A Raman sensing temperature measurement system and method for double-ended injection ring structure

Abstract

The invention discloses a Raman sensing and temperature measuring system and method for dual-end injection into a ring structure. The system includes a light source, a wavelength division multiplexer, a photoelectric conversion module, a sensing optical fiber, a signal acquisition and processing module, and a 1x2 optical switch. The first and last ends of the sensing fiber are respectively connected to the 1x2 optical switch correspondingly and the sensor fiber is arranged in a ring structure, and the 1x2 optical switch switches and connects the optical path at the head end or the tail end of the sensing fiber in time division. The light source is injected into the head end and tail end of the sensing fiber in time division, and the anti-Stokes optical signal is obtained from the head end and tail end accordingly, and the obtained head end signal and tail end signal are multiplied and geometrically averaged to obtain the optical fiber The fiber loss in the temperature curve has nothing to do with the position, thereby eliminating the static wavelength-dependent loss and local loss. This method also uses the signal at the temperature-controlled fiber ring for normalization and self-correction to eliminate the dynamics of the photoelectric conversion gain change and fiber loss. The impact of changes can improve the temperature measurement accuracy.

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] [0005] The Stokes optical power is: [0006]...

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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