Tapered GRIN fiber microsensor

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOThe sensitivity of an optical fiber microsensor based on inter-modal interference can be considerably improved by tapering a short extension of the multimode fiber. In the case of Graded Index fibers with a parabolic refractive index profile, a meridional ray exhibits a sinusoidal path. When these fibers are tapered, the period of the propagated beam decrease down-taper and increase up-taper. We take advantage of this modulation -along with the enhanced overlap between the evanescent field and the external medium- to substantially increase the sensitivity of these devices by tuning the sensor's maximum sensitivity wavelength. Moreover, the extension of this device is reduced by one order of magnitude, making it more propitious for reduced space applications. Numerical and experimental results demonstrate the success and feasibility of this approach.The sensitivity of an optical fiber microsensor based on inter-modal interference can be considerably improved by tapering a short extension of the multimode fiber. In the case of Graded Index fibers with a parabolic refractive index profile, a meridional ray exhibits a sinusoidal path. When these fibers are tapered, the period of the propagated beam decrease down-taper and increase up-taper. We take advantage of this modulation -along with the enhanced overlap between the evanescent field and the external medium- to substantially increase the sensitivity of these devices by tuning the sensor's maximum sensitivity wavelength. Moreover, the extension of this device is reduced by one order of magnitude, making it more propitious for reduced space applications. Numerical and experimental results demonstrate the success and feasibility of this approach.22253043230441FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2011/01524-8Tam, H.Y., Liu, S.Y., Guan, B.O., Chung, W.H., Chan, T.H., Cheng, L.K., Fiber bragg grating sensors for structural and railway applications (2005) Advanced Sensor Systems and Applications II, 5634, pp. 85-97Villatoro, J., Monzón-Hernández, D., Mejía, E., Fabrication and modeling of uniform-waist single-mode tapered optical fiber sensors (2003) Appl. Opt., 42, pp. 2278-2283Kumar, A., Varshney, R.K., Sa, C., Sharma, P., Transmission characteristics of SMS fiber optic sensor structures (2003) Optics Communications, 219, pp. 215-219Tripathi, S.M., Kumar, A., Varshney, R.K., Kumar, Y.P., Marin, E., Meunier, J.-P., Strain and temperature sensing characteristics of single-mode-multimode-single-mode structures (2009) J. Lightwave Technol., 27, pp. 2348-2356Biazoli, C.R., Silva, S., Franco, M.A.R., Frazão, O., Cordeiro, C.M.B., Multimode interference tapered fiber refractive index sensors (2012) Appl. Opt., 51, pp. 5941-5945Beltrán-Mejía, F., Osório, J.H., Biazoli, C.R., Cordeiro, C.M.B., D-microfibers (2013) J. Lightwave Technol., 31, pp. 2756-2761Wang, P., Brambilla, G., Ding, M., Semenova, Y., Wu, Q., Farrell, G., Investigation of single-mode-multimode-single-mode and single-mode-tapered-multimode-single-mode fiber structures and their application for refractive index sensing (2011) J. Opt. Soc. Am. B, 28, pp. 1180-1186Pillai, R.S., Lorenser, D., Sampson, D.D., Deep-tissue access with confocal fluorescence microendoscopy through hypodermic needles (2011) Opt. Express, 19, pp. 7213-7221Liu, Y., Wei, L., Low-cost high-sensitivity strain and temperature sensing using graded-index multimode fibers (2007) Appl. Opt., 46, pp. 2516-2519(2014) Comsol Multiphysics, , Burlington, MA, USA Version 4.4Ghatak, A., Thyagarajan, K., (1998) An Introduction to Fiber Optics, , Cambridge University Press, chap 9Shiraishi, K., Kuroo, S.-I., A new lensed-fiber configuration employing cascaded GI-fiber chips (2000) J. Lightwave Technol., 18, p. 787Guenther, R.D., (1990) Modern Optics, , Wiley, chap.9Kogelnik, H., On the propagation of gaussian beams of light through lenslike media including those with a loss or gain variation (1965) Appl. Opt, 4, pp. 1562-1569Birks, T., Li, Y., The shape of fiber tapers (1992) J. Lightwave Technol., 10, pp. 432-43

