Lidé
doc. Ing. Leoš Boháč, Ph.D.
Všechny publikace
Highly variable FBG Interrogator with Electro-Optical Attenuation and Time Delay
- Autoři: Ing. Jiří Weiss, Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D., Sasek, L.
- Publikace: IEEE Sensors Letters. 2023, 7(11), ISSN 2475-1472.
- Rok: 2023
- DOI: 10.1109/LSENS.2023.3321009
- Odkaz: https://doi.org/10.1109/LSENS.2023.3321009
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
In this letter, we present a Fiber-Bragg Grating (FBG) interrogator combining wavelength and time division multiplexing to increase the number of interrogation up to 800 independent gratings. The unit consists of a super luminescent light emitting diode, a variable electro-optical attenuator and a spectrometer. The wavelength range is 85 nm spanning through the S, C, and L optical communication bands. High variability is assured by independent settings of time delay and optional signal enhancement for each individual time window with simultaneous wavelength multiplexing. The variability of the setup is advantageous for such an application as in civil and mechanical engineering where large numbers of gratings or groups of gratings are used and allows to measure a wide range of setups of FBGs.
Non-stationary Events Detection Based on Extrema Value Theory
- Autoři: Ing. Radek Mařík, CSc., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 2018 5th International Conference on Systems and Informatics (ICSAI). Piscataway: IEEE, 2018. p. 889-894. ISBN 978-1-7281-0120-0.
- Rok: 2018
- DOI: 10.1109/ICSAI.2018.8599319
- Odkaz: https://doi.org/10.1109/ICSAI.2018.8599319
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
A detection of anomaly events in a non-stationary time series resembling vibration aspects is often based on the signal envelope. Both commonly used approaches, i.e. the Hilbert transform and the empirical mode decomposition, lead to high processing power requirements. As anomalies are assumed to be rare, we propose simplified methods based on extreme value theory that enable trend corrections and anomaly event occurrence detection. Both methods are based on the upper and lower envelope approximations that are constructed using maxima and minima limits of the signal.
Linear Watershed Algorithm for 1D Real Signals
- Autoři: Ing. Radek Mařík, CSc., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Systems and Informatics (ICSAI), 2017 4th International Conference on. Tianjin: IEEE, 2017. p. 1103-1108. ISBN 978-1-5386-1106-7.
- Rok: 2017
- DOI: 10.1109/ICSAI.2017.8248450
- Odkaz: https://doi.org/10.1109/ICSAI.2017.8248450
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The watershed transformation is widely used, a powerful tool for the segmentation of 2D and 3D images. In this paper we propose a fast linear one sweep algorithm generating all possible extreme weighted connected components in 1D real value signal.We also show how such a post-order list of connected components can be converted into a component tree in linear time. Furthermore, we demonstrate how some features of the connected components can be computed again in linear time.
On Application of Least-delay Variation Problem in Ethernet Networks Using SDN Concept
- Autoři: Hégr, T., Kozák, M., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Advances in Electrical and Electronic Engineering. 2016, 14(4), 397-404. ISSN 1336-1376.
- Rok: 2016
- DOI: 10.15598/aeee.v14i4.1807
- Odkaz: https://doi.org/10.15598/aeee.v14i4.1807
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The goal of this paper is to present an application idea of SDN in Smart Grids, particularly, in the area of L2 multicast as defined by IEC 61850-9-2. Authors propose an Integer Linear Formulation (ILP) dealing with a Least-Delay-Variation multicast forwarding problem that has a potential to utilize Ethernet networks in a new way. The proposed ILP formulation is numerically evaluated on random graph topologies and results are compared to a shortest path tree approach that is traditionally a product of Spanning Tree Protocols. Results confirm the correctness of the ILP formulation and illustrate dependency of a solution quality on the selected graph models, especially, in a case of scale-free topologies.
On the Highly Stable Performance of Loss-Free Optical Burst Switching Networks
- Autoři: Kozák, M., Jaumard, B., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Advances in Electrical and Electronic Engineering. 2016, 14(3), 325-329. ISSN 1336-1376.
- Rok: 2016
- DOI: 10.15598/aeee.v14i3.1781
- Odkaz: https://doi.org/10.15598/aeee.v14i3.1781
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Increase of bandwidth demand in data networks, driven by the continuous growth of the Internet and the increase of bandwidth greedy applications, raise the issue of how to support all the bandwidth requirements in the near future. Three optical switching paradigms have been defined and are being investigated: Optical Circuit Switching (OCS); Optical Packet Switching (OPS); and Optical Burst Switching (OBS). Among these paradigms, OBS is seen as the most appropriate solution today. However, OBS suffers from high burst loss as a result of contention in the bufferless mode of operation. This issue was investigated by Coutelen et al., 2009 who proposed the loss-free CAROBS framework whereby signal convertors of the optical signal to the electrical domain ensure electrical buffering. Convertors increase the network price which must be minimized to reduce the installation and operating costs of the CAROBS framework. An analysis capturing convertor requirements, with respect to the number of merging flows and CAROBS node offered load, was carried out. We demonstrated the convertor location significance, which led to an additional investigation of the shared wavelength convertors scenario. Shared wavelength convertors significantly decrease the number of required convertors and show great promise for CAROBS. Based on this study we can design a CAROBS network to contain a combination of simple and complex nodes that include none or some convertors respectively, a vital feature of network throughput efficiency and cost.
Optical Fiber Sensor Networks Floating in IT Cloud
- Autoři: doc. Ing. Leoš Boháč, Ph.D., Kozák, M.
- Publikace: Proceedings of the 2016 17th International Conference on Mechatronics - Mechatronika (ME) 2016. Prague: Czech Technical University in Prague, Faculty of Electrical Engineering, 2016. pp. 526-532. ISBN 978-80-01-05883-1.
- Rok: 2016
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Optical fiber sensors are now practically deployed in special disciplines such as structural health monitoring, distributed vibrations sensing, surveillance and even at other fields. Thought interesting technology, there are still many persistent barriers for its massive wide scale utilization. Should optical fiber sensing system play more dominant role in the future as compared to more traditional systems, it is necessary to significantly lower the costs of the optical sensor units and also consider more distributed deployment architectures based on optical fiber sensor networks with system build intelligence assuring interfacing with traditional sensing systems. With that said, we need to have also clever signal acquisition systems. In this article, we propose new optical sensor architecture based on fusion of the optical sensor networks, internet of things and IT cloud paradigms and evaluate its possible advantages.
Enhancing Availability of Services Using Software-Defined Networking
- Autoři: Klepáč, M., Hégr, T., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Advances in Electrical and Electronic Engineering. 2015, 13(5), 522-528. ISSN 1336-1376.
- Rok: 2015
- DOI: 10.15598/aeee.v13i5.1498
- Odkaz: https://doi.org/10.15598/aeee.v13i5.1498
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The immense growth of client requirements imposed on data centre and cloud providers results in a conflict with traditional networking concepts lacking the required agility. In order to promote flexibility, which data centre providers promise to their clients, this discrepancy needs to be resolved, for instance by employing the novel concept of Software Defined Networking (SDN). This paper utilises this concept in order to minimise service downtime while performing live virtual machine migration. The work is aimed at small/medium-sized data centres and hence the findings are based on real communication patterns found in such environments. Results show that packet loss is slightly diminished while available throughput is increased thanks to the proactive approach taken during network topology changes when compared to the traditional approach based on L2 forwarding.
How to Enhance the Efficiency of Loss-Less Optical Burst Switching Networks with the Streamline Effect
- Autoři: Kozák, M., Jaumard, B., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Advances in Electrical and Electronic Engineering. 2015, 13(4), 407-416. ISSN 1336-1376.
