Localization Enhancement of Forward-Transmission Distributed Vibration Sensors Using Phase Differentiation Endpoint Amplification

Forward-transmission fiber-optic distributed vibration sensors have potential use in long-distance sensing and integration with optical communication networks. However, the ability to localize disturbance events with low frequency is fairly inferior to high-frequency events, which hinders the broader application of such distributed vibration sensors. To address this problem, we propose a phase differentiation endpoint-amplification (PDEA) method to optimize the sensor's frequency response for event localization. By differentiating the original extracted phase signal, the proposed method amplifies the amplitude of the endpoints of the disturbance event. Via cross correlation (CC), the endpoint amplitude amplification reduces the localization errors. Experimental results demonstrate that the forward-transmission sensing system using the proposed method maintains a localization accuracy within ±51 m across frequencies from 300 Hz to 10 kHz over a 122-km range. In addition, the system's localization capability for low-frequency disturbances occurring at the near end is notably enhanced. The PDEA algorithm significantly improves the wide-frequency response of forward-transmission fiber-optic distributed vibration sensors. The enhanced localization ability will be beneficial when the sensors are applied in scenarios, such as integrated optical sensing and communication (IOSAC).