The Effect of Lightning Rod Grounding on the Operation of Underground Fiber-Optic Communication Lines

Abstract Fiber-optic communication lines laid underground near grounded objects may be exposed to lightning currents flowing from the grounding conductors of these objects. Lightning discharge and its electromagnetic radiation can alter the polarization state of the signal transmitted over the communication line and interfere with its operation. Experiments on a physical model have shown the possible inefficiency of a lightning rod when it is grounded in soils with high resistivity: a discharge from a high-voltage electrode may be not intercepted by a rod lightning rod model and hit a well-grounded metal structure located at a depth through the upper layers of the soil. Thus, when laying underground fiber-optic cable lines in the ground with high resistivity, it is necessary to take into account the possibility of lightning orientation on the metal armor of the cable itself or on metal structural elements located near the cable. In addition, currents flowing through grounding devices can indirectly affect underground communication lines, creating an intense electromagnetic field. An increase in the electric field strength can lead to a rotation of the plane of polarization of the transmitted signal and, consequently, interference in the operation of the communication channel.