Tunable wavelength-selective liquid crystal filters for 600-channel FDM system

A tunable wavelength-selective filter is described that is capable of selecting one channel from over 600 channels at a wavelength of 1.47-1.60 mu m by stacking two liquid-crystal Fabry-Perot interferometers, one with a wide tuning range of 127 nm and a broad bandwidth of 3.4 nm and the other with a very narrow bandwidth of 0.07 nm (9 GHz) and a small tuning range of 12 nm. This filter has an efficient finesse of 1800, and it can select one channel from 600 light sources with 0.2-nm (25-GHz) spacing at a beam optics loss of 5 dB.<
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