Fig. 6: Perturbation detection.
From: Brillouin expanded time-domain analysis based on dual optical frequency combs
a Distributions of νB with and without heating current in a 2 cm test section of the FUT, focusing on the hotspot position. The inset show the zoomed view on the hotspot (dotted circle). b BGS comparison at the center of the hotspot with and without heating current. c Deviation of νB in the plots of repeated measurements. The standard deviation σ is calculated to be 1.2 MHz
