January 27, 2021


The challenge

Cloud computing, 5G and Internet of Things (IoT) have a major impact in our everyday lives. Consider a moment when you are watching a live sports game or 4K video content on your cell phone, participate in online courses, webminars and scientific conferences, store your photos and files and make them accessible from your phone, tablet or computer, control your household devices through cell phone applications, monitor your work-out performance and health status of your elderly ones, you are using the Internet and more specifically the Cloud.

The above use cases employ a large number of connected devices including computers, tablets, phones and wearables on one hand, and on the other, a massive number of servers located in large buildings across the globe called datacenters; all interconnected to one another which are used to store and fetch all the above information to you anytime, anywhere, fast and in a secure manner. According to CISCO, the number of devices connected to IP networks will be more than three times the global population by 2023 [1]!

Information is represented by bits of data which are transmitted, forwarded and received within datacenters across a few meters or a few kilometers (500m-2 km) and from one datacenter to another over tens of kilometers (10-40km) by means of optical transceivers and switches. More data means more transceivers and more switches for their interconnection and at the same time this means even more power consumption. It is worth noting that datacenters already consume more than 2 percent of the world’s electricity having quite a significant environmental footprint [2]!.

Datacenter operators struggle to keep pace with the bandwidth-hungry and time-sensitive cloud applications which are responsible for the immense growth of global Internet traffic.  It is noteworthy that datacenter traffic only is expected to reach 19.5 Zetabytes per year by 2021 ramping up from 6 Zetabytes per year in 2016 [3]! As Internet traffic grows, the size of the datacenter grows yielding a direct impact on airflow management and cooling. Cost is also tightly related to the increase of datacenter traffic considering that larger datacenter space is required which in turn increases capital (CAPEX) and operational (OPEX) expenditure.

The next datacenter upgrades will involve the deployment of novel ultra-high speed optical transceivers and ultra-fast switches capable of supporting the traffic demands in terms of bandwidth and latency. These rely on the combination of high-speed photonic and electronic technologies as well as novel co-integration and packaging concepts which are eagerly sought leveraging in tandem power consumption and cost benefits.


TWILIGHT is a Horizon 2020 ICT project funded by the European Commission and the Photonics Public Private Partnership (PPP) which addresses the transformation of datacenters in two-fold approach: a) it targets the development of terabit high-speed optical transceivers and nanoscale optical space switches exploiting the best of photonics and electronics technologies; InP membranes and InP-HBT electronics and b) it introduces novel photonics and electronics co-integration and co-packaging concepts.

So far, the development of optical transceivers relies on the hybrid integration of photonics and electronics components which have to comply with specific form factor pluggable modules placed on the front panel of a digital switch inside a datacenter. Moreover, the operating speed of transceivers is limited by parasitic effects stemming from the long wire interconnections between the photonics and the electronics components. TWILIGHT introduces two significant innovations to resolve this challenge. First, it exploits photonic integration as a Key Enabling Technology to host multiple photonic components and functionalities on the same chip generating large scale Photonic Integrated Circuits (PICs), in combination with InP membrane technology enabling PICs with reduced footprint. Secondly, it envisions co-integration of photonics and electronics components based on full wafers rather than components typically placed side-by-side that inevitably consume much more space. This yields ultra-tight photonics and electronics co-integration via ultra-short electrical connections (RF vias ~ 20μm) eliminating parasitic effects and allowing for ultra-high speed operation of the transceiver.

Furthermore, TWILIGHT revolutionizes on the packaging scheme of its transceiver modules moving away from the standard form factor pluggables at the front panel of digital switches and introduces the concept of Multi-Chip-Module (MCM) based on which the optoelectronic engines (OE) are placed as satellite chips around the ASIC switch chip on the same high-speed host board. This allows to scale the overall capacity of digital switches from 12.8T (currently deployed today in datacenters) to 51.2T!

At the same time, TWILIGHT will respond to the massive interconnectivity in growing datacenter environments via the development of ultra-fast optical space switches again exploiting photonic integration and InP membrane technology. The switch architecture will be modular which means that it will easily be scalable to large number of input/output ports and hence it will facilitate the increasing number of interconnections within the datacenter as dictated by modern applications.

TWILIGHT technologies are expected to enter the datacenter market after a 6-9 year framework leveraging more than 70% power consumption savings and cost 0.89€/Gb/s.

For more technical information of the project please follow the “Objectives” and “project public documents”.


  1. Cisco Annual Internet Report (2018–2023) White Paper, March 2020.
  2. https://www.datacenterdynamics.com/en/opinions/power-consumption-data-centers-global-problem/
  3. Cisco Global Cloud Index: Forecast and Methodology, 2016–2021 White Paper.