OPTICAL FIBER

摘要

An optical fiber has a structure for suppressing the occurrence of a nonline ar phenomenon effectively while not increasing the transmission losses such as the bending loss. The optical fiber has a central region having a predetermined refractive index, a first annular region having a refractive index higher than that of the central region and a second annular region whi ch is doped with fluorine and has a refractive index lower than that of the fir st annular region in this order from the central axis in the radial direction. Particularly, the optical fiber has an effective cross-sectional area of mor e than 70 .mu.m2 for a light with a wavelength of 1550 nm, and the dosage of fluorine is so adjusted that the refractive index of the region lowers in th e radial direction from the center of the optical fiber.