Monolithic fiber optic coupler having total internal reflecting surface

Abstract

A coupler for light between the termination of an optical fiber and one or more detector or emitter elements in which the optical path between the termination and the detectors and emitters includes one or more focussing surfaces. The coupler is designed as a molded plastic body adapted to precisely position the optical fiber termination and the emitters and detectors so that the optical path between them via the focussing surfaces couples light efficiently. The focussing surfaces are molded into the coupler during manufacture and are preferably angled to the radiation to provide total internal reflection, avoiding reflective coatings. In the case where the focussing surfaces are reflecting, they are preferably ellipsoidal or paraboloidal in shape. In a second case, one surface is beam splitting and a second surface provides focussed reflection. In another case one focussing surface is reflecting while a second focussing surface is refracting. The coupler permits the realization of various features including precise alignment between the fiber, emitters and detectors; physically separated surfaces; cross-talk elimination; insensitivity to variations in radiation wavelength, index of refraction and dimensions of the coupler; aberration correction; ease of molding without side actions in the mold; and design flexibility in the placement of the focussing surfaces.