New Type of Tunable Optical Filter using InGaAsP/InP Gratings

A new type of tunable optical filter for use in Wavelength Division Multiplexing (WDM) transmission system has been fabricated in the InGaAsP/InP material system for use at 1.55 pm. The device uses tunable reflection gratings in a waveguide to control the channels (4 in this case). Crosstalk levels between 9 dB and 20 dB have been measured, depending on the channel.