Abstract: In an optical fiber having a core region and a cladding region, surrounding the core region, comprising a main medium having different refractive indices from the main medium and spaced apart in the main medium, the core region comprises a central core region having a hollow portion disposed at the center of the core region and an outer core region surrounding the central core region having a mean refractive index higher than the central core region, and the core region has a higher mean refractive index than the cladding region.

Abstract: In an optical fiber comprising a core region, an inner cladding region, and an outer cladding region which extend along its fiber axis, the average refractive index n0 of core region, the average refractive index n1 of inner cladding region, and the average refractive index n2 of outer cladding region satisfying the relationship of n1<n2<n0; at least three microstructures each extending along the fiber axis and comprising an auxiliary medium having a refractive index different from that of a main medium constituting the inner cladding region are included in the inner cladding region.

Abstract: An optical fiber has a core region and a cladding region surrounding the core region. The core region and the cladding region are made of a base material containing silica glass as a principal component. A plurality of holes extending along an axial direction are arranged at least in the cladding region. In the optical fiber, the base material has a hydroxyl mole fraction of not less than 10 ppm, or a fluorine content of not less than 0.2% by weight.

Abstract: The present invention provides an optical fiber which has a hollow portion extending along the axis and which reduces degradation of the optical characteristics, and a production method thereof. An optical fiber includes a hollow core portion, and a cladding portion which surrounds the hollow core portion. The refractive index of the hollow core portion is lower than that of the cladding portion. The hollow core portion is closed at both ends of the optical fiber so as to form sealed portions. The sealed portions are formed by, for example, heating the optical fiber and softening the cladding portion. This prevents foreign material and the like from entering the hollow core portion. Ferrules of optical connectors are attached to both end faces of the optical fiber.

Abstract: Provided is an optical fiber having holes extending along the axis whose transmission loss is substantially reduced and the manufacturing method thereof. First, a plurality of through-holes 9 are formed in a preform 5 extending along the preform axis. Subsequently, the preform 5 is heated by heating means 24 in the furnace preferably for 30 minutes or more at a temperature equal to or more than 800° C. while flowing a dry gas in the through-holes 9. As a result, the OH group which exists on the surfaces of the inner walls 5a of the through-holes 9 of the preform 5 is discharged outside the preform. Subsequently, the preform 5 is drawn into an optical fiber.

Abstract: Provided are an optical transmission line including a connected part of the optical fibers having different refractive index profiles, wherein at least one of the optical fibers has a hollow region, and a method for connecting such optical fibers, wherein connection loss in a connection of such optical fibers is reduced. In the case of connecting an optical fiber 1, which does not have a hollow region and which consists of a core region 3 and a cladding region 4, and an optical fiber 2, which consists of a hollow core region 5 and a cladding region 6 having a plurality of refractive index variation parts 7 which extend along optical fiber 2, matching oil M is first injected into the connecting end portion of the hollow core region 5 to be connected with the optical fiber 1.

Abstract: In an optical fiber having a core region and a cladding region which surrounds the core region, wherein a plurality of regions made of sub mediums having refractive index different from that of the main medium constituting the cladding region are spaced apart in cross section of the cladding region and the mean refractive index of the core region is lower than that of the cladding region, the sub-medium regions are regularly arranged in the radial direction of said optical fiber such that the light having given wavelength, propagation coefficient and electric field distribution propagates along the fiber axis and has not less than 50% of a total propagating power in the core region, and this arrangement does not have translational symmetry in cross section.

Abstract: In an optical fiber including a core region and cladding regions of not less than three layers which surround the core region in order, at least one of the cladding regions has lower mean refractive index than both adjacent regions, and at least one cladding region is provided with a plurality of sub medium regions each having a refractive index lower than a main medium constituting this cladding region.

Abstract: An optical fiber has a section of the first kind having a chromatic dispersion not less than a given positive value x and a negative chromatic dispersion slope at a given wavelength and a section of the second kind has a chromatic dispersion not more than −x and a positive chromatic dispersion slope at the same wavelength. Another optical fiber has a chromatic dispersion higher than a positive value x and a negative chromatic dispersion slope at a given wavelength band.

Abstract: In an optical fiber including a core region and a cladding region surrounding said core region in a cross section and having a cross-sectional structure in which a plurality of regions constituted by sub mediums are arranged in main mediums, at least one of refractive indices of the main mediums and the sub mediums are changed in a radial direction.

Abstract: In an optical fiber composed of a core region and a cladding region surrounding the core region and having a plurality of regions made of sub mediums having refractive indices different from a refractive index of a main medium disposed in a main medium constituting this cladding region, these regions made of the sub mediums are arranged in one given or a plurality of a given circular annular regions and the centers of the regions made of the sub mediums in respective circular annular regions are arranged on the same circumference centered at the center of the core.

Abstract: In an optical fiber having a core region and a cladding region, surrounding the core region, comprising a main medium and sub mediums having different optical characteristics from the main medium and spaced apart in the main medium, the core region comprises a central core region having a hollow portion disposed at the center of the core region and an outer core region surrounding the central core region having a mean refractive index higher than the central core region, and the core region has a higher mean refractive index than the cladding region.