- Rok: 2015
- DOI: 10.15598/aeee.v13i4.1476
- Odkaz: https://doi.org/10.15598/aeee.v13i4.1476
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
With the ongoing steady traffic increase in the Internet, the wavelength usage of the supporting optical networks is a critical network efficiency parameter. Therefore, this paper suggests a way how to efficiently and economically achieve this goal in the context of optical burst switching, a very promising technology that has been proposed to overcome the shortcomings of conventional WDM deployment, such as lack of fine bandwidth granularity in wavelength routing and electronic speed bottlenecks in the presence of bursty traffic. In order to mitigate the burst loss and achieve high network efficiency we adapt the loss-less paradigm defined by Coutelen et al. (2010), i.e., the CAROBS framework. In classical OBS networks, the streamline effect ensures a very low level of contention, i.e., efficient transmission, hence we define a routing guided only by the streamline effect. The resulting routing problem is formulated as an optimization model which is solved using a decomposition technique to increase the scalability of the solution process.
Measurement o f Switching Latency in High Data Rate Ethernet Networks
- Autoři: Hégr, T., Vozňák, M., Kozák, M., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Elektronika ir Elektrotechnika. 2015, 21(3), 73-78. ISSN 1392-1215.
- Rok: 2015
- DOI: 10.5755/j01.eee.21.3.10445
- Odkaz: https://doi.org/10.5755/j01.eee.21.3.10445
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The paper deals with a methodology of switching latency measurement in switched Ethernet networks. The switching latency is parameter necessary for simulation and design of low-latency networks that are often intended for real-time control inherent to many industrial applications. The proposed measurement methodology provides a simple way of switching the latency determination and vendor quoted latency values verification directly at the physical layer.
On the Efficiency of Stream Line Effect for Contention Avoidance in Optical Burst Switching Networks
- Autoři: Kozák, M., Jaumard, B., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Optical Switching and Networking. 2015, 18(1), 35-50. ISSN 1573-4277.
- Rok: 2015
- DOI: 10.1016/j.osn.2015.03.002
- Odkaz: https://doi.org/10.1016/j.osn.2015.03.002
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The OBS paradigm is a very promising all-optical transmission paradigm; however, OBS still suffers from burst losses because of burst contentions. Consequently, several loss-less approaches were proposed by various authors. In this paper, we investigate further one of them, the CAROBS framework, originally proposed by Coutelen et al. (2010). CAROBS uses electronic buffering for contention resolution that requires careful routing strategies in order not to entail too many new contentions, and then buffering as a result of these contentions. This led us to look at the stream-line effect in order to devise efficient routing. The streamline effect has not yet been much exploited except for its straightforward implementation. Firstly, we empirically verify the impact of buffering within a stream-line effect framework, and discuss the significance of the results. Secondly, we devise an optimized request provisioning taking advantage of the stream-line effect with a compact integer linear programming (ILP) model, and then with a decomposition ILP model. Thirdly, we proceed with extensive numerical experiments. We run a time domain analysis of the routing obtained from the last ILP model for four referential network topologies. Results show very appealing properties of the CAROBS framework, and in particular, a wavelength efficiency higher than 70%.
Synthesizing TCP Data Traffic From Industrial Networks For Simulations
- Autoři: Hégr, T., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Advances in Electrical and Electronic Engineering. 2015, 13(5), 536-544. ISSN 1336-1376.
- Rok: 2015
- DOI: 10.15598/aeee.v13i5.1501
- Odkaz: https://doi.org/10.15598/aeee.v13i5.1501
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
In this paper, authors deal with a problem of an impaired TCP stream reconstruction from a real-world captured data. The goal is to obtain an original application data. The data are synthesized to be used as an input for a traffic generator. Authors describe a way to solve specific problems at transport and application layers during the reconstruction of an impaired TCP stream. The traffic reconstruction is oriented to IEC 60870-5-104 protocol on top of TCP. The evaluation of proposed algorithms shows that it is possible to estimate original time dependencies between received and dispatched messages with high accuracy.
VM Migration Measurement and Failure Detection
- Autoři: Kukrál, T., Kozák, M., Hégr, T., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 38th International Conference on Telecommunications and Signal Processing. Piscataway: IEEE, 2015. p. 285-288. ISSN 1805-5435. ISBN 978-1-4799-8498-5.
- Rok: 2015
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
This paper tackles migration of virtual machines, and the migration reliability. The migration is seen as a reliable operation, but this assumption is not true and almost no work on this topic has been published. In order to quantify the migration successful rate, we designed and implemented framework for autonomous migration evaluation, network availability testing, and reporting. This framework is introduced in this paper and its configuration is described. This framework is very unique because of its modular architecture and orchestration independence. We use this framework in order to quantify the migration successful rate, so we prepare statistically reliable test. Based on this test we formulated a mathematical hypothesis and we found that only 87% of migrations successfully finish. This is very low value which is very alarming because the experiment was carried out on the testbed which is based on the most recent technologies.
Fiber Optic and Free Space Michelson Interferometer - Principle and Practice
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D., Zelený, R.
- Publikace: Optical Sensors - New Developments and Practical Applications. Rijeka: InTech, 2014. p. 1-22. ISBN 978-953-51-1233-4.
- Rok: 2014
- DOI: 10.5772/57149
- Odkaz: https://doi.org/10.5772/57149
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Michelson interferometer is used in metrology of small amplitude nonelectric physical quantities for its accuracy, noncontact and noninvasive procedure. It is broadly used in sensor applications. There are many papers assuming the use of an interferometer and focusing on measured results, but there are not many works offering practical knowledge on how to construct and run Michelson interferometer. In this chapter we discuss wide range of aspects, which greatly facilitate the launch of Michelson interferometer in in-situ conditions.
Impact of Nodal Centrality Measures to Robustness in Software-Defined Networking
- Autoři: Hégr, T., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Advances in Electrical and Electronic Engineering. 2014, 12(4), 252-259. ISSN 1336-1376.
- Rok: 2014
- DOI: 10.15598/aeee.v12i4.1208
- Odkaz: https://doi.org/10.15598/aeee.v12i4.1208
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The paper deals with the network robustness from the perspective of nodal centrality measures and its applicability in Software-Defined Networking (SDN). Traditional graph characteristics have been evolving during the last century, and numerous of less-conventional metrics was introduced trying to bring a new view to some particular graph attributes. New control technologies can finally utilize these metrics but simultaneously show new challenges. SDN brings the fine-grained and nearly online view of the underlying network state which allows to implement an advanced routing and forwarding. In such situation, sophisticated algorithms can be applied utilizing pre-computed network measures. Since in recent version of SDN protocol OpenFlow (OF) has been revived an idea of the fast link failover, the authors in this paper introduce a novel metric, Quality of Alternative Paths centrality (QAP). The QAP value quantifies node surroundings and can be with an advantage utilized in algorithms to indicate more robust paths. The centrality is evaluated using the node-failure simulation at different network topologies in combination with the Quality of Backup centrality measure.
Precise optical differential thermometer sensor based on interferometric measurement of thermal expansion coefficient
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D., Zelený, R., Davídková Antošová, M.
- Publikace: Optical Sensing and Detection III. Bellingham: SPIE, 2014. SPIE Proceedings Volume 9141. ISBN 9781628410891.
- Rok: 2014
- DOI: 10.1117/12.2054346
- Odkaz: https://doi.org/10.1117/12.2054346
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Knowing a thermal expansion coefficient and measured exact thermal expansion, it is possible to design a very sensitive sensor measuring temperature differential. A Michelson interferometer is used to determine temperature changes. It measures linear expansion on a metal object, e.g. a copper rod, as a change in length in response to a change in temperature. Based on the obtained interferograms and knowing the value of thermal expansion coefficient, temperature differential can be calculated. The accuracy of the procedure can be determined by using the exact differential method based on the measurement errors for linear expansion, and initial length. The contribution of this paper is the employment of Michelson interferometer to design a very sensitive differential thermometer measuring with the accuracy of one thousandth degree Celsius. It results from the achieved precision of measuring the optical path length changes in the range of hundreds nanometers. The advantage of this sensor is its precision and noncontact procedure.
