The distributed acoustic sensing (DAS) has been extensively studied and widely used. A distributed acoustic sensing system based on the unbalanced Michelson interferometer with phase generated carrier (PGC) demodulation was designed and tested. The system could directly obtain the phase, amplitude, frequency response, and location information of sound wave at the same time and measurement at all points along the sensing fiber simultaneously. Experiments showed that the system successfully measured the acoustic signals with a phase-pressure sensitivity about –148 dB (re rad/μPa) and frequency response ripple less than 1.5 dB. The further field experiment showed that the system could measure signals at all points along the sensing fiber simultaneously.

We demonstrate a distributed optical fiber sensing system based on the Michelson interferometer of the phase sensitive optical time domain reflectometer (φ-OTDR) for acoustic measurement. Phase, amplitude, frequency response, and location information can be directly obtained at the same time by using the passive 3×3 coupler demodulation. We also set an experiment and successfully restore the acoustic information. Meanwhile, our system has preliminary realized acoustic-phase sensitivity around 150 dB (re rad/μPa) in the experiment.

提出了一种利用均匀相位掩模板制作啁啾光纤光栅(FBG)的方法。在对光纤的扫描曝光过程中, 相位掩模板沿长度方向周期性抖动, 且抖动幅度随光栅扫描长度的变化而变化, 使FBG的相位随着掩模板位置的变化而变化, 实现了FBG周期的线性调制, 从而得到线性啁啾FBG。掩模板抖动振幅的变化规律决定了FBG的啁啾系数。设计了3种不同的相位掩模板抖动函数, 实验制作了不同啁啾量的FBG。