BER and outage probability of DPSK subcarrier intensity modulated free space optics in fully developed speckle.

In this paper a differential phase shift keying (DPSK) subcarrier intensity modulated (SIM) free space optical (FSO) link is considered in negative exponential atmospheric turbulence environment. To mitigate the scintillation effect, the selection combining spatial diversity scheme (SelC) is employed at the receiver. Bit error rate (BER) and outage probability (Pout) analysis are presented with and without the SelC spatial diversity. It is shown that at a BER of 10-6, a maximum diversity gain 25 dB is predicted. And about 60 dBm signal power is required to achieve an outage probability of 10-6, based on a threshold BER of 10-4

A review of modulation techniques for use in a satellite multipath environment

Modulation techniques for use in satellite multipath environmen

Dispensing with channel estimation: differentially modulated cooperative wireless communications

As a benefit of bypassing the potentially excessive complexity and yet inaccurate channel estimation, differentially encoded modulation in conjunction with low-complexity noncoherent detection constitutes a viable candidate for user-cooperative systems, where estimating all the links by the relays is unrealistic. In order to stimulate further research on differentially modulated cooperative systems, a number of fundamental challenges encountered in their practical implementations are addressed, including the time-variant-channel-induced performance erosion, flexible cooperative protocol designs, resource allocation as well as its high-spectral-efficiency transceiver design. Our investigations demonstrate the quantitative benefits of cooperative wireless networks both from a pure capacity perspective as well as from a practical system design perspective

A multicast overlay scheme for wavelength division multiplexed passive optical networks.

Zhang, Yin.Thesis submitted in: December 2008.Thesis (M.Phil.)--Chinese University of Hong Kong, 2009.Includes bibliographical references (leaves 56-60).Abstracts in English and Chinese.Chapter Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Telecommunications network hierarchy --- p.2Chapter 1.2 --- PON architectures for access networks --- p.4Chapter 1.2.1 --- TDM-PON --- p.5Chapter 1.2.2 --- WDM-PON --- p.7Chapter 1.3 --- Data delivery mode in WDM-PON --- p.8Chapter 1.3.1 --- Point-to-point --- p.8Chapter 1.3.2 --- Broadcast --- p.9Chapter 1.3.3 --- Multicast --- p.10Chapter 1.4 --- Motivation of this thesis --- p.10Chapter 1.5 --- Outline of this thesis --- p.13Chapter Chapter 2 --- Previous Multicast Architectures in WDM-PON --- p.14Chapter 2.1 --- Introduction --- p.15Chapter 2.2 --- Previous WDM-PON architectures with multicast capability --- p.15Chapter 2.2.1 --- Subcarrier multiplexing --- p.16Chapter 2.2.2 --- All-optical based multicast enabled architecture --- p.18Chapter 2.3 --- Summary --- p.21Chapter Chapter 3 --- A Multicast enabled WDM-PON Architecture Using ASK-DPSK Orthogonal Modulation --- p.23Chapter 3.1 --- Introduction --- p.24Chapter 3.2 --- System architecture --- p.25Chapter 3.3 --- Experimental Demonstration --- p.27Chapter 3.4 --- Discussion --- p.31Chapter 3.5 --- Summary --- p.36Chapter Chapter 4 --- A WG filtering and its suppression in quaternary ASK-DPSK based multicast enabled WDM-PON --- p.37Chapter 4.1 --- Introduction --- p.38Chapter 4.2 --- Principle of narrowband filtering --- p.38Chapter 4.3 --- Simulation model --- p.40Chapter 4.4 --- Simulation results and discussion --- p.42Chapter 4.4.1 --- Different extinction ratios --- p.43Chapter 4.4.2 --- Different AWG filter shape and bandwidth --- p.47Chapter 4.5 --- Summary --- p.50Chapter Chapter 5 --- Summary and Future Works --- p.51Chapter 5.1 --- Summary of the thesis --- p.52Chapter 5.2 --- Future works --- p.53List of Publications --- p.55BIBLIOGRAPHY --- p.5

