Optical wireless communication (OWC) is a strong candidate in the sixth generation (6G) of wireless communications as it can support data transmission at high communication speeds, low power consumption, high security, and high reliability. Near-infrared lasers, specifically vertical cavity surface emitting lasers (VCSELs), exhibit larger modulation bandwidth compared to light-emitting diodes (LEDs), and can provide aggregate data rates ranging up to Terabit per second (Tbps). This chapter proposes innovative optical transmitter and receiver designs for indoor laser-based wireless communications, aiming to provide seamless coverage in high-speed multi-user scenarios. The proposed optical transmitter is based on a 5 × 5 VCSEL array where each VCSEL can provide 10 Gigabit per second (Gbps) in a uniform coverage area of 20 cm x 20 cm, achieving a total of 250 Gbps in an area of 1 m2 at 3 m transmission distance. Moreover, two wide-FOV receiver designs that employ photodetector (PD) arrays in along with imaging or non-imaging optics are introduced to support such an ultra-high-speed optical link. The new design of OWC requires potential techniques to address various networking challenges, including cell formation, interference management, resource allocation, and backhauling. To this end, potential solutions for these challenges are discussed to help establish an end-to-end OWC infrastructure for practical deployment.

This article introduces the general concepts of light fidelity (LiFi) 2.0 for sixth generation (6G) of wireless networks that will be based on indoor laser-based wireless networks capable of achieving aggregate data-rates of terabits per second as widely accepted as a 6G key performance indicator. The main focus of this article is on the technologies supporting the near infrared region of the optical spectrum. The main challenges in the design of the transmitter and receiver systems and communication/networking schemes are identified and new insights are provided. This article also covers the previous and recent standards as well as industrial applications for optical wireless communications (OWC) and LiFi.

One of the most important challenges of this century will be to minimise as much as possible the energy consumption of the worldwide digital infrastructure to have a significant contribution on our emissions of CO 2 reduction since energy consumption and emission of CO 2 are directly linked. Therefore, after an introduction (part 1), in part 2 of this paper, we will describe the status of the worldwide production of electricity, the contribution of information and communications technology (ICT) in terms of electricity consumption, and the identification of the critical network segments that can have a significant environmental impact. In part 3, we will focus on the data centres and core services that represent important network segments responsible for the largest emission of CO 2 . In part 4, we will address the access and aggregation part, which represents the second important network segment to optimise. Part 5 will focus on the home networking and enterprise. And before an estimation of the energy savings obtained when adopting the innovations proposed, the impact of the vertical market will be discussed in part 6. Finally, the conclusion (part 7) will summarise the results and perspectives will be proposed to complete the analysis.

We describe key technologies for a greener ICT for the fixed & mobile access, in-building optical backbones including a novel cooling technology, for DC to ensure energy savings and flexibility for different ICT market segments.

In this paper we present a novel approach enabling the switching of native Ethernet frames directly in the optical domain without any buffering. This is possible for the first time in the optical domain thanks to our approach using the known Ethernet frames arrival times, to preconfigure the fast-optical switches to build a new optical path before arrival of the Ethernet packet. The technique is analysed and validated with an Ethernet frame analyser to demonstrate its feasibility.

ZusammenfassungOptical transmission has long been the established choice for nonwireless data transmission spanning distances longer than a few tens of meters, due to its high bandwidth and electromagnetic noise immunity. Most current high-bandwidth networks are essentially a group of fiber-optic links connected by nodes whose function is to forward incoming data to the appropriate output. The input to these nodes is data in optical form, and their output is also data in optical form. Thus, it makes sense to also process the data in the optical domain in order to have simple node architectures that improve reliability, performance, and cost. However, optical node technology cannot yet match the flexibility of electronic technology: The main roadblocks are the lack of random-access optical memories and of optical processors. Industry has addressed this lack by creating two kinds of nodes that achieve opposite extremes in the trade-off between efficiency and complexity: electronic packet switching () nodes and optical circuit switching () nodes.

