前向受激布里渊散射(F-SBS)是光纤中重要的三阶非线性效应，是进行外界物质识别和分析研究光纤物理特性的有力手段，成为近年研究的热点。本文通过对光纤中前向受激布里渊散射研究进展的调研和分析，整合了F-SBS的主要理论和传感原理，回顾了基于相位解调和能量转移探测的F-SBS测量手段，并重点介绍了本地光相位追溯技术、光力时域反射技术和光力时域分析技术等分布式传感技术。随着F-SBS传感器的逐渐实用化，对于F-SBS的高精度、高空间分辨力分布式测量的需求愈发显著，这将是未来光纤中前向受激布里渊散射的主要研究方向。

The phase-sensitive optical time-domain reflectometry (φ-OTDR) is a good candidate for distributed dynamic strain sensing, due to its high sensitivity and fast measurement, which has already been widely used in intrusion monitoring, geophysical exploration, etc. For the frequency scanning based φ-OTDR, the phase change manifests itself as a shift of the intensity distribution. The correlation between the reference and measured spectra is employed for relative strain demodulation, which has imposed the continuous measurement for the absolute strain demodulation. Fortunately, the Brillouin optical time domain analysis (BOTDA) allows for the absolute strain demodulation with only one measurement. In this work, the combination of the φ-OTDR and BOTDA has been proposed and demonstrated by using the same set of frequency-scanning optical pulses, and the frequency-agile technique is also introduced for fast measurements. A 9.9 Hz vibration with a strain range of 500 nε has been measured under two different absolute strains (296.7με and 554.8 με) by integrating the Rayleigh and Brillouin information. The sub-micro strain vibration is demonstrated by the φ-OTDR signal with a high sensitivity of 6.8 nε, while the absolute strain is measured by the BOTDA signal with an accuracy of 5.4 με. The proposed sensor allows for dynamic absolute strain measurements with a high sensitivity, thus opening a door for new possibilities which are yet to be explored.

Optical chirp chain Brillouin optical time-domain analysis (OCC-BOTDA) has the capabilities of fast measurement, high Brillouin threshold, and freedom from the nonlocal effect; at the same time, however, it also has problems introduced by transient stimulated Brillouin scattering. The influence of the transient interaction is reflected as the broadened asymmetric Brillouin spectrum, the ghost peak, and the frequency shift of the main peak. This introduces difficulty in computing the fiber Brillouin frequency shift with good measurement accuracy. Besides, the OCC modulation causes additional noise due to the uneven amplitude response for different frequency components. In this work, we propose a high-performance OCC-BOTDA using the principal component analysis (PCA) based pattern recognition algorithm and differential pulse-width pair (DPP) technique. After building the Brillouin spectrum database (i.e., all patterns), the fiber intrinsic Brillouin frequency shift can be recognized by the PCA algorithm from a nonstandard Brillouin spectrum profile, resulting in good measurement accuracy. Meanwhile, the DPP technique, subtracting between two Brillouin signals generated by two wide-width pump pulses, is utilized to reduce the OCC modulation noise and avoid the pulse self-phase modulation effect in long-range BOTDA sensing. In the experiment, a temperature measurement with 1.3?MHz measurement precision, 4?m spatial resolution, and 5?s measurement time is achieved over a 100?km single-mode fiber.

A 100-J-level Nd:glass laser system in nanosecond-scale pulse width has been constructed to perform as a standard source of high-fluence-laser science experiments. The laser system, operating with typical pulse durations of 3–5 ns and beam diameter 60 mm, employs a sequence of successive rod amplifiers to achieve 100-J-level energy at 1053 nm at 3 ns. The frequency conversion can provide energy of 50-J level at 351 nm. In addition to the high stability of the energy output, the most valuable of the laser system is the high spatiotemporal beam quality of the output, which contains the uniform square pulse waveform, the uniform flat-top spatial fluence distribution and the uniform flat-top wavefront.