Circulator-Free Reflection-Type Tunable Optical Dispersion Compensator Using Tandem Arrayed-Waveguide Gratings

A tunable optical dispersion compensator that uses cascaded arrayed-waveguide gratings and an integrated phase shifter is reported. It is a catoptric circuit but does not require a circulator. The dispersion is successfully controlled from +142 to +1148 ps/nm. Error-free transmission is confirmed after dispersion compensation in a transmission experiment using 43 Gbps CSRZ-DQPSK modulation.