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Title: Applications of spectrum slicing in optical access networks
Author: Sun, Shaobo
ISNI:       0000 0004 2703 1173
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2010
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Spectrum-slicing (SS) is a novel attractive technique for the implementation of optical access network. Its main advantage compared to the conventional optical network is utilizing spectral slices of a broadband source for different data channels. Since the light sources employed are quite cost effective, this technology is economically attractive to the modern communication system. The major objective of this dissertation is to investigate the performance of systems employing spectrum-slicing, for implementing wavelength division multiplexing (WDM) and optical code division multiple access (OCDMA) in optical access systems. The analysis is conducted mainly through the theoretical model based on the statistics, derived from fundamental chi-square and Gaussian distribution. Firstly, the analysis of an SS-WDM system performance when employing an optical preamplifier receiver is carried out to improve understanding of the SS in a realistic situation where dispersion significantly impacts the signal in transmission. It is shown that there exists an optimum optical bandwidth which minimizes the detection sensitivity for a given error probability caused by two competing effects of inherent signal fluctuation and dispersion. The optically preamplified receiver delivers increased transmission capacity and a substantially improved power budget compared to a pin receiver. The results are obtained using the saddle point approximation and compared to the customary Gaussian approximation, which is found to be reasonably accurate in predicting the optimum bandwidth but conservative in sensitivity predictions. The second part of the work investigates the performance of an SS-OCDMA employing and proposes a supporting adaptive coding scheme developed from prime-hop codes. The concomitant higher-order dispersion, beat noise and multiple access interference in incoherent OCDMA systems become limiting factors to the bit error rate. The major thrusts of the new schemes are to alleviate the performance degradation from these impacts especially to reduce the power loss and the bit error rate (BER) degradation due to higher-order dispersion. Performance comparisons between the adaptive PHC and original PHC schemes indicate that the former is more suitable for use in the considered incoherent system in terms of accommodating more users for a given BER. The proposed adaptive method can be universally applied to mitigate dispersion effects in the similar 2-D OCDMA systems. Within the last part of the work, regular low-density parity-check (LDPC) codes are applied for the first time to a SS-WDM system. An adaptive decoding algorithm of low density parity check (LDPC) codes based on the precise SSWDM noise statistics is developed, which outperforms the decoding with conventional Gaussian model. The simulation results for various code rates show that such a forward error correction scheme provides significant coding gain for a dedicated system in terms of improving the overall transmission capacity and available power budget. The adaptive algorithm of LDPC codes can be generically applied to all the asymmetric channels.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TK Electrical engineering. Electronics Nuclear engineering