A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein T.sub.h is at least about 50 C., preferably 50 C.<T.sub.h<250 C.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein T.sub.h is at least about 50 C., preferably 50 C.<T.sub.h<250 C.

A heat treatment apparatus includes: a furnace core tube made of silica glass; a heater provided adjacent to the furnace core tube, the heater heating a heating region; and a moving mechanism supporting a porous glass base material and relatively moving the porous glass base material with respect to the heater in the furnace core tube in a state where the heating region is heated by the heater to make the porous glass base material pass through the heating region. The heat treatment apparatus includes a thin-walled part provided in a region adjacent to a portion located in the heating region in the furnace core tube, the thin-walled part having a thickness of glass less than that of the portion located in the heating region.

A heat treatment apparatus includes: a furnace core tube made of silica glass; a heater provided adjacent to the furnace core tube, the heater heating a heating region; and a moving mechanism supporting a porous glass base material and relatively moving the porous glass base material with respect to the heater in the furnace core tube in a state where the heating region is heated by the heater to make the porous glass base material pass through the heating region. The heat treatment apparatus includes a thin-walled part provided in a region adjacent to a portion located in the heating region in the furnace core tube, the thin-walled part having a thickness of glass less than that of the portion located in the heating region.

Provided is a cooling water spray apparatus including a plurality of spinners disposed to be adjacent to one another along a travel path of a target to be cooled, and a plurality of cooling water spray holes provided on each spinner and configured to spray cooling water. The plurality of spinners may be non-overlappingly disposed with respect to one another.

A method for manufacturing an optical fiber is disclosed. The method for manufacturing an optical fiber includes: drawing an optical fiber by heating an optical fiber preform inside a drawing furnace into which a first gas is introduced; and annealing the optical fiber by causing the optical fiber to pass through an annealing furnace disposed downstream of the drawing furnace and adjusted to a temperature lower than a temperature at which the optical fiber preform is heated. In the annealing, a second gas having a lower heat conductivity than the first gas is introduced into the annealing furnace through one or more gas introduction ports such that a total flow rate becomes 3 slm or higher, and a flow rate of the second gas per gas introduction port is adjusted to 30 slm or lower.

A method for manufacturing an optical fiber is disclosed. The method for manufacturing an optical fiber includes: drawing an optical fiber by heating an optical fiber preform inside a drawing furnace into which a first gas is introduced; and annealing the optical fiber by causing the optical fiber to pass through an annealing furnace disposed downstream of the drawing furnace and adjusted to a temperature lower than a temperature at which the optical fiber preform is heated. In the annealing, a second gas having a lower heat conductivity than the first gas is introduced into the annealing furnace through one or more gas introduction ports such that a total flow rate becomes 3 slm or higher, and a flow rate of the second gas per gas introduction port is adjusted to 30 slm or lower.

The glass-fiber-yarn joined body 1 is provided with glass fiber yarns 2, 3, and a connection 5 in which a resin yarn 4 is wound around ends of both of the glass fiber yarns 2, 3, the ends being superimposed with each other. The connection 5 has a width W.sub.1 of 20 to 40 mm. When a connection diameter R as a total of diameters of the respective glass fiber yarns 2, 3 and the thickness of the resin yarn 4 wound around the connection 5 is 500 to 5000 m and a mass of each of the glass fiber yarns 2, 3 is 200 to 6000 tex, a value of a ratio of mass of each of the glass fiber yarns 2, 3 relative to the connection diameter R is in the range of 0.32 to 2.00.

The glass-fiber-yarn joined body 1 is provided with glass fiber yarns 2, 3, and a connection 5 in which a resin yarn 4 is wound around ends of both of the glass fiber yarns 2, 3, the ends being superimposed with each other. The connection 5 has a width W.sub.1 of 20 to 40 mm. When a connection diameter R as a total of diameters of the respective glass fiber yarns 2, 3 and the thickness of the resin yarn 4 wound around the connection 5 is 500 to 5000 m and a mass of each of the glass fiber yarns 2, 3 is 200 to 6000 tex, a value of a ratio of mass of each of the glass fiber yarns 2, 3 relative to the connection diameter R is in the range of 0.32 to 2.00.

A Photonic Crystal Fiber (PCF) a method of its production and a supercontinuum light source comprising such PCF. The PCF has a longitudinal axis and includes a core extending along the length of said longitudinal axis and a cladding region surrounding the core. At least the cladding region includes a plurality of microstructures in the form of inclusions extending along the longitudinal axis of the PCF in at least a microstructured length section. In at least a degradation resistant length section of the microstructured length section the PCF includes hydrogen and/or deuterium. In at least the degradation resistant length section the PCF further includes a main coating surrounding the cladding region, which main coating is hermetic for the hydrogen and/or deuterium at a temperature below T.sub.h, wherein T.sub.h is at least about 50 C., preferably 50 C.<T.sub.h<250 C.