Gh. Duan et E. Georgiev, Non-white photodetection noise at the output of an optical amplifier: Theory and experiment, IEEE J Q EL, 37(8), 2001, pp. 1008-1014
Based on the statistical properties of amplified spontaneous emission, the
photodetection noise spectrum at the output of an optical amplifier is calc
ulated. The results revealed that the signal-spontaneous emission beat nois
e spectrum is a transposition of the spontaneous-emission spectrum to the l
ow-frequency domain, and the spontaneous emission-spontaneous emission beat
noise spectrum is the auto-correlation function of the spontaneous-emissio
n spectrum. These theoretical results are verified experimentally on an erb
ium-doped fiber amplifier, filtered by a Mach-Zehnder interferometer.