We propose an optical spatial filter (OSF) method to suppress beam wander and spatial noise effects. Signal from random\ndisplacements of the focus spot around the optical axis within the constricted area is collected. This method advantageously\nsuppresses fluctuations in signal intensity.The OSF consists of a pinhole and cone reflector.The pinhole produces Fresnel diffraction\non the focus spot. The cone reflector provides directed reflectance onto the pinhole for random focus spot displacements due to\nbeam wander. The calculations of signal power are based on fluctuations of signal intensity that are minimized by the circular\naperture function of the pinhole and the cosine of the reflectance angle from the cone reflector.The method is applied to free-space\noptical communications at a wavelength of 1.55 ????m with an atmospheric chamber to provide optical propagation media. Based\non calculations, the beam wander angles that can be received by the OSF are from 14.0? to 28.0?. Moreover, based on experiment,\nthe OSF with a pinhole diameter of 20.0 ????m and cone reflector diameter of 1.5mm produces signal power of ?15.3 dBm. Both\ncalculations and experiment show that the OSF enhances the received signal power in the presence of turbulence.
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