Fig. 2: Illustration of the time expansion.
From: Time-expanded phase-sensitive optical time-domain reflectometry
Magnitude of the traces detected using a a 40-Hz offset and b a 20-Hz offset. Insets show the details of several consecutive acquired traces, showing good repeatability. c SNR comparison of both measurements, showing a 3dB average increase for the smaller offset, as expected from the reduced acquisition bandwidth. These results show that the proposed method can expand the temporal duration of the trace, leading to a proportional increase in the SNR but with a loss in the maximum measurable acoustic bandwidth
