New approaches to optical code-division multiple access

This thesis focuses on new strategies of designing Optical Code-Division Multiple Access (OCDMA) networks. Specifically, two new spreading code families of 2-dimensional (2D) wavelength-time system are considered: Depth-First Search Codes (DFSC) and Balanced Codes for Differential Detection (BCDD). DFSC utilizes a depth-first search algorithm to generate unipodal codes with maximum unit auto- and cross-correlation properties that are suitable for direct detection. These codes have similar interference-limited bit error rate (BER) performance as most 2D wavelength-time codes, but the algorithm can generate more codes, enabling the full potential of Forward Error Correction (FEC). BCDD defines a new set of high weight antipodal codes with relaxed correlation constraints that is suitable for differential detection. These codes can support approximately twice as many users as the other previously published OCDMA systems. Using a system with 32 wavelengths and 16 time chips operating at OC-12 transmission rates (622Mbps), BCDD can support an aggregate throughput of approximately 136Gbps when proper FEC is applied.Furthermore, studies on the information theoretical capacity of chip synchronous OCDMA channel with Single User Detection (SUD) is conducted to obtain the ultimate throughput that can be achieved. Calculations are done under three assumptions: (i) interference-limited channel, (ii) interference-limited channel with Gaussian noise; or (iii) Gaussian approximated interference channel. In additions, system specific DFSC and BCDD capacity is obtained. These results are used as the basis for comparison among DFSC, BCDD and other previously proposed OCDMA systems. It is found that the maximum throughput of an OCDMA system is limited to about 0.7 bits per OCDMA chip. With the application of turbo code, BCDD can support an aggregate throughput of about 0.42 bits per OCDMA chip