Simple, Low-Loss Joints Between Single-Mode Optical Fibers

Recently, several authors have dealt with techniques for making low-loss joints between multimode 1 - 4 or single-mode 5 optical fibers. For long-distance communication channels, joints between fiber cables, simply assembled in the field, would be very valuable. The joints that were made so far with the technique described in this paper connected just one pair of fibers at a time. However, this is intended to be the first step in the development of joints between multifiber cables. Therefore, in the present experiments emphasis has been put on getting repetitive results which are not a consequence of careful laboratory adjustment. This is an important difference with respect to the methods that gave the best results reported so far. 1,5 Nonetheless, the joints between single-mode fibers described here compare favorably with previous ones as far as the losses are concerned. The demonstration with single-mode fibers (core diameters of ~ 4 ^m) means that the technique applies also to multimode fibers, the larger core diameters of which should make the alignment less critical. * This work was performed at Bell Telephone Laboratories, Incorporated, Crawford Hill Laboratory, Holmdel, New Jersey, during a six-month internship sponsored by a N A T O - C N R fellowship. 583