All-fiber humidity sensor based on Michelson interferometer with hyaluronic acid and polyvinyl alcohol composite film

All-fiber humidity sensor based on Michelson interferometer with hyaluronic acid (HA) and polyvinyl alcohol (PVA) composite film is investigated. The interferometer is fabricated by fusing 691 mu m thin-core fiber (TCF) with single mode fiber (SMF) together and melting the other end of the TCF into a circular shape. The outer of the interferometer is coated with HA and PVA composite film. As far as we know, hyaluronic acid is used in relative humidity (RH) measurement for the first time. Through wavelength and intensity demodulation, the proposed sensor's maximum sensitivity is 0.1679 nm/%RH and 0.148 dB/%RH, respectively. Besides, the sensor's cross-sensitivity is low (0.0727%RH/degrees C). Therefore, the proposed sensor with hyaluronic acid has great potential in humidity measurement.