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.     

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.     

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.     

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.     

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.     

光纤中的多级斯托克斯及反斯托克斯谱线

本文叙述在多模光纤中产生的多级受激拉曼散射谱，作了两种不同掺杂的SiO2光纤中的受激拉曼散射谱。对掺锗硅光纤得到16级斯托克斯线及10级反斯托克斯线。对掺磁硅光纤获得了13级斯托克斯线及4～5级斯托克斯线。测出了各级谱线的峰值波长及相对强度分布，并作了简单讨论。     

800/1060 nm dual-wavelength pumped TDFA using single active pump source

Novel 800/1060 nm dual-wavelength pumping sources for Tm/sup 3+/-doped fibre amplifiers (TDFAs) are reported: a Nd/sup 3+/-doped silica fibre laser or a Nd/sup 3+/-doped microstructured silica fibre laser, both pumped near 800 nm and emitting near 1060 nm, providing the two required TDFA pump wavelengths. A new regime of pump power ratios is explored, in which the 800 nm power is comparable to the 1060 nm power. Gain and noise figure are comparable with those obtained using individual pump modules at the two wavelengths.     

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.     

Loss spectra of optical fibres under hydrogen and deuterium

Assignment of the frequencies at the loss peaks due to hydrogen permeation is clarified on the basis of the loss spectra in silica glass fibre under deuterium. As a result, it is concluded that the loss peaks due to hydrogen permeation in silica glass fibre are related to the combinational vibrations of hydrogen molecular vibration and SiO4 tetrahedral vibrations.     

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.     

210 mW 2.84 /spl mu/m Ho/sup 3+/, Pr/sup 3+/-doped fluoride fibre laser

210 mW of unsaturated continuous-wave output from a Ho/sup 3+/, Pr/sup 3+/-doped fluoride fibre laser is demonstrated using the /spl sim/1100 nm output from a free-running diode-cladding-pumped Yb/sup 3+/-doped silica fibre laser as the pump source. A slope efficiency of 3.2% and an output wavelength of 2.84 /spl mu/m are obtained.     

Direct evidence for laser reabsorption as initial cause for self-pulsing in three-level fibre lasers

The temporal characteristics of a standing wave Tm/sup 3+/-doped silica fibre laser are presented. For uni-directional pumping, the output displays the well-known self-pulsation phenomenon, but with bidirectional pumping, a significant increase in the laser stability is observed. A longitudinally uniform population inversion is shown to be of paramount importance to the stability of three-level lasers.     

Narrow-linewidth fibre laser with integral fibre grating

The fabrication and operation of an Nd3+-doped silica single-mode fibre laser using a distributed fibre grating as the feedback element is reported. The laser had a threshold of less than 2mW, a slope efficiency of 19% and an output bandwidth at the lasing wavelength of 1.084?m of 16 GHz, significantly narrower than the conventional cavity design.     

Microbending losses of P2O5-doped graded-index multimode fibre

Measurement results showing that the cabling loss of P2O5-doped MCVD graded-index multimode fibre increases for wavelengths longer than 1.3 ?m have been obtained. This letter investigates the cause for this loss increase. It also has been found that the loss increase is caused by P-OH bond absorption near the core-cladding boundary, where OH ions are diffused from the fused-quartz tube.     

Singly Ho/sup 3+/-doped fluoride fibre laser operating at 2.92 /spl mu/m

A singly Ho/sup 3+/-doped fluoride fibre laser that uses energy transfer upconversion to maintain the population inversion has produced 340 mW at 2.92 /spl mu/m. The /spl sim/1100 nm output from a diode-cladding-pumped Yb/sup 3+/-doped silica fibre laser was used as the pump source and a maximum slope efficiency of 5% was obtained.     

Forced pump oscillation at anti-Stokes wavelength of coupled Raman fibre laser resonators

Multi-watt oscillation of a Yb/sup 3+/-doped silica fibre pump laser is demonstrated at two wavelengths when pump-coupled Raman fibre laser resonators are constructed using fibre end reflection and a dielectric mirror, which are common to both the pump and Raman fibre lasers. Using an off-resonant Bragg grating to force the initial oscillation of the Raman fibre laser, pump emission at the anti-Stokes wavelength is demonstrated.     

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.     

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.<>     

Molecular hydrogen behaviour for loss increase of silica fibre in cable filled with water

Evaluation of molecular hydrogen diffusion into silica fibre, which causes a loss increase at 1.24 ?m wavelength, and the accumulation mechanism for hydrogen in cable are reported. It has been found that loss increase around 1.24 ?m wavelength due to hydrogen greatly depends on the ambient hydrogen pressure. The hydrogen pressure in LAP sheath cable easily increases due to metal corrosion and the sealing effect of the sheath.     

Laser diode pumped Pr/sup 3+/-doped and Pr/sup 3+/-Yb/sup 3+/-codoped fluoride fiber amplifiers operating at 1.3 mu m

Both Pr/sup 3+/-doped and Pr/sup 3+/-Yb/sup 3+/-codoped singlemode fibres with high numerical apertures are pumped by laser diodes with InGaAs/GaAs strained quantum well structures. A net gain of 5.2 dB is obtained from Pr/sup 3+/-doped fluoride fibre pumped by laser diodes operating at 1.1017 mu m and a net gain of 3.2 dB is obtained from Pr/sup 3+/-Yb/sup 3+/-codoped fibre pumped by laser diodes operating at 0.98 mu m. The pumping efficiency difference between Pr/sup 3+/-doped and Pr/sup 3+/-Yb/sup 3+/-codoped fibre is discussed.<>