Multicore optical fiber

Abstract

A multicore optical fiber is made of silica-based glass. The multicore optical fiber includes a plurality of cores containing one or more kinds of elements among an alkali metal element group consisting of an alkali metal element and alkaline-earth metal element, and a cladding that surrounds the plurality of cores, and has a refractive index lower than a refractive index of the plurality of cores. All adjacent first cores and second cores among the plurality of cores have refractive indexes different from each other. A difference between a maximum value and a minimum value of a transmission loss of the plurality of cores at a wavelength of 1550 nm is 0.005 dB/km or less.

Dependencies are inferred from the claim text.