&lt;title&gt;Bent long-period fiber gratings for sensor applications&lt;/title&gt;

Chen, Zhihao; Chiang, Kin Seng; Ng, Mei Nar; Chan, Yuen Ming; Ke, Hong

doi:10.1117/12.369362

Cited by 8 publications

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“…Besides the change in the optical path, changes in the difference between the effective refractive indices of core and cladding modes, as well as the break of degeneracy of the circular cladding modes, lead to the modification of the LPG spectrum [23,24]. Furthermore, experiments show that no significant polarization dependence exists, as expected [23,25]. This experimental behavior is confirmed by the simulation (considering F = 0.006 N due now to a different mechanical resonance), whose result fits the experimental curve well, particularly at the long wavelengths (peak to the right of the spectrum).…”

Section: Acousto-optic Modulation Effect In Lpg-resultsmentioning

confidence: 76%

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Yagodovskii¹

2002

Russ. Math. Surv.

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We have shown experimental results of the excitation of long period fiber gratings by means of flexural acoustic waves with a wavelength larger than the grating period, validated by numerical simulations. The effect of the acoustic wave on the grating is modeled with the method of assumed modes, which delivers the strain field inside the grating, then used as the input to the transfer matrix method, needed for calculating the grating spectrum. The experimental and numerical results are found to be in good agreement, even though only the strain-optic effects are taken into account.

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Section: Acousto-optic Modulation Effect In Lpg-resultsmentioning

confidence: 76%

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Yagodovskii¹

2002

Russ. Math. Surv.

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“…Besides the change in the grating period, changes in the effective refractive indices of core and cladding modes, as well as the break of degeneracy of the circular cladding modes, lead to the modification of the LPG spectrum [15]. Furthermore, experiments show that no significant polarization dependence exists, as expected [15,16]. Considering the different peak transmissivity observed when the acoustic wave is ON and OFF at the particular excitation frequencies, one sees that this effect can be employed as a switch for fiber lasers, a means of tuning a laser cavity or simply a filter.…”

Section: Resultsmentioning

confidence: 78%

Acousto-optic control of the LPG spectrum for sensing applications

Oliveira¹,

Possetti²,

Marques

et al. 2011

SPIE Proceedings

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Experimental and numerical demonstration of the acousto-optic effect applied in long period grating by means of flexural waves is presented. The interaction between acoustic and optical waves is modeled with help of the method of assumed modes, which delivers the strain field inside the grating and the transfer matrix method, which, given the strain field as input, calculate the resultant grating spectrum. The experimental and theoretical results are found to be in good agreement. The main effect of the bends in the grating is the break of degeneracy of the circular cladding modes, leading the attenuation band to be changed. Among all the applications of this methodology, it is important to mention the possibility of use as a tunable filter, laser cavity gain controller, switching device and transducer in sensing systems.When the refractive index of a fiber is modulated, with modulation period around hundreds of micrometers, a long period grating (LPG) is generated [1]. This period is chosen in order to make the grating able to couple light from the guided fundamental mode into the forward propagating cladding modes and irradiated modes. The high sensitivity of LPGs to the refractive index of the surrounding material shows great potential in sensors applications [2]. Moreover, such technology can be used in optical communications devices, for instance, as rejection filters [1].The most used inscription techniques of LPGs are based on induced changes in the refractive index of the fiber core through electric discharge [3], exposure to 193 nm UV light [4] and 10.6 μm (CO 2 ) laser radiation [5]. Another very popular technique uses the formation of bends in the fiber through transversal pressure of the fiber axis [6]. Such bends can also be generated by the propagation of "high" frequency flexural acoustical waves in the fiber, which gives rise to several useful devices [7]. The interaction of a flexural acoustic wave, generated by longitudinal excitation with an LPG "already" existent in the fiber, however, has not been reported so far in the literature. In this work, we show experimentally the dynamic control of the LPG transmission spectrum, whose results are compared to numerical simulations, carried-out using the methods of assumed modes and transfer matrix [8]. METHODOLOGYThe acousto-optic effect [7-9] has been successfully used in the construction of a variety of all-fiber devices. In this work, the interaction of the acoustic wave with the LPG is simulated with the help of a numerical technique based on the methods of assumed modes (AM) [10,11] and transfer matrix (TM) [12]. The numerical approach consists in calculating the time-space variation of the displacement field in a length of fiber through the method of AM, delivering the strain field in the LPG, which is further used as the input to the TM method. This allows the behavior of the transmitted spectrum of the grating to be calculated under the influence of the strain generated by the acoustic wave.The AM approach is a method used in mechanical engine...

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“…When a LPG is being bent, new dips in the spectrum can appear [66,67]. The new dip in the transmission band is normally significantly weaker and is typically in the range of 10 nm shifted from the original dip.…”

Section: Bend Sensorsmentioning

confidence: 99%

Drug-Induced T-Wave Morphology Changesn

Shakibfar¹

2014

Drug-Induced T-Wave Morphology Changes

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<title>Bent long-period fiber gratings for sensor applications</title>

Cited by 8 publications

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Representations of multivalued groups on graphs

Representations of multivalued groups on graphs

Acousto-optic control of the LPG spectrum for sensing applications

Drug-Induced T-Wave Morphology Changesn

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