Noise properties of a quadrature phase tracker for interferometric optical fiber sensors

The noise performance of an electronic quadrature phase-detection system for interferometric optical fiber sensors is presented. Three noise sources are discussed in this work, namely, synchronous detection-circuit noise, phase-perturbation noise; and additive amplitude noise. We determined the output signal-to-noise ratio (SNR) experimentally as a function of input phase power for each of the three noise sources. For uncorrelated synchronous detection-circuit noise the output SNR increases monotonically with input phase power. For correlated noise the output SNR has distinct peaks due to noise cancellation. System performance is limited by uncorrelated detection-circuit noise which exhibits a threshold behavior in output SNR at a phase shift of 25 mrad/Hz/sup 1/2 /. The phase noise has a more conventional behavior in the sense that SNR gain occurs only at the expense of dynamic performance. Uncorrelated amplitude noise also displays noise cancellation at certain discrete values of input phase, as is the case for correlated synchronous detection-circuit noise. System insensitivity to correlated light-source amplitude noise is evident from the fact that the output SNR is more than 30 dB higher than the input SNR.