基于实时STF-VCFIR滤波器系统的OFDR谐波噪声消除  

OFDR Harmonic-Noise Elimination Based on a Real-Time STF-VCFIR Filter System

作　　者：帅禄玮 叶蕾 李璇[1,2] 王照勇 高侃[1] 叶青 Shuai Luwei;Ye Lei;Li Xuan;Wang Zhaoyong;Gao Kan;Ye Qing(Key Laboratory of Space Laser Communication and Detection Technology,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China;Shanghai Zhongke Shenguang Optoelecronic Industry Co.,Ltd.,Shanghai 201815,China)

机构地区：[1]中国科学院上海光学精密机械研究所空间激光传输与探测技术重点实验室,上海201800 [2]中国科学院大学材料与光电研究中心,北京100049 [3]上海中科神光光电产业有限公司,上海201815

出　　处：《中国激光》2025年第2期170-177,共8页Chinese Journal of Lasers

基　　金：国家重点研发计划(2023YFB2905300);国家自然科学基金(U23A20379);上海市科技攻关项目(23xtcx00500,23DZ1203900,22ZR1471100);中国科学院青年创新促进会项目(YIPA2023257);上海科技启明星项目(22QB1406000)。

摘　　要：随着光频域反射计(OFDR)探测精度(<-100 dB)的提高,谐波噪声对探测的干扰逐渐增大,可能会导致OFDR系统出现传感误差或者误判。在传统的信号处理中,可以采用滤波器对谐波噪声进行消除;但是OFDR信号具有时变特性,传统滤波器无法完全消除谐波噪声。鉴于此,本课题组提出了一种实时短时频率-可变系数有限长脉冲响应(STF-VCFIR)滤波器系统。该系统通过测量辅助干涉仪信号的短时频率、动态调节滤波器系数、对探测信号进行实时滤波处理,改善了传统滤波器导致的谐波泄漏的缺点,大幅降低了噪声的影响。最终通过实验证明了该系统可在实时处理的同时实现对谐波噪声的消除。与无滤波系统相比,该系统对谐波噪声的最大消除可达8 dB以上,使得谐波噪声降低到-102.7 dB以下,达到与噪声均值相同的水平,减小了将谐波噪声误判为反射点的概率,提高了系统判别的准确性。Objective As an advanced fiber-optic sensing technology,optical frequency domain reflection(OFDR)has attracted increasing attention from researchers since its first proposal in the 1980s,owing to its advantages of high spatial resolution,high sensitivity,and high precision range.However,as the detection accuracy improves,errors and noise in some signal-processing processes can affect OFDR detection.Harmonic noise is common in analog signal processing and analog-to-digital converters.Operational amplifiers,transistors,and analog-to-digital converter chips,which are commonly used in analog signal processing,introduce harmonic noise.Because harmonic noise is generally separated from the measured signal in the frequency domain,traditional filters can eliminate it.However,this does not apply to OFDR signals.When harmonic noise appears in a signal’s frequency domain,it may interfere with the OFDR detection or sensing results,causing sensing errors or erroneous judgment results.In this study,we design a real-time short-term frequency variable-coefficient finite-length impulse response(STF-VCFIR)filter system.We use a field-programmable gate array(FPGA)as the real-time processing unit of the system and design a real-time computing method based on the pipeline characteristics of FPGA processing.Methods In this study,we analyzed the impact of harmonic noise on the OFDR and theoretically calculated the location of harmonic-noise occurrences.Through analysis,we know that the position of harmonics in the spectrum changes with the number of harmonics and may not necessarily be greater than the signal position.However,when the harmonic frequency is lower than the signal frequency,the harmonics overlap with the signal and are difficult to remove.This implies that harmonic signals must be filtered out before resampling.We drew a time-frequency graph of the OFDR signal and compared it with those of traditional filters.Thus,we know that the fixed cut-off frequency of traditional filters cannot completely eliminate harmonic noise.

关 键 词：光纤传感技术 光频域反射计(OFDR) 现场可编程门阵列(FPGA) 实时处理 可变系数滤波器 噪声消除 

分 类 号：TN253[电子电信—物理电子学]