Fiber Optic Smart Structures

Udd, Eric

doi:10.1002/9781118014103.ch14

Cited by 135 publications

(32 citation statements)

References 31 publications

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“…Correlation coding has been introduced to Rayleigh scattering-based optical time-domain reflectometry, as early as 1989 [2]. In our work, we carry over the principle of match-filtering long pulse sequences to the realm of fiberoptic sensing [3][4][5][6][7], and use it for the unambiguous probing of a random locale. Stimulated Brillouin scattering (SBS) is an ideally suited platform for such random-access sensing system: not only is it inherently dependent on both strain and temperature [8][9][10][11][12], it also allows for the realization of correlation-based matched filtering of pulse sequences directly in the optical domain, as will be described in detail.…”

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confidence: 99%

Random‐access distributed fiber sensing

Zadok

Antman

Primerov

et al. 2012

Laser & Photonics Reviews

145

150

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Optical sensing offers an attractive solution to the societal concern for prevention of natural and human-generated threats and for efficient use of natural resources. The unprecedented properties of optical fibers make them ideal for implementing a 'nervous system' in structural health monitoring: they are small, low-cost and electrically and chemically inert. In particular, the nonlinear interaction of stimulated Brillouin scattering allows for the distributed measurement of strain and temperature with tens of km range. In this work, a novel, radar-inspired technique for random-access Brillouin scattering-based sensors is shown, making a significant step towards a real optical sensing nerve. The method selectively addresses each fiber segment as a distinct sensing element in a synaptic neuronal system. The measurement principle relies on phase-coding of both the Brillouin pump and signal waves by a high-rate, pseudo-random bit sequence. Temperature measurements with 1 cm resolution are reported. The measurement range is scalable to several km. The precision localization of disturbances has been a mainstay of radar systems since WW-II. A widely employed radar technique relies on the transmission of long sequences of short pulses [1], and their subsequent processing by a pre-designed matched filter at the receiving end. The filtering procedure compresses the sequence of pulses to a temporally-narrow impulse response function, which provides high resolution together with a large signal to noise ratio [1]. Matched filters in radars are realized by correlating the received radar echoes against a replica of the transmitted sequence, which was stored as a reference. The correlation, in turn, is implemented either through ratio-frequency, electrical analogue mixing or via digital signal processing. Correlation coding has been introduced to Rayleigh scattering-based optical time-domain reflectometry, as early as 1989 [2]. In our work, we carry over the principle of match-filtering long pulse sequences to the realm of fiberoptic sensing [3][4][5][6][7], and use it for the unambiguous probing of a random locale. Stimulated Brillouin scattering (SBS) is an ideally suited platform for such random-access sensing system: not only is it inherently dependent on both strain and temperature [8][9][10][11][12], it also allows for the realization of correlation-based matched filtering of pulse sequences directly in the optical domain, as will be described in detail. LETTER ARTICLE RandomIn stimulated Brillouin scattering (SBS), a relatively intense pump wave interacts with a counter-propagating signal wave, which is detuned in frequency [8]. The combination of the two waves generates an intensity beating pattern, whose frequency equals the difference Ω between the two optical frequencies. Through electrostriction, the intensity beat introduces an acoustic wave, which in turn leads to a traveling grating of refractive index variations, due to the photo-elastic effect. The traveling grating can couple optical power between ...

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confidence: 99%

Random‐access distributed fiber sensing

Zadok

Antman

Primerov

et al. 2012

Laser & Photonics Reviews

145

150

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“…For the on-line monitoring of large-scale engineering structures, developing distributed optical fiber sensors (DOFS) are of great interest [1][2][3][4]. The DOFS can be used to satisfy many specific engineering demands, where there are a large number of continuously distributed parameters in the engineering structures that must be measured.…”

