The influences of fiber loss and pump depletion on single-pump four-wave mixing (FWM) parametric process in the isotropic and highly-nonlinear optical fiber are considered. The power conversion relation of the guided optical waves is expressed by an elliptic equation, and the calculated results are consistent with the simulation datum obtained by OptiSystem software. The elliptic equation is also used to analyze the performance of all optical 2R regenerators based on FWM. The research shows that the increase of fiber loss coefficient can not only deteriorate the re-amplifying performance, but also lead to the decrease and increase of noise tolerances of input high and low levels, respectively.