Utilization In Optical Code Division Multiple Access Networks Microform

In the process of studying O-CDMA through the spectral and network utilization, a number of specific original contributions are made: an impairment in O-CDMA networks---the spectral crosstalk---is studied for two different system configurations; a procedure is designed to evaluate the performance of O-CDMA signature sequences in realistic networking environments; and a technique is developed to allocate adaptively signature sequences which leads to an order of magnitude improvement in performance and provides a quality-of-service contract on the bit-error rate. In local-area networks with a high traffic load, an O-CDMA system with static allocation of signature sequences is shown to have a higher network utilization than a competing WDMA scheme. It is demonstrated that by increasing the adaptability of the next generation of O-CDMA systems, the performance may be further improved. This work provides the tools-the analytical frameworks, figures of merit and mechanisms for adaptability-that may be used to design and evaluate these future O-CDMA systems. This work investigates how O-CDMA exploits resources in multiwavelength optical fiber networks. For the first time, it examines this question fundamentally from the perspective of both transmission and network connectivity. Given the processing gain of O-CDMA, the spectral width of the transmitted signal may become appreciable relative to the spacing between adjacent channels. The assumption traditionally made in optical communications that these channels may be treated independently breaks down in this case. In this work, a figure of merit---the spectral utilization---together with an analytical framework are developed to treat the bandwidth of O-CDMA networks as a whole, rather than as a collection of independent segments. The studies of O-CDMA with this spectral utilization metric suggest that the technology cannot compete with wavelength-division multiple-access (WDMA) at the physical layer taken in isolation; however, this is not the sole measure of the value of a network. Factors such as channel or receiver contention and the statistics of the traffic being transported do not manifest themselves in the physical layer yet are important factors in determining the performance of an optical network. A different figure of merit---the network utilization---is therefore used to compare and evaluate various O-CDMA and WDMA systems in a networking context.

Code-division multiple access (CDMA) technology has been widely adopted in cell phones. Its astonishing success has led many to evaluate the promise of this technology for optical networks. This field has come to be known as Optical CDMA (OCDMA). Surveying the field from its infancy to the current state, Optical Code Division Multiple Access: Fundamentals and Applications offers the first comprehensive treatment of OCDMA from technology to systems. The book opens with a historical perspective, demonstrating the growth and development of the technologies that would eventually evolve into today's optical networks. Building on this background, the discussion moves to coherent and incoherent optical CDMA coding techniques and performance analysis of these codes in fiber optic transmission systems. Individual chapters provide detailed examinations of fiber Bragg grating (FBG) technology including theory, design, and applications; coherent OCDMA systems; and incoherent OCDMA systems. Turning to implementation, the book includes hybrid multiplexing techniques along with system examples and conversion techniques to connect networks that use different multiplexing platforms, state-of-the-art integration technologies, OCDMA network security issues, and OCDMA network architectures and applications, including a look at possible future directions. Featuring contributions from a team of international experts led by a pioneer in optical technology, Optical Code Division Multiple Access: Fundamentals and Applications places the concepts, techniques, and technologies in clear focus for anyone working to build next-generation optical networks.

Optical code division multiple access (OCDMA) communication network technology will play an important role in future optical networks, such as optical access and metropolitan area networks. OCDMA technology can also be applied to implement optical signal multiplexing and label switching on backbone networks. Optical Code Division Multiple Access Communication Networks - Theory and Applications introduces the code theory of OCDMA, the methods and technologies of OCDMA encoding and decoding, the theory and methods of analyzing OCDMA systems with various receiver models and realizing multiple-class services with different bit rates and QoS. In addition, OCDMA network architectures, protocols and applications are discussed in detail. The up-to-date theoretical and experimental results on OCDMA systems and networks are also reported. A large number of encoding/decoding examples and many analysis and simulation results of code and system performances are given. It is a valuable text and/or reference book for postgraduates majoring in telecommunication and photonics to obtain a well-knit theoretical foundation and for engineers in R&D and management of optical communications. Dr. Yin is an Associate Professor of the School of Electronics Engineering and Computer Science at Peking University, China, and was a Visiting Research Fellow of Optoelectronics Research Centre (ORC) at University of Southampton, UK. Dr. Richardson is a Professor for optical communications and Deputy Director of ORC at University of Southampton, UK, and is responsible for much of the ORC's fiber related activities.

Code Division Multiple Access (CDMA) has been proposed for optical fibre networks to a achieve high-speed connectivity, asynchronous operation and network control simplifications. Traditionally, all-optical devices have been proposed to encode, decode and process CDMA signals because the bandwidth in the optical medium is higher than electronic processing techniques. Today's advances in integrated circuit technologies coupled with bandwidth efficient circuit topologies, may provide robust alternatives for CDMA over fibre applications. This thesis overs two areas of work. First, a new circuit for encoding and decoding incoherent CDMA signals in the electrical domain is proposed. This structure makes use of the high bandwidth of distributed amplifier-like topologies to achieve very wideband operation. As proof of concept, a distributed transversal filter was designed with a commercial available GaAs MMIC process; modelling results show feasibility of CDMA encoding/decoding at 40 GChip/s employing transistors with cut-off frequencies of 60 GHz. Limitations and potential practical applications of these design ideas are discussed. The second part of the thesis focuses on the impact of the time skewing due to optical-fibre Group Velocity Difference in Wavelength-Hopping Time-Spreading (WHTS) Optical CDMA and the compensation of this impairment through electronic techniques. A new network model was created to assess the impact of such impairment in these systems. Conclusions about the time skewing impact on the auto and cross-correlation properties of the system are extracted. This model was employed to assess the use of an electronic distributed transversal filters as time skewing compensator in Optical CDMA networks. Finally, an experimental setup of a WHTS Optical CDMA network was built to analyze the effect of time skewing and to assess the practical feasibility of its compensation with a distributed transversal filter. The Fiber Bragg Grating based system comprises 2.5 GBit/s transmission (20 GChip/s) with five wavelengths. Conclusions about the practical limitations are derived and presented.

"A comprehensive guide to optical fiber communications, from the basic principles to the latest developments in OCDMA for Next-Generation Fiber-to-the-Home (FTTH) systems. Part I starts off with the fundamentals of light propagation in optical fibers, including multiple access protocols, and their enabling techniques. Part II is dedicated to the practical perspectives of Next-Generation Fiber-to-the-Home (FTTH) technology. It covers the key building blocks of OCDMA, devices such as optical encoders and decoders, signal impairments due to noise, and data confidentiality, a unique property of OCDMA. This is followed by hybrid system architectures with TDM and WDM and practical aspects such as system cost, energy efficiency and long-reach PONs. Featuring the latest research, with cutting-edge coverage of system design, optical implementations, and experimental demonstrations in test beds, this text is ideal for students, researchers and practitioners in the industry seeking to obtain an up-to-date understanding of optical communication networks"--