Moisture sensitive composite fiber based on agarose gel surface modification

A new moisture-sensitive composite fiber has been reported. A 12-mu m-diameter single-mode tapered fiber is modified with a thickness of 10-mm-length agarose layer in the evanescent field of the tapered fiber. The application of agarose gel makes the composite fibers with lower temperature crosstalk. The average temperature crosstalk of the sensor is only 0.06 dB/%degrees C in the range of 40-70 degrees C. Moreover, the thinner diameter of the composite fiber is designed to improve the time response, and the light intensity changes controlled in a smaller sensing area significantly increased the sensitivity of the sensor. The relative humidity (RH) sensitivity of the sensor is up to 0.78 dB/%RH in the sensing range. To the best of our knowledge, the performance of the fiber is effectively improved from the previous report. Due to the excellent indicators, the design of the proposed composite fiber makes it useful for highly sensitive RH sensing applications in a wide temperature environment.