摘要
可调谐法布里-珀罗(F-P)滤波器的磁滞和温度漂移是限制其解调精度的重要因素。现有研究很少考虑同时对磁滞和温度漂移进行动态补偿。针对光纤布拉格光栅(FBG)解调误差,提出了一种基于最小二乘支持向量机(LSSVM)的动态补偿方法。考虑到参考光栅与传感光栅的反射光谱经过可调滤波器后具有相似的漂移特性,将多个参考光栅的波长漂移作为LSSVM模型的输入特征,以预测传感光栅的反射光经过可调滤波器后的波长漂移误差。在单调降温和先降温后升温的数据集上分别对所提方法进行了验证,实验结果表明:当未引入参考光栅作为模型特征时,两个数据集的补偿后最大绝对误差分别达到33.65 pm和69.25 pm;在引入参考光栅作为模型特征后,补偿后的最大绝对误差分别降至3.63 pm和7.84 pm,即所提方法在不同温变模式下均有效提高了F-P滤波器的解调精度。
Objective Tunable Fabry-Perot(F-P)filters powered by piezoelectric ceramics are prone to hysteresis and temperature drift in fiber Bragg grating(FBG)sensing systems.The demodulated wavelength of tunable F-P filters may produce significant drift during long-term monitoring,which exerts a significant impact on the measurement accuracy of FBG sensing systems.Incorporating a hardware calibration module into the FBG sensing system,including the reference grating method,gas absorption line method,F-P etalon method,and composite wavelength reference method,is the current way of error compensation for the tunable filter.These techniques can successfully reduce the drift error of tunable filters,but typically increase the technical complexity,structural complexity,cost,and even unidentified problems.As a result,it is now practical and affordable to employ a software compensation technique to predict and correct the output drift error of the tunable filter induced by hysteresis and temperature fluctuations.Unfortunately,the output drift error trend of tunable filters over time cannot be accurately tracked by conventional offline models,which limits the model's capacity to make up for it.Therefore,based on least squares support vector machine(LSSVM)and numerous reference gratings,this study proposes a dynamic compensation approach for tunable filter demodulation errors.Methods Four FBGs(FBGO,FBG1,FBG2,and FBG3)are employed for the reference and sensing gratings in this study.Firstly,the experimental environment's direct temperature-related values are chosen to serve as the dynamic compensation model's input characteristics.The high association between the wavelength drift errors of each FBG in the tunable filter's output spectrum is also thoroughly taken into account in this study.The drift of the reference grating is adopted in this study as one of the input features of the dynamic compensation model to compensate for the absence of precise temperature information inside the F-P cavity.This study employs moving window technology to continuously update the input and output feature quantities of the model and rebuilds the error compensation model to realize real-time prediction and compensation of the most recent drift error of the filter,thus preventing the model performance from degrading.It also highlights how the dynamic model's performance is affected by the moving window's length,the number of reference gratings,and the characteristic wavelength's separation between the reference grating and the sensing grating.The aforementioned approach has been validated in several temperature variation modes.Results and Discussions Firstly,FBG3 positioned in the top of the FBG arrangement distribution receives error compensation(Table 2).In the cooling mode,the maximum absolute error after dynamic compensation reduces from 39.12 pm to 2.53 pm as the number of reference gratings increases.As the number of reference gratings rises in the cooling-heating mode,the maximum absolute error after dynamic compensation falls from 77.02 pm to 8.78 pm.Secondly,FBG2 at the center of the FBG arrangement distribution receives error compensation(Table 3).In the cooling mode,the maximum absolute error after dynamic compensation reduces from 33.65 pm to 3.63 pm as the number of reference gratings in the dynamic model input features rises.The maximum absolute error after dynamic compensation falls from 69.25 pm to 7.84 pm in the cooling-heating mode as the number of reference gratings grows.The aforementioned findings demonstrate that as the number of reference gratings grows,the dynamic model's compensation accuracy gradually increases.Additionally,the experimental findings regarding the characteristic wavelength's distance between the reference grating and the sensing grating indicate that,for the same number of reference gratings,the closer characteristic wavelengths of the reference grating and the sensing grating leads to better compensation capacity of models whose spectral position is adopted as the input feature.Conclusions Firstly,this paper adopts the moving window technique as the foundation for building the online drift soft compensation model to prevent performance degradation of the initial model.Then,the experiment builds a nonlinear model between the surface temperature of the filter and the output drift error using the spectral locations of several reference gratings as the input features.The effectiveness of the model is also discussed concerning the moving window's length,the variety of reference gratings,and the characteristic wavelength's distance between the reference and sensing gratings.The experimental results on two datasets with various patterns of temperature variation show that the model's compensation capacity grows as the window length and the number of reference gratings do.Additionally,when the number of reference gratings is the same,the characteristic wavelengths of the reference grating and the sensing grating are closer to one another,and the dynamic model's compensation capacity is greater.In addition to the current hardware compensation method,the online dynamic soft compensation method presented in this study offers a fresh idea for real-time dynamic compensation of F-P filters'output drift errors.
作者
盛文娟
娄海涛
彭刚定
Sheng Wenjuan;Lou Haitao;Peng Gangding(College of Automation Engineering,Shanghai University of Electric Power,Shanghai 200090,China;College of Electrical Engineering and Telecommunications,The University of New South Wales,Sydney 2052,NewSouthWales,Australia)
出处
《光学学报》
EI
CAS
CSCD
北大核心
2023年第7期27-37,共11页
Acta Optica Sinica
基金
国家自然科学基金青年基金(61905139)
国家自然科学基金重点项目(61935002)。
关键词
光纤光学
光纤光栅解调
法布里-珀罗滤波器
解调误差
多参考光栅
动态补偿
fiber optics
fiber grating demodulation
Fabry-Perot filter
demodulation error
multi-reference gratings
dynamic compensation
