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IEEE Sensors Journal

Quantum-Enhanced Signal-to-Noise Ratio Fiber Bending Sensor Utilizing Intensity Correlated Pulse Twin Beams

Hailong Wang, Qiong Fan, Chunliu Zhao, Xiong Zhang, Zhaokun Wang, Jun Chen, Yan Shi, Shangzhong Jin

Published Dec 15, 2021• 10 citations
Publisher

Abstract

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 of$85.1~\mu \text{m}$,$74.9~\mu \text{m}$, and$67.3~\mu \text{m}$, 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 with$67.3~\mu \text{m}$waist 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.

DOI
10.1109/jsen.2021.3135925

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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.
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.
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.
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.
Motivated by the pursuit of a simple system to produce a continuous variable non-classical light source for long-distance quantum communication, we construct an all-fiber source of pulsed twin beams in the 1550 nm band by using a high gain fiber optical parametric amplifier. The intensity-difference noise of the twin beams is below the shot noise limit by 3.1 dB (10.4 dB after correction for losses). A detailed study reveals a number of limiting factors for noise reduction. Therefore, further noise reduction will be feasible once care is taken for these limiting factors.
The optical shot-noise limit of a laser beam represents the classical limit in precision and signal to noise ratio achievable in optical sensors and imaging systems. It is known that quantum states of light, such as squeezed light and quantum correlated twin beams can be used to enhance precision and signal to noise ratio to beyond this limit. This promises optical sensors with fundamentally superior performance to the state of the art. While quantum-enhanced signal to noise ratio has been demonstrated with macroscopic powers of squeezed probe beam, demonstrations of quantum enhanced precision have remained at extremely low powers of light (femto-Watts). Here we will give examples where increasing SNR with quantum light is not sufficient to increase precision and we will review proof of principle experiments that have demonstrated sub shot noise precision, including for absorption spectroscopy and imaging. We will also report our efforts to achieve this sub-shot-noise precision performance for transmission measurement with ~0.1mW of average probe power, equating to ~10W peak power in a pulsed experiment. Time permitting, we will discuss how integrated optics and integrated electronics enables 10s GHz bandwidth in the detection of squeezed light, for integrated quantum sensor technology.
We report generation of pulsed twin beams of light through optical parametric amplification in a fiber Sagnac loop. By pumping the Sagnac loop with picosecond pulses at a wavelength near the zero-dispersion wavelength of the fiber, we achieve phase-matched nondegenerate four-wave mixing with gain. For a gain of 2.2, the intensity noises of the amplified signal and the generated idler (conjugate) pulses are found to be correlated by 5.0 dB, and the subtracted noise drops below the shot-noise limit by 1.1 dB (2.6 dB when corrected for losses). We have investigated the gain dependence of the quantum-noise reduction as well as of the intensity noises of the amplified signal and idler pulses. As the gain increases, we observe the onset of excess noise on the idler pulses.