基于差分-补偿-积累算法的Ф-OTDR系统相位解调方法  

Phase Demodulation Method forФ-OTDR System Based on Differential-Compensation-Accumulation Algorithm

作　　者：张立欣[1,2,3] 康清华 黄达 霍锴 刘紫娟 李永倩 Zhang Lixin;Kang Qinghua;Huang Da;Huo Kai;Liu Zijuan;Li Yongqian(Department of Electronic&Communication Engineering,North China Electric Power University,Baoding 071003,Hebei,China;Hebei Key Laboratory of Power Internet of Things Technology,North China Electric Power University,Baoding 071003,Hebei,China;Baoding Key Laboratory of Optical Fiber Sensing and Optical Communication Technology,North China Electric Power University,Baoding 071003,Hebei,China)

机构地区：[1]华北电力大学电子与通信工程系,河北保定071003 [2]华北电力大学河北省电力物联网技术重点实验室,河北保定071003 [3]华北电力大学保定市光纤传感与光通信技术重点实验室,河北保定071003

出　　处：《光学学报》2024年第21期37-45,共9页Acta Optica Sinica

基　　金：国家自然科学基金(62205105,52177141);中央高校基本科研业务费专项基金(2023MS111);河北省省级科技计划(SZX2020034)。

摘　　要：基于相位敏感光时域反射计的分布式声波传感系统常用于振动信号的检测,但在相位解调时容易产生相位模糊现象,导致解调后的相位值失真、难以准确反映振动信息。针对相位模糊问题,本文提出一种基于差分-补偿-积累的相位解调算法,可有效避免相位变化幅度超出2π时产生的相位错乱现象,实现振动信号相位信息的准确提取。首先,对数字正交相位解调得到的相位信号进行一次后向差分,消除积累的相位噪声,避免相位噪声的全局传播,最小化误差;然后,在差分域选择合适的补偿系数对相位信号进行补偿,扩大差分-补偿-积累方法的解调范围;最后,将补偿后的相位进行累加获得准确的相位值。实验结果表明,本文方法在10 m空间分辨率下实现了20、60、100 Hz振动信号的重建,并有效降低了相位噪声的干扰,提升了系统信噪比。Objective Distributed acoustic sensing systems based on phase-sensitive optical time-domain reflectometer(Ф-OTDR)are commonly used for vibration signal detection.When external vibrations are applied to the sensing optical fiber,the fiber’s refractive index changes,leading to variations in the phase of the backscattered Rayleigh light at the vibration location.Since the phase change of the backscattered Rayleigh light is linearly related to the vibration applied to the fiber,external vibration signals can be measured based on these phase changes.However,phase ambiguity often occurs during demodulation,resulting in distorted phase values,making it difficult to accurately reflect the vibration information.Common demodulation methods,such as the arctangent method,can extract the phase,but due to the phase’s periodicity and variability,only the wrapped phase with a period of 2πand a principal value interval from−πtoπcan be obtained.As the vibration measurement range increases,if the phase change exceeds 2π,phase ambiguity occurs,leading to demodulated phase results that cannot accurately reflect the vibration amplitude and frequency.Methods To address the phase ambiguity issue,we propose a phase demodulation algorithm based on differentialcompensation-accumulation,building on digital in-phase and quadrature(IQ)demodulation.This algorithm provides a reliable phase compensation scheme to solve phase ambiguity,making the differential phase no longer dependent on the jump threshold ofπ.It effectively avoids phase misalignment caused by phase changes exceeding 2π,enabling accurate extraction of phase information from vibration signals.TheФ-OTDR digital IQ demodulation process is divided into three processes:mixing,filtering,and phase demodulation.Since the phase information obtained by digital IQ demodulation is mainly distributed between−π/2 andπ/2,arctangent unwrapping in a four-quadrant manner is required.A backward differential operation is then applied to the arctangent phase signal to eliminate accu

关 键 词：相位敏感光时域反射计 相位解调 振动监测 相位模糊 

分 类 号：TP212[自动化与计算机技术—检测技术与自动化装置]