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DSP based Chromatic Dispersion Equalization and Carrier Phase Estimation in High Speed Coherent Optical Transmission Systems
KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Coherent detection employing multilevel modulation formats has become one of the most promising technologies for next generation high speed transmission systems due to the high power and spectral efficiencies. Using the powerful digital signal processing (DSP), coherent optical receivers allow the significant equalization of chromatic dispersion (CD), polarization mode dispersion (PMD), phase noise (PN) and nonlinear effects in the electrical domain. Recently, the realizations of these DSP algorithms for mitigating the channel distortions in the coherent transmission systems are the most attractive investigations.

The CD equalization can be performed by the digital filters developed in the time and the frequency domain, which can suppress the fiber dispersion effectively. The PMD compensation is usually performed in the time domain with the adaptive least mean square (LMS) and constant modulus algorithms (CMA) equalization. Feed-forward and feed-back carrier phase estimation (CPE) algorithms are employed to mitigate the phase noise (PN) from the transmitter (TX) and the local oscillator (LO) lasers. The fiber nonlinearities are compensated by using the digital backward propagation methods based on solving the nonlinear Schrödinger (NLS) equation and the Manakov equation.

In this dissertation, we present a comparative analysis of three digital filters for chromatic dispersion compensation, a comparative evaluation of different carrier phase estimation methods considering digital equalization enhanced phase noise (EEPN) and a brief discussion for PMD adaptive equalization. To implement these investigations, a 112-Gbit/s non-return-to-zero polarization division multiplexed quadrature phase shift keying (NRZ-PDM-QPSK) coherent transmission system with post-compensation of dispersion is realized in the VPI simulation platform. In the coherent transmission system, these CD equalizers have been compared by evaluating their applicability for different fiber lengths, their usability for dispersion perturbations and their computational complexity. The carrier phase estimation using the one-tap normalized LMS (NLMS) filter, the differential detection, the block-average (BA) algorithm and the Viterbi-Viterbi (VV) algorithm is evaluated, and the analytical predictions are compared to the numerical simulations. Meanwhile, the phase noise mitigation using the radio frequency (RF) pilot tone is also investigated in a 56-Gbit/s NRZ single polarization QPSK (NRZ-SP-QPSK) coherent transmission system with post-compensation of chromatic dispersion. Besides, a 56-Gbit/s NRZ-SP-QPSK coherent transmission system with CD pre-distortion is also implemented to analyze the influence of equalization enhanced phase noise in more detail.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , 72 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 12:06
Keyword [en]
coherent detection, chromatic dispersion, carrier phase estimation, quadrature phase shift keying
National Category
Telecommunications
Research subject
SRA - ICT
Identifiers
URN: urn:nbn:se:kth:diva-94835ISBN: 978-91-7501-346-6 (print)OAI: oai:DiVA.org:kth-94835DiVA: diva2:526152
Public defence
2012-06-08, Sal/Hall C1, ICT-KTH Electrum, Isafjordsgatan 26, Kista, 10:00 (English)
Opponent
Supervisors
Note
QC 20120528Available from: 2012-05-28 Created: 2012-05-10 Last updated: 2012-05-28Bibliographically approved
List of papers
1. Analytical estimation of phase noise influence in coherent transmission system with digital dispersion equalization
Open this publication in new window or tab >>Analytical estimation of phase noise influence in coherent transmission system with digital dispersion equalization
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2011 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, no 8, 7756-7768 p.Article in journal (Refereed) Published
Abstract [en]

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

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-34201 (URN)10.1364/OE.19.007756 (DOI)000290482500074 ()2-s2.0-79953851378 (Scopus ID)
Note
QC 20110610Available from: 2011-06-10 Created: 2011-05-30 Last updated: 2017-12-11Bibliographically approved
2. Chromatic dispersion compensation in coherent transmission system using digital filters
Open this publication in new window or tab >>Chromatic dispersion compensation in coherent transmission system using digital filters
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2010 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 18, no 15, 16243-16257 p.Article in journal (Refereed) Published
Abstract [en]

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

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-26873 (URN)000280693300106 ()2-s2.0-77954893944 (Scopus ID)
Note
QC 20101130Available from: 2010-11-30 Created: 2010-11-29 Last updated: 2017-12-12Bibliographically approved
3. Normalized LMS digital filter for chromatic dispersion equalization in 112-Gbit/s PDM-QPSK coherent optical transmission system
Open this publication in new window or tab >>Normalized LMS digital filter for chromatic dispersion equalization in 112-Gbit/s PDM-QPSK coherent optical transmission system
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2010 (English)In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 283, no 6, 963-967 p.Article in journal (Refereed) Published
Abstract [en]

