A novel optical fiber humidity sensor based on Mach-Zehnder interference and AIEgens

The wide application of aggregation-induced emission (AIE) materials in numerous fields has caused a surge in attention. This paper presents a novel optical fiber humidity sensor based on Mach-Zehnder interference structure with poly methyl methacrylate/(5-OHC9H6N)2B18H20 (record as: PMMA/S1) composite film. The RH response performance of the sensor was investigated and the water molecules response mechanism of the PMMA/S1 composite film was discussed. The sensitivity of 0.153 nm/% RH with a linear correlation coefficient of R2 = 0.99265 can be obtained at the range of 20 %-95 % RH. Compared with the fiber optic sensor using PMMA thin film alone, the humidity sensitivity of this sensor has increased by nearly 19 times. In addition, the temperature effect of the sensor in an environment of 20 degrees C-40 degrees C can be ignored, and it can meet the humidity detection requirements at room temperature. The sensor has the advantages of wide humidity response range, fast response time, resistance to temperature interference and high stability. Our work provides a promising platform for remote and online monitoring humidity.