A new type of 1:1 optical branch for optical fiber with low insertion loss was fabricated using three graded-index rods. Two pieces of the graded-index rods were cut in parallel to their own optical axes and cemented together with the cut surfaces, and then the third rod is butt-joined to the combined rods. The experimental results were that the insertion loss was 1.1 dB and the distribution ratio was 1:0.98 at 6328 wavelength. Minor modification of this structure enables us to get distribution rations other than 1:1.

A three-terminal optical branch for multimode fiber was fabricated. Two pieces of optical fiber were side ground and glued together with the ground surfaces, the third optical fiber was butt-joined to the coupled fibers. The distribution ratio was 1:0.84 and the insertion loss was 3.2 dB for incoherent LED (8700) as well as for coherent He-Ne laser (6328).