Chip-Level Modulated BPPM Fiber-Optic Code Division Multiple Access

Abstract

Chip-Level Modulated Binary Pulse Position Modulation (CLM-BPPM) is proposed as a modulation scheme for Fiber-Optic Code Division Multiple Access (FO-CDMA) systems using Optical Orthogonal Code (OOC) for time domain signal spreading. The proposed scheme provides better synchronization and source activity detection at the receiver side as compared to On-Off Keying (OOK). A mathematical expression is derived for the BER of CLM-BPPM using a combinatorial interference pattern analysis approach. The mathematical model is verified using simulation. Numerical results demonstrate that CLM-BPPM has a BER that is very close to OOK. Moreover, increasing the average source activity causes the performance of the CLM-BPPM to approach that of the OOK system with an asymptotic BER equal to the BER of OOK at full user activity.