| The advances in long haul transmission and optical reach have shifted the bottleneck from the core network to metro and access networks. Optical access network is a promising solution to the already congested access network, advocating the fulfillment of the enormous future requirements of applications and Internet services of the next-generation on demand.;Optical code division multiple Access (O-CDMA) systems are possible strong candidate for future optical access network due to their enhanced data privacy, flexibility, and simplicity of network control, especially when considering the fine granularity of traffic, fine channel granularity; flexible bandwidth management, and ability to support variable Quality-of-Service (QoS).;One major challenge in O-CDMA systems results from the square detection in the optical receivers. Spreading sequences need to be designed in order to support unipolar signaling, hence, limiting the number of codes for a certain code parameters. In addition, the multiple-access-interference (MAI) caused by other users, limits the maximum number of users that can simultaneously operate in the system.;This thesis presents a detailed research on various system structures alleviating the effects of MAI. This paper presents an analytical model quantifying the MAI in the O-CDMA systems for various transmitter/receiver structures including conventional receiver, hard limiting receiver, and code position modulation (CPM) O-CDMA systems; relates the system performance to the MAI; experimentally demonstrates the effects of MAI on the threshold level and a novel technique to monitor the number of users in the system based on estimating the amount of MAI in the system; demonstrates a novel technique "code position modulation" and its variances "double pulse position modulation (2-PPM) and differential pulse position modulation (DPPM)" to increase the spectral efficiency of the system by a factor of 3; and finally introduces and demonstrates various techniques in order to enhance the O-CDMA network performance by enabling variable quality of service, variable bit rate, and interference avoidance.;The techniques presented in this thesis may potentially play key roles in future dynamically reconfigurable optical code division multiple access systems and networks. |
