The rapid growth of data transferred within data centres, combined with the slowdown in Moore's Law, creates challenges for the future scalability of electronically-switched data-centre networks. Optical switches could offer a future-proof alternative and photonic integration platforms have been recently demonstrated with nanosecond-scale optical switching times. End-to-end switching time, however, is currently limited by the clock and data recovery time, which typically takes microseconds, removing the benefits of nanosecond optical switching. Here we show a clock phase caching technique that can provide clock and data recovery times of under 625 ps (16 symbols at 25.6 Gb/s). Our approach uses the measurement and storage of clock phase values in a synchronised network to simplify clock and data recovery versus conventional asynchronous approaches. We demonstrate our technique using a real-time prototype with commercial transceivers and validate its resilience against temperature variation and clock jitter, based on measurements from a production cloud data centre. Main T he rate of data transmitted between servers within data centres has rapidly increased over the last few years [1], driven by cloud adoption and data-intensive cloud workloads such as data analytics and machine learning. Cloud providers have been able to accommodate this fast growth by relying on Moore's Law for networking: every two years the electronic switch integrated circuits (ICs) double their bandwidth at same cost and power. The long-term sustainability of this trend, however, is being questioned by two upcoming challenges: Firstly, similar to processor ICs, scaling transistor density on electronic switch ICs is fundamentally limited by power dissipation as few-nm transistor sizes are approached [2]. Secondly, electronic high-speed serial transceiver data rates are predicted to be hard to scale beyond 112 Gb/s due to the steep increase in dielectric loss when operating at high frequencies [3, 4]. Consequently, increasing the aggregate switch capacity will require a proportional increase in the number of serial transceivers surrounding the chip, resulting in greater power density and packaging complexity. Although continued bandwidth scaling in the near future could be supported by architectural optimisations such as co-packaged optics [5], preserving cost neutrality in the medium-to-long term appears very challenging. This uncertainty has motivated research in optical switches as a viable alternative to electronic switches [6]. Optical switches simply redirect the incoming signals onto output ports without any optical/electronic conversion or digital processing and, hence, they do not suffer from the limitations of transistor or transceiver technology. They could, therefore, provide a future-proof solution for bandwidth scaling within the data centre [7].

We demonstrate a clock and data recovery technique that achieves <625ps locking time for 25.6Gb/s-OOK and show its robustness under worst-case data centre temperature variation. The locking time was improved by 12×, making nanosecond optical switching viable in data centres.

Across the world, policy initiatives are being developed to engage children with computer programming and computational thinking. Diversity and inclusion has been a strong force in this agenda, but children with disabilities have largely been omitted from the conversation. Currently, there are no age appropriate tools for teaching programming concepts and computational thinking to primary school children with visual disabilities. We address this gap through presenting the design and implementation of Torino, a tangible programming language for teaching programming concepts to children age 7-11 regardless of level of vision. In this paper, we: 1) describe the design process done in conjunction with children with visual disabilities; 2) articulate the design decisions made; and 3) report insights generated from an evaluation with 10 children with mixed visual abilities that considers how children are able to trace (read) and create (write) programs with Torino. We discuss key design trade-offs: 1) readability versus extensibility; and 2) size versus liveness. We conclude by reflecting upon how an inclusive design approach shaped the final result.

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Due to the slowdown of Moore’s law, it will become increasingly challenging to efficiently scale the network in current data centers utilizing electrical packet switches as data rates grow. Optical circuit switches (OCS) represent an appealing option to overcome this issue by eliminating the need for expensive and power-hungry transceivers and electrical switches in the core of the network. In particular, optical switches based on tunable lasers and arrayed waveguide grating routers are quite promising due to the use of a passive core, which increases fault tolerance and reduces management overhead. Such an OCS-network can offer high bandwidth, low network latency and an energy-efficient and scalable data center network. To support dynamic data center workloads efficiently, however, it is critical to switch between wavelengths at nanosecond (ns) timescales. Here we demonstrate ultrafast OCS based on a microcomb and semiconductor optical amplifiers (SOAs). Using a photonic integrated Si3N4 microcomb, sub-ns (<520 ps) switching along with the 25-Gbps non-return-to-zero (NRZ) and 50-Gbps four-level pulse amplitude modulation (PAM-4) burst mode data transmission is achieved. Further, we use a photonic integrated circuit comprising an Indium phosphide based SOA array and an arrayed waveguide grating to show sub-ns switching (<900 ps) along with 25-Gbps NRZ burst mode transmission providing a path towards a more scalable and energy-efficient wavelength-switched network for data centers in the post Moore’s Law era.