Turbo product codes for performance improvement of optical CDMA systems

The application of turbo product codes (TPC) in asynchronous (or synchronous) intensity modulated direct detection optical code division multiple access (CDMA) systems with on-off keying (OOK) is proposed in this study. Optical multiple access interference (OMAI) caused by other users, is the main source of noise that degrades system performance and limits the total number of active users in optical CDMA. The original turbo product decoding algorithm is modified according to the channel model of a direct detection optical CDMA system and it is shown that the implementation of turbo product codes in such a system provides significant improvement of the bit-error rate (BER) permitting a higher number of active users with less complex transmitters and receivers.