The Effect of Length and Curvature on Quantum-Enhanced Temperature Sensing in a Fiber-Based Sagnac Loop

In this work, we theoretically proposed and experimentally demonstrated the enhanced effect of prior curvature precondition on temperature sensing in a quantum-enhanced sensing system, which is constructed by combining an all-fiber two-mode squeezed light source and a Sagnac loop. By choosing the prior optimum length and curvature of polarization-maintaining fiber inside the Sagnac loop, both signal-to-noise ratio (SNR) and sensitivity can be effectively enhanced. The experimental results are summarized as follows. SNR is enhanced by the factor of 0.38 dB under balanced measurement condition. Under unbalanced measurement condition, the enhanced factors with regard to sensing depth are 0.22 and 2.34 dB for the classical double-channel light source and two-mode squeezed light source, respectively. With the support of curvature precondition, the sensing depth of the former one 15.62 dB is enhanced to 31.49 dB of the latter one by an enhanced factor of 15.87 dB, which is larger than 13.75 dB in the absence of curvature precondition, this enhanced effect still exists in the temperature sensitivity (0.982 dB/°C <1.134 dB/°C) and SNR (0.54 dB <1.7 dB). These results confirm the potential prospects of using the cross effects from other physical quantities to enhance temperature sensing in a quantum-enhanced sensing system.