This document presents a troubleshooting guide for fiber optic cables once deployed and in regular use. It also includes a list of common fault location items. Maintenance personnel can refer to this document for step-by-step troubleshooting whe. This document presents a troubleshooting guide for fiber optic cables once deployed and in regular use. It also includes a list of common fault location items. Maintenance personnel can refer to this document for step-by-step troubleshooting when dealing with faults arising from the following sources.The table below presents a selection of commonly used tools, instruments, and equipment. Instruments and equipment from different brands have distinct characteristics and functions. Please refer to the following table to get more information.The table below presents the primary faults of fiber optic cables. By employing an enumerative method based on the collected fault information, the fault can be comprehensively determined. Please refer to the following table to get more information.Fault localization can be confirmed through replacement testing using the control variable method. The following measures correspond to different fault scopes and types for fault localization:For the issues listed above, if verified by the user or through FS tests, the following methods can be employed to exclude the fault.