Fabrication And Strain Sensing Characteristic Of The Fiber Temperature-compensated Interference Structure

In recent years,the sensor based on Fabry-Perot interferometric has attracted wide attention in the field of strain sensing because of its advantages of high sensitivity,small size and anti-electromagnetic interference.However,the sensitivity of the sensor based on Fabry-Perot interferometric is generally low.And when the strain sensor is applied to the actual measurement,the temperature variation is ordinarily at a large range.Due to the response of the optical fiber sensing structure to the temperature,the measurement precision of the sensing structure is reduced.Therefore,in the practical application,especially in the precise measurement of the micro strain field,it is essential that a kind of sensor with excellent sensing performance is designed and prepared.In this paper,a temperature compensated in-fiber ultra-long suspension taper interference sensing structure is proposed.The relationship between the strain sensitivity of the sensing structure and the length of the hollow core fiber and the length of the fiber cone is derived theoretically.By increasing the length of the hollow fiber and the length of the taper fiber,the strain sensitivity of the sensing structure can be increased.The thermal expansion of the hollow fiber and the taper fiber is simulated,respectively.The matching equation to achieve zero temperature crosstalk of the sensing structure is obtained,which is related to the length and shape of the hollow fiber and the taper fiber.The inner diameter of the hollow core fiber is set as 50 ?m,the outer diameter is set as 125 ?m,and the diameter of the optical fiber cone is set as 40 ?m.The length of the hollow fiber is set as 1000 ?m.When the matching equation is satisfied,the length of the taper fiber is calculated to be 993.8 ?m.To control the length of hollow fiber and taper fiber,a simple optical fiber taper platform is set up.The in-fiber ultra-long suspended taper interference structure with high strain sensitivity is fabricated,the length of hollow fiber and taper fiber can be reach as high as 3096 ?m and 3092 ?m,respectively.The strain sensing experiment is carried out.The experimental results show that the strain sensitivity of in-fiber ultra-long suspended taper interference structure is as high as 1 nm/??.The precise displacement platform of the fiber optic cone is built,and its accuracy can reach 0.02?m to achieve precise control of the insertion length of the taper fiber.The experiment results of the strain and temperature response of the optimized structure show that the strain sensitivity is as high as 214.35 pm/°C and the temperature crosstalk is only 0.05 pm/°C.The "ladder-mode" and repeatability experiments show that the proposed sensing structure is actually with the ult ra-low detection limit of 0.047 ??.The in-fiber ultra-long suspension taper interference sensing structure is attached to the thin plate to measure the sound wave.A strain sensing structure attached to the thin plate is used to measure the strain generated by the sound pressure acting on the thin plate to realize the sensing of the sound wave.The experimental results show that the structure has a good response to some sound waves and can change the acoustic response characteristics of the sensing structu re by changing the diameter of the attached plate.