Identifying individuals using fNIRS-based cortical connectomes

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORThe fMRI-based functional connectome was shown to be sufficiently unique to allow individual identification (fingerprinting). We aimed to test whether a fNIRS-based connectome could also be used to identify individuals. Forty-four participants performed experimental protocols that consisted of two periods of resting-state interleaved by a cognitive task period. Connectome identification was performed for all possible pairwise combinations of the three periods. The influence of hemodynamic global variation was tested using global signal regression and principal component analysis. High identification accuracies well-above chance level (2.3%) were observed overall, being particularly high (93%) to the oxyhemoglobin signal between resting conditions. Our results suggest that fNIRS is a suitable technique to assess connectome fingerprints.10628892897FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORSem informaçãoSem informaçãoSem informaçã

Integrated polarizers based on tapered highly birefringent photonic crystal fibers

COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFINANCIADORA DE ESTUDOS E PROJETOS - FINEPThis paper proposes and demonstrates the creation of sections with a high polarization dependent loss (PDL) in a commercial highly birefringent (polarization maintaining) photonic crystal fiber (PCF), via tapering with pressure applied to the holes. The tapers had a 1-cm-long uniform section with a 66% scale reduction, in which the original microstructure aspect ratio was kept by the pressure application. The resulting waveguides show polarizing action across the entire tested wavelength range, 1510-1600 nm, with a peak PDL of 35.3 dB/cm (c.f. ∼1 dB/cm for a typical commercial polarizing fiber). The resulting structure, as well as its production, is extremely simple, and enable a small section with a high PDL to be obtained in a polarization maintaining PCF, meaning that the polarization axes in the polarizing and polarization maintaining sections are automatically aligned. © 2014 Optical Society of America.This paper proposes and demonstrates the creation of sections with a high polarization dependent loss (PDL) in a commercial highly birefringent (polarization maintaining) photonic crystal fiber (PCF), via tapering with pressure applied to the holes. The tapers had a 1-cm-long uniform section with a 66% scale reduction, in which the original microstructure aspect ratio was kept by the pressure application. The resulting waveguides show polarizing action across the entire tested wavelength range, 1510-1600 nm, with a peak PDL of 35.3 dB/cm (c.f. similar to 1 dB/cm for a typical commercial polarizing fiber). The resulting structure, as well as its production, is extremely simple, and enable a small section with a high PDL to be obtained in a polarization maintaining PCF, meaning that the polarization axes in the polarizing and polarization maintaining sections are automatically aligned.22151776917775COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFINANCIADORA DE ESTUDOS E PROJETOS - FINEPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFINANCIADORA DE ESTUDOS E PROJETOS - FINEPSem informaçãoSem informaçãoSem informação0.1.06.1177.00Chraplyvy, A.R., High-capacity lightwave transmission experiments (1999) Bell Labs Tech. J., 4 (1), pp. 230-245Bock, W.J., Chen, J., Eftimov, T., Urbanczyk, W., A photonic crystal fiber sensor for pressure measurements (2006) IEEE Trans. Instrum. Meas., 55 (4), pp. 1119-1123Bergh, R.A., Lefevre, H.C., Shaw, H.J., An overview of