DESIGN CONSIDERATIONS FOR AN ER-3+-DOPED FIBER AMPLIFIER

This paper theoretically determines the optimum fiber parameters for an Er3+-doped fiber amplifier pumped at 1.48-mu-m using the rate equation for a three-level laser system and Gaussian beam approximation for the guided wave. It is shown that the signal gain is improved by decreasing the Er3+-doped radius a0. For a step-index fiber, the optimum cutoff wavelength for maximizing the signal gain is found to be 0.8-mu-m regardless of relative-index difference-DELTA when the core area radius a is filled with Er3+ ions. It is also shown that the optimum cutoff wavelength increases as a0 decreases. Moreover, it is shown that the signal gain depends on the index profile.