The WDM slotted Add/Drop Multiplexer (WSADM) technology relies on time slotted WDM rings, where a slot can carry a single WDM packet. All stations can insert and receive these WDM packets. This differs from previous architectures in which packets were carried over a single wavelength, while multiple packets could be carried in a single slot, thus taking advantage differently of the WDM dimension. The WSADM architecture is expected to reduce costs by exploiting low cost technologies. We propose mathematical models for evaluating the performance offered by WSADM optical packet rings, under two different packet insertion policies. In the slot reservation mode, a station can only use the slots that are periodically reserved for its exclusive usage. In the opportunistic insertion mode, a station can use any slot that is neither reserved, nor already occupied. These modes are bench-marked with a channel reservation mode in which each wavelength is dedicated to a single station.

A low-cost WDM slot switching “N-GREEN” network is studied for the Xhaul application. We assess the impact of inter-slot intervals on the jitter in N-GREEN and propose a deterministic scheduler ensuring a zero-jitter performance as needed by CPRI traffic. The scheduling is then implemented in the form of an Integer Linear Program and as a scalable heuristic, and these tools are used for the evaluation of the scheduler performances. The results show important savings and improvements in cost, energy consumption, latency and jitter using N-GREEN w.r.t. state-of-the-art Ethernet Xhaul.

We show that N-GREEN technology is a cost-effective alternative of Ethernet technology. We also demonstrate that WDM slot sharing permits to improve latency and to differentiate Classes of Service with no impact on N-GREEN architecture.

The need for ultra-low latencies in fronthaul/backhaul solutions for the 5G as well as the need for low energy consumption technologies in a cost-effective way push constructors of equipment to propose disruptive approaches for ICT. This paper will then draw the potential of WDM packets in terms of energy consumption and cost gains when compared to classical approaches. The study is completed with an additional analysis showing that this technology has the potential to efficiently reduce the insertion delay of networks.

The optical packet switching technology has been identified as a key technology to offer data rate and modulation format transparency, fine switching granularity and efficient bandwidth utilization. The ANR N-GREEN project proposes a novel over-dimensioned switch/router node with colored optical packet concept. In this work, we propose a new WDM slot sharing approach that significantly improves N-GREEN node-level latency, and show that it is quite effective for Class of Service differentiation in the optical domain.

Further growth of data centers is asking for scalable, low latency and cost efficient interconnection network inside data centers. In this paper, we propose a new packet-optical network called “VERNE”, aiming to satisfy the above requirements by exploiting all-optical and “lossless” operation (by “lossless” we mean operation without packet collisions during their transport from source to destination). The VERNE's network and switching node architecture are detailed for the first time, and the numerical evaluation of the VERNE solution w.r.t. traditional data center architectures is provided. The results suggest that VERNE significantly reduces the number of optical transponders required for data center operation.

WDM has been generally proposed to groom wavelengths for transport applications. This paper will describe our attempt to reduce cost and energy consumption of smart network elements, through an extended use of WDM techniques at the data link level. This paper will draw the advantages of this approach and will demonstrate that this new direction is efficient to keep the frequency processing at a reasonable value in the electronic interfaces, to validate optical bypasses concepts even for long haul applications, to reduce the complexity of ROADM systems and to increase the energy efficiency, through a better exploitation of an integrated optical technology and of the efficient use of the available optical bandwidth. This paper demonstrates that by combining components realized for the data com, or for the NGPON2 systems and a parallelism in the optical domain, it is then possible to decrease dramatically the cost of the systems while offering better performance than classical Ethernet technologies.

The growing energy footprint of communication networks has raised concern about the sustainability of future network development. The GreenTouch consortium was founded to help counter this trend by developing and integrating green network technologies from the access to the core. In order to evaluate these technologies, an end-to-end network power model was developed in the form of the Green Meter, a tool to assess the overall impact and overall energy efficiency benefits of an entire portfolio of solutions. In this paper, we describe the methodology of the Green Meter for the residential fixed access portion, which was extended to include metro aggregation. A baseline architecture for optical access and metro aggregation networks is defined, and is adapted to other scenarios integrating future technologies. The performance is evaluated each time through a mathematical model that captures the energy savings at the component level and has the ability to compute the overall system-level energy savings. We show that energy efficiency can be improved 29-fold over a decade (2010-2020) with businessas- usual trends, and with the added effort of introducing GreenTouch solutions, this could be further improved to achieve a 257-fold increase in energy efficiency. The results confirm that an emphasis on green network design can indeed have a huge impact on reducing the energy consumption of an optical access infrastructure.

This paper describes the benefit of a dynamic optical bypass technology and illustrates some examples of implementation. Techno-economical aspects as well as power consumption estimations are shown.