Channel coding for asynchronous fiberoptic CDMA communications

Several studies have explored the feasibility and systems performance aspects of a code division multiple access (CDMA) format for fiberoptic networks. Previously discussed CDMA architectures would either have to tolerate a high bit error rate or be forced to use long code sequences in networks with even a moderate number of simultaneous users. The use of long sequences lowers the maximum achievable bit rate or places unrealistic requirements on the system hardware. This paper examines some of the possible improvements to system performance that could be realized by combining the CDMA format with external error correcting codes (ECCs) or a PPM format. It is determined that ECCs can be highly effective in lowering the BER, and/or increasing the achievable information bit rate and number of network users. The results are sufficiently encouraging to conclude that one should seriously consider including ECCs in any practical fiberoptic CDMA network.>