Patent ID: 9739935
Date: 2017-08-22
CPC Classifications: C03B,G02B

Claim:
1. An optical fiber, comprising: a core; and a clad surrounding an outer circumference of the core, the clad comprising an inner cladding layer adjacent to the outer circumference of the core and an outer cladding layer formed on an outer circumference of the inner cladding layer, wherein when a radius of the core is r1, a relative refractive index difference between a center of the core and the clad is a first relative refractive index difference Δ1a, and a relative refractive index difference between a position in which a distance from the center of the core in a radial direction is r1 and the clad is a second relative refractive index difference Δ1b, the first relative refractive index difference Δ1a is greater than 0, the second relative refractive index difference Δ1b is greater than 0, the first relative refractive index difference Δ1a is greater than the second relative refractive index difference Δ1b, the first relative refractive index difference Δ1a and the second relative refractive index difference Δ1b satisfy a relationship denoted by the following expression: a refractive index profile Δ of the core in an entire region of a section of 0≦r≦r1 as a function Δ(r) of a distance r from the center of the core in the radial direction is denoted by the following expression: when a minimum refractive index of the inner cladding layer is Δ2min and a refractive index of the outer cladding layer is Δ3, the minimum refractive index of the inner cladding layer Δ2min and the refractive index of the outer cladding layer Δ3 satisfy a relationship denoted by the following expression: a ratio r1/r2 of the radius r1 of the core to a radius r2 of the inner cladding layer is in a range denoted by the following expression: