ABSTRACT
The Fabry–Perot interferometer (FPI), sometimes called the Fabry–Perot etalon, consists of two mirrors of reflectance R 1 and R 2 separated by a cavity 36of length L, as in Figure 2.1. Since its invention in the late 19th century [1], the bulk-optics version of the FPI has been widely used for high-resolution spectroscopy. In the early 1980s, the first results on fiber optic versions of the FPI were reported. In the late 1980s, fiber Fabry–Perot interferometers began to be applied to the sensing of temperature, strain, and ultrasonic pressure in composite materials. This early work laid the foundation for extensive research and development as well as commercialization, which followed during the 1990s.
