Wavelength- and Polarization-Independent Operation of Differential M-ary PSK Receiver Based on Single Delay Interferometer Using 120 degrees Optical Hybrid

Abstract

In this letter, we demonstrate the wavelength- and polarization-independent operation of a receiver for differential quadrature phase-shift-keying and 8-ary phase-shift-keying signals, which utilizes a single delay interferometer made of a 3 x 3 optical coupler. We show that the phase distortion, which occurred in the proposed receiver, can be reduced to less than 2 degrees without any adjustments. This feature enabled us to achieve nearly quantum-limited sensitivities.