Principles and applications of fiber-optic Fabry-Perot sensors

Summary form only given. A versatile technology based upon the fiber Fabry-Perot interferometer (FFPI) is proving its merit in industrial sensing applications. The FFPI consists of two internal mirrors separated by a length L of single-mode optical fiber. A sensor head is designed such that the measurand of interest (e.g., pressure, strain, acceleration, magnetic field, temperature) affects the optical length of the interferometer. A signal conditioning unit that performs multiplexing and signal processing functions is capable of monitoring many sensors with a single distributed feedback laser and digital signal processor. An alternative monitoring scheme using a white light interferometry with a low coherence light source has also been demonstrated. Applications include monitoring gas pressure in engines, liquid pressure in pumps, strain in civil structures, defects in bearings, and vibration in rotating machinery. In extensive field tests, the engine pressure sensor has shown an unprecedented combination of accuracy and durability at high temperatures. Other advantages over competing technologies include high sensitivity, immunity from electromagnetic interference, small size, the ability to locate sensors far from monitoring equipment, and the potential for least-cost implementation through multiplexing and networking.