Statistical analysis of fiber-optic CDMA communication systems. II. Incorporating multiple optical amplifiers

For pt. I see ibid., vol.20, no.8, p.1304-16 (2002). In this paper, we study and elaborate on the architectural consideration of using multiple optical amplifiers in an all-optical fiber-optic code-division multiple-access (FO-CDMA) network. Our study and considerations are based on obtaining the statistical characteristic functions for photon-counts of a string of output pulses that constitutes the address code in a FO-CDMA network. Optical orthogonal codes (OOCs) with minimum auto-and cross correlation are employed as the address or signature sequence codes. Our analysis is based on chip-synchronous interference only, which provides an upper bound on the system performance. Shot noise, thermal noise, and extinction ratio are considered in this analysis. Bit error rate (BER) results are obtained using two methods, namely, saddle-point and Gaussian approximations. From our BER analysis, we develop some insight into the optimum distribution of optical amplifiers and their corresponding gain setting parameter. Moreover, the effects of source power, code weight, number of users, bit rate, and amplified spontaneous emission noise are investigated.