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1
Content available Monitoring of phase jitter in fibre optic time and frequency transfer systems
Salwik K., Śliwczyński Ł., Krehlik P.
Metrology and Measurement Systems
|
2018
|
Vol. 25, nr 3
487--497
EN
The phase jitter enables to assess quality of signals transmitted in a bi-directional, long-distance fibre optic link dedicated for dissemination of the time and frequency signals. In the paper, we are considering measurements of jitter using a phase detector the detected frequency signal and the reference signal are supplied to. To cover the wideband jitter spectrum the detected signal frequency is divided and - because of the aliasing process - higher spectral components are shifted down. We are also examining the influence of a residual jitter that occurs in the reference signal generated by filtering the jitter occurring in the same signal, whose phase fluctuations we intend to measure. Then, we are discussing the evaluation results, which were obtained by using the target fibre optic time and frequency transfer system.
2
Content available Testing Time and Frequency Fiber-Optic Link Transfer by Hardware Emulation of Acoustic-Band Optical Noise
Lipiński M., Krehlik P., Śliwczyński Ł., Buczek Ł., Kołodziej J.
Metrology and Measurement Systems
|
2016
|
Vol. 23, nr 2
309--316
EN
The low-frequency optical-signal phase noise induced by mechanical vibration of the base occurs in field-deployed fibers. Typical telecommunication data transfer is insensitive to this type of noise but the phenomenon may influence links dedicated to precise Time and Frequency (T&F) fiber-optic transfer that exploit the idea of stabilization of phase or propagation delay of the link. To measure effectiveness of suppression of acoustic noise in such a link, a dedicated measurement setup is necessary. The setup should enable to introduce a low-frequency phase corruption to the optical signal in a controllable way. In the paper, a concept of a setup in which the mechanically induced acoustic-band optical signal phase corruption is described and its own features and measured parameters are presented. Next, the experimental measurement results of the T&F transfer TFTS-2 system’s immunity as a function of the fibre-optic length vs. the acoustic-band noise are presented. Then, the dependency of the system immunity on the location of a noise source along the link is also pointed out.
3
Content available Badanie nieliniowości w precyzyjnym pomiarze przedziału czasu dla wybranych typów częstościomierzy-czasomierzy
Urban A., Czubla A., Osmyk R., Szterk P., Krehlik P., Śliwczyński Ł.
Zeszyty Naukowe Wydziału Elektrotechniki i Automatyki Politechniki Gdańskiej
|
2014
|
Nr 38
81--84
PL
Celem niniejszego artykułu jest zaprezentowanie metody i wyników badań nad nieliniowością częstościomierzyczasomierzy w pomiarach precyzyjnych przedziałów czasu, prowadzonych w GUM przy współpracy z AGH. Dokonano porównań wyników pomiarów dla częstościomierzy-czasomierzy SR620 i HP 53132A zarówno stałych i zmiennych przedziałów czasu. Potwierdzono przydatność dwukanałowego generatora/dzielnika typu Dual Channel 1/100 PPS Generator oraz komparatora częstotliwości typu A7-MX.
EN
In this paper we present the method and the last results of verification of nonlinearities in time interval measurements with the usage of Time Interval Counters (TIC), performed at Central Office of Measures (GUM) with cooperation of AGH University of Science and Technology. We consider the non-ideal operation of TIC manifested by fluctuations of differences between the current indication of TIC and the real value of the measured time interval. We observed instabilities of indications of TIC, even if the measured time interval is keeping constant. For verification of TIC operation at continuously changed time intervals, it was set up a special measurement system that performs simultaneous measurements of the phasetime changes between two standard frequency signals (with the usage of A7-MX standard frequency comparator) and time intervals between two pulse signals (with the usage of TIC under test). Due to applying a special, developed by AGH, dual channel 1/100 pps generator, the measured 1 pps (1 pulse per second) and 10 MHz signals are standardized and the phasetime between 1 pps and 10 MHz signals are kept in pairs constant. Differences between the indications of TIC and the proper measurement results for frequency allow to verify internal nonlinearities of TIC in time interval measurements. Here, we show and shortly discuss the results obtained for SR620 and 53132A universal counters. The obtained range of fluctuations of indications of SR6200 with relation to the measured time interval approaches about 190 ps, and for 53132A – about 450 ps, whereas the observed short-term noise of measurement for SR620 is about 10 ps, and for 53132A – about 100 ps typically. It was confirmed the complex and random influence of many factors on operation of TIC. Our investigation will be continued with the usage of 100 pps (100 pulses per second) signals and with automatic switching of the measured pulse signals in pairs.
