Low loss and low OH content soda-lime-silica glass fibre

Low loss soda-lime-silica glass fibres of minimum loss of 4.23 dB/km at 0.85 ?m were prepared with 6.5 dB/km extra absorption loss due to OH radicals at 0.97 ?m. The loss factors were analysed from the impurity contents and scattering loss. These fibres have been developed by unique preparation techniques of wet mixing of raw materials and dry gas flow at glass melting.     

Fluoride glass etching method for preparation of infra-red fibres with improved tensile strength

A method for the congruent dissolution of zirconium fluoride glass using an aqueous solution with zirconium ions as a complexing agent is described. Preform cleaning by this technique leads to IR fibres with mean tensile strength values as high as 400 MPa, which is an improvement by a factor of 2. The transmission loss of Teflon-jacketed fibres could be reduced by a factor of ten in comparison to fibres from untreated preforms.     

Ten-port graded-index waveguide star coupler fabricated by dry ion diffusion process

A ten-port planar star coupler has been developed, utilising multimode waveguides easily formed in a glass substrate by evaporated silver ion diffusion. The waveguides have circular cross-sections with graded-index profile, which matches well to graded-index multimode fibres. Insertion loss of 6 dB and the loss variation of 0.8 dB were attaied.     

Multi-glass-rod optical-fibre splicers made by drawing technique

New splicers for optical fibres have been fabricated in a process in which arrayed glass rods are heated and drawn together. The splicers exhibit low average splicing loss of less than 0.1 dB, slight loss fluctuation of less than 0.05 dB in the temperature range ?20°C~ +60°C, and are potentially low in cost.     

Chemical change from diffused hydrogen gas to hydroxyl ion in silica glass optical fibres

The chemical change from hydrogen gas that diffuses into silica glass for optical fibres to hydroxyl function has been investigated. Hydrogen molecules that diffuse into GeO2-doped silica glass at 500°C easily change into OH ions by thermal energy, while this chemical change does not occur in pure silica glass at 500°C. Also, germanium-doped silica fibre, in which hydrogen gas is dissolved at room temperature, shows OH ion absorption loss increase with chemical change by heat treatment at above 100°C, while pure silica core fibre shows no OH ion absorption loss increase by the same treatment.     

Fabrication of low-loss Al2O3-doped silica fibres

This letter is concerned with the alternative dopant of Al2O3 for VAD silica-based optical fibres. In order to clarify basic loss characteristics of Al2O3-doped silica glass fibres, single-mode fibres were made. The fabricated single-mode fibre shows an ideal step-index profile and a low transmission loss of 0.65 dB/km at 1.56 ?m.     

Low-loss GaAs/GaAlAs strip-loaded waveguides with high coupling efficiency to single-mode fibres

We report measurements of low-loss MOVPE-grown GaAlAs/GaAs strip-loaded waveguides with high coupling efficiency to single-mode fibres. A propagation loss of 2 dB/cm and a coupling efficiency of 70% has been achieved for a p+-i-n+-structure waveguide. A propagation loss of 0.7 dB/cm and a coupling efficiency of 61% has also been achieved for an n?-i-n?-structure waveguide.     

Fusion splicing of heavy metal fluoride glass optical fibres

Heavy metal fluoride (HMF) glass optical fibres were spliced by fusing the two ends of fibres using a DC arc. An average optical loss of 0.08 dB per splice and strengths of up to 600 MPa were achieved for fusion splices using an inert gas purge during splicing. Estimates are made to determine the feasibility of achieving a splice loss of 0.005 dB for single-mode (HMF) fibres.<>     

Fibre loss increase due to hydrogen generated at high temperatures

The loss changes at 1.39 and 1.88 ?m are measured for various nylon-jacketed fibres at a high temperature of 200°C. The loss increase at 1.39 ?m is due to the Si-OH-bond formation, and that at 1.88 ?m is caused by the absorption of hydrogen molecules in the silica glass. It is found that the loss increase due to the OH-bond formation is in proportion to the time-integrated concentration of the generated hydrogen molecules.     

