A Differential Temperature Sensor Based on Stimulated Brillouin Effect

Abstract

The invention provides a differential temperature sensor based on the stimulated Brillouin effect. The continuous light generated by the light generation unit passes through the first modulation and amplification unit to obtain a signal including Stokes light and anti-Stokes light, and then The phase modulation signal is generated by the second modulation and amplification unit, and the modulation signal filters out the Stokes light and the anti-Stokes light through the filter, and the Stokes light passes through the delay fiber and the anti-Stokes light After the 3dB coupler synthesizes one optical signal, it passes through the polarizer to extract the polarized light. The extracted polarized light passes through the third modulation and amplification unit to obtain the pump pulse light, and then injects it into the beginning of the sensing fiber; the detection light on the other side is disturbed. The polarizer passes through an isolator and enters from the end of the sensing fiber. After being stimulated by the Brillouin action with the pump pulse light in the fiber, it passes through the circulator and is converted into an electrical signal by the photodetector. The invention can realize higher temperature resolution and longer sensing distance under the premise of high spatial resolution.

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, " secondary echo", which 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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