COTDR performance optimization for amplified transmission systems

Abstract

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 between 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 penalty is negligible if a high speed polarization scrambling is used and the launched power per wavelength is kept below +2 dBm.