Thesis

The impact of WH/TS codes in implementing incoherent OCDMA system

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Awarding institution
  • University of Strathclyde
Date of award
  • 2014
Thesis identifier
  • T13815
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Abstract
  • A viable last-mile solution for high-speed high-capacity optical networks capable of securely supporting a large number of simultaneous users by minimal hardware requirements is needed. Optical code division multiple access (OCDMA) is an advanced multiplexing scheme which provides a more efficient and fairer division of available bandwidth among users in comparison to other techniques such as wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM). As a result, OCDMA has become a very attractive multi-access technique that can be used in local area networks (LAN) and last-mile application. I have built an incoherent OCDMA system, whose performance I investigated, including the influence of chromatic dispersion, timing jitter and the effect of ambient temperature fluctuations on data transmission over a 17-km bidirectional fibre link (a testbed) I designed between Strathclyde and Glasgow University. The OCDMA system is based on two-dimensional wavelength-hopping time-spreading (2D-WH/TS) incoherent OCDMA codes which use multiwavelength picosecond pulses. The encoders/decoders are based on fibre Bragg gratings (FBG) technology and the investigations were carried out at OC-48 (2.5 Gb/s) data rate. The testbed was built to be a fully chromatic dispersion compensated with sub-picosecond accuracy. Synchronisation and timing jitter effects were investigated on OCDMA signal transmitted over 17-km distance. A receiver that incorporates an all-optical clock recovery (AOCR) for synchronisation in incoherent OCDMA systems was developed and demonstrated. The all-optically recovered clock signal was then used to drive optical "time gate" to control a switching window ("a time gate"). This is to pass the autocorrelation peak while blocking the MAI noise to improve system power budget and overall performance.
Resource Type
DOI
Date Created
  • 2014
Former identifier
  • 1040904

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