Optical packet networks : enabling innovative switching technologies

Les réseaux informatiques avec une grande capacité nécessitent des liaisons de transmission de données rapides et fiables pour prendre en charge les applications web en pleine croissance. Comme le nombre de serveurs interconnectés et la capacité de stockage des médias ne cessent daugmenter, les communications optiques et les technologies de routage sont devenues intéressantes grâce au taux binaire élevé et à lencombrement minimum offert par la fibre optique. Les réseaux optiques à commutation de paquets (OPSNs) offrent une flexibilité accrue dans la gestion de réseau. OPSNs exploitent les convertisseurs de longueur donde accordables (WC) pour minimiser la probabilité de blocage et fournir une allocation dynamique des longueurs donde. Les émetteurs optiques basés sur des sources multi-longueurs donde se présentent comme une solution intéressante en termes de coût, dencombrement et defficacité énergétique par rapport aux autres types de lasers. Les convertisseurs de longueurs donde doivent permettre des taux binaires élevés et une transparence à une grande variété de formats de modulation, tout en offrant une réponse rapide, des niveaux de puissance modérés et un rapport de signal à bruit optique (OSNR) acceptable à la sortie. Plusieurs technologies de conversion de longueur donde ont été proposées dans la littérature. Lutilisation du mélange à quatre ondes (FWM) dans les amplificateurs optiques à semi-conducteurs (SOA) permet lutilisation de faibles niveaux de puissance dentrée et offre une bonne efficacité de conversion ainsi que la possibilité dintégration photonique. Les SOAs offrent donc un excellent compromis par rapport aux autres solutions. Pour couvrir une plus large bande de conversion, nous utilisons le schéma exploitant le FWM avec doubles pompes dans les SOAs. Pour la stabilité de phase, les pompes viennent d’un laser en mode bloqué (QDMLL) qui sert comme source multi-longueurs donde. Deux modes du QDMLL sont sélectionnés par un filtrage accordable et servent comme doubles pompes. Un filtre accordable placé à la sortie du SOA sert à sélectionner le produit du FWM pour le signal final. Nous étudions le convertisseur de longueur donde proposé et comparons sa performance pour différents formats de modulation (modulation dintensité et de phase) et à différents débits binaires (10 et 40 Gbit/s). Le taux derreur binaire, lefficacité de conversion et la mesure de lOSNR sont présentés. Nous démontrons aussi la possibilité de simultanément convertir en longueurs donde les données et l’étiquette. Les données à haut débit et l’étiquette à faible débit se retrouvent dans une seule bande de longueurs d’onde, et ils sont convertis ensemble avec une bonne efficacité. Notre démonstration se concentre sur les performances de conversion, donc les données et létiquette sont des signaux continus plutôt que de paquets optiques. Des mesures de taux derreur binaire ont été effectuées à la fois pour les données et pour létiquette. Nous proposons aussi lutilisation de QDMLL comme source de transmetteurs WDM pour deux applications différentes: unicast et multicast. Nous démontrons aussi sa compatibilité avec le format de transmission DQPSK à haut débit binaire. Nous évaluons la performance du DQPSK en terme de taux derreur binaire et comparons sa performance à celle dune source laser à cavité externe.Large scale computer networks require fast and reliable data links in order to support growing web applications. As the number of interconnected servers and storage media increases, optical communications and routing technologies become interesting because of the high speed and small footprint of optical fiber links. Furthermore, optical packet switched networks (OPSN) provide increased flexibility in network management. Future networks are envisaged to be wavelength dependent routing, therefore OPSN will exploit tunable wavelength converters (WC) to enable contention resolution, reduce wavelength blocking in wavelength routing and switching, and provide dynamic wavelength assignment. Optical transmitters based on multi-wavelength sources are presented as an attrative solution compared to a set of single distributed feedback lasers in terms of cost, footprint and power consumption. Wavelength converters should support high bit rates and a variety of signal formats, have fast setup time, moderate input power levels and high optical signal-to-noise ratio at the output. Several wavelength conversion technologies have been demonstrated. The use of four wave mixing (FWM) in semiconductor optical amplifiers (SOAs) provides low input power levels, acceptable conversion efficiency and the possibility of photonic integration. SOAs therefore offer excellent trade-offs compared to other solutions. To achieve wide wavelength coverage and integrability, we use a dual pump scheme exploiting four-wave mixing in semiconductor optical amplifiers. For phase stability, we use a quantum-dash mode-locked laser (QD-MLL) as a multi-wavelength source for the dual pumps, with tunability provided by the frequency selective filter. We investigate the proposed wavelength converter and compare its performance of wavelength conversion for different non-return-to-zero (NRZ) intensity and phase modulation formats at different bit rates (10 and 40 Gbit/s). Bit error rate, conversion efficiency and optical signal-to-noise ratio measurements are reported. We demonstrate the possibility of tightly packed payload and label wavelength conversion at very high data baud rate over wide tuning range with good conversion efficiency. Our demonstration concentrates on conversion performance, hence continuous payload and label signals were used without gating into packets. Bit error measurements for both payload and label were performed. We propose the use of QD-MLL as multi-wavelength source for WDM unicast and multicast applications and we investigated its compatibility with DQPSK transmission at high bit rate. We quantify DQPSK performance via bit error rate measurements and compare performance to that of an external cavity laser (ECL) source

