Four-channel tunable optical notch filter using InGaAsP/InP reflection gratings

A new tunable optical notch filter for use in wavelength division multiplexing (WDM) transmission system has been fabricated in the InGaAsP/InP material system for use at 1.55 μm. 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. System experiments at 150 Mb/s show less than 1 dB crosstalk penalty at 10/sup /spl minus/9/ bit-error rate.