Abstract: A method and apparatus for testing a data path in a network is described. The method may comprise creating a closed loop in the data path so that test data (e.g., fixed set of known data) sent from a local network device to a downstream network device is returned by the downstream network device. Thereafter, the test data is injected into the closed loop and selectively extracted from the loop. The test data may then be processed. The method may create the closed loop by closing a first loopback mechanism at the local network device and closing a second loopback mechanism at the downstream network device. In an example embodiment, the method determines whether the identified errors exceed a threshold number of errors. The method may be utilized to determine if fiber connectivity of the data path has failed when the identified errors exceed the threshold.