| 1. |
- Agrell, Erik, 1965, et al.
(author)
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Roadmap of optical communications
- 2016
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In: Journal of Optics. - : IOP Publishing. - 2040-8978 .- 2040-8986. ; 18:6
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Journal article (peer-reviewed)abstract
- Lightwave communications is a necessity for the information age. Optical links provide enormous bandwidth, and the optical fiber is the only medium that can meet the modern society's needs for transporting massive amounts of data over long distances. Applications range from global high-capacity networks, which constitute the backbone of the internet, to the massively parallel interconnects that provide data connectivity inside datacenters and supercomputers. Optical communications is a diverse and rapidly changing field, where experts in photonics, communications, electronics, and signal processing work side by side to meet the ever-increasing demands for higher capacity, lower cost, and lower energy consumption, while adapting the system design to novel services and technologies. Due to the interdisciplinary nature of this rich research field, Journal of Optics has invited 16 researchers, each a world-leading expert in their respective subfields, to contribute a section to this invited review article, summarizing their views on state-of-the-art and future developments in optical communications.
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| 2. |
- Makki, Behrooz, 1980, et al.
(author)
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On the Performance of Millimeter Wave-based RF-FSO Multi-hop and Mesh Networks
- 2017
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In: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 16:12, s. 7746-7759
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Journal article (peer-reviewed)abstract
- This paper studies the performance of multi-hop and mesh networks composed of millimeter wave-based radio frequency (RF) and free-space optical (FSO) links. The results are obtained in cases with and without hybrid automatic repeat request (HARQ). Using the central limit theorem as well as other state-of-the-art approximation schemes, we derive closed-form expressions for the networks’ outage probability and ergodic achievable rates. We also evaluate the effect of various parameters such as power amplifiers efficiency, number of antennas as well as different coherence times of the RF and the FSO links on the system performance. Finally, we determine the minimum number of the transmit antennas in the RF link such that the same rate is supported in the RF- and the FSO-based hops. The results show the efficiency of the RF-FSO setups in different conditions. Moreover, HARQ can effectively improve the outage probability/energy efficiency, and compensate for the effect of hardware impairments in RF-FSO networks. For common parameter settings of the RF-FSO dual-hop networks, outage probability of 10−4 and code rate of 3 nats-per-channel-use, the implementation of HARQ with a maximum of 2 and 3 retransmissions reduces the required power, compared to cases with open-loop communication, by 13 and 17 dB, respectively.
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| 3. |
- Makki, Behrooz, 1980, et al.
(author)
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Performance analysis of RF-FSO multi-hop networks
- 2017
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In: IEEE Wireless Communications and Networking Conference, WCNC. - 1525-3511. ; , s. Article no 7925522-
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Conference paper (peer-reviewed)abstract
- © 2017 IEEE. We study the performance of multi-hop networks composed of millimeter wave (MMW)-based radio frequency (RF) and free-space optical (FSO) links. The results are obtained in the cases with and without hybrid automatic repeat request (HARQ). Taking the MMW characteristics of the RF links into account, we derive closed-form expressions for the network outage probability. We also evaluate the effect of various parameters such as power amplifiers efficiency, number of antennas as well as different coherence times of the RF and the FSO links on the system performance. Finally, we present mappings between the performance of RF- FSO multi-hop networks and the ones using only the RF- or the FSO-based communication, in the sense that with appropriate parameter settings the same outage probability is achieved in these setups. The results show the efficiency of the RF-FSO setups in different conditions. Moreover, the HARQ can effectively improve the outage probability/energy efficiency, and compensate the effect of hardware impairments in RF-FSO networks. For common parameter settings of the RF-FSO dual- hop networks, outage probability 10^{-4} and code rate 3 nats-per-channel-use, the implementation of HARQ with a maximum of 2 and 3 retransmissions reduces the required power, compared to the cases with no HARQ, by 13 and 17 dB, respectively.
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| 4. |
- Xu, Yuxin, et al.
(author)
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Cross-layer static resource provisioning for dynamic traffic in flexible grid optical networks
- 2021
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In: Journal of Optical Communications and Networking. - 1943-0620 .- 1943-0639. ; 13:3, s. 1-13
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Journal article (peer-reviewed)abstract
- Flexible grid networks need rigorous resource planning to avoid network over-dimensioning and resource over-provisioning. The network must provision the hardware and spectrum resources statically, even for dynamic random bandwidth demands, due to the infrastructure of flexible grid networks, hardware limitations, and reconfiguration speed of the control plane. We propose a flexible online–offline probabilistic (FOOP) algorithm for the static spectrum assignment of random bandwidth demands. The FOOP algorithm considers the probabilistic nature of random bandwidth demands and balances hardware and control plane pressures with spectrum assignment efficiency. The FOOP algorithm uses the probabilistic spectrum Gaussian noise (PSGN) model to estimate the physical-layer impairment (PLI) for random bandwidth traffic. Compared to a benchmark spectrum assignment algorithm and a widely applied PLI estimation model, the proposed FOOP algorithm using the PSGN model saves up to 49% of network resources.