fiber-optic gyroscopes (1984) J. Lightwave Technol., 2 (2), pp. 91-107Jacobsen, W., Mayfield, J., Fournier, P., Bolte, D., Elmaola, H., Wang, C.H., Drenzek, G., Soufiane, A., (2013) Single-polarization Fiber, , Verrillon Inc., US Patent 8, 369, 672 B2Nolan, D.A., Berkey, G.E., Li, M.J., Chen, X., Wood, W.A., Zenteno, L.A., Single-polarization fiber with a high extinction ratio (2004) Opt. Lett., 29 (16), pp. 1855-1857Russell, P., Photonic crystal fibers (2006) J. Lightwave Technol., 24 (12), pp. 4729-4749Saitoh, K., Koshiba, M., Single-polarization single-mode photonic crystal fibers (2003) IEEE Photon. Technol. Lett., 15 (10), pp. 1384-1386Ju, J., Jin, W., Demokan, M.S., Design of single-polarization single-mode photonic crystal fiber at 1.30 and 1.55 μm (2006) J. Lightwave Technol., 24 (2), pp. 825-830Zhang, F., Zhang, M., Liu, X., Ye, P., Design of wideband single-polarization single-mode photonic crystal fiber (2007) J. Lightwave Technol., 25 (5), pp. 1184-1189Chen, M.Y., Sun, B., Zhang, Y.K., Broadband single-polarization operation in square-lattice photonic crystal fibers (2010) J. Lightwave Technol., 28 (10), pp. 1443-1446Serrão, V.A., Franco, M.A.R., A new approach to obtain single-polarization hollow-core photonic bandgap fiber (2013) Proc. SPIE 8794, Fifth European Workshop on Optical Fibre Sensors, 879428Kubota, H., Kawanishi, S., Koyanagi, S., Tanaka, M., Yamaguchi, S., Absolutely single polarization photonic crystal fiber (2004) IEEE Photon. Technol. Lett., 16 (1), pp. 182-184Statkiewicz-Barabach, G., Olszewski, J., Napiorkowski, M., Golojuch, G., Martynkien, T., Tarnowski, K., Urbanczyk, W., Thienpont, H., Polarizing photonic crystal fiber with lowindex inclusion in the core (2010) J. Opt., 12 (7), p. 075402Zheng, X., Liu, Y., Wang, Z., Han, T., Tai, B., Tunable single-polarization single mode photonic crystal fiber based on liquid infiltrating (2011) IEEE Photon. Technol. Lett., 23, pp. 709-711Espinel, A.V.Y., Franco, M.A.R., Cordeiro, C.M.B., Tunable single-polarization single-mode microstructure polymer optical fiber (2011) J. Lightwave Technol., 29 (16), pp. 2372-2378Qian, W., Zhao, C.L., Wang, Y., Chan, C.C., Liu, S., Jin, W., Partially liquid-filled hollow-core photonic crystal fiber polarizer (2011) Opt. Lett., 36 (16), pp. 3296-3298Sodré Jr., A.C., Nascimento Jr., A.R., Franco, M.A.R., Oliveira, I., Serrão, V.A., Fragnito, H.L., Numerical and experimental analysis of polarization properties from hybrid PCFs across different photonic bandgaps (2012) Opt. Fiber Technol., 18 (6), pp. 462-469Romagnoli, P., Biazoli, C.R., Franco, M.A.R., Cordeiro, C.M.B., De Matos, C.J.S., Generation of polarizing sections in highly birefringent photonic crystal fibers via post-processing (2013) CLEO:2013, , Optical Society of America, paper JTu4A.12Birks, T.A., Li, Y.W., The shape of fiber tapers (1992) J. Lightwave Technol., 10 (4), pp. 432-438Ju, J., Jin, W., Yang, Y., Introduction of birefringence into photonic crystal fibers (2011) Proc. SPIE 7753, 21st International Conference on Optical Fiber Sensors, 77536JMalitson, I.H., Interspecimen comparison of the refractive index of fused silica (1965) J. Opt. Soc. Am., 55 (10), pp. 1205-1209Gerosa, R.M., Spadoti, D.H., Menezes, L.S., De Matos, C.J.S., In-fiber modal Mach-Zehnder interferometer based on the locally post-processed core of a photonic crystal fiber (2011) Opt. Express, 19 (4), pp. 3124-3129The authors thank CAPES, Mackpesquisa, INCT Fotonicom (CNPq and FAPESP) and FINEP (SIA Project- proc. 0.1.06.1177.00) for financial support

Beyond the target area: an integrative view of tDCS-induced motor cortex modulation in patients and athletes

