OPTICAL FIBER TRANSMISSION LINE

摘要

The present invention relates to an optical fiber transmission line having a structure offering superior connection loss characteristics at the fusion-spliced position between optical fibers. This optical fiber transmission line has at least first and second optical fibers that are fusion-spliced. Each of these first and second optical fibers has a core region doped with 10 mol% or more of Ge and, has a mode field diameter with a minimum value of 7 .mu.m or less at the wavelength of 1550 nm. The difference between the minimum mode diameter of the first optical fiber and that of the second optical fiber is 1 .mu.m or less. In particular, in this optical fiber transmission line, the mode field diameter of the first optical fiber, at a position separated by at least 2 mm from the fusion-spliced positron between the first and second optical fibers, is enlarged so as to reach a value of 110% or more of the minimum mode field diameter of the first optical fiber, and the mode field diameter of the second optical fiber, at a position separated by at least 2 mm from the fusion-spliced position between the first and second optical fibers, is enlarged so as to reach a value of 110% or more of the minimum mode field diameter of the second optical fiber.