Multi-point optical fiber hydrogen detection system based on light polarization modulation

A hydrogen sensing system including 8 sensors based on light polarization modulation is developed and demonstrated for simultaneous multi-point hydrogen sensing with high sensitivity. Each sensor is composed of a polarizer, a polarization control, and a short segment of polarization maintaining fiber (PMF) coated with Pt-loaded WO3. Due to the exothermic reaction between hydrogen and WO3 with the help of catalyst Pt, the local temperature of PMF increases and the reflective spectrum of the sensor shift accordingly. The self-developed control system software achieves the sequential scanning and recording of the reflection spectra of each sensor by programable controlling a light switch, and then gives the measured hydrogen concentration of each channel in real-time according to the spectrum shift by using an automatic dip finding algorithm with Gaussian fitting. The experimental results show that the proposed type of sensor has ultra-high hydrogen sensitivity, with a maximum value of-20.22 nm/% (vol %); packaging with foam substrate helps to reduce the response time of the device; the hydrogen sensor is almost unaffected by environmental relative humidity. Moreover, the hydrogen sensing system is experimentally proved having good stability and repeatability.