An optical fiber includes a glass portion, a primary coating layer, and a secondary coating layer. In the optical fiber, a value of microbend loss characteristic factor F.sub.μBL_GO is 2.6 ([GPa.sup.−1.Math.μm.sup.−10.5.Math.dB/turn].Math.10.sup.−27) or less, when represented by
F.sub.μBL_GO=F.sub.μBL_G×F.sub.μBL_O
by using geometry microbend loss characteristic F.sub.μBL_G and optical microbend loss characteristic F.sub.μBL_O.

A microstructured optical fiber for generating supercontinuum light. The optical fiber includes a core and a cladding region surrounding the core. The optical fiber includes a first fiber length section, a second fiber length section as well as an intermediate fiber length section between said first and second fiber length sections. The first fiber length section has a core with a first characteristic core diameter larger than about 7 μm. The second fiber length section has a core with a second characteristic core diameter, smaller than said first characteristic core diameter. The intermediate length section of the optical fiber includes a core which is tapered from said first characteristic core diameter to the second characteristic core diameter over a tapered length. Also, a supercontinuum light source including an optical fiber and a pump light source.

A low-dispersion single-mode optical fiber includes a core and a cladding covering the core. The core has a relative refractive index difference of 0.30-0.65% and a radius of 2.5-4.5 μm. The cladding layer including first, second, third cladding layers and an outer cladding arranged sequentially from inside to outside. The first cladding layer covers the core, and has a relative refractive index difference of −0.70% to −0.30% and a radius of 4.5-7.5 μm. The second cladding layer covers the first cladding layer, and has a relative refractive index difference of −0.20% to 0.25% and a radius of 7.0-12.0 μm. The third cladding layer covers the second cladding layer, and has a relative refractive index difference of −0.60% to 0.00% and a radius of 10.0-20.0 μm. The outer cladding covers the third cladding layer, and is a layer made of pure silicon dioxide glass.

An optical fiber includes a glass portion, a primary coating layer, and a secondary coating layer. In the optical fiber, a value of microbend loss characteristic factor F.sub.μBL_GO is 2.6 ([GPa.sup.−1.Math.μm.sup.−10.5.Math.dB/turn].Math.10.sup.−27) or less, when represented by

F.sub.μBL_GO=F.sub.μBL_G×F.sub.μBL_O

by using geometry microbend loss characteristic F.sub.μBL_G and optical microbend loss characteristic F.sub.μBL_O.

An optical fiber includes: a core portion made of glass; and a cladding portion made of glass, having a refractive index lower than the refractive index of the core portion, and positioned on an outer periphery of the core portion. Further, the cladding portion has an outer diameter smaller than 100 μm, and the core portion has a relative refractive-index difference of 0.32% to 0.40% with respect to the cladding portion.

An optical fiber includes a glass portion, a primary coating layer, and a secondary coating layer. In the optical fiber, a value of microbend loss characteristic factor F.sub.μBL_GΔβ is 6.1 ([GPa.sup.−1.Math.μm.sup.−2.5/rad.sup.8].Math.10.sup.−12) or less when represented by

F.sub.μBL_GΔβ=F.sub.μBL_G×F.sub.μBL_Δβ,

where F.sub.μBL_G is geometry microbend loss characteristic and F.sub.μBL_Δβ is optical microbend loss characteristic.

A wavelength multiplexing system is presented comprising at least one basic functional unit extending between input and output light ports. The basic functional unit comprises at least one multi-core fiber. The multi-core fiber comprises N cores configured for supporting transmission of N wavelength channels λ.sub.1, . . . , λ.sub.n, wherein each of said at least one multi-core fibers is configured to apply a predetermined encoding pattern to the wavelength channels enabling linear mixing between them while propagating through multiple cores of said multi-core fiber. The encoding pattern may be configured to affect light propagation paths in the cores by inducing a predetermined dispersion pattern causing linear interaction and mixing between the channels; or may be configured to affect spectral encoding of the channels being transmitted through the cores by applying different weights to the channels.

A low-dispersion single-mode optical fiber includes a core and claddings covering the core. The core has a relative refractive index difference of 0.30-0.65% and a radius of 2.5-4.5 μm. The claddings include first, second, third cladding layers and an outer cladding arranged sequentially from inside to outside. The first cladding layer covers the core, and has a relative refractive index difference of −0.70% to −0.30% and a radius of 4.5-7.5 μm. The second cladding layer covers the first cladding layer, and has a relative refractive index difference of −0.20% to −0.25% and a radius of 7.0-12.0 μm. The third cladding layer covers the second cladding layer, and has a relative refractive index difference of −0.60% to 0.00% and a radius of 10.0-20.0 μm. The outer cladding covers the third cladding layer, and is a layer made of pure silicon dioxide glass.

T/C, which is a ratio of an area T of a skirt part outside the boundary to an area C of the core region in a refractive index distribution, is 4% or more and 30% or less, the boundary is defined at a position where an absolute value of a change amount of the index becomes maximum between the center of the core region and the outer peripheral part of the first clad region, the area C of the core region is defined in a range from the center of the core region to the boundary in the radial direction, the area T of the skirt part is defined in a range from the boundary to the outer peripheral part of the first clad region.

An optical fiber comprising: a core having an outer radius r.sub.1; a cladding having an outer radius r.sub.4≤31 microns; a primary coating surrounding the cladding having an outer radius r.sub.5, a thickness t.sub.p>10 microns, in situ modulus E.sub.P of 0.5 MPa or less, and a spring constant χ.sub.P<1 MPa, where χ.sub.P=2E.sub.P r.sub.4/t.sub.P; and a secondary coating surrounding said primary coating, the secondary coating having an outer radius r.sub.6, a thickness t.sub.S=r.sub.6-r.sub.5, in situ modulus E.sub.S of 1200 MPa or greater; t.sub.S greater than 9.5 microns, wherein r.sub.6 is 50 to 67.5 microns. The fiber has a mode field diameter MFD greater than 8.2 microns at 1310 nm; a fiber cutoff wavelength of less than 1310 nm; and a bend loss at a wavelength of 1550 nm, when wrapped around a mandrel having a diameter of 10 mm, of less than 1.0 dB/turn.