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A method of increasing the range of 1.65Ám long range OTDR system based on Raman amplification
H.H.Kee, G.P.Lees and T.P.Newson
Optical Time Domain Reflectometry (OTDR) is an efficient and reliable technique for locating fibre faults and determining the loss distribution along the fibre. An OTDR system operating at a wavelength of 1.65μm is more sensitive to fibre macro-bending and micro-bending losses than those at the region of 1.3/1.55μm, thus providing an early detection of system faults and reducing the risk of total system failure. The current limitation in the maximum dynamic range of OTDR systems is due to the low power of 1.65μm laser diodes. Raman amplification has been employed to amplify a 1.66μm laser diode pulse by 24.8dB before launching it down the end of a sensing fibre.
We propose a novel method of increasing the dynamic range of a 1.65μm OTDR system through the use of delayed Raman amplification within the sensing fibre. By delaying the pump pulse with respect to the OTDR pulse, amplification of the latter may be delayed by tens of kilometres.
12th International Conference on Optical Fibre Sensors Williamsburg USA 28-31 Oct (1997)
Copyright University of Southampton 2006