US Patent 7826378 PON with distributed virtual port loopback

A passive optical network (PON) access network connected to an external data network can be tested using a remote test host operating on the external data network by looping test data from the test host through the PON to an Optical Network Terminator (ONT), through a data path between an ONT test port and an ONT user port, and back through the PON to the test host. Data tunneling is used to route the data through the external data network between the test host and the PON Optical Line Terminal (OLT). The invention can be used to emulate downstream as well as upstream PON traffic for remote diagnostic testing or other purposes.