BOTDA system based on four-frequency-division driving

Abstract

The invention discloses a BOTDA system based on four frequency division driving. The system comprises a narrow linewidth laser, a first electro-optic intensity modulator, an optical coupler, a polarization controller, a first erbium-doped fiber amplifier, an optical isolator, a single-mode fiber, a first optical filter, a second electro-optic intensity modulator, a second erbium-doped fiber amplifier, a circulator, a second optical filter, an adjustable radio frequency signal generator, a pulse signal generator and a signal processing unit. The upper path of the optical coupler is connected with the polarization controller, the polarization controller, the first erbium-doped fiber amplifier, the optical isolator and the initial end of the single-mode fiber are connected in sequence, the lower path of the optical coupler is connected with the first optical filter, and the second electro-optic intensity modulator is connected with the second erbium-doped fiber amplifier after being modulated by the pulse signal generator. The second erbium-doped fiber amplifier is connected with a first port of the circulator, and a second port of the circulator is connected with the tail end of the single-mode fiber. According to the invention, the frequency difference of two beams of light is Brillouin frequency shift only by 1 / 4 of an original radio frequency driving signal.

Description

technical field [0001] The invention relates to the technical field of distributed optical fiber sensing, in particular to a BOTDA system based on four-frequency division drive. Background technique [0002] The Brillouin Optical Time-Domain Analysis (BOTDA) based on optical fiber stimulated Brillouin scattering has huge potential applications in structural health monitoring of large civil engineering, communication cables, oil and gas pipelines, etc. The Brillouin optical time-domain analysis technology uses the stimulated Brillouin amplification characteristic to allow two beams of light to propagate in the optical fiber in opposite directions, and one beam has a frequency of v 1 The pulsed pump light of the other beam is the frequency v 2 continuous probe light. When two beams of light meet somewhere in the fiber and the frequency difference between them is equal to the Brillouin frequency shift v B (about 11 GHz), the energy of the optical signal with high frequency w...

AI Technical Summary

Problems solved by technology

[0004] Because the Brillouin frequency shift in the optical fiber is relatively high, about 11GHz, in order to obtain an optical signal with a frequency shift of 11GHz through the electro-optic modulator, according to the frequency shift characteristics of the electro-optic modulator, it needs to be driven by a radio frequency electrical signal of the same 11GHz , it is difficult for a general signal generator to output such a high-frequency signal, and a dedicated RF signal generator is expensive, which increases the system cost sharply

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