Optimal source linewidth in a coherence multiplexed optical fiber communications system

In a fiber-based coherence multiplexed (CM) system, fiber path lengths must be carefully controlled. In an extrinsic reference ladder (ERL) CM system, two optical fibers are required to connect the transmitter array to each receiver. The effect of differential length variations between these two fibers is examined and is found to have significant impact on carrier-to-noise ratio (CNR). It is determined that, for a given differential mismatch length, there is an optimum value of optical source linewidth which maximizes system multiplexing capacity. An expression for the SNR of a certain multichannel digital CM communications system is developed.<
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