Using a Semiconductor Laser with Frequency Capture as an Operating Optical Generator of a Coherent Reflectometer for Distributed Vibration Frequency Measurements

A standard distributed feedback semiconductor laser that is self-stabilized through the frequency capture effect of an external fiber ring resonator is able to replace the standard reference oscillator of a coherent reflectometer in the system of a distributed fiber vibration sensor. A direct comparison of the signal-to-noise ratio, as measured in configurations with a semiconductor and reference master oscillator, has been carried out for quantitative assessment of the ability of the system to restore the frequency spectrum of vibrations. Distributed measurements of vibration spectra with frequencies up to 5600 Hz and a spatial resolution of 10 m when performed on an optical fiber at a distance of ~3500 m show a signal-to-noise ratio above ~8 dB for both configurations. The difference between the configurations was less than 2 dB over the entire spectral range.