Faculty of Electrical Engineering

Czech Technical University in Prague

CTU in Prague

Free-space and fiber optics

Department of Electromagnetic Field
Technická 2
166 27 Praha 6
Tel.: 224 352 280, Fax: 233 339 958
http://elmag.org/
 

Who are we?

Stanislav Zvánovec
Coordinates activities in the fields of fiber and free-space optics with extension towards the sub-millimeter region and terahertz spectroscopy.

Karel Novotný
His scientific focus is aimed at electromagnetic field theory, wave propagation in optical waveguides and numerical field modeling.

Matěj Komanec
Deals with nonlinear optical phenomena and their utilization in all-optical networks, with pulse lasers and analyses of optical effects in simulation software.

Jiří Libich
His work is mainly focused on free-space and beam optics, analysis of atmospheric influence on optical links and optical subsystem programming.

Jan Šístek
Engages in fiber optics and microwave techniques.

Michael Písařík
Deals with new technological approaches and waveguide optics and with passive nonlinear optical components.

Jan Bohata
Focuses on optical fiber component development and on testing of modern fiber systems in hazardous environment.

Pavel Škoda
Deals with photonic services, fiber optics, optical waveform shaping and fiber lasers.

Petr Chvojka
Focuses on analyses and development of Vissible Light Communications (VLC)

Tomáš Němeček
Focuses on advanced fiber sensors for gas and liquid detection.

Petr Dvořák
Focuses on measurement methods in optical systems and microwave radiometry.

Martin Mudroch
His work composes of system behavior simulation with employment of neural networks and FPGA programming.

Redwan Ahmad
Focused on Microstructured optical fibers (MOF), hllow core fibers.

Petr Pešek
Deals with LTE transfer through optical infrastructures (both fiber and FSO).

Norhanis Aida Mohd Nor
Diversity techniques for free-spce optical networks (PhD student of Northumbria University, supervisor prof. Ghasemlooy, co-supervisor prof. Zvanovec).

External (or hosting) team members:

  • Joaquin Perez (Valenci University, Northumbria University), 2013
  • Paul Anthony Haigh (University of Bristol), 2014
  • Mojtaba Mansour Abadi (Northumbria University, Newcastle upon Tyne), 2014
  • Hatef Nouri (Ozyegin University, Istanbul), 2014
  • Amalia Nallely Castro Martínez (Universidad Nacional Autónoma de México), 2015

What are our research topics?

Our team research is focused on numerous areas of optical signal propagation and transmission.

First topic is represented by fiber optics, where we work on research and development of fiber sensors, fiber lasers, broadband optical signal generation and all-optical network components. We utilize state-of-art techniques and technologies. We test specialty optical fibers (microstructured, doped, special glass materials) for the purposes of liquid detection, nonlinear effects and supercontinuum generation. Furthermore we develop fiber pulsed fiber lasers, evaluate long-term effects on optical fibers, design fiber structures and much more. For these we utilize state-of-art simulation software and approaches. We work in co-operation with leading universities worldwide, Institute of Photonics and Electronics, Academy of Sciences and with a number of technological companies participating in the field of photonics.

Another research and development topic is represented by free-space optics (FSO), where we exploit several wireless optical links in the CTU campus connected into a simple network. We measure atmospheric parameters; we have a special turbulence chamber; we develop behavioral models of atmospheric turbulences, rain influence, etc. with respect to the quality of FSO links.

Last topic of interest is wireless optical communication inside buildings in visible light (indoor visible light communication, VLC), where transmissions over 7 Gbit/s have been achieved. Here our goal is analysis of LED technologies coverage as for room illumination and data transmission. Furthermore we test in international cooperation the employment of organic LED (OLED) for communication purposes.

What it is good for?

The optical fiber development in the last decades have enabled extreme growth in network transmission capacity, but also employment of optical fibers in other areas, such as eg. sensing. Optical fibers are isolants, they are chemically resistant and immune to electromagnetic interference . which makes the ideal candidates for sensing in hazardous environments. Special fiber structures then enable broadband signal generation, where application in medicine or chemical analysis is of overestimate value. Free-space optic link then enable high-speed transmission to numerous areas, where it is not possible to place optical fibers (historical town centers), or where standard high-speed transmissions are insufficient in capacity. Furthermore for VLC the LED illumination is massively applied worldwide not only indoor but also in public places. In contrast to radiofrequency region VLC provides several orders higher transmission speeds.

What have we been working on?

Fiber optic detection of liquids

The project is focused on development of fiber optical sensors with enhanced sensitivity for detection of liquid analytes. This detection is based on enhanced overlapping of evanescent wave with the liquid, in principle we speak of refractometric measurement. In the project we develop various types of fiber optic detection units for detection of liquid (such as hydrocarbons) not only based on silica fibers, but also based on microstructure optical fibers. This project is carried out in cooperation with SQS, Fiber optics.

