Sensitivity degradation in polarization diversity receivers for lightwave systems

The effect of weighting circuit unidealities on the sensitivity degradation of diversity receivers is examined for synchronous and nonsynchronous detectors. A novel model is developed in which the weighting ratio for each polarization diversity receiver branch can be calculated using practical values. For synchronous detectors, it is shown analytically that the sensitivity degradation is relatively independent of the weighting ratio deviation from the optimum value. The same is also true for nonsynchronous detectors. Results of experiments on a 600 Mb/s single-filter frequency-shift keying (FSK) lightwave system, a 400 Mb/s continuous-phase FSK (CPFSK) lightwave system, and an amplitude-shift keying (ASK) synchronous detection network simulated with a 600 Mb/s baseband system generally support the theoretical results