Long term attenuation measurements on optical ground wires

The attenuation stability of optical fibres integrated in optical ground wire (OPGW) cables over temperature and time is of paramount importance in the planning of long distance links. We report here a mean thermal attenuation dependence of 5.5/spl middot/10/sup -5/ dB/(km/spl middot//spl deg/C) at 1550 nm, on a 220 km span of dispersion shifted (DS) fibres of an installed OPGW cable. This optical link is installed in the James Bay region over a 735 kV power line where temperature varies from -40/spl deg/C to +30/spl deg/C annually. The data sample presented covers 1.5 year starting December 1993. During that period, we also observed a temporal evolution of the attenuation described by the empirical relation A=A/sub 0/ (t-t/sub 0/)/sup 0.00394/.