A generalization of a coherence multiplexing system

Coherence multiplexing is a relatively unknown form of a CDMA-system, especially used in access networks for optical communication systems. Usually a coherence multiplex system uses delay-filters at the transmitter and at the receiver to perform the code. In this paper, an extension to other filter types is described. The performance, in terms of the signal-to-noise ratio, can be calculated. The result is a simple expression in which only the bit-time, the coherence-time of the source and the number of simultaneous users is involved. With the use of a continuous source, the signal to noise ratio will be proportional to the inverse of the square of the number of simultaneous users. Such a system is in fact a spectral code system. Further extension will be made with the use of a pulsed source and by replacing the filters in the previous case by a bank of filters. Each element of that filter bank also has a delay, different for each element, included. It will be shown that in that case the signal-to-noise ratio can be made proportional to the inverse of the number of users instead of the square of the number of users, which means an important improvement with respect to the number of users that can be handled. This system can be named a spectro-temporal code system