Sergei Popov

KTH Royal Institute of Technology, Tukholma, Stockholm, Sweden

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Publications (103)88.15 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Long-haul high speed optical transmission systems are significantly distorted by the interplay between the electronic chromatic dispersion (CD) equalization and the local oscillator (LO) laser phase noise, which leads to an effect of equalization enhanced phase noise (EEPN). The EEPN degrades the performance of optical communication systems severely with the increment of fiber dispersion, LO laser linewidth, symbol rate, and modulation format. In this paper, we present an analytical model for evaluating the performance of bit-error-rate (BER) versus signal-to-noise ratio (SNR) in the n-level phase shift keying (n-PSK) coherent transmission system employing differential carrier phase estimation (CPE), where the influence of EEPN is considered. Theoretical results based on this model have been investigated for the differential quadrature phase shift keying (DQPSK), the differential 8-PSK (D8PSK), and the differential 16-PSK (D16PSK) coherent transmission systems. The influence of EEPN on the BER performance in term of the fiber dispersion, the LO phase noise, the symbol rate, and the modulation format are analyzed in detail. The BER behaviors based on this analytical model achieve a good agreement with previously reported BER floors influenced by EEPN. Further simulations have also been carried out in the differential CPE considering EEPN. The results indicate that this analytical model can give an accurate prediction for the DQPSK system, and a leading-order approximation for the D8PSK and the D16PSK systems.
    Optics Communications 01/2015; 334:222–227. · 1.44 Impact Factor
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    ABSTRACT: Forward error correction (FEC) plays a vital role in coherent optical systems employing multi-level modulation. However, much of coding theory assumes that additive white Gaussian noise (AWGN) is dominant, whereas coherent optical systems have significant phase noise (PN) in addition to AWGN. This changes the error statistics and impacts FEC performance. In this paper, we propose a novel semianalytical method for dimensioning binary Bose-Chaudhuri-Hocquenghem (BCH) codes for systems with PN. Our method involves extracting statistics from pre-FEC bit error rate (BER) simulations. We use these statistics to parameterize a bivariate binomial model that describes the distribution of bit errors. In this way, we relate pre-FEC statistics to post-FEC BER and BCH codes. Our method is applicable to pre-FEC BER around $10^{-3}$ and any post-FEC BER. Using numerical simulations, we evaluate the accuracy of our approach for a target post-FEC BER of $10^{-5}$ . Codes dimensioned with our bivariate binomial model meet the target within 0.2-dB signal-to-noise ratio.
    Journal of Lightwave Technology 11/2014; 32(21). · 2.56 Impact Factor
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    ABSTRACT: We show that by proper code design, phase noise induced cycle slips causing an error floor can be mitigated for 28 Gbaud DQPSK systems. Performance of BCH codes are investigated in terms of required overhead.
    CLEO: Science and Innovations; 06/2014
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    ABSTRACT: We present the compensation of the equalization enhanced phase noise (EEPN) in the long-haul n-level phase shift keying (n-PSK) coherent optical transmission system, by employing a scheme of phase modulated optical pilot carrier.
    Asia Communications and Photonics Conference; 11/2013
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    ABSTRACT: We demonstrate 230-Gbit/s (57.5-Gbaud) polarization-multiplexed QPSK coherent transmission over 820 km field-installed SSMF with quasi real-time DSP, without resorting to ETDM. BER performance well below FEC error-free threshold (2×10^-3) at 2^31-1 PRBS length was achieved.
    Asia Communications and Photonics Conference; 11/2013
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    ABSTRACT: We propose - as a modification of the optical (RF) pilot scheme - a balanced phase modulation between two polarizations of the optical signal in order to generate correlated equalization enhanced phase noise (EEPN) contributions in the two polarizations. The method is applicable for n-level PSK system. The EEPN can be compensated, the carrier phase extracted and the nPSK signal regenerated by complex conjugation and multiplication in the receiver. The method is tested by system simulations in a single channel QPSK system at 56 Gb/s system rate. It is found that the conjugation and multiplication scheme in the Rx can mitigate the EEPN to within ½ orders of magnitude. Results are compared to using the Viterbi-Viterbi algorithm to mitigate the EEPN. The latter method improves the sensitivity more than two orders of magnitude. Important novel insight into the statistical properties of EEPN is identified and discussed in the paper.
    Optics Express 05/2013; 21(10):12351-62. · 3.55 Impact Factor
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    ABSTRACT: We present a comparative study on three carrier phase estimation algorithms, including a one-tap normalized least mean square (NLMS) method, a block-average method, and a Viterbi–Viterbi method in the n-level phase shift keying coherent transmission systems considering the equalization enhanced phase noise (EEPN). In these carrier phase estimation methods, the theoretical bit-error-rate floors based on traditional leading-order Taylor expansion are compared to the practical simulation results, and the tolerable total effective linewidths (involving the transmitter, the local oscillator lasers and the EEPN) for a fixed bit-error-rate floor are evaluated with different block sizes, when the fiber nonlinearities are neglected. The complexity of the three carrier phase estimation methods is also discussed. We find that the carrier phase estimation methods in practical systems should be analyzed based on the simulation results rather than the traditional theoretical predictions, when large EEPN is involved. The one-tap NLMS method can always show an acceptable behavior, while the step size is complicated to optimize. The block-average method is efficient to implement, but it behaves unsatisfactorily when using a large block size. The Viterbi–Viterbi method can show a small improvement compared to the block-average method, while it requires more computational complexity.
