Two-dimensional optical CDMA systems with multi-wavelength pulse modulation and double hard-limiters

In this paper, we present a two-dimensional (2D) optical code-division multiple-access (OCDMA) system with multi-wavelength pulse modulation (MWPM) and double optical hard-limiters (DHL). In the proposed system, each user is sending optical pulses spread in both wavelength and time domains and the receiver is equipped with two optical hard-limiters before and after fiber Bragg grating (FBG) decoders to limit the detrimental effect of the multiple-access interference (MAI) and shot noise at the photo-detectors (PD). Under the assumption of random sequence spreading and Poisson model for shot noise, the performance of the proposed system is analyzed. Analytical and simulation results are in good agreement. They indicate that in a 2D-OCDMA system the MWPM is possible for supporting higher data rates, and that the double optical hard-limiters can significantly improve the system performance