we provide a solution for multicast-based group membership management using CoAP.

  18. COMMUNICATIONS

    CERN Multimedia

    L. Taylor and D. Barney

    2010-01-01

    CMS Centres, Outreach and the 7 TeV Media Event The new CMS Communications group is now established and is addressing three areas that are critical to CMS as it enters the physics operations phase: - Communications Infrastructure, including almost 50 CMS Centres Worldwide, videoconferencing systems, and CERN meeting rooms - Information systems, including the internal and external Web sites as well as the document preparation and management systems - Outreach and Education activities, including working with print, radio and TV media, visits to CMS, and exhibitions. The group has been active in many areas, with the highest priority being accorded to needs of CMS operations and preparations for the major media event planned for 7 TeV collisions. Unfortunately the CMS Centre@CERN suffered a major setback when, on 21st December, a cooling water pipe froze and burst on the floor above the CMS Centre main room. Water poured through the ceiling, flooding the floor and soaking some of the consoles, before e...

  19. COMMUNICATIONS

    CERN Multimedia

    A. Petrilli

    2013-01-01

    The organisation of the Open Days at the end of September was the single biggest effort of the CMS Communications Group this year. We would like to thank all volunteers for their hard work to show our Point 5 facilities and explain science and technology to the general public. During two days more than 5,000 people visited the CMS detector underground and profited from the surface activities, which included an exhibition on CMS, a workshop on superconductivity, and an activity for our younger visitors involving wooden Kapla blocks. The Communications Group took advantage of the preparations to produce new CMS posters that can be reused at other venues. Event display images have been produced not just for this occasion but also for other exhibits, education purposes, publications etc. During the Open Days, Gilles Jobin, 2012 winner of CERN Collide@CERN prize, performed his Quantum show in Point 5, with the light installation of German artist Julius von Bismarck. Image 3: CERN Open Days at CMS wel...

  20. Task Group on Computer/Communication Protocols for Bibliographic Data Exchange. Interim Report = Groupe de Travail sur les Protocoles de Communication/Ordinateurs pour l'Exchange de Donnees Bibliographiques. Rapport d'Etape. May 1983.

    Science.gov (United States)

    Canadian Network Papers, 1983

    1983-01-01

    This preliminary report describes the work to date of the Task Group on Computer/Communication protocols for Bibliographic Data Interchange, which was formed in 1980 to develop a set of protocol standards to facilitate communication between heterogeneous library and information systems within the framework of Open Systems Interconnection (OSI). A…