Highly selective FSK receiver for a high channel capacity WDM system using a fiber Fabry Perot or a 2-electrode DFB-LD as the optical filter

The ability of optical fiber to carry large amounts of information can be fully utilized in wavelength division multiplexing (WDM) systems, but significant degradation of transmitted signals occurs when the channel spacing is too small or input power too high. The selectivity of a frequency shift keying (FSK) receiver using a fiber Fabry-Perot filter or a distributed feedback (DFB) laser filter is characterized, and the number of allowable channels, in the authors' system configuration, is determined.