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Receiver implemented RF pilot tone phase noise mitigation in coherent optical nPSK and nQAM systems
KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Optics.
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2011 (English)In: Optics Express, 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.

Place, publisher, year, edition, pages
2011. Vol. 19, no 15, 14487-14494 p.
Keyword [en]
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-37263DOI: 10.1364/OE.19.014487ISI: 000292877600080ScopusID: 2-s2.0-79960520226OAI: diva2:433533
ICT - The Next Generation
QC 20110810Available from: 2011-08-10 Created: 2011-08-08 Last updated: 2012-05-28Bibliographically approved
In thesis
1. DSP based Chromatic Dispersion Equalization and Carrier Phase Estimation in High Speed Coherent Optical Transmission Systems
Open this publication in new window or tab >>DSP based Chromatic Dispersion Equalization and Carrier Phase Estimation in High Speed Coherent Optical Transmission Systems
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.
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 12:06
coherent detection, chromatic dispersion, carrier phase estimation, quadrature phase shift keying
National Category
Research subject
urn:nbn:se:kth:diva-94835 (URN)978-91-7501-346-6 (ISBN)
Public defence
2012-06-08, Sal/Hall C1, ICT-KTH Electrum, Isafjordsgatan 26, Kista, 10:00 (English)
QC 20120528Available from: 2012-05-28 Created: 2012-05-10 Last updated: 2012-05-28Bibliographically approved

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