Power conversion efficiency analysis of distributed backward pumped fibre Raman amplifier

der to analyze the power conversion efficiency of backward pumped fibre Raman amplifier(FRA), by combining the shooting method with the RungeKutta method for solving differential coupling equations of backward pumped FRA, the effect of every parameter on backward pumped FRA-s power conversion efficiency was detailedly investigated. It is found that the power conversion efficiency is increasing with the increase of fibre length, until it reaches the maximum; the power conversion efficiency increases when the initial signal power or Raman gain coefficient or the attenuation coefficient of signal is larger, and it decreases when the fibre efficient area or the attenuation coefficient of pump or the pump and signal frequency ratio is larger; the relation between power conversion efficiency and initial pump power is para-curve. The conclusions are helpful to，further study the backward pumped FRA.