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.

The invention relates to a method for producing a glass-fibre preform with a core of a polygonal cross section by using a rod-in-tube method and comprising the method steps of: providing a core rod (1) of a polygonal core rod cross section (2), producing a sectored sandwich tube (3) from a starting tube (4), wherein the lateral surface of the starting tube (4) is slit in the longitudinal direction into a series of outer segments (8), and so the tube cross section of the starting tube (4) is subdivided into a series of sectors of a circle (7), inserting the core rod (1) into the sectored sandwich tube (3) and aligning it and, in the case of one embodiment, inserting the core rod (1) and the sectored sandwich tube (3) into an outer casing tube (10) with a complete annular cross section and melting the sectored sandwich tube (3) and possibly the outer casing tube (10) onto the sectored sandwich tube (3), wherein the outer segments (8) of the sectored sandwich tube (3) are fused to the respective side surfaces (9) of the core rod (1).

To achieve a high degree of precision and an exact positioning of anti-resonant elements in a sufficiently stable and reproducible manner in an anti-resonant hollow-core fiber which has a hollow core extending along a fiber longitudinal axis and an inner jacket region that surrounds the hollow core, formation of anti-resonant element precursors includes formation of elongated pressure chambers, each of which adjoins a wall deformable under pressure and heat in the region of target positions of the anti-resonant elements. A section of the deformable wall is caused to protrude in the direction of a cladding tube inner bore, thereby forming an anti-resonant element or a precursor for same, while carrying out a process of elongating a primary preform to form the hollow-core fiber or further processing the primary preform to a secondary preform from which the hollow-core fiber is drawn.

Methods are known for producing an anti-resonant hollow-core fiber which has a hollow core extending along a fiber longitudinal axis and an inner jacket region that surrounds the hollow core, said jacket region comprising multiple anti-resonant elements. The known methods have the steps of: providing a cladding tube that has a cladding tube inner bore and a cladding tube longitudinal axis along which a cladding tube wall extends that is delimited by an interior and an exterior; providing a number of tubular anti-resonant element preforms; arranging the anti-resonant element preforms at target positions of the interior of the cladding tube wall, thereby forming a primary preform which has a hollow core region and an inner jacket region; and elongating the primary preform in order to form the hollow-core fiber or further processing the primary preform in order to form a secondary preform. The aim of the invention is to achieve a high degree of precision and an exact positioning of the anti-resonant elements in a sufficiently stable and reproducible manner on the basis of the aforementioned methods. This is achieved in that a positioning template is inserted into the cladding tube inner bore in order to arrange the anti-resonant element preforms, said template having holding elements for positioning the anti-resonant element preforms at the target positions.

The invention relates to a method for producing a polarization-maintaining optical fiber, consisting of a core region and stress-generating elements embedded in the fiber body, having the following method steps: producing a core preform for the core region using internal deposition on a substrate tube, the internally coated substrate tube subsequently being collapsed, generating recesses on the core preform by virtue of the material on the outer surface of the core preform being removed parallel to the longitudinal axis of the core preform at diametrically opposed positions, filling the recesses with stress-generating rods, with the tightest possible rod packing, in a freely selectable first filling geometry, possibly filling the recesses in addition with non-stress-generating rods in a second filling geometry, sheathing the filled core preform with a jacketing tube, preparing the sheathed core preform for a fiber-drawing process, and drawing the sheathed arrangement to form the optical fiber. A preform for producing a polarization-maintaining optical fiber contains a core preform, having a core region and a lateral region, and also contains a jacketing tube, which encloses the core preform, as well as stress-generating elements contained in the lateral region, wherein the stress-generating elements are provided in the form of recesses in the lateral region, wherein the recesses are filled with doped rods and/or undoped rods, and wherein the rod filling forms a first and/or a second arrangement geometry.

A production method of an optical fiber preform includes first preparing a first preform having a plurality of glass preforms and a first cladding portion disposed between the plurality of glass preforms, and first arranging a second cladding portion to surround the first preform. At the first arranging, a material gas and a combustion gas are ejected from a burner to produce glass particles. The first preform and the burner are moved relative to each other in a longitudinal direction of the first preform. The glass particles are deposited on the first preform.

The invention relates to a method for producing a polarization-maintaining optical fibre, consisting of a core region and stress-generating elements embedded in the fibre body, having the following method steps: producing a core preform for the core region using internal deposition on a substrate tube, the internally coated substrate tube subsequently being collapsed, generating recesses on the core preform by virtue of the material on the outer surface of the core preform being removed parallel to the longitudinal axis of the core preform at diametrically opposed positions, filling the recesses with stress-generating rods, with the tightest possible rod packing, in a freely selectable first filling geometry, possibly filling the recesses in addition with non-stress-generating rods in a second filling geometry, sheathing the filled core preform with a jacketing tube, preparing the sheathed core preform for a fibre-drawing process, and drawing the sheathed arrangement to form in the optical fibre. A preform for producing a polarization-maintaining optical fibre contains a core preform, having a core region and a lateral region, and also contains a jacketing tube, which encloses the core preform, as well as stress-generating elements contained in the lateral region, wherein the stress-generating elements are provided in the form of recesses in the lateral region, wherein the recesses are filled with doped rods and/or undoped rods, and wherein the rod filling forms a first and/or a second arrangement geometry.

Methods for producing a multicore fiber comprise a method step in which a component group is reshaped to form the multicore fiber or a pre-form for the multicore fiber, which comprises a hollow cylinder comprising a central bore and a hollow cylinder longitudinal axis, which hollow cylinder comprises a cladding glass region made of cladding glass and a plurality of core glass regions occupied by a core glass, wherein at least part of the central bore is occupied by a glass filling material. In order to provide a method for producing multicore fibers without central signal core, in which the risk of rejects during the completion of the hollow glass cladding cylinder is reduced, a marker element made of marker glass adjacent to the glass filling material is used, which extends along the longitudinal axis of the central bore.

A high degree of precision and an exact positioning of anti-resonant elements in a sufficiently stable and reproducible manner is achieved in that a step of providing a cladding tube includes a processing measure, in which the cladding tube wall is machined with a longitudinal structure extending in the direction of the cladding tube longitudinal axis in the region of the target positions.

A multicore fiber includes: a plurality of core portions made of glass; and a cladding portion made of glass and configured to surround outer periphery of the plurality of core portions. The cladding portion has tensile stress of 20 MPa or lower in a region on outer periphery side than a core portion that is closest to outer periphery of the cladding portion in the plurality of core portions.