OTDR performance enhancement using a quaternary FSK modulated probe and coherent detection

This letter proposes a new approach to enhance the performance of optical time domain reflectometry (OTDR). This approach employs a probe signal modulated in a quaternary frequency-shift-keying (FSK) format and a coherent detection technique. Experiments show that the proposed approach reduces the measurement time to one fourth without sacrificing dynamic range and spatial resolution on a 1100-km-long transmission line with optical amplifiers.<
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