&lt;title&gt;Long-period fiber grating bending sensors in laminated composite structures&lt;/title&gt;

The behavior of a temperature self-compensating, fiber, long-period grating ͑LPG͒ device is studied. This device consists of a single 325-m-period LPG recorded across two sections of a single-mode B-Ge-codoped fiber-one section bare and the other coated with a 1-m thickness of Ag. This structure generates two attenuation bands associated with the eighth and ninth cladding modes, which are spectrally close together ͑ϳ60 nm͒. The attenuation band associated with the Ag-coated section is unaffected by changes in the refractive index of the surrounding medium and can be used to compensate for the temperature of the bare-fiber section. The sensor has a resolution of Ϯ1.0 ϫ 10 Ϫ3 for the refractive index and Ϯ0.3°C for the temperature. The effect of bending on the spectral characteristics of the two attenuation bands was found to be nonlinear, with the Ag-coated LPG having the greater sensitivity.

show abstract

“…For this arrangement with the LPG midway between the clamps, the sensor's curvature, R, is given in Ref. 19 as…”

Section: Bending Sensitivitymentioning

confidence: 99%

Sensing characteristics of a novel two-section long-period grating

et al. 2003

View full text Add to dashboard Cite

show abstract

“…The study of LPGs has yielded many potential uses in the area of telecommunications and numerous sensing applications. This is because the mean wavelengths of the attenuation bands are influenced by strain, temperature, curvature and the refractive index of the surrounding medium [1][2][3][4][5][6][7][8][9]. In particular there has been strong interest in using long period gratings as chemical sensors [6,7,9], for example in the detection of organic aromatic compounds in paraffin [7].…”

Section: Introductionmentioning

confidence: 99%

Enhanced spectral sensitivity of fibre long-period gratings to refractive index of aqueous solutions utilising copper patterned coatings

et al. 2006

View full text Add to dashboard Cite

A set of long period grating devices have been fabricated in photosensitive single mode fibre coated with a series of copper rings (period of 380Pm, 50% duty cycle and length of 4cm). The long period gratings were inscribed with a uniform UV-laser exposure across the entire length of the copper ring patterned coating. The devices ranged in copper thickness from 0.5Pm to 1.5Pm. In addition, a control long period grating was fabricated in the same type of fibre with the same period for comparison. The refractive index and temperature spectral sensitivity of these devices were investigated and it was found that the index and temperature sensitivity is a function of the thickness of the copper rings, as supported by theoretical modelling. Furthermore, the index sensitivity of these devices in the 1.333 index region is greater than the control long period grating. The patterned 0.5Pm coated long period grating gave a sensitivity of 'O/'n = -74 nm leading to a resolution of 1.4u10-3 compared to the control which had a sensitivity of 'O/'n = -32 nm with a resolution of 3.2u10 -3 in the index region of 1.320 to 1.380 (aqueous solution regime). This demonstrates a two fold increase in the sensitivity. This novel fibre long period grating device shows potential for increasing the resolution of measurements of the index of aqueous solutions.

show abstract

“…Examples include the use of air-clad [8] or depressed-cladding [9] fibres to desensitise the structure to changes in the refractive index of the surrounding medium, and the use of three-layered W-fibres either to reduce sensitivity to temperature changes [10] or, alternatively, to maximise the temperature sensitivity [11]. A promising application of LPGs is in bend or shape sensing where several papers have been published [5,6,12]. A few papers have been presented concerning LPGs written in asymmetric optical fibres [7,12], which have shown red/blue wavelength shifts depending on the way the fibre is bent.…”

Section: Introductionmentioning

confidence: 99%

“…Coupling of light from the core to various cladding modes results in a set of attenuation bands in the transmitted light. The study of the LPG attenuation bands has yielded many potential applications in the field of sensing through their sensitivities to strain, temperature, refractive index and bending/shape [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The LPG sensitivity can manifest itself in two ways; firstly through the spectral shift in the attenuation band, which here we refer to as spectral sensitivity, and secondly through a change in the strength of the attenuation band.…”

Section: Introductionmentioning

confidence: 99%

The spectral sensitivity of long-period gratings fabricated in elliptical core D-shaped optical fiber

et al. 2004

View full text Add to dashboard Cite

Long period gratings (LPGs) were written into a D-shaped optical fibre, which has an elliptical core with a W-shaped refractive index profile. The LPG's attenuation bands were found to be sensitive to the polarisation of the interrogating light with a spectral separation of about 15nm between the two orthogonal polarisation states. In addition, two spectrally overlapping attenuation bands corresponding to orthogonal polarisation states were observed; modelling successfully reproduced this spectral feature. The spectral sensitivity of both orthogonal states was experimentally measured with respect to temperature, surrounding refractive index, and directional bending. These LPG devices produced blue and red wavelength shifts of the stop-bands due to bending in different directions. The measured spectral sensitivities to curvatures, d /dR, ranged from -3.56nm m to +6.51nm m. The results obtained with these LPGs suggest that this type of fibre may be useful as a shape/bend sensor. It was also demonstrated that the neighbouring bands could be used to discriminate between temperature and bending and that overlapping orthogonal polarisation attenuation bands can be used to minimise error associated with polarisation.

show abstract

<title>Long-period fiber grating bending sensors in laminated composite structures</title>

Cited by 36 publications

References 0 publications

Sensing characteristics of a novel two-section long-period grating

Sensing characteristics of a novel two-section long-period grating

Enhanced spectral sensitivity of fibre long-period gratings to refractive index of aqueous solutions utilising copper patterned coatings

The spectral sensitivity of long-period gratings fabricated in elliptical core D-shaped optical fiber

Contact Info

Product

Resources

About