PSK self-homodyne detection using a pilot carrier for multibit/symbol transmission with inverse-RZ signal

Phase-shift-keying (PSK) self-homodyne modulation and demodulation using a polarization-multiplexed pilot-carrier with an inverse-return-to-zero (RZ) intensity modulation signal for 2-bit/symbol transmission at 20 Gb/s was demonstrated. The pilot-carrier was generated by polarization-modulation in an orthogonal polarization state with respect to a PSK signal in the transmitter, while its polarization state was rotated by 90° in a LiNbO₃-based hybrid module for homodyne detection in the receiver. We confirm that the proposed self-homodyne detection scheme is insensitive to cross-modulation degradation by an inverse-RZ signal with high extinction ratio, thanks to an intensity-noise reduction capability of more than 15 dB in the homodyne-balanced receiver. The proposed scheme offers robust PSK homodyne detection for multibit per symbol formats without using a complex optical phase-locked loop.