Criterion for subpulse-length resolution and minimum frequency shift in distributed Brillouin sensors

We introduce a Rayleigh equivalent criterion to measure stressed section shorter than the spatial resolution of a distributed Brillouin sensor. Under this criterion for the worst-case of any given sensing length, the minimum resolvable strain length is 1/2 of the pulse length (w) with Brillouin frequency uncertainty of 5% or 0.8w with 2% frequency uncertainty. This is smaller than the pulse length.