An ultra-long adiabatic tapered single-mode fiber is proposed to enhance the received scattered light in the fiber without additional loss. By controlling the radius and refractive index distribution on the length of the fiber, the backscattering coefficient of the scattered light is increased, and the signal-to-noise ratio of the scattered light is improved while the long distance sensing length is maintained. By analyzing and optimizing the length, radius and refractive index distribution of tapered optical fibers, scattering enhancement of 7dB can be achieved at 45km. Ultra-long adiabatic tapered single-mode fiber can realize Rayleigh backscattered light enhancement of equal signal-to-noise ratio at each position, which can be used to improve the signal-to-noise ratio and measurement range of fiber sensing system based on Rayleigh backscattered, and further promote the application of fiber sensing technology for ultra-long distance sensing.
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