ABSTRACT
Detailed consideration of the features of design and fabrication of optical and fiber-optic humidity sensors is presented in this chapter. In particular, this chapter contains both general comments to optical sensor design, and analysis of the reasons of uncontrolled intensity modulation in optical sensors. Descriptions of light sources, optical materials, reflectors, fiber-optic couplers and detectors used in optical and fiber-optic sensors (FOS), and advantages of charge-coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) matrixes for the application are also presented in this chapter. Great attention is being paid to the selection of fibers, aimed for optical sensors, and features of these fibers’ preparation. Fabrication of fiber grating using two-beam holographic technique, phase-mask technique, and point-by-point technique are also discussed. Features of microfiber gratings and long-period grating are considered. Descriptions of UV long-period fiber gratings, residual thermal stress long period fiber gratings, mechanical stress-induced long-period fiber gratings, and etching induced long-period fiber gratings are given. Optic fiber sensor fabrication by laser-micromachining is also discussed. In optical humidity sensors, the humidity recognition element is usually immobilized on an inert and stable solid matrix. Therefore, an appreciable part of this chapter is devoted to the consideration of various techniques of fiber’s immobilization on the basis of chemical and physical methods of deposition. The analysis carried out has also shown that the development of appropriate packaging for fiber sensors, without a doubt is an important one on the way to promote fiber-optic humidity sensors on the market, because sensors in the appearance that is used in most of the studies cannot emerge on the market. Therefore, the packaging FOS is the next big task after a sensor design.
