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| 2. |
- Czegledi, Cristian Bogdan, 1988, et al.
(författare)
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Modulation Format Independent Joint Polarization and Phase Tracking for Coherent Receivers
- 2016
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Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 13:14, s. 3354-3364
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Tidskriftsartikel (refereegranskat)abstract
- © 1983-2012 IEEE. The state of polarization and the carrier phase drift dynamically during transmission in a random fashion in coherent optical fiber communications. The typical digital signal processing solution to mitigate these impairments consists of two separate blocks that track each phenomenon independently. Such algorithms have been developed without taking into account mathematical models describing the impairments. We study a blind, model-based tracking algorithm to compensate for these impairments. The algorithm dynamically recovers the carrier phase and state of polarization jointly for an arbitrary modulation format. Simulation results show the effectiveness of the proposed algorithm, having a fast convergence rate and an excellent tolerance to phase noise and dynamic drift of the polarization at low complexity, which make the algorithm a strong candidate for future optical systems.
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| 3. |
- Czegledi, Cristian Bogdan, 1988, et al.
(författare)
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Polarization Drift Channel Model for Coherent Fibre-Optic Systems
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 6, s. 21217-
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical framework is introduced to model the dynamical changes of the state of polarization during transmission in coherent fibre-optic systems. The model generalizes the one-dimensional phase noise random walk to higher dimensions, accounting for random polarization drifts, emulating a random walk on the Poincare sphere, which has been successfully verified using experimental data. The model is described in the Jones, Stokes and real four-dimensional formalisms, and the mapping between them is derived. Such a model will be increasingly important in simulating and optimizing future systems, where polarization-multiplexed transmission and sophisticated digital signal processing will be natural parts. The proposed polarization drift model is the first of its kind as prior work either models polarization drift as a deterministic process or focuses on polarization-mode dispersion in systems where the state of polarization does not affect the receiver performance. We expect the model to be useful in a wide-range of photonics applications where stochastic polarization fluctuation is an issue.
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| 4. |
- Czegledi, Cristian Bogdan, 1988, et al.
(författare)
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Temporal stochastic channel model for absolute polarization state and polarization-mode dispersion
- 2017
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Ingår i: 2017 Optical Fiber Communications Conference and Exhibition, OFC 2017 - Proceedings. - 2162-2701. - 9781943580231
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Konferensbidrag (refereegranskat)abstract
- We propose and validate a discrete-time channel model for the temporal drift of the absolute polarization state and polarization-mode dispersion for coherent fiber optic systems. The model can be used in simulations to test and develop DSP for coherent receivers.
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| 5. |
- Eliasson, Henrik, 1985, et al.
(författare)
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Mitigation of nonlinearities using conjugate data repetition
- 2015
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Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 23:3, s. 2392-2402
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Tidskriftsartikel (refereegranskat)abstract
- We investigate a time-domain implementation of generalized phase-conjugated twin waves which we call conjugate data repetition. A theory based on time-domain perturbation analysis explaining the mitigation of nonlinear effects is provided, and the concept is evaluated using numerical simulations. Compared to PM-QPSK at the same channel bit rate, the single-channel transmission reach in a conventional system with standard single-mode fiber of conjugate data repetition-QPSK is increased by approximately a factor of 2.
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| 6. |
- Eriksson, Tobias, 1986, et al.
(författare)
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Achievable Rates Comparison for Phase-Conjugated Twin-Waves and PM-QPSK
- 2016
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Ingår i: 21st OptoElectronics and Communications Conference, OECC 2016 - Held Jointly with 2016 International Conference on Photonics in Switching, PS 2016, Niigata, Japan, 3-7 July 2016. - 9784885523052 ; , s. TuB3-3
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Konferensbidrag (refereegranskat)abstract
- Phase-conjugated twin-waves (PCTW)-QPSK is experimentally compared to PM-QPSK in terms of achievable information rate for bit-wise decoders. For typical long-haul transmission distances, PM-QPSK with soft-decision FEC achieves significantly higher spectral efficiency than PCTW-QPSK.
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| 7. |
- Fehenberger, Tobias, et al.
(författare)
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On the impact of carrier phase estimation on phase correlations in coherent fiber transmission
- 2015
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Ingår i: 2015 Tyrrhenian International Workshop on Digital Communications, TIWDC 2015. - 9781467392600 ; , s. 35-38
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Konferensbidrag (refereegranskat)abstract
- Carrier phase estimation (CPE) is an integral part of the digital signal processing (DSP) of coherent optical communication systems as it compensates laser phase noise (LPN) introduced by free-running transmitter and local oscillating (LO) lasers. Nonlinear interactions during propagation are another source of correlated phase noise. In this paper, we show through simulations and in experiments that blind decision-directed (DD) CPE with regular block lengths removes a large portion of the memory. This makes it virtually impossible in practice to quantify correlations that come from propagation effects, or to obtain rate gains by exploiting the nonlinear phase noise (NLPN). Larger CPE block lengths leave the memory partly intact. This, however, comes at the expense of reduced information rates. We are able to fully recover this rate loss in simulations by using idealized processing of phase distortions. In experiments with full DSP, an almost full rate recovery is reported.
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| 8. |
- Fougstedt, Christoffer, 1990, et al.
(författare)
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Dynamic Equalizer Power Dissipation Optimization
- 2016
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Ingår i: 2016 Optical Fiber Communications Conference and Exhibition. - 9781943580071
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Konferensbidrag (refereegranskat)abstract
- We investigate power dissipation/performance trade-off in a 28nm ASIC implementation of a parallel dynamic equalizer. Over 50% dissipation improvement is possible by sample pruning during filter updates, with only minor tracking-performance reduction.
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| 9. |
- Fougstedt, Christoffer, 1990, et al.
(författare)
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Filter Implementation for Power-Efficient Chromatic Dispersion Compensation
- 2018
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- Chromatic dispersion (CD) compensation in coherent fiber-optic systems represents a very significant DSP block in terms of power dissipation. Since spectrally efficient coherent systems are expected to find a wider deployment in systems shorter than long haul, it becomes relevant to investigate filter implementation aspects of CD compensation in the context of systems with low-to-moderate amounts of accumulated dispersion. The investigation we perform in this paper has an emphasis on implementation aspects such as power dissipation and area usage, it deals with both time-domain and frequency-domain CD compensations, and it considers both A/D-conversion quantization and fixed-point filter design aspects. To enable an accurate analysis on power dissipation and chip area, the evaluated filters are implemented in a 28-nm fully depleted silicon-on-insulator (FD-SOI) process technology. We show that an optimization of the filter response that takes pulse shaping into account can significantly reduce power dissipation and area usage of time-domain implementations, making them a viable alternative to frequency-domain implementations.
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| 10. |
- Fougstedt, Christoffer, 1990, et al.
(författare)
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Power-Efficient Time-Domain Dispersion Compensation Using Optimized FIR Filter Implementation
- 2015
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Ingår i: Signal Processing in Photonics Communications, SPPCom 2015; Boston, MA; United States; 27 June 2015-1 July 2015. - 9781557520005 ; , s. SpT3D.3-
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Konferensbidrag (refereegranskat)abstract
- We investigate fixed-point aspects and time-domain ASIC implementations of CD compensation. An optimized implementation gives significant power dissipation reduction for short links, with further reduction if pulse shaping is considered.
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