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Journal of Lightwave Technology

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

Hailong Wang, Zehua Chen, Siyuan Ma, Dongxu Wang, Tenghui Mao, Yajuan Zhang, Zhao Chunliu

Published Sep 23, 2024• 9 citations
Publisher

Abstract

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−1respectively 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.

DOI
10.1109/jlt.2024.3466236

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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−1respectively 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.
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.
A quantum-enhanced fiber curvature sensor based on single-mode fiber (SMF) taper exploiting intensity-correlated pulse twin beams has been proposed and experimentally realized. The curvature can be measured by intensity difference noise power and degree of intensity difference squeezing which are tailored by the bending-induced loss of one beam’s SMF taper. In addition, the three different waist diameters of SMF tapers, i. e.,52.12 μm52.12~ \boldsymbol {\mu }\text{m}52.12 μm,61.68 μm61.68~ \boldsymbol {\mu }\text{m}61.68 μm, and 67.54μm\boldsymbol {\mu }\text{m}μmrespectively have been prepared using a fusion splicer. Finally, the maximum measured sensitivity enhancement of 4.42 dB/m−1and signal-to-noise ratio enhancement of 2.0 dB have been experimentally implemented through intensity difference measurement technique compared with the corresponding classical counterpart (double-channel light source). In contrast to other curvature sensors, this proposal has the advantages of high sensitivity, ease of fabrication, simple structure, and low cost.
To overcome the precision limitation imposed by classical common noise and standard quantum limit (SQL) in traditional classical sensing, a single-multi-single-mode (SMS) fiber optic sensor based on the combination of self-imaging principle and two-mode squeezed light source is proposed and experimentally demonstrated. The SMS sensor is constructed by fusing a multi-mode fiber in between two single-mode fiber segments. By utilizing an intensity-correlated twin beam source (signal and idler), the signal beam acts as the sensing probe interacting with the SMS sensor, while the idler beam serves as a reference to implement balanced differential measurement. The experimental results explicitly demonstrate a maximum signal-to-noise ratio enhancement of 1.196±0.012 dB and 1.194±0.019 dB for strain sensing (0 με to 2077.9 με) and temperature sensing (30°C to 110°C), respectively. These findings confirm the sensor's capability for real-time, high-precision sub-Poissonian measurements, particularly for practical applications in electromagnetic-immune and the requirements of simultaneous discrimination of temperature and strain.
We have experimentally proposed and implemented a fiber bending sensor with quantum-enhanced signal-to-noise ratio (SNR), which stems from the combination of single-mode fiber (SMF) taper and intensity correlated pulse twin beams. One beam from pulse twin beams is coupled into the SMF taper to obtain a bending-induced loss, while the other beam is also attenuated correspondingly by a variable optical attenuator to ensure maximum noise cancellation. Along this line, intensity-difference noise power between pulse twin beams is always reduced below standard quantum limit (SQL), and thus a higher SNR value compared with the corresponding double-channel light source can be realized. In this work, the three different SMF tapers with the waist diameters of85.1 μm85.1~\mu \text{m}85.1 μm,74.9 μm74.9~\mu \text{m}74.9 μm, and67.3 μm67.3~\mu \text{m}67.3 μm, respectively have been prepared by a fusion splicer. The experimental results show that in the bending range of 0–20 m−1, the SMF taper with67.3 μm67.3~\mu \text{m}67.3 μmwaist diameter shows the highest sensitivity of 0.105 dB/m−1, the resolution of 0.095 m−1, and its SNR value is enhanced by a maximal factor of 2.84 dB compared with the corresponding classical counterpart. The present bending proposal may find potential applications in monitoring the bending deformation of building structure, roadbed settlement, medical and health, etc.
The injection of squeezed light can be used to improve the sensitivity of an interferometer beyond the limit imposed by the zero-point fluctuation of the electromagnetic field. Here, we report on the realization of such a quantum-enhanced interferometer with a fiber-based Sagnac topology. Continuous wave squeezed states at 1550 nm with a noise reduction of 6.4 dB below shot noise were produced by type I optical parametric amplification and subsequently injected into the dark port of the interferometer. A reduction of the interferometer shot noise by 4.5 dB was observed, and the enhancement of the signal-to-noise ratio for a phase modulation signal generated within the interferometer could be demonstrated. We achieved a 95% fiber transmission for the squeezed states, which suggests that corresponding fiber-based quantum metrology and communication systems are feasible.
Fiber-optic sensors enable high-sensitivity measurements of various physical parameters. Here, we demonstrate a quantum-enhanced interrogation of an all-fiber-optic Fabry-Perot resonator, employing entangled two-photon interference to probe directly strain-induced optical phase shifts. The resonator is interrogated by a narrow-linewidth laser that is frequency-locked to its resonance mode, thereby exploiting the cavity's inherent sensitivity to variations in the fiber length. To access the phase fluctuations transferred to the interrogation field due to external perturbations on the sensor, we implement an in-fiber Mach-Zehnder interferometer readout. This configuration allows the sensor to operate both with classical coherent light and with entangled photon pairs generated via spontaneous parametric down-conversion. Harnessing two-photon entangled states corresponding to an N = 2 NOON state, we experimentally demonstrate a reduction of the measurement noise below the standard quantum limit. These results provide clear evidence of the quantum advantage in enhancing fiber-optic sensors under practical constraints on optical power.