Remote Michelson interferometric phase sensor based on dual-core fiber transmission and linear phase demodulation.

We present a remote Michelson interferometric phase sensor based on dual-core fiber transmission and linear phase demodulation. The former allows for synchronous transmission of both sensing signal and reference lights, enabling efficient suppression for the environmental disturbances along the transmission link and for the incoherent phase noise between the two lights. The latter is conducted by two optical phase-locked loops, one of which consists of a fiber stretcher that is used to eliminate the residual phase noises, thus stabilizing the operation point while the other relies on a phase modulator that is used to track the remote phase changes, thus achieving a highly linearized phase demodulation. A remote phase sensing over a 20 km fiber link with less than 3% nonlinear phase error over 3π range has been readily realized, corresponding to more than 10 times extension in a linear phase demodulation range. The proposed system shows great potential in the field of remote phase sensing for a variety of physical quantities.