Spectral modelling of curved long-period fibre gratings

González, Daniel A.; Arce-Diego, J. L.; Cobo, A.; López‐Higuera, José Miguel

doi:10.1088/0957-0233/12/7/306

Cited by 13 publications

(12 citation statements)

References 14 publications

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“…Dip 1 is the original transmission dip and dip 2 is the new dip. [18] In the literature the splitting has in several papers [69][70][71] been explained by stating that the fibre-curvature breaks the degeneracy of the cladding modes that are normally coupled to in the straight fibre. These non-degenerate modes, with power concentrated on opposite sides of the fibre core, then propagate with different speeds due to the difference in longitudinal strain above and below the fibre axis.…”

Section: Bend Sensorsmentioning

confidence: 99%

Drug-Induced T-Wave Morphology Changesn

Shakibfar¹

2014

Drug-Induced T-Wave Morphology Changes

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Section: Bend Sensorsmentioning

confidence: 99%

Drug-Induced T-Wave Morphology Changesn

Shakibfar¹

2014

Drug-Induced T-Wave Morphology Changes

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“…Several papers [61][62][63] have explained the splitting by stating that the fiber-curvature breaks the degeneracy of the cladding modes that are normally coupled to in the straight fiber. These nondegenerate modes, with power concentrated on opposite sides of the fiber core, then propagate with different speeds due to the difference in longitudinal strain above and below the fiber axis.…”

Section: Long-period Gratings As Bend Sensorsmentioning

confidence: 99%

Fiber-optical grating sensors for wind turbine blades: a review

Glavind¹,

Olesen²,

Skipper³

et al. 2013

Opt. Eng

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Abstract. With the rapid growth of wind turbines and focus on maintenance costs structural measurements are becoming essential. Fiberoptical sensors have physical properties that make them suitable for embedding in wind turbine blades, such as small size and immunity to electrical interferences. Fiber-optical grating sensors can be utilized to provide important information regarding strain, temperature, and curvature of the blades, which can be applied in condition-monitoring to detect fatigue failure and furthermore for optimization of the production from the wind turbine. We provide an overview of the current status and a discussion on research and implementation of fiber Bragg gratings and long-period gratings in wind turbine blade sensors. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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“…The constant resonance wavelength, as the sensor is bent (figure 4.15), could be due to two reasons. First, it has been shown that the change in the effective refractive index modulation of the gratings in the fiber core is less than 0.1 % for huge curvature [18] and since the bending curvature in this experiment was not large enough to induce a major change in the effective refractive index modulation, the resonance wavelength of the ELPG spectrum would not be affected. In addition, with the external medium refractive index higher than that of cladding, the phase matching Chapter 4…”

Section: Response Of Elpg To Bendingmentioning

confidence: 80%

“…Study shows that bending of the LPG results in a red shift of LPG resonance wavelength. Theoretical analysis showed that the spectral shift of the resonance wavelength is due to the change in the period of the gratings and the strain caused in the core of the optical fiber [18]. Despite non-linear output response, the sensor yields a total wavelength shift of 16 nm for a bending curvature of 4.4m" 1 .…”

Section: The Advantages Of Lpgs Over Fbgs Include the Elimination Of mentioning

confidence: 99%

“…In addition to the lack of confinement of the cladding mode, bending of the LPG will induce a lateral shift in the modal distribution of the fundamental core mode and the cladding mode. Even if air is the external medium, lateral shift of the modal distribution will exist when the LPG is bent [18]. The lateral shift of the modal distribution will cause the grating coupling strength to be reduced, which is due to the reduction of overlap integral between the core mode and the cladding mode as At Om" 1 the resonance dip is at its deepest.…”

Section: Response Of Elpg To Bendingmentioning

confidence: 99%

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Investigation of long-period gratings for sensor applications

Tan¹

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Long period fiber grating or LPG sensor has been gaining popularity due to its sensitivity to numerous perturbations such as temperature, strain and refractive index. The LPG has an advantage over other optical fiber sensors for refractive index sensing since the cladding region of the optical fiber, with LPG, is not required to be etched away in order to gain access to the evanescent field. Since the cladding modes propagates in the cladding within the LPG region of the optical fiber. The advantage is that the structural integrity of the optical fiber remains intact as compared to other optical fiber refractive index sensors with cladding etched away. Currently, a LPG sensor converts a measurand into wavelength. To interrogate the information would require expensive and complicated wavelength interrogation system. This will increase the overall system cost for industrial applications. In addition, other perturbations such as temperature and strain will affect the LPG wavelength, compromising the accuracy of the results. The aim of this research was the investigation of LPG for sensing applications such that the output from the LPG sensors is intensity-based instead of wavelength-based. Intensity-based LPG sensor requires its resonance dip or coupling strength to change with external perturbation of interest. Two intensity-based LPG sensors were developed and characterized. They were embedded LPG (ELPG) bending sensor and gelatin-coated LPG high relative humidity sensor. Embedding LPG in carbon-fiber composite material not only provides protection to the LPG, it was found experimentally that the ELPG responds to bending by changing its coupling strength with bending while its resonance wavelength remains unchanged. This was due to the matrix in the carbon-fiber composite which has a refractive index higher than that of the optical fiber cladding refractive index. That causes a change in the cladding mode viii

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Spectral modelling of curved long-period fibre gratings

Cited by 13 publications

References 14 publications

Drug-Induced T-Wave Morphology Changesn

Drug-Induced T-Wave Morphology Changesn

Fiber-optical grating sensors for wind turbine blades: a review

Investigation of long-period gratings for sensor applications

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