A preform element, its production, and fiber production methods from preform assemblies. The preform element has a length and a center axis along its length, a first and second end defined by its length and an outer preform element surface. The preform element includes a plurality of longitudinal structures disposed to form longitudinal hole(s) in a background material. At least one slot extending from its outer preform element surface and intersecting at least one of the longitudinal holes, wherein the at least one slot does not fully intersect the preform element. The preform element may be a preform center element or a preform ring element and may be assembled to a form part of a preform assembly for an optical fiber.

A method of producing a microstructured optical fiber is disclosed. The method includes providing a preform and drawing the preform. The preform has a center axis, a length and a first end and a second end and has at least one longitudinal hole extending lengthwise. The method includes inserting a first end of a pressure tube into the hole of the preform at the first end of the preform and subjecting the hole of the preform to a controlled pressure via the pressure tube during the drawing.

A hollow core fiber has a cladding comprising a matrix of cells, wherein each cell comprises a hole and a wall surrounding the hole. The fiber further has a hollow core region comprising a core gap in the matrix of cells, wherein the core gap spans a plurality of cells and has a boundary defined by the interface of the core gap. The matrix of cells comprises a plurality of lattice cells, and a plurality of defect cells characterised by at least one difference in at least one property from that of the lattice cells. The cells at the core region boundary include lattice cells and defect cells that are arranged in a pattern so as to produce birefringence in a light propagating through the hollow core fiber. Further described is a technique for making the fiber.

A method of producing a microstructured optical fiber is disclosed. The method includes providing a preform and drawing the preform. The preform has a center axis, a length and a first end and a second end and has at least one longitudinal hole extending lengthwise. The method includes inserting a first end of a pressure tube into the hole of the preform at the first end of the preform and subjecting the hole of the preform to a controlled pressure via the pressure tube during the drawing.

A method of forming an optical fiber, the method including heating a forming region of the optical fiber preform within a pressure device while exposing the forming region to a total pressure of about 500 atm or greater, directing the optical fiber preform in a downstream direction along a process pathway to form the optical fiber, and traversing the optical fiber through an aperture of a nozzle to maintain the total pressure of about 500 atm or greater within the pressure device.

A hollow core fiber has a cladding comprising a matrix of cells, wherein each cell comprises a hole and a wall surrounding the hole. The fiber further has a hollow core region comprising a core gap in the matrix of cells, wherein the core gap spans a plurality of cells and has a boundary defined by the interface of the core gap. The matrix of cells comprises a plurality of lattice cells, and a plurality of defect cells characterised by at least one difference in at least one property from that of the lattice cells. The cells at the core region boundary include lattice cells and defect cells that are arranged in a pattern so as to produce birefringence in a light propagating through the hollow core fiber. Further described is a technique for making the fiber.

A hollow core fiber has a cladding comprising a matrix of cells, wherein each cell comprises a hole and a wall surrounding the hole. The fiber further has a hollow core region comprising a core gap in the matrix of cells, wherein the core gap spans a plurality of cells and has a boundary defined by the interface of the core gap. The matrix of cells comprises a plurality of lattice cells, and a plurality of defect cells characterized by at least one difference in at least one property from that of the lattice cells. The cells at the core region boundary include lattice cells and defect cells that are arranged in a pattern that define two orthogonal axes of reflection symmetry, so as to produce birefringence in a light propagating through the hollow core fiber.

The disclosure relates to an integrated hollow-core optical fiber preform, an optical fiber and a fabrication method thereof. Initially, holes are drilled to obtain a preform which is then subjected to a drawing process with gas fed into the drilled holes for pressurization control, resulting in an optical fiber with an anti-resonant ring structure. This method employs mechanical drilling to achieve precise positioning of the azimuth angle of the anti-resonant unit, ensuring axial uniformity and preventing any azimuthal shift during the drawing process. Furthermore, no additional materials are introduced for positioning the anti-resonant unit, thereby minimizing contamination from impurities and enhancing properties such as attenuation and strength of the optical fiber. Additionally, gas pressure control expands the anti-resonant unit during the drawing process, reducing its wall thickness and consequently lowering attenuation in this hollow-core optical fiber.

A method of manufacturing an optical fiber with a hole from a preform having a through hole is disclosed. The manufacturing method includes placing a preform in a drawing furnace, forming an optical fiber by melting and drawing the preform in the drawing furnace while a gas is introduced into the through hole, capturing an image of the optical fiber drawn from the preform, and measuring a hole diameter of the optical fiber based on an image captured in the capturing of the image and controlling a pressure of the gas introduced into the through hole based on a measurement result. In the capturing of the image, when the optical fiber deviates, a predetermined countermeasure is taken to make the image clear, and the image is maintained in a clear state.

An optical fiber manufacturing method includes: a drawing step of heating one end portion of an optical fiber preform to melt and deform the one end portion and drawing an optical fiber, wherein in the drawing step, drawing is performed while applying pressure to a melted-deformed portion that is melted and deformed.