Bi-directional optical fiber coupler

Abstract

A bi-directional, fiber optic coupler operative to receive from an optical fiber, modulated light for detection thereof, and for applying to the same fiber, modulated light for transmission to a remote location. The coupler comprises a body which can be conveniently and economically molded as a unitary plastic element and in which a V-channel is formed to receive and securely hold the optical fiber. The channel terminates in a slanted reflecting face which is readily coated with a dielectric layer to provide a beam splitting function, or in the case of dual frequency transmissions, a frequency dependent layer to provide multiplexing or demultiplexing. The slanted reflecting face is located at the bottom of an emitter cavity in which an emitter assembly is readily press-fit to provide predetermined alignment between light emanating from the emitter assembly and the reflecting face from which the light is reflected into the adjacent termination of the optical fiber. A detector cavity is formed within the body and positioned to receive light passing through the reflecting face. The transiting light is refracted downward toward the detector cavity which is positioned off axis. An index of refraction matching material may be applied between the optical fiber and reflecting face in which case the reflecting face passes the incoming light directly along the axis. A portion of the transmitted light is totally internally reflected by the bottom surface of the emitter cavity which is formed to provide a mirror surface that redirects that light toward the detector cavity. A lens may be molded directly into the coupler body to gather light passing through and refracted by the reflecting face. For the portion of light generated by the emitter and passing through the reflective face, a reflective wedge is provided in the bottom of the coupler body to direct that radiation away from the detector to reduce cross talk.