Characterization and theoretical analysis of second-order intermodulation distortion of InGaAs/InP p-i-n photodiode modules for fiber-optic CATV

InGaAs/InP p-i-n photodiode (PD) modules for fiber-optic analog CATV have been developed. The optical configuration was optimized by making use of a spherical lens aberration. Responsivity and second-order intermodulation distortion (IMD2) were 0.95 A/W and -85 dBc at V/sub r/=12 V, P/sub in/=0 dBm, and m=40%, respectively. The improvement of IMD2 by defocusing was explained by the decrease of incident optical power density calculated by ray tracing. IMD2 was quantitatively explained through the reverse voltage dependence of responsivity which originates from the variation of the p/sup +/-InGaAs depletion layer thickness.