Strategies for realizing optical CDMA for dense, high-speed, long span, optical network applications

Since the mid 1990s, the role of optical CDMA has expanded from local area networks to longer span, telecommunication-type networks. In order to play a significant role in these longer span, denser, higher data rate networks, optical CDMA code set must 1) have at least as many codes as dense wavelen gth division multiplexing (WDM) (i.e., more than eight codes); 2) operate a t high data rates (i.e., greater than 2.5 Gb/s); and 3) propagate with high fidelity over the installed or installable fiber links. Most approaches to optical CDMA require narrow pulses, which are more susceptible to fiber im pairments and may have lower spectral efficiency than conventional WDM modu lation schemes such as nonreturn-to-zero (NRZ), so they do not meet these n ew requirements. Therefore, we have formulated a strategy which simultaneou sly increases the number of good codes (resulting in higher density) and re duces their code length (i.e., decreasing the number of time slots required thus enabling higher data rates for a given chip time): the strategy of ma trix codes. In this paper, we describe the design of a set of eight matrix codes for operation at 2.5 Gb/s and evaluate their propagation over an exis ting 214 km network link by means of computer simulation, The results indic ate that the codes propagate well if dispersion management is used. The pap er also discusses a strategy for managing the multiaccess interference (MAI ) in a bursty traffic environment.