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Rayleigh scattering based distributed optical fiber sensing utilizes back-scattered light signals from the naturally existed impurities (scatters) in normal optical fibers, eliminating the need for introduction of other markers for achieving sensing purposes. Similar to fiber Bragg grating (FBG) sensing, the primary physical parameters which can be detected by Rayleigh scattering are strain and temperature with resolutions up to 1 με and 0.1°C respectively. Depending on the technique used for the signal processing, various spatial resolution and sensing distance can be achieved. Here we report a Rayleigh scattering based distributed optical fiber sensing system for strain and high temperature measurements. In the sensing system, optical time domain reflectometry is adopted for signal detection. The highest spatial resolution can be achieved is 20 microns with a sensing distance up to 30 meters, and the longest sensing distance can be 2 km. By using normal communications fibers as the sensing elements, continuously distributed strain sensing has been successfully demonstrated along three different planes of a balsa wood beam with different loading conditions. In the temperature sensing experiments, we have measured the temperature distributions in a tube furnace with the maximum temperature above 1000°C.
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