A Brillouin optical time-domain analysis system with alternating high and low frequency modulation of pump light

Abstract

The invention relates to a distributed optical fiber sensing system, and discloses a Brillouin optical time-domain analysis system with high and low frequency alternate modulation of pump light, which includes a narrow linewidth laser, and the light emitted by the narrow linewidth laser is divided into Two beams, one beam is used as the detection light to carry out carrier-suppressed double-sided band modulation through the electro-optical modulator; then it is amplified by the erbium-doped fiber amplifier and then enters the sensing fiber, and the other beam is used as the pump light, which is sequentially passed through the single-side band modulator, pulse After the modulator and the pulsed optical amplifier enter the sensing fiber from the other end; the single sideband modulator is used to alternately modulate the pump light at high and low frequencies, making it alternate high frequency sidebands and low frequency sidebands and sweep them; The Brillouin gain spectrum signal and Brillouin loss signal emitted from the other end of the sensing fiber are received by the photodetector after the stray light is filtered out by the optical filter, and then collected by the data acquisition card. The invention increases the signal power twice that of the traditional BOTDA system, and improves the signal-to-noise ratio of the system.

Description

technical field [0001] The invention relates to a distributed optical fiber sensing system, in particular to a BOTDA system for obtaining gain / loss spectrum through high / low frequency alternate modulation of pump light. Background technique [0002] The proposal of distributed optical fiber sensing technology combines signal transmission with sensing media, and successfully realizes data measurement of temperature / strain with a length of hundreds of kilometers, and distributed optical fiber sensing has anti-electromagnetic interference, high sensitivity, and monitoring distance Long and many other advantages, so it can be widely used in various fields of engineering and life, such as in traffic tunnels, bridge construction, and mine environments, it can realize functions such as temperature monitoring, leakage monitoring, and crack inspection. [0003] In distributed optical fiber sensing, because the BOTDA (Brillouin optical time-domain analysis, Brillouin optical time-doma...

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Problems solved by technology

A balanced detection technique to obtain the gain spectrum and the loss spectrum has been proposed in the research (Alejandro Domínguez-López, Alexia López-Gil, Sonia Martín-López, and Miguel González-Herráez. Signal-to-Noise Ratio Improvement in BOTDA Using Balanced Detection [J ]. IEEE PHOTONICS TECHNOLOGY LETTERS, 2014, 26(4): 338-341), but the system device is relatively complex and expensive

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