Stimulated Brillouin effect-based differential temperature sensor

Abstract

The present invention provides a stimulated Brillouin effect-based differential temperature sensor. The continuous light generated by a light generating unit is subjected to a first modulation amplifier unit to obtain a signal containing the Stokes light and the anti-Stokes light. After that, the signal is subjected to a second modulation amplifier unit to generate a phase modulated signal. The modulated signal is subjected to a filter, so that the Stokes light and the anti-Stokes light are filtered out. The Stokes light passes through a delay optical fiber to be integrated with the anti-Stokes light as one path of optical signals through a 3 dB coupler. The path of optical signals is subjected to a polarizer, so that the polarized light can be extracted. The extracted polarized light is subjected to a third modulation amplifier unit to obtain the pumped pulse light. The pumped pulse light is injected into the initial end of a sensing optical fiber. The detection light of the other path is infiltrated through the tail end of the sensing optical fiber via a scrambler instrument and an isolator. Inside the optical fiber, the detection light forms a circulator together with the pumped pulse light under the stimulated Brillouin effect, and then is converted into an electric signal through a photoelectric detector. According to the technical scheme of the invention, the temperature resolution and the sensing distance are higher on the premise that the high spatial resolution is realized.

Description

technical field [0001] The invention relates to the technical field of temperature or stress sensors, in particular to a differential temperature sensor based on the stimulated Brillouin effect. Background technique [0002] The distributed optical fiber temperature and stress sensing system based on the stimulated Brillouin effect uses light waves as sensing signals and optical fibers as the transmission medium to sense and detect external measured temperature or stress signals. It not only has the advantages of general optical fiber sensors, Moreover, the continuous distribution information of temperature or stress with time and space can be obtained at the same time. Because the optical fiber itself has no electricity, small size, light weight, easy bending, anti-electromagnetic interference, and good anti-radiation performance, it is especially suitable for use in harsh environments such as flammable, explosive, and strong electromagnetic interference, making it suitable...

AI Technical Summary

Problems solved by technology

[0006] In the traditional BOTDA system, due to the limitation of phonon relaxation, the pulse width cannot be smaller than the phonon relaxation time, otherwise the phonon will not reach a steady state, resulting in a decrease in signal-to-noise ratio, broadening of the Brillouin gain spectrum, and frequency The resolution is reduced, which greatly limits the further improvement of the spatial resolution

The pre-pumping method solves the limitation of phonon relaxation to a certain extent by pre-pumping a pulse in advance, but the sensing distance is limited, and the long-distance sensing will cause the Brillouin gain of the pulse base to be greater than the pulse itself. gain

In the dark pulse method, almost no phonons are excited between the pump pulse and the probe light in the dark pulse, resulting in a loss of Brillouin gain due to the lack of phonons in a period of time after the dark pulse, that is, " secondaryecho", which in turn will increase the error in calculating the Brillouin frequency shift

Although the signal-to-noise ratio of the pulse method is twice that of the dark pulse, it still suffers from the same defects as the dark pulse, which affects the practicability of the system.

As for the differential pulse pair method, high spatial resolution and frequency resolution can indeed be obtained, as well as long-distance sensing, but due to the need to measure twice, it takes a long time, and its response time is twice that of traditional BOTDA

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