An optical fiber is formed from silica glass, and includes a core, a first cladding which surrounds the core and has a refractive index lower than the refractive index of the core, and a second cladding which surrounds the first cladding and has a refractive index that is lower than the refractive index of the core and higher than the refractive index of the first cladding. The second cladding is divided into an inner region that is in contact with the first cladding and an outer region which surrounds the inner region and has a thickness that is half the thickness of the second cladding or less, while being 5 μm or more. The residual stress in at least a part of the outer region is a compressive stress.

An optical fiber comprising: a core having an outer radius r.sub.1; a cladding having an outer radius r.sub.4<45 microns; a primary coating surrounding the cladding and having an outer radius r.sub.5 and a thickness t.sub.p>8 microns, the primary coating having in situ modulus E.sub.P of 0.35 MPa or less and a spring constant χ.sub.P<1.6 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, wherein >10 microns and r.sub.6≤85 microns. The fiber has a mode field diameter MFD greater than 8.2 microns at 1310 nm; a 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.

A method of processing by controlling one or more beam characteristics of an optical beam may include: launching the optical beam into a first length of fiber having a first refractive-index profile (RIP); coupling the optical beam from the first length of fiber into a second length of fiber having a second RIP and one or more confinement regions; modifying the one or more beam characteristics of the optical beam in the first length of fiber, in the second length of fiber, or in the first and second lengths of fiber; confining the modified one or more beam characteristics of the optical beam within the one or more confinement regions of the second length of fiber; and/or generating an output beam, having the modified one or more beam characteristics of the optical beam, from the second length of fiber. The first RIP may differ from the second RIP.

One described aspect is an optical fiber comprising: a fiber core that extends along a fiber axis, is configured to transmit a laser energy along the fiber axis, and terminates at a distal end; a first cladding that extends along the fiber axis, is adjacent to the fiber core, and terminates at a distal end; a coating that extends along the fiber axis and terminates at a distal end, wherein the coating is a gold coating; a second cladding that surrounds a portion of the gold coating along the fiber axis, and terminates at a distal end; an outer jacket that extends along the fiber axis and terminates at a distal end; and a fiber tip. Associated laser systems are also disclosed.

An optical fibre includes a glass core defined by a central core region surrounded by an outer core region. The glass core has a core thickness of 3.5 to 6 micrometers. The central core region has a centerline dip. The central dip has a centerline width in range of about 0 to 3 micrometers. The outer core region has a core alpha in a range of 3-8. The optical fibre includes a buffer clad region, a trench region and an outer cladding region. The outer cladding region has at least one of an outer cladding thickness in range of 41.5 to 46.5 micrometers and an outer cladding relative refractive index near zero.

One embodiment of the present disclosure relates to an optical fiber having lower transmission loss. The optical fiber is an optical fiber comprised of silica-based glass and includes a core including a central axis and a cladding. The cladding surrounds the core and has a refractive index lower than a refractive index of the core. The core contains phosphorus, chlorine, and fluorine. The core further includes an alkali metal element or an alkaline earth metal element. In a cross section of the optical fiber orthogonal to the central axis, a ratio Rp/Ra of a radius Rp of a phosphorus-containing region with respect to a radius Ra of the core is 0.3 or more.

A manufacturing method for an optical fiber, includes: drawing, while heating in a heating furnace, a lower end of an optical fiber preform that is to be an optical fiber having a core consisting of silica glass containing a rare earth element compound. The heating furnace has a temperature profile in which a temperature of the heating furnace increases to a maximum temperature T.sub.max and then decreases from an upstream side of the heating furnace toward a downstream side of the heating furnace. The temperature profile has a changing point at which the temperature decreases more steeply on the downstream side from a position where the maximum temperature T.sub.max is reached. At the maximum temperature, a temperature of the silica glass is higher than or equal to a glass transition temperature and the silica glass is in a single phase.

A method of manufacturing an optical fiber is provided. The method involves providing a fiber preform with an active core and a pump-guiding cladding, and assembling one or more side rods to the fiber preform. The side rods extend longitudinally along an outer surface of the pump-guiding cladding. The resulting fiber preform assembly is drawn into the optical fiber. Each side rod defines a longitudinal protrusion extending along the optical fiber. Each longitudinal protrusion may have a cross-section forming a middle bump projecting radially away from the outer surface of the pump-guiding cladding and smooth transition regions with this outer surface of the pump-guiding cladding on opposite sides of the middle bump.

The optical fiber offered is capable of not only restraining the attenuation due to glass defects, but also reducing the increase of manufacturing cost. The optical fiber is made of silica glass and includes a core and a cladding. The cladding encloses the core and has a refractive index smaller than that of the core. When the core is divided into inner core and outer core at half of the radius of the core, the average chlorine concentration of the inner core is larger than that of the outer core. The core includes any of the alkali metal group.

The present disclosure relates to a process by which an optical fiber is terminated with a ferrule to form an optical fiber connector assembly. The ferrule is heated at a heating temperature whereby the ferrule bore (and ferrule microhole) expands. The optical fiber is then inserted into the ferrule microhole. The ferrule then contracts when heat is no longer applied resulting in an interference fit between the optical fiber and the ferrule microhole based on the dimensions of the optical fiber and the ferrule microhole. The interference fit yields certain optical fiber characteristics within the optical fiber connector assembly. The present disclosure also relates to an optical fiber having an outer cladding comprising titania-doped silica and the resulting optical fiber characteristics.