Optimised structure for preparing long ultra-low-loss single-mode fibres

An optimised structure has been evolved for producing long lengths of ultra-low-loss single-mode fibre. Attenuation figures of 0.6 dB/km at 1.3 ?m and 0.34 dB/km at 1.6 ?m have been achieved in fibres up to 17.1 km in length. The absorption due to OH impurity has been reduced to <3 dB/km at 1.39 ?m.     

Low-loss splicing of a 62.4 km single-mode-fibre link

A 62.4 km single-mode-fibre link containing 35 splices has been made in the laboratory using equipment and techniques suitable for landline installations. Mean splice attenuations of 0.1 dB at 1.3 ?m and 0.08 dB at 1.55 ?m were measured. The mean attenuation of the complete spliced link was 0.5 dB/km at 1.3 ?m and 0.34 dB/km at 1.55 ?m. In addition, the attenuations of 200 splices measured at 1.3 ?m are reported.     

New low-loss liquid-core fibre waveguide

Low-loss liquid-core fibre-optical waveguides having a transmission loss of 10 dB/km has been made using commercially available glass tubing. The loss is less than 20 dB/km over a wavelength range of greater than 0.8?1.1 ?m, and, at the semiconductor laser wavelength of 0.9 ?m, has a value of 14 dB/km. This is the first low-loss fibre to be made using glass.     

Low crosstalk polarisation-maintaining optical fibre with an 11 km length

An 11 km-long polarisation-maintaining optical fibre with crosstalk up to ?25.2 dB and ?22.5 dB at 1.30 ?m and 1.56 ?m, respectively, is presented. Transmission loss is 1.2 dB/km at 1.3 ?m and has a minimum value of 0.79 dB/km at 1.56 ?m.     

Fabrication of single-mode fibres by v.a.d.

A 21 km long single-mode fibre with loss values of 0.6 dB/km at 1.2 and 1.55 ?m, and 0.7 dB/km at 1.3 ?m, has been made by the v.a.d. method. This indicates the high potential of this method in the production of long low-loss single-mode fibres.     

Fabrication of low-loss and wide-bandwidth v.a.d. optical fibres at 1.3 ?m wavelength

A low-loss and wide-bandwidth optical fibre in the long-wavelength region has been fabricated by the v.a.d. method. Loss at 1.3 ?m is 0.98 dB/km and 6 dB down bandwidth is 1600 MHz km at 1.26 ?m.     

100 km single mode VAD fibres

100 km single mode fibres with low loss values of 0.3 dB/km at 1.55 ?m and 0.5 dB/km at 1.3 ?m have been made by the VAD method. Swept frequency 6 dB down bandwidths at the two wavelengths were 40 MHz for 100 km length and 800 MHz for 50 km length, respectively.     

Double-flame VAD process for high-rate optical preform fabrication

High-rate deposition techniques for the VAD process have been developed by increasing the size of synthesised fine glass particles by means of a new `double-flame burner?. VAD core preforms have been increased to 2500 g in size, from which a 580 km-length fibre with 50 ?m core diameter can be drawn. A deposition rate of 4.5 g/min from one burner has been attained. Fibres from high-rate deposited preforms exhibit transmission losses of 0.62 dB/km at 1.3 ?m and 0.44 dB/km at 1.55 ?m.     

Low-OH-absorption fluoride glass infra-red optical fibres

Ultralow losses of 10?2 to 10?3 dB/km have been predicted in fluoride glass optical fibres between 2 and 4.5 ?m. At 2.9 ?m, in the central part of this spectral region, the OH? ion presents its fundamental stretching vibration which gives rise to a strong and broad absorption. The attenuation at 2.9 ?m in a step-index fluorozirconate glass fibre has been brought down to 58 dB/km, by reducing the OH? concentration in the glass. It is the lowest attenuation yet reported at this wavelength in any optical fibre.     

High-?n, small-core single-mode fibres for efficient nonlinear optical effects

High-?n, small-core single-mode fibres have been fabricated with the VAD method. Results have been obtained for fibres having cores of ?n = 2.9% and diameter = 2.3 ?m and ?n = 1.9% and diameter = 2.8 ?m. Minimum losses for a ?n = 2.9% fibre and a ?n = 1.9% fibre are 0.82 dB/km at 1.61 ?m and 0.68 dB/km at 1.62 ?m. Other fundamental properties have been measured.     

