| 31. |
- Eriksson, Tobias, 1986, et al.
(author)
-
Experimental Investigation of a Four-Dimensional 256-ary Lattice-based Modulation Format
- 2015
-
In: 2015 Optical Fiber Communications Conference and Exhibition, OFC 2015, Los Angeles, United States, 22-26 March 2015. - 9781557529374
-
Conference paper (peer-reviewed)abstract
- A four-dimensional modulation format with 256 point from the D4-lattice (256-D4) is compared to PM-16QAM in experiments. 256-D4 is more sensitive at high OSNR but with a 21.3% overhead turbo product code, PM-16QAM outperforms 256-D4.
|
|
| 32. |
- Eriksson, Tobias, 1986, et al.
(author)
-
Experimental Investigation of Crosstalk Penalties in Multicore Fiber Transmission Systems
- 2015
-
In: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 7:1
-
Journal article (peer-reviewed)abstract
- We experimentally study the impact of crosstalk in multicore fibers, using polarization-multiplexed quadrature phase-shift keying signals. Using a 7-core fiber, we perform single-span transmission experiments, where the level of crosstalk to the core under test can be varied. We find the penalty in the required optical signal-to-noise ratio (OSNR), compared to a system with no crosstalk, for different signal-to-crosstalk ratios and at different pre-forward-error-correction target bit-error rates (BERs). We show that, for a 1-dB penalty, a 15.7-dB signal-to-crosstalk ratio can be tolerated at BER = 1 x 10(-3). We also perform recirculating loop experiments with varying amount of crosstalk per span to find the impact on the achievable transmission distance.
|
|
| 33. |
- Eriksson, Tobias, 1986, et al.
(author)
-
Four-Dimensional Estimates of Mutual Information in Coherent Optical Communication Experiments
- 2015
-
In: European Conference on Optical Communications (ECOC), Valencia, Spain, 27 September - 1 October 2015. - 9788460817413
-
Conference paper (peer-reviewed)abstract
- Mutual information is experimentally investigated for long-haul coherent transmission. Receivers that consider memoryless four-dimensional noise distributions can achieve significantly higher rates than receivers assuming two-dimensional symmetric distributions.
|
|
| 34. |
- Eriksson, Tobias, 1986, et al.
(author)
-
Impact of 4D Channel Distribution on the Achievable Rates in Coherent Optical Communication Experiments
- 2016
-
In: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 34:9, s. 2256-2266
-
Journal article (peer-reviewed)abstract
- We experimentally investigate mutual information and generalized mutual information for coherent optical transmission systems. The impact of the assumed channel distribution on the achievable rate is investigated for distributions in up to four dimensions. Single channel and wavelength division multiplexing (WDM) transmission over transmission links with and without inline dispersion compensation are studied. We show that for conventional WDM systems without inline dispersion compensation, a circularly symmetric complex Gaussian distribution is a good approximation of the channel. For other channels, such as with inline dispersion compensation, this is no longer true and gains in the achievable information rate are obtained by considering more sophisticated four-dimensional (4D) distributions. We also show that for nonlinear channels, gains in the achievable information rate can also be achieved by estimating the mean values of the received constellation in four dimensions. The highest gain for such channels is seen for a 4D correlated Gaussian distribution.
|
|
| 35. |
- Eriksson, Tobias, 1986, et al.
(author)
-
Multidimensional modulation formats for coherent optical communications
- 2016
-
In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 9774
-
Conference paper (peer-reviewed)abstract
- Coherent optical communication systems applying modulation formats with a dimensionality of four or higherare investigated and compared to systems using conventional formats. Higher dimensionality can be achieved by applying modulation over more than one polarization, time-slot, wavelength, mode or core. Both uncoded systems and systems applying forward-error correction (FEC) coding are studied in terms of spectral efficiency and sensitivity. It is shown that increasing the dimensionality for a constant spectral efficiency improves the sensitivity substantially if no coding is applied, whereas the corresponding gains generally are much smaller in FEC-coded systems.
|
|
| 36. |
- Eriksson, Tobias, 1986, et al.
