Backreflection of the residual pump power into the cavity, and optimization
of the fiber length, may significantly improve the efficiency of a strongl
y pumped fiber laser. A rate equation model is introduced and studied. Exam
ples for Yb3(+)-doped fiber lasers, with DBR mirrors at either end, show th
at employing such a geometry results in higher efficiency with shorter opti
mal fiber length. Approximate analytical and quasi-analytical expressions a
re shown to be in excellent agreement with the exact numerical solution of
the rate equations.