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针对传统的通过功率信息测量所得受激布里渊散射阈值偏高的问题,提出了一种利用布里渊散射谱宽确定光纤受激布里渊散射阈值的新方法。分析了本地外差检测的原理及布里渊散射谱宽与入纤光功率的关系;设计了基于本地外差检测的布里渊散射谱测量系统,在常温下对不同长度标准单模光纤的受激布里渊散射阈值进行了测量。实验结果表明:当光纤长度分别为48.8 km和9.5 km时,根据功率信息获得的受激布里渊散射阈值对应的布里渊散射谱宽均接近恒定值10 MHz,此时已发生严重的泵浦耗尽效应。利用布里渊散射谱表现出的低入纤功率时谱宽的线性下降特性和高入纤功率时谱宽的功率无关特性确定的两种光纤长度下的受激布里渊散射阈值分别为1.12 m W和3.8 m W,对应的布里渊散射谱宽分别为24.86 MHz和23 MHz,其值近似等于布里渊自然线宽。文中的研究结果对布里渊光时域反射系统最大入纤光功率的确定具有重要的参考价值。
Aiming at the problem that traditional stimulated Brillouin scattering threshold is too high by power information measurement, a new method to determine the threshold of fiber stimulated Brillouin scattering using Brillouin scattering spectrum is proposed. The principle of local heterodyne detection and the relationship between the Brillouin scattering spectrum width and the input fiber power are analyzed. A Brillouin scattering spectrum measurement system based on local heterodyne detection is designed. At different temperatures, Stimulated Brillouin scattering thresholds were measured. Experimental results show that when the fiber lengths are 48.8 km and 9.5 km respectively, the Brillouin scattering spectral widths corresponding to the stimulated Brillouin scattering thresholds obtained according to the power information are all close to a constant value of 10 MHz. At this time, a serious pump has occurred Pu depletion effect. The thresholds of stimulated Brillouin scattering for the two fiber lengths determined by the linear decrease of the spectral width at low input fiber power and the power independent characteristic of the high input fiber power are respectively 1.12 m W and 3.8 m W, respectively. The corresponding Brillouin scattering spectral widths are 24.86 MHz and 23 MHz, respectively, which are approximately equal to the natural line width of Brillouin. The research results in this paper have an important reference value for the determination of the maximum input fiber power of the Brillouin optical time-domain reflection system.