Method for measuring spontaneous Brillouin scattering based on super structured fiber grating filter

Abstract

The invention discloses a method for measuring spontaneous Brillouin scattering based on a super structured fiber grating filter, which inhibits coherent Rayleigh noise by the method which uses the distribution of a narrow line width to feedback a fiber optic laser and a wide band laser to obtain strength ratio of a Brillouin signal and a Rayleigh signal; the method comprises the following steps:firstly, the generated narrow line width pulsed light is fed back to a detected fiber after polarization control according to the length of the fiber; a back reflection signal enters a filter bank through a circulator port (4) and respectively regulates the adjustable super structured fiber grating filter, filters a Rayleigh signal to the largest extent, extracts a spontaneous Brillouin scatteringsignal, feeds the spontaneous Brillouin scattering signal into a highly sensitive photoelectricity conversion module and a signal processing module, and detects the intensity of the spontaneous Brillouin signal through data accumulation and wavelet-de-noising treatment; secondly, the pulsed light generated by the wide band laser passes through a rear-end module the same as in the first step to measure the Rayleigh scattering signal; and finally, the data measured at two times are processed on a computer to display the fiber temperature and stress, which solves the problem of measuring methodof the fiber spontaneous Brillouin signal.

Description

technical field [0001] The invention relates to a method for measuring optical fiber spontaneous Brillouin scattering signals based on a superstructure optical fiber grating filter (also known as a double-peak filter), which is mainly used for measuring optical fiber spontaneous Brillouin scattering signals and belongs to the field of sensing technology. Background technique [0002] The design and fabrication of filter is the key to the measurement of optical fiber self-Brillouin scattering signal. Due to the characteristics of the Brillouin signal (the scattering spectrum in the fiber is as figure 1 As shown), it is difficult to obtain matching filters on the market. At present, interferometers are mainly used to realize the existing schemes. However, the commonly used fiber-optic M-Z interferometers have problems such as poor stability and difficult adjustment. They can only be used in some experiments. It is used in a room environment, and the F-P interferometer is not ...

AI Technical Summary

Problems solved by technology

Fiber Bragg Gratings are widely used to make all-optical filters required for various sensing and communication, but traditional Fiber Bragg Grating filters cannot meet the needs of BOTDR, because Rayleigh and Brillouin scattering wavelengths are close (11G), since the release The Liouin effect will produce two Stokes and anti-Stokes peaks with an interval of about 0.17nm on both sides of the Rayleigh peak, which are nearly 30dB lower than Rayleigh

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