Fabrication of long-length high-strength single-mode silica fibres

The letter reports an alternative approach to the realisation of long, low-attenuation, high-strength single-mode optical fibres suitable for high bit-rate transmission over long distances in adverse environments. We show that low attenuation (less than 0.45 dB km) can be achieved in combination with high proof-test levels (1% ¿ 2% strain) in fibre lengths greater than 5 km, using natural fused-quartz tubing, and report a 15 km fibre having an attenuation of 0.44 dB km which survived a proof test at 1% strain.