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| 5. |
- Xu, Yuxin, et al.
(author)
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Iterative Resource Allocation Algorithm for EONs Based on a Linearized GN Model
- 2019
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In: Journal of Optical Communications and Networking. - 1943-0620 .- 1943-0639. ; 11:3, s. 39-51
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Journal article (peer-reviewed)abstract
- Elastic optical networks (EONs) rely on efficient resource planning to meet future communication needs and avoid resource overprovisioning. Estimation of physical-layer impairments (PLIs) in EONs plays an important role in the network planning stage. Traditionally, the transmission reach (TR) and Gaussian noise (GN) models have been broadly employed in the estimation of the PLIs. However, the TR model cannot accurately estimate PLIs, whereas the GN model is incompatible with state of the art linear optimization solvers. In this paper, we propose a physical-layer estimation model based on the GN model, referred to as the conservative linearized Gaussian noise (CLGN) model. To address the routing, spectrum, and regeneration assignment problem accounting for PLIs, we introduce a link-based mixed integer linear programming formulation employing the CLGN, whose heavy computational burden is relieved by a heuristic approach referred to as the sequential iterative optimization algorithm. We show through simulation that network resources such as spectrum and regeneration nodes can be saved utilizing the CLGN model rather than the TR model. Our proposed heuristic algorithm speeds up the optimization process and provides better resource usage compared to state of the art algorithms on benchmark networks.
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| 6. |
- Xu, Yuxin, et al.
(author)
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Physical-layer impairments estimation for random bandwidth traffic
- 2024
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In: Journal of Optical Communications and Networking. - 1943-0620 .- 1943-0639. ; 16:2, s. 104-111
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Journal article (peer-reviewed)abstract
- Traffic demands in future elastic optical networks are expected to be heterogeneous with time-varying bandwidth. Estimating the physical-layer impairments (PLIs) for random bandwidth demands is important for cross-layer network resource provisioning. State-of-the-art PLI estimation techniques yield conservative PLI estimates using the maximum bandwidth, which leads to significant over-provisioning. This paper uses probabilistic information on random bandwidth demands to provide a computationally efficient, accurate, and flexible PLI estimate. The proposed model is consistent with the needs of future self-configuring fiber-optic networks and maximally avoids up to a 25% overestimation of PLIs compared to the benchmark for the cases studied, thus reducing the network design margin at a negligible extra computational cost.
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| 7. |
- Xu, Yuxin, et al.
(author)
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Probabilistic spectrum Gaussian noise estimate for random bandwidth traffic
- 2019
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In: IET Conference Publications. - : Institution of Engineering and Technology. ; 2019
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Conference paper (peer-reviewed)abstract
- A probabilistic spectrum Gaussian noise (PSGN) model is proposed to predict the nonlinear noise for random bandwidth traffic in long-haul elastic optical networks. The model reduces the noise estimate 9.1% on average compared to the standard Gaussian noise model applied to the maximum bandwidth.
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| 8. |
- Xu, Yuxin, et al.
(author)
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Static resource allocation for dynamic traffic
- 2019
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In: IET Conference Publications. - : Institution of Engineering and Technology. - 9781839530074 ; 2019
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Conference paper (peer-reviewed)abstract
- A flexible offline probabilistic (FOP) algorithm is designed to aggressively accommodate random bandwidth traffic demands in long-haul networks. Compared to algorithms that configure demands according to their maximum bandwidth, the FOP algorithm can save 15% of the spectrum used, accommodating over 99% of the throughput demand.
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| 9. |
- Yan, Li, 1988, et al.
(author)
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Link-Level Resource Allocation for Flexible-Grid Nonlinear Fiber-Optic Communication Systems
- 2015
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In: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 27:12, s. 1250-1253
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Journal article (peer-reviewed)abstract
- Resource allocation for transport optical networks has traditionally used a transmission reach constraint to estimate physical impairments. For flexible-grid networks, nonlinear impairments are not sufficiently well characterized by the transmission reach since various modulations and bandwidths can coexist on the same link. We propose a resource allocation algorithm for a single flexible-grid fiber link based on a nonlinear signal distortion model, as a first step towards whole-network design. An optimization problem is formulated to provide a close-to-optimal resource allocation that guarantees the quality of transmission for every channel. Compared with a simpler algorithm based on transmission reach, our proposed algorithm shows the potential of bandwidth savings. It is demonstrated to be insensitive to channel ordering.
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| 10. |
- Yan, Li, 1988, et al.
(author)
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Regenerator Allocation in Nonlinear Elastic Optical Networks With Random Data Rates
- 2018
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In: 2018 Optical Fiber Communications Conference and Exposition, OFC 2018 - Proceedings. - 9781943580385
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Conference paper (peer-reviewed)abstract
- We optimize the regenerator allocation in nonlinear elastic networks whose traffic demands have random data rates. Compared with previous regenerator allocation algorithms, our method achieves the same blocking probability with 11% fewer regenerator sites.
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