▎ 摘　　要

In this paper, a carboxymethyl cellulose (CMC)/graphene oxide (GO) composite film-coated humidity sensor was proposed based on thin-core fiber Mach-Zehnder interferometer (TCMZI). A segment of thin-core fiber (TCF) was spliced between two segments of single-mode fiber (SMF), and the TCF cladding was first corroded with hydrofluoric acid and then coated with a layer of CMC/GO film via optical driven deposition method. The relative humidity (RH) sensing characteristics of the sensor were experimentally investigated by observing the wavelength shift of resonant dips in the transmission spectrum, which showed that the CMC/GO composite film-coated TCMZI has good repeatability and stability in the measurement of humidity. A maximum average humidity sensitivity of -75.6 pm/%RH was obtained in the RH range of 35%-80%, nearly 2.048 and 3.237 times higher than that of CMC and GO single film coated ones. To the best of our knowledge, this is the first report on using the CMC/GO composite film for humidity measurement, and its excellent performance is expected to be extended to humidity sensitization of more fiber-optic sensors. The proposed sensor has the advantages of simple structure, easy fabrication, low cost, good stability and high performance, which can be applied to the fields of bio-chemical and medicine.