Fundamentals of Optical Fiber Sensors

CHAPTER 7

EXTRINSIC FIBER FABRY–PEROT INTERFEROMETER SENSOR

Chapter 7 is engaged mainly in the extrinsic fiber Fabry–Perot interferometer (EFFPI) sensor, which is usually composed of a fiber end facet and a mirror. Some intrinsic FFP sensors, in which the Fabry–Perot cavity is built inside the fiber without other components incorporated, are described also. The EFFP sensors are used widely in displacement sensing, pressure sensing, acoustic and ultrasonic sensing, pickup of atomic force microscope (AFM) signals, and other applications. The structures and principles of EFFPI sensors are introduced in Section 7.1. The theoretical analysis on the Gaussian beam Fabry–Perot interferometer is presented in Section 7.2. The basic characteristics and performances of EFFPI sensors are discussed in Section 7.3. The last section introduces applications of EFFPI sensors and discusses the technical issues involved.

7.1 BASIC PRINCIPLES AND STRUCTURES OF EXTRINSIC FIBER F-P SENSORS

The extrinsic fiber FPI sensors were demonstrated earlier in the 1980s [1–3], showing their features and usefulness. The EFFPI sensors have since been studied and developed greatly. The typical sensor structures are introduced as follows.

7.1.1 Structures of EFFP Devices

The EFFP device is typically composed of a fiber with a cleaved or polished end facet and a nonfiber-optical component with a reflective surface, such as a diaphragm fixed on a hollow support, and a cantilever with a planar surface. When a probe optical ...