Photonic integrated circuits

The architecture and performance of two recently demonstrated photonic integrated circuits (PICs) are presented. One is a wavelength-division multiplexing (WDM) source comprising four discretely tunable MQW-DBR lasers which combine to a single MQW amplifier, providing a four-channel high-bit-rate WDM source with a single fiber coupling port. With a channel spacing of 25 angstrom, this PIC has demonstrated 36-km transmission of four simultaneous 2 Gb/s (8 Gb/s composite rate) pseudo-random NRZ intensity modulated channels with only a approximately 1.4 dB crosstalk penalty. Another device is a fully integrated MQW balanced heterodyne receiver PIC. The chip integrates a 4-section 60 angstrom continuously tunable MQW-DBR LO, a directional coupler switch, and two zero-bias MQW waveguide detectors. With the detectors SMA-connected directly to 50Ω commercial amplifiers, in balanced operation this PIC has demonstrated free space beam sensitivities of -42.3 dBm and -39.7 dBm at 108 Mb/s and 200 Mb/s, respectively, for coherent FSK pseudo-random NRZ data. Combined waveguide losses, radiation losses, internal inter-element coupling, and detector η on this chip are only 4.3 dB.