CDMA fiber-optic systems with optical hard limiters

The code-division multiple-access (CDMA) technique has recently received substantial attention for fiber-optic communication systems. Simultaneous users are allowed to send their data asynchronously in CDMA fiber-optic systems through the assignment of unique “signature codes.” The multiple-access interference (MAI), which increases with the number of simultaneous users, severely limits the user capacity of the systems. An optical hard limiter can be placed at the front end of the desired receiver to reduce the effects of the MAI. We obtain the bit error probability for the CDMA fiber-optic systems with optical hard limiters. The exact performance analysis is performed and the result is a generalization of a previous analysis. For λ_c=1 codes, the result is not restricted to the case for threshold Th=w, yielding a more general and useful result than that obtained previously. The improvement in the performance from using a hard limiter with prime code and extended prime code is shown. The effect on the choice of decision threshold Th is also examined