An alysis of gain an d n oise pe rform an c e of bid ire c tion ally pu m pe d Pr 3+ -d ope d¯u orid e ® bre am pli® e r c on ® gu ration s w ith u n balan c e d pu m pin g Abs trac t.This paper presents a numerical study of the performance of asymmetric bidirectionally pumped and re¯ective-type ampli® er con® gurations in the unsaturated and saturated regions. The dependences of the optimum relative backward pump power on the ® bre parameters and on the ampli® er's working conditions for each con® guration are analysed. This study has been made in the frameworkof the European Project COST 241: Characterization of Active Fibres for the Photonic Network.