An electronic scanning spatial multiplexing technique for interferometric optical fiber sensor arrays

Dual-wavelength operation of digital spatial domain multiplexed fibre sensor arrays for dynamic strain monitoring

“…On the other hand, a fringe set generated by the interference between two sensing fibres, k and 1, has a digital spatial frequency, n' , expressed as = M(d' -d')a (5) Phase values at these frequency positions are normally not used. From Equation (5), itis possible to separate these phases from useful phase signals in the digital spatial domain by arranging positions of the fibre end-faces in such a way so that n'' <n (6) In addition, in order that all useful phase signals can be discriminated from each other in the digital spatial domain, additional constrain has to be applied to the positioning of the fibre end-faces, which can be expressed as n <nc' (p=1,2,...N-2)…”

“…The authors have developed a digital spatial domain multiplexing technique for the integration of large scale interferometric sensor arrays which is suitable for applications in smart structure and material [6]. It makes use of digital image processing technique to significantly reduce the number of optical fibre devices in the network and greatly simplify the system architecture.…”

“…into(6) and assuming ?i < ?2 , d1 <d2 < ... < dN,The positioning of fibre end-faces and the corresponding intensity spectrum are illustrated inFigure 2aand 2bpositioning arrangement of fibre end-faces (a) and its corresponding digital spatial frequency distribution (b)By differentiating both sides of Equation(3), the resolution of wavelength discrimination of the proposed system,x, can be written as x= L?Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/17/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx above, the directly retrieved phase changes in sensing fibre k are 4coded by wavelength X. However, because of the ambiguity problem, the real phase change, (1 is actually written Part of the digital spatial domain intensity spectrum of the fringe pattern generated in a system shown inFigure 1with three sensors and two wavelength carriers…”