With the rapid development of the radio over fiber (ROF) system,photoelectric conversion efficiency has become an important factor in evaluating its performance.This paper investigates the key factors affecting photoelectric conversion efficiency through theoretical analysis,simulation studies,and system experiments.First,theoretical analysis reveals that optimal photoelectric conversion efficiency is achieved when the beam spot profile aligns with the photosensitive surface of the photodetector.Then,using ZEMAX simulations,it is found that under given light source and transmission distance conditions,the received optical power is maximized when the beam spot radius is half that of the photodetector′s photosensitive surface.Furthermore,as the laser divergence angle increases from 3° to 30°,the optical power sharply decreases from 3 mW to 0.56 mW,and the spot image tends to be saturated.In addition,as the laser transmission distance increases,the beam width and divergence increase,reducing the detector′s received optical power.Finally,a small-scale ROF experimental system is built,and the accuracy of the simulation results is verified through spot acquisition using a CMOS camera and optical power detection experiments.