3 km-long single-polarisation single-mode fibre

A single-polarisation single-mode (SPSM) fibre with crosstalk of ?40 dB in a 3.2 km length has been demonstrated. No crosstalk degradation was found for lengths of more than 0.2 km. The two polarisations of the fundamental mode were split with a high modal birefringence of 8.5×10?4, which was produced by PANDA structure. The transmission loss was 2.8 dB/km at 1.56 ?m.     

Spectral losses of low-OH-content optical fibres

Very-low-OH-content optical fibres consisting of borosilicate-cladding phosphosilicate-core have been produced by a chemical vapour deposition technique. One of the fibres, whose transmission loss was less than 1 dB/km between 0.95 and 1.37 ?m, showed a minimum loss of 0.47 dB/km at 1.2 ?m.     

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.     

Design and fabrication of dispersion-shifted depressed-clad triangular-profile (DDT) single-mode fibre

A new depressed-clad triangular-index-profile single-mode fibre with dispersion minimum shifted to the 1.55 ?m region is investigated. Fibres with high cutoff wavelength (?1.1 ?m) and low dispersion slope (?0.052 ps/km nm2) at their minimum dispersion wavelength (?1.55 ?m) were fabricated. Results from 226.7 km of fibre show an average loss of 0.241 dB/km at 1.55 ?m and 0.232 dB/km at the loss minimum.     

Low-loss single-mode fibres prepared by plasma-enhanced MCVD

A series of single-mode lightguide preforms capable of yielding > 20 km of 110 ?m OD fibre have been fabricated using the RF plasma-enhanced MCVD technique. The loss of kilometre lengths drawn from both ends of the preforms has been measured. At 1.3 ?m, the loss ranged between 0.55 and 0.7 dB/km. The preforms were made at deposition rates of 3.5 g/min.     

Low loss and low OH content soda-lime-silica glass fibre

Low loss soda-lime-silica glass fibres of minimum loss of 4.23 dB/km at 0.85 ?m were prepared with 6.5 dB/km extra absorption loss due to OH radicals at 0.97 ?m. The loss factors were analysed from the impurity contents and scattering loss. These fibres have been developed by unique preparation techniques of wet mixing of raw materials and dry gas flow at glass melting.     

Tunable fibre Raman oscillator in the 1.32?1.41 ?m spectral region using a low-loss, low OH? single-mode fibre

We report the first tunable fibre Raman oscillator in the 1.32?1.41 ?m spectral region using a 1 km-long low-loss (0.32 dB/km at 1.32 ?m) and low OH? (1 dB/km at 1.39 ?m) single-mode fibre as the nonlinear medium, and a CW mode-locked Nd: YAG laser at 1.32 ?m as the pump source.     

OH-absorption in fluoride glass infra-red fibres

The OH fundamental peak absorption at 2.87 ?m has been reduced in fluoride fibres to less than 20 dB/km. By measuring the difference spectra between low and high peaks, the OH-peak shape has been measured over two orders of magnitude, and the results indicate that the optimum low-loss window occurs at 2.55 ?m in these materials.     

Transmission properties of 30.4 km v.a.d. fibre

A 30.4 km graded-index fibre has been fabricated by the vapour-phase axial deposition (v.a.d.) method. Optical-time-domain reflectometry was used to characterise the loss uniformity along the longitudinal direction of this fibre. Measured transmission loss and 6 dB bandwidth with good uniformity along this long fibre were 0.54 dB/km and 1200 MHzkm at the 1.3 ?m wavelength, respectively.     

Low-OH MCVD fibres without a barrier layer using OH ? OD-exchanged substrate tubes

The effect of deuteration (OH ? OD exchange) of the MCVD substrate tube on the absorption loss in fibres was studied using tubes of moderate and low OH content. The OH absorption at 1.39 ?m was reduced from 4 dB/km and 0.9 dB/km to 1 dB/km and 0.7 dB/km, respectively, in fibres made without a barrier layer using deuterated tubes.