Effect of photodetector on the noise conversion of the optical pulse train generated from mode-locked lasers

Noise conversion from relative intensity noise (RIN) to phase noise in the photodetection process of an optical pulse train is characterized by pump modulation method. It is found that the conversion ratio from RIN to phase noise is not sensitive to the noise power or the incident optical power, but decreases at a rate of 1/f with the increase of noise frequency. A new parameter related to the RF power difference of noise spurs is proposed and provides an easy way to describe the strength of the correlation between RIN and phase noise with no need of measuring the noise spectra of RIN and phase noise.