OPTICAL FIBER, OPTICAL FIBER LASER, OPTICAL FIBER AMPLIFIER, AND METHOD FOR PRODUCING OPTICAL FIBER

摘要

An optical fiber which is provided with: a core portion that is formed of silica glass to which a rare earth element and aluminum are added; an inner cladding layer that is formed on the outer circumference of the core portion and formed of silica glass to which an alkali metal and/or an alkaline earth metal is added, while having a refractive index lower than that of the core portion; and an outer cladding layer that is formed on the outer circumference of the inner cladding layer and has a refractive index lower than that of the inner cladding layer. Consequently, desired optical characteristics can be achieved with high productivity.