ABSTRACT
The history of Fabry-Perot (FP) sensors began at the turn of the nineteenth century with derivatives of the parallel-plate interferometer. Some of the Fiber-Optic Fabry-Perot Interferometric (FFPI) sensors have been successfully commercialized and widely used for health monitoring of composite materials, large civil engineering structures, space aircrafts and airplanes which would lead to the realization of the so-called smart materials and structures. By measuring the shift of the phase or wavelength spectrum, the sensing parameter applied on the FFPI sensor can be quantitatively obtained. The free spectral range (FSR), the spacing between adjacent interference peaks in a spectrum, is also influenced by the Optical Path Difference (OPD) variation. The interferometric signal from the FFPI is amplified by the Er-doped fiber (EDF) and then detected by an optical spectrum analyzer (OSA). The book also focuses on quantity of the interference beams. The principle of two-beam interference is the coherent addition of two reflectors with low reflectance.
