Bragg gratings on InGaAsP/InP waveguides as polarizationindependent optical filters

The fabrication and operation of Bragg gratings for future wavelength-division multiplexing (WDM) devices in integrated optical circuits are discussed. Crosstalk attenuation of more than 20 dB with respect to the optical power and spectral bandwidths of up to 2.2 nm were achieved. Polarization-independent operation of the gratings, an important qualification for their operation in fiber optical transmission systems, was demonstrated with a filter bandwidth of 0.2 nm at -10 dB and channel spacings as small as 1 nm