Hybrid receiver study

The results are presented of a 4 month study to design a hybrid analog/digital receiver for outer planet mission probe communication links. The scope of this study includes functional design of the receiver; comparisons between analog and digital processing; hardware tradeoffs for key components including frequency generators, A/D converters, and digital processors; development and simulation of the processing algorithms for acquisition, tracking, and demodulation; and detailed design of the receiver in order to determine its size, weight, power, reliability, and radiation hardness. In addition, an evaluation was made of the receiver's capabilities to perform accurate measurement of signal strength and frequency for radio science missions

Optical code-division multiple access system and optical signal processing

This thesis presents our recent researches on the development of coding devices, the investigation of security and the design of systems in the optical cod-division multiple access (OCDMA) systems. Besides, the techniques of nonlinear signal processing used in the OCDMA systems fire our imagination, thus some researches on all-optical signal processing are carried out and also summarized in this thesis. Two fiber Bragg grating (FBG) based coding devices are proposed. The first coding device is a superstructured FBG (SSFBG) using ±π/2-phase shifts instead of conventional 0/π-phase shifts. The ±π/2-phase-shifted SSFBG en/decoders can not only conceal optical codes well in the encoded signals but also realize the reutilization of available codes by hybrid use with conventional 0/π-phase-shifted SSFBG en/decoders. The second FBG based coding device is synthesized by layer-peeling method, which can be used for simultaneous optical code recognition and chromatic dispersion compensation. Then, two eavesdropping schemes, one-bit delay interference detection and differential detection, are demonstrated to reveal the security vulnerability of differential phase-shift keying (DPSK) and code-shift keying (CSK) OCDMA systems. To address the security issue as well as increase the transmission capacity, an orthogonal modulation format based on DPSK and CSK is introduced into the OCDMA systems. A 2 bit/symbol 10 Gsymbol/s transmission system using the orthogonal modulation format is achieved. The security of the system can be partially guaranteed. Furthermore, a fully-asynchronous gigabit-symmetric OCDMA passive optical network (PON) is proposed, in which a self-clocked time gate is employed for signal regeneration. A remodulation scheme is used in the PON, which let downstream and upstream share the same optical carrier, allowing optical network units source-free. An error-free 4-user 10 Gbit/s/user duplex transmission over 50 km distance is reazlied. A versatile waveform generation scheme is then studied. A theoretical model is established and a waveform prediction algorithm is summarized. In the demonstration, various waveforms are generated including short pulse, trapezoidal, triangular and sawtooth waveforms and doublet pulse. ii In addition, an all-optical simultaneous half-addition and half-subtraction scheme is achieved at an operating rate of 10 GHz by using only two semiconductor optical amplifiers (SOA) without any assist light. Lastly, two modulation format conversion schemes are demonstrated. The first conversion is from NRZ-OOK to PSK-Manchester coding format using a SOA based Mach-Zehnder interferometer. The second conversion is from RZ-DQPSK to RZ-OOK by employing a supercontinuum based optical thresholder