The Research Of Temperature And Gas Pressure Optical Fiber Sensor Based On Vernier Effect

Due to the advantage of small size,strong anti-electromagnetic interference ability and high flexibility,fiber optic sensors have been widely used in various fields.In practical applications,some fiber optical sensors have the problem of low sensitivity.To solve this problem,the paper optimized the structure of the sensor and used the optical vernier effect to increase the sensitivity of the fiber optic sensor to realize temperature sensing and gas pressure sensing.The main research content of the paper is as follow:A Fabry-Perot fiber sensor with high temperature sensitivity and high spectral contrast was designed and fabricated.The sensor is composed of a hollow core fiber(HCF)filled with polydimethylsiloxane(PDMS)and a semi-ellipsoidal PDMS structure.Due to the focusing effect of the curved end face of the semi-ellipsoidal PDMS structure,the contrast of the spectrum has been significantly improved.Experimentally,the spectral contrast is11.97 d B,which is two times higher than the sensor without semi-ellipsoidal PDMS structure.By utilizing the high thermal expansion coefficient of PDMS and the sensitivity enhancement characteristics of the vernier effect,the temperature sensitivity of the sensor can reach-10.64 nm/℃.An ultra-sensitive temperature sensor based on enhanced vernier effect was designed and fabricated.The sensor consists of a double-groove cavity(DGC)and an open cavity(OC)filled with PDMS.When the temperature changes,the cavity length of DGC is limited by two single-mode fibers(SMF),and the cavity length of OC is not limited.The two sensing cavities are respectively affected by the thermal optic effect(TOE)and thermal expansion effect(TEE).Their interference dip of the spectral shifts to the opposite directions respectively,which realizes the enhanced vernier effect.The experimental results show that the sensor exhibits a high temperature sensitivity of 11.93 nm/℃.Compared to the traditional sensors based on vernier effect using TOE(sensitivity is 3.33nm/℃)or TEE(sensitivity is 8.62 nm/℃)alone,the sensitivity increased by 264.8 % and38.4 % respectively.An ultra-sensitive gas pressure fiber optic sensor based on the vernier effect was designed and fabricated.The sensor consists of a section of SMF and HCF.By using self-filming technology,a thin gelatin film was made inside the air core of HCF,and the thickness of the gelatin film is only 2.12 μm.The thinner the gelatin film,the higher the gas pressure sensitivity of the sensor.When the gas pressure in the external environment changes,the gelatin film will undergo obvious deformation.In this case,the length of the air cavity is sensitive to the changes in the external gas pressure.The vernier effect can be achieved by cascading this structure with another SMF-HCF-SMF structure.The experimental results show that the pressure sensitivity of the sensor is 289.20 nm/MPa,and the sensor shows a strong ability to resist temperature interference.