Search results for "LONG"
showing 10 items of 3969 documents
Fabrication of chirped fiber Bragg gratings by simple combination of stretching movements
2008
Abstract A new stretching technique to fabricate chirped fiber Bragg gratings using a nonchirped phase mask is presented. It is based on continuous stretching and continuous UV beam scanning, which ensures phase matching between periods along the grating. Simple combinations of the fiber stretching movements of a pair of piezoelectric transducers are used to avoid unwanted period blurring and wavelength shifting. A third piezoelectric transducer can be easily added to the system to provide independent apodization through phase mask dithering. Successful fabrication of apodized and nonapodized chirped fiber gratings has been performed with this technique.
All-fiber noninterferometric narrow-transmission-bandpass filter
2012
In-fiber mode engineering based on the combination of Bragg and long-period gratings (LPGs) permits the implementation of noninterferometric transmission filters with narrow passbands using standard single-mode fiber. The design of the bandpass filter is based on the coupling between propagating and counterpropagating cladding modes in two fiber Bragg gratings. A LPG located between the Bragg gratings transfers power from the input fundamental mode to a specific cladding mode and recouples the filtered signal to the output fundamental mode. The filter produces a series of narrow passbands of about 30 pm linewidth with a maximum transmittance above 60%, 20 dB isolation, and passband separati…
Radiation Vulnerability of Fiber Bragg Gratings in Harsh Environments
2015
International audience; The difficulties encountered in the implementation of a temperature or strain sensor based on fiber Bragg grating (FBG) in a harsh radiative environment are introduced. We present the choices made to select both a radiation-resistant fiber in terms of transmission and also the grating inscription conditions necessary to write radiation tolerant FBGs in such fibers with a femtosecond laser. The radiation response of these gratings was also studied under radiation at dose up to 1 MGy. The comparison between Ge-free and Ge-doped fibers was highlighted.
Asymmetrically Apodized Fiber Bragg Gratings for Applications in Dispersion-Less Fabry-Pérot Fiber Cavities
2010
Abstract This article presents a theoretical study of the dispersion properties of the asymmetrically apodized fiber Bragg gratings. It is shown that the dispersive behavior of these gratings may be changed from normal to anomalous, depending on the apodization function and the grating strength. The asymmetrical Bessel functions were chosen in order to demonstrate these properties of the gratings. The application of this effect in a dispersion-less Fabry-Perot fiber cavity formed by two asymmetrically apodized fiber Bragg gratings is discussed.
Dynamic Bragg gratings induced in erbium-doped fiber at phase-Modulated beams' coupling
2005
We present the results of an experimental study of dynamic amplitude and phase Bragg gratings induced in a heavy-doped erbium fiber at the wavelengths 1532 and 1538 nm under the 980-nm pumping. The technique of two phase-modulated beams' coupling was applied for an experimental measurement of the changes in refractive index and gain accompanying the gratings' formation in the fiber, and an analysis based on the Kramers-Kronig Relations for the fiber absorption/gain spectra and two-pass amplifying was performed for modeling these changes.
Electrically tunable photonic true-time-delay line
2010
We present a new application of the acousto-optic superlattice modulation of a fiber Bragg grating based on the dynamic phase and group delay properties of this fiber-optic component. We demonstrate a tunable photonic true-time-delay line based on the group delay change of the light reflected from the grating sidebands. The delay is electrically tuned by adjusting the voltage applied to a piezoelectric transducer that generates the acoustic wave propagating along the grating. In our experiments, a true-time delay of 400 ps is continuously adjusted (300 ps within the 3 dB amplitude range of the first sideband), using a 12 cm long uniform grating.
Carbohydrate quality changes and concurrent changes in cardiovascular risk factors: a longitudinal analysis in the PREDIMED-Plus randomized trial.
2020
[Background]: Overall quality of dietary carbohydrate intake rather than total carbohydrate intake may determine the risk of cardiovascular disease (CVD).
Reliability and validity evidence of the early numeracy test for identifying children at risk for mathematical learning difficulties
2020
Abstract This study investigated reliability and validity evidence regarding the Early Numeracy test (EN-test) in a sample of 1139 Swedish-speaking children (587 girls) in kindergarten (n = 361), first grade (n = 321), and second grade (n = 457). Structural validity evidence was established through confirmatory factor analysis (CFA), which showed that a four-factor model fit the data significantly better than a one-factor or two-factor model. The known-group and cross-cultural validity were established through multigroup CFAs, finding that the four-factor model fit the gender, age and language groups equally well. Internal consistency for the test and sub-skills varied from good to excellen…
Gadd45α modulates aversive learning through post‐transcriptional regulation of memory‐related mRNA s
2018
Abstract Learning is essential for survival and is controlled by complex molecular mechanisms including regulation of newly synthesized mRNAs that are required to modify synaptic functions. Despite the well‐known role of RNA‐binding proteins (RBPs) in mRNA functionality, their detailed regulation during memory consolidation is poorly understood. This study focuses on the brain function of the RBP Gadd45α (growth arrest and DNA damage‐inducible protein 45 alpha, encoded by the Gadd45a gene). Here, we find that hippocampal memory and long‐term potentiation are strongly impaired in Gadd45a‐deficient mice, a phenotype accompanied by reduced levels of memory‐related mRNAs. The majority of the Ga…
Longitudinal Relationships Between Job Satisfaction and Creative Performance: A Three-Wave Cross-Lagged Panel Design
2020
Despite the assumption about the positive relationship between wellbeing and performance within the happy and productive worker thesis (HPWT), the matter is still under discussion due to inconclusive results. To better understand the link between wellbeing and performance and delineate their possible causal relationships, it is necessary to conduct longitudinal studies with data collection at different moments, as well as broaden the focus by considering different types of wellbeing and performance. To achieve this, the authors of this study analyzed the relationship between intrinsic (IJS) and extrinsic job satisfaction (EJS) with creative performance. The design consisted of a three-time …