Room-temperature operation of widely tunable loss filter

Shu, Xuewen; Allsop, Thomas D.P.; Gwandu, B.A.L.; Zhang, Lin; Bennion, I.

doi:10.1049/el:20010166

Cited by 34 publications

(22 citation statements)

References 5 publications

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“…Using a Taylor expansion for the temperature and bending induced changes in central wavelength of attenuation band, and making the assumption that there is no axial strain being applied to the sensor, we have the following expression, which contains the cross sensitivity (5) Using the expression given in [4] for and differentiating with respect to curvature yields the following expression for the spectral cross sensitivity of this LPG sensor: (6) Some of the terms in the above expression are already defined, the others are , the thermal expansion coefficient of the core and , the differential thermo-optic coefficient between the core ( C ) and the cladding material ( C ) from [5]. We assume that the amount of birefringence induced is negligibly small for curvatures of 2 m (no splitting of the attenuation bend was observed experimentally over the range of curvatures studied).…”

Section: Temperature Characteristicsmentioning

confidence: 99%

Bending and Orientational Characteristics of Long Period Gratings Written in D-Shaped Optical Fiber

Allsop

Gillooly

Mezentsev

et al. 2004

IEEE Trans. Instrum. Meas.

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Abstract-Long period gratings (LPGs) were written into a D-shaped single-mode fiber. These LPGs were subjected to a range of curvatures, and it was found that as curvature increased, there was increasingly strong coupling to certain higher order cladding modes without the usual splitting of the LPGs stopbands. A bend-induced stopband yielded a spectral sensitivity of 12.55 nm m for curvature and 2 2 10 2 nm C 1 for temperature. It was also found that the wavelength separation between adjacent bend-induced stopbands varied linearly as a function of curvature. Blue and red wavelength shifts of the stopbands were observed as the sensor was rotated around a fixed axis for a given curvature; thus, in principle, this sensor could be used to obtain bending and orientational information. The behavior of the stopbands was successfully modeled using a finite element approach.Index Terms-Curvature measurement, D-shaped optical fiber, long-period fiber gratings, optical fiber devices, temperature measurement.

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Section: Temperature Characteristicsmentioning

confidence: 99%

Bending and Orientational Characteristics of Long Period Gratings Written in D-Shaped Optical Fiber

Allsop

Gillooly

Mezentsev

et al. 2004

IEEE Trans. Instrum. Meas.

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“…Therefore only the cladding modes that extend out of the fiber are affected by changes to the surrounding medium RI. Using equation (1), the expression for the surrounding RI sensitivity can be derived [5].…”

Section: Lpfg Refractive Index Sensitivitymentioning

confidence: 99%

Liquid level sensor utilising a long period fiber grating

et al. 2009

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We propose here a liquid level sensor using a long period fiber grating (LPFG) in which direct liquid level measurement is carried out by utilising an LPFG, 100mm in length and a periodicity of 1mm. The LPFG was exposed to liquids with varying levels and the wavelength shift of a selected loss band of the transmission spectra was monitored using a broadband light source and an optical spectrum analyzer. The mechanism of this LPFG sensor is based on the fact that the effective Refractive Index (RI) of a cladding mode is directly dependant on the RI of the surrounding medium, be it air, or in this case water and petrol. As the surrounding RI changes, so does the phase matching condition of the LPFG. The result for the level change of the liquid with a specific RI is both a shift in wavelength and a change in the attenuation level of the selected loss band. For the selected loss band, continuous wavelength shifts of 9.5 nm and 25 nm for 100 mm of water and petrol level change have been observed respectively, with sub-millimetre accuracy.

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“…23. Using the results obtained from a 2-D curvilinear hybrid mode eigenvalue equation and the condition that the amount of birefringence induced in a typical single-mode fiber is negligibly small for curvatures ͑pure bending͒ of Ͻ2 m −1 , 24 ͑i.e., there is no splitting of the attenuation band͒, the spectral cross-sensitivity between temperature and curvature was calculated to be 3 ϫ 10 −3 nm m°C −1 .…”

Section: Characterization Of Curvature Sensorsmentioning

confidence: 99%

Application of long-period-grating sensors to respiratory plethysmography

et al. 2007

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Abstract.A series of in-line curvature sensors on a garment are used to monitor the thoracic and abdominal movements of a human during respiration. These results are used to obtain volumetric tidal changes of the human torso in agreement with a spirometer used simultaneously at the mouth. The curvature sensors are based on long-period gratings ͑LPGs͒ written in a progressive three-layered fiber to render the LPGs insensitive to the refractive index external to the fiber. A curvature sensor consists of the fiber long-period grating laid on a carbon fiber ribbon, which is then encapsulated in a low-temperature curing silicone rubber. The sensors have a spectral sensitivity to curvature, d / dR from ϳ7-nm m to ϳ9-nm m. The interrogation technique is borrowed from derivative spectroscopy and monitors the changes in the transmission spectral profile of the LPG's attenuation band due to curvature. The multiplexing of the sensors is achieved by spectrally matching a series of distributed feedback ͑DFB͒ lasers to the LPGs. The versatility of this sensing garment is confirmed by it being used on six other human subjects covering a wide range of body mass indices. Just six fully functional sensors are required to obtain a volumetric error of around 6%. © 2007 Society of Photo-Optical Instrumentation Engineers.

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Room-temperature operation of widely tunable loss filter

Cited by 34 publications

References 5 publications

Bending and Orientational Characteristics of Long Period Gratings Written in D-Shaped Optical Fiber

Bending and Orientational Characteristics of Long Period Gratings Written in D-Shaped Optical Fiber

Liquid level sensor utilising a long period fiber grating

Application of long-period-grating sensors to respiratory plethysmography

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