单频拉曼光纤放大器中受激布里渊散射的抑制

Suppression of Stimulated Brillouin Scattering in Single-Frequency Raman Fiber Amplifiers

高功率单频拉曼光纤放大器(RFA)的性能往往会由于受激布里渊散射(SBS)的出现而受到限制。在综合考虑受激拉曼散射和SBS过程的基础上,提出了SBS限制下的RFA中的强度耦合方程组。通过在耦合方程中加入温度场和应力场,讨论温度场和应力场对SBS阈值的影响。分析表明,虽然单独依靠温度场或者应力场都能很好地抑制SBS,提升放大器的性能,但要求都比较苛刻,很难真正实现。提出了一种综合使用温度和应力梯度的方案,在实际可操作的范围内,将RFA的输出功率提高了3倍。数值模拟的结果为实验研究高功率单频RFA中抑制SBS提供了一定的指导。

High power operation of single-frequency Raman fiber amplifiers（RFA） is usually limited by the onset of stimulated Brillouin scattering（SBS）.We present our theoretical investigation on RFA limited by SBS,based on the intensity equations combining SBS and stimulated Raman scattering.The influence of temperature gradients and strain gradients,which can broaden the SBS gain profile and thereby increase the SBS threshold,on the performance of RFA is discussed.Although tensile strain and temperature gradients can suppress SBS in RFA separately,the conditions are too rigorous to realize.A feasible scheme for suppression of SBS in RFA is proposed using the temperature gradients together with tensile strain gradients along the fiber length,resulting in an increase of about 3 times of amplifier output power.The results of simulation provide a guide to suppress SBS in high power single-frequency RFA.