Study on optimum fiber length for maximum gain in C- and L-band EDFAs

We study the optimum fiber length for maximum gain of C- and L-band Erbium Doped Fiber Amplifiers (EDFAs) with fixed pump power. We show that the dependence of the optimum length on the wavelength and power of the signal is stronger in the L than in the C band and validate our findings trough distributed gain measurements. We also show that the predictions of the transcendental power equation model, which neglects the Amplified Spontaneous Emission (ASE), give accurate results for the optimum length even of L-band EDFAs, fact not obvious a priori because of the key rule played by the ASE as a pump source in amplifiers operating in this region.