Coherence Multiplexing System Based on Asymmetric Mach–Zehnder Interferometers for Faraday Sensors

An optical coherence multiplexing system for Faraday sensors is proposed. With an asymmetric Mach-Zehnder (M-Z) interferometer, the linearly polarized light from a Faraday sensor is decomposed into two orthogonal modes, which are interrogated by a path-scanning Michelson interferometer at different path positions. The variations in the intensities of these two modes are utilized to deduce the rotation of the polarization plane, which is related to the measurand tested by the Faraday sensor. By employing multiple asymmetric M-Z interferometers with arm-lengths carefully controlled, the sensing signals of the multiplexed Faraday sensors are obtained and well separated in one scan of the Michelson interferometer.