New investigations on the effect of fiber amplifier phase noise

We investigated the effect of the phase noise of fiber amplifiers on the li newidth of the amplified signal. We used three different sources as input s ignal, with linewidth between 5 kHZ and 18 GHz. We did not observe any spec tral broadening of the signal linewidth at the output of the fiber amplifie r. This is in opposition with the generally admitted description of phase n oise in fiber amplifiers, but it confirms some recently published results. We propose a new theoretical description, which is in butter agreement with the experimental data.