Performance evaluation of spectral amplitude coding signature sequences for OCDMA systems

In this paper, we have evaluated the performance of spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) systems. A performance comparison has been made between various OCDMA signature sequences (random diagonal (RD), modified double weight (MDW), and modified quadratic congruence (MQC) codes). Analytical expressions have been used to analyze the bit-error rate (BER) value for each code. Our analysis shows that the system performance of the RD code is better than the MDW and MQC codes in a local area network (LAN) (for active users less than 60). Furthermore, the MDW code is more applicable in a wide area network (WAN) (for active users greater than 60). However, the BER value of the MQC code is more than the RD and the MDW codes. The MQC code shows worse system performance over other SAC OCDMA codes in LAN and WAN access networks. In other words, the value of BER is high and number of users is less than the other SAC codes. Our results indicate that when the number of users (K) is 50, the value of BER is 1×10^-32 for the RD code, while the BER value of 1×10^-26 for the MDW code. In addition, the BER value of 1×10^-13 and 1×10^-9 are obtained at K=100 for MDW, and RD codes, respectively.