Fig. 1.

(a) Raw optical coherence tomography (OCT) data consist of 1024 radially directed A-scans per B-scan and 541 B-scans in the $z$ direction, covering $541*100\mu \mathrm{m}=54.1\mathrm{mm}$. (b) 16 A-scans and 5 B-scans were averaged to smoothen the data, resulting in 31 radial averaged A-scans and 108 B-scans over the 54.1 mm length. (c) Savitzky-Golay filter was applied to smooth the A-lines. (d) The first 90 data points were removed from each averaged A-scan to remove scattering properties from the probe itself. (e) Attenuation analysis was performed over first 50 points after the maximum of the resulting curve (red part).