The Experts below are selected from a list of 51819 Experts worldwide ranked by ideXlab platform
Byoung Yoon Kim - One of the best experts on this subject based on the ideXlab platform.
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all fiber acousto optic tunable notch filter with electronically controllable Spectral Profile
Optics Letters, 1997Co-Authors: Hyo Sang Kim, Seok Hyun Yun, In Kag Kwang, Byoung Yoon KimAbstract:We demonstrate a novel all-fiber acousto-optic tunable notch filter based on coupling to cladding modes in a single-mode fiber. The device has the advantage of low loss (<0.1 dB) and low polarization dependence. By coupling input light to multiple cladding modes by use of multiple acoustic waves, we achieved an electronically controllable variable Spectral Profile without a significant coherent cross-talk problem.
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All-fiber acousto-optic tunable notch filter with electronically controllable Spectral Profile.
Optics Letters, 1997Co-Authors: Hyo Sang Kim, Seok Hyun Yun, In Kag Kwang, Byoung Yoon KimAbstract:We demonstrate a novel all-fiber acousto-optic tunable notch filter based on coupling to cladding modes in a single-mode fiber. The device has the advantage of low loss (
Kara Peters - One of the best experts on this subject based on the ideXlab platform.
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A Spectral Profile multiplexed FBG sensor network with application to strain measurement in a Kevlar woven fabric
Sensors and Smart Structures Technologies for Civil Mechanical and Aerospace Systems 2017, 2017Co-Authors: Guodong Guo, Drew Hackney, Mark Pankow, Kara PetersAbstract:A Spectral Profile division multiplexed fiber Bragg grating (FBG) sensor network is described in this paper. The unique Spectral Profile of each sensor in the network is identified as a distinct feature to be interrogated. Spectrum overlap is allowed under working conditions. Thus, a specific wavelength window does not need to be allocated to each sensor as in a wavelength division multiplexed (WDM) network. When the sensors are serially connected in the network, the spectrum output is expressed through a truncated series. To track the wavelength shift of each sensor, the identification problem is transformed to a nonlinear optimization problem, which is then solved by a modified dynamic multi-swarm particle swarm optimizer (DMS-PSO). To demonstrate the application of the developed network, a network consisting of four FBGs was integrated into a Kevlar woven fabric, which was under a quasi-static load imposed by an impactor head. Due to the substantial radial strain in the fabric, the spectrums of different FBGs were found to overlap during the loading process. With the developed interrogating method, the overlapped spectrum would be distinguished thus the wavelength shift of each sensor can be monitored.
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interrogation of a Spectral Profile division multiplexed fbg sensor network using a modified particle swarm optimization method
Measurement Science and Technology, 2017Co-Authors: Guodong Guo, Drew Hackney, Mark Pankow, Kara PetersAbstract:This paper applies the concept of Spectral Profile division multiplexing to track each Bragg wavelength shift in a serially multiplexed fiber Bragg grating (FBG) network. Each sensor in the network is uniquely characterized by its own reflected spectrum shape, thus Spectral overlapping is allowed in the wavelength domain. In contrast to the previous literature, Spectral distortion caused by multiple reflections and Spectral shadowing between FBG sensors, that occur in serial topology sensor networks, are considered in the identification algorithm. To detect the Bragg wavelength shift of each FBG, a nonlinear optimization function based on the output spectrum is constructed and a modified dynamic multi-swarm particle swarm optimizer is employed. The multiplexing approach is experimentally demonstrated on data from multiplexed sensor networks with up to four sensors. The wavelength prediction results show that the method can efficiently interrogate the multiplexed network in these overlapped situations. Specifically, the maximum error in a fully overlapped situation in the specific four sensor network demonstrated here was only 110 pm. A more general analysis of the prediction error and guidelines to optimize the sensor network are the subject of future work.
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Spectral Profile tracking of multiplexed fiber Bragg grating sensors
Optics Communications, 2015Co-Authors: William J. Stewart, Bram Van Hoe, Geert Van Steenberge, Stephen M. Schultz, Kara PetersAbstract:Abstract This paper outlines a demodulation technique for fiber Bragg grating (FBG) sensors based on combined Spectral Profile division multiplexing and wavelength division multiplexing. The advantage to this technique is that more FBG sensors can be compressed in a fixed bandwidth, as compared to pure wavelength division multiplexing, in which separate wavelength window is required for each sensor. To identify each FBG sensor, the cross-correlation algorithm of the original sensor Spectral Profile with the measured full-spectrum from the sensor array is calculated for rapid signal processing. The demodulation method is tested on simulated and experimental data. The demodulation generally performed well, except for cases where a significant amount of Spectral distortion due to multiplexing was present. Finally, a correction factor based on the prior location of each sensor at the previous time step is added to compensate for inherent uncertainties in the cross-correlation algorithm. The correction factor improved some predictions, but made others worse, and therefore needs further investigation for practical applications.