Procedure to Measure of the Data Transmission Speed in LTE Mobile Networks
- Autoři: doc. Ing. Jiří Vodrážka, Ph.D., Ing. Zbyněk Kocur, Ph.D., Ing. Jiří Holeček, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 16th Mechatronika 2014. Brno: Brno University of Technology, 2014. pp. 644-647. ISBN 978-80-214-4817-9.
- Rok: 2014
- DOI: 10.1109/MECHATRONIKA.2014.7018335
- Odkaz: https://doi.org/10.1109/MECHATRONIKA.2014.7018335
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The methodology specifies a procedure for measuring of data transmission speed for the assessment of compliance with the conditions proscribed for holders of licenses for usage frequencies in the 800, 1800 and 2600 MHz bands, for the operation of mobile systems according to the LTE standard. The achievement of specified data transmission speed is a key parameter for evaluating the coverage of the Czech Republic mobile signal for the LTE standard systems. The methodology allows to the Czech telecommunication regulatory body (Czech Telecommunication Office – CTO), telecommunications operators and end users unambiguous determination of values of speed of data transmission in mobile networks in accordance with standard LTE. The methodology treats the issue comprehensively and specifies in initial conditions of measurement, measurement procedures (both for stationary measurement and in motion measurement) and related calculations. The team of authors from the Czech Technical University in Prague created a substantial part of the described methodology.
Fault Tolerant Ethernet Based Network for Time Sensitive Applications in Electrical Power Distribution Systems
- Autoři: doc. Ing. Leoš Boháč, Ph.D., doc. Ing. Jiří Vodrážka, Ph.D.,
- Publikace: Advances in Electrical and Electronic Engineering. 2013, 11(5), 321-326. ISSN 1336-1376.
- Rok: 2013
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The paper analyses and experimentally verifies deployment of Ethernet based network technology to enable fault tolerant and timely exchange of data among a number of high voltage protective relays that use proprietary serial communication line to exchange data in real time on a state of its high voltage circuitry facilitating a fast protection switching in case of critical failures. The digital serial signal is first fetched into PCM multiplexer where it is mapped to the corresponding E1 (2 Mbit/s) time division multiplexed signal. Subsequently, the resulting E1 frames are then packetized and sent through Ethernet control LAN to the opposite PCM demultiplexer where the same but reverse processing is done finally sending a signal into the opposite protective relay. The challenge of this setup is to assure very timely delivery of the control information between protective relays even in the cases of potential failures of Ethernet network itself. The tolerance of Ethernet network to faults is assured using widespread per VLAN Rapid Spanning Tree Protocol potentially extended by 1+1 PCM protection as a valuable option.
Intrinsic Fiber Optic Sensor Analysis for Temperature, Vibration and Strain Sensing
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 15th International Conference on Research in Telecommunication Technologies. Bratislava: Slovak University of Technology in Bratislava, 2013. pp. 77-82. ISBN 978-80-227-4026-5.
- Rok: 2013
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The subject of this paper is the analysis of the intrinsic fibre optic sensor potentially useful for measuring ambient quantities as strain, stress, vibration and temperature. The quantitative response of these ambient effects is analyzed and evaluated. It is shown when the optical fibre is exposed to the external strain and heat it results in the phase change of the propagated light. However, it is not possible to measure phase variations directly by the optoelectronic detectors as they are able to detect only the average optical power. Thus, this paper also debates interferometric detection method to convert phase variations induced by those ambient effects to the optical power and electric current that is easily measurable.
Methodology of the Direct Measurement of the Switching Latency
- Autoři: Hégr, T., doc. Ing. Leoš Boháč, Ph.D., Ing. Zbyněk Kocur, Ph.D., Vozňák, M., Chlumský, P.
- Publikace: Przeglad Elektrotechniczny. 2013, 89(7/2013), 59-63. ISSN 0033-2097.
- Rok: 2013
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The article provides a measurement methodology based on the related RFCs. It brings a solution of determining the switching la tency on the physical layer using common measuring devices. As a proof of concept were done a number of the experimental measurements, including analysis of the results. Switching latency is an important performance parameter which participates in the decision-making whether to deploy the switch to low-latency environments. This is especially important in industrial networks for real-time systems involving smart grids. Determine the value of the switching latency is also an important step in the eventual deployment of the OpenFlow technology on this field.
On Regenerator Placement in Loss-less Optical Burst Switching Networks
- Autoři: Kozák, M., Jaumard, B., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 36th International Conference on Telecommunications and Signal Processing. Piscataway: IEEE, 2013. pp. 311-315. ISSN 1805-5435. ISBN 978-1-4799-0402-0.
- Rok: 2013
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Optical burst switching suffers from burst contention, which can occur even under low load. This issue was investigated by Coutelen et al., 2009 and led to the CAROBS framework. Therein, the authors considered burst concatenation, and with the recourse to wavelength conversion throughout signal regeneration, can resolve all burst contentions, offering then a loss-free OBS framework. However, CAROBS does not take into account physical layer impairments, which can lead to OSNR degradation and ultimately optical burst losses. In this paper, we investigate how many additional optical regenerators need to be introduced in order to overcome those physical impairments in translucent OBS networks. We propose two different heuristics in order to optimize the regenerator locations. Numerical results are presented in order to both investigate the number of regenerators that need to be installed in order to minimize burst loss, ultimately to reach no burst loss, and the signal degradation due to physical layer impairments.
OpenFlow Deployment and Concept Analysis
- Autoři: Hégr, T., doc. Ing. Leoš Boháč, Ph.D., Uhlíř, V., Chlumský, P.
- Publikace: Advances in Electrical and Electronic Engineering. 2013, 11(5), 327-335. ISSN 1336-1376.
- Rok: 2013
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Terms such as SDN and OpenFlow (OF) are often used in the research and development of data networks. This paper deals with the analysis of the current state of OpenFlow protocol deployment options as it is the only real representative protocol that enables the implementation of Software Defined Networking outside an academic world. There is introduced an insight into the current state of the OpenFlow specification development at various levels is introduced. The possible limitations associated with this concept in conjunction with the latest version (1.3) of the specification published by ONF are also presented. In the conclusion there presented a demonstrative security application addressing the lack of IPv6 support in real network devices since most of today's switches and controllers support only OF v1.0.
Problem of Channel Utilization and Merging Flows in Buffered Optical Burst Switching Networks
- Autoři: Kozák, M., Jaumard, B., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Advances in Electrical and Electronic Engineering. 2013, 11(5), 426-432. ISSN 1336-1376.
- Rok: 2013
- DOI: 10.15598/aeee.v11i5.887
- Odkaz: https://doi.org/10.15598/aeee.v11i5.887
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
In the paper authors verify two problems of methods of operational research in optical burst switching. The first problem is at edge node, related to the medium access delay. The second problem is at intermediate node related to buffering delay. A correction coefficient K of transmission speed is obtained from the first analysis. It is used in to provide full-featured link of nominal datarate. Simulations of the second problem reveal interesting results. It is not viable to prepare routing and wavelength assignment based on end-to-end delay, i.e. link's length or number of hops, as commonly used in other frameworks (OCS, Ethernet, IP, etc.) nowadays. Other parameters such as buffering probability must be taken into consideration as well. Based on the buffering probability an estimation of the number of optical/electrical converters can be made. This paper concentrates important traffic constraints of buffered optical burst switching. It allows authors to prepare optimization algorithms for regenerators placement in CAROBS networks using methods of operational research.
