Optical Fiber Humidity Sensors Using Nanostructured Coatings of SiO$_{2}$ Nanoparticles

In this paper, a new optical fiber humidity sensor based on superhydrophilic coating is proposed. The electrostatic self-assembly technique has been used to create a nanometric scale surface on the tip of a standard single-mode pigtail. The fabricated sensor has demonstrated a good linearity in the range from 40% to 98% of relative humidity (RH). A variation of 10 dB in reflected optical power is achieved with a response time of only 150 ms. Among other applications, this sensor is intended to be used for monitoring the human breathing, so high dynamic performances are required, specially in the higher RH ranges.