Coherent/Noncoherent Detection of Coherent Optical Heterodyne DPSK-CDMA and MFSK-CDMA Signals

摘要

The system performance of a coherent optical heterodyne communication system isanalyzed for MFSK-CDMA and DPSK-CDMA signalling. The analysis determines the effect that receiver thermal noise, photodetector shot noise, laser phase noise, and multiple user noise has on the system performance. For the single user system performance, the probability of bit error of the system is calculated as a function of Eb/No for laser linewidth-to-bit rate ratios from 0.1 to 0.01. For both MFSK and DPSK, the system performance is most affected by laser phase noise at higher linewidth-to-bit rate ratios. The multiple user analysis for MFSK-CDMA and DPSK-CDMA is determined by calculating the probability of bit error as a function of the number of users for various laser linewidth-to-bit rate ratios and codelengths. The observations made for the single user case concerning the effects of laser phase noise are also observed for the multiple user case. When the effects of the laser phase noise no longer dominate system performance, then MFSK-CDMA and DPSK-CDMA can be used to increase the user capacity of optical fiber systems. (Author)