A Polarization-Space Michelson Interferometric Fiber-Optic Vibration Sensor

A polarization-space Michelson interferometric fiber-optic vibration sensor is proposed and experimentally demonstrated. A phase-coherent dual-frequency optical pulse with two orthogonal polarization states is generated as transmitted signal. Compared with conventional frequency-shifted dual-pulse-based scheme, a polarization-maintaining vibration sensing unit with an equal arm length configuration is utilized in the proposed method, which contributes to the common mode noise elimination at the receiver and is also beneficial to miniaturization design, anti-acceleration, and large-scale application. A polarization diversity detection is adopted for optical-to-electrical conversion of two polarized beat signals; then, a novel demodulation algorithm is applied based on real-to-imaginary-Kramers-Kronig (RI-KK) receiver and direct phase subtraction. The sensitivity enhancement and phase noise suppression in the proposed system are analyzed. In a proof-of-principle experiment, a system with a background noise level of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.2\times 10^{-{4}}$ </tex-math></inline-formula> rad/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\surd $ </tex-math></inline-formula>Hz and a demodulated signal-to-noise ratio of 43.51 dB ref rad2/Hz at 1 kHz is demonstrated. The phase sensitivity is 17.33 dB ref rad/V, which is improved by two times compared with conventional frequency-shifted dual-pulse-based scheme.