A technique for detecting a fiber fault in a WDM optical access network includes launching a test signal into a fiber trunk line linking a central office (“CO”) to a remote node (“RN”) of the WDM optical access network. The test signal is generated by an optical time domain reflectometry unit to simultaneously fault test fiber access lines linking the RN to customer premises. The test signal is separated from downstream WDM signals at the RN. The test signal is power split at the RN into a plurality of access line test signals. The access line test signals are each recombined with a corresponding one of the downstream WDM signals onto a corresponding one of the fiber access lines. Test signal reflections are received at the CO from the fiber access lines as a reflection signature and analyzed to identify a location of the fiber fault.