Service quality standards is represented by SLA (Service Level Agreement). One way to improve the SLA is to minimize service downtime. This downtime is called with TTR (Time to Repair) which is an FMS (Fault Management System) performance indicator. The lower TTR values, the better the FMS performance. This research discuss the performance improvement by evaluating FMS business process, determine the components that lead to system failure, measure the value of a system failure probability with changes in the composition of its components, and obtain business process that improve FMS performance. FMS business process is represented in SOP of fiber optic fault handling process. MC (Markov Chain) method is used to determine the level of FMS business process performance for each process from open ticket to closed ticket. FTA (Fault Tree Analysis) method is used to determine the probability of system failure for various components composition in the FMS. The purpose of this method is to get a system that has a minimum system failure probability. The new system is then re-tested for its performance using MC method. With both methods we can obtain business process models that can improve the performance of FMS PT. XYZ up to 92.64%.