Coherent optical frequency-domain reflectometer based on a fibre laser with frequency self-scanning

The first results of an experimental study of a coherent optical frequency-domain reflectometer (C-OFDR) based on a simple single-frequency fibre laser with frequency self-scanning are presented. The self-scanning laser generates microsecond pulses, and its lasing frequency changes linearly with a change in the pulse number without using any actively tuned elements. In addition, the generation of each pulse occurs on only one longitudinal mode with a linewidth less than 1 MHz. This laser is characterised by a high linearity of frequency tuning, due to which reflectograms can be measured without any additional spectral correction. The C-OFDR demonstrates a possibility of attaining a spatial sampling of ∼200 μm and a reflectance sensitivity of approximately down to-80 dB at a test line length of ∼9 m.