In literature, I find that both distributed acoustic sensing (DAS; for dynamic strain measurement) and distributed strain sensing (DSS; for static strain measurement) using methods on the basis of Rayleigh backscattering. Both obtain strain from comparing a reference and a target. I wonder what is the difference between them.
Thank you.
Dear Johnny Zhang ;
very good question.. pleas to check link below paper, may be usefull for you..
https://pages.mtu.edu/~scarn/teaching/GE4250/scattering_lecture_slides.pdf
I think the main point is the time response. As per dynamic strain, the strain usually varies fast which can be detected by a high-speed acoutic sensor (e.g. DAS ) while the static strain sensor would take long time for processing (e.g. OFDR).
Thank you, Liang Zhang. As your answer, a DAS tool can be used to detect static strain. However, the accuracy and resolution is low (even not quantitative). Why?@
Thank you for your answer, Vincent.
For example, if both DAS and DSS using the same OTDR and the same fiber, can I say they have same intrinsic sensitivity? The apparent sensitivity depends on the time windows?
By my oppinion some DAS systems provide the distributed vibration spectra, without obtaining of accurate values in microstrains, but DSS should provide it more precisely, but in static mode. In both cases the reference and the target have difference in phase.
Yuri, thank you for your answer. So can I think the DSS and DAS actually use the same method, but what is the difference making they have different accuracy and speed?
Johny, it depends also on domain of registration. Say, a part of DSS systems are based on OFDR principles, it is not pulsed like phase OTDRs for DAS applications, but sweeps in optical frequency, so such schemes strongly differs. Anyway they both use coherent light and work as interferometric sensors. But please note that some OTDRs (but not OFDRs) for strain sensing use incoherent light. So in all these cases setups differ.
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