Method and system for improving performance of distributed optical fiber sensing system based on phi-OTDR

Abstract

The invention discloses a method and a system introducing the Raman mixing amplification technology in a distributed optical fiber sensing system based on a phi-OTDR (phase-sensitive optical time-domain reflectometer) to improve the sensing distance and the sensing performance of the distributed optical fiber sensing system. The Raman mixing amplification technology is introduced based on the conventional phi-OTDR distributed optical fiber sensing technology, and compared with the conventional phi-OTDR distributed optical fiber system based on the first-order Raman amplification technology, the method and the system can obtain higher gain and improve the pumping efficiency under the same pumping power, the distribution of sensing signals along the optical fibers is flatter, the method and the system can be used for greatly improving the spatial resolution, the measuring accuracy and the sensitivity of a monitoring system when being used for long-distance disturbance monitoring, can remarkably improve the sensing performance with very low cost (without additionally arranging a second-order pumping light source), and have certain practicability.

Description

technical field [0001] The invention relates to the field of optical fiber technology, in particular to a method and system for improving the performance of a Ф-OTDR distributed optical fiber sensing system by using Raman hybrid amplification technology. Background technique [0002] Driven by the trend of the Internet of Things, as people have higher and higher security requirements for military bases, power stations, substations, oil storage bases, dangerous goods warehouses, high-end communities and other places, various intelligent security technologies are being closely watched by people. attention, the new security system has very important economic value and social value. The distributed optical fiber sensing system based on Ф-OTDR technology has incomparable advantages compared with ordinary sensing systems. The system uses phase as the measurement parameter and has extremely high sensitivity. The sensing elements and optical cables are buried underground In additio...

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Problems solved by technology

[0004] ①The front end is prone to nonlinear effects, which will not only interfere with the sensing signal, but also when the signal light power is greater than the Brillouin threshold of the fiber, the signal light will produce a stimulated Brillouin effect, causing the signal light power to drop sharply near the incident end , the energy is sharply converted to Brillouin scattered light, so that the transmission distance of signal light cannot be effectively increased

[0005] ②The power distribution in the optical fiber is unbalanced, which makes the sensitivity of the sensing fiber at the front and rear ends very different, and in the same environment, the front-end fiber is more susceptible to environmental noise, especially when the external noise changes greatly, the disturbance signal at the back end will be Being submerged by noise will greatly reduce the remote performance of the system and increase the false alarm rate

However, in the long-distance (>50km) Ф-OTDR sensing system, due to the exponential attenuation of the Raman pump power and Raman gain coefficient along the optical fiber, this method cannot completely eliminate the uneven power distribution, and the sensing distance The longer the length, the more severe the fluctuation, resulting in a large-scale, low signal-to-noise ratio measurement "blind zone" in the distribution of the sensing signal

On the other hand, the efficiency of first-order Raman pumping is low, and in long-distance sensing systems, the requirement for Raman pumping power is high, which greatly increases the system cost

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