Transcranial Direct Current Stimulation (tDCS) is a non-invasive technique used to modulate neural tissue. Neuromodulation apparently improves cognitive functions in several neurologic diseases treatment and sports performance. In this study, we present a comprehensive, integrative review of tDCS for motor rehabilitation and motor learning in healthy individuals, athletes and multiple neurologic and neuropsychiatric conditions. We also report on neuromodulation mechanisms, main applications, current knowledge including areas such as language, embodied cognition, functional and social aspects, and future directions. We present the use and perspectives of new developments in tDCS technology, namely high-definition tDCS (HD-tDCS) which promises to overcome one of the main tDCS limitation (i.e., low focality) and its application for neurological disease, pain relief, and motor learning/rehabilitation. Finally, we provided information regarding the Transcutaneous Spinal Direct Current Stimulation (tsDCS) in clinical applications, Cerebellar tDCS (ctDCS) and its influence on motor learning, and TMS combined with electroencephalography (EEG) as a tool to evaluate tDCS effects on brain function

Manufacture of Tapered Fibers and FBG Writing

Abstract This article discusses procedures for production of tapered fibers in different diameters (tapers) and Bragg gratings writing (tFBG) in such fibers. The reflection spectra in different tFBGs are compared with a FBG written in standard single-mode fiber (SMF28). The gratings were characterized in terms of their thermal sensitivity. Values reasonably close to 11 pm/°C were expected and were obtained in the different gratings in tapers, confirming that the thermo-optical coefficient is predominant in relation to thermal expansion in gratings written in tapered fibers

Inferring the heritability of large-scale functional networks with a multivariate ACE modeling approach

Recent evidence suggests that the human functional connectome is stable at different timescales and is unique. These characteristics posit the functional connectome not only as an individual marker but also as a powerful discriminatory measure characterized by high intersubject variability. Among distinct sources of intersubject variability, the long-term sources include functional patterns that emerge from genetic factors. Here, we sought to investigate the contribution of additive genetic factors to the variability of functional networks by determining the heritability of the connectivity strength in a multivariate fashion. First, we reproduced and extended the connectome fingerprinting analysis to the identification of twin pairs. Then, we estimated the heritability of functional networks by a multivariate ACE modeling approach with bootstrapping. Twin pairs were identified above chance level using connectome fingerprinting, with monozygotic twin identification accuracy equal to 57.2% on average for whole-brain connectome. Additionally, we found that a visual (0.37), the medial frontal (0.31), and the motor (0.30) functional networks were the most influenced by additive genetic factors. Our findings suggest that genetic factors not only partially determine intersubject variability of the functional connectome, such that twins can be identified using connectome fingerprinting, but also differentially influence connectivity strength in large-scale functional networks

Characterisation of a Nafion film by optical fibre Fabry-Perot interferometry for humidity sensing

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESNafion has been evaluated as a sensing phase of an optical fibre humidity sensor based on a low-finesse Fabry-Perot interferometer. The sensor was constructed by manual deposition of a drop of a Nafion solution on the tip of a single mode optical fibre, forming a Fabry-Perot resonant cavity. The absorption of water by the Nafion film makes it swells, changing its refractive index and the length of the cavity, which produces a phase shift in the interference signal. The sensitivity, stability and response time of the sensor were evaluated in the RH range from 22 to 80% by analysing the correspondent reflection spectra of the interference fringes. As a result, it was obtained that Nafion can be used as sensing phase of an optical fibre humidity sensor based on optical fibre Fabry-Perot interferometry, presenting a response time of 242 ms (3% RH variation) and a sensitivity of 3.5 nm/%RH. (C) 2014 Elsevier B.V. All rights reserved.Nafion has been evaluated as a sensing phase of an optical fibre humidity sensor based on a low-finesse Fabry-Perot interferometer. The sensor was constructed by manual deposition of a drop of a Nafion solution on the tip of a single mode optical fibre, forming a Fabry-Perot resonant cavity. The absorption of water by the Nafion film makes it swells, changing its refractive index and the length of the cavity, which produces a phase shift in the interference signal. The sensitivity, stability and response time of the sensor were evaluated in the RH range from 22 to 80% by analysing the correspondent reflection spectra of the interference fringes. As a result, it was obtained that Nafion can be used as sensing phase of an optical fibre humidity sensor based on optical fibre Fabry-Perot interferometry, presenting a response time of 242 ms (3% RH variation) and a sensitivity of 3.5 nm/%RH.19699105CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESCNPq [573894/2008-6]FAPESP [2008/57808-1]FAPESP [11/00322-2]573894/2008-611/00322-22008/57808-1Sem informaçãoThe authors are thankful to INCTAA (CNPq grant 573894/2008-6 and FAPESP grant 2008/57808-1), Fotonicom, CePOF, and CAPES for financial support. J.S. Santos would like to acknowledge the scholarship from FAPESP (grant 11/00322-2)

