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Träfflista för sökning "WFRF:(Xu Jie) ;pers:(Friberg Ari T.)"

Sökning: WFRF:(Xu Jie) > Friberg Ari T.

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1.
  • Jacobsen, Gunnar, et al. (författare)
  • EEPN and CD study for coherent optical nPSK and nQAM systems with RF pilot based phase noise compensation
  • 2012
  • Ingår i: Optics Express. - 1094-4087. ; 20:8, s. 8862-8870
  • Tidskriftsartikel (refereegranskat)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.
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2.
  • Jacobsen, Gunnar, et al. (författare)
  • Error-rate floors in differential n-level phase-shift-keying coherent receivers employing electronic dispersion equalisation
  • 2011
  • Ingår i: Journal of optical communications. - 0173-4911 .- 2191-6322. ; 32, s. 191-193
  • Tidskriftsartikel (refereegranskat)abstract
    • A model for the phase noise influence in differential n-level phase shift keying (nPSK) systems and 2nlevel quadrature amplitude modulated (2nQAM) systems employing electronic dispersion equalization and quadruple carrier phase extraction is presented. The model includes the dispersion equalization enhanced local oscillator phase noise influence. Numerical results for phase noise error-rate floors are given for dual polarization (DQPSK, Dl6PSK and D64PSK) system configurations with basic baud-rate of 25 GS/s. The transmission distance in excess of 1000 km requires local oscillator lasers with sub-MHz linewidth.
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3.
  • Jacobsen, Gunnar, et al. (författare)
  • Phase noise influence in coherent optical OFDM systems with RF pilot tone : Digital IFFT multiplexing and FFT demodulation
  • 2012
  • Ingår i: Journal of optical communications. - : Walter de Gruyter GmbH. - 0173-4911 .- 2191-6322. ; 33:3, s. 217-226
  • Tidskriftsartikel (refereegranskat)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.
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4.
  • Jacobsen, Gunnar, et al. (författare)
  • Phase noise influence in optical OFDM systems employing RF pilot tone for noise cancellation
  • 2011
  • Ingår i: Journal of optical communications. - 0173-4911 .- 2191-6322. ; 32:2
  • Tidskriftsartikel (refereegranskat)abstract
    • For coherent and direct-detection Orthogonal Frequency Division Multiplexed (OFDM) systems employing radio frequency (RF) pilot tone phase noise cancellation the influence of laser phase noise is evaluated. Novel analytical results for the common phase error and for the (modulation dependent) inter carrier interference are evaluated based upon Gaussian statistics for the laser phase noise. In the evaluation it is accounted for that the laser phase noise is filtered in the correlation signal detection. Numerical results are presented for OFDM systems with 4 and 16 PSK modulation, 200 OFDM bins and baud rate of 1 GS/s. It is found that about 225 km transmission is feasible for the coherent 4PSKOFDM system over normal (G.652) fiber.
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5.
  • Jacobsen, Gunnar, et al. (författare)
  • Receiver implemented RF pilot tone phase noise mitigation in coherent optical nPSK and nQAM systems
  • 2011
  • Ingår i: Optics Express. - 1094-4087. ; 19:15, s. 14487-14494
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, a novel method for extracting an RF pilot carrier signal in the coherent receiver is presented. The RF carrier is used to mitigate the phase noise influence in n-level PSK and QAM systems. The performance is compared to the use of an (ideal) optically transmitted RF pilot tone. As expected an electronically generated RF carrier provides less efficient phase noise mitigation than the optical RF. However, the electronically generated RF carrier still improves the phase noise tolerance by about one order of magnitude in bit error rate (BER) compared to using no RF pilot tone. It is also found, as a novel study result, that equalization enhanced phase noise - which appears as correlated pure phase noise, amplitude noise and time jitter - cannot be efficiently mitigated by the use of an (optically or electrically generated) RF pilot tone.
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6.
  • Xu, Tianhua, et al. (författare)
  • Analytical BER performance in differential n-PSK coherent transmission system influenced by equalization enhanced phase noise
  • 2015
  • Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 334, s. 222-227
  • Tidskriftsartikel (refereegranskat)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 rare, 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.
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7.
  • Xu, Tianhua, 1984-, et al. (författare)
  • Analytical estimation of phase noise influence in coherent transmission system with digital dispersion equalization
  • 2011
  • Ingår i: Optics Express. - 1094-4087. ; 19:8, s. 7756-7768
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a novel investigation on the enhancement of phase noise in coherent optical transmission system due to electronic chromatic dispersion compensation. Two types of equalizers, including a time domain fiber dispersion finite impulse response (FD-FIR) filter and a frequency domain blind look-up (BLU) filter are applied to mitigate the chromatic dispersion in a 112-Gbit/s polarization division multiplexed quadrature phase shift keying (PDM-QPSK) transmission system. The bit-error-rate (BER) floor in phase estimation using an optimized one-tap normalized least-mean-square (NLMS) filter, and considering the equalization enhanced phase noise (EEPN) is evaluated analytically including the correlation effects. The numerical simulations are implemented and compared with the performance of differential QPSK demodulation system. (C) 2011 Optical Society of America
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8.
  • Xu, Tianhua, et al. (författare)
  • Carrier phase estimation methods in coherent transmission systems influenced by equalization enhanced phase noise
  • 2013
  • Ingår i: Optics Communications. - : Elsevier BV. - 0030-4018 .- 1873-0310. ; 293, s. 54-60
  • Tidskriftsartikel (refereegranskat)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.
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9.
  • Xu, Tianhua, 1984-, et al. (författare)
  • Chromatic dispersion compensation in coherent transmission system using digital filters
  • 2010
  • Ingår i: Optics Express. - 1094-4087. ; 18:15, s. 16243-16257
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a comparative analysis of three popular digital filters for chromatic dispersion compensation: a time-domain least mean square adaptive filter, a time-domain fiber dispersion finite impulse response filter, and a frequency-domain blind look-up filter. The filters are applied to equalize the chromatic dispersion in a 112-Gbit/s non-return-to-zero polarization division multiplexed quadrature phase shift keying transmission system. The characteristics of these filters are compared by evaluating their applicability for different fiber lengths, their usability for dispersion perturbations, and their computational complexity. In addition, the phase noise tolerance of these filters is also analyzed. (C) 2010 Optical Society of America
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10.
  • Xu, Tianhua, 1984-, et al. (författare)
  • Digital chromatic dispersion compensation in coherent transmission system using a time-domain filter
  • 2010
  • Ingår i: 2010 Asia Communications and Photonics Conference and Exhibition, ACP 2010. - Shanghai. - 9781424471119 ; , s. 132-133
  • Konferensbidrag (refereegranskat)abstract
    • We demonstrate the chromatic dispersion equalization employing a time-domain filter in a 112-Gbit/s polarization division multiplexed quadrature phase shift keying coherent system. The required tap number of the filter is analyzed from anti-aliasing and pulse broadening. The dynamic range of the filter is evaluated by using different number of taps.
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Xu, Tianhua, 1984- (6)
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