TEMPERATURE-TUNED ZNS ETALON FILTERS FOR WDM SYSTEMS

Abstract

We report a simple ZnS etalon filter tunable with temperature (5 GHz/-degrees-C) for channel selection and noise filtering in amplified WDM systems. It has large free-spectral-range (30 nm), narrow passband (4.6 angstrom), and low insertion loss (1 dB). The filter has been used for channel selection in a WDM system without any degradation in the receiver sensitivity. When the filter was locked to a desired channel using a simple digital servoloop, it maintained a very stable transmission (maximum drift < 3%) even when the wavelength of transmitter laser was intentionally changed by as much as 1 nm.