High-reflectivity-resolution coherent optical frequency domain reflectometry using optical frequency comb source and tunable delay line.

We propose a high-reflectivity-resolution coherent optical frequency domain reflectometry (OFDR) with a novel scheme of delay shift averaging (DSAV) by using an optical frequency comb source and a tunable delay line to suppress the fading noise. We show theoretically and experimentally that the novel DSAV scheme is equivalent, in realizing a high reflectivity resolution, to our previously reported frequency shift averaging (FSAV) of the same number of teeth of the optical frequency comb [1], but does not need the expensive narrow-pass-band tunable optical filter required in the previous scheme. Furthermore, by using this new method in combination with FSAV, better reflectivity-resolution is obtained compared to using only conventional FSAV with a single-wavelength laser source.