Optical fiber
An optical fiber includes: a core portion; a side core layer circumferentially surrounding the core portion; a cladding portion circumferentially surrounding the side core layer; and a coating layer circumferentially surrounding the cladding portion. When an average maximum relative refractive-index difference of the core portion to an average refractive index of the cladding portion is Δ 1 , a relative refractive-index difference of an average refractive index of the side core layer to the average refractive index of the cladding portion is Δ 2 , a relative refractive-index difference of the average refractive index of the cladding portion to pure silica glass is ΔClad, Δ 1 >ΔClad>Δ 2 and 0>Δ 2 hold, the Δ 1 is 0.18% or more and 0.24% or less, the Δ 2 is −0.27% or more and −0.12% or less, and (Δ 1−Δ2 ) is 0.36% or more and 0.45% or less.
1 . An optical fiber comprising:
a core portion;
a side core layer circumferentially surrounding the core portion;
a cladding portion circumferentially surrounding the side core layer; and
a coating layer circumferentially surrounding the cladding portion, wherein
when an average maximum relative refractive-index difference of the core portion to an average refractive index of the cladding portion is Δ 1 , a relative refractive-index difference of an average refractive index of the side core layer to the average refractive index of the cladding portion is Δ 2 , a relative refractive-index difference of the average refractive index of the cladding portion to pure silica glass is ΔClad, Δ 1 >ΔClad>Δ 2 and 0>Δ 2 hold,
the Δ 1 is 0.18% or more and 0.24% or less,
the Δ 2 is −0.27% or more and −0.12% or less,
(Δ 1 −Δ 2 ) is 0.36% or more and 0.45% or less,
when a core diameter of the core portion is 2 a and an outer diameter of the side core layer is 2 b , b/a is 2.5 or more and 5 or less,
an effective core area at a wavelength of 1550 nm is 105 μm 2 or more and 130 μm 2 or less,
a cable cut-off wavelength is 1530 nm or less, and
a macrobending loss at a wavelength of 1550 nm when bent at a diameter of 30 mm is 1 dB/m or less.
2 . The optical fiber according to claim 1 , wherein
the b/a is 3.9 or less.
3 . The optical fiber according to claim 1 , wherein
the cable cut-off wavelength is 1500 nm or less.
4 . The optical fiber according to claim 1 , wherein
a transmission loss at a wavelength of 1550 nm is 0.18 dB/km or less.
5 . The optical fiber according to claim 1 , wherein
the ΔClad has a negative value.
6 . The optical fiber according to claim 1 , wherein
the core portion does not include germanium.
7 . The optical fiber according to claim 1 , wherein
a microbending loss at a wavelength of 1550 nm measured by a sandpaper method is 1.0 dB/km or less.
8 . The optical fiber according to claim 1 , wherein
the 2 a is 12 μm or more and 13.9 μm or less.
9 . The optical fiber according to claim 1 , wherein
the Δ 2 is −0.14% or less.
10 . The optical fiber according to claim 1 , wherein
the Δ 1 is 0.19%≤Δ 1 ≤0.24%.
11 . The optical fiber according to claim 1 , wherein
a transmission loss at a wavelength of 1550 nm is 0.165 dB/km or less.