Broadband optical source based on soft-glass fibers

Aim of the project is the development of a broadband optical source prototype (i.e. supercontinuum source). The supercontinuum source is composed of a pulsed laser and a nonlinear media . optical fiber. The nonlinear media is based in our application on conventional and microstructured optical soft-glass fibers (fluoride, lead-silicate, chalcogenide). In parallel we are developing a pulsed fiber laser at 1550 nm and 2000 nm. This project is carried out in cooperation with SQS, Fiber optics, development of the 2000 nm pulsed laser also in cooperation with Institute of photonics and electronics, AS CR.

Optical packet switch

Project aims at a switch development, which is based on optical packet routing. Main advantage stands in keeping the data payload in optical format, while only the label . IP address . is processed electronically. Employing this approach we achieve higher data speeds than with the consideration of opto-electronic speed limits. For the switching itself we utilize special fibers and nonlinear phenomena.

Femtosecond fiber laser

We develop fiber laser with passive mode synchronization, which exploits commercially available erbium-doped optical fiber and thanks to nonlinear polarization rotation in the loop, pulse behavior is achieved. It is possible to obtain pulses having full-width-at-half-maximum (FWHM) as short as 200fs, while preserving high energy. Our goal is the loop optimization and high repetition rate.

Research of ambient influence on novel broadband free-space optical systems

Main aim of this project stands in national cooperation with partners of Cost project IC1101 OPTICWISE, which should lead to development of a new methodology for atmospheric parameters reconnaissance based on measurement of free-space optical systems utilizing adaptive approaches. Large measurement campaign including two optical links WaveBridge 500 by Plaintree, 4-beam optical wireless link FlightStrata G od LightPointe (1.25 Gbps, VCSEL at 850 nm) and approximately 400m long link MRV Telescope 700. Parallel measurement in microwave region (5GHz link Mikrotik) is being carried out, atmospheric parameters are being measured by two metrological stations and turbulent environment close to buildings is analyzed based on temperature gradient obtained by special sensor link and also based on radiometric noise temperature measurement. In analyses, the meteoradar database is utilized; containing rain intensity behavior in the area of 250x250km (Czech Republic) with 1km step and time step of 1min for a 3-year period.

Visible light communications (VLC)

In recent years, visible light communications (VLC) has rapidly gained interest among research communities worldwide. It is an emerging technology for future high capacity communication links utilizing the visible range of the electromagnetic spectrum (~370 . 780 nm), which is not only license free, but free from spectral overcrowding unlike radio frequencies (RF). VLC utilizes light-emitting diodes (LEDs), modulating them at high speeds that are much faster than the human eye can detect, to simultaneously provide data transmission and room illumination. A major challenge in VLC is the LED modulation bandwidths, which are limited to a few MHz. However, gigabit speed transmission links have already been demonstrated.

Concurrently, organic LEDs (OLEDs) have been the focus of enormous attention for solid-state lighting applications due to their advantages over conventional LEDs such as ultra-low costs, mechanical flexibility and large photoactive areas. As a result, researchers are starting to investigate the performance of OLEDs in VLC systems, which is a very challenging research area, as OLED bandwidths can be approximately three orders of magnitude lower than their LED counterparts. Our group works on development of such VLC links to drive both LEDs and OLEDs in order to implement broadcasting networks featuring advanced modulation formats such as orthogonal frequency division multiplexing (OFDM) or carrier-less amplitude and phase modulation (CAP). We have many international academic and industrial collaborations with world leading research groups in the field of VLC, including Northumbria University and University College London (UCL) or University of Bristol.

Who supports our research?

  • COST project IC1101 Optical Wireless Communications - An Emerging Technology, OPTICWISE,http://www.cost.eu/domains_actions/ict/Actions/IC1101(link is external)
  • Wideband Optical Source Based on Soft-glass Fibers (in cooperation with SQS, fiber optics a.s), TACR grant TA04010220
  • Fiber optic detection of liquids (in cooperation with SQS, fiber optics a.s), TACR grant TA03010060
  • Optical packet switch (in cooperation with SQS, fiber optics a.s, IFE AV ČR), TAČR grant TA01011105
  • TACR - Centre of competence TE02000202 Advanced sensors and sensor data processing methods (our team - leading Working Package 6), external academic participants from University of West Bohemia, Brno University of Technology and industrial participants from AZD Praha, Honeywell International s.r.o., SQS Fiber optics, LESIKAR, a.s. and Safibra
  • Research of Ambient Influences on Novel Broadband Optical Wireless Systems - RAINBOWS, MŠMT COST_CZ project LD12058
  • Centre for quasi-optical systems and terahertz spectroscopy, project LC06071 (with VŠCHT and VUT)
  • Quadrupole Interactions as a Powerful Tool for the Conformational and Structural Analyses of Biochemically and Astrophysically Important Molecules (with VŠCHT), GAČR project GAP206/10/2182
  • The Influence of the Atmosphere on Electromagnetic Wave Propagation for Broadband Stratospheric Links, GAČR project GP102/08/P346
  • Optical and microwave detection systems, CTU project SGS14/190/OHK3/3T/13

Who do we cooperate with?

