Novel scanning method for distortion-free BOTDA measurements
AuthorsDomínguez López, Alejandro; Zhisheng, Yang; Soto Hernández, Marcelo Alfonso; Angulo Vinuesa, Xabier; Martín López, Sonia; [et al.]
IdentifiersPermanent link (URI): http://hdl.handle.net/10017/26277
Optical Society of America
Ministerio de Economía y Competitividad
Comunidad de Madrid
Optics Express, 2016, v. 24, n.10, p. 10188-10204.
Fiber optics sensors
info:eu-repo/grantAgreement/MINECO/TEC2013-45265-R/ES/DETECCION TEMPRANA DE AMENAZAS PARA INFRAESTRUCTURAS CRITICAS USANDO SISTEMAS DISTRIBUIDOS DE FIBRA OPTICA/
info:eu-repo/grantAgreement/Comunidad de Madrid//S2009%2FMIT2790/ES/Sensores e INstrumentación en tecnologías FOTÓNicas/SINFOTON
info:eu-repo/grantAgreement/EC/FP7/307441/EU/Ubiquitous optical FIbre NErves/U-FINE
Systematic errors induced by distortions in the pump pulse of conventional Brillouin distributed fiber sensors are thoroughly investigated. Experimental results, supported by a theoretical analysis, demonstrate that the two probe sidebands in standard Brillouin optical time-domain analyzers provide a non-zero net gain on the pump pulse, inducing severe distortions of the pump when scanning the pump-probe frequency offset, especially at high probe power levels. Compared to the impact of non-local effects reported in the state-of-the-art, measurements here indicate that for probe powers in the mW range (below the onset of amplified spontaneous Brillouin scattering), the obtained gain and loss spectra show two strong side-lobes that lead to significant strain/temperature errors. This phenomenon is not related to the well-known spectral hole burning resulting from pump depletion, but it is strictly related to the temporal and spectral distortions that the pump pulse experiences when scanning the Brillouin gain/loss spectrum. As a solution to this problem, a novel scanning scheme for Brillouin sensing is proposed. The method relies on a fixed frequency separation between the two probe sidebands, so that a flat zero net gain is achieved on the pump pulse when scanning the pump-probe frequency offset. The proposed technique is experimentally validated, demonstrating its ability to completely cancel out non-local effects up to a probe power ultimately limited by the onset of amplified spontaneous Brillouin scattering. The method allows for one order of magnitude improvement in the figure-of-merit of optimized long-range Brillouin distributed fiber sensors, enabling measurements along a 100 km-long sensing fiber with 2 m spatial resolution and with no need of added features for performance enhancement.