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An experimental study of coupling efficiency of a circular multimode fiber coupler dependency of radiation from macro-bending is investigated on the basis of simplified coupled mode theory. The study is investigated by experimental set-up using various radii of circular blocks customized with matching refractive index material. The aim is to provide a considerable explanation on the differences in splitting ratio, excess loss and insertion loss when different bending radii due to radii of circular blocks is applied to the couplers. Other factors that contribute to the characterization of the coupler include fiber diameters and forces exerted upon the two fibers that lapped together forming the coupler developed. The technique used is proven to develop a low-cost coupler using mechanical lapping technique