Extended tuning range integrated receivers with grating-assisted codirectional coupler optical filters

In recent years, there has been continuous interest in developing tunable receivers for wavelength-division multiplexed (WDM) systems. A direct-detection receiver with a combination of an optical preamplifier and an optical filter offers possible high sensitivity and selectivity. In this paper, we report on an InP/InGaAsP widely tunable receiver, which integrates a semiconductor optical amplifier (SOA), a tunable two-stage grating-assisted codirectional coupler (GACC) optical filter, and a waveguide photodetector. The integrated device can be continuously tuned for a 45-nm wavelength range, however, side-lobes are higher than desired. With suitable tapering in the GACC sections, it is predicted that the side-lobes of the integrated device can be depressed to be as low as -50 dB