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Scalable And Flexible optical Architecture for Reconfigurable Infrastructure

Periodic Reporting for period 3 - SAFARI (Scalable And Flexible optical Architecture for Reconfigurable Infrastructure)

Reporting period: 2016-10-01 to 2017-09-30

SAFARI (Scalable And Flexible optical Architecture for Reconfigurable Infrastructure):
SAFARI is an EU-Japan coordinated R&D project funded by the European Commission and Ministry of Internal Affairs and Communications (MIC), Japan. It will allow European and Japanese research institutions and industries to develop highly scalable & flexible optical data transport networks for the long term future.

Context and motivation
Unrelenting exponential data traffic growth and bandwidth intensive applications are creating an urgent demand for highly scalable & flexible optical transport networks (OTNs). SAFARI will realise such OTNs by developing programmable optical hardware and Space-Division Multiplexing (SDM)-based optical component technologies that allow for multiple independent data pathways through the same optical fibre, greatly enhancing its data carrying capacity.

Today’s digital coherent optical transport technologies based on digital signal processing (DSP) have allowed the commercial realisation of 100 Gbit/s/channel long-haul transport systems capable of providing more than 8 Tbit/s capacity per fibre in installed commercial networks. The introduction of such dynamic DSP functionality has dramatically reduced the network provisioning cost and inventory. However, capacity demands are ever increasing, and to address those requirements in the near future, it becomes indispensable to introduce various types of transport flexibility, for example in modulation format and subcarrier number for super channel transport. Such flexibility will be enabled by progress in DSP functionality in conjunction with flexible optical hardware. Control technologies to manage flexible hardware and transport will thus be urgently needed to provide telecom-carrier-grade reliability for the future OTNs with capacity beyond 10 Tbit/s. Furthermore, within the next 10 years, we will encounter the fundamental capacity limit of conventional single-mode fibres (SMFs) at around 100 Tbit/s due to optical fibre nonlinearity and limitations on the maximum allowable launched power.

SAFARI aims to develop programmable optical hardware, and SDM-based optical components capable of realising highly scalable and flexible OTNs. Specifically SAFARI will:
- Develop programmable optical hardware allowing novel multi-flow transport functions which is scalable to at least 400 Gbit/s/channel transport, and implement the critical interworking capability required between the software-defined network (SDN) layer and the physical layer.
- Develop SDM-based optical transport technologies based on super-dense, high-count multicore fibres (MCFs) and multicore erbium-doped optical fibre amplifiers (MC-EDFAs) capable of Pbit/s level operation.
- Undertake system experiments on scalable and flexible OTNs based on the technology developed within the project. Specific attention will be focussed on demonstrating that the SDN-controlled programmability developed is compatible with both existing SMF transmission systems and future SDM-based systems, allowing for a graceful upgrade scenario.
- Bring together major organisations in both the EU nations and Japan in order to develop the most advanced enabling technologies, to demonstrate their feasibility in an international setting, and to jointly contribute to international standardisation and forum activities.

Conclusion of the Action
By the end of the project, as detailed below, SAFARI proved the viability of the above approach for developing super-capacity OTNs capable of supporting several orders of magnitude increase in capacity with great flexibility in term of control and management. The project has led to a potential pathway to the industrial development of software defined optical networks based on SDM.
Over the course of the project SAFARI established the following key technologies for the realisation of future Pbit/s-class optical transport with a reach over 1000 km with manageable flexibility and control.

- Record core count (32-core) single-mode MCFs offering ultra-low inter-core crosstalk (-40 dB over 100 km).
- 32-core low crosstalk fan-in fan-out devices.
- 32-core C-band integrated cladding-pumped Erbium (Er)/Ytterbium (Yb)-doped fibre amplifiers (EYDFAs) with built-in 32-core integrated isolators.
- In-service XT monitoring scheme applicable to 32-core inline amplified transmission systems.
- Multilayer interworking control architectures between software and physical layers.

By integrating the above key technologies, we have shown the potential of Dense-SDM (DSDM) single-mode MCF transmission systems through the achievement of the following demonstrations;

- 661 Tbit/s data transmission in a 30-core MCF using an AlGaAs frequency comb transmitter
- 32-core DSDM long distance transmission over 1600-km for the first time with PDM-16 QAM WDM channels
- 1-Pbit/s capacity inline amplified transmission within C-band over 205 km based on 680 Gbit/s PDM-16 QAM channels
- 32-core DSDM transmission subsystem over 1000 km using an integrated cladding-pumped EYDFA
- Adaptive rates of WDM/SDM channels using probabilistic shaped PDM-1024-QAM signals for high spectral efficiency using a 30-core MCF
- Final testbed demonstration of single-mode MCF transport networks with crosstalk-aware in-service optical channel control in combination with conventional single mode fibres.

SAFARI published a total of 41 international conference papers (including 2 Tutorial, 19 Invited, 3 Workshop, 5 Postdeadline Papers, 4 Top-Scored Papers, and 21 Peer-reviewed Papers), and 15 Journal papers. The partners also filed 20 patents, several jointly, and won the prestigious Horizon Prize “Breaking the optical transmission barrier”. SAFARI also participated in various standardisation activities and organised two major international workshops in which the project results were disseminated. These achievements highlight the impact that the project has had within the international photonics community.
In the final year of the project the SAFARI team reported two key overall project achievements. Firstly, at NTT Labs in Tokyo, an energy efficient 32-core MCF inline amplified system supporting 1 Pbit/s DSDM transmission within the C-band over 200 km. Secondly, in a joint testbed built at Coriant’s laboratories in Munich the successful interworking of all the subsystems developed within SAFARI which showed that well-controlled single mode DSDM systems offer good interoperability with conventional SMF-based systems and provide manageable flexibility and control when supported by inter-core crosstalk monitoring. The project provided operation beyond the state of the art in terms of subsystem performance, raw transmission performance, and in terms of network functionality and flexibility.

SAFARI has enhanced the performance of leading edge European and Japanese SDN and SDM technologies. At the same time it has provided a new and potentially disruptive capability to the European and Japanese optical communications industries providing them with a leadership position in the field.

The new technologies developed are ultimately expected to deliver improved broadband services (faster, more reliable, increased functionality) which will benefit commerce and the general public alike. It is also likely to find uses in many other sectors reliant on optical fibres including improved monitoring of oil reserves and laser based industrial materials processing.