An interferometric Measurement of Thermal Expansion Coefficient of Materials
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D., Zelený, R., Kraus, S.
- Publikace: Research in Telecommunication Technologies Conference proceedings and Workshop. Žilina: Žilinská univerzita, 2012. pp. 169-174. ISBN 978-80-554-0570-4.
- Rok: 2012
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
A Michelson-type visible spatial interferometric method is used to measure a thermal expansion coefficient of metals. A He-Ne laser beam is split to create an inreferometric pattern consisting of a reference signal and a measuring signal coming from a copper rod, terminated with a 100% mirror, which can potentially be replaced by any other solid state resistant to heating. Since temperature is responsible for the increased length of the copper rod, the position of a mirror is changed and consequently, the interferogram is modified. Based on this, thermal expansion coefficient can be predicted and the type of material can be specified. In addition, heating and cooling processes exhibit a different time variation, which allows distinguishing between them employing this accurate and non-contact optical method.
Calculation of observational errors for an interferometric measurement by using exact differential method
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 24th Conference and Exhibition on Optical Communications 2012 Proceedings. Praha: Agentura Action M, 2012. pp. 35-39. ISBN 978-80-86742-36-6.
- Rok: 2012
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
An optical interferometric method is used to measure a thermal expansion coefficient of a copper rod. Heating process is responsible for the increased length of the investigated rod, placed in a measuring arm of an interferometer. Based on obtained interferograms and the measurement of initial length and temperature changes, thermal expansion coefficient is calculated. Potential observation errors originated at the measurements of initial length and temperature are considered. Mathematical apparatus as well as sample calculations of observational errors and the estimation of overall accuracy of measured thermal expansion coefficient are obtained by using an exact differential method.
Fiber Optic Sensory System for Area Perimeter Guarding with Speckle Detection
- Autoři: doc. Ing. Leoš Boháč, Ph.D., Šašek, L., Bakala, B.
- Publikace: 24th Conference and Exhibition on Optical Communications 2012 Proceedings. Praha: Agentura Action M, 2012. pp. 26-30. ISBN 978-80-86742-36-6.
- Rok: 2012
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Vibration detection is widely used in many areas in our everyday life. Several methods exist to measure vibration. Particularly interesting is to use light propagating in optical fiber for spatially distributed or locally induced vibration measurement. This paper deals with the results achieved in currently running project that aims to test and practically implement vibration sensors using optical fibers with detection of spatially filtered speckle light patterns of multimode fiber driven by a coherent laser source light. Primary anticipated area of practical implementation is continuous guarding of critical infrastructures. In aforementioned project we are using the multi zoned speckle detection so that an intrusion event can be identified only per zone as whole and not yet at specific position in the zone itself. The results show that a speckle analysis is potentially applicable as an inexpensive method for sensing vibrations with optical fibers if suitable spatial light filtering at the fiber output is used to achieve reasonable sensitivity and intelligent correlation algorithms are found. In this paper we show some practical "in field" experimental measurements done in one zone system only.
Selected Aspects of Interferometric Measurements of Non-electric Low-amplitude Physical Quantities
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Proceedings of 15th Mechatronika 2012. Praha: Czech Technical University in Prague, 2012. pp. 285-290. ISBN 978-80-01-04987-7.
- Rok: 2012
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
A Michelson-type visible spatial interferometric method is used to measure very high speed vibrations of a bass-reflex loudspeaker, and further its resonant frequency. The goal of investigation is to create the model for measurement of non-electric, low-amplitude, high-speed alternating physical quantities. The contribution of this paper is this new application area.
Strategies For Regenerators Placement In Impairment Aware Optical Burst Switching Networks
- Autoři: Kozák, M., Jaumard, B., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 24th Conference and Exhibition on Optical Communications 2012 Proceedings. Praha: Agentura Action M, 2012. pp. 8-12. ISBN 978-80-86742-36-6.
- Rok: 2012
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Current optical networks suffer from limited performance as all frames in optical network nodes are processed in an electrical domain which is often very time-consuming and complex task. So in this sense the electrical conversion is considered as a bottleneck in future terabit optical networks. A variety of new all-optical network frameworks have been recently introduced to cope with this limitation. Optical burst switching is one all-optical network framework which is seemed to be the most feasible but yet not being fully ready for its deployment in practice. Optical burst switching is ideal for networks with bursty traffic load pattern such as in access or metro network. These networks are usually geographically extensive so physical layer impairments can really be an issue. Although optical regenerators can resolve the problem of optical impairments, they are still very expensive and consequently their installation in practice is very rare and limited. Regenerators also break optical network transparency and turn the all-optical paradigm into translucent one.
Stress-induced Birefringent Photonic Crystal Fiber
- Autoři: Kraus, S., Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Research in Telecommunication Technologies Conference proceedings and Workshop. Žilina: Žilinská univerzita, 2012. pp. 189-192. ISBN 978-80-554-0570-4.
- Rok: 2012
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The goal of this paper is to present a novel single-material photonic crystal fiber utilizing stress-induced birefringence for detection of unidirectional load applied onto the fiber. Particular contributions to the birefringence, which are the deformation of fiber's geometry and stress-induced variation in refractive index, are considered in the proposed fiber.
A New Optical Signal To Noise Ratio Based OMNeT++ Fiber Approximation Model
- Autoři: Kozák, M., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 13th International Conference on Research in Telecommunication Technologies 2011. Brno: VUT v Brně, Fakulta elektrotechniky a komunikačních technologií, 2011. pp. 162-164. ISBN 978-80-214-4283-2.
- Rok: 2011
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
This paper deals with impairment aware rating and wavelength assignment problem in all optical networks. It provides information about simulation possibilities in classical optical network simulators and suggests implementation of simplified model that may be used in an environment of an Event Driven Simulator (EDS) like OMNeT++. The paper provides basic information about simulation methods used in classical commercial software and emphasizes important parts of these methods that must be preserved and that can be simplified or avoided. Based on this a new model is introduced that uses optical signal to noise ratio (OSNR) for bit error rate (BER) estimation. Model evaluation is carried out on elementary network consisting of traffic generator, sink and above mentioned new model. The fiber link length granularity of 10 km is used and BER is obtained for two different optical modulations.
Model of Impairment-aware Routing Algorithm for Generalized Multi-Protocol Label Switching
- Autoři: Kozák, M., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 23rd Conference and Exhibition on Optical Communications 2011 - Scientific Section Proceedings. Praha: Agentura Action M, 2011. pp. 30-33. ISBN 978-80-86742-32-8.
- Rok: 2011
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
This paper deals with impairment aware routing and wavelength assignment problem in all optical networks. It provides information about current state of the art of GMPLS impairment aware interface for patch computation. The paper gives suggestion to use OMNeT++ simulation tool for evaluation of routing and wavelength assignment problem especially in its enhanced version encompassing physical properties of fibers. The paper discusses nonexistence of models for simulations of impairment aware routing and wavelength assignment problem and thus suggests a model that could fulfill the gap. The model implementation is clearly described and mathematical evaluation of fiber model is provided. The evaluation is based on attenuation of fiber that causes optical signal to noise ratio (OSNR) and consequently bit error rate (BER) degradation. Evaluation is made using Artis OptSim simulator and OMNeT++. Measurement of BER is carried out using both simulators and results are compared. The correlation of results verifies that model is correct. The following discussion provides information about additional model extension and calculations of impairment aware routing and wavelength assignment problem for Generalized Multi-Protocol Label Switching framework.
