An optical fiber is formed from silica-based glass. The optical fiber includes a core including a central axis and a cladding surrounding the core. A refractive index of the core is greater than a refractive index of the cladding. The core contains chlorine, and one or more kinds of elements selected from an element group consisting of alkali metal elements and alkaline earth metal elements. A relative refractive index difference of the core based on a refractive index of pure silica is 0.00% or greater and 0.15% or less. An average concentration of fluorine in the cladding is 1.2% or less in a mass fraction.

A method for manufacturing an optical fiber preform made of silica-based glass, the method including: forming a core portion; and forming a cladding portion surrounding the core portion, the cladding portion having a refractive index lower than a refractive index of the core portion, wherein the forming the core portion includes: adding an alkali element group consisting of an alkali metal element and an alkaline earth metal element to an inner surface of a glass pipe made of silica-based glass; and integrating the glass pipe and a glass rod disposed inside the glass pipe to form an integrated rod after the adding.

A method of producing an optical fiber preform includes a silica glass body forming step of forming a silica glass body to be at least a portion of a core portion. The method includes an alkali-metal-doped silica glass body forming step of forming an alkali-metal-doped silica glass body doped with an alkali metal around the silica glass body such that the alkali-metal-doped silica glass body contacts the silica glass body. The method further includes a diffusing step of diffusing the alkali metal from the alkali-metal-doped silica glass body to the silica glass body by a heat treatment.

The present application provides a process of fabrication of erbium and ytterbium-co-doped multielements silica glass based cladding-pumped fiber for use as a highly efficient high power optical amplifier.

A method of preparing an optical preform, comprises the steps of: positioning an optical preform comprising silica within a cavity of a furnace; passing an etchant gas into the furnace and at least one of through an open channel defined in the optical preform and around the optical preform; and passing a neutralizing gas into the cavity of the furnace, the neutralizing gas configured to neutralize the etchant gas.

A manufacturing method of an optical fiber preform used to produce an optical fiber includes: etching a surface of a core preform that forms a core of the optical fiber with a plasma flame in a chamber; obtaining a porous preform by depositing glass particles on an etched surface of the core preform to form an outside vapor-deposited layer that forms a cladding of the optical fiber in a state where the core preform is put into the chamber; and heating and sintering the porous preform. When obtaining the porous preform, the outside vapor-deposited layer is formed by repeatedly performing the deposition of the glass particles multiple times through supply of source material gas. In a first deposition among the multiple times of deposition of the glass particles, a flow rate of the source material gas is less than or equal to 50% of a stable value.

The present embodiment relates to an optical fiber preform producing method for effectively suppressing breaking of symmetry of refractive index profile defined on a cross section of an optical fiber preform. In the present embodiment, when producing a center glass rod forming a part of the optical fiber preform, prior to grinding an outer peripheral portion of an intermediate glass rod in which an element-doped region is formed by collapse, an non-defective article determination regarding the intermediate glass rod to be a grinding target is performed.

The present embodiment relates to an optical fiber preform producing method for effectively suppressing breaking of symmetry of refractive index profile defined on a cross section of an optical fiber preform. In the present embodiment, when producing a center glass rod forming a part of the optical fiber preform, prior to grinding an outer peripheral portion of an intermediate glass rod in which an element-doped region is formed by collapse, an non-defective article determination regarding the intermediate glass rod to be a grinding target is performed.

A rare earth-doped double-clad optical fiber includes a rare earth ion-doped fiber core, an inner cladding layer, and an outer cladding layer. A cross section of the inner cladding layer is a non-circular plane including at least two arcuate notches. According to the provided optical fiber, optical processing can be performed on a preform without changing a preform preparation process and a drawing process. The inner cladding is designed to have a non-circular planar structure having a cross section with at least two arcuate notches. While maintaining the same light absorption efficiency of pump light within the cladding layer, a preform polishing process is simplified, a risk of cracking the preform during polishing of multiple surfaces and a risk of contamination of the preform caused by impurities are reduced, wire drawing control precision is better, and comprehensive performance of the optical fiber is improved.

There is provided a method of manufacturing a cutting element for use in a hair cutting device, the cutting element comprising an optical waveguide, the method comprising providing a preform for an optical waveguide, the preform comprising a core and an outer layer, wherein the outer layer is arranged around the core along the length of the core; forming a shaped preform by removing a portion of the outer layer along the length of the core to expose part of the core, wherein a remaining portion of the outer layer is a support structure for the core; heating the shaped preform; and pulling the shaped preform in the direction of the axis of the core to reduce the cross-section of the shaped preform and form the optical waveguide. Also provided is a cutting element manufactured according to the above method and a cutting element for use in a hair cutting device, the cutting element comprising an optical waveguide comprising a core and a support structure, wherein the support structure contacts the core along the length of the core to support the core, and wherein part of the core is exposed along the length of the core to form a cutting face for contacting hair. The thickness of the support structure tapers linearly or non-linearly from a thin side at which the support structure contacts the core to a thick side.