Wavelength-dependent transmission at fibre connectors

It is shown that the transmission loss of a fibre connector with a preceding fibre is extremely wavelength-dependent. A change of laser wavelength by only 0.01 ? may suffice to change the transmission by 10% when using typical multi-mode fibres.     

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.     

Bandwidth and loss measurements of graded-index microstructured polymer optical fibre

The first bandwidth measurements of graded-index microstructured optical fibres are presented, demonstrating that this novel fibre geometry can provide high-bandwidth multimode polymer fibres without the need for complex doping techniques as with conventional polymer fibres.     

Relation between splice loss and mode conversion in a graded-index optical fibre

To design an optical-transmission-line system, transmission characteristics of splices made by arc-fusion and V-groove methods were investigated experimentally for a graded-index optical fibre. It was found that the splice made by the arc-fusion method had a larger mode conversion than the splice made by the V-groove method for the same loss.     

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.     

Pulse response of a graded-index optical fibre

An analysis has been made of pulse dispersion in an optical fibre having a continuous radial variation of refractive index. Solutions are presented for Selfoc fibre showing the effects of mode and material dispersion and of group delay. The predicted dispersions range from very low values up to about 1 ns/km, depending on the launching conditions.     

Wavelength-dependent differential modal delay in graded-index fibres

We present a technique for measurement of wavelength-dependent differential modal delay in a graded-index fibre. The data are used to derive the excitation-dependent zero-dispersion wavelength. The method offers an accurate calibration procedure to determine the zero-material-dispersion wavelength for given dopant concentration.     

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.     

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.     

Mode dependence of splice loss in graded-index optical fibers

Various measurements of the mode dependence of loss in fusion splices are presented. Both laser diodes and light-emitting diodes are employed as sources and measurements are made using both the cutback method and the backscattering technique. Empirical relations, quantifying the form of the mode dependent loss function, are derived and discussed.     

Continuous measurement of optical fibre transmission loss characteristics during drawing process

An online measurement method using an optical rotary connector is proposed for continuously monitoring optical fibre loss characteristics during manufacture. This method provides a complete transmission loss spectrum and OTDR measurements of optical fibres during the drawing process. The results coincide with corresponding offline cutback measurements to better than ±0.2 dB/km.     

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.     

Ten-channel coherent optical fibre transmission

A laboratory ten-channel coherent fibre-optic broadband transmission system is reported. The frequency-division-multiplexed optical carriers are separated by 6 GHz and are demultiplexed by a tunable heterodyne receiver having a sensitivity of -46 dBm at a bit error rate of 10-9. In this system a maximum number of 64 channels can be installed.     

Optimum profile parameter on graded-index optical fibre at 1.27 ?m wavelength

The optimum profile parameter on germanium phosphosilicate graded-index optical fibres at 1.27 ?m wavelength is examined experimentally and is found to be 1.88 ± 0.01. Graded-index optical fibres that simultaneously possess high transmission bandwidth (in excess of 1 GHz km) and attenuation below 1 dB/km are obtained.     

Hydraulic pressure dependence of optical loss in jacketed optical fibre

Hydraulic pressure dependence of fibre loss is examined for several jacket structures. It is found that a liquid-filled pipe structure exhibits small loss increase, 0.9 dB/km at a pressure of 500 kg/cm2, and is promising for use in a submarine optical cable     

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。     

OH absorption-induced loss in tapered singlernode optical fibre

Observation of the OH induced absorption loss near 1.39 μm in optical fibres tapered using a flame brushing technique is reported. The induced loss is experimentally analysed in terms of tapering conditions, fibre type, and annealing conditions. Impacts of the OH induced loss on fused taper fibre devices are discussed     

Digital fibre transmission using optical homodyne detection

Homodyne detection of a 140 Mbit/s PSK signal transmitted over 30 km of cabled fibre has been achieved using a balanced optical phase-locked-loop receiver. System phase error was dominated by the laser frequency instability and not the cabled fibre.     

FM-AM noise conversion in dispersive single-mode fibre transmission lines

It is shown that a considerable FM-AM-noise conversion occurs in dispersive fibre-links which must be taken into account when designing analogue subcarrier distribution systems. For a link-length of 10 km at lambda =1.55 mu m, RIN-values between -125 and -145 dB/Hz are expected for frequencies between 1 and 10 GHz.<>