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针对φ-OTDR振动传感系统中的相位模糊问题,推导了背向瑞利散射光功率与干涉光场相位差、干涉光场相位差与光纤应变的关系式,分析了相位模糊现象的发生原因及表现形式,研究了相位模糊对传感系统性能的影响及系统最大可检测应变与空间分辨率的关系,并进行了仿真验证。结果表明:相位模糊是限制系统应变测量范围的主要因素,它会引起振动频率的误判和振动幅度的测量错误,还可能导致大应变信息的漏报;系统空间分辨率越高,应变测量范围越大,说明φ-OTDR振动传感系统适用于高空间分辨率振动的测量。研究结果为φ-OTDR振动传感系统参数设计和系统优化提供了理论参考。
Aiming at the problem of phase ambiguity in φ-OTDR vibration sensing system, the relationship between the optical power of back-and-back Rayleigh scattering, the phase difference of interfering light field, the phase difference of interfering light field and the optical fiber strain is deduced. The causes of the phase ambiguity are analyzed And its manifestations, the influence of phase ambiguity on the performance of the sensing system and the relationship between the maximum detectable strain and the spatial resolution of the system are studied, and the simulation is verified. The results show that the phase ambiguity is the main factor that limits the measurement range of the system strain. It can lead to misjudgment of vibration frequency and measurement error of vibration amplitude, and may lead to omission of large strain information. The higher the spatial resolution of the system, The larger, φ-OTDR vibration sensing system for high spatial resolution vibration measurements. The results provide a theoretical reference for the parameter design and system optimization of φ-OTDR vibration sensor system.