Fig. 5: The strain change demodulation process.
From: Single-shot BOTDA based on an optical chirp chain probe wave for distributed ultrafast measurement
a The demodulation flow chart based on a twice-correlation algorithm; ⋆ represents the cross-correlation operator. b The reference BGS and the random BGS are processed by this algorithm, resulting in two symmetrical profiles. c The demodulated BFS changes along the 50-m PMF. d Change in BFS versus change in strain
