Optical integrated receiver for DQPSK systems

A very compact integrated optical device, including a pair of two-arm Mach-Zehnder interferometers realized in silicon oxynitride technology (SiON), is proposed as a receiver for optical DQPSK transmission systems. A review on high-index contrast SiON technology is given with details on the design, technological realization and optical characterization of the presented device. System measurements, including BER curves, are reported to show the performance of the receiver in a RZ-DQPSK system operating at 10 Gsymbol/s. To reduce impairments due to the frequency mismatch between receiver and transmitter, a dynamic thermal tuning of the receiver has been realized and its contribution to system's penalty reduction is experimentally demonstrated.