For the practical use of the carbon slider on Shinkansen cars, a system to detect the damage of pantograph has been studied. The method to detect the breakdown of the optical fiber made of plastics provides a low cost system. Therefore, a detecting device and a new type insulater with optical fibers were manufactured and tested. The results show that the system is convenient for practical use. It was confirmed from filed tests that the heat characteristics of the optical fiber is sufficient for practical use.