Method and apparatus for side launch excitation of selected modes in graded-index optical fibers

摘要

An optical fiber having a parabolic-index profile is etched to a taper below the cladding layer. A prism contacts the taper along its length within the etched portion of the fiber, and coherent light is transmitted through the prism into the fiber. Selective control of the light beam entry angle, entry position along the taper, and control of the etching depth allows excitation of specific modes within the fiber and maximization of coupling efficiency.