Practical limits of coherent receivers for unamplified 100Gb/s applications

The impact of noise sources on the performance of a coherent receiver for loss-limited links is demonstrated. With GFEC, -29.1dBm receiver sensitivity is achieved for 112-Gb/s PM-QPSK format. For shared laser architectures, asymmetric power splitting favoring the transmitter is shown to result in optimum link budget.