A method for monitoring a passive optical network, the passive optical network comprising a plurality of network components, comprises receiving an alert message (200) from a fault detection system associated with the passive optical network, the alert message comprising an indication of one or more candidate locations for a detected fault in the passive optical network. The method further comprises accessing an inventory (202) of the plurality of network components, the inventory storing, for each of the plurality of network components, information comprising the network component location. The method further comprises identifying (204), based on the one or more candidate locations and the network component locations, one or more network components of the plurality of network components as candidates for the cause of the detected fault.