High bit rates optical communication systems pose the challenge of their tolerance to linear and nonlinear fiber impairments. Coherent optical receivers using digital signal processing techniques can mitigate the fiber impairments in the optical transmission system, including the chromatic dispersion equalization with digital filters. In this paper, an adaptive finite impulse response filter employing normalized least mean square algorithm is developed for compensating the chromatic dispersion in a 112-Gbit/s polarization division multiplexed quadrature phase shift keying coherent communication system, which is established in the VPI Simulation platform. The principle of the adaptive normalized least mean square algorithm for signal equalization is analyzed theoretically, and at the meanwhile, the taps number and the tap weights in the adaptive finite impulse response filter for compensating a certain fiber chromatic dispersion are also investigated by numerical simulation. The chromatic dispersion compensation performance of the adaptive filter is analyzed by evaluating the behavior of the bit-error-rate versus the optical signal-to-noise ratio, and the compensation results are also compared with other present digital filters.

Keyword
Coherent optical receiver, Digital signal processing, Chromatic, dispersion equalization, Polarization division multiplexed quadrature, phase shift keying, Normalized least mean square algorithm, Adaptive, finite impulse response filter, compensation, receiver
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-19238 (URN)10.1016/j.optcom.2009.11.011 (DOI)000274769900017 ()2-s2.0-74549132513 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
4. Frequency-domain chromatic dispersion equalization using overlap-add methods in coherent optical system
Open this publication in new window or tab >>Frequency-domain chromatic dispersion equalization using overlap-add methods in coherent optical system
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2011 (English)In: Journal of optical communications, ISSN 0173-4911, E-ISSN 2191-6322, Vol. 27, no 2Article in journal (Refereed) Published
Abstract [en]

The frequency domain equalizers (FDEs) employing two types of overlap-add zero-padding (OLA-ZP) methods are applied to compensate the chromatic dispersion in a 112-Gbit/s non-return-to-zero polarization division multiplexed quadrature phase shift keying (NRZ-PDM-QPSK) coherent optical transmission system. Simulation results demonstrate that the OLA-ZP methods can achieve the same acceptable performance as the overlap-save method. The required minimum overlap (or zero-padding) in the FDE is derived, and the optimum fast Fourier transform length to minimize the computational complexity is also analyzed.

 

National Category
Telecommunications Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-35416 (URN)2-s2.0-84859220890 (Scopus ID)
Note
QC 20110629Available from: 2011-06-29 Created: 2011-06-29 Last updated: 2017-12-11Bibliographically approved
5. Receiver implemented RF pilot tone phase noise mitigation in coherent optical nPSK and nQAM systems
Open this publication in new window or tab >>Receiver implemented RF pilot tone phase noise mitigation in coherent optical nPSK and nQAM systems
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2011 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 19, no 15, 14487-14494 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
DISPERSION COMPENSATION, TRANSMISSION-SYSTEM, DIGITAL-FILTERS, EQUALIZATION
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-37263 (URN)10.1364/OE.19.014487 (DOI)000292877600080 ()2-s2.0-79960520226 (Scopus ID)
Funder
ICT - The Next Generation
Note
QC 20110810Available from: 2011-08-10 Created: 2011-08-08 Last updated: 2017-12-08Bibliographically approved
6. EEPN and CD study for coherent optical nPSK and nQAM systems with RF pilot based phase noise compensation
Open this publication in new window or tab >>EEPN and CD study for coherent optical nPSK and nQAM systems with RF pilot based phase noise compensation
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2012 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 8, 8862-8870 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
Carrier phase, Complex multiplication, Discrete filter, Fixed frequency, Least mean squares, Noise compensation, Noise impact, Pilot carrier, Radio frequencies, System quality, Systems performance
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-95258 (URN)10.1364/OE.20.008862 (DOI)000302855500063 ()2-s2.0-84860148490 (Scopus ID)
Note
QC 20120521Available from: 2012-05-21 Created: 2012-05-21 Last updated: 2017-12-07Bibliographically approved
7. Error-rate floors in differential n-level phase-shift-keying coherent receivers employing electronic dispersion equalisation
Open this publication in new window or tab >>Error-rate floors in differential n-level phase-shift-keying coherent receivers employing electronic dispersion equalisation
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2011 (English)In: Journal of optical communications, ISSN 0173-4911, E-ISSN 2191-6322, Vol. 32, 191-193 p.Article in journal (Refereed) Published
Abstract [en]

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.

