Brillouin optical fiber sensing system and method

Abstract

The invention discloses a Brillouin optical fiber sensing system and method. A light difference parameter amplifying technology, a three-frequency probe laser technology and a coherent detection technology are adopted at the same time. By means of the light difference parameter amplifying technology, the spatial resolution of the Brillouin optical fiber sensing system can be improved to a sub-meter grade, the coherent detection technology can improve the signal to noise ratio and measurement precision of the system and increase the sensing distance, and the three-frequency probe laser technology compensates power loss of two beams of pump pulse light, can greatly reduce the non-local effect brought by power mismatch of the two beams of the pump pulse light and loss in long-distance sensing, and further improves measurement precision, so that it is guaranteed that the Brillouin optical fiber sensing system has a relatively long sensing distance, and the sub-meter spatial resolution and high measurement precision can be achieved.

Description

Technical field [0001] The invention relates to the technical field of optical fiber sensing, in particular to a Brillouin optical fiber sensing system and method. Background technique [0002] When the frequency difference of the two light waves propagating in opposite directions in the fiber is within the inherent Brillouin gain range of the fiber, the two light beams undergo stimulated Brillouin effect through the acoustic wave field, and energy transfer occurs between the two beams. When the frequency difference of the light is equal to the inherent Brillouin frequency shift (BFS) of the fiber, the energy transfer amount is the largest. Based on this, the Brillouin frequency shift distribution along the length of the fiber can be measured. Brillouin Optical Time Domain Analysis (BOTDA) technology It is based on the above principle and the linear relationship between Brillouin frequency shift (BFS) and temperature and strain to realize distributed temperature and strain sensin...

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Problems solved by technology

[0003] Limited by the phonon lifetime of 10ns, the best spatial resolution of the traditional direct detection BOTDA system is 1m. In addition, due to the existence of fiber nonlinear effects, the sensing length of traditional BOTDA is limited by the maximum optical power allowed by the pump pulse light. And due to the limitation of the non-local effect caused by the power loss of the pump pulse, these shortcomings greatly limit the application of the BOTDA system

In order to improve the spatial resolution of the system, people proposed the method of differential pulse pair, but this method needs twice the measurement time. For this reason, people also proposed the scheme of optical path difference, that is, injecting pulses with different pulse widths in the optical domain at the same time. The Stokes pump light and the anti-Stokes pump light are used to subtract the Brillouin gain and Brillouin loss brought about by their interaction with the probe light at the same time, and finally measure the optical power of the probe light over time However, because the Brillouin gain signal after the optical path difference is relatively weak, the sensing distance is not long and the measurement error is relatively large. In addition, the non-local effect caused by the mismatch and loss of the optical power of the two pump pulses is also will cause systematic errors in the measurement

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