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confidence: 99%

Experimental research on distributed fiber sensor for sliding damage monitoring

Guo

Wang

Liu

2009

Optics and Lasers in Engineering

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“…Although strain mode shapes are more sensitive to local damage than displacement mode shapes [35,36], the conventional foil strain gauges are not suitable for largescale civil SHM because they are unstable and unreliable for long-term monitoring and cannot reflect the influence of damage effectively unless located at the damaged region.More importantly, the advent of fiber optic sensing strategies, especially FBG sensors, has provided flexibility and practicality where the conventional sensors are either incapable or not feasible to make reliable measurements. Compared with mechanical sensors, they are light, compact, flexible, immune to electro-magnetic interference, and can be easily multiplexed in a large-scale distributed strain monitoring network [37]. The authors' laboratory has lately dedicated special effort toward developing a feasible distributed long-gage strain sensing system for practical adaptation to civil structural engineering [38,39].…”

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confidence: 99%

“…More importantly, the advent of fiber optic sensing strategies, especially FBG sensors, has provided flexibility and practicality where the conventional sensors are either incapable or not feasible to make reliable measurements. Compared with mechanical sensors, they are light, compact, flexible, immune to electro-magnetic interference, and can be easily multiplexed in a large-scale distributed strain monitoring network [37]. The authors' laboratory has lately dedicated special effort toward developing a feasible distributed long-gage strain sensing system for practical adaptation to civil structural engineering [38,39].…”

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Modal macro-strain flexibility methods for damage localization in flexural structures using long-gage FBG sensors

Adewuyi¹,

Wu²

2011

Struct. Control Health Monit.

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Modal flexibility is a robust and promising damage index for constructed facilities. However, the classicalflexibility methods are still unable to provide the required accuracy and reliability for damage localization due to their low sensitivity to small and multiple damages, and high sensitivity to measurement noise. In most cases, the modal parameters of the structures in the healthy state are required as baseline. On the other hand, the recent major advances in structural dynamics and mechanical vibration measurements have provided the opportunity to exploit more reliable modal parameters for damage identification. This paper presents modal macro-strain (MMS) flexibility methods to detect and locate multiple damages in elastic structures on the basis of dynamic distributed strain measurements from long-gage fiber Bragg grating sensors. Through analytical and experimental investigations, the MMS flexibility and its curvature have been validated as reliable indices to accurately localize less severe practical damages from few measurable modes with or without baseline information. The proposed damage indices are promising alternatives to the classical approach for civil structures where mode truncation and measurement errors are inevitable.[7], mode shape and its derivatives [8][9][10][11] modal flexibility and its curvature [12][13][14][15][16][17], modal stiffness [18][19][20], modal strain energy [21][22][23][24], frequency response functions (FRF) and their curvature [25][26][27][28] and power spectral density [29]. Many techniques have demonstrated varying degrees of success in small structures. However, in spite of the exhaustive research efforts devoted to structural health monitoring (SHM) methodologies, only a few have been fully validated for applicability on large-scale civil structures. They cannot provide the required accuracy and reliability needed for complex system identifications of real-life civil infrastructure due to the complicated behavior, the diversity of material properties, and incomplete, incoherent and noise-contaminated measurements of structural response to excitations.Among the commonly used nonparametric vibration-based damage identification techniques, modal flexibility methods are the focus of this paper. The advantage of modal flexibility-based identification methods lies in the fact that the flexibility matrix can be obtained from a truncated set of lower frequency modes with sufficient accuracy. Thus, the techniques have received considerable attention in the civil engineering field, where only a few fundamental modes are measurable. There are several studies focusing on the modal flexibility for damage localization in structures. Pandey and Biswas [12,13] proposed a method based on changes in flexibility and applied it to locate damage in a beam-type structure through numerical simulation and laboratory experiment. The method, however, is unable to reliably locate multiple damages. Besides, it requires a sufficiently fine spatial resolution of measurement. Toksoy and Aktan [1...

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Fiber Optic Smart Structures

Cited by 135 publications

References 31 publications

Random‐access distributed fiber sensing

Random‐access distributed fiber sensing

Experimental research on distributed fiber sensor for sliding damage monitoring

Modal macro-strain flexibility methods for damage localization in flexural structures using long-gage FBG sensors

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