An optical extinction ratio monitoring technique for wavelength-division-multiplexed passive optical network systems is proposed. This technique is based on the optical spectrum analysis. It can accurately measure the optical extinction ratio of optical signals and does not change with the transmission distance. In our experiments, the transient chirp hardly affects the measured results if the optical extinction ratio is lower than 7 dB, and the measured errors are less than 0.5 dB.
Microwave and Optical Technology Letters 51(8), pp.1800-1803