Improved distributed fiber optic sensing system based on single-ended double-pulse input Brillouin scattering

In a new distributed fiber optic sensing system, single-ended double-pulse input is used to strengthen Brillouin backscattered light by increasing the population of acoustic phonons. The first pulse (pump pulse), has a wide pulsewidth (tens or hundreds of us) and is used to generate a nonlinear population of acoustic phonons in the sensing fiber. Whereas the second pulse (probe pulse) has a different central wavelength and a much narrower pulse-width (several ns), and is emitted into the sensing fiber with a controlled time delay to absorb the generated abundant acoustic phonons, so that strong Anti-Stokes light can be generated. In this way, Brillouin backscattered light can be detected easily, leading to higher signal to noise ratio and better spatial resolution (less than 1 m), as well as good temperature and strain resolution, and longer sensing distance.

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