Construction of OPGW cable depends on the electrical and mechanical characteristics of existing alignments and will be different for different power line voltages, fault current, and span lengths, etc. The cable contains optical fibers for data transmission and telecom purpose optical fiber unit and the cable armoring. Furthermore this specification contains information concerning the quality assurance during manufacturing, the final accepta ce tests. An optical fiber composite overhead ground wire (OPGW) is a new type of ground cable used in the high-voltage power transmission system that serves as both a conventional overhead ground cable and a communication optical cable. Prysmian never has a pre-determined answer to a challenge – instead. Optical Fiber Overhead Ground Wire (OPGW) 1. How to calculate the required fault.