Investigation of code reconfigurable fibre Bragg gratings for Optical Code Division Multiple Access (OCDMA) and Optical Packet Switching (OPS) Networks

摘要

This thesis documents my work in the telecommunication system laboratory at the Optoelectronics Research Centre, towards the implementation of code reconfigurable OCDMA and all-optical packet switching nodes based on fibre Bragg grating (FBG) technology. My research work involves characterizing the performance of various gratings, specifically high reflectivity, short chip duration, long code sequences, multiple phase level and tunable superstructured fiber Bragg gratings (SSFBGs), by using the recently proposed Frequency-Resolved Optical Gating technique based on Electro-Absorption Modulator (EAM-FROG). This technology can obtain the complex code profile along the grating, making it a powerful method to understand the thermally-induced code-reconfigurable grating. Efforts have been made to improve the grating design to achieve better system performance. Three different types of FBGs optical encoder/decoder, e.g. conventional discrete phaseshift SSFBGs, code-reconfigurable gratings, and novel continuous phase-shift SSFBGs, have been investigated comparatively, as well as their performance in various optical coding/decoding systems. This thesis also discusses the possibility of reducing multiple access interference (MAI) using a Two-Photon Absorption (TPA) process. The advanced grating devices enable the improvement of system performance. A dynamically reconfigurable optical packet processing system and a 16-channel reconfigurable OCDMA/DWDM system with 50GHz DWDM intervals has been demonstrated.These results highlight the feasibility of FBG-based optical coding/decoding techniques, with improved system flexibility and sustainability.