光CATV系统中提高受激布里渊阈值功率方法的研究

Analysis of Increasing Stimulated Brillouin Threshold Power in Lightwave CATV Systems

受激布里渊散射是限制光CATV传输系统入射功率从而限制系统传输距离的主要障碍 .本文研究了光CATV传输系统中提高受激布里渊阈值功率的一种方法———非均匀掺杂光纤法 .若光纤纤芯和包层参杂浓度沿传输方向变化 ,将导致布里渊频移发生变化 ,增益谱结构变化 ,最终影响受激布里渊阈值功率 .本文分析了阈值功率与布里渊频移分布之间的数量关系 ,设计了渐增型、周期正弦型、正弦型、三角型和平方型 5种沿光传输方向频移分布的方案 ,比较了它们提高SBS阈值功率的效果 .数值计算表明 :布里渊阈值功率可提高 2 0dB ,可将传输距离提高 1 0 0km .

Stimulated Brillouin scattering(SBS) is main obstacle to ligthwave CATV systems, that limits input power and therefore restricts the optical transmission distance. A novel method, namely nonuniform dopant concentration fiber, is investigated, with that SBS threshold power of lightwave CATV systems can be increased. If the dopant concentrations of core and cladding along the fiber length are varied, the Brillouin frequency shift and the Brillouin gain spectrum will change. The relationship between the SBS threshold and the Brillouin frequency shift is studied. Five schemes of Brillouin frequency shift distribution along its length are designed as follows: gather type, periodic sin type, sin type, triangle type, and square type. Their effects on increasing SBS threshold power are compared. The results of the numerical computations show that the transmission distance can be increased by 100?km.