Optical fibers can be used as sensors to measure, , and other quantities by modifying a fiber so that the quantity to be measured modulates the,,, or transit time of light in the fiber. Sensors that vary the intensity of light are the simplest, since only a simple source and detector are required. A particularly useful feature of intrinsic fiber-optic sensors is that they can, if required, provide distributed sensing over very large distances.
[pdf] Rayleigh scattering -based distributed acoustic sensing (DAS) systems use fiber optic cables to provide distributed strain sensing. In DAS, the optical fiber cable becomes the sensing element and measurements are made, and in part processed, using an attached optoelectronic device. In order to further promote the acoustic detection potential of the Fabry–Pérot etalon (FPE)-based FOAS, it is of great significance to study the acoustic. We provide two high performing, highly reliable long-range intrusion detection sensors.
[pdf] 
