Abstract
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.
Highlights
Low-noise microwave signals are required for many applications such as microwave signal generation [1], phased-array radars [2], and coherent optical communication [3]
The RF signal from the PD is received by port 2 of the vector network analyzer (VNA) through the alternating current (AC) port of a bias tee, and the photocurrent of this link is monitored by sourcemeter through the direct current (DC) port of the bias tee
We have studied the phase variation caused by the fluctuation of incident optical power, and found it is consistent with the relationship between optical power and phase variation in other literature
Summary
Low-noise microwave signals are required for many applications such as microwave signal generation [1], phased-array radars [2], and coherent optical communication [3] These systems are very sensitive to the phase response of optoelectronic devices. We qualitatively give a schematic diagram to explain the reason why the phase variations are different when the bias voltages of PD are different It is proposed for the first time that when the electric field attenuation caused by incident optical power is not sufficient to make the drift velocity less than the saturated drift velocity, the phase is almost unchanged. We attribute the aforementioned phenomena to the change of carrier velocity and high-frequency response capability of PD, respectively These studies have been motivated by technological applications of PDs and for an increasing understanding of the mechanism of AM-to-PM conversion
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