Andrew Lord

Next generation sliceable bandwidth variable transponders

This article reports the work on next generation transponders for optical networks carried out within the last few years. A general architecture supporting super-channels (i.e., optical connections composed of several adjacent subcarriers) and sliceability (i.e., subcarriers grouped in a number of independent super-channels with different destinations) is presented. Several transponder implementations supporting different transmission techniques are considered, highlighting advantages, economics, and complexity. Discussions include electronics, optical components, integration, and programmability. Application use cases are reported.

Roadmap of optical communications

Quantum physics allows one to produce truly random bits. Moreover, it allows one to distribute them in such a way that one can certify their privacy before eventually using them for cryptography applications. Quantum Random Number generators (QRNG) and Quantum Key Distribution (QKD) have found a few niche markets. Today, some commercial clients use QKD continuously 24×7 a week. In this workshop world specialists will talk about reliability tests in quantum networks; about quantum hacking, its importance and limitations, and its role in classical and quantum cryptography; about high rate and about low cost QKD systems; about free space quantum communication; and about future quantum repeaters for continental scale quantum communication.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 societys 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.

Gridless optical networking field trial: Flexible spectrum switching, defragmentation and transport of 10G/40G/100G/555G over 620-km field fiber

We report the first gridless networking field trial with flexible spectrum switching nodes over 620 km field fibre links. Successful transport, spectrum switching and defragmentation achieved for mixed line signals including 555G and coherent 100G.

Colourless, directionless, contentionless ROADM architecture using low-loss optical matrix switches

We show a novel colourless, directionless, contentionless add/drop optical node architecture using low-loss NxM optical switches which scales to multiple degrees and removes the need for unnecessary network-wide wavelength assignment restrictions

A Cost Model for the WDM Layer

In this paper a detailed capital expenditure cost model is presented taking various network elements and node architectures at the WDM layer into account. It was developed within the European NOBEL project [1] and aligned by major European network suppliers and operators. The current cost structure of WDM transport equipment is shown in a normalised format. Typical model applications are also discussed by presenting examples. This model can serve as a reference for future techno-economic research into optical transport networks in general.

160 Gb/s OTDM networking using deployed fiber

This paper reports a 160-Gb/s OTDM network comprising switching and demultiplexing through field deployed fiber. The 160-Gb/s signal was obtained by time-interleaving 16 channels of a 10-Gb/s signal. The add-drop node was realized by using a gain-transparent operation of a semiconductor optical amplifier (SOA). A subharmonic clock recovery with a prescaled electrooptical phase locked loop employing an electroabsorption modulator was applied. An OTDM receiver employed a four-wave mixing principle in an SOA. The impact of fiber chromatic and polarization-mode dispersion (PMD) is discussed. Switching and demultiplexing performance are shown for a fiber link of 275 and 550 km, respectively. Excellent operation of clock recovery, drop-through-add function, and transmission was achieved.

Planning fixed to flexgrid gradual migration: drivers and open issues

Flexgrid technology has recently been presented as the most promising option for upgrading the currently operating fixed grid optical networks and extending their capacity to be able to deal with the massive traffic volumes forecast for the next decade. Although the current traffic is successfully supported on fixed grid networks, flexgrid technology brings features that are not offered by the fixed grid networks, such as transporting optical connections with a capacity beyond 100 Gb/s and elasticity against time-varying traffic. In light of this, a gradual fixed grid to flexgrid migration is generally accepted in order to add these useful features to the network. In this article, we study the migration process where flexgrid is deployed in the network progressively, and review the main drivers and open issues induced by its deployment.

Experimental demonstration of a gridless multi-granular optical network supporting flexible spectrum switching

A gridless dynamic multi-granular optical network supporting flexible spectrum allocation is proposed and experimentally demonstrated to efficiently accommodate high-speed traffic and increase channel density for lower speed traffic leading to improved network efficiency and scalability.

Saving CAPEX by extending flexgrid-based core optical networks toward the edges [invited]

National IP/multiprotocol label switching (MPLS) networks have been designed using a multilayer approach to take advantage of the optical layers longer reach. In that approach, the IP/MPLS layer performs routing and flow aggregation, whereas the optical layer, based on wavelength division multiplexing technology, transports those aggregated flows into optical connections. However, the flexgrid technology, featuring a finer granularity, also allows the performance of grooming at the optical layer, and hence, the aggregation level of the incoming flows can be reduced. Taking advantage of that fact, in this paper we propose a new network architecture consisting of a number of IP/MPLS areas performing routing and aggregating flows to the desired level and a flexgrid-based core network connecting the areas among them. A two-step procedure to design the whole network is presented where locations are first partitioned into a set of areas, and then each area network and the flexgrid core is designed separately. Mixed-integer linear programming models are developed for the resulting optimization problems. Solving these models, however, becomes impractical for real-sized scenarios so evolutionary heuristics based on the biased random-key genetic algorithm framework are also proposed. Extending the core toward the edges results in significant savings in both the core and IP/MPLS networks.

Core Networks in the Flexgrid Era

This paper reviews the status of research into elastic optical networks and flexgrid, illustrating the benefits of new flexible technologies to allow higher network capacities and support superchannel flows. The paper assesses the potential for the various forms of elasticity and describes open questions of a currently active research area.