Ferrario M, Marazzi Lucia, Boffi Pierpaolo, Righetti Aldo, Martinelli Mario
PoliCom, Dept. of Electronics and Information, Politecnico di Milano, Via G. Colombo 81, 20133 Milano, Italy.
Opt Express. 2009 Sep 28;17(20):18110-5. doi: 10.1364/OE.17.018110.
At bit rates comparable with the Brillouin shift, i.e. higher than 10 Gbit/s, the signal and the Brillouin backscattered spectra partially overlap. This implies an interaction between different scattering phenomena occurring through out the optical fiber. In particular we believe that an evaluation of how Rayleigh backscattered components of the modulated signal are subjected to Stokes gain is required. This interaction may lead to an increased backscattered power, which in turn will affect Brillouin threshold estimation. We experimentally verified a decrease of Stimulated Brillouin Scattering (SBS) threshold for 10 Gb/s NRZ-OOK signals with respect to theoretical predictions. Simulations carried out with a numerical model of SBS, accounting for Rayleigh contributions, well predict measured backscattered power levels. On the other hand we also experimentally verified that this SBS threshold decrease does not degrade transmission system performance. Indeed, measured BER curves put into evidence a penalty reduction for signal powers just before the saturation regime, which should be usefully taken into consideration in optical systems power budget planning.
在与布里渊频移相当的比特率下，即高于10 Gbit/s时，信号和布里渊后向散射光谱会部分重叠。这意味着在整个光纤中发生的不同散射现象之间存在相互作用。特别是，我们认为需要评估调制信号的瑞利后向散射分量如何受到斯托克斯增益的影响。这种相互作用可能会导致后向散射功率增加，进而影响布里渊阈值估计。我们通过实验验证了10 Gb/s非归零开关键控（NRZ-OOK）信号的受激布里渊散射（SBS）阈值相对于理论预测有所降低。使用考虑了瑞利贡献的SBS数值模型进行的模拟，很好地预测了测量的后向散射功率水平。另一方面，我们也通过实验验证了这种SBS阈值降低不会降低传输系统性能。实际上，测量的误码率（BER）曲线表明，在饱和状态之前的信号功率的惩罚降低，这在光系统功率预算规划中应予以充分考虑。