4
Content available Precyzyjny światłowodowy transfer czasu i częstotliwości w relacji GUM-AOS (420 km)
Czubla A., Osmyk R., Szterk P., Śliwczyński Ł., Krehlik P., Buczek Ł., Lipiński M., Nawrocki J., Nogaś P., Lemański D., Dunst P.
Pomiary Automatyka Kontrola
|
2013
|
R. 59, nr 6
518--522
PL
W artykule przedstawiono najnowsze wyniki, prowadzonych w GUM i AOS (Obserwatorium Astrogeodynamiczne CBK PAN) w ścisłej współpracy z AGH, badań nad precyzyjnym transferem czasu i częstotliwości przez włókna światłowodowe w oparciu o uruchomione pomiędzy GUM i AOS operacyjne łącze światłowodowe ze stabilizacją opóźnienia, o łącznej długości optycznej około 420 km. Dokonano kalibracji łącza na poziomie niepewności rozszerzonej 0,25 ns. Uzyskano zgodność wyników z wynikami uzyskanymi z metody GPS CV i GPS PPP. Ponadto potwierdzono poprawność przyjęcia poprawek kalibracyjnych w użytkowanych w GUM i AOS systemach TTS-4 i potwierdzono ogromną przydatność metod światłowodowych do rozwoju i oceny stabilności i dokładności satelitarnych metod transferu czasu i częstotliwości.
EN
In this paper there are presented the newest results of investigation carried on at Central Office of Measures (GUM - Główny Urząd Miar) and Astrogeodynamical Observatory of Space Research Center PAS (AOS) in close cooperation with AGH Technical University (Akademia Górniczo-Hutnicza), in the scope of precise time transfer over optical fibers [1-9]. Since January 2012 the constant operational optical link with stabilization of propagation delay for time and frequency transfer has been run between two UTC(k) time and frequency laboratories: GUM – maintaining UTC(PL), and AOS – maintaining UTC(AOS), over 420 km of optical link [10]. Si-multaneously, there are carried on continuous time transfer with TTS-4 dual-frequency GNSS systems and comparison of measure-ment results obtained from the fiber method and GPS CV or GPS PPP method is possible. It allows to verify calibration results and assess the relative accuracy and stability of the all methods. Calibration of the optical link was performed on the base of local measurements with expanded uncertainty of 0,25 ns, with no need of usage of other time transfer systems or travelling standards or receivers. Calibration results agreed with satellite methods: GPS CV and GPS PPP within the range of about ± 1 ns (Fig. 4, Section 4), which confirms the correctness of adopted calibration method in practice. Simultaneously, this confirms the correctness of adopted calibration corrections in TTS-4 systems used at GUM and AOS for remote time transfer. The obtained results confirmed also the huge useful-ness of our optical method of time and frequency transfer for development and investigation accuracy and stability of satellite methods within this domain (Fig. 5 and 6, Section 4).
5
Content available Precyzyjny światłowodowy transfer czasu i częstotliwości w relacji GUM-AOS (420 km)
Czubla A., Osmyk R., Szterk P., Śliwczyński Ł., Krehlik P., Buczek Ł., Lipiński M., Nawrocki J., Nogaś P., Lemański D., Dunst P.
Metrologia i Probiernictwo : biuletyn Głównego Urzędu Miar
|
2013
|
nr 3
24--25
PL
W artykule przedstawiono najnowsze wyniki, prowadzonych w GUM i AOS oraz w ścisłej współpracy z AGH, badań nad precyzyjnym transferem czasu i częstotliwości przez włókna światłowodowe w oparciu o uruchomione pomiędzy GUM i AOS operacyjne łącze światłowodowe ze stabilizacją opóźnienia, o łącznej długości optycznej ok. 420 km.
