A novel technique in BDG sensors: combination of phase and frequency correlation techniques
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A novel technique in BDG sensors: combination of phase and frequency correlation techniques Abdollah Malakzadeh1,2 · Mohsen Mansoursamaei2 · Rasoul Pashaie2 Received: 6 January 2020 / Accepted: 11 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This paper investigates a novel theoretical model based on Brillouin dynamic grating (BDG) sensors with ultrahigh spatial resolution over long sensing length. So far, frequency correlation or phase correlation technique is singly used to measure properties of the BDG sensors, although each of the techniques has its own drawbacks due to either low spatial resolution and short sensing length or processing complexities. We introduce a straightforward theoretical technique in BDG sensors based on the combination of phase and frequency correlations (CPFC) in a polarization-maintaining fiber. Correlation peak points in the CPFC technique are points where the correlation peaks in the phase correlation technique are matched with the correlation peaks in the frequency correlation technique. The spatial resolution in this novel technique is the same as the spatial resolution of the phase correlation technique. The peaks of the frequency correlation technique have no effect on the final spatial resolution of the CPFC technique and can only increase its sensing length. Long sensing length with no complexity and short calculation process are advantages of the CPFC technique. By simulation of this innovative theoretical technique, a 9 mm spatial resolution over 17.7 km sensing length has achieved, which to the best of our knowledge is the longest sensing length in millimeter range spatial resolution reported so far in BDG sensors. Keywords Distributed optical fiber sensor · Fiber sensors · Brillouin dynamic grating · Phase correlation technique
1 Introduction Distributed fiber sensors can be considered as millions of interconnected point sensors. The spatial resolution, sensing length, and response time are important parameters of sensors that different techniques used to improve them (Bao and Chen 2012; Malakzadeh et al. 2020a, b; Barrias et al. 2016). Among the distributed fiber sensors, Brillouin scattering based ones have often a higher spatial resolution (Bao and Chen 2011). * Abdollah Malakzadeh [email protected] 1
School of Astronomy, Institute for Research in Fundamental Sciences, Tehran, Iran
2
Physics Department, Iran University of Science and Technology, Tehran, Iran
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A. Malakzadeh et al.
Stimulated Brillouin scattering (SBS) is a nonlinear effect that arises from the interaction between the incident light and the acoustic waves in a nonlinear medium, causing the incident pump light to be backscattered (Bai et al. 2019) and have many useful applications, such as slow light generation (Okawachi et al. 2005), Brillouin amplification (Gao et al. 2012), and distributed pressure/temperature sensing (Teng et al. 2016), etc. The highest recorded spatial resolution in the range of Km belo
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