用于分布式声学传感的带尾重用重建的无循环前缀正交频分复用
Cyclic-Prefix-Free OFDM With Tail-Reuse Reconstruction for Distributed Acoustic Sensing
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中文总结 AI 辅助
研究用于分布式声学传感的无循环前缀OFDM波形，利用前一有用块尾部作虚拟循环扩展实现尾重用重建，推导相关条件。通过模拟和实验验证该方法可行性，量化无混叠振动带宽扩展，提高了探测性能。
中文摘要 AI 辅助
正交频分复用（OFDM）能在相干分布式声学传感（DAS）中对分布式瑞利后向散射信道进行频域重建，但显式传输的循环前缀（CP）会延长探测周期并降低每个距离单元的慢时间奈奎斯特极限。本文研究了一种用于DAS的重复无循环前缀OFDM波形，其中前一个有用块的尾部用作虚拟循环扩展。推导了尾重用重建的有限记忆范围条件，并确定了有用周期短于信道记忆时的循环折叠情况。对于固定的有用块长度和光纤记忆，去除显式CP可提高周期限制的最高无混叠振动频率，而不改变占用带宽限制的空间分辨率。在5.2公里的数值配置中，75兆采样每秒的处理速率和4096样本的有用块给出了54.61微秒的探测周期和9.16千赫兹的慢时间奈奎斯特极限。模拟验证了尾重用、预测的折叠边界以及从800赫兹到8800赫兹的100个振动事件的恢复。带宽缩放模拟进一步表明，在固定报告间隔下，精细空间观测的联合处理可提高差分相位可靠性和重建信噪比。在具有111.984兆赫兹占用OFDM带宽的5.2公里相干DAS链路上的实验分别在5063.7米和5070.1米处盲目定位了500赫兹和3千赫兹的PZT引起的振动，并恢复了它们的波形和频谱。结果证明了尾重用信道重建的可行性，并量化了无混叠振动带宽的扩展。
英文摘要
Orthogonal frequency-division multiplexing (OFDM) enables frequency-domain reconstruction of the distributed Rayleigh backscatter channel in coherent distributed acoustic sensing (DAS), but an explicitly transmitted cyclic prefix (CP) lengthens the probing period and reduces the slow-time Nyquist limit of each range cell. We investigate a repeated cyclic-prefix-free OFDM waveform for DAS, in which the tail of the preceding useful block serves as a virtual cyclic extension. A finite-memory range condition for tail-reuse reconstruction is derived, and circular folding is identified when the useful period is shorter than the channel memory. For fixed useful-block length and fiber memory, removing the explicit CP increases the period-limited highest unaliased vibration frequency without changing the occupied-bandwidth-limited spatial resolution. In a 5.2-km numerical configuration, a 75-MSa/s processing rate and a 4096-sample useful block give a 54.61-us probing period and a 9.16-kHz slow-time Nyquist limit. Simulations verify tail reuse, the predicted folding boundary, and recovery of 100 vibration events from 800 Hz to 8800 Hz. Bandwidth-scaling simulations further show that joint processing of fine spatial observations improves differential-phase reliability and reconstruction SNR at a fixed reporting interval. Experiments on a 5.2-km coherent DAS link with 111.984-MHz occupied OFDM bandwidth blindly localize 500-Hz and 3-kHz PZT-induced vibrations at 5063.7 m and 5070.1 m, respectively, and recover their waveforms and spectra. The results demonstrate feasible tail-reuse channel reconstruction and quantify the extension of the unaliased vibration bandwidth.
