Noise Figure Spectral Distribution of Erbium-Doped Fiber Amplifiers.

An analysis of the noise figure spectral distribution in erbium- doped fiber amplifiers is presented. In the case where signal- spontaneous beat noise is the dominant cause of SNR degradation, it is shown that noise figures in the range +- 0.15 dB around the 3 dB quantum limit are possible within a spectral band of 50 nm, with the result applying to both forward and backward pumping configurations. This study thus demonstrates the possibility of quantum-limited amplification for wavelength division multiplexed signals.