6
Content available remote Optimisation of narrowband optical filters for 10 Gbit/s directly modulated laser transmitters
Sliwczynski Ł., Krehlik P., Buczek Ł.
Optica Applicata
|
2010
|
Vol. 40, nr 1
33--47
EN
Filtering of the chirped signal from a directly modulated laser with the narrowband optical filter with a high roll-off allows to in-crease the dispersion tolerance of the transmitter substantially. In the paper, the influence of the parameters of the filter on the performance of the fibre link is analysed. Investigations are carried out for both band-pass and band-stop filters. Basing on the numerical modelling of the fibre link, the parameters of the filter are searched that give the smallest dispersion penalty. Theoretical investigations are supported by hardware experiments confirming correctness of applied methods and models.
7
Światłowodowy transfer sygnałów atomowych wzorców czasu i częstotliwości w Polsce : stan obecny i perspektywy
Lipiński M., Krehlik P., Śliwczyński Ł.
Elektronika : konstrukcje, technologie, zastosowania
|
2010
|
Vol. 51, nr 8
159-162
PL
W artykule omówiono zagadnienie precyzyjnej transmisji sygnałów atomowych wzorców czasu i częstotliwości dla celów dystrybucji i/ lub porównywania. Pokrótce scharakteryzowano stan obecny stosowanych technik transferu satelitarnego, wskazując na ich niewystarczającą dokładność dla potrzeb prowadzenia porównań i tworzenia atomowych skal czasu w najbliższej przyszłości. Zaprezentowano szkicowo prace prowadzone na AGH w dziedzinie wyspecjalizowanych łączy światłowodowych. Ich potencjał aplikacyjny i banery precyzji. Omówiono specyfikę krajowego środowiska laboratoriów tworzących Polską Atomową Skalę Czasu i przedstawiono wstępne koncepcje budowy światłowodowej sieci porównań w aglomeracji stołecznej oraz krajowych i międzynarodowych łączy dalekosiężnych łączących przodujące laboratoria czasu, jako obiecującej perspektywy rozwiązania problemu dokładności prowadzonych porównań w najbliższej przyszłości.
EN
In the paper the problem of the precise atomic time and frequency reference transfer for distribution and/or comparison is discussed. The currently used satellite methods of transfer are described and their parametric limitations for the near future applications shown. The research works carried on the specialized fiber optic links at the AGH University of Technology are mentioned as well as their parametric advantages over the satellite methods are displayed. In the next part the characteristics of domestic lime and frequency enviroment is presented and both the preliminary concept of the metropolitan fiber optic network and the domestic as well as international specialized long-haul links as the solution of the problem of the precise time and frequency transfer in the near future are proposed.
8
Content available remote Precise Measurements of Highly Attenuated Optical Eye Diagrams
Krehlik P., Śliwczyński Ł., Sikorski G.
Advances in Electronics and Telecommunications
|
2010
|
Vol. 1, no. 2
67--69
EN
The idea and practical realization of a measurement system dedicated for highly attenuated eye diagrams diagnostics is presented in the paper. It is specially oriented on high-speed modulated optical data transmission signals which amplification is difficult and/or undesired. The presented measurements displayed the usefulness of proposed solution.
9
Content available remote Bit Error Rate Tester for 10 Gb/s Fibre Optic Link
Śliwczyński Ł., Krehlik P.
Advances in Electronics and Telecommunications
|
2010
|
Vol. 1, no. 2
70--73
EN
The bit error rate tester suitable for operation in 10 Gb/s fibre optic links is described in the paper. The BER tester was built from commercially available components. Generation and reception of 10 Gb/s data stream is performed with help of high-speed serialiser and deserialiser by Maxim. The main functions of the BER tester are implemented in the field programmable gate array (FPGA) Spartan3 device by Xilinx. The part of the FPGA runs with the clock speed equal to 622 MHz. Some measurement results obtained in the fibre optic links operated with 10 Gb/ data rate are also presented.
10
Content available remote Are Carrier Transport Effects Important for Chirp Modeling of Quantum-Well Lasers?
Krehlik P.
