Optical fiber light tap

摘要

An optical fiber tap is described which comprises a beamsplitter formed by positioning bevelled, parallel endfaces of two segments of optical fiber in coaxial alignment and in close proximity to each other. A suitable dielectric film, such as air, fills the gap between the endfaces. Light propagating into the tap from the first fiber segment is partially reflected and partially refracted at the bevelled endfaces. The refracted portion enters the second fiber segment and the reflected portion leaves the tap and is detected by a photodetector. By choice of the proper angle for the bevelled endfaces, the tap can be made substantially mode independent. A greater degree of mode independence can be obtained by interposing a steady-state mode exciter between the light source and the beamsplitter. The tap is particularly useful for semiconductor junction laser stabilization by the feedback arrangement described herein since the ratio of the intensity of the reflected portion to that of the refracted portion is substantially constant. A package assembly for use in the feedback arrangement is also described.