COTDR PERFORMANCE OPTIMIZATION FOR AMPLIFIED TRANSMISSION-SYSTEMS

Two different cross-coupling schemes that allow coherent optical time- domain reflectometry (COTDR) on an amplified transmission system have been tested. A COTDR dynamic range of 109 km (56 km) with a coupling b etween the upstream repeater output to the downstream repeater input ( output) has been demonstrated on a 900-km test-bed. When the data are launched in both directions at the same wavelength, the impact of the coherent Rayleigh noise on the transmission has been evaluated. The pe nalty is negligible if a high-speed polarization scrambling is used an d the launched power per wavelength is kept below +2 dBm.