Fast detection of humidity sensor with a weakly coupled fiber coated with carbomer

Abstract

Humidity, as one of the basic environmental physical quantities, is essential in medical monitoring, food production and pharmaceutical industries.Fast and highly sensitive humidity sensing technology has become an urgent need in areas such as medical monitoring. We proposed and realized a novel coupled fiber-optic humidity sensor based on double tapered fiber twisted weakly coupled structure coated with carbomer film. The sensor adopts 2 × 2 coupler structure with waist diameter of 10 μm. The Carbomer film is coated in the weakly coupled area to improve the sensitivity of the sensor, and the thickness of this coating is about 79.2 nm. The sensor provides linear sensing over a relative humidity range of 40%–65% RH, with a dynamic response time of 208 ms and a recovery time of 464 ms. The sensitivity of the sensor is up to −0.28 dB/%RH and the linearity of the sensor is as high as 99.89%. Moreover, the sensor has good stability, reversibility, and low temperature crosstalk. Based on these characteristics, it can be expected that the sensor will bring a great breakthrough in applications where sensitive monitoring of humidity is required.