Frequency domain detection of coherence multiplexed sensor signals by using an optical loop with a frequency shifter

We describe a frequency domain detection scheme of coherence multiplexed sensor signals by using an optical loop with a frequency shifter. The optical path differences of the sensors are adjusted to integer-multiple of the loop length of the optical loop, and then the the sensor signals are multiplexed in the frequency domain, appearing at the integer-multiple of the working frequency of the frequency shifter. In the experiment, four Michelson-type sensors are successfully multiplexed with the sensitivities of about 2 mrad//spl radic/Hz. The sensitivities are also theoretically calculated which are in good agreement with the experimental results. The optimum design of the optical loop is also discussed.