ABSTRACT

In this paper, the effect of optical pulse shape on the performance of direct sequence optical code division multiple access in presence of fiber group velocity dispersion (GVD) and pulse linear chirp is analyzed. In our analysis, chirp-Gaussian shape and chirp-Hyperbolic-Secant shape optical orthogonal codes are employed as address sequence. Avalanche photodiode (APD) is used in an optical correlator receiver. The signal to noise power for the proposed system is evaluated on account of APD short noise, bulk dark current, surface leakage current, thermal noise current, and multiuser access interference noises. The system BER performance is determined as a function of received signal power, number of simultaneous users, fiber length, pulse linear chirp, and pulse-shape. The power penalty suffered by the system is evaluated at BER of 10-9. The numerical results show that the BER performance of the proposed system is highly dependent on the number of simultaneous user, fiber length, pulse linear chirp, and pulse-shape. It is found that, if the effect of GVD is considered, the proposed system performance i.e., BER is degraded. The BER performance of the proposed system also aggravated due to presence of pulse linear chirp. It is also found that the proposed system suffers minimum penalty when chirp-Hyperbolic-Secant shape optical pulse is used instead of chirp-Gaussian shape pulse.