Application of Rayleigh Scattering Light in Fiber Optic as Sensing System

摘要

The general ideas were created several years ago [l÷3] and discussed by us in invited paper on 16th International School on Condensed Matter Physics, August 29th - September 3rd 2010, Varna, Bulgaria. Fiber-optic sensors are devices designed on the basis of characteristic changes in light wave spreading in optical fiber. The most commonly used changes arc in intensity, phase, frequency, polarization, time distribution and mode state. Fiber-optic systems integrating fiber optics are set up in combination with opto-electronic components, such as: high coherent laser diodes, power LEDs, various kind of photodiodes, optical modulators, electronic modules containing highly specialized computer blocks. Systems arc managed by special software designed for specific purposes, in which conducts an analysis of the light signals carrying information about the relevant perturbation. One way to create an optical sensing system is through analysis of Rayleigh scattering of light in fiber optic, in which light from the coherent laser radiation is spreading. This phenomenon is related to the interference of waves scattered back from different parts of the fiber itself and can carry information about the initiation of the perturbation of external influences on the fiber. Such interference could be mechanical stresses, seismic or sound waves and locally increase of pressure in adjacent areas of the optical fiber.