Simple, low-loss joints between single-mode optical fibers

Low-loss joints between single-mode optical fibers have been made without microscopic alignment, without fusing the tips, and without monitoring the transmitted power while the joints are assembled. The fibers are tightly held in an embossed groove; an index-matching liquid is added. Average power coupling efficiencies close to 90 percent in the red and to 85 percent in the infrared have been obtained. Mediocre end faces are acceptable. Realistic discrepancies between the fiber cladding diameters (slightly in excess of twice the core diameter) do not deteriorate the results.