Optical Fiber Humidity Sensor Based On Fabry-Perot Interferometer With Vernier Effect

As a common physical quantity,humidity has a profound impact on our production and life.There are many traditional humidity measurement methods,most of which are based on current transfer signals.In this case,the disadvantages of large size,low sensitivity,and weak anti-electromagnetic interference ability are very prominent,and the humidity sensor based on the optical principle can avoid these disadvantages.In recent years,optical fiber sensors with Fabry-Perot structure have been used in humidity measurement due to their compact structure,neat spectrum,and easy coating.troubled.In this thesis,we investigated a Fabry-Perot interferometer-based fiber-optic humidity sensor coated with polyvinyl alcohol(PVA),introduce coating humidity-sensitive films and vernier effects to improve sensor sensitivity,and design three methods based on Fabry-Perot interferometers.The sensor of Luo principle discusses their principle and various sensing parameters.The main research contents are as follows:1.A Fabry-Perot fiber humidity sensor based on open cavity is studied.Aiming at this structure,we show the sensing principle and design and fabrication scheme of the sensor and describe the measurement device and method of the sensor’s humidity,response time,stability,and temperature.Then,the sensitivity performance of this interferometer under the same cavity length,different aperture diameters and film thicknesses was investigated.Through experiments,it is obtained that the sensor sensitivity of this structure can reach 0.722 nm/%RH when the aperture diameter is40 μm and the film thickness is 10 μm.And the sensor response time is about 10 s,good stability,low temperature interference.2.A parallel optical fiber humidity sensor based on vernier effect is studied.The principle of the parallel vernier effect is expounded;the design and fabrication scheme of the sensor is shown;the humidity sensor of this type of structure is then experimentally measured to have a sensitivity of 1.7 nm/%RH under high humidity,and the experimental data show that the response time of this type of sensor is About12 s,good stability,temperature cross-sensitivity of 0.174 %RH/℃.3.A series optical fiber humidity sensor based on vernier effect is studied.The principle of the series vernier effect is expounded;the design and manufacture scheme of the sensor is explained;through experiments,the sensitivity of the sensor is measured to be 1.522 nm/%RH,the response time of the sensor is about 10 s,the stability is good,and the temperature cross-sensitivity is 1.02 %RH/℃ And it is proposed to deal with the larger temperature disturbance by the method of sensitivity coefficient matrix.