Permanent Multiple Splices of Fused-Silica Fibers

Recently, several techniques for connecting both multimode and single-mode fibers have been developed. 1-5 The problems associated with obtaining good optical ends of the fibers to be spliced have also been the subject of a recent work. 6 These efforts have been motivated by the fact that, for optical communications to become a reality, permanent low-loss splices of fibers must be achieved. In this paper, a method of permanently joining single and multiple pairs of fibers is described. The method used is summarized here, and a complete description of the technique and results is given in the following sections. It should be noted that the results reported for single bonds were obtained with eight splices and for the multiple bonds with 30-fiber pairs. In brief, coupling efficiency is over 95 percent, and the strength of a joint does not fail until a force of over 300 grams is applied to the end of the fiber. The fiber breaks at a force of approximately 450 grams. Alignment of the fibers is achieved by feeding the fiber into flared tunnels over a fused-silica substrate and is easily done by hand. 4 After the fibers are aligned, an aluminum washer yg-inch in diameter is placed against the aligned fibers. The washer is centered so that the splice is in the open center of the washer. The washer is then compressed against the aligned fibers so that the aluminum yields around a portion of each fiber. The pressure required is below the breaking strength range of the fiber, and the aluminum is 451