Low-loss single-mode fibers with different B(2)O(3)-SiO(2) compositions

Design considerations, fabrication, and transmission characteristics of single-mode optical fibers made with different borosilicate compositions are discussed. Fibers with core sizes as large as 15 microm and refractive-index differences below 0.1% were made with the modified chemical vapor deposition (MCVD) process. Minimum losses achieved with fibers up to 1-km lengths were 1.3-1.4 dB/km in the 1.02-1.1-microm range. Microbending losses were avoided by jacketing the fibers with silicone resin. Single-mode operation is maintained in moderately overmoded fibers (V ~ 3.0) because of leakage loss through a finite cladding thickness and because of bends in the fiber axis.