| 41. |
- Beygi, Lotfollah, 1977, et al.
(author)
-
Rate-Adaptive Coded Modulation for Fiber-Optic Communications
- 2014
-
In: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 32:2, s. 333-343
-
Journal article (peer-reviewed)abstract
- Rate-adaptive optical transceivers can play an important role in exploiting the available resources in dynamic optical networks, in which different links yield different signal qualities. We study rate-adaptive joint coding and modulation, often called coded modulation (CM), addressing non-dispersion-managed (non-DM) links, exploiting recent advances in channel modeling of these links.We introduce a four-dimensional CM scheme, which shows a better tradeoff between digital signal processing complexity and transparent reach than existing methods. We construct a rate-adaptive CM scheme combining a single low-density parity-check code with a family of three signal constellations and using probabilistic signal shaping. We evaluate the performance of the proposed CM scheme for single-channel transmission through long-haul non-DM fiber-optic systems with electronic chromatic-dispersion compensation. The numerical results demonstrate improvement of spectralefficiency over a wide range of transparent reaches, an improvement over 1 dB compared to existing methods.
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| 42. |
- Beygi, Lotfollah, 1977, et al.
(author)
-
Signal Statistics in Fiber-Optical Channels with Polarization Multiplexing and Self-Phase Modulation
- 2011
-
In: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 29:16, s. 2379 - 2386
-
Journal article (peer-reviewed)abstract
- In this paper, the statistics of received signals in a single-channel dispersion-managed dual-polarization fiber-optical channel are derived in the limit of low dispersion. The joint probability density function (pdf) of the received amplitudes and phases of such a system is derived for both lumped and distributed amplification. The new pdf expressions are used to numerically evaluate the performance of modulation formats over channels with nonlinear phase noise. For example, a sensitivity gain of up to 2 dB is calculated for a specific system using polarization-multiplexed 8-ary phase shift keying compared with a similar single-polarization system at the same spectral efficiency and a symbol error rate of 5*10^(-4). Moreover, the accuracy of the derived pdf is evaluated for some single-channel dispersion-managed fiber-optical links with different dispersion-maps using the split-step Fourier transform method.
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| 43. |
- Beygi, Lotfollah, 1977, et al.
(author)
-
The Limits of Digital Backpropagation in Nonlinear Coherent Fiber-Optical Links
- 2012
-
In: 2012 38th European Conference and Exhibition on Optical Communications, ECOC 2012; Amsterdam; Netherlands; 16 September 2012 through 20 September 2012. - 9781557529503 ; , s. Art. no. 6706029-
-
Conference paper (peer-reviewed)abstract
- The performance of a single-channel fiber-optical link is evaluated with linear (dispersive) and nonlinear equalization. The results show a quadratic growth of the noise variance with input power for a system with nonlinear equalization and also justify the known cubic growth for linear equalization.
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| 44. |
- Bhar, Chayan, 1988, et al.
(author)
-
Channel allocation in elastic optical networks using traveling salesman problem algorithms
- 2019
-
In: Journal of Optical Communications and Networking. - 1943-0620 .- 1943-0639. ; 11:10, s. C58-C66
-
Journal article (peer-reviewed)abstract
- Elastic optical networks have been proposed to support high data rates in metro and core networks. However, frequency allocation of the channels (i.e., channel ordering) in such networks is a challenging problem. This requires arranging the optical channels within the frequency grid with the objective of ensuring a minimum signal-to-noise ratio (SNR). An optimal arrangement results in the highest SNR margin for the entire network. However, determining the optimal arrangement requires an exhaustive search through all possible arrangements (permutations) of the channels. The search space increases exponentially with the number of channels. This discourages an algorithm employing an exhaustive search for the optimal frequency allocation. We utilize the Gaussian noise (GN) model to formulate the frequency allocation (channel ordering) problem as a variant of the traveling salesman problem (TSP) using graph theory. Thereafter, we utilize graph-theoretic tools for the TSP from the existing literature to solve the channel ordering problem. Performance figures obtained for the proposed scheme show that it is marginally inferior to the optimal search (through all possible permutations) and outperforms any random allocation scheme. Moreover, the proposed scheme is implementable for a scenario with a large number of channels. In comparison, an exhaustive search with the GN model and split-step Fourier method simulations are shown to be feasible for a small number of channels only. It is also illustrated that the SNR decreases with an increase in bandwidth when the frequency separation is high.
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| 45. |
- Bjork, G., et al.
