OTDR system using Raman amplification of a 1.65µm probe pulse

A technique for increasing the dynamic range of a 1.65 µm OTDR system has been demonstrated. This is achieved by Raman amplification of the 1.65 µm pulse within the sensing fibre using a co-propagating 1.53 µm pulse generated from a Q-switched erbium doped fibre laser. An increase in dynamic range of 17.5 dB has been demonstrated, providing an OTDR trace over 100 km on the test fibre.