Noncoherent WDMA/FDMA (wavelength-division multiaccess/frequency-division multiaccess) networks that use tunable filters to select channels are considered. They have the same sensitivity as direct-detection networks, which is about 10 dB less than coherent networks. However, the noncoherent networks are much less complicated, which makes them interesting for multiaccess applications, where cost is more important than sensitivity. The direct-detection sensitivity is sufficient to allow as many as 1000 channels. Some recent research network experiments and progress on essential components for realizing noncoherent FDMA networks are reviewed.
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