Research On Optical Fiber Temperature And Humidity Dual Parameters Sensing Method Based On Sensitive Film

Humidity monitoring is difficult in some special environment due to the requirements of low humidity measurement and small in size,such as warehouse,high-voltage substation and advanced laboratory.In this dissertation,a high-precision temperature and humidity sensing system is designed,which can be applied in the environment that is mentioned above.In this dissertation,a sensor probe that contains optical fiber and sensitive film is fabricated to detect the humidity of narrow and extremely low humidity environment.In order to clarify the moisture sensitive principle of the humidity sensitive film and the mechanism of humidity sensor,the film generating pattern and the specific film fabricating method are analyzed in detail.Since it is difficult to measure humidity in low humidity environment,the humidity sensor which can be used in extremely low humidity environment was studied.The spectral wavelength shift of the humidity sensing probe with photonic crystal structure reaches 21.6 nm in the humidity range of 11-84%RH,and the average humidity sensitivity is 0.3 nm/%RH.The spectral wavelength shift of the humidity sensor with Fabry-Perot interference structure reaches 9.6 nm in the humidity range of 30-70%RH,and the average humidity sensitivity is 0.24 nm/%RH.The two types of humidity sensors mentioned above both can be used in extremely low humidity environment as low as 1%RH.In order to detect the temperature and humidity simultaneously,the temperature and humidity dual parameters sensing and monitoring systems are designed.A temperature and humidity sensing probe based on porous anodic alumina film is designed and fabricated.In the humidity range of 11-84%RH,the sensing probe spectral wavelength shifted 13 nm and the humidity sensitivity is 0.185 nm/%RH.In the temperature range of 30-80?,the temperature sensitivity is 10.4 pm/?.A temperature and humidity sensing probe based on fiber Bragg grating was designed and manufactured.The temperature sensitivity of the probe is 10 pm/? in the temperature range of 20-60?,and the humidity sensitivity of the probe is 0.5 pm/%RH in the humidity range of 30-90% RH.This type of sensor probe can be serially multiplexed to form distributed sensing measurement.In this dissertation,the moisture sensitivity of different types of thin films and their combination with optical fibers are studied.The point-based and quasi-distributed measurements of ambient temperature and humidity are achieved.And the application of fiber optic temperature and humidity sensor in practical environment is explored.Therefore the studies within this dissertation laid a solid foundation for the combination of moisture sensitive films and optical fibers.