Raman sensing temperature measurement system in double-end injection annular structure, and Raman sensing temperature measurement method

Abstract

The invention discloses a Raman sensing temperature measurement system in a double-end injection annular structure, and a Raman sensing temperature measurement method. The system comprises a light source, a wavelength division multiplexer, a photovoltaic conversion module, a sensing optical fiber, a signal collection and processing module, and a 1x2 optical switch. The head and tail ends of the sensing optical fiber are respectively connected with the 1x2 optical switch, and the sensing optical fiber is arranged in an annular structure. The 1x2 optical switch is connected to a head end optical circuit or a tail end optical circuit of the sensing optical fiber in a timing manner. The method comprises the steps: enabling the light of the light source to be injected to the head and tail ends of the sensing optical fiber in a timing manner, and correspondingly, obtaining anti-Stokes optical signals from the head and tail ends; enabling the obtained head-end and tail-end signals to be multiplied with each other, and then carrying out geometric averaging, thereby obtaining a result that optical fiber loss in an optical fiber temperature curve is not related with the position, and eliminating related loss of static wavelength and local loss. The method also achieves the normalization and self-collection of signals at an optical fiber ring through temperature control, thereby eliminating impact caused by photovoltaic conversion gain change and dynamic change of optical loss, and improving the temperature measurement precision.

Description

technical field [0001] The invention relates to a temperature measurement system and method, in particular to a Raman sensing temperature measurement system and method with double-end injection ring structure. Background technique [0002] Distributed Raman fiber optic sensors have many advantages such as long-distance distributed measurement, anti-electromagnetic interference, small size and light weight, etc., in urban gas pipelines, power transmission / communication cables, reservoir dams, bridges, tunnels, highways, etc., which require real-time temperature It has a wide range of applications in the field of monitoring. The traditional Raman optical fiber sensing scheme uses a single-ended injection method to simultaneously detect Stokes light and anti-Stokes signals in spontaneous Raman scattering, and use the ratio of the two for temperature demodulation. [0003] Among them, the anti-Stokes optical power is: [0004] P AS ...

AI Technical Summary

Problems solved by technology

However, due to the wavelength-dependent loss of Stokes light and anti-Stokes light in the optical fiber, the temperature measurement curve obtained by the sensing system cannot completely reflect the temperature information along the optical fiber.

In practical applications, environmental changes will also change the wavelength-dependent loss and local loss of the sensing fiber at any time, resulting in slow and imperceptible measurement errors in the temperature measurement curve demodulated by the sensing system. Therefore, the Raman scattered optical power is not only related to Sensing fiber temperature is related. In practical applications, due to the influence of incident light wavelength drift, transmission loss, local loss (fiber fusion, bending, etc.), and fiber aging in harsh environments, the α in formula (3) AS (x)-α S (x) changes with time, and this change is reflected in the measured value of Raman scattering power, which will increase the temperature measurement error

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