An optical fiber coupler comprises an optical fiber, an implant and a coupling medium. The optical fiber is used to guide light progression and contains a light exit end formed at one end. The implant has a through hole for insertion by the light exit end. The coupling medium is filled between the implant and the optical fiber light exit end for the combination of the implant and the optical fiber and has a refractive index different from that of the optical fiber. Accordingly, this invention can use the coupling medium to affect light progression path so as to slightly change the intensity of exiting light, having the advantages of simple structure, low cost and convenient usage.
