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.     

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.     

Low loss high-density optical cable with nylon-extruded fibre units

A low loss, highly dense cable containing nylon-extruded six-fibre units was examined. Suitable unit parameters were determined by measuring loss increases with lateral force and at low temperature. 216-fibre cable was manufactured using the nylon-extruded units, and cabling loss increase was found to be only 0.1 dB/km.     

Stress and temperature effects on optical loss increase for phosphor-doped silica fibre in the long wavelength region

Irreversible loss increase in the long-wavelength region is first observed for phosphor-doped silica fibres with silicone resin layer by applying the stress at high temperature. The loss increment becomes larger for longer wavelengths. Experimental results show that the loss increase is strongly dependent on stress and temperature.     

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.     

Optical loss increase in optical fibre coated with silicone resin containing Si?D

One possible origin of the loss increase phenomenon with heat treatment at 200°C (H2 evolution from the coating material) has been investigated, using optical fibre coated with silicone resin containing the Si?D group. Although OH absorption at 1.4 ?m increases with 200°C heat treatment, no OD peak is observed. It is suggested that silicone resin containing no Si?H and Si?CH2?CH2?Si groups is appropriate as a coating material as no H2 evolution is present.     

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.     

Photobleaching effect on visible-region loss increase for heat-treated optical fibres in a hydrogen atmosphere

The photobleaching effect on the visible-region loss increase due to hydrogen was observed for the first time by argon-ion laser light launching in fibres. A 660 nm fluorescence intensity reduction for the bleached fibres was also observed.     

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     

Optical loss measurement results on an experimental optical fibre submarine cable of 30 km length

A continuous length of 30 km optical fibre submarine cable was successfully manufactured and laid on the sea bed about 1000 m deep. After the sea trial of 17 months, the cable was recovered from the sea bed. No significant degradation was observed in the optical loss of the recovered cable.     

Leaky coaxial cable with adjustable coupling loss for mobilecommunications in complex environments

A new kind of leaky coaxial cable composed of an axially-slotted line covered with periodic metallic patches is proposed. The basic cable sets up a surface wave and does not radiate itself, but excites the patch apertures into radiation. The direction of the radiation field can be changed by adjusting the size and period of the patches according to the environmental application. A combined method that involves FDTD iteration and integration of the equivalent surface magnetic current is introduced in order to determine the radiation field accurately     

Dispersion of Verdet constant in stress-birefringent silica fibre

The Faraday effect in stress-birefringent silica fibre is discussed theoretically and measured experimentally. In the red and infra-red spectral range, the Verdet constant is found to be VH = 2.0 × 10?35 v2 rad/A, where v is the optical frequency in hertz.     

Measurement of strain relief in an experimental optical fibre cable

Optical cables made by helically winding loose-tubed fibres around a central member can be designed to tolerate different amounts of axial strain before the fibres are strained. Here an optical technique is used to measure the strain relief achieved in an experimental cable incorporating fibres tubed under different conditions. The results are in good agreement with the strain relief predicted from the cable geometry.     

The influence of a fibre structure on optical loss in a graded-index fibre

For designing a fibre structure, the influence of structural parameters on optical loss is investigated experimentally for a graded-index fibre. The fibre with large cladding/outer-layer index difference and small cladding thickness is found to have large excess loss near excitation points, such as a launching point and a splicing point.     

Temperature stability of transit time delay for a single-mode fibre in a loose tube cable

Transit time is measured as a function of temperature for a single-mode fibre installed in a loose tube cable structure. In the range from ?50°C to +60°C, the results indicate a positive linear slope of 6.7 ppm/°C, one of the lowest figures reported to date.     

A review of recent progress in holmium-doped silica fibre sources

In this paper we present a review of holmium-doped silica fibre based sources. We discuss recent demonstrations of an efficient cladding-pumped fibre geometry and the impact it has made on the power scaling of these sources. We discuss the wavelength region that is addressable by holmium-doped silica based devices and highlight the advantage over thulium-doped fibres in terms of atmospheric transmission. Finally we review the development and current status of the pulsed and CW operation of holmium fibre sources and discuss the future development potential of sources in the ns-fs pulse-width range.     

Simplified model for effect of Ge doping on silica fibre acoustic properties

A simplified model for the effect of Ge doping on the longitudinal acoustic modulus and acoustic damping coefficient of silica fibres is presented. The model provides the longitudinal acoustic velocity, Brillouin spectral width, and Brillouin gain coefficient as a function of the Ge concentration. The model only requires knowledge of high-level, easily-measurable physical properties of the bulk fictive materials. The model and experimental data were found to be in excellent agreement.     

Signal-level dependence in the recovery rate of irradiated plastic-clad silica fibre

The optical recovery of a plastic-clad silica fibre after gamma irradiation was monitored at a wavelength of 850 nm. The recovery rate over the measured range of 10 s to > 1 h was found to be strongly dependent on the signal power passing through the fibre.     

Temperature dependence of the Kerr effect in a silica optical fibre

The temperature dependence of the electro-optic Kerr effect has been measured in a silica-cored monomode optical fibre. The Kerr constant was measured as 5.3×10?16 mV?2 at 23°C with a temperature coefficient of +0.56% per deg C over the range 23 to 88°C. This measurement has implications for optical-fibre temperature and electric field sensors.