Abstract

Introduction: It is expected that, over the next decade, large quantities of optical fibre cable will be installed into the British Telecom inland long haul telecommunications system. Most of this cable will be installed into underground duct. Fibre in this system is required to have a lifetime of 20 years or more. Fibre life is greatly influenced by humidity and residual strain. Moisture ingress can be controlled by an aluminium-polyethylene laminate (APL) water barrier in the cable, but little is known about residual fibre strain levels in the ground. The level of residual strain is required as an input to any realistic calculation of fibre lifetime from stress corrosion effects.