Performance evaluation and enhancement of OCDMA systems with broadband light sources

Abstract

In this paper the performance of low complexity optical CDMA systems is evaluated. Beat noise is the main performance limitation for an implementation using an incoherent receiver. Therefore, a channel model with both interference and beat noise is presented. From the channel model a maximum likelihood soft decoding method is derived. The system considered is a passive optical network with tree topology where the headend can use information about the number of active users to improve the receiver performance. In order to simulate systems with forward error correction (FEC) and soft decoding an efficient simulation method is used. The simulations show that the performance is highly overestimated when the beat noise is neglected. The results also show that it is better to use FEC to expand the bandwidth compared with only using CDMA spreading, in particular since the efficiency of FEC can be further increased with soft decoding.