摘要
激光器脉宽是分布式光纤测温系统空间分辨率的主要影响因素之一,在光脉冲覆盖待测区域的情况下,系统无法准确解调出待测区域的准确温度。提出了一种拉曼信号分段与重构方法,通过分析光脉冲在待测区域处的信号特征,得出了激光脉宽对温度偏差的影响关系,并根据此关系对不同温度区域原始拉曼信号进行分段,借助待测区域长度、已知温度和待测温度下的拉曼光强差重构待测区域处的拉曼信号强度,利用重构后的拉曼信号进行温度解调,使系统空间分辨率、测温精度大幅提升。使用20 ns脉宽的光源(理论空间分辨率可达到2 m)、0.72 m测试光纤进行测试,结果表明,在90℃测试温度下,温度误差从33.9℃减小至5.8℃,系统空间分辨率由2.27 m提升至1.13 m。
Objective Currently distributed fiber optic temperature sensor has become an important tool for oil and gas storage tank seal ring fires,high temperature furnace crack detection,and thermal pipeline leakage detection.Most detection methods are judged by the temperature threshold and temperature rise rate.And when the leak area is too small and the system spatial resolution is insufficient,the temperature and temperature rise rate will be much lower than the actual value.As one of the main factors of the spatial resolution of the distributed optical fiber temperature measurement system,the pulse width of the laser determines whether the sensor can detect the occurrence of accidents in time.Therefore,it is necessary to use a method to reduce the impact of laser pulse width on the spatial resolution of the system.Methods A Raman signal segmentation and reconstruction method is proposed.By analyzing the signal characteristics of the laser pulse in the optical fiber at the region to be measured,the relationship between the laser pulse width and the temperature deviation is obtained.According to this relationship,the original Raman signal at different temperature regions is segmented into known temperature segments and temperature segments to be measured,and the Raman signal intensity at the region to be measured is reconstructed from the signal of the temperature segment to be measured with the help of a fitted signal to eliminate the Raman signal offset at the known temperature segment.Results and Discussions The method was tested using a laser source with 20 ns pulse width(the theoretical spatial resolution is about 2 m)and 0.72 m test fiber.The results show that within the test temperature range of 40-90℃,the temperature error is reduced from a maximum of 33.9℃to below 5.8℃,and the spatial resolution of the system was improved from 2.27 m to 1.13 m.Conclusions By analyzing the signal characteristics of the laser pulses passing through the high-temperature region,a Raman signal segmentation reconstruction method is proposed.By dividing the high temperature area covered by the laser pulse into the known temperature region and the temperature region to be measured,the signal offset of the known temperature segment is removed and the signal of the high temperature area is reconstructed according to the signal intensity of the temperature segment to be measured.A test is carried out using 20 ns laser pulses and 0.72 m test fiber.The results show that the temperature error is reduced from 33.9℃to 5.8℃at 90℃,and the spatial resolution of the system is improved from 2.27 m to 1.13 m.This method mainly solves the temperature measurement error when the length of the optical fiber in the area to be measured is less than the laser pulse width,and has outstanding advantages for small-scale leakage monitoring.The remaining temperature error mainly comes from insufficient APD bandwidth.This method can gradually shorten the measurable temperature region length and temperature accuracy with the increase of APD bandwidth.
作者
李硕
王纪强
高忠国
高建新
侯泽民
姜龙
侯墨语
Li Shuo;Wang Jiqiang;Gao Zhongguo;Gao Jianxin;Hou Zemin;Jiang Long;Hou Moyu(Faculty of Optoelectronic Science and Technology,Qilu University of Technology,Jinan 250104,China;Inner Mongolia Shuangxin Mining Co.,Ltd.,Ordos 017001,China;Shandong Micro-sensor Photonics Limited,Jinan 250104,China)
出处
《红外与激光工程》
EI
CSCD
北大核心
2023年第10期285-290,共6页
Infrared and Laser Engineering
基金
国家重点研发计划(2022YFB3207602)
山东省自然基金重点项目(ZR2020KC012)。
关键词
分布式温度传感器
空间分辨率
温度精度
拉曼信号分段
拉曼信号重构
distributed temperature sensor
spatial resolution
temperature accuracy
Raman signal segmentation
Raman signal reconstruction