Keyword
Amplitude modulated; Baud rate; Carrier phase; Coherent receivers; Coherent system; Dual-polarizations; Electronic dispersions; Equalisation; Local oscillators; N-level phase-shift-keying systems; Noise influence; Numerical results; System configurations; Transmission distances, Dispersions; Floors; Phase noise; Phase shift, Phase shift keying
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-95480 (URN)10.1515/JOC.2011.031 (DOI)2-s2.0-80054756993 (Scopus ID)
Note
QC 20120528Available from: 2012-05-28 Created: 2012-05-28 Last updated: 2017-12-07Bibliographically approved
8. Influence of pre-and post-compensation of chromatic dispersion on equalization enhanced phase noise in coherent multilevel systems
Open this publication in new window or tab >>Influence of pre-and post-compensation of chromatic dispersion on equalization enhanced phase noise in coherent multilevel systems
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2011 (English)In: Journal of optical communications, ISSN 0173-4911, E-ISSN 2191-6322, Vol. 32, 257-261 p.Article in journal (Refereed) Published
Abstract [en]

In this paper we present a comparative study of the equalization enhanced phase noise (EEPN) for preand 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 precompensation 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.

Keyword
Comparative studies; Constellation systems; Dispersion-compensation fibers; Equalization enhanced phase noise (EEPN); High capacity; Local oscillators; Multi-level systems; Optical domains; Post-compensation; Pre-compensation; Quadrature phase shifts; Transmitter lasers, Chromatic dispersion; Dispersion compensation; Phase noise; Quadrature phase shift keying, Dispersions
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-95481 (URN)10.1515/JOC.2011.053 (DOI)2-s2.0-84862909225 (Scopus ID)
Note
QC 20120528Available from: 2012-05-28 Created: 2012-05-28 Last updated: 2017-12-07Bibliographically approved
9. Digital compensation of chromatic dispersion in 112-Gbit/s PDM-QPSK system
Open this publication in new window or tab >>Digital compensation of chromatic dispersion in 112-Gbit/s PDM-QPSK system
Show others...
2009 (English)In: 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009, 2009, 5377275- p.Conference paper, Published paper (Refereed)
Abstract [en]

Coherent optical receivers with digital filters can mitigate the impairments in optical transmission system. In this paper, an adaptive filter employing NLMS algorithm is developed for chromatic dispersion compensation in a 112-Gbit/s PDM-QPSK coherent communication system. The performance of the adaptive filter is analyzed by comparing with present digital filters .

Keyword
Coherent communication, Digital compensation, NLMS algorithm, Optical transmission systems, Adaptive algorithms, Adaptive filtering, Adaptive filters, Chromatic dispersion, Communication systems, Electric filters, Quadrature phase shift keying, Light transmission
National Category
Atom and Molecular Physics and Optics Telecommunications
Identifiers
urn:nbn:se:kth:diva-35420 (URN)2-s2.0-77949413923 (Scopus ID)978-155752877-3 (ISBN)
Conference
2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009; Shanghai; China; 2 November 2009 through 6 November 2009
Note

QC 20110629

Available from: 2011-06-29 Created: 2011-06-29 Last updated: 2014-10-14Bibliographically approved
10. Phase noise mitigation in coherent transmission system using a pilot carrier
Open this publication in new window or tab >>Phase noise mitigation in coherent transmission system using a pilot carrier
Show others...
2011 (English)In: Optical Transmission Systems, Subsystems, and Technologies IX / [ed] Xiang Liu, SPIE - International Society for Optical Engineering, 2011Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, we investigate the phase noise elimination employing an optical pilot carrier in the high speed coherent transmission system considering the equalization enhanced phase noise (EEPN). The numerical simulations are performed in a 28-Gsymbol/s quadrature phase shift keying (QPSK) coherent system with a polarization multiplexed pilot carrier. The carrier phase estimation is implemented by the one-tap normalized least mean square (NLMS) filter and the differential phase detection, respectively. Simulation results demonstrate that the application of the optical pilot carrier is very effective for the intrinsic laser phase noise cancellation, while is less efficient for the EEPN mitigation.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2011
Series
SPIE Proceedings, ISSN 0277-786X ; 8309
National Category
Telecommunications Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-82142 (URN)10.1117/12.904038 (DOI)000298882200024 ()2-s2.0-84862946883 (Scopus ID)9780819489579 (ISBN)
Conference
ACP 2011, Shanghai, China, 13-16 November 2011
Note
QC 20120214Available from: 2012-02-11 Created: 2012-02-11 Last updated: 2012-05-28Bibliographically approved

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