Compound Clearance Humidity Sensor Based on a Polyvinyl Alcohol (PVA) Coated Mach-Zehnder Interferometer (MZI) Using a Broadband Laser as the Light Source
P. Gao, Y. Liu, X-L. Zheng and Z-M. Wang
A single-mode fibre (SMF)-compound clearance – photonic crystal fibre (PCF)-SMF humidity sensor is proposed. This sensor uses the composite gap composed of air cavity and fibre matching liquid as the beam splitter, and uses a broadband laser as the light source. This structure can effectively beam the core mode conducted in the core of single-mode fibre (SMF), so that it can evenly diffuse into PCF and has better repeatability than the fusion method. In the PCF transmission process of this structure, a relatively stable Mach-Zehnder interferometer (MZI) is formed, which realizes the sensing of relative humidity, and has a sensitivity of 330 pm/%RH in the range of 30 to 80 %RH. The sensor has the characteristics of high sensitivity, simple structure and low production cost, and has a good prospect in various application fields.
Keywords: Broadband laser, polyvinyl alcohol (PVA), Mach-Zehnder interferometer (MZI), photonic crystal fibre (PCF), single-mode fibre (SMF), humidity sensor, compound clearance, optical fibre mechanical connection