Czech research teams and industrial partners
  • SQS Vláknová optika a.s.
  • Ústav fotoniky a elektroniky AV ČR, v. v. i.
  • SITEL, spol. s.r.o.
  • T-Mobile Czech Republic a.s.
  • Kabelovna Kabex a.s.
  • OFA, s.r.o.
  • PROFiber Networking s.r.o.
  • NETWORK GROUP, s.r.o.
  • Vysoké učení technické v Brně
  • Vysoká škola báňská-Technická univerzita Ostrava
  • Vysoká škola chemicko-technologická v Praze
  • Czech Metrology Institute
International teams
  • Northumbria University, Newcastle UK
  • University of Southampton
  • University of Bristol
  • University College London
  • University of Edinburgh
  • University of Oxford
  • Ecole Centrale Marseille, Institut Fresnel, Francie
  • RWTH Aachen
  • Politecnico di Milano
  • Hong Kong Polytechnic University
  • Ozyegin University Turecko
  • Cork Institute of Technology
  • University of Technology Graz

Selected publications

  • Perez, J. - Zvanovec, S. - Ghassemlooy, Z. - Popoola, W. O., Experimental characterization and mitigation of turbulence induced signal fades within an ad-hoc FSO network, Optics Express, vol. 22, no. 3, p. 3208-3218, 2014.
  • Pisarik, M. - Peterka, P. - Zvanovec, S. - Baravets, Y. - Todorov, F. - Kasik, I. - Honzatko, P., Fused fiber components for .eye-safe. spectral region around 2 micrometers, Optical and Quantum Electronics, vol. 46, pp. 603-611, 2014.
  • Haigh, P. A. - Burton, A. - Werfli, K. - Minh, H. L. - Bentley, E. - Chvojka, P. - Popoola, W. O. - Papakonstantinou, I. - Zvánovec, S., A Multi-CAP Visible Light Communications System with 4.85 b/s/Hz Spectral Efficiency, IEEE Journal on Selected Areas in Communications, accepted for publications...
  • Bohata, J. - Pisarik, M.- Zvanovec, S. - Peterka, P., Reliability of Aircraft Multimode Optical Networks, Optical Engineering, vol. 53, no. 9, 2014
  • Komanec, M. - Skoda, P. - Sistek, J. - Martan, T., Data Transparent and Polarization Insensitive Optical Packet Switch based on Fibers with Enhanced Nonlinearity, Radioengineering, vol. 23, no. 3, pp. 768-775, 2014.
  • Rajbhandari, S. . Ghassemlooy, Z. . Haigh, P. A. . Kanesan, T., Experimental Error Performance of Modulation Schemes under a Controlled Laboratory Turbulence FSO Channel, IEEE Journal of Lightwave Technology, accepted for publications...
  • Zvanovec, S. - Perez, J. - Ghassemlooy, Z. - Rajbhandari, S. - Libich, J. , Route diversity analyses for free-space optical wireless links within turbulent scenarios(link is external), Optics Express, vol. 21, Issue 6, pp. 7641-7650, 2013.
  • Skoda, P. - Radil, J. - Vojtecht, J. - Hula, M.: Analyses of 100 Gbps Coherent System Performances. Radioengineering. 2013, vol. 2, no. 22, p. 632-637. ISSN 1210-2512.
  • Libich, J. - Zvánovec, S.: Influences of Turbulences in Near Vicinity of Buildings on Free-space Optical Links. IET Microwaves, Antennas & Propagation. 2011, vol. 9, no. 5, p. 1039-1044. ISSN 1751-8725.
  • Komanec, M. - Honzátko, P. - Zvánovec, S.: Single-shot All-optical Sampling Oscilloscope using a Polarization-maintaining Resonator for Pulse Replication. Microwave and Optical Technology Letters. 2010, vol. 52, no. 11, p. 2452-2456. ISSN 0895-2477.
  • Zvánovec, S. - Pechač, P.: Validation of Rain Spatial Classification for High Altitude Platform Systems. IEEE Transactions on Antennas and Propagation. 2011, vol. 59, no. 7, p. 2746-2750. ISSN 0018-926X.
  • Černý, P. - Piksa, P. - Zvánovec, S. - Kořínek, T. - Kabourek, V.: Improved axial feeding of Fabry-Perot resonator for high-resolution spectroscopy applications. Microwave and Optical Technology Letters. 2011, vol. 53, no. 11, p. 2456-2462. ISSN 0895-2477.
  • Kelleher, B. - Bonatto, C. - Škoda, P. - Hegarty, S. P. - Huyet, G.: Excitation Regeneration in Delay-coupled Oscilators. Physical Review E. 2010, vol. 81, no. 3, p. 036204-1-036204-5. ISSN 1539-3755.
  • Zvánovec, S. - Černý, P. - Piksa, P. - Kořínek, T. - Pechač, P. - et al.: The use of the Fabry-Perot interferometer for high resolution microwave spectroscopy. Journal of Molecular Spectroscopy. 2009, vol. 256, no. 1, p. 141-145. ISSN 0022-2852.

Responsible person: doc. Ing. Milan Polívka, Ph.D.