Cancellation of reference update-induced 1/f noise in a chirped-pulse DAS.

Distributed acoustic sensors (DAS) perform distributed and dynamic strain or temperature change measurements by comparing a measured time-domain trace with a previous fiber reference state. Large strain or temperature fluctuations or laser frequency noise impose the need to update such a reference, making it necessary to integrate the short-term variation measurements if absolute strain or temperature variations are to be obtained. This has the drawback of introducing a 1/f noise component, as noise is integrated with each cumulative variation measurement, which is detrimental to the determination of very slow processes (i.