The present version of IEEE Standard 1138  gives no guidance regarding the possible damage to OPGW from exposure to lightning. Industry experience with conventional overhead ground wires has settled on an overall diameter in excess of 12 mm for good long-term mechanical performance. This may not be enough to protect optical fibers from long-term damage. Test specifications, using the existing body of knowledge for calculation of lightning tripout rates, can be derived from existing practice in IEEE Standard 1243 , supplemented by empirical fits to observations of the distribution of total flash charge as measured by Berger . Test procedures can also be recommended, based on practical experience obtained using a variety of approaches that include IEEE Standard 4  and IEC 60794 .