Research Of The Optical Interferometric Fiber Humidity Sensor Based On The Humidity-Sensitive Materials

The main research content of this paper is optical fiber humidity sensors,resent years,people have paid a lot of attention to the humidity sensitive material.Several new humidity sensitive material have been studied.The experiment results show the existence of humidity sensitive film make a great difference to the humidity sensitivity of the sensor,and the number of humidity sensitive film layers also affect the performance of the sensor's humidity testing.1.We made a study to several kinds of material to their possibility for humidity testing which have not been proved before.The experiment results showed methylcellulose(MC),sodium carboxy methylcellulose(CMC)and acacia can all be used as humidity sensitive film for optical fiber sensor,which provides us new choices of humidity sensitive material when it comes to humidity testing.2.We made a comparison between optical sensors with bitaper structure,these sensors have been coated with humidity sensitive film(polyvinyl alcohol)or not,and the experiment results showed the humidity sensitivity have been improved by almost 10 times after the humidity sensitive film has been coated.This proved the humidity sensitive film plays an important part in the optical fiber humidity sensor.3.We made a comparison among optical sensors with bitaper structure,these sensors have been coated with different layers of humidity sensitive film(sodium carboxy methylcellulose),and the experiment results showed the layers of humidity sensitive film is proportional to the humidity sensitivity of the sensor within limits.When the number of layer is beyond the certain region,the humidity sensitivity of the sensor decrease due to the swelling of the film causing by absorbing moisture.4.We proposed a new Peanut-Taper-Peanut structure,we used this structure to measure refractive index(the refractive index of the film is affected by the air humidity,so the test of humidity can be transferred to the measurement of refractive index).The results showed the structure is sensitive to the RI,so it provides us a new structure to realize humidity sensing.