Abstract: The invention relates to a bundle of optical fibers and a process for its preparation, wherein at least two of the optical fibers are at least partly attached to each other lengthwise by means of a removable longitudinal bridging element. Typically, the bridging element is an open one-hole capillary.

Abstract: An optical waveguide including a core, a buffer surrounding the core, and a cladding surrounding the buffer. The core, the buffer and the cladding include silica glass. A refractive index of the buffer is substantially equal to a refractive index of pure amorphous silica glass. The buffer may reduce bubble formation during manufacturing and may facilitate splicing of the waveguide. A numerical aperture of the waveguide may be fine-tuned by adjusting a radial dimension of the buffer in order to compensate variations in the refractive index of the core.

Abstract: A method and a liquid feeding device for feeding liquid in a flame spraying apparatus that is arranged for treating an optical fiber structure, as well as a flame spraying apparatus in which liquid feeding is arranged according to the invention. Liquid is supplied to an unpressurized space in a pressure generating part substantially in a constant flow. In the pressure generating part the pressure of liquid is generated by means of gravity influencing the liquid, and the pressurized liquid is arranged to be supplied to the flame spraying at a substantially constant pressure and at a constant flow rate.

Abstract: A method for preparing doped oxide material, in which method substantially all the reactants forming the oxide material are brought to a vaporous reduced form in the gas phase and after this to react with each other in order to form oxide particles. The reactants in vaporous and reduced form are mixed together to a gas flow of reactants, which gas flow is further condensated fast in such a manner that substantially all the component parts of the reactants reach a supersaturated state substantially simultaneously by forming oxide particles in such a manner that there is no time to reach chemical phase balances.

Abstract: A light-amplifying fiber arrangement including a pump fiber including glass and a bridge element. At least a portion of a side of the bridge element has been fused to at least a portion of a side of the pump fiber. An active fiber includes a light-amplifying core and a first cladding. The first cladding includes glass. At least a portion of a side of the active element has been fused to at least a portion of a side of the bridge element. A second cladding surrounds the pump and active fibers in order to confine pump light to the fibers. The second cladding includes glass. The arrangement allows coupling of high power levels into the pump fiber, wherein splicing of pigtails to the arrangement is easier than e.g. in case of conventional doubly clad fibers.

Abstract: The invention relates to a process of preparing an optical fiber joint, wherein an optical fiber or its undrawn precursor is brought into contact with a longitudinal element and attached to it via a ridge-groove fitting prior to drawing of the final optical fiber joint. The longitudinal element can be another optical fiber or its precursor or a removable and/or workable bridging element.

Abstract: A light-amplifying fiber arrangement including a pump fiber including glass and a bridge element. At least a portion of a side of the bridge element has been fused to at least a portion of a side of the pump fiber. An active fiber includes a light-amplifying core and a first cladding. The first cladding includes glass. At least a portion of a side of the active element has been fused to at least a portion of a side of the bridge element. A second cladding surrounds the pump and active fibers in order to confine pump light to the fibers. The second cladding includes glass. The arrangement allows coupling of high power levels into the pump fiber, wherein splicing of pigtails to the arrangement is easier than e.g. in case of conventional doubly clad fibers.

Abstract: A method and a device in optical fiber based spectral filtering. A length of an optical fiber including at least a core region surrounded by a cladding region is coiled over its length in whole or in part to subject the fiber to longitudinal curvature in order to affect the optical transmission properties of the fiber. The fiber is arranged to have radially asymmetric refractive index distribution and in addition to coiling the fiber lengthwise, the fiber is over its length in whole or in part also twisted around its longitudinal axis. The method and device can be used to significantly improve the performance of fiber based filtering devices.

Abstract: A method for charging particles used for processing of a material. At least a gaseous reactant is supplied and oxidizing gas is supplied to the reactant. The oxidizing gas is charged electrically before it is supplied to the reactant. The reactant and the oxidizing gas form charged particles. The material to be processed is advantageously a multicomponent oxide construction, such as an optical fiber preform. The invention also related to a charging device implementing the method.

Abstract: A method and a liquid feeding device for feeding liquid in a flame spraying apparatus that is arranged for treating an optical fiber structure, as well as a flame spraying apparatus in which liquid feeding is arranged according to the invention. Liquid is supplied to an unpressurized space in a pressure generating part substantially in a constant flow. In the pressure generating part the pressure of liquid is generated by means of gravity influencing the liquid, and the pressurized liquid is arranged to be supplied to the flame spraying at a substantially constant pressure and at a constant flow rate.

Abstract: The invention relates to the production of light-amplifying optical material. Liquid reactant is atomized into droplets using a high velocity gas. The droplets are subsequently introduced into a flame. Reactants are oxidized in the flame and condensed by forming small particles. At least a fraction of said particles is collected and fused to form optical waveguide material, which is subsequently drawn to form an optical waveguide. According to the invention, the velocity of the atomizing gas stream is in the order of the velocity of sound. The high velocity enhances atomization and increases reaction rates in the flame. The residence times are reduced to such a degree that unwanted phase transformations in the produced particles are substantially minimized. Consequently, very homogeneous material is produced. Especially, in the production of erbium-doped silica, low percentage of clustered erbium ions is achieved.

Abstract: A method and a device in optical fiber based spectral filtering. A length of an optical fiber including at least a core region surrounded by a cladding region is coiled over its length in whole or in part to subject the fiber to longitudinal curvature in order to affect the optical transmission properties of the fiber. The fiber is arranged to have radially asymmetric refractive index distribution and in addition to coiling the fiber lengthwise, the fiber is over its length in whole or in part also twisted around its longitudinal axis. The method and device can be used to significantly improve the performance of fiber based filtering devices.

Abstract: A system and a method in producing a doped glass material, particularly a glass material to be used in light amplifying optical waveguides. The method comprising: bringing at least a first dopant and a second dopant of the glass material into a vaporous gas phase; controlling the vapour pressure of the gas phase of each dopant by bringing each dopant to a desired temperature which is simultaneously used to control the composition of their gas phase; and mixing each vaporous dopant with the gas flow of the basic material for the glass material, which basic material is also in a gas phase and is used as a carrier gas for the dopants, wherein said basic material and said dopants together constitute the required gas flow of so-called reactants, to be used for producing the glass material; performing the mixing so that said dopants are each mixed in turn with the same gas flow of the basic material in such an order that said desired temperatures of the dopants are increasing in relation to one another.