The Fiber-optic Sensor for Perimeter Guarding
- Autoři: Hladík, J., Šašek, L., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 23rd Conference and Exhibition on Optical Communications 2011 - Scientific Section Proceedings. Praha: Agentura Action M, 2011. pp. 62-66. ISBN 978-80-86742-32-8.
- Rok: 2011
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
This paper deals with the practical application of the optical fiber sensors for the specific purpose of intrusion detection systems and the integrity protection of critical infrastructures. Currently, the use of security equipment is primarily based on metallic lines that generally integrate also surveillance cameras, free space detection lasers and other complicated security equipment. This paper shows one of the principles of using glass optical fibers as sensors for dynamic perimeter intrusion detection systems based on perturbation of the optical transmission properties of sensor zone fiber. The bending-pressure perturbations are used to induce optical speckle patterns at the end of sensing multimode fiber. These patterns are further spatially filtered by connected single mode fiber. The use of optical sensor systems has its advantages compared with conventional metallic systems that include stable parameters in time, potential greater guarding coverage due to low attenuation of the zone sensor driving fibers, passive mode of operation without using of active components in a guarded area, and great resistance to electromagnetic interference.
The Labelled Optical Burst Switching OMNeT++ Model With Accurate Time Offset Evaluation
- Autoři: Kozák, M., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Proceedings of the 11th International Conference Knowledge in Telecommunication Technologies and Optics. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2011. pp. 75-77. ISBN 978-80-248-2399-7.
- Rok: 2011
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
In this paper, problems of labelled optical burst switching are discussed. In purely optical networks a lightpath along which optical bursts are consequently transferred must be first dynamically set up using optical switches in nodes and switching information contained in the burst header itself. However, creation of the lightpath takes time due to technological limits of current switching elements. This time must be considered in a design of signalling protocol otherwise the data packets located at the front of the optical burst and sometimes even further are going to be lost. The OMNeT++ simulation models are proposed to solve these problems. The simple mathematical model was created as well to evaluate correct time offset required between optical burst header and its data payload that follows it.
Wykorzystanie środków obliczeniowych i multimedialnych w nauczaniu i badaniach w obszarze telekomunikacji
- Autoři: doc. Ing. Jiří Vodrážka, Ph.D., Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Nowoczesne Technologie w Dydaktyce. Kielce: Politechnika Swietokrzyska, 2011.
- Rok: 2011
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
W pracy przedstawiono narzędzia wykorzystywane w Katedrze Telekomunikacji dla elektronicznego wspomagania nauczania. System Class Server do zarządzania kształceniem przeznaczony jest dla istniejących programów nauczania, natomiast platforma Moodle wykorzystywana jest dla obsługi nowych programów kształcenia. Obok tekstu strukturalnego, równań, przykładów czy rycin, dostępne szablony umożliwiają umieszczanie interaktywnych elementów multimedialnych w postaci animacji, ścieżki dźwiękowej, wideo oraz testów. Za jeden z najbardziej zaawansowanych elementów uważać można integrację obliczeń teoretycznych, prowadzonych w środowisku Matlab Web Server, z drugiej strony jednym z najbardziej kompleksowych rozwiązań jest powiązanie wspomnianych narzędzi z zadaniami laboratoryjnymi typu online, do których możliwy jest zdalny dostęp wraz z możliwością konfiguracji na odległość, bez konieczności fizycznej obecności w laboratorium.
Wykorzystanie środków obliczeniowych i multimedialnych w nauczaniu i badaniach w obszarze telekomunikacji
- Autoři: doc. Ing. Jiří Vodrážka, Ph.D., Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Nowoczesne technologie w dydaktyce. Kielce: Politechnika Swietokrzyska, 2011. p. 308-316. ISBN 978-83-88906-73-2.
- Rok: 2011
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
W pracy przedstawiono narzędzia wykorzystywane w Katedrze Telekomunikacji dla elektronicznego wspomagania nauczania. System Class Server do zarządzania kształceniem przeznaczony jest dla istniejących programów nauczania, natomiast platforma Moodle wykorzystywana jest dla obsługi nowych programów kształcenia. Obok tekstu strukturalnego, równań, przykładów czy rycin, dostępne szablony umożliwiają umieszczanie interaktywnych elementów multimedialnych w postaci animacji, ścieżki dźwiękowej, wideo oraz testów. Za jeden z najbardziej zaawansowanych elementów uważać można integrację obliczeń teoretycznych, prowadzonych w środowisku Matlab Web Server, z drugiej strony jednym z najbardziej kompleksowych rozwiązań jest powiązanie wspomnianych narzędzi z zadaniami laboratoryjnymi typu online, do których możliwy jest zdalny dostęp wraz z możliwością konfiguracji na odległość, bez konieczności fizycznej obecności w laboratorium.
Analyzing of Data Flows at Czech Antarctic Station
- Autoři: Ing. Zbyněk Kocur, Ph.D., Kozák, M., Ing. Marek Neruda, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: TSP 2010 - 33rd International Conference on Telecommunications and Signal Processing. Budapest: Asszisztencia Szervező Kft., 2010. pp. 219-221. ISBN 978-963-88981-0-4.
- Rok: 2010
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Paper deals with data transmission behind polar circle with respect to multimedia content and reliable data transport. Two different transmission algorithms are discussed in the paper. The first one is common periodic transfer used for transmission of collected data. The second one is transmission on demand trigged by scientists in Czech Republic.
Digital Interpolator Implementation in VHDL
- Autoři: Kekrt, D., Podgorný, R., prof. Ing. Miloš Klíma, CSc., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: RTT 2010 Proceedings. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2010. pp. 168-173. ISBN 978-80-248-2261-7.
- Rok: 2010
- Pracoviště: Katedra telekomunikační techniky, Katedra radioelektroniky
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Anotace:
In this article we describe a creation, modeling, implementation and simulation of a digital interpolator. It will be used as a part of advanced radio transmission system. The input part of the system receiving part provides correct complex envelope sampling that is necessary for consequent signal processing. During the re-sampling, an interpolator co-operates with symbol timing estimator. It estimates correct sampling timing and controls an interpolator. We describe the process of interpolator modeling in Matlab in both floating and fixed point arithmetics for later implementation in the VHDL language for FPGA. The complete system was simulated in ISim, compared with the model and results are presented.
Direct Quadrature Frequency Synthesizer Implementation in VHDL
- Autoři: Kekrt, D., prof. Ing. Miloš Klíma, CSc., Podgorný, R., Zavrtálek, J., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Knowledge in Telecommunication Technologies and Optics - KTTO 2010. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2010. pp. 69-74. ISBN 978-80-248-2330-0.
- Rok: 2010
- Pracoviště: Katedra telekomunikační techniky, Katedra radioelektroniky
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Anotace:
In this article we describe a creation, modeling, implementation and simulation of a direct quadrature frequency synthesizer.We describe the process of synthesizer modeling in Matlab in both floating and fixed point arithmetics for later implementation in the VHDL language for FPGA. The complete functional block was implemented in the Xilinx Virtex6 FPGA device attached to analog radio front-end built of Analog Devices evaluation boards. The results on the front-end output was measured, presented and compared with the Matlab model.
Optimization of TCP Satellite Communication in Inmarsat Network
- Autoři: Ing. Zbyněk Kocur, Ph.D., Ing. Marek Neruda, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: The Sixth International Conference on Wireless and Mobile Communications (ICWMC 2010). Piscataway: IEEE, 2010. p. 544-548. ISBN 978-0-7695-4182-2.
- Rok: 2010
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The purpose of this paper is to present the improvements of packet data transmission via originally only voice oriented Inmarsat satellite network. The window size has been optimized to enable transferring files between the hosts in Inmarsat satellite network with increased throughput and also reduced transfer times.
