Polarization-sensitive intermodal all-fiber sensor using spectrally resolved detection

In this paper we report on the principle of operation of a novel detection scheme for fiber-optic sensors allowing for low-noise simultaneous retrieval of X- and Y-polarized intermodal responses which greatly facilitates conducting two parameter measurement. The scheme is based on powering the sensor using a depolarized partly coherent optical source. It provides low-noise signals and allows for simple simultaneous detection of two channels, for independent phase presetting and for conducting relative measurements. All these features are achieved by spectrally resolving the signal exiting from the sensor and measuring the responses at two different wavelengths. The use of depolarized excitation allows for a low-noise detection while the spectral decoding permits employing a more sophisticated phase tracking in the system.