ABSTRACT
The general consideration of optical and fiber-optic humidity sensors is the topic of the present chapter.In particular, the instrumentation and possible configuration of optical humidity sensors are considered. It is shown that a multitude of configurations can be adopted in optical and fiber-optic humidity sensors. But, usually these configurations do not differ from the configuration of optical sensors used for the detection of toxic or flammable gases. The most important component of an optical sensor system is the sensor spot (S), which contains an analyte-specific indicator (humidity-sensitive material). A detailed analysis of the various types of optical and fiber-optic humidity sensors includes a description of optical fibers, which are also called the light guides, and the consideration of approaches to the classification of fiber-optic sensor configurations. It is shown that there are many different configurations of fiber-optic sensors (FOS), but the most common are end-of-fiber configuration, side-of-fiber configuration, hybrid intrinsic sensors, and porous or interrupted fiber configuration. The difference of these configurations is in a different location of a humidity indicator. Features of using planar waveguide-based platforms for humidity sensor design are also discussed in this chapter.
