Transmission loss behaviour of PCVD fibres in H2 atmosphere

The long-term irreversible loss increase of conventional GeO2-doped PCVD fibres in H2 atmosphere at room temperature is almost negligible. Purely F-doped fibres show virtually no H2-induced irreversible loss effects, even at high temperatures.     

Influence of impurities on loss increase in optical fibre

The influence of impurities on hydrogen-induced OH loss increase and radiation-induced loss increase is examined in GeO2-doped SiO2 fibres with a synthetic SiO2 clad. Fibres contaminated by both aluminium and sodium ions show loss increases as great as fibres with a natural SiO2 clad.     

Spectral loss characteristics of GeO2-P2O5-doped silica graded-index fibres in long-wavelength band

Spectral loss characteristics of GeO2-P2O5-doped silica graded-index fibres were investigated in the long-wavelength band. A broad absorption loss, increasing in proportion to the OH-ion concentration, was observed in the vicinity of 1.60 ?m wavelength.     

Fabrication of low-loss single-mode fibres

Low-loss single-mode fibres with GeO2-doped SiO2 cores have been made by the c.v.d. method and the loss spectrum from 0.6 to 1.8 ?m measured. The minimum loss of the fibre with suitably designed parameters, characterised by the refractive-index difference and the core diameter, was 0.75 dB/km at 1.05 ?m.     

Low-loss high-numerical-aperture optical fibre fabricated by v.a.d. method

Low-loss high-numerical-aperture optical fibres, consisting of GeO2/P2O5-doped silica core and silica cladding, have been made by the v.a.d. method. The minimum transmission loss of the fibre with an n.a. 0.32 was 0.8 dB/km at 1.55 ?m.     

Temperature dependence of second harmonic generation in germania-doped silica optical fibres

Seeded second harmonic generation (SHG) is compared between room temperature (RT) and liquid N/sub 2/ temperature (LNT) in GeO/sub 2/-doped silica fibres. At RT the SH power grows much more rapidly. The corresponding conversion efficiency after seeding for 2 h is over 20 times larger than at LNT.<>     

Very low OH content P2O5-doped silica fibres

Very low OH content optical fibres consisting of P2O5-doped silica core and GeO2-P2O5-B2O3-doped silica cladding were fabricated by the m.c.v.d. technique. The relation between the OH absorption loss and the deposition temperature was clarified. The OH content in this fibre could be reduced to about seven parts per billion (~ 7 × 10?9) by using a low deposition temperature.     

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.     

Refractive index dispersion of lightguide glasses at high temperature

The refractive index of pure and GeO2-doped silica glasses was measured at wavelengths from 0.4 ?m to 2.1 ?m, over a temperature range from 20°C to 540°C. Values for the thermal coefficient of the refractive index (about 1.2×10?5/°C at 1.3 ?m) were almost identical for both glasses. The data showed that material dispersion for optical fibres increases with increasing temperature.     

Pulse delay measurements in the zero-material-dispersion region for germanium- and phosphorus-doped silica fibres

Wavelength-dependent pulse dispersion in germanium- and phosphorus-doped silica fibres of different concentrations was measured using mode-locked subnanosecond pulses in the 1.064?1.55 ?m wavelength range. Zero dispersion for GeO2-SiO2 fibres was observed in the 1.3?1.33 ?m region depending on the concentration. P2O5-doped silica fibres showed zero dispersion near 1.28 ?m, independent of doping concentration.     

Visible-region optical absorption property for germanium-doped silica optical fibres induced by UV light propagation

Visible-region absorption and fluorescence are first observed for GeO2-doped silica optical fibres propagated by UV light in the 350?370 nm region. An absorption band at 1.97 eV and fluorescence at 1.91 eV are observed in the UV-propagated fibre. The absorption and fluorescence are considered to be caused by creation of the oxygen-hole centre.     

Dopant effect on transmission loss increase due to hydrogen permeation

The transmission loss increase due to hydrogen permeation in a GeO2-doped silica fibre and a P2O5-doped silica fibre are investigated. As a result, the difference of the loss increase between them is observed, and is considered to be due to the difference of the electronegativity between silica, germanium and phosphorus.     

Wavelength-dependent optical loss increase in graded-index optical fibre transmission lines

Wavelength-dependent optical loss increase in GeO2-P2O5-doped graded-index optical fibre transmission lines has been observed. The loss increase is found to depend strongly on the P2O5 concentration. By reducing the P2O5 concentration, loss increases at 1.3 ?m can be suppressed to a sufficient extent without any hindrance for practical usage.     

Multicomponent glass fibres with high numerical aperture

Multicomponent glass is suited for the preparation of high numerical aperture (n.a.) fibres which may be used in short-distance applications. Low loss of 20dB/km fibres have been produced with a n.a. of 0.53. Core glass having high refractive index has been prepared by using the additives of BaO and GeO2 which are hardly harmful to the intrinsic absorption loss.     

OH absorption in GeO2-doped fused silica fibres

The OH-ion absorption of SiO2/GeO2-core step-index multimode fibres in the 1.2?1.6 ?m region has been studied in relation to changing GeO2 concentrations. It was found that the OH absorption band at ? 1.4 ?m in SiO2/GeO2-core fibres had two components with maxima at 1.39 ?m and 1.42 ?m related to the first overtone of the fundamental OH vibration in SiO2 and GeO2, respectively.     

Low-Loss single-mode fibre at the material-dispersion-free wavelength of 1.27 ?m

A GeO2-doped silica single-mode optical fibre with a low attenuation loss of 0.5 dB/km at 1.27 ?m, where the material dispersion of the silica glass falls to zero, has been made by a C.V.D. technique. Attention was paid to reducing OH absorption losses in the single-mode fibre.     

Large-scale and high-density planar lightwave circuits with high- Delta GeO/sub 2/-doped silica waveguides

GeO/sub 2/-doped silica waveguides with a high refractive index difference ( Delta ) of 2% and a propagation loss of 0.1 dB/cm are fabricated on Si substrates. 200 cm-long test circuits and ring resonators are demonstrated, both with a minimum curvature of 2 mm.<>     

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.     

Effects of radiation on doped silica core optical fibres

The effect of ?-radiation on SiO2/GeO2 core fibres for times between 10?3 s and 1 h have been measured. Between 10?1 s and 30 min, these fibres offer a large improvement over previously published data. Addition of P2O5 in the core of these fibres reduces the transient response at the expense of long-term response. The P2O5:GeO2 ratio controls the level of response.     

Profile dispersion in multimode fibres: measurement and analysis

An electronically scanned interference microscope has been used to measure the refractive-index profile and its dispersion in optical fibres. From these measurements, we find that the power-law profile that best equalises modal delays in GeO2-S1O2 fibres should have an exponent that varies between 1.9 and 2.5 in the wavelength range from 0.5 to 1.1 ?m and is close to 2 at 0.9 ?m.