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Quasi-distributedmeasurement of strain and/or temperature is often implemented using arrays of weakly reflecting fiber Bragg gratings (FBGs)whose reflection peaks are centered at the same nominal wavelength. The signals are obtained bymeasuring the phase difference between the reflections of consecutive FBGs. Typically, in such a system, the spatial resolution of the interrogatormust be compatible with the spatial separation between consecutive FBGs. Insufficient resolution leads to an overlap of reflection peaks, a decrease in the differential-phase signal and poor sensitivity. In this paper, we study the use of two different sparsity basedmethodologies for improving the sensitivity of such quasi distributed acoustic sensing systems in the casewhere traditional signal processing approaches do not provide sufficient spatial resolution. Thesemethods enable relaxing the requirements regarding the interrogator or, alternatively, reducing the needed separation between reflectors. Experimentally, these techniques were used tomeasure 1 kHz dynamic strain induced in a fiber segment between two discrete reflectors, located at the end of a 4 km longfiber. The separation between the reflectors was 18mwhile the pulse (spatial)widthwas intentionally chosen bigger than that. It yielded approximately 5 dB increase in themeasured signal compared to the traditional processing approach and an order ofmagnitude improvement in the sensitivity,~ m 0.9 rad Hz .

Sparse recovery methodologies for quasi-distributed dynamic strain sensing