Effect of selected luminescent layers on CCT, CRI, and response times

Phosphors have been used as wavelength converters in illumination for many years. When it is excited with blue light, the frequently used yttrium aluminium garnet doped with cerium (YAG:Ce) phosphor converts a part of blue light to a wideband yellow light, resulting in the generated light having a white color. By combining an appropriate concentration of the YAG:Ce phosphor and blue excitant light, white light of a desired correlated color temperature (CCT) can be obtained. However, this type of illumination has a lower color rendering index value (CRI). In an attempt to improve the CRI value, we mixed the YAG:Ce phosphor with europium-doped calcium sulfide phosphor (CaS:Eu), which resulted in a considerably increased CRI value. This article examines an experiment with luminescent layers consisting of a mixture of selected phosphors and polydimethylsiloxane (PDMS). Different thicknesses in these layers were achieved by changing the speed of rotation during their accumulation onto laboratory glass using the method of spin coating. The spectral characteristics of these luminescent layers as they were excited with blue light emitting diode (LED) and laser diode (LD) were then determined. A suitable combination of the YAG:Ce phosphor with a phosphor containing europium, as it was excited with a blue LED, yielded a source of white light with a CRI value of greater than 85. The response time in the tested luminescent layers to a rectangular excitant impulse (generated by a signal generator and transmitted by LD) was also measured in order to examine their potential use in visible light communications (VLC).Web of Science1213art. no. 209

Analysis of the applicability of singlemode optical fibers for measurement of deformation with distributed systems BOTDR

Distributed optical fiber sensors allow monitoring physical effects across the whole cable. The paper presents results obtained from the performed tests and shows that single mode fibers can provide analyses of the deformation changes, when distributed optical systems BOTDR used. We used standard optical fiber G.652.D with primary and secondary protected layers and specialized cable SMC-V4 designed for this purpose. The aim was to compare the deformation sensitivity and determine which fiber types are the best to use. We deformed the fiber in the longitudinal and transverse directions and mechanically stressed in orthogonal directions to find how to localize optical fibers. They could be deployed in real use. For achieving optimal results of mechanical changes and acting forces, sensor fibers have to be located carefully

Encapsulation of FBG sensor into the PDMS and its effect on spectral and temperature characteristics

Fiber Bragg Grating (FBG) is the most distributed type of fiber-optic sensors. FBGs are primarily sensitive to the effects of temperature and deformation. By employing different transformation techniques, it is possible to use FBG to monitor any physical quantity. To use them as parts of sensor applications, it is essential to encapsulate FBGs to achieve their maximum protection against external effects and damage. Another reason to encapsulate is increasing of sensitivity to the measured quantity. Polydimethylsiloxane (PDMS) encapsulation appears to be an interesting alternative due to convenient temperature and flexibility of the elastomer. This article describes an experimental proposal of FBG PDMS encapsulation process, also providing an analysis of the FBG spectral characteristics and temperature sensitivity, both influenced by high temperature and the process of polydimethylsiloxane curing itself. As for the PDMS type, Sylgard 184 was employed. Encapsulation consisted of several steps: allocation of FBG to PDMS in its liquid state, curing PDMS at the temperature of 80°C ± 5 %, and a 50-minute relaxation necessary to stabilize a Bragg wavelength. A broadband light source and an optical spectrum analyzer were both used to monitor the parameters during the processes of curing and relaxation. Presented results imply that such a method of encapsulation does not have any influence on the structure or functionality of the FBG. At the same time, a fourfold increase of temperature sensitivity was monitored when compared to a bare FBG

Non-destructive fiber-optic sensor system for the measurement of speed in road traffic

Fiber-optic sensors offer an attractive option to existing sensors for the measurement of the vehicle speed in road traffic. This article describes the measuring scheme of two interferometric sensor units including input-output components for the measurement of the vehicle speed. The interferometric sensors operate on a principle of Mach-Zehnder interferometer. The sensors are constructed to detect a vibration caused by vehicles moving on roads. The sensor system processes the vibrational response, and the vehicle speed is calculated in a time domain. DFB laser was used with a wavelength of 1550 nm and output power of 1--5~mW. The solution provides very high sensitivity. The performance of the proposed system was verified by a series of experimental measurements of the speed. The vehicle speed was monitored by GPS. The highest relative difference of the evaluated speed against GPS data was 7.7 %, the smallest was 1.36 %. When recalculated on kph, the absolute error ranged in the tolerance ± 3 kph, which denotes segmental measuring systems in CZE

Non-invasive fiber optic probe encapsulated into PolyDiMethylSiloxane for measuring respiratory and heart rate of the human body

