Wyniki wyszukiwania - Biblioteka Nauki

1

Analysis of baseline wander and BER performance in transmission links with low - frequency removal

100%

Śliwczyński Ł.

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tom Vol. 52, z. 3

309-322

EN

The paper presents the study of the statistical properties of baseline wander appearing when transmitting digital data through transmission links with low frequency removal. The model of the links is considered where received signal is compared with the threshold obtained by low-pass filtering the non-return to zero digital data signal. Probability density of the signal at the output of different order low-pass is investigated. Beta distribution is proposed as the approximation of true probability density function of such signal. Next, the BER performance of transmission link with baseline wander and additive Gaussian noise is analysed. Some practical remarks concerning the localisation of the low frequency poles are also given.

PL

Artykuł dotyczy analizy zjawiska błądzenia progu komparacji występującego w cyfrowych łączach transmisyjnych z odciętą składową stałą. W przedstawionym modelu zastępczym łącza w zakresie małych częstotliwości odbierany sygnał NRZ jest porównywany z progiem komparacji, otrzymywanym poprzez dolnoprzepustową filtrację sygnału danych. Transmitancja filtru na wyjściu którego otrzymujemy próg komparacji uwzględnia ograniczenia dolnopasmowe, wnoszone do łącza przez układy nadajnika oraz wzmacniacza odbiorczego. Na podstawie przeprowadzonych rozważań teoretycznych zaproponowano aproksymację funkcji gęstości prawdopodobieństwa sygnału na wyjściu filtru w postaci rozkładu beta. Poprawność zaproponowanego rozkładu sprawdzono w przypadku transmitancji 1 rzędu przy użyciu metody odwzorowania zwężającego. W przypadku łączy o transmitancji II i III rzędu celem sprawdzenia poprawności aproksymacji posłużono się metodami Monte Carlo ( w wersji standardowej oraz importance sampling). Następnie, wykorzystując zaproponowaną aproksymację dokonano analizy wpływu fluktuacji progu komparacji na bitową stopę błędów oraz wyznaczono redukcję czułości łącza transmisyjnego. Na zakończenie zostały podane praktyczne uwagi odnośnie sposobu doboru stałych czasowych związanych z ograniczeniami dolnopasmowymi w łączu transmisyjnym.

2

Compensation of the dynamic error in burst-mode fibre optic receivers based on preamble filtering

100%

Śliwczyński Ł.

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tom No 54

189-196

EN

In the paper the extension of the idea of the threshold generation circuitry based on preamble filtering, and dedicated for fibre-optic packet receivers, is presented. In such a circuit, during the phase of sweeping the time constant of the controlled filter some error arises. During further filter operation, this error diminishes, but the time necessary for this is quite long comparing to the bit period. This error is responsible for pulse width distortions of received bits and degrades bit error rate of the link. It is shown that this error may be compensated in the rceeiver what is proved by experimental data.

3

Analysis of operation of fast peak detectors in burst-mode fibre optic receivers

100%

Śliwczyński Ł.

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tom No 54

181-188

EN

In the paper, the analysis of operation of fast peak detectors is presented. It is assumed that the signal driving the detector is composed of short pulses with amplitude in the order of a few mV. Such detectors are used in the fibre optic burst-mode networks, where digital data is conveyed in the form of packets, which differ in amplitude substantially. Peak detectors are used there to determine proper threshold voltage that is necessary to perform data detection in each packet. The paper is focused mostly on the effects occurring in the peak detectors with transconductance amplifier in the feedback loop, resulting from amplifier bandwidth limitation and presence of stray capacitances.

4

Discussion of optimal decision rules in case of noise corrupted threshold

100%

Śliwczyński Ł.

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tom T. 1, z. 3

128-137

EN

In the paper some optimal decision rules of data reception for binary digital transmission systems and channel with additive noise (i.e. maximum a posteriori, maximum likelihood and minimum average error) are briefly reviewed in the case of noiseless threshold. Next the optimal decision rules are derived under the assumption that the threshold level is corrupted by noise, which may originate during the process of threshold extraction. The influence of this noise to the optimal threshold setting is examined and finally some illustrative examples are given.

PL

W artykule dokonano krótkiego przeglądu wybranych, optymalnych progowych reguł decyzyjnych dla cyfrowej transmisji binarnej w kanale z addytywnym szumem. Następnie wyprowadzono warunki optymalności dla przypadku, gdy dodatkowo wartość progowa jest zakłócona szumem, który może powstawać w układzie odzyskującym wartość progową z sygnału. Przeprowadzono dyskusję otrzymanych rezultatów a wyniki zilustrowano przykładami, które obrazują wpływ zaszumienia progu na optymalne odtwarzanie sygnału w odbiorniku.

