Multi-wavelength light source-based Brillouin optical time domain reflectometer

Abstract

The invention discloses a multi-wavelength light source-based Brillouin optical time domain reflectometer which comprises a multi-wavelength laser, a coupler, an electrooptical modulator, an erbium-doped optical fiber amplifier, an optical filter, a circulator, a double-balanced detector and a signal acquiring and processing system, wherein continuous light of the multi-wavelength laser is divided into two paths, wherein one path is modulated into pulse light through the electrooptical modulator and the other path is modulated to obtain continuous light of a local oscillator through an electrooptical modulator sideband. Multi-wavelength detection pulse light is amplified by the erbium-doped optical fiber amplifier, subjected to spontaneous emission noise filtration by the optical filter and is injected into a sensing optical fiber by the circulator. Stokes Brillouin back scattering light in the sensing optical fiber is coherent with local oscillator light through the circulator, is subjected to photovoltaic conversion through the double-balanced detector and then is fed into the signal acquiring and processing system to obtain a Brillouin scattering spectrum on the whole optical fiber and further obtain the temperature and strain distribution on the optical fiber.

Description

Technical field: [0001] The invention relates to a Brillouin optical time domain reflectometer used in the fields of optical fiber sensing and optical cable health monitoring. Background technique: [0002] At present, the Brillouin Optical Time Domain Reflectometer (BOTDR) based on coherent heterodyne detection uses a single-frequency narrow-linewidth light source. The probe light and local oscillator light are only single-frequency optical signals, and the obtained electrical signals are single-frequency detection. The scattering spectrum of the light and the coherent intermediate frequency broadband signal of the single-frequency local oscillator light, changing the center frequency of the local oscillator light, and collecting different frequency bands of the coherent intermediate frequency electrical signal spectrum each time, can obtain the Brillouin scattering spectrum of the optical fiber under test, through Lorentz fit to get the Brillouin frequency shift. By compa...

AI Technical Summary

Problems solved by technology

However, due to the limitation of the nonlinear effect in the optical fiber, the probing optical power incident on the optical fiber under test should be lower than the stimulated Brillouin threshold, and increasing the number of measurements will increase the measurement time, so the improvement of the dynamic range of the system is restricted

The spatial resolution of the measurement is mainly limited by the pulse width of the probe light, shortening the pulse width of the probe light can improve the spatial resolution, but it will reduce the dynamic range of the measurement

By means of pulse encoding, the measurement can have a large dynamic range and high spatial resolution at the same time, but this will greatly increase the signal processing time of the system

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