The invention describes a method, a communication system and a central communication unit (OLT) for detecting at least one faulty peripheral communication unit (ONU1, ..., ONUn) in a network system using a shared medium between the central communication unit (OLT) and the at least one peripheral communication unit (ONU1, ..., ONUn). Under the inventive method each peripheral communication unit (ONU1, ..., ONUn) is triggered to transmit a clocked signal towards the central communication unit OLT). It is determined whether the clock can be recovered from each transmitted signal. Subsequently, the at least one faulty peripheral communication unit (ONU1, ..., ONUn) is detected on the basis of the determination results. Furthermore, a transmission time slot during which the respective peripheral communication unit (ONU1, ..., ONUn) transmits the clocked signal may be allocated for each peripheral communication unit (ONU1, ..., ONUn).
展开▼
