Polarization-Insensitive Frequency Shift Keying Optical Heterodyne Receiver Using Discriminator Demodulation

We describe a polarization-state-independent binary frequency shift keying optical heterodyne receiver, achieved by splitting the received signal between two orthogonal polarization axes and combining the signals after demodulation. We consider various receiver configurations using a discriminator with a limiter for applications in which received-signal-envelope fluctuations cannot be ignored and, without a limiter, when the fluctuations are negligible. For applications that require the limiter, we propose a diversity method or a variable-gain limiter that improves the performance of the limiter/discriminator receiver. Our numerical results indicate that, with diversity and a limiter/discriminator structure, we can achieve polarization independence with a system performance which is nearly that of an ideal receiver. Using a discriminator without a limiter, when there is no source of envelope fluctuations other than those due to Gaussian noise, the receiver performance degradation compared to the ideal baseline receiver is 0.5 dB.