Hyo Sang Kim - One of the best experts on this subject based on the ideXlab platform.
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all fiber acousto optic tunable notch filter with electronically controllable Spectral Profile
Optics Letters, 1997Co-Authors: Hyo Sang Kim, Seok Hyun Yun, In Kag Kwang, Byoung Yoon KimAbstract:We demonstrate a novel all-fiber acousto-optic tunable notch filter based on coupling to cladding modes in a single-mode fiber. The device has the advantage of low loss (<0.1 dB) and low polarization dependence. By coupling input light to multiple cladding modes by use of multiple acoustic waves, we achieved an electronically controllable variable Spectral Profile without a significant coherent cross-talk problem.
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All-fiber acousto-optic tunable notch filter with electronically controllable Spectral Profile.
Optics Letters, 1997Co-Authors: Hyo Sang Kim, Seok Hyun Yun, In Kag Kwang, Byoung Yoon KimAbstract:We demonstrate a novel all-fiber acousto-optic tunable notch filter based on coupling to cladding modes in a single-mode fiber. The device has the advantage of low loss (
Sophie Kazamias - One of the best experts on this subject based on the ideXlab platform.
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Fourier-limited seeded soft x-ray laser pulse
Optics Letters, 2010Co-Authors: O Guilbaud, D Ros, K Cassou, F. Tissandier, Jean-philippe Goddet, Maxime Ribière, Stéphane Sebban, Julien Gautier, Denis Joyeux, Sophie KazamiasAbstract:We present what we believe to be the first measurement of the Spectral properties of a soft x-ray laser seeded by a high-order harmonic beam. Using an interferometric method, the Spectral Profile of a seeded Ni-like krypton soft x-ray laser (32.8 nm) generated by optical field ionization has been experimentally determined, and the shortest possible pulse duration has been deduced. The source exhibits a Voigt Spectral Profile with an FWHM of 3.1±0.3 mÅ, leading to a Fourier-transform pulse duration of 4.7 ps. This value is comparable with the upper limit of the soft x-ray pulse duration determined by experimentally investigating the gain dynamics, from which we conclude that the source has reached the Fourier limit. The measured bandwidth is in good agreement with the predictions of a radiative transfer code, including gain line narrowing and saturation rebroadening.
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temporal coherence and Spectral linewidth of a seeded soft x ray laser pulse
2009Co-Authors: O Guilbaud, Annie Klisnick, J P Godde, S Sebba, D Joyeu, D Ros, Jerome Gautie, K Cassou, Sophie Kazamias, J HabibAbstract:We present in this paper the first measurement of the Spectral Profile of a seeded soft x-ray laser. Using a varying path diference interferometer the temporal coherence of a seeded OFI x-ray laser has been experimentally determined, leading to a coherence length of 5ps of the order of the gain lifetime. The measured bandwidth is of order 3.4 mA which is in good agreement with the prediction of a theoretical model presented here.
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longitudinal coherence and Spectral Profile of a nickel like silver transient soft x ray laser
European Physical Journal D, 2006Co-Authors: O Guilbaud, Annie Klisnick, D Ros, K Cassou, Sophie Kazamias, D Joyeux, D Benredjem, D Phalippou, G Jamelot, C MollerAbstract:The Spectral width of a Ni-like silver transient soft X-ray laser (4d-4p λ= 13.9 nm) was experimentally inferred from the measurement of its temporal coherence, performed with a novel wavefront division interferometer. The measured coherence time of 3 ps corresponds to a Spectral linewidth of 0.7 mA which is narrow. We compare this experimental result to numerical simulations of the amplified line Profile, performed along two different approaches. Both calculations predict a Spectral linewidth that is about 3 times larger than the experimental value. We discuss several effects that might explain this discrepancy. We show that, due to the short duration of the X-ray laser pulse, the assumption of a stationary electromagnetic field used in both the experimental analysis and in the calculations need to be reconsidered.
Tim K Lee - One of the best experts on this subject based on the ideXlab platform.
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surface roughness measurement by speckle contrast under the illumination of light with arbitrary Spectral Profile
Optics and Lasers in Engineering, 2010Co-Authors: Lioudmila Tchvialeva, Haisha Zeng, Igo Markhvida, David I Mclea, Harvey Lui, Tim K LeeAbstract:Abstract Quantification of surface roughness greater than a micron is desirable for many industrial and biomedical applications. Polychromatic speckle contrast has been shown theoretically to be able to detect such roughness range using an appropriate light source with a Gaussian Spectral shape. In this paper, we extend the theory to arbitrary Spectral Profile by formulating speckle contrast as a function of Spectral Profile, surface roughness, and the geometry of speckle formation. Under a far-field set-up, the formulation can be simplified and a calibration curve for contrast and roughness can be calculated. We demonstrated the technique using a blue diode laser with a set of 20 metal surface roughness standards in the range 1–73 μm, and found that the method worked well with both Gaussian and non-Gaussian surfaces.
