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| 2. |
- Jacobsen, Gunnar, et al.
(författare)
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Error-rate floors in differential n-level phase-shift-keying coherent receivers employing electronic dispersion equalisation
- 2011
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Ingår i: Journal of optical communications. - 0173-4911 .- 2191-6322. ; 32, s. 191-193
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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. |
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| 4. |
- Jacobsen, Gunnar, et al.
(författare)
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Influence of pre-and post-compensation of chromatic dispersion on equalization enhanced phase noise in coherent multilevel systems
- 2011
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Ingår i: Journal of optical communications. - 0173-4911 .- 2191-6322. ; 32, s. 257-261
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Jacobsen, Gunnar, et al.
(författare)
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New rigorous model for Rx ISI effects in WDM systems
- 2004
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Ingår i: Journal of optical communications. - 0173-4911 .- 2191-6322. ; 25:6, s. 241-45
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Tidskriftsartikel (refereegranskat)abstract
- We present a model for Rx ISI effects using a new and completely general and rigorous dynamic Rx model for-mulation aiming at 10–40 Gbit/s WDM system design applications. The signal shaping part of an electrical fil-ter is modelled in the optical domain using the filter impulse response to modify the signal vector and the covariance matrix. In this way inter-symbol-interference (ISI) effects from any type of electrical filter – specified by the filter impulse response – can be described. The formulation leads to a Hermitian form of the covariance matrix, thus allowing a straightforward analytical formu-lation of the moment generating function (MGF) which in turn specifies the bit-error-ratio (BER). Numerical ex-amples for a 10 Gbit/s pre-amplified Rx shows that the ISI leads to (up to) several dBʼs degradation in sensitivity. Thus it is imperative to account for the Rx ISI effect in rigorous and accurate form in any general WDM trans-mission model.
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| 7. |
- Jacobsen, G., et al.
(författare)
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Phase noise influence in coherent optical DnPSK systems with DSP based dispersion compensation
- 2014
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Ingår i: Journal of optical communications. - : Walter de Gruyter GmbH. - 0173-4911 .- 2191-6322. ; 35:1, s. 57-61
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Tidskriftsartikel (refereegranskat)abstract
- We present a comparative study of the influence of dispersion induced phase noise for n-level PSK systems. From the analysis, we conclude that the phase noise influence for classical homodyne/heterodyne PSK systems is entirely determined by the modulation complexity (expressed in terms of constellation diagram) and the analogue demodulation format. On the other hand, the use of digital signal processing (DSP) in homodyne/intradyne systems renders a fiber length dependence originating from the generation of equalization enhanced phase noise. For future high capacity systems, high constellations must be used in order to lower the symbol rate to practically manageable speeds, and this fact puts severe requirements to the signal and local oscillator (LO) linewidths. Our results for the bit-error-rate (BER) floor caused by the phase noise influence in the case of QPSK, 16PSK and 64PSK systems outline tolerance limitations for the LO performance: 5 MHz linewidth (at 3-dB level) for 100 Gbit/s QPSK; 1 MHz for 400 Gbit/s QPSK; 0.1 MHz for 400 Gbit/s 16PSK and 1 Tbit/s 64PSK systems. This defines design constrains for the phase noise impact in distributed-feed-back (DFB) or distributed-Bragg-reflector (DBR) semiconductor lasers, that would allow moving the system capacity from 100 Gbit/s system capacity to 400 Gbit/s in 3 years (1 Tbit/s in 5 years). It is imperative at the same time to increase the analogue to digital conversion (ADC) speed such that the single quadrature symbol rate goes from today's 25 GS/s to 100 GS/s (using two samples per symbol).
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| 8. |
- Jacobsen, Gunnar, et al.
(författare)
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Phase noise influence in coherent optical OFDM systems with RF pilot tone : Digital IFFT multiplexing and FFT demodulation
- 2012
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Ingår i: Journal of optical communications. - : Walter de Gruyter GmbH. - 0173-4911 .- 2191-6322. ; 33:3, s. 217-226
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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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| 9. |
- Jacobsen, Gunnar, et al.
(författare)
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Phase noise influence in long-range coherent optical OFDM systems with delay detection, IFFT multiplexing and FFT demodulation
- 2012
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Ingår i: Journal of optical communications. - : Walter de Gruyter GmbH. - 0173-4911 .- 2191-6322. ; 33:4, s. 289-295
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Tidskriftsartikel (refereegranskat)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.
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| 10. |
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