Theoretical fatigue life of helically stranded optical fibres

摘要

The design of optical fibre cables currently preferred by BICC ordinarily produces little or no tension or torsion in the fibres. Bending them into helical form, however, causes a permanent stress which couid give rise to static fatigue. In a recent paper, the probability that a bent fibre will fail owing to static fatigue was calculated. The calculation is extended in the present paper to take account of proof-testing. Assuming reasonable values for the parameters, it appears that a fibre of 125μm diameter, proof-tested at 0.5 strain and subsequently bent to a radius not less than 25 mm, would certainly survive for 40 years