The lengths are determined by measuring between splice locations including allowances for racking at all manhole locations. Additional length to reach the splicing vehicle (truck or trailer) plus some minimum of excess cable should also be added. Optical fiber cables are tested for attenuation using the cut back method (TIA 455-78) or back reflection method (TIA 455-8). The cutback method is mainly used in test at the manufacturing facility and the back reflection method is normally used in the field and in the manufacturing facility for. Recommendation ITU-T L. 151 refers to the installation of optical fibre ground wire cable. It deals with the factors that should be considered in determining the characteristics of this type of cable, the apparatus that should be used, the precautions that should be taken in handling the reels, and. This Applications Engineering Note (AE Note) addresses estimating cable length or event distance using an optical time domain reflectometer (OTDR).