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Monitoring the evaporation of fluids from fiber-optic micro-cell cavities
Eyal Preter, Borut Preložnik, Vlada Artel, Chaim Sukenik, Denis Đonlagić, Avi Zadok, 2013, izvirni znanstveni članek

Opis: Fiber-optic sensors provide remote access, are readily embedded within structures, and can operate in harsh environments. Nevertheless, fiber-optic sensing of liquids has been largely restricted to measurements of refractive index and absorption spectroscopy. The temporal dynamics of fluid evaporation have potential applications in monitoring the quality of water, identificationof fuel dilutions, mobile point-of-care diagnostics, climatography and more. In this work, the fiber-optic monitoring of fluids evaporation is proposed and demonstrated. Sub-nano-liter volumes of a liquid are applied to inline fiber-optic micro-cavities. As the liquid evaporates, light is refracted out of the cavity at the receding index boundary between the fluid and the ambient surroundings. A sharp transient attenuation in the transmission of light through the cavity, by as much as 50 dB and on a sub-second time scale, is observed. Numerical models for the transmission dynamics in terms of ray-tracing and wavefront propagation are provided. Experiments show that the temporal transmission profile can distinguish between different liquids.
Ključne besede: fiber-optic sensors, opto-fluidics, evaporation monitoring, optical micro-cells, fiber cavities, droplet analysis
Objavljeno: 22.06.2017; Ogledov: 520; Prenosov: 264
.pdf Celotno besedilo (551,58 KB)
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Fiber-optic sensors for measurements of torsion, twist and rotation
Vedran Budinski, Denis Đonlagić, 2017, pregledni znanstveni članek

Opis: Optical measurement of mechanical parameters is gaining significant commercial interest in different industry sectors. Torsion, twist and rotation are among the very frequently measured mechanical parameters. Recently, twist/torsion/rotation sensors have become a topic of intense fiber-optic sensor research. Various sensing concepts have been reported. Many of those have different properties and performances, and many of them still need to be proven in out-of-the laboratory use. This paper provides an overview of basic approaches and a review of current state-of-the-art in fiber optic sensors for measurements of torsion, twist and/or rotation.
Ključne besede: fiber optic sensors, twist sensors, rotation sensors, circular birefringence, linear birefringence, FBG, polarization, optical fibers, Fiber Bragg Gratings
Objavljeno: 22.06.2017; Ogledov: 729; Prenosov: 177
.pdf Celotno besedilo (8,96 MB)
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Unobtrusive heartbeat monitoring by using a bed fiber-optic sensor
Peter Podbreznik, Denis Đonlagić, Dejan Lešnik, Boris Cigale, Damjan Zazula, 2014, izvirni znanstveni članek

Opis: Demographic trends suggest that by 2050 approximately 11 % of the world population will be 80 or older. If a fast increase of chronic diseases is also considered, it becomes clear the present healthcare capacities won't be enough. The elderly and people with limited abilities must be assisted in their home environment and, thus, reduce needs for hospitalization and institutionalization. Today's computer and communication technologies provide different smart devices, which is a core of emerging intensification of homecare services, in particular remote and unobtrusive monitoring of human functional- health parameters.
Ključne besede: plastic optical fiber, speckle interferometry, unobtrusive monitoring of human vital signs, heartbeat detection, ballistocardiography
Objavljeno: 21.12.2015; Ogledov: 854; Prenosov: 87
.pdf Celotno besedilo (573,53 KB)
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Unobtrusive monitoring of human vital functions based on speckle interferometry with plastic optical fiber
Peter Podbreznik, Denis Đonlagić, Dejan Lešnik, Boris Cigale, Damjan Zazula, 2013, izvirni znanstveni članek

Opis: In this paper, a speckle interferometer with a plastic optical fiber system is reported for unobtrusive monitoring of heartbeat and respiration. The sensor consists of a laser diode butt-coupled to the plastic optical fiber, whose exit face projects speckle patterns onto a linear optical sensor array, which leads to a simple and cost-effective construction. Speckle images are acquired in a sequence and transformed into a 1D signal by using a phase-shifting method. Band-pass filtering and Morlet-wavelet-based multiresolutional approaches were used to analyze signals for the detection of cardiac and respiratory activities, respectively. Ten young, healthy persons participated in system testing, by lying supine on a mattress with embedded plastic optical fiber. Experimental results show the proposed system and detection algorithms are highly efficient. Sensitivities of 99.4 0.6% and 95.3 3%, precisions of 98.8 1.5% and 97.9 2.3%, and mean delays between interferometric detections and corresponding referential signals of 116.6 55.5ms and 1299.2 437.3 ms were computed for heartbeat and respiration, respectively.
Ključne besede: plastic optical fiber, speckle interferometry, unobtrusive monitoring, heartbeat detection, respiration detection, phase-shift method, wavelet transform
Objavljeno: 10.07.2015; Ogledov: 905; Prenosov: 12
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System for precise balancing and controlled unbalancing of fiber-optic interferometers
Irvin Sirotić, Denis Đonlagić, 2002, izvirni znanstveni članek

Opis: A system for accurate balancing and controlled unbalancing of the optical path difference in all-fiber optical interferometers is described. Interferometers with various arm lengths (1-30m) and with initial optical pathdifferences of as much as 1 cm have been successfully balanced within a 5 ▫$mu$▫m range. In addition, the proposed system allows for controlled unbalancing of arbitrary all-fiber optical interferometers with a precision better than 5 ▫$mu$▫m.
Ključne besede: electrical measurements, optical instruments, interferometers, fiber interferometers, optical path difference, sensor systems
Objavljeno: 01.06.2012; Ogledov: 968; Prenosov: 79
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A low bending loss multimode fiber transmission system
Denis Đonlagić, 2009, izvirni znanstveni članek

Opis: This paper presents a high bend tolerant multimode optical fiber transmission system that is compatible with standard 50 ìm graded index multimode fiber, interms of achievable bandwidth and interconnectivity losses. When the 10 loops of the proposed bend resistive multimode fiber were wrapped around a cylinder of 1.5 mm radius, bend losses below -0.2 dB were achieved in case of experimentally produced fiber. Furthermore, when the section of the proposed bend resistive fiber was inserted between two sections of a standard 50 ìm graded index multimode fiber, the total experimental measured loss proved to be below -0.15 dB.
Ključne besede: optical fiber transmission systems, bending loss, bend resistive multimode fiber, optical communications, fiber optics
Objavljeno: 31.05.2012; Ogledov: 1661; Prenosov: 93
URL Povezava na celotno besedilo

In-line higher order mode filters based on long highly uniform fiber tapers
Denis Đonlagić, 2006, izvirni znanstveni članek

Opis: This paper presents a simple and effective design of taper-based higher order mode (HOM) filters that can effectively remove HOMs from the few-mode fibers. For this purpose, a taper manufacturing technique that allows the production of long and highly uniform tapers was developed. A filter performance was demonstrated on a standard single-mode telecommunication fiber operating at 850 nm. The HOM suppression was better than$-$39 dB, and the insertion loss ofthe fundamental mode was less than 0.15 dB.
Ključne besede: optical fibres, few moded fiber, fiber design, mode conversion, mode filter, noise figure, optical fiber dispersion, optical signal to noise, optical transmission systems, taper
Objavljeno: 31.05.2012; Ogledov: 1631; Prenosov: 92
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