Quantum-Enhanced Strain and Curvature Sensing Based on a Birefringent Fiber Sagnac Interferometer

In this work, the combination of an all-fiber two-mode squeezed state light source and Sagnac interferometer for the experimental realization of a quantum-enhanced strain and curvature sensor is presented here. The former can offer intensity-correlated twin beams, whose intensity difference noise is beyond standard quantum limit. The latter can be prepared by splicing a polarization-maintaining fiber between two standard single-mode fibers. Using the intensity interrogation method tracing the intensity variation of the sensing signal beam, we can obtain the following quantum-enhanced experimental results. In the strain sensing, signal-to-noise ratio (SNR) is enhanced by a maximal factor of 1.54 dB compared with the corresponding classical strategy under balanced measurement condition. Under unbalanced measurement condition, SNR and the sensitivity are enhanced by the maximal factors of 1.39 dB and 0.026 dB/μϵ respectively compared with the corresponding classical counterpart. In the curvature sensing, balanced measurement condition can offer a maximal factor of 1.31 dB SNR enhancement, unbalanced measurement condition will bring the maximal factors of 1.36 dB and 3.31 dB/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> respectively enhancement in SNR and sensitivity. These results demonstrate the feasibility of the combination of all-fiber non-classical light source and various fiber-based structures as the strain and curvature sensors for many applications that demands sub-poissonian precise measurements.