Fused single mode fibre access couplers

Single mode fibre access couplers have been fabricated by chemically etching most of the glass cladding material surrounding the fibre core, and thermally fusing the fibres together in the etched region. The resulting couplers have low loss and are both durable and insensitive to ambient temperature variations.     

Reduced loss in extruded soft glass microstructured fibre

The fabrication of small core high-NA soft glass microstructured optical fibres with propagation loss as low as 0.6 dB/m at 1100 nm is reported. Advances in soft glass preform extrusion and fibre fabrication have allowed the first demonstration that extrusion does not significantly contribute to the fibre loss.     

Low-loss splices for single mode fibres

A technique for producing low-loss splices in single-mode fibres has been developed and evaluated. The splices are made by sandwiching the fibre butt-joint ends between a glass V-groove block and a flat glass plate, both of which are made by fibre-drawing techniques. A new splice-loss measuring technique is described. The majority of splices made on identical fibres have losses of less than 0.01 dB.     

Loss increase in deuterium-doped VAD fibres with heat treatment

The origin of the increase in the intensity of OH bands with heat treatment has been investigated using deuterium-containing VAD fibres. Remarkable loss increases only in the absorption peaks due to the OH ions have been observed after 200?500°C heat treatment applied to three kinds of fibre: drawn from a preform prepared by a D2-O2 flame, and OD-doped in the core and in the cladding. It was confirmed that the origin of the hydrogen causing the loss increase is not in the synthesised glass materials.     

Realistic efficiency of coupling light from GaAs laser diodes into parabolic-index optical fibres

More than 500 laser diodes have been coupled to graded-index fibres using microscopic glass beads for a proper injection into the fibre core. The coupling efficiencies have a good reproducibility and a high average value.     

Chalcogenide holey fibres

The fabrication of the first non-silica holey or microstructured optical fibre is reported. The chalcogenide glass gallium lanthanum sulphide was used. Applications of such fibres include optical switching, high power-delivery, acousto-optic devices, air-guiding fibres, fibre sensors, mid-IR devices, amongst others. In addition, holey fibre technology provides an improved route towards fabricating singlemode compound glass fibres     

Fluoride glasses for infra-red optical fibres

Fluoride glasses in the ZrF4-BaF2-RF3 system (R=Gd, Yb) have been investigated as potential low loss materials for achievement of fibres transmitting wavelengths at about 3?5 ?m. Optical measurements confirm the interest in such components and PbF2 doping allows substantial refractive index increases, making for feasible doped core glass preforms.     

Infra-red optical loss increase for silica fibre in cable filled with water

Loss increase characteristics of optical fibre in cable filled with water are reported. Drastic loss increase around 1.24 ?m is observed for both graded-index and single-mode fibres. The origin of the loss increase is found to be due to hydrogen gas diffused into the silica glass interstitially.     

Low-loss optical glass fibre with Al2O3-SiO2 core

Optical glass fibres, consisting of an Al2O3-SiO2 core and SiO2 cladding, were produced by using a glass growth technique of vapour deposition in a flame. The core measured from 4 to 10 ? in diameter, and the difference in refractive index between the core and the cladding was 0.003. The lowest loss of this fibre was 10 dB/km at 0.66 ?m.     

Effect of deposition rate on spectral loss of GeO2-P2O5-SiO2 graded index fibres

Low loss, low OH content 0.23 n.a. graded index germanium phosphosilicate fibres have been fabricated using the m.c.v.d. process at rates up to 0.34 g/min with deposited layer thicknesses up to 16 ?m. The deposition rate did not affect achievement of low loss in the spectral range 0.7 ?m?1.7 ?m.     

Hydrogen permeation in optical fibres with hermetic carbon coatings

Hydrogen permeation has been measured for optical fibres with hermetic carbon coatings. Data obtained at elevated temperatures and high hydrogen pressures lead to predictions of extremely low permeation rates at typical operating conditions. In situ loss measurements have shown the existence of a lag time, during which no hydrogen reaches a fibre's interior