    Optics Communications 04/2013; 293:54–60. · 1.44 Impact Factor
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    ABSTRACT: Spherical CdSe-CdS core-shell quantum dots (QDs) are found to be flexible in the transition between the type-I regime and the type-II regime with different core/shell dimensions. The quasi-type-II feature of the colloidal dots is confirmed with time-resolved photoluminescence (PL) measurements. Two recombination paths of the excitons with significantly different decay rates are observed and analyzed. The spherical CdSe-CdS core-shell QDs are numerically simulated to investigate the carrier separation. A relatively long radiative lifetime and high degree of spatial carrier separation provide good potential to achieve lasing under continuous-wave excitation. Amplified spontaneous emission at room temperature is detected from the QDs embedded in the polymer matrix. It is shown that a larger shell thickness results in a lower pumping threshold, while a smaller shell thickness leads to higher PL efficiency.
    Applied Optics 01/2013; 52(1):105-9. · 1.69 Impact Factor
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    ABSTRACT: We present a study of the influence of dispersion induced phase noise for CO-OFDM systems using FFT multiplexing/IFFT demultiplexing techniques (software based). The software based system provides a method for a rigorous evaluation of the phase noise variance caused by Common Phase Error (CPE) and Inter-Carrier Interference (ICI) including - for the first time to our knowledge - in explicit form the effect of equalization enhanced phase noise (EEPN). This, in turns, leads to an analytic BER specification. Numerical results focus on a CO-OFDM system with 10-25 GS/s QPSK channel modulation. A worst case constellation configuration is identified for the phase noise influence and the resulting BER is compared to the BER of a conventional single channel QPSK system with the same capacity as the CO-OFDM implementation. Results are evaluated as a function of transmission distance. For both types of systems, the phase noise variance increases significantly with increasing transmission distance. For a total capacity of 400 (1000) Gbit/s, the transmission distance to have the BER < 10-2 for the worst case CO-OFDM design is less than 800 and 460 km, respectively, whereas for a single channel QPSK system it is less than 1400 and 560 km.
    Journal of Optical Communications 12/2012; 33(4):289-295.
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    IEEE Journal of Quantum Electronics 09/2012; 48(9):1220-1226. · 2.11 Impact Factor
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    ABSTRACT: We present a comparative study of the influence of dispersion induced phase noise for CO-OFDM systems using Tx channel multiplexing and Rx matched filter (analogue hardware based); and digital FFT multiplexing/IFFT demultiplexing techniques (software based). An RF carrier pilot tone is used to mitigate the phase noise influence. From the analysis, it appears that the phase noise influence for the two OFDM implementations is very similar. The software based system provides a method for a rigorous evaluation of the phase noise variance caused by Common Phase Error (CPE) and Inter-Carrier Interference (ICI) and this, in turns, leads to a BER specification. Numerical results focus on a CO-OFDM system with 1 GS/s QPSK channel modulation. Worst case BER results are evaluated and compared to the BER of a QPSK system with the same capacity as the OFDM implementation. Results are evaluated as a function of transmission distance, and for the QPSK system the influence of equalization enhanced phase noise (EEPN) is included. For both types of systems, the phase noise variance increases significantly with increasing transmission distance. An important and novel observation is that the two types of systems have very closely the same BER as a function of transmission distance for the same capacity. For the high capacity QPSK implementation, the increase in BER is due to EEPN, whereas for the OFDM approach it is due to the dispersion caused walk-off of the RF pilot tone relative to the OFDM signal channels. For a total capacity of 400 Gbit/s, the transmission distance to have the BER < 10-4 is less than 277 km. For an RF pilot located in the center of the OFDM band in a CO-OFDM implementation with n-level PSK channel modulation the current results suggest that the walk-off effect is equivalent to the EEPN impact in a single channel n-level PSK system with the same capacity. This observation is important for future design of coherent long-range systems since it shows that there is a free choice between CO-OFDM and a high capacity nPSK implementation at least as long as the phase noise influence is concerned.
    Journal of Optical Communications 09/2012; 33(3):217-226.
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    ABSTRACT: We study polarization-dependent transmission of light through arrays of single-slit split-ring resonator (SSRR) based systems at normal incidence using finite integration time domain (FITD) and finite element methods (FEM). It is found that a conventional planar array of SSRRs acts as an effective optical wave plate at certain polarizations of incident light. The effect is attributed to the intrinsic linear birefringence of individual SSRRs. A comparison is made with other split-ring resonator-based systems exhibiting wave-plate-like properties due to inter-SSRR coupling.
    Optics Letters 06/2012; 37(11):2043-5. · 3.39 Impact Factor
