A system and methods are described herein for preheating a preform in a preheater furnace and then transferring the preheated preform to a consolidation furnace for chemical treatment and sintering the preform into a clear glass which can be drawn into optical fiber. In addition, the preheater furnace is described herein which is configured to heat the preform per a predetermined heat-profile until the preform is uniformly heated to a temperature above 1000° C.

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 by providing anti-resonant element preforms which have at least one respective ARE outer tube and/or at least one respective ARE inner tube, wherein the ARE outer tube and/or the ARE inner tube is produced using a vertical drawing method without molding tools.

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; further processing the primary preform in order to form a secondary preform, including an elongation process; and drawing the secondary preform in order to form the hollow-core fiber. 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 after the primary preform is elongated, at least some of the formerly tubular anti-resonant element preforms of the primary preform have an oval outer cross-sectional shape with a longest cross-sectional axis A.sub.L and a shortest cross-sectional axis A.sub.K, wherein the ratio A.sub.L/A.sub.K of the length of the axes ranges from 1.01 to 1.27, and the shortest cross-sectional axis A.sub.K runs in a radial direction when viewed from the cladding tube longitudinal axis.

A method for elongating a glass preform for an optical fiber is provided for producing a glass rod having a smaller diameter by elongating the glass preform having a large diameter, the method including: when the glass preform having a tapered transparent glass portion at one end of a straight body of the glass preform and a tapered portion including an opaque glass portion at another end is elongated, prior to the elongating, cutting a part of the tapered portion including the opaque glass portion, wherein a cut surface of the part is a lower end of the glass preform; and welding the cut surface of the tapered portion to a pulling dummy connected to a pulling mechanism in a elongating apparatus, wherein the cut surface is circular and has an outer diameter ranging from 135 mm to 160 mm.

A gas pressure maintaining and adjusting device, a microstructure optical fiber and a preparation method of the microstructure optical fiber belong to the field of preparation of special optical fibers. In the gas maintaining and adjusting device, a communication control module is electrically connected with a main console of an optical fiber drawing tower; a signal output end of the communication control module is connected with a signal receiving end of a programmable logic controller (PLC); the PLC is provided with a gas pressure threshold display screen; the signal receiving end of the PLC is further connected with a signal output end of a pressure controller; and the PLC is further connected with an electromagnetic valve used for controlling opening and closing of a gas inlet and a gas outlet.

Systems and methods for drawing high aspect ratio metallic glass-based materials are provided. Methods of drawing a high aspect ratio metallic glass-based material are premised on stably drawing high aspect ratio metallic glass-based material from a preform metallic glass-based composition, accounting for the relationships between: the desired formation of an amorphous structure that is substantially homogenous along the majority of the length of the drawn high aspect ratio material; the desired final geometry of the drawn high aspect ratio material; the nature of the force that is used to draw the molten metallic glass-based composition; the velocity at which the high aspect ratio material is drawn; the viscosity profile of the material along its length as it is being drawn; and/or the effect of temperature on the metallic glass-based material. A precise thermal treatment is imposed along the forming length of the drawn material so as to enable a steady state drawing process, the precise thermal treatment being based on: the desire to develop a substantially same amorphous structure along the length of the drawn material; the desired final geometry for the drawn material; the nature of the force used to draw the material; the velocity at which the material is being drawn; and/or the thermal treatment's impact on the viscosity profile of the material along its length as it is being drawn.

A drawing system for polygonal optical fiber is provided, comprising: a clamping moving device, a furnace, a protective layer coating device, at least a protective layer drying system, and a fiber take-up device, all arranged from top to bottom; the clamping moving device clamping a polygonal preform rod and slowly moving the preform rod into the furnace; a polygonal optical fiber extracted from bottom of the furnace passing sequentially through the protective layer coating device, the protective layer drying system, and finally the fiber take-up device controlling drawing speed of the polygonal optical fiber, characterized in that: at least two optical fiber micrometers being disposed between the furnace and the protective layer coating device, and the two optical fiber micrometer respectively measuring two outer diameters of different sizes of the polygonal optical fiber; the fiber take-up device adjusting the drawing speed according to measurement results of the optical fiber micrometers.

A system and methods are described herein for preheating a preform in a preheater furnace and then transferring the preheated preform to a consolidation furnace for chemical treatment and sintering the preform into a clear glass which can be drawn into optical fiber. In addition, the preheater furnace is described herein which is configured to heat the preform per a predetermined heat-profile until the preform is uniformly heated to a temperature above 1000 C.

A method for elongating a glass preform for an optical fiber is provided for producing a glass rod having a smaller diameter by elongating the glass preform having a large diameter, the method including: when the glass preform having a tapered transparent glass portion at one end of a straight body of the glass preform and a tapered portion including an opaque glass portion at another end is elongated, prior to the elongating, cutting a part of the tapered portion including the opaque glass portion, wherein a cut surface of the part is a lower end of the glass preform; and welding the cut surface of the tapered portion to a pulling dummy connected to a pulling mechanism in a elongating apparatus, wherein the cut surface is circular and has an outer diameter ranging from 135 mm to 160 mm.

An optical fiber preform includes a silica-glass core portion, and a cladding portion surrounding the core portion, the cladding portion being composed of a fluorine-containing silica glass having a lower refractive index than the core portion, the core portion including a first region that does not include the central axis thereof, the first region containing a first dopant selected from sodium, potassium, and compounds thereof, and a second region that includes the central axis, the second region containing a second dopant that reduces the viscosity of the silica glass, the second dopant having a diffusion coefficient of 110.sup.12 cm.sup.2/s or more and less than the first dopant at 2,000 C. to 2,300 C., in which the entire core portion has an average first dopant concentration of 10 atomic ppm or more and 2,000 atomic ppm or less and an average second dopant concentration of 10 atomic ppm or more.