Monolithic DQPSK receiver in InP with low polarization sensitivity

We present a monolithic differential quadrature phase-shift keying (DQPSK) receiver in InP consisting of a 1 × 2 coupler, two different-length waveguides, a 2 × 4 coupler, and four photodetectors. We demonstrate a method to reduce the interferometer polarization sensitivity and show preliminary results of 43 Gb/s DQPSK reception.