Nonlinear fiber system for shot-noise limited intensity noise suppression and amplification.

We propose a nonlinear fiber system for shot-noise limited, all-optical intensity noise reduction and signal amplification. The mechanism is based on the accumulation of different nonlinear phase shifts between orthogonal polarization modes in a polarization-maintaining fiber amplifier in combination with an implemented sinusoidal transmission function. The resulting correlation between the input intensity fluctuations and the system transmission enables tunable intensity noise reduction of the input pulse train. In the experiment, the noise spectral density of a mode-locked oscillator is suppressed by up to 20 dB to the theoretical shot-noise limit of the measurement at -151.1/ with simultaneous pulse amplification of 13.5 dB.