Designing adaptive coded modulation for optical networks via achievable information rates

© 2017 IEEE. Achievable information rates are discussed as a tool to analyse and design optical networks. It is shown that the maximum throughput of the network and its dependency of different network parameters can be predicted with such a tool

Physical layer transmitter and routing optimization to maximize the traffic throughput of a nonlinear optical mesh network

This paper investigates the physical layer optimization as a means of improving the utilization of limited network resources. A transparent optical network operating in the nonlinear transmission regime using coherent optical technology is considered. A physical layer model is described that allows the transmission signal quality to be included in the optimization process. Initially a fixed power, route-adapted modulation format approach is taken using integer linear programming to solve the static route allocation problem. It is shown that for the 14-node, 21-link NSF mesh network adaptation of the modulation formats leads to increases in data throughput of 17%. Optimization of the individual transmitter launch powers and spectral channel allocation results in a SNR margin of 2.3 dB, which is used to further increase the overall network traffic throughput exceeding the fixed PM-QPSK modulation format by as much as 50%. Compared to other work this paper highlights that increased gains in network throughput can be achieved if nonlinear interference is included in the routing and spectral assignment algorithm and individual transmitter spectral assignment and launch power is optimized to minimize nonlinear interference

Remote abstraction of an installed dark fiber network using noise to signal ratio

© 2018 OSA. A dark fiber network was partially abstracted utilizing network monitors, prior information and a single probe channel. Validation employed 13×200Gb·s-1 DWDM signals transmitted at the optimum launch power, with measured performance 0.2dB better than abstracted

Single Channel Probe Utilizing the EGN Model to Estimate Link Parameters for Network Abstraction

© 2017 IEEE. We experimentally demonstrate multi-span link parameter abstraction using a single channel 11.5GBd probe. EGN based abstraction gave γ=1.14W 1 km -1 c.f. 0.72W 1 km 1 for a GN based abstraction. The GN model overestimates the abstracted SNR by 0.4dB c.f. the EGN model at 1000km

Estimating coherent optical transmission system performance over heterogeneous fibre span lengths

© 2017 IEEE. This work investigates the estimation accuracy of a coherent optical transmission system's performance when the number of spans in the system is known and the overall system length is approximately known. However, there is no knowledge of the lengths of the individual spans as may happen when institutional knowledge of deployed fibre is lost. Estimating the performance of an optical signal over systems using this fibre may be inaccurate as a result. In this paper, the estimation accuracy of this scenario is examined considering a system with heterogeneous fibre span lengths for a DWDM system transmitting 80 channels modulating polarization multiplexed quadrature phase shift keying (PM-QPSK) at 32 Gbaud across the optical C-band using the Gaussian noise (GN) model in comparison to a reference system with homogenous fibre spans.EU ICONE project grant #60809

Routing, modulation, spectrum and launch power assignment to maximize the traffic throughput of a nonlinear optical mesh network

We investigate the optimization of routing, modulation format adaptation, spectral and launch power assignment as a means of improving the utilization of limited network resources and increasing the network throughput. We consider a transparent optical network operating in the nonlinear transmission regime and using the latest software adapted coherent optical techniques. We separate the problem into one of routing, modulation adaption and channel assignment, followed by channel spectral assignment, and launch power allocation. It is shown, for three test networks, that the launch power allocation and channel spectral assignment can improve the transmission SNR margin over the fixed modulation, fixed power, fully loaded link worst case by approximately 3–4 dB. This increase in SNR margin can be utilized through modulation format adaption to increase the overall network throughput. This paper highlights that increased gains in network throughput can be achieved in nonlinear impaired networks when individual transmitter spectral assignment and launch power are optimized to minimize the nonlinear interference

Throughput Gains From Adaptive Transceivers in Nonlinear Elastic Optical Networks

In this paper, we link the throughput gains, due to transceiver adaptation, in a point-to-point transmission link to the expected gains in a mesh network. We calculate the maximum network throughput for a given topology as we vary the length scale. We show that the expected gain in the network throughput due to transceiver adaptation is equivalent to the gain in a point-to-point link with a length equal to the mean length of the optical paths across the minimum network cut.We also consider upper and lower bounds on the variation of the gain in the network throughput due to transceiver adaptation, where integer-constrained channel bandwidth assignment and quantized adaptations are considered. This bounds the variability of results that can be expected and indicates why some networks can give apparently optimistic or pessimistic results. We confirm the results of previous authors that show finer quantization steps in the adaptive control lead to an increase in the throughput since the mean loss of throughput per transceiver is reduced. Finally, we consider the likely network advantage of digital nonlinear mitigation and show that a significant tradeoff occurs between the increase in the signal-to-noise ratio for larger mitigation bandwidths and the loss of throughput when routing fewer large-bandwidth superchannels.This work was supported by the U.K. Engineering and Physical Sciences Research Council through Program Grant UNLOC [EP/J017582/1] and project INSIGHT [EP/L026155/1]

Adapting Transmitter Power and Modulation Format to Improve Optical Network Performance Utilizing the Gaussian Noise Model of Nonlinear Impairments

This paper serves to highlight the gains in SNR margin and/or data capacity that can be achieved through a proper optimization of the transceiver parameters, for example, launch power, modulation format, and channel allocation. A simple quality of transmission estimator is described that allows a rapid estimation of the signal quality based on ASE noise and nonlinear interference utilizing the Gaussian noise model. The quality of transmission estimator was used to optimize the SNR and maximise the data throughput of transmission signals in a point-to-point link by adjusting the launch power and modulation format. In a three-node network, the launch power and channel allocation were adjusted to minimise the overall effect of nonlinear interference. This paper goes on to show that by optimizing the transceiver modulation format as part of the channel allocation and routing problem gains in network data throughput can be achieved for the 14-node NSF mesh network