Measurements on jointed optical-fibre cables for the Slough¿Maidenhead field trial

It is not easy to predict the attenuation of the jointed cables making up a repeater length from measurements performed on the fibres in kilometre lengths of cable. A comparison is made of the attenuation values obtained by summing the values from single kilometre length measurements made using three different launch conditions and attenuation values obtained from direct measurements made as ten lengths of cable were jointed into and broken down from multikilometre lengths. One of the launching conditions is shown to overestimate by only a small amount of the attenuation of the jointed lengths of fibre. Attenuations and bandwidths were measured on cables before and after jointing in lengths up to 10.5 km. The results obtained under different test conditions are analysed and predictions of cumulative attenuation and bandwidth are made.