Poly-phase Decimation Filter Implementation in VHDL
- Autoři: Kekrt, D., Podgorný, R., prof. Ing. Miloš Klíma, CSc., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: RTT 2010 Proceedings. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2010. pp. 155-160. ISBN 978-80-248-2261-7.
- Rok: 2010
- Pracoviště: Katedra telekomunikační techniky, Katedra radioelektroniky
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Anotace:
In this article we describe our effort to create, model, implement and simulate a poly-phase decimation filter. It is to be used as a part of advanced radio transmission system. We describe the process of modeling the filter in Matlab in both floating and fixed point arithmetic for later implementation in VHDL language for FPGA. The complete system is then being simulated in ISim, compared with the model and results are presented and evaluated.
Quadrature Linear Digital Modulator Implementation in VHDL
- Autoři: Kekrt, D., Podgorný, R., prof. Ing. Miloš Klíma, CSc., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Applied Electronic 2010. Pilsen: University of West Bohemia, 2010. pp. 153-158. ISSN 1803-7232. ISBN 978-80-7043-865-7.
- Rok: 2010
- Pracoviště: Katedra telekomunikační techniky, Katedra radioelektroniky
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Anotace:
In this article we describe our effort to create, model, implement and simulate a quadrature linear digital modulator. It is to be used as a part of advanced radio transmission system. We describe the process of modeling the modulator in Matlab in both floating and fixed point arithmetic for later implementation in VHDL language for FPGA. We also describe the techniques we have used to implement the modulator in digital domain using efficient parallel structure with elimination of multiplication operation. The complete system is then being simulated in ModelSim, compared with the model and results are presented and evaluated.
The Four Wave Mixing Nonlinear Effect
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: RTT 2010 Proceedings. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2010. pp. 115-118. ISBN 978-80-248-2261-7.
- Rok: 2010
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The main purpose of this paper is to present some of the simulation results of the optical nonlinearities of fibers with a focus on the parametric four wave mixing processes. These nonlinear processes offer very interesting properties that may be used possibly in optical signal processing in telecommunication systems but they are also in some respect a limiting factor in the case of DWDM systems. In this paper the simulation result of FWM is presented.
The Optical Burst Switching OMNET++ Simulator Model Extension with The Polarisation Multiplex
- Autoři: Kozák, M., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Knowledge in Telecommunication Technologies and Optics - KTTO 2010. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2010. pp. 36-40. ISBN 978-80-248-2330-0.
- Rok: 2010
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
This paper deals with the simulations of the optical communication systems. The main focus of the simulations is on OMNeT++ simulation environment and the telecommunication fibre optics. The optical burst switching technique is considered and further extended with the polarisation multiplex.
The Soliton Transmission in Optical Fibers
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Advances in Electrical and Electronic Engineering. 2010, 8(5), 107-110. ISSN 1336-1376.
- Rok: 2010
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The objective of this paper is to familiarize readers with the basic analytical propagation model of short optical pulses in optical fiber. Based on this model simulation of propagation of the special type of pulse, called a soliton, will be carried out. A soliton transmission is especially attractive in the fiber optic telecommunication systems as it does not change a pulses shape dutiny propagating right-down the fiber link to the receiver. The model of very short pulse propagation is based on the numerical solution of the nonlinear Schroedinger equation (NLSE), although in some specific cases it is possible tosolve it analytically.
Vybrané aspekty rušení v plně optických přenosových sítích
- Autoři: Kozák, M., Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Access server. 2010, 8.(04), 0003. ISSN 1214-9675.
- Rok: 2010
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Článek se zabývá problematikou plně optických přenosových sítí, využívajících vlnového multiplexu (Wavelength Division Multiplex - WDM). Provádí rozbor vlivů působících na kvalitu přenosu datové informace, porovnává dvě odlišné metody monitorování OSNR podél trasy.
Analysis of EDFA Amplifier Noise Behind the Detector
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: 11th International Conference RTT 2009. Praha: České vysoké učení technické v Praze, 2009. pp. 0162_0009. ISBN 978-80-01-04410-0.
- Rok: 2009
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
The objective of this article is to familiarize the reader with theoretical solution of noise in the EDFA optical amplifiers. Work is focused primarily on spontaneously generated optical noise - ASE and analysis of its impact on the size of noise on the electrical side of a detector. The paper is focused on the impact on the electrical bandwidth - Be and optical bandwidth - Bo on the size of signal noise SNR behind the detector. In today's modern optical systems, where the optical amplifiers are deployed, the contribution of only thermal and quantum noise is not sufficient. The gain of optical amplifiers can significantly improve SNR of the optical line system.
A Short Overview of the Most Actual Problems in the Area of Fiber Bending and Chromatic Dispersion in Photonic Crystal Fibers
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D., doc. Ing. Jiří Vodrážka, Ph.D.,
- Publikace: Proceedings of SPIE - Photonic Crystal Fibers II. Bellingham: SPIE, 2008. pp. 69900X-1-69900X-12. ISSN 0277-786X. ISBN 978-0-8194-7188-8.
- Rok: 2008
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
This paper is oriented to present a short overview of chosen aspects in the area of Photonic Crystal Fibers, primarily nonlinear dispersion properties induced by fiber bending. This topic refers to applications of to microstructure optical components of high-speed transmission systems, such as dispersion compensator based on negative chromatic dispersion resulting from bending the fiber at certain radius.
Advanced Coding for High-speed Radio Link
- Autoři: Bažant, I., doc. Ing. Leoš Boháč, Ph.D., doc. Ing. Jiří Vodrážka, Ph.D.,
- Publikace: Digital Technologies 2008. Žilina: Žilinská universita, Elektrotechnická fakulta, 2008. pp. 1-4. ISBN 978-80-8070-953-2.
- Rok: 2008
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
In modern digital communication and storage system, information theory is becoming increasingly important. The best example of this is the appearance and quick adoption of turbo and block product codes in many practical wireless communication systems.
Design of Photonic Crystal Fibers with Low Bending Losses
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D., doc. Ing. Jiří Vodrážka, Ph.D.,
- Publikace: Proc. SPIE 7138, Photonics, Devices, and Systems IV. Bellingham: SPIE, 2008. p. 713810-1-713810-6. Proceedings of SPIE. vol. 7138. ISSN 0277-786X. ISBN 978-0-8194-7379-0.
- Rok: 2008
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
This paper deals with Photonic Crystal Fibers (PCF) that is not sensitive to bending. On one hand, fiber bending may result in potential negative chromatic dispersion or coupling light from the fundamental mode into the cladding modes, which opens many possibilities to design microstructured optical components for all-optical PCF-based system (e.g. group velocity dispersion compensator) On the other hand, fiber bending is responsible for huge bending losses. The goal of this paper is to reduce bending losses in an operating range of the designed fiber. Reduction of bending losses could be considered in the fiber that would be single-mode for wide range of bending angles or bending radii, but the light is not being coupled into the cladding and the fiber is not sensitive to bending in an office environment.
Pulse Propagation Model of Optical Fibre and Simulation of Optical Soliton Transmission
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: RTT 2008. Bratislava: STU v Bratislave, 2008. ISBN 978-80-227-2939-0.
- Rok: 2008
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Pulse Propagation Model of Optical Fibre and Simulation of Optical Soliton Transmission is presented.
Chosen Aspects of Negative Dispersion Generation in Index Guiding Photonic Crystal Fibers
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D., Ing. Jaroslav Burčík, Ph.D., LL.M.,
- Publikace: Photonic Crystal Fibers. Bellingham: SPIE, 2007. p. 65880W1-65880W10. ISSN 0277-786X. ISBN 978-0-8194-6716-4.
- Rok: 2007
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
This paper deals with the new method of generation of negative waveguide dispersion for dispersion compensation purposes. It is possible to generate negative dispersion by bending waveguide. Only for certain values of bent radius for which cladding mode can appear it is possible to confine the mode and cause optical nonlinearities. Deformation of fundamental modes is possible in the multicore structure.
