Capacity demand for network connections within and between datacenters is increasing relentlessly, fueling the need for deployment of new and improved optical communications equipment. Confronted with the task of developing innovative solutions to address this challenge, engineers must deal with and consolidate countless design choices that are influenced by a large variety of constraints. To name just a few, an optimum solution may depend on technological requirements such as minimum data rate, maximum latency, electrical and optical bandwidth, link distance, upgradability (to higher speeds and/or other/more wavelengths), as well as the need to comply with standards and how these evolve. In this sense, automated design tools for simulating and comparing alternative solutions are indispensable. We present design examples at the system- and component-levels, illustrating the challenges in modeling, analyzing and optimizing technology choices and equipment parameters of optical interconnects for intra- and inter-datacenter applications. Of critical importance for tuning the performance of transceiver components is the integrated co-design of the corresponding electronic and optical parts. We demonstrate a seamless design flow linking simulations of the electronic circuits at the transmitter/receiver (such as serialization/deserialization, DAC/ADC, driver amplifier/TIA, etc.) with simulations of the optical fiber link, enabling investigation and optimization of the overall system performance. Further, we compare advantages and challenges of multimode infrastructure solutions utilizing, for instance, PAM4 modulation of multimode VCSELs with transmission over wide-bandwidth multimode fibers, and single-mode solutions employing Mach-Zehnder modulators with tunable DFB lasers in WDM operation over SMF-links.
We present the benefits and limitations for designing complex optical semiconductor-based integrated structures by means of advanced numerical modeling. Multi-section tunable laser designs are presented in this summary; and their tuning properties are analyzed for different architectures. Other applications and their performance characteristics will be presented in the final paper.
We experimentally characterize wavelength-dependent I/Q imbalances when operating standard C-band IQ-modulator and coherent receiver in S-C-L-band systems. We evaluate their impact on the achievable entropy rate for probabilistically shaped PDM-256/64-QAM and show no penalty up to 150 nm bandwidth based on a single calibration.
This paper addresses the transmission-aware transceiver allocation problem of flexible optical networks for a multi-period planning. The proposed approach aims at assigning the best configuration of bandwidth variable transceivers (BVTRX) considering the amplifier noise and nonlinear channel interferences using the incoherent Extended Gaussian Noise (EGN) model. The proposed solution improves the network throughput and spectrum utilization in the early planning periods and allocates lower number of BV-TRXs in later periods in comparison to algorithms presented recently. A heuristic approach to regenerator placement has also been applied achieving up to 25% transceiver and 50% spectrum utilization savings in comparison to configurations without regenerators.
Next-generation optical communication networks aim to vastly increase capacity by exploiting a larger optical transmission window covering the S-C-L-band. Simultaneously, the clear market trend is to maximize capacity per wavelength to reduce operational costs. This approach requires an increase in spectral efficiency, resulting in stringent requirements on the transceivers, which may not be satisfied in a multi-band (MB) scenario by current commercial components designed for operation in C-band. Transceiver specifications for MB operation can be relaxed through additional digital signal processing (DSP), at the cost of additional complexity, and by more resource-intensive calibration procedures. In this context, we experimentally characterize the wavelength-dependent frequency-resolved in-phase/quadrature (I/Q) imbalance of a standard C-band IQ-modulator and coherent receiver operating in an S-C-L-band system utilizing receiver-side DSP. This operation allows us to understand the nature of the wavelength-dependency of I/Q imbalance in MB systems. In the considered scenario, we validate the effectiveness of a cost-effective strategy for transceiver impairments mitigation and monitoring based on standard wavelength-independent calibration and reduced-complexity DSP.
We demonstrate the effectiveness of digital nonlinear pre-compensation for Raman-amplified transmission of single-carrier 28 Gbaud PM-16QAM. Our simulation results show that by applying transmitter side digital backpropagation and carefully selecting forward and backward Raman pump powers, unrepeated transmission over 300 km can be achieved.
Smart cities will be characterized by a variety of intelligent and networked services, each with specific requirements for the underlying network infrastructure. While smart city architectures and services have been studied extensively, little attention has been paid to the network technology. The KIGLIS research project, consisting of a consortium of companies, universities and research institutions, focuses on artificial intelligence for optimizing fiber-optic networks of a smart city, with a special focus on future mobility applications, such as automated driving. In this paper, we present early results on our process of collecting smart city requirements for communication networks, which will lead towards reference infrastructure and architecture solutions. Finally, we suggest directions in which artificial intelligence will improve smart city networks.
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