摘要
A fiber-optic humidity sensor has been fabricated by coating a moisture sensitive polymer film to the fiber Bragg grating （FBG）. The Bragg wavelength of the polyimide-coated FBG changes while it is exposed to different humidity conditions due to the volume expansion of the polyimide coating. The characteristics of sensors, including sensitivity, temporal response, and hysteresis, were improved by controlling the coating thickness and the degree of imidization during the thermal curing process of the polyimide. In the relative humidity （RH） condition ranging from 11.3%RH to 97.3%RH, the sensitivity of the sensor was about 13.5pm/%RH with measurement uncertainty of ±1.5%RH.
A fiber-optic humidity sensor has been fabricated by coating a moisture sensitive polymer film to the fiber Bragg grating （FBG）. The Bragg wavelength of the polyimide-coated FBG changes while it is exposed to different humidity conditions due to the volume expansion of the polyimide coating. The characteristics of sensors, including sensitivity, temporal response, and hysteresis, were improved by controlling the coating thickness and the degree of imidization during the thermal curing process of the polyimide. In the relative humidity （RH） condition ranging from 11.3%RH to 97.3%RH, the sensitivity of the sensor was about 13.5pm/%RH with measurement uncertainty of ±1.5%RH.
基金
This work is supported by National Natural Science Foundation of China （61107073, 61107072 and 61290312）, Fundamental Research Funds for the Central Universities （ZYGX2011J002）, Research Fund for the Doctoral Program of Higher Education of China （20110185120020）, Program for Changjiang Scholars and Innovative Research Team in University （PCSIRT, IRT1218）, and the 111 Project （B 14039）.
