The Effect of Bias and Frequency on Amplitude to Phase Conversion of Photodiodes

Fluctuation of the optical power incident on a photodiode will cause phase variation of the electrical signal. This phenomenon is known as amplitude-to-phase (AM-to-PM) conversion. The effects of bias voltage and test frequency on AM-to-PM conversion are described systematically in this paper. A larger null point of AM-to-PM coefficient and smaller phase variation have been observed when bias voltage increases or test frequency decreases. The variation of transit time which is caused by different carrier velocity is the main reason of the phase variation. The influence mechanism of bias on AM-to-PM conversion has been explained in detail by giving the relationship between the carrier drift velocity and the internal electric field related to bias. When the internal voltage exceeds a certain value, the transit time will be almost unchanged and the phase variation is small because of saturated drift velocity. These results can provide guidance to operate the optoelectronic link under optimal conditions.