A method for producing a tubular quartz glass composite body in an outside deposition method comprising the following method steps: providing a substrate tube, rotating the substrate tube about a rotation axis, depositing SiO.sub.2 particles on the outer lateral surface of the substrate tube to form a composite consisting of the substrate tube and an SiO.sub.2 soot body, and sintering the composite by heating at a sintering temperature to form the tubular quartz glass composite body. A substrate tube is provided which consists at least partially of quartz glass of a first quartz glass quality, and that the soot body consist of quartz glass of a second quartz glass quality, wherein the first quartz glass quality has a material-specific viscosity at the sintering temperature that is higher than the material-specific viscosity of the second quartz glass quality.

A device for producing a tubular SiO.sub.2 blank in an external deposition process has a substrate tube and a substrate tube holder comprising a clamping device, which is designed to support the substrate tube and to rotate the substrate tube about an axis of rotation. In order to provide, on this basis, a reproducible and operationally reliable holder for a large-volume, tubular SiO.sub.2 blank in an external deposition process, it is proposed that the substrate tube holder comprise a clamping mechanism which has a first pressure unit abutting the first substrate tube end face, a second pressure unit abutting the second substrate tube end face, and at least one force element which is designed to generate an axial contact pressure with a force component acting in the direction of the longitudinal axis of the substrate tube.

A method of manufacturing at least one optical fibre preform comprising: providing a plurality of partially porous intermediate preforms, each partially porous intermediate preform having a longitudinal axis and comprising a respective soot intermediate clad layer formed around a respective glass core rod comprising a central core region of radius a and an inner clad region of radius b to define a first core-to-clad ratio a/b; consolidating the formed soot intermediate clad layers to form a respective plurality of intermediate glass preforms, each of the plurality of intermediate glass preforms comprising an intermediate clad region having an external radius c to define a second core-to-clad ratio a/c of from 0.20 to 0.30 , and overcladding at least one intermediate glass preform by forming an overclad region surrounding the intermediate clad region to form an optical fibre glass preform, wherein consolidating comprises exposing the plurality of intermediate preforms to a consolidation hot zone of a single furnace body while rotating each of the intermediate preforms about its respective longitudinal axis.

Provided is a glass base material hanging mechanism that, when hanging a starting member or a glass base material, can tightly (solidly) connect the hanging shaft tube and the hanging component and can vertically align the hanging component and the center of the glass base material.

A production apparatus capable of suppressing the generation of rusts on a base material gripper and a rotation mechanism is provided in a production of a porous glass preform. In an apparatus for producing a porous glass preform by depositing glass fine particles, produced by a flame hydrolysis reaction using a burner, on a starting member gripped by a base material gripper in a reaction vessel, the base material gripper is covered with a cover, and gas is supplied to the inside of the cover and the gas is caused to flow from the inside of the cover to an inside of the reaction vessel.

A gripping mechanism includes: a plurality of chuck claws that, when having come close to each other, generate a gripping force on a gripped body; a chuck body that holds the plurality of chuck claws on a common planar surface, and moves them on the planar surface; and a plurality of chuck plates that, when each of the plurality of chuck claws grips the gripped body, are interposed between each of the plurality of chuck claws and the gripped body, wherein a thermal expansion coefficient .sub.l of the plurality of chuck claws, a thermal expansion coefficient .sub.2 of the plurality of chuck plates and a thermal expansion coefficient .sub.W of the gripped body has a relationship indicated by Equation 1:

.sub.W<.sub.1<.sub.2 (Equation 1)

Provided is a method for manufacturing an optical fiber preform includes supporting at least one end of an optical fiber preform with a gripping portion; and heating the optical fiber preform while rotating it to process the optical fiber preform, wherein the optical fiber preform is gripped by the gripping portion via a buffer material comprising the gripping portion; wherein the buffer material includes a surface side member in contact with the optical fiber preform, and a surface side member in contact with the gripping portion; wherein a composition of the surface side member in contact with the optical fiber preform and the surface side member in contact with the gripping portion are different; and the surface side member in contact with the optical fiber preform does not contain any of Ca, Mg, Al, K, Na, Mg, or Ba.

An apparatus includes an all-fiber side-pump combiner fabrication system and a control unit coupled to control operations of the all-fiber side-pump combiner fabrication system to produce a (N+1)1 combiner with N side pump fibers.