Comparison of XPM Products using a Self-developed Program
- Autoři: Krčmařík, D., Karásek, M., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Proceedings of the 6th Conference on Telecommunications. Lisboa: Instituto de Telecomunicaçoes - Lisboa, 2007. pp. 509-512. ISBN 978-989-8109-01-9.
- Rok: 2007
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
This document introduces a computer program for investigation of cross-phase modulation (XPM) effects during copropagation of two different pulses along a nonlinear optical fiber. It is also possible to study a simultaneous copropagation of a pulse and a CW signal. Split-step Fourier method is used for solving the Nonlinear Schrodinger equation. Effects of the various parameters of the fiber and the pulses are discussed.
Přehled nejaktuálnějších vědeckých problémů v oblasti disperze u mikrostrukturních vláken
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Jiří Vodrážka, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Optické komunikace 2007. Praha: Agentura Action M, 2007. pp. 71-76. ISBN 978-80-86742-21-2.
- Rok: 2007
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
Přehled nejaktuálnějších vědeckých problémů v oblasti disperze u mikrostrukturních vláken v kontextu současného výzkumu na ČVUT FEL.
Surviving-Channel-Power Transients in Second-Order Pumped Lumped Raman Fiber Amplifier: Experimentation and Modeling
- Autoři: Karásek, M., Kaňka, J., doc. Ing. Leoš Boháč, Ph.D., Krčmařík, D., Radil, J., Vojtěch, J.
- Publikace: IEEE/OSA Journal of Lightwave Technology. 2007, 25(3), 664-672. ISSN 0733-8724.
- Rok: 2007
- Pracoviště: Katedra telekomunikační techniky
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Anotace:
In this paper, the effect of addition and/or dropping of wavelength-division-multiplexed channels in an all- optical gain-clamped (AOGC) second-order (SO) pumped lumped Raman fiber amplifier (LRFA) has been investigated experimentally and analyzed by numerical simulation.
The Sensitivity of Negative Dispersion Induced by Introducing the Curvature into the Index Guiding Photonic Crystal Fiber for Deviation of Geometrical Parameters
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Proceedings of Workshop 2007. Praha: České vysoké učení technické v Praze, 2007. pp. FYZ009. ISBN 978-80-01-03667-9.
- Rok: 2007
- Pracoviště: Katedra telekomunikační techniky
Transmission Analysis of an Optical Arrayed Waveguide Grating Filter - AWG
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: RTT 2007. Žilina: University of Žilina, 2007. pp. 38-42. ISBN 978-80-8070-735-4.
- Rok: 2007
- Pracoviště: Katedra telekomunikační techniky
All-optical Interferometric Switches
- Autoři: Kumpera, A., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Research in Telecommunication Technology 2006 - Proceedings. Brno: Vysoké učení technické v Brně, 2006. pp. 9-13. ISBN 80-214-3243-8.
- Rok: 2006
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
Operation principles and transmission properties of all-optical interferometric switches
Comparison of Dispersion and Loss Parameter of Index Guiding Photonic Crystal Fibers with Hexagonal and Square Lattice
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Proceedings of the Conference TSP 2006. Brno: VUT v Brně, 2006. pp. 51-54. ISBN 80-214-3226-8.
- Rok: 2006
- Pracoviště: Katedra telekomunikační techniky
Flexible Control of Dispersion in Index Guiding Photonic Crystal Fibers Governed by Geometrical Parameters
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Photonic Crystal Materials and Devices III. Bellingham, WA: The International Society for Optical Engineering, 2006. p. 61822F-1-61822F-9. ISSN 0277-786X. ISBN 0-8194-6238-1.
- Rok: 2006
- Pracoviště: Katedra telekomunikační techniky
Important Effects for Supercontinuum Generation
- Autoři: Krčmařík, D., doc. Ing. Leoš Boháč, Ph.D., Karásek, M.
- Publikace: Research in Telecommunication Technology 2006 - Proceedings. Brno: Vysoké učení technické v Brně, 2006. pp. 168-171. ISBN 80-214-3243-8.
- Rok: 2006
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
The paper tries to summarize effects which play a role in a supercontinuum generation
Investigation of Optical Nonlinearities of Highly Nonlinear Photonic Crystal Fibers
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Research in Telecommunication Technology 2006 - Proceedings. Brno: Vysoké učení technické v Brně, 2006. pp. 200-205. ISBN 80-214-3243-8.
- Rok: 2006
- Pracoviště: Katedra telekomunikační techniky
Investigation of the Dependence of a Supercontinuum Bandwidth on Pulse Shape and Fiber Dispersion
- Autoři: Krčmařík, D., doc. Ing. Leoš Boháč, Ph.D., Karásek, M.
- Publikace: Research in Telecommunication Technology 2006 - Proceedings. Brno: Vysoké učení technické v Brně, 2006. pp. 206-210. ISBN 80-214-3243-8.
- Rok: 2006
- Pracoviště: Katedra telekomunikační techniky
Negative Dispersion in Index Guiding Photonic Crystal Fibers
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D., Ing. Jaroslav Burčík, Ph.D., LL.M.,
- Publikace: IWSSIP 2006 and COST 292. Košice: HARLEQUIN s.r.o., 2006. pp. 111-114. ISBN 80-89082-09-2.
- Rok: 2006
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
New method of generation of negative waveguide dispersion for dispersion compensation purposes
Raman Amplifier in an Optical Fiber Line System
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Research in Telecommunication Technology 2006 - Proceedings. Brno: Vysoké učení technické v Brně, 2006. pp. 327-331. ISBN 80-214-3243-8.
- Rok: 2006
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
The use of Raman amplifiers in the optical fiber line systems
Virtuální laboratoř pro výuku přenosu dat
- Autoři: doc. Ing. Leoš Boháč, Ph.D., doc. Ing. Jiří Vodrážka, Ph.D.,
- Publikace: Pedagogický software 2006. České Budějovice: Scientific Pedagogical Publishing, 2006. pp. 555-557. ISBN 80-85645-56-4.
- Rok: 2006
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
Virtuální laboratoř pro výuku přenosu dat
Band Gap Structure as the Photonic Crystal Fiber Guidance Mechanism
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Photonic Crystals and Fibers. Bellingham: SPIE, 2005. pp. 1F-1-1F-8. ISSN 0277-786X. ISBN 0-8194-5957-7.
- Rok: 2005
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
Guidance mechanism in photonic crystal fibers
Internet Remote Teaching in Field of Data Networking
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: RTT 2005 Proceedings. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2005. ISBN 80-248-0897-8.
- Rok: 2005
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
The main objective of this paper is to familiarize the persons concerned with potential forms of theoretical and practical education in field of data networking.
Modern Forms of Education - Perspectives and Visions
- Autoři: prof. Ing. Boris Šimák, CSc., doc. Ing. Jiří Vodrážka, Ph.D., doc. Ing. Leoš Boháč, Ph.D., Ing. Jaromír Hrad, Ph.D., Ing. Tomáš Zeman, Ph.D., Bažant, I., Ing. Robert Bešťák, Ph.D.,
- Publikace: 4th International Conference on Emerging E-learning Technologies and Applications - Conference proceedings. ( Information and Telecommunications Technologies in Education ). Košice: ELFA, 2005. p. 421-424. ISBN 80-8086-016-6.
- Rok: 2005
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
The current stage of modern education forms in technical field with regard to further development
New Type of a Guidance Mechanism in Photonic Crystal Fibers
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Proceedings EC-SIP-M 2005. Bratislava: STU v Bratislave, FEI, 2005. pp. 245-250. ISBN 80-227-2257-X.
