Frequency tracking of tunable liquid-crystal wavelength filter for WDM transmission

The authors show that the drift in the pass-band of a liquid crystal Fabry-Perot tunable filter caused by temperature variations can be controlled by using electronic feedback. The circuit locks onto the wavelength of the incoming signal and adjusts the drive voltage that is applied to the liquid crystal to compensate for any shifts. Bit-error-rate measurements were used to show that the use of such feedback can extend the operating temperature range by tens of degrees. The purpose was to investigate the effect of this modulation on the bit-error-rate in a data transmission system.<>