Uniform free-space cell shaping using diffractive-type beam diffusers for optical wireless links

This Letter presents the design of a diffractive beam diffuser to homogenize the irradiance within optical free-space cells generated from multimode fibers in an indoor high-speed network environment. Native speckled beams with a Gaussian envelope are transformed into circular flat-top distributions to guarantee a constant signal-to-noise ratio at the wireless receiving stage. Design considerations followed by the device fabrication and test results are given, showing its ability to shape narrow line-of-sight optical wireless cells operating at the Gbps range.