Low frequency fluctuation of brain spontaneous activity and obsessive compulsive symptoms in a large school-age sample

Background: The present study was designed to explore alterations in brain dynamics at rest that are associated with Obsessive Compulsive Symptoms (OCS) in childhood by measuring low frequency fluctuation of spontaneous brain activity in a large school community sample from a developing country. Method: Resting state functional magnetic resonance imaging data were collected in a sample of 655 children and adolescents (6-15 years old) from the brazilian 'High Risk Cohort Study for Psychiatric Disorders (HRC)'. OCS were assessed using items from the Compulsion and Obsessions section of the Development and Well-Being Assessment (DAWBA). The correlation between the fractional amplitude of low frequency fluctuations (fALFF) and the number of OCS were explored by using a general linear model, considering fALFF as response variable, OCS score as regressor and age, gender and site as nuisance variables. Results: The number of OCS was positively correlated with the fALFF coefficients at the right sensorimotor cortex (pre-motor, primary motor cortex and post-central gyrus) and negatively correlated with the fALFF coefficients at the insula/superior temporal gyrus of both hemispheres. Our results were specific to OCS and not due to associations with overall psychopathology. Conclusions: Our results suggest that brain spontaneous activity at rest in the sensorimotor and insular/superior-temporal cortices may be involved in OCS in children. These findings need independent replication and future studies should determine whether brain spontaneous activity changes within these regions might be predictors of risk for obsessive-compulsive disorder latter in life.Sao Paulo Research Foundation - FAPESPCNPqFAPESPUniv Sao Paulo, Dept & Inst Psiquiatria, Fac Med FMUSP, Sao Paulo, SP, BrazilCNPq, Natl Inst Dev Psychiat Children & Adolescents, Sao Paulo, BrazilUniv Fed Sao Paulo UNIFESP, Interdisciplinary Lab Clin Neurosci LiNC, Sao Paulo, BrazilUniv Fed ABC, Ctr Math Comp & Cognit, Santo Andre, BrazilUniv Fed Rio Grande do Sul, Dept Psychiat, Porto Alegre, RS, BrazilHosp Clin Porto Alegre, Med Phys & Radioprotect Serv, Porto Alegre, RS, BrazilCarlos III Hlth Inst, Dept Psychiat, Bellvitge Univ Hosp, Bellvitge Biomed Res Inst IDIBELL, Barcelona, SpainCarlos III Hlth Inst, CIBERSAM, Barcelona, SpainUniv Autonoma Barcelona, Dept Psychobiol & Methodol Hlth Sci, Barcelona, SpainUniv Sao Paulo, Sch Med, Dept Radiol, Sao Paulo, BrazilFed Univ Sao Paulo UNIFESP, Dept Psychiat, Child & Adolescent Psychiat Unit UPIA, Sao Paulo, BrazilUniv Fed Sao Paulo UNIFESP, Interdisciplinary Lab Clin Neurosci LiNC, Sao Paulo, BrazilFed Univ Sao Paulo UNIFESP, Dept Psychiat, Child & Adolescent Psychiat Unit UPIA, Sao Paulo, BrazilFAPESP: 2012/50722-0FAPESP: 2013/00506-1FAPESP: 2008/57896-8FAPESP: 2016/05865-8FAPESP: 2013/08531-5FAPESP: 2016/02246-5FAPESP: 2013/10498-6CNPq: 442026/2014-5CNPq: 573974/2008-0Web of Scienc