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.

Provided is an optical fiber containing an alkali metal element or the like having a smaller diffusion coefficient than K and having a low Rayleigh scattering loss. An optical fiber is composed of silica glass and includes a core and a cladding arranged to surround the core which has a lower refractive index than the core. The core includes a first core including a central axis and a second core arranged to surround the first core. The average concentration of an alkali metal element or alkaline-earth metal element in the first core is 10 mol ppm or less. The average concentration of chlorine in the first core is 2000 mol ppm or more. The average concentration of an alkali metal element or alkaline-earth metal element in the second core is 10 mol ppm or more. The average concentration of chlorine in the second core is 10 to 600 mol ppm.

A method of manufacturing a glass core preform for an optical fibre comprising: providing a porous soot core preform having an outer surface) and a central hole extending axially therethrough; dehydrating the porous soot core preform at a first temperature by exposing the outer surface of the preform to an atmosphere containing chlorine, and simultaneously consolidating the soot core preform and closing the central hole at a second temperature higher than the first temperature to form a glass core preform, wherein consolidating and closing comprises sequentially alternating flowing chlorine containing gas into the central hole and reducing the internal pressure of the central hole.

An optical fiber in which the increase of attenuation can be reduced is offered. An optical fiber is made of silica glass and includes a core and a cladding enclosing the core. The refractive index of the cladding is smaller than that of the core. The core includes chlorine and any of the alkali metal group. The chlorine concentration is 1 ppm or more in the whole region of the core. In the whole region of the core, the absolute value of rate of radial change of the chlorine concentration is smaller than 2000 ppm/m.

A highly purified quartz powder having a low level of naturally occurring lithium modified for cladding a fiber optic cable, said modified quartz powder having an increased total amount of lithium in solid solution in said powder, said increased total amount being in the range of more than 0.50 ppm and less than 1.00 ppm and a method of modifying an highly purified quartz powder to make the same.

The invention relates to Cr.sup.2+:ZnSe core optical fibers and methods of fabricating thereof, including a hybrid physical-chemical vapor deposition reaction. The invention relates also to Cr.sup.2+:ZnSe optical fiber lasers, in particular to a crystalline semiconductor optical fiber laser.

The disclosed fluorophosphate glasses for an active device include: a metaphosphate composition including Al(PO.sub.3).sub.3; a fluoride composition including BaF.sub.2 and SrF.sub.2; and a dopant composed of ErF.sub.3 and YbF.sub.3, and have thermal and mechanical properties to be able to be used as a glass base material for an active device (e.g., optical fiber laser), have a high emission cross-section characteristic, have a reinforced upconversion and downconversion emission characteristic, and have high sensitivity S in a cryogenic environment.

Disclosed is fluorophosphate glasses for an active device, the fluorophosphate glasses including: a metaphosphate composition including Mg(PO.sub.3).sub.2 of about 20 mol % to about 60 mol %; a fluoride composition including BaF.sub.2 of about 20 mol % to about 60 mol % and CaF.sub.2 of about 0 mol % to about 40 mol %; and dopants including rare earth elements, in which there is an effect of increasing a carrier lifetime at a metastable state energy level that is stimulated-emitted due to an efficient energy transfer phenomenon by composition optimization of dopants (e.g. Er and Yb).

Provided are an optical fiber and a manufacturing method of the optical fiber that can reduce transmission loss even when drawing is performed at a high tension and a high rate. An optical fiber has a core to which chlorine is added and a clad to which fluorine is added, chlorine of 9000 to 13000 ppm is added to the core, a relative refractive index difference 1 of the core to a pure silica glass is 0.09 to 0.13%, a relative refractive index difference 2 of the clad to a pure silica glass is 0.36 to 0.17%, a difference (12) between the relative refractive index difference 1 of the core and the relative refractive index difference 2 of the clad is larger than or equal to 0.30%, a mode field diameter at wavelength 1.31 m is 8.8 to 9.6 m, and a stress difference occurring at an interface between the core and the clad is lower than or equal to 60 MPa.

Provided are an optical fiber and a manufacturing method of the optical fiber that can reduce transmission loss even when drawing is performed at a high tension and a high rate. An optical fiber has a core to which chlorine is added and a clad to which fluorine is added, chlorine of 9000 to 13000 ppm is added to the core, a relative refractive index difference 1 of the core to a pure silica glass is 0.09 to 0.13%, a relative refractive index difference 2 of the clad to a pure silica glass is 0.36 to 0.17%, a difference (12) between the relative refractive index difference 1 of the core and the relative refractive index difference 2 of the clad is larger than or equal to 0.30%, a mode field diameter at wavelength 1.31 m is 8.8 to 9.6 m, and a stress difference occurring at an interface between the core and the clad is lower than or equal to 60 MPa.