Fundamentals of Optical Fiber Sensors

CHAPTER 6

FIBER SENSORS WITH SPECIAL APPLICATIONS

Among the various fiber sensors, the fiber optic gyroscope (FOG), fiber optic hydrophone, fiber Faraday sensor, and fiber sensors based on surface plasmon are worthy of special attention, not only for their special applications but also for their technical features. Since some monographs and a great number of papers have been published, this chapter gives just a brief introduction.

6.1 FIBER OPTIC GYROSCOPE

The FOG, as an excellent rotation sensor, is regarded as one of the most successful and most precise devices of fiber sensor technology. It is widely used in many important application areas, such as compasses and navigational devices for various vehicles, including automobiles, boats, airplanes, missiles, and submarines, well and tunnel logging, and latitude position sensors [1–5]. Compared with the mechanical gyros, the FOG shows high sensitivities, low cost and good robustness with no moving parts. The physical principle, theory, characteristics and related mechanisms, and fabrication techniques of the FOG are expounded in hundreds of references [6–8] and textbooks [2,9] systematically in detail. Roughly, three types of FOG are developed: interferometric FOG (IFOG), resonant FOG (RFOG), and Brillouin FOG (BFOG). This section gives a brief introduction to the FOGs with emphasis on IFOG.

6.1.1 Interferometric FOG

The basic concept of the Sagnac effect is introduced in Section 3.3.1. For a practical fiber optic gyro, it is necessary ...