Experimental Research On Quantum-enhanced Tapered Optic Fiber Sensors

In optical sensing,shot noise limit（SNL）defines the minimum noise floor achievable by classical sources and can only be surpassed by using Quantum states such as squeezed or entangled states.These states allow for a lower noise floor,which enables the detection of signals below the SNL,thereby increasing the resolution of the sensor.Using quantum state light as the probe light for fiber optic sensors enables quantum-based sensitivity enhancements to be applied to devices already used in practical applications.In this paper,the intensity-correlated twin beams probe taper sensors are used to verify its Quantum enhancement properties in the precise measurement of curvature and temperature.The details are as follows:1.Theoretical research on two intensity modulation models（equilibrium measurement and non-equilibrium measurement）based on intensity-correlated twin beams is carried out,and their working characteristics in the process of quantum precision measurement are analyzed.2.A quantum-enhanced single-tapered fiber curvature sensor is proposed and experimentally verified,which has quantum-enhanced sensitivity and signal-noise ratio.Compared with the double-channel coherent state light source,4.42 d B/m^-1sensitivity enhancement and 2.0 d B signal-noise ratio enhancement are achieved by the non-equilibrium measurement intensity difference detection technique.3.A quantum-enhanced biconical Mach-Zehnder interferometer curvature/temperature sensor is proposed.Quantum-enhanced curvature and temperature measurements were achieved using intensity-correlated twin beams probing under two intensity modulations（equilibrium measurement and non-equilibrium measurement）.The experimental results show that the optimal curvature measurement sensitivity and resolution under equilibrium measurement are 1.2 d B/m^-1 and 0.008 m^-1 in the curvature range of 0-1 m^-1 and the temperature range of 35-60℃;the optimal temperature measurement sensitivity and resolution are 0.01 d B/℃and1°C.The optimum curvature measurement sensitivity and resolution under unbalanced measurement are 50.61 d B/m^-1 and 0.0002 m^-1;the optimum temperature measurement sensitivity and resolution are 0.51 d B/℃and 0.02℃.Under non-equilibrium measurement,since the reference signal does not balance out excess quantum noise,changes in curvature/temperature lead to a sharp increase in noise between the twin beams.Therefore,although the SNR enhancement is not achieved in all curvature and temperature measurement ranges as in the equilibrium measurement,it has a higher measurement sensitivity.