ANALYSIS OF DISTRIBUTED ERBIUM-DOPED FIBER AMPLIFIERS WITH FIBER BACKGROUND LOSS

We present an accurate model for erbium-doped fiber amplifiers with fiber background loss applicable to the unsaturated gain regime. Exact analytical solutions are derived for the output pump power, gain, and amplified spontaneous noise as a function of input pump power in the cases of unidirectional or bidirectional pumping. An exact relation is also derived between the pump threshold and the pump required for fiber transparency. Such expressions are particularly useful to model distributed fiber amplifiers and to determine the optimal fiber parameters corresponding to a given pumping scheme. As an example, the analytical solutions are used to study the pump power requirement for distributed fiber amplifiers pumped unidirectionally at 1.48-mu-m, and to determine an optimum Er3+ absorption coefficient.