(author)
-
Proposed Implementation of "Non-Physical" Four-Dimensional Polarization Rotations
- 2016
-
In: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 34:14, s. 3317-3322
-
Journal article (peer-reviewed)abstract
- Recently one of us proposed a new formalism for modeling electromagnetic wave transformations for coherent communication using a real, four-vector description instead of the conventionally used Jones calculus or the Mueller matrices. The four-vector can then handle all superpositions of two orthogonal polarization basis and two orthogonal time bases (e.g., the in-phase and quadrature phase). In developing this formulation it was found that to provide a general but minimal framework for such rotations, it is natural to divide the six generators of four-dimensional (4d) rotations into two groups of three generators, the right-and the left-isoclinic matrices. Of the six transformations these generators define, it was furthermore found that four of them are readily implemented by linear optical components, while two of then were impossible to implement by such means. In this paper, we detail the reason these two "unphysical" rotations cannot be implemented with linear optics. We also suggest how they can be implemented, but at a cost in the signal-to-noise ratio, and give this minimum cost.
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| 46. |
- Boulanger, B., et al.
(author)
-
Focus issue introduction: nonlinear optics
- 2011
-
In: Optics Express. - 1094-4087 .- 1094-4087. ; 19:23, s. 23561-23566
-
Journal article (peer-reviewed)abstract
- It is now fifty years since the original observation of second harmonic generation ushered in the field of nonlinear optics, close on the heels of the invention of the laser. This feature issue celebrates this anniversary with papers that span the range from new nonlinear optical materials, through the increasingly novel methods that have been developed for phase matching, to emerging areas such as nonlinear metamaterials and plasmonic enhancement of optical properties. It is clear that the next fifty years of nonlinear optics will witness a proliferation of new applications with increasing technological impact.
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| 47. |
- Boyer, Gilbert, et al.
(author)
-
Four-wave mixing of femtosecond pump-probe pulses in optical fibers
- 1999
-
In: Nonlinear Guided Waves and Their Applications.
-
Conference paper (peer-reviewed)abstract
- The nonlinear propagation of a pump-probe pulse pair in an optical fiber has been extensively studied both experimentally, numerically and theoretically. In particular, it has been shown that the probe can attain a spectral shift under the influence of cross-phase modulation (XPM) from the pump, an effect having important applications in e. g. optical switching and demultiplexing.
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| 48. |
- Brajato, Giovanni, et al.
(author)
-
Bayesian filtering framework for noise characterization of frequency combs
- 2020
-
In: Optics Express. - 1094-4087 .- 1094-4087. ; 28:9, s. 13949-13964
-
Journal article (peer-reviewed)abstract
- Amplitude and phase noise correlation matrices are of fundamental importance for studying noise properties of frequency combs. They include information about the origin of noise sources as well as the scaling and correlation of the noise across the comb lines. These matrices provide an insight that is essential for obtaining low-noise performance which is important for, e.g., applications in optical communication, low–noise microwave signal generation, and distance measurements. Estimation of amplitude and phase noise correlation matrices requires highly–accurate measurement technique which can distinguishes between noise sources coming from the frequency comb and the measurement system itself. Bayesian filtering provides a theoretically optimum approach for filtering of measurement noise and thereby, the most accurate measurement of phase and amplitude noise. In this paper, a novel Bayesian filtering based framework for joint estimation of amplitude and phase noise of multiple frequency comb lines is proposed, and demonstrated for phase noise characterization. Compared to the conventional approaches, that do not employ any measurement noise filtering, the proposed approach provides significantly more accurate measurements of correlation matrices, operates over a wide range of signal–to–noise–ratios and gives an insight into comb’s dynamics at short scales (<10−8 s). © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 49. |
- Brentel, Jonas, et al.
(author)
-
Single-wavelength 40 Gb/s soliton field transmission experiments over 400 km fibre without in-line control
- 1999
-
In: OFC/IOOC 1999 - Optical Fiber Communication Conference and the International Conference on Integrated Optics and Optical Fiber Communication. - 155752582X ; 3, s. 121-124
-
Conference paper (peer-reviewed)abstract
- We report single-wavelength 40-Gbit/s soliton transmission over 400-km installed fiber lines in Sweden. Both polarization-division multiplexed and parallel solitons were transmitted. The system performance is dominated by the polarization-mode dispersion.
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| 50. |
- Börjeson, Erik, 1984, et al.
(author)
-
Circuit Implementation of Pilot-Based Dynamic MIMO Equalization for Coupled-Core Fibers
- 2024
-
In: Optical Fiber Communication Conference, OFC 2024. - 9781957171326
-
Conference paper (peer-reviewed)abstract
- We explore ASIC implementation for pilot-based MIMO equalizers for coupled-core transmission, considering chip area scaling trends and performance impact of time-dependent drift. For a system with 28-GBd subcarriers, an equalizer for 8 × 8 is 5.3 times larger than for 2 × 2.
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