Transmission loss increase in optical fibres due to hydrogen permeation

The experiment of soaking the optical fibre cable in water is carried out. As a result, a tremendously large transmission loss increase is observed at 1.24 ?m. Through a fundamental experiment, it is shown that hydrogen permeation causes the transmission loss increase in optical fibres.     

Loss increase for optical fibers exposed to hydrogen atmosphere

Loss spectrum changes for optical fibers exposed to a hydrogen atmosphere in the15-200degC temperature range are measured. Loss increase due to molecular hydrogen dissolved into fibers is investigated from the loss peak at 1.24 μm, and that due to hydroxyl group formation from the loss peak at 1.41 μm. The loss increase due to molecular hydrogen is fully explained by physical solubility theory and diffusion equation. The empirical formula for time, temperature, and hydrogen-pressure dependences of the loss increase due to hydroxyl group formation is evaluated from the experimental results. The loss increase at 1.3- and 1.5-μm wavelength band at room temperature are estimated.     

Absorption loss in optical fibres due to hydrogen

It is shown that OD formation in optical fibres due to the deuterium molecule can become a barrier to OH formation in optical fibres exposed to hydrogen, although it cannot be a barrier to the absorption due to the hydrogen molecule in a fibre. The mechanism is discussed.     

Effects of hydrogen diffusion on optical fibre loss increase

The time dependence of fibre loss increase due to hydrogen diffusion for different pressures and temperatures is reported. It is found that the optical fibre loss increases with increasing hydrogen pressure as well as temperature, and decreases with increasing temperature when removed from the hydrogen environment.     

Germanium-dopant effect on hydroxyl loss increase in optical fibers

The germanium-dopant effect on hydroxyl loss increase in optical fibers is studied experimentally. The distribution profile of hydroxyl absorption which is caused by hydrogen diffusion is measured for GeO2-doped silica glasses. From the experiment, it is found that the distribution profile of induced hydroxyl absorption is similar to the GeO2concentration profile. Moreover, the absorption loss increases due to hydrogen diffusion are measured for GeO2-doped silica fibers. From the experiment, it is concluded that the induced molecular hydrogen loss as well as the induced hydroxyl loss increases with an increase in the GeO2concentration.     

Long-term loss stability of single-mode optical fibres exposed to hydrogen

The rate of increase in loss in single-mode optical fibres exposed to hydrogen at temperatures up to 150°C has been determined. Extrapolation down to ambient temperature of effects other than that due to interstitial hydrogen indicates that slow long-term loss increments at 1310 nm will remain less than 0.02 dB/km after 25 yr at 20°C in one atmosphere of hydrogen.     

Estimation of long-term transmission loss increase in silica-basedoptical fibers under hydrogen atmosphere

The irreversible loss increase in silica-based optical fibers due to hydrogen is discussed on the basis of results of various high-temperature tests. The results show that germanium-doped-core fibers have different behavior with respect to irreversible loss increase, and that a pure-silica-core fiber fabricated under optimum conditions is very stable against irreversible loss increase. The estimation of long-term transmission loss stability is also discussed, and high-temperature testing is certified to be effective for estimating the long-term loss stability under low temperature     

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.     

?-ray irradiation effect on transmission loss for ZrF4-based optical fibres

The ?-ray irradiation effect on the transmission loss of ZrF4-BAF2-GdF3-AlF3 and ZrF4-BaF2-GdF3-AlF3-PbF2 optical fibres is investigated. Absorption bands are induced in the ultraviolet to near infrared region, and their tails increase the transmission losses in the mid-infrared region. Induced transmission losses for a dose of 106 R are 1000?2300 dB/km in the 2?4 ?m band. These values are comparable to those at 1.5 ?m for doped silica fibres.     

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.     

Attenuation changes in optical fibres due to hydrogen

The attenuation in an optical fibre due to dissolved hydrogen has been studied experimentally and theoretically as a function of time as the hydrogen is allowed to escape. The agreement confirms that the hydrogen is in molecular form and that the diffusion constant is 1 5×10?11 cm2/s at room temperature.     

Radiation-induced loss and colour-centre concentration in optical fibres

The number of colour centres generated by gamma radiation has been measured with the ESR method; radiation-induced loss was obtained during the steady-state irrediation. By comparing these data, the induced loss in Ge/P-doped GI fibres corresponding to one colour centre is estimated to be 5.5 × 10?15 dB/km.     

Prediction of loss minima in infra-red optical fibres

Loss minima in two fluoride glass and chalcogenide glass fibres were calculated. The intrinsic losses are predicted to be 1 × 10?3 dB/km at 3.4 ?m for BaF2-GdF3-ZrF4 glass fibre, 1 × 10?2 dB/km at 2.7 ?m for BaF2-CaF2-YF3-AlF3 glass fibre and 1 × 10?2 dB/km at 4.5 ?m for GeS3 glass fibre.     

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.     

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.     

Effect of dopants on transmission loss of low-OH-content optical fibres

We formerly developed very-low-OH-content optical fibres consisting of a borosilicate cladding and a phosphosilicate core. The transmission loss of the fibre was 0.47 dB/km at 1.2 ?m. We have further investigated the effects of dopants in pure silica on the losses of fibres. The letter clarifies the effects of dopants on the loss in the near-infrared region.     

Effective index drift from molecular hydrogen diffusion inhydrogen-loaded optical fibres and its effect on Bragg gratingfabrication

When hydrogen loading is used to enhance the photosensitivity of silica-based optical waveguides and fibres, the presence of molecular hydrogen dissolved in the glass matrix changes the effective index of propagation of guided optical modes by as much as 0.05%. Real-time monitoring of the reflectivity spectrum of Bragg gratings written in such conditions shows that the centre wavelength follows the changes in hydrogen concentration due to diffusion and reaction with glass defects     

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.     

Hydrogen-induced loss increases in germanium-doped single-mode optical fibres: long-term predictions

A spectrally broad loss increase occurs in GeO2-doped optical fibres exposed to hydrogen at elevated temperatures. This is the primary H2-induced loss mechanism in GeO2-doped single-mode fibres for temperatures above 20 C. Loss increases at 1.3 and 1.55 ?m are predicted to be less than 0.01 dB km after 20 years.     

Optical loss change caused by hydraulic pressure in multimode optical fibres

The optical loss change caused by hydraulic pressure in a multimode plastic-coated fibre with a buffer layer was examined. The relationship between loss change and fibre dimensions was found. A large-outer-diameter fibre exhibits a small change in the optical loss caused by hydraulic pressure.