Advances in Electronics and Telecommunications
|
2010
|
Vol. 1, no. 2
63--66
EN
The paper investigates the impact of carrier transport effects on the chirp modeling of quantum-well lasers. Particularly, the difference between the full modeling based on quantum-well laser rate equations is compared with modeling based on formulas derived for bulk lasers. As it was shown, the relations between chirp and intensity modulation are quite similar in both cases.
11
Content available remote Improvement in dispersion tolerance of high-speed fiber optic transmission link by optimization of laser modulation
Krehlik P.
Opto-Electronics Review
|
2009
|
Vol. 17, No. 3
225-230
EN
In this paper, the improvement in dispersion tolerance of high-speed transmission link with directly modulated laser is presented. The method is based on adopting the laser modulation (its amplitude and depth) accordingly to the dispersion of actual link. As it is shown, the tolerance of negative dispersion may be doubled and of positive increased even seven times. The simulations are proved by hardware experiment, in which the extended dispersion tolerance is demonstrated.
12
Content available Dwukierunkowa transmisja sygnałów czasu poprzez światłowód
Czubla A., Konopka J., Górnik M., Adamowicz W., Struś J., Romsicki J., Lipiński M., Krehlik P., Śliwczyński Ł., Wolczko A.
Pomiary Automatyka Kontrola
|
2007
|
R. 53, nr 9 bis
289--292
PL
W niniejszym artykule szczegółowo opisano eksperymentalny system do precyzyjnej dwukierunkowej transmisji sygnałów czasu poprzez światłowód oraz przedstawiono najnowsze wyniki pomiarów prowadzonych w tym zakresie przez Główny Urząd Miar, Telekomunikację Polską S. A. i Akademię Górniczo-Hutniczą. Rozważania prowadzone są pod kątem zastosowania w metrologii czasu i częstotliwości.
EN
In this paper an experimental system of two-directional transmission of time signals over optical fibre was described in detail as well as the newest results of measurements performed within this range by GUM, TP S. A. and AGH. These considerations are conducted in context of time and frequency metrology.
13
Content available remote Directly modulated lasers in negative dispersion fiber links
Krehlik P.
Opto-Electronics Review
|
2007
|
Vol. 15, No. 2
71-77
EN
In the paper the impact of frequency chirp of directly modulated lasers is considered in context of high-speed data transmission over negative dispersion fiber. Chirp dispersion induced signal distortions are described, and detailed investigations of their influence on 10 Gbls transmission system performance are presented. The desired laser chirp characteristics and optimal driving conditions are determined. It is also demonstrated that directly modulated laser with low chirp offers similar or even better dispersion tolerance than unchirped (externally modulated) source. Experimental verification of described investigations is presented at the end.
14
Content available remote Directly modulated lasers in chromatic dispersion limited 10 Gb/s links
Krehlik P.
Electronics and Telecommunications Quarterly
|
2007
|
Vol. 53, No 2
177-191
EN
In the paper the usefulness of directly modulated lasers in 10 Gb/s links suffering significant chromatic dispersion is investigated. The influence of laser chirp characteristics on transmission system performance is analysed and optimal laser driving conditions, significantly reducing destructive impact of the chirp, are pointed out. The results of the work are experimentally verified.
15
Content available remote Characterization of semiconductor laser frequency chirp based on signal distortion in dispersive optical fiber
Krehlik P.
Opto-Electronics Review
|
2006
|
Vol. 14, No. 2
123-128
EN
In the paper, the simple method of laser chirp parameters estimation is presented. It is based on measuring time-domain distortions of chirped signal transmitted through dispersive fiber and finding laser chirp parameters by matching measured distortions to calculated ones. Experiments undertaken with 1.55 µm telecommunication grade distributed feedback (DFB) lasers and standard single-mode fiber are described, together with some practical remarks on measurement setup and main conclusions.
16
Content available remote Influence of the laser turn-on delay jitter on BER performance in telecommunication links
Śliwczyński Ł., Krehlik P.
Kwartalnik Elektroniki i Telekomunikacji
|
2006
|
Vol. 52, z. 1
7-22
EN
Paper presents the analysis of sensitivity penalty induced by turn-on delay jitter resulting from subthreshold biasing of directly modulated semiconductor laser. Modelling of the laser turn-on delay used in the analysis assumes that Auger process dominates the recombination of carriers in the subthreshold region. Bit error rate calculation were performed for different modulation speeds and biasing conditions. The change of the received signal mean value was also taken into account. Obtained results show that subthreshold biasing of semiconductor lasers is possible with reasonable sensitivity penalty even for data rates as high as 2.5 Gb/s and that it is generally not a problem for data rates below 622 Mb/s.