(author)
-
Single parity check-coded 16QAM over spatial superchannels in multicore fiber transmission
- 2015
-
In: Optics Express. - : The Optical Society. - 1094-4087 .- 1094-4087. ; 23:11, s. 14569-14582
-
Journal article (peer-reviewed)abstract
- We experimentally investigate single-parity check (SPC) coded spatial superchannels based on polarization-multiplexed 16-ary quadrature amplitude modulation (PM-16QAM) for multicore fiber transmission systems, using a 7-core fiber. We investigate SPC over 1, 2, 4, 5 or 7 cores in a back-to-back configuration and compare the sensitivity to uncoded PM-16QAM, showing that at symbol rates of 20 Gbaud and at a bit-error-rate (BER) of 10(-3), the SPC superchannels exhibit sensitivity improvements of 2.7 dB, 2.0 dB, 1.7 dB, 1.3 dB, and 1.1 dB, respectively. We perform both single channel and wavelength division multiplexed (WDM) transmission experiments with 22 GHz channel spacing and 20 Gbaud channel symbol rate for SPC over 1, 3 and 7 cores and compare the results to PM-16QAM with the same spacing and symbol rate. We show that in WDM signals, SPC over hl1 core can achieve more than double the transmission distance compared to PM-16QAM at the cost of 0.91 bit/s/Hz/core in spectral efficiency (SE). When sharing the parity-bit over 7 cores, the loss in SE becomes only 0.13 bit/s/Hz/core while the increase in transmission reach over PM-16QAM is 44 %. (C) 2015 Optical Society of America
|
|
| 37. |
- Fehenberger, Tobias, et al.
(author)
-
Experimental Analysis of Correlations in the Nonlinear Phase Noise in Optical Fiber Systems
- 2016
-
In: ECOC 2016; 42nd European Conference on Optical Communication. ; :W.1.D.4, s. 488-490
-
Conference paper (peer-reviewed)abstract
- A dual-link self-homodyne receiver is used to measure the phase correlations introduced bythe interplay of dispersion and fiber nonlinearities. The dependence of the memory on the WDM setup,signal power and transmission distance is experimentally demonstrated.
|
|
| 38. |
|
|
| 39. |
- Fehenberger, Tobias, et al.
(author)
-
On the impact of carrier phase estimation on phase correlations in coherent fiber transmission
- 2015
-
In: 2015 Tyrrhenian International Workshop on Digital Communications, TIWDC 2015. - 9781467392600 ; , s. 35-38
-
Conference paper (peer-reviewed)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.
|
|
| 40. |
- Foo, Benjamin, 1991, et al.
(author)
-
Analysis of nonlinearity mitigation using phase-sensitive optical parametric amplifiers
- 2019
-
In: Optics Express. - 1094-4087 .- 1094-4087. ; 27:22, s. 31926-31941
-
Journal article (peer-reviewed)abstract
- Phase-sensitive optical parametric amplifiers (PSAs) can provide low-noise optical amplification while simultaneously mitigating nonlinear distortions caused by the Kerr effect. However, nonlinearity mitigation using PSAs is affected by link parameters, and imperfect link design results in residual nonlinear distortions. In this paper, we use first-order perturbation theory to describe these residual nonlinear distortions, and develop a way to mitigate them using a modified third-order Volterra nonlinear equalizer (VNLE) in the receiver. Using numerical simulations, we show that our proposed VNLE reduces the residual nonlinear distortions in links using in-line PSAs for several combinations of symbol rates and modulation formats, and can increase the maximum transmission distance by up to 80%. We also perform a proof-of-concept experiment and confirm that our modified VNLE can mitigate the residual nonlinear distortions on a 10-Gbaud 16QAM signal after transmission through a 10×80-km link with in-line PSAs.
|
|