5

Resolving group delay of narrowband optical filters from their transmission characteristics

100%

Śliwczyński Ł.

Opto-Electronics Review

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2009

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tom Vol. 17, No. 4

318-324

EN

In the paper, the factors affecting the accuracy of calculating the optical filter group delay basing on the measured power transmission characteristic are analyzed. Having the phase characteristic of the filter recovered from its transmission, the group delay is usually calculated via differentiation. The new, direct formula is proposed giving more accurate results when the characteristic of the filter is available in the limited frequency range. Also the limitations arising from the noise of the optical spectrum analyzer are examined.

6

Optimisation of low frequency characteristics of digital optical links

63%

Śliwczyński Ł. , Krehlik P.

Opto-Electronics Review

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2003

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tom 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.

7

Novel burst mode laser driver with just-at-threshold bias

63%

Śliwczyński Ł. , Krehlik P.

Opto-Electronics Review

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2004

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tom 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.

8

Modelling of dynamic performance of semiconductor lasers under subthreshold biasing

63%

Krehlik P. , Śliwczyński Ł.

Opto-Electronics Review

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2004

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tom 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.

9

High-speed DC optical receiver for measurement applications

63%

Śliwczyński Ł. , Krehlik P.

Opto-Electronics Review

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1998

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tom Vol. 6, No. 4

269-272

EN

In the paper a concept and theoretical analysis of feedforward compensated transimpedance amplifier for amplifying a signal from photodiode is presented. The main feature of feedforward structure used is very wide bandwidth, allowing amplification of not only AC component of incoming optical signal but DC component as well. Experimental results for the amplifier built with ERA5 MIMIC are also presented, confirming practical usefulness of the proposed solution. Application of the amplifier may include measurements in any optical high-speed network exploiting burst-mode transmission (e. g., PON, ATM).

10

Performance analysis of CW laser driving circuits

51%

Śliwczyński Ł. , Lipiński M. , Krehlik P. , Wolczko A.

Opto-Electronics Review

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1998

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tom Vol. 6, No. 2

131-139

EN

In the paper the most popular structures of the semiconductor laser drives are presented: driver with the mean-value loop and driver with the wideband loop. Both DC and AC performance are analysed and dependence of the output optical power on different circuit parameters is shown. Some remarks on the laser safety in the considered driver structures are also made. The inherent low frequency (LF) limitation of the mean-value loop, its dependence on the open loop gain and particular circuit structure are examined. The effects resulting from the LF cut-off shown along with their impact on the driver dynamic performance. Good high frequency (HF) performance of the mean-value loop is pointed out. Analysis of the wideband loop is also carried out and especially the difficulties in practical realisation are considered. The need of trade-off between good DC and AC performance is shown. The particular case of the maximally flat frequency response shaping is recommended as being a reasonable choice for both frequency and pulse performance and some practical formulas are given. The lack of LF cut-off and relatively poor HF performance in the wideband loop driver are pointed out. As the final conclusion a general performance comparison between mean-value loop and wideband loop driver structures is carried out.

11

Monitoring of phase jitter in fibre optic time and frequency transfer systems

51%

Salwik K. , Śliwczyński Ł. , Krehlik P.

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tom 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.

12

Testing Time and Frequency Fiber-Optic Link Transfer by Hardware Emulation of Acoustic-Band Optical Noise

45%

Lipiński M. , Krehlik P. , Śliwczyński Ł. , Buczek Ł. , Kołodziej J.

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tom 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.

13

Dwukierunkowa transmisja sygnałów czasu poprzez światłowód

32%

Czubla A. , Konopka J. , Górnik M. , Adamowicz W. , Struś J. , Romsicki J. , Lipiński M. , Krehlik P. , Śliwczyński Ł. , Wolczko A.

Pomiary Automatyka Kontrola

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2007

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tom 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.

14

Precyzyjny światłowodowy transfer czasu i częstotliwości w relacji GUM-AOS (420 km)

26%

Czubla A. , Osmyk R. , Szterk P. , Śliwczyński Ł. , Krehlik P. , Buczek Ł. , Lipiński M. , Nawrocki J. , Nogaś P. , Lemański D. , Dunst P.

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2013

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tom 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.

15

Precyzyjny światłowodowy transfer czasu i częstotliwości w relacji GUM-AOS (420 km)

26%

Czubla A. , Osmyk R. , Szterk P. , Śliwczyński Ł. , Krehlik P. , Buczek Ł. , Lipiński M. , Nawrocki J. , Nogaś P. , Lemański D. , Dunst P.

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tom 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).