Distribution-type optical-fiber Raman temperature sensor adopting circulating pulse coding and decoding and Rayleigh demodulation

Abstract

The invention discloses a distribution-type optical-fiber Raman temperature sensor adopting circulating pulse coding and decoding and Rayleigh demodulation, and the sensor comprises a pulse optical-fiber laser, an acoustic-optic demodulator, an integrated optical-fiber wavelength division multiplexer with four ports, two photoelectric receiving amplification modules, a coding-decoding demodulation digital signal processor, an optical-fiber temperature sampling ring, an intrinsic temperature measuring optical fiber, a digital temperature detector and a personal computer (PC). The sensor codes and decodes a signal on the basis of the circulating S matrix conversion, and the online location temperature measurement of the optical fiber is realized by utilizing an effect that the optical-fiber Raman optical strength is demodulated by the temperature and utilizing an optical time domain reflection principle. The circulating laser pulse coding and decoding is realized, and a Rayleigh channel is used as a temperature demodulation reference channel, so that the signal-to-noise ratio of the system is greatly improved, and the measuring precision and the measuring distance of the system are improved.

Description

technical field [0001] The invention relates to a distributed optical fiber Raman temperature sensor, in particular to a distributed optical fiber Raman temperature sensor adopting cyclic pulse code decoding and Rayleigh demodulation, and belongs to the technical field of optical fiber sensing. Background technique [0002] Distributed optical fiber temperature sensor system is a sensor system for real-time measurement of spatial temperature field distribution. In the system, optical fiber is both a transmission medium and a sensing medium. The distributed optical fiber Raman temperature sensor uses the Raman spectrum effect of the optical fiber. The temperature field of each point in the space where the optical fiber is located modulates the optical carrier transmitted in the optical fiber. After demodulation, the information of the spatial temperature field is displayed in real time. It is a special optical fiber communication system; using optical time domain reflection (...

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Problems solved by technology

[0004] Single-mode optical fiber is more suitable for long-distance distributed optical fiber temperature sensing systems due to its low transmission loss, but single-mode optical fiber has a large bending loss, which will affect temperature detection in actual engineering applications

For the influence of bending loss, the general method is to use the Stokes reference channel to perform temperature demodulation on the anti-Stokes signal channel to offset, but due to the long optical wavelength of the Stokes channel, bending in single-mode fiber The loss is much stronger than the anti-Stokes signal (about 5 times for 1550nm system), so the effect of fiber bending loss cannot be effectively counteracted by using the Stokes reference channel

In addition, since the fiber nonlinear threshold power of the Stokes channel is much lower than that of the anti-Stokes channel, the input laser pump peak power of the system using the Stokes reference channel is mainly limited by the Stokes The nonlinear threshold power of the reference channel, and the lower the input laser pump peak power, the lower the signal-to-noise ratio of the system

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