基于大偏置熔接的全光纤法布里珀罗湿度传感器

利用大偏置熔接方法在两段单模光纤(SMF)中间熔接一小段单模光纤作为支撑梁制作了一种开腔式法布里珀罗（F-P）干涉传感器。提出在干涉腔内填充一种湿度敏感型物质聚丙烯酰胺（PAM）从而形成一种高灵敏度的微型湿度计。当PAM通过吸收空气中的水蒸气而引起自身折射率发生改变，从而导致F-P干涉谱发生漂移，通过检测干涉谱的漂移量可以实现对环境相对湿度的测量。实验结果表明，这种湿度传感器在38%~78%的相对湿度范围内，在PAM折射率变化范围内其干涉谱漂移了约4 nm，漂移量与相对湿度的灵敏度约为0.1 nm/%；而在88%~98%的相对湿度范围内可实现高灵敏度的湿度测量，其干涉谱漂移了约59 nm，漂移量与相对湿度的灵敏度为5.868 nm/%。

A Humidity Sensor Based on All-Fiber Fabry-Perot Interferometer Formed by Large Offset Splicing

A novel humidity sensor based on open cavity Fabry-Perot (F-P) interferometer which is formed by fusion splicing a short section of single-mode fiber (SMF) between two sections of single-mode fibers with a large offset splicing method is proposed. The proposed structure can act as a nano-composite hygrometer with high sensitivity by filling the cavity with a humidity sensitive material polyacrylamide (PAM). It is realized that the humidity can be measured by monitoring the interference spectrum shift of the sensor when the refractive index of PAM changes due to absorbing water vapor in the air substantially. The experimental results show that the interference spectrum shift is about 4 nm when the surrounding humidity varies in the range of 38%~78% and the sensitivity of interference spectrum shift versus the relative humidity is about 0.1 nm/%; the interference spectrum shift can reach up to about 59 nm when the surrounding humidity varies in the range of 88%~98% and the sensitivity of interference spectrum shift versus the relative humidity is 5.868 nm/%.