This article describes the design and the functional verification of fiber optic system with an innovative non-invasive measuring probe for monitoring respiratory and heart rate. The measuring probe is based on Fiber Bragg Grating (FBG), and it is encapsulated in the PolyDiMethylSiloxane polymer (PDMS). PDMS offers a unique combination of suitable properties for the use in biomedical applications. The main advantages include inert to human skin and immunity to electromagnetic interference. The measuring probe is a part of contact strip which is placed on the chest of the patient. The measurement is based on sensing the movements of the thoracic cavity of the patient during breathing. Movement (mechanical stress) is transferred to FBG using the contact strip. Respiratory and heart rate are analyzed using the spectral evaluation of the measured signals. This monitoring method is fully dielectric; thus the absolute safety of the patient is ensured. The main contributions of the article are a design of non-invasive probe encapsulated into a PDMS polymer and implementation of the probe for humans using a contact strip. This combination forms an essential element of the measuring system. The set of experimental measurements verified functionality with respect to the position of the patient. Performed experiments proved the functionality of the presented solution so it can be utilized for further research in biomedical applications

Restoration of optical spectrum

This article deals with research of luminous sources which could be applied in indoor Free Space Optic (FSO) networks. Indoor FSO networks have potential to replace standard IEEE 802.11 in the future. Suitable selection and configuration of optical radiation sources can at the same time provide communication and lighting in indoor spaces. This article is engaged in spectral mergence of optical sources, willful suppression of part of emitted visible spectrum and consequential restoration of this optical spectrum

Zastosowania LEDów w komunikacji samochodowej

The passengers safety, the decrease of mortality on European roads, the increase of individual transport and reducing of CO2 emission are important concepts, which coming to the fore in automotive industry at the present time. The only solution of the aspects mentioned above is establishment of informative-communicative (cooperative) systems. The International Organizations (Car2Car Communications Consortium, GeoNET) had built the core of problems solution of informative-communicative systems construction on wireless communication in range of radio frequency (802.11p WAVE, CALM M5). Thanks to the significant advance in the quality of vehicles lighting, in the form of implementation of LED technologies, and development of adaptive lighting systems, shows the car communication systems based on optical free space networks that are next developmental milestone in the construction of informative-communicative (cooperative) systems V2V2I (Vehicle-to-Vehicle-to- Infrastructure).Bezpieczeństwo pasażerów, spadek liczby wypadków śmiertelnych na drogach Europy, wzrost liczby pojazdów i ograniczenie emisji CO2 to ważne wyzwania stojące dzisiaj przed przemysłem samochodowym. Jedynym rozwiązaniem wszystkich tych problemów jest wykorzystanie systemów informacyjno-komunikacyjnych. Organizacje międzynarodowe (Konsorcjum Car2Car, GeoNet) tworzą narzędzia informacyjnokomunikacyjne bazujące na komunikacji bezprzewodowej dla częstotliwości (802,1p WAVE, CALM M5). Dzięki istotnemu rozwojowi jakości oświetlenia samochodowego, m.in. wdrożenia systemów LED i adaptacyjnych, możliwe staje się wprowadzanie systemów komunikacji pojazdów opartych na otwartych sieciach optycznych, co w dalszej kolejności umożliwi wprowadzenie informacyjno-komunikacyjnych systemów V2V2I

Fiber-optic interferometric sensor for monitoring automobile and rail traffic

This article describes a fiber-optic interferometric sensor and measuring scheme including input-output components for traffic density monitoring. The proposed measuring system is based on the interference in optical fibers. The sensor, based on the Mach-Zehnder interferometer, is constructed to detect vibration and acoustic responses caused by vehicles moving around the sensor. The presented solution is based on the use of single-mode optical fibers (G.652.D and G.653) with wavelength of 1550 nm and laser source with output power of 1 mW. The benefit of this solution lies in electromagnetic interference immunity and simple implementation because the sensor does not need to be installed destructively into the roadway and railroad tracks. The measuring system was tested in real traffic and is characterized by detection success of 99.27% in the case of automotive traffic and 100% in the case of rail traffic.Web of Science2662995298

Simple and universal current modulator circuit for indoor mobile free-space-optical communications testing

The use of LED for illumination and communication together is more and more interesting with the increasing deployment of LEDs to our homes and industrial buildings. Modulation of this kind of light sources is difficult because of high voltage and current demands. Since the LED configurations and values of current and voltage are different, our universal modulator has to be able to operate even under these circumstances. This paper proposes simple and universal current modulator for LED lighting modulation for frequencies around 1MHz. Main objective is to allow initial testing of different types of High Power LEDs and different photodetector configurations and circuits in diffusive based Free-Space-Optical networks. In the experimental part we also compare results for some different types of LED light sources