POLARIZATION-DEPENDENT GAIN IN ERBIUM-DOPED FIBER AMPLIFIERS - COMPUTER-MODEL AND APPROXIMATE FORMULAS

A computer model for polarization dependent gain (PDG) in Er-doped fib er amplifiers (EDFA) is presented, The model assumes that each erbium ion possesses an ellipsoidal gain surface and that all ion orientation s are equally likely, By dividing the ions into subsets based upon ori entation and computing the inversion of each subset in the presence of polarized pump and signal waves, the model predicts the dependence of the PDG induced by this polarization hole-burning (PHB) on the design of the EDFA, the signal degree and state of polarization (SOP), and t he pump SOP, For moderate gain amplifiers (made from the same fiber) w ith the same gain peak wavelength and the same compression level, the magnitude of the PDG is nearly independent of the EDFA gain, Internal and random fiber birefringence are included to model real fibers, In f ibers which cause the signal SOP to walk rapidly around the Poincare s phere, the PDG is reduced by a factor of 2/3 when compared with a line ar polarization-maintained signal. Scrambled signals and partially pol arized saturating tones are also considered, Simple rules are derived for predicting the PDG of a given EDFA.