PL
Artykuł przedstawia analizę redukcję czułości, spowodowaną przez jitter powstający w bezpośrednio modulowanych laserach półprzewodnikowych, spolaryzowanych wstępnie prądem mniejszym niż prąd progowy. Wykorzystywany w analizie model lasera pozwala wyznaczyć opóźnienie włączenia lasera spolaryzowanego wstępnie poniżej progu w zależności od warunków sterowania. Zakłada on, że rekombinacja nośników przy takiej polaryzacji jest zdominowana przez proces Auger'a. Obliczenia stopy błędów łącza światłowodowego zostały wykonane dla prędkości transmisji w zakresie 155 Mb/s - 2.5 Gb/s oraz dla różnych wartości stosunku prądu wstępnej polaryzacji do prądu progowego lasera. W analizie uwzględniono również zmianę wartości średniej sygnału, spowodowaną dynamicznym zniekształceniem wypełnienia przebiegu przez laser. Rezultaty otrzymane na podstawie przeprowadzonej analizy wskazują, że podprogowa polaryzacja lasera jest możliwa nawet dla prędkości transmisji rzędu 2.5 Gb/s jeśli prąd polaryzacji wstępnej jest utrzymywany w pobliżu połowy prądu progowego lasera. Natomiast dla prędkości transmisji poniżej 622 Mb/s nawet całkowite wygaszanie lasera w trakcie nadawania niskiej wartości sygnału wywołuje jedynie niewielką redukcję czułości rzędu 1.5 dB.
17
Content available remote Novel burst mode laser driver with just-at-threshold bias
Śliwczyński Ł., Krehlik P.
Opto-Electronics Review
|
2004
|
Vol. 12, No. 3
333-337
EN
In the paper, the novel idea of burst mode laser driver with high extinction ratio is presented. The concept is based on controlling the bias current very close to the laser threshold, what is obtained by stabilising the laser power between the data bursts in the range of a few µW. The at-threshold bias eliminates the laser turn on delay, making the driver suitable to transmit the bursts of data without any prebiasing procedure. The experimental driver design is described and measurement results are reported.
18
Content available remote Modelling of dynamic performance of semiconductor lasers under subthreshold biasing
Krehlik P., Śliwczyński Ł.
Opto-Electronics Review
|
2004
|
Vol. 12, No. 2
187-192
EN
The problem of turn-on delay induced by the subthreshold bias of the semiconductor laser in the burst-mode fiber optic transmitters is discussed. An easy to use method of estimation of the turn-on delay is proposed and experimentally verified. The Simulink model of the laser is proposed, allowing to simulate the data pattern distortions in fiber optic communication systems. Presented considerations may be useful for high-speed burst-mode system designers.
19
Content available remote Optimisation of low frequency characteristics of digital optical links
Śliwczyński Ł., Krehlik P.
Opto-Electronics Review
|
2003
|
Vol. 11, No. 1
27-29
EN
In the paper, an analysis of the influence of low frequency characteristics of digital optical links on bit error rate performance is undertaken. Effects caused by both baseline wander flicker noise are investigated. Links with one and two poles in the low frequency range are taken into account. Also some practical conclusions emerging from the analysis are pointed out.
20
Content available remote Four-level signalling in fiber optic transmission of two different bit rates data streams
Krehlik P.
Opto-Electronics Review
|
2002
|
Vol. 10, No. 2
105-109
EN
In the paper an unisochronous four-level signalling is proposed as a method of two different bit rate data multiplexing in standard single mode, intensity modulation fiber optic transmission system. The method is described and its main limitation-some inherent jitter-is pointed out and estimated. After a brief discussion about transmitter (multiplexer) and receiver (demultiplexer) solution, an experimental transmission system is presented. In the system, the 155 Mb/s and 50 Mb/s data streams were successfully multiplexed. Measured systems sensitivity predisposes it to be used in short and medium haullinks.
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