BALANCED DETECTION OF TURBO-CODED OPTICAL PPM CDMA SYSTEM

摘要

In this paper, the performance of coherence multiplexed CM) turbo-coded optical PPM CDMA network is evaluated in terms of bit-error-rate (BER), number of users (K) and for various interleaver lengths (TV) taking into account the effects of the thermal noise ad shot noise of APD detectors. For a fixed K(=10), theBERofa CM system is reduced by an order of 10~(-5) than that of the single-ended direct detection system. For a typical data rate of 1Gb/s, and a specified BER of 10~(-6), it is found that the number of simultaneous users increases to 50. Turbo decoding is done using Log-MAP algorithm with different interleaver lengths of N=10, 50, 100 resulting in the reduction of BER to 10~(-9), 10~(-10) and 10~(-11) respectively and by applying performance bounds on the turbo-coded system, the maximum number of iterations to reach a BER of 10~(-14) are limited to four in this system.