Abstract:
An optical fiber including: (i) a silica based, rare earth doped core (12) having a first index of refraction n 1 ; (ii) a silica based inner cladding (14) surrounding the core and having a second index of refraction n 2 , such that n 1 >n 2 , the inner cladding having a plurality of air holes (24, 26) extending longitudinally through the length of the optical fiber; (iii) a silica based outer cladding (16) surrounding the inner cladding and having a third index of refraction n 3 , such that n 2 >n 3 ; wherein the optical fiber supports a single polarization mode within the operating wavelength range.
Abstract:
An optical fiber suitable to support single mode optical transmission at longer wavelengths (e.g., 1550 nm) is formed to comprise a pure silica core region and a "down doped" cladding layer. The core region is defined as having a diameter d and the cladding layer is defined has having an outer diameter D. In accordance with the present invention, single mode propagation wí11 be supported when D/d > 8.5, and is preferably in the range of 9 - l 0.
Abstract:
The present invention provides a method of fabricating rare earth doped preforms and optical fibres by a combination of modified chemical vapour deposition (MCVD) process and solution doping technique said (MCVD) process is used to develop matched or depressed clad structure inside a silica glass substrate tube followed by deposition of porous silica soot layer containing GeO 2 , P 2 O 5 or such refractive index modifiers by the backward deposition method for formation of the core and presintering the deposited particulate layer by backward pass with flow of GeCl 4 and/or corresponding dopant halides, soaking the porous soot layer into an alcoholic/aqueous solution of RE-salts containing codopants such as AlCl 3 in definite proportion, drying, oxidation, dehydration and sintering of the RE containing porous deposit and by collapsing at a high temperature to produce the preform followed by drawing the fibres by known technique to produce fibres with suitable core-clad dimensions and geometry.
Abstract:
The present invention relates to an optical fiber and a planar waveguide for achieving a uniform optical attenuation, which comprises a core co-doped with a first metal ions having an optical absorption coefficient of a negative slope in a particular wavelength band and a second metal ions having an optical absorption coefficient of a positive slope in a predetermined wavelength band.
Abstract:
The present invention provides an improved process for making rare earth doped preforms and fibres by a combination of MCVD technique and solution doping method, said method comprising developing matched or depressed clad structure inside a silica glass substrate tube followed by deposition of unsintered particulate layer containing GeO 2 and P 2 O 5 for formation of the core and solution doping by soaking the porous soot layer into an alcoholic/aqueous solution of RE-salts containing co-dopants like AlCl 3 / Al(NO 3 ) 3 in definite proportion, controlling the porosity of the soot, dipping period, strength of the solution and the proportion of the codopants to achieve the desired RE ion concentration in the core and minimise the core clad boundary defects and followed by drying, oxidation, dehydration and sintering of the RE containing porous deposit and collapsing at a high temperature to produce the preform and overladding with silica tubes of suitable dimensions and fibre drawing to produce fibres.
Abstract:
An object of the present invention is to provide a quartz glass tube for optical fiber preforms capable of producing optical fiber preforms having high dimensional precision, excellent distribution of refraction index, and yet free from degradation and the like of working environment. The object above is accomplished by a quartz glass tube for use in the production of optical fiber preforms, characterized in that the high temperature viscosity thereof is varied in the wall thickness direction, and that the high temperature viscosity in the inner layer side is lower than that of the outer layer side. It is shown how the viscosity and the refractive index are influenced by different doping agents to optimize producing parameters for the optical fiber preform and the distribution of refraction index of the optical fiber preform obtained. A method for producing an optical fiber preform comprising inserting a core glass rod into said quartz glass tube and melt welding them together is also disclosed.
Abstract:
Glass soot (130) is deposited on a glass rod by a burner (140). The body is stretched (126). More depositing and stretching is effected. The final body is then drawn into a fiber.
Abstract:
A process for the manufacture of a synthetic silica product by vapour-phase oxidation of a silica precursor material in a flame not less than 60 % of the silica in the deposited product being derived by oxidation of: (A) one or more straight chain volatile silicon compounds of the general formula: R3Si.O(SiR2O)n.SiR3 and/or (B) one or more cyclic volatile silicon compounds of the general formula: SinOn(R)2n. Doped or undoped fume powder, porous silica soot or fully densified bodies made by the process are also claimed.