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    ABSTRACT: A radio frequency (RF) carrier can be used to mitigate the phase noise impact in n-level PSK and QAM systems. The systems performance is influenced by the use of an RF pilot carrier to accomplish phase noise compensation through complex multiplication in combination with discrete filters to compensate for the chromatic dispersion (CD). We perform a detailed study comparing two filters for the CD compensation namely the fixed frequency domain equalizer (FDE) filter and the adaptive least-mean-square (LMS) filter. The study provides important novel physical insight into the equalization enhanced phase noise (EEPN) influence on the system bit-error-rate (BER) versus optical signal-to-noise-ratio (OSNR) performance. Important results of the analysis are that the FDE filter position relative to the RF carrier phase noise compensation module provides a possibility for choosing whether the EEPN from the Tx or the LO laser influences the system quality. The LMS filter works very inefficiently when placed prior to the RF phase noise compensation stage of the Rx whereas it works much more efficiently and gives almost the same performance as the FDE filter when placed after the RF phase noise compensation stage.
    Optics Express 04/2012; 20(8):8862-70. · 3.55 Impact Factor
  • 01/2012;
  • Sergey Sergeyev, Sergei Popov
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    ABSTRACT: We report on a theoretical study of polarization impairments in periodically spun fiber Raman amplifiers. Based on the Stochastic Generator approach we have derived averaged equations to calculate polarization dependent gain and mean-square gain fluctuations. We show that periodically spun fiber can work as a Raman polarizer but it suffers from increased polarization dependent gain and gain fluctuations. Unlike this, application of a depolarizer can result in suppression of polarization dependent gain and gain fluctuations. We demonstrate that it is possible to design a new fiber Raman polarizer by combining a short fiber without spin and properly chosen parameters and a long periodically spun fiber. This polarizer provides almost the same polarization pulling for all input signal states of polarization and so has very small polarization dependent gain.
    IEEE Journal of Quantum Electronics 01/2012; 48(1):56-60. · 2.11 Impact Factor
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    ABSTRACT: We present a comparative analysis on three carrier phase extraction approaches, including a one-tap normalized least mean square method, a block-average method, and a Viterbi-Viterbi method, in coherent transmission system considering equalization enhanced phase noise.
    Communications and Photonics Conference (ACP), 2012 Asia; 01/2012
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    ABSTRACT: Gold nanoparticles are mixed in aqueous solution of Rhodamine 6G to modify the lasing output intensity. The photostability deterioration of the gain medium by gold nanoparticles is successfully compensated by silica coating on the nanoparticles.
    Lasers and Electro-Optics (CLEO), 2012 Conference on; 01/2012
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    ABSTRACT: We report the lasing performance and photobleaching of gain material containing a water solution of Rhodamine 6G dye and gold nanoparticles (NPs). In comparison to a pure dye solution, the investigated material demonstrated both enhancement and quenching of the lasing output, depending on the relative concentration of the gold NPs. Although the presence of NPs with an optimized concentration looks preferable in terms of the lasing output enhancement, such additives deteriorate the operational resource of the gain material; i.e., the photobleaching rate speeds up.
    Optics Letters 01/2012; 37(1):34-6. · 3.39 Impact Factor
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    ABSTRACT: The phase noise enhancement due to digital dispersion equalization is investigated, which indicates that the phase noise from transmitter laser can also interact with the dispersion depending on the choice of digital dispersion compensation methods.
    Communications and Photonics Conference (ACP), 2012 Asia; 01/2012
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    ABSTRACT: In this paper we present a comparative study of the equalization enhanced phase noise (EEPN) for pre- and post-compensation of chromatic dispersion in high capacity and high constellation systems. This is to our knowledge the first detailed study in this area for pre-compensation systems. Our main results show that the local oscillator phase noise determines the EEPN influence in post-compensation implementations whereas the transmitter laser determines the EEPN in pre-compensation implementations. As a result of significance for the implementation of practical longer-range systems it is to be emphasized that the use of chromatic dispersion equalization in the optical domain e.g. by the use of dispersion compensation fibers eliminates the EEPN entirely. Thus, this seems an efficient solution for such systems operating at high constellations in the future.
    Journal of Optical Communications 12/2011; 32(4):257-261.

Publication Stats

169 Citations
88.15 Total Impact Points

Institutions

  • 2004–2013
    • KTH Royal Institute of Technology
      • • Department of Microelectronics and Applied Physics (MAP)
      • • Department of Microelectronics and Information Technology
      Tukholma, Stockholm, Sweden
  • 2012
    • Acreo
      Киста, Stockholm, Sweden
  • 2011
    • Aston University
      • School of Engineering and Applied Science
      Birmingham, England, United Kingdom
  • 2010
    • University of Joensuu
      Helsinki, Southern Finland Province, Finland
  • 2008–2010
    • Waterford Institute of Technology
      • Optics Research Group
      Waterford, Munster, Ireland
  • 2005
    • Tampere University of Technology
      • Optoelektroniikan tutkimuskeskus
      Tampere, Western Finland, Finland