High-resolution OFDR with incorporated fiber-optic frequency encoder

A high-resolution optical frequency-domain reflectometer (OFDR) which employs the frequency sampling method is reported. The auxiliary interferometer for generating the clock pulses at equally spaced light frequencies is incorporated into the main interferometer to simplify the system configuration and to reduce the effect of different environmental perturbations occurring at the two interferometers. 180-MHz frequency sampling is shown to give an 850- mu m spatial resolution and -80-dB minimum detectable reflectivity through the use of a DFB-LD with 180-GHz nonlinear chirp.<
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