Temperature monitoring method of distributed optical fiber system

Abstract

The invention discloses a temperature monitoring method of a distributed optical fiber system. The method includes: dividing laser into two laser beams, modulating one laser beam with pulse or random sequence signals to obtain pulsed light, and amplifying the pulsed light; modulating the other laser beam with OFDM (orthogonal frequency division multiplexing) signals to obtain optical OFDM signals, and amplifying the optical OFDM signals; using the amplified pulsed light as pumping light, and using the amplified optical OFDM signals as probe light; subjecting the pumping light and the probe light to Brillouin gain in a single mode fiber; performing photovoltaic conversion to the pumping light and the probe light subjected to Brillouin gain to obtain OFDM electrical signals; performing channel estimation to the OFDM electrical signals to obtain Brillouin frequency shift of each subcarrier; and obtaining temperature of points distributed along an optical fiber shaft according to the Brillouin frequency shift of each subcarrier. By the method, measuring time can be shortened, measuring precision can be increased, dynamic range can be increased greatly, power grid system temperature can be monitored in real time, and reliability and instantaneity of a distributed sensing system can be improved.

Description

【Technical field】 [0001] The invention relates to the technical field of temperature measurement of a power system, in particular to a method for temperature monitoring by using a distributed optical fiber system. 【Background technique】 [0002] In the power system, high temperature and fire are common accidents that affect the safe operation of the power system. Therefore, the quality of online temperature monitoring is a very important aspect affecting the safe operation of power systems. If early warnings can be made through temperature measurement and measures can be taken quickly in the early stages of safety accidents, such safety accidents can be effectively avoided. The traditional temperature measurement method is to install point temperature sensing elements such as thermocouples in important parts of cables or power systems for temperature measurement, or to use fiber gratings and quasi-distributed measurement methods for temperature measurement. However, these t...

AI Technical Summary

Problems solved by technology

However, the distributed optical fiber sensing technology based on Raman scattering has the following problems: the Raman backscattering coefficient is too small, and the scattered light is relatively weak; the detection response time is long; the peak power of the pulsed laser source needs to be quite high, which is difficult to achieve

However, the distributed optical fiber sensing technology based on Brillouin scattering has the following problems: (1) The spontaneous Brillouin scattered light generated in the system is relatively weak; (2) The Brillouin frequency shift in the system is very small, and the measurement is very difficult ;(3) Since the Brillouin frequency shift is very small, the requirements on the filter are extremely high, and the measurement accuracy is not high, which affects the measurement accuracy; (4) The detection response time is long

However, this technology has the following problems: (1) high frequency stabilization requirements for light sources; (2) due to the need for a large number of analysis points, in order to improve the test sensitivity, multiple averages are required, so the test time is very long; (3) the gain-type sensing method It will cause a sharp decrease in the energy of the pump light, making it difficult to achieve long-distance detection

[0015] The lossy BOTDA distributed optical fiber sensing technology based on microwave external modulation mainly has the following technical defects: (1) the single-ended scheme cannot realize long-distance sensing; (2) in order to improve the measurement accuracy, it is necessary to measure multiple frequency points, multiple Average, so the measurement time is longer; (3) Because this program needs to perform statistical analysis on a large number of experimental data, it has high requirements for experimental equipment and environment

This greatly affects the detection speed of the Brillouin scattering spectrum, making the BOTDA system unsuitable for the field of health monitoring with high dynamic characteristics

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