- Rok: 2005
- Pracoviště: Katedra telekomunikační techniky
New Type of a Guidance Mechanism in Photonic Crystal Fibers
- Autoři: Ing. Michal Lucki, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: RTT 2005 Proceedings. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2005. ISBN 80-248-0897-8.
- Rok: 2005
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
Setting the band condition in a microstructure is described. The Mode Profile dependent on the band condition is presented. Cross-section patterns presenting the propagation of electromagnetic field are shown. The comparison of a guidance mechanism in various types of PCF's (Index Guiding Photonic Crystal Fibers, Hollow Core Photonic Crystal Fibers, Polarization Maintaining Fibers) is discussed.
Optimalization of 10G Optical Line System
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: RTT 2005 Proceedings. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2005. ISBN 80-248-0897-8.
- Rok: 2005
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
Basic comparison of various optical line configurations used to carry 10 Gbps optical digital signal.
Optical Signal Regeneration - 3R
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: COFAX-TELEKOMUNIKÁCIE 2004 - zborník prednášok. Bratislava: D&D STUDIO, 2004. pp. 239-240. ISBN 80-967019-6-7.
- Rok: 2004
- Pracoviště: Katedra telekomunikační techniky
Optimization of NRZ Data Transmission at 10Gbit/s over G.652 without in-line DFAs
- Autoři: Karásek, M., Radil, J., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Fiber and Integrated Optics. 2004, 23(4), 297-310. ISSN 0146-8030.
- Rok: 2004
- DOI: 10.1080/01468030490460014
- Odkaz: https://doi.org/10.1080/01468030490460014
- Pracoviště: Katedra telekomunikační techniky
-
Anotace:
The article deals with optimization methods of data transmission in NRZ mode at the speed of 10Gbit/s over G.652 without in-line DFAs
Components of DWDM Transport Networks
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: COFAX - Telekomunikácie 2003. Bratislava: D&D STUDIO, 2003. pp. 271-272. ISBN 80-967019-4-0.
- Rok: 2003
- Pracoviště: Katedra telekomunikační techniky
Optimalizace přenosu NRZ dat s rychlostí 10 Gbit/s po vláknech G.652 bez linkových zesilovačů: simulace a experiment
- Autoři: Karásek, M., Radil, J., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Optické komunikace 2003. Praha: Agentura Action, 2003. pp. 77-82. ISBN 80-86742-03-2.
- Rok: 2003
- Pracoviště: Katedra telekomunikační techniky
Using the Raman Scattering for Optical Amplification
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: COFAX - Telekomunikácie 2003. Bratislava: D&D STUDIO, 2003. pp. 269-270. ISBN 80-967019-4-0.
- Rok: 2003
- Pracoviště: Katedra telekomunikační techniky
Páteřní sítě nové generace
- Autoři: doc. Ing. Jiří Vodrážka, Ph.D., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Technologies & Prosperity. 2002, 7(2), 30-36. ISSN 1213-7162.
- Rok: 2002
- Pracoviště: Katedra telekomunikační techniky
Použití EDFA optických zesilovačů v síti CESNET
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: COFAX - Telekomunikácie 2002. Bratislava: D&D STUDIO, 2002. ISBN 80-967019-5-9.
- Rok: 2002
- Pracoviště: Katedra telekomunikační techniky
The Transmission Effectivity and Rate Enhancement of a Cable Media in an Access Network
- Autoři: doc. Ing. Jiří Vodrážka, Ph.D., prof. Ing. Boris Šimák, CSc., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Proceedings of Workshop 2002. Praha: České vysoké učení technické v Praze, 2002. pp. 202-203. ISBN 80-01-02511-X.
- Rok: 2002
- Pracoviště: Katedra telekomunikační techniky
Aplikace MPlambdaS v DWDM sítích
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Telekomunikácie 2001 - Zborník prednášok. Bratislava: ADAPT, 2001. pp. 226-227. ISBN 80-968042-3-5.
- Rok: 2001
- Pracoviště: Katedra telekomunikační techniky
Gigabitová karta sítě Ethernet firmy 3Com
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: LANcom. 2001, XI(10), 44-49. ISSN 1210-2997.
- Rok: 2001
- Pracoviště: Katedra telekomunikační techniky
Simulace systémů DWDM
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Telekomunikácie 2001 - Zborník prednášok. Bratislava: ADAPT, 2001. pp. 224-225. ISBN 80-968042-3-5.
- Rok: 2001
- Pracoviště: Katedra telekomunikační techniky
Využití principu DWDM v optických metropolitních přístupových sítích
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Telekomunikácie 2000. Bratislava: ADAPT, 2000. pp. 260-263. ISBN 80-968042-7-8.
- Rok: 2000
- Pracoviště: Katedra telekomunikační techniky
Zkušenosti s provozem IP telefonie a jeho integrací do současné telekomunikační infrastruktury
- Autoři: doc. Ing. Leoš Boháč, Ph.D., Vozňák, M.
- Publikace: Telekomunikácie 2000. Bratislava: ADAPT, 2000. pp. 149-152. ISBN 80-968042-7-8.
- Rok: 2000
- Pracoviště: Katedra telekomunikační techniky
DIVA LAN ISDN Modem
- Autoři: doc. Ing. Leoš Boháč, Ph.D., Dobšíček, M.
- Publikace: LANcom. 1999, 9(7-8), 58-62. ISSN 1210-2997.
- Rok: 1999
- Pracoviště: Katedra telekomunikační techniky
Optické sítě a jejich využití
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: LANcom. 1999, 9(7-8), 42-48. ISSN 1210-2997.
- Rok: 1999
- Pracoviště: Katedra telekomunikační techniky
Připojení pobočkové lokální sítě LAN do Internetu prostřednictvím ISDN BRI přípojky
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: LANcom. 1999, 9(2), 31-35. ISSN 1210-2997.
- Rok: 1999
- Pracoviště: Katedra telekomunikační techniky
Propojení lokálních počítačových sítí prostřednictvím ISDN
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: LANcom. 1999, 9(3), 36-44. ISSN 1210-2997.
- Rok: 1999
- Pracoviště: Katedra telekomunikační techniky
Microsoft Site Server 3.0
- Autoři: Lagowski, R., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: LANcom. 1998, 8(5), 48-50. ISSN 1210-2997.
- Rok: 1998
- Pracoviště: Katedra telekomunikační techniky
The Common Telecommunication and Transport Problems in Electronic Fee Collection
- Autoři: doc. Ing. Leoš Boháč, Ph.D., Svítek, M.
- Publikace: Konference k 5. výročí založení Fakulty dopravní ČVUT. Praha: České vysoké učení technické v Praze, 1998. pp. 155-157.
- Rok: 1998
- Pracoviště: Katedra telekomunikační techniky
The Common Telecommunication and Transport Problems in Electronic Fee Collection on System Implementation
- Autoři: Svítek, M., doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Sborník mezinárodní konference k 5. výročí zalopžení Fakulty dopravní ČVUT. Praha: České vysoké učení technické v Praze, Fakulta dopravní, 1998, pp. 155-158.
- Rok: 1998
- Pracoviště: Katedra telekomunikační techniky
Kruhové topologie v přenosových synchronních sítích SDH
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Elektro 95. Žilina: VŠDS, 1995. pp. 45-48. ISBN 80-7100-251-8.
- Rok: 1995
- Pracoviště: Katedra telekomunikační techniky
Optické přenosové sítě SDH a jejich topologie
- Autoři: doc. Ing. Leoš Boháč, Ph.D.,
- Publikace: Poster 1995. Praha: České vysoké učení technické v Praze, Fakulta elektrotechnická, 1995, pp. 49.
- Rok: 1995
- Pracoviště: Katedra telekomunikační techniky