Speakers at "The Evolution for Next-Generation Optical Networks" workshop session at ECOC 2018 in Rome delivered a compelling vision of next-generation optical networks and how they will support cloud and 5G services. The presentations from experts at operators, equipment suppliers and academic institutions based in the US, China and Europe were very well received by the audience in a packed room with more than 200 attendees. Speakers covered a wide range of key topics, including: bandwidth growth; enhanced 200G via probabilistic constellation shaping; 400G and beyond single-carrier operation; optical integration; and machine learning in optical networks.

Peter Winzer of Nokia Bell Labs, and chair of ON2020, reviewed network traffic evolution and trends that will drive optical network technology scaling through the next 20 years. ON2020, an IEEE Industry Connections Activity, is working on traffic evolution in optical networks over the coming ten years, optics integration into switch and coherent engines, and the transport network physical layer and autonomy/control. Winzer showed multiple charts demonstrating 60% per year traffic growth and 45% per year growth in global optical port capacity sales over the past ten years. Based on future growth projections, Winzer concluded that optical network technology scaling over the next 20 years will require more parallelization and integration in wavelength and space, and a shift towards full optics-electronics integration using fiber-in-fiber-out (FIFO) communications engines. (If you wish to join the discussion in ON2020 or get to know more details, please sign up through ON2020 IEEE website at https://standards.ieee.org/industry-connections/optical-networks-2020.html.)

Zhang He, representing the NGOF core team, explained that the NGOF (the Next Generation Optical transport network Forum) was founded in December 2017 with the goal of building an open cooperative platform and promoting the development of the optical transmission network industry. NGOF currently has 26 member companies, including leading carriers, equipment suppliers and semiconductor vendors. Zhang He reviewed current works within NGON that cover several key market areas including the 5G bearer network, MAN optical modules and new-generation cloud and private lines. On behalf of NGOF, He welcomed close cooperation with ON2020.

Dr. Kevin Smith, until very recently with BT, discussed the development of high-speed transmission towards 400G per wavelength and beyond. He explained that 100G per wavelength using coherent DP-QPSK has become the de facto standard for development, although 200G is also now a mature technology with a number of modulation formats available and deployments in live networks. BT has recently conducted successful transmission of enhanced 200G with real-time PCS (probabilistic constellation shaping)-based coherent transceivers developed by Huawei. Developments are now moving to 400G single carrier with a long-reach coherent 400G solutions based on 64GBaud DP-16QAM being demonstrated. The demonstration covered the first Terabit superchannel based on 400G single carrier and used 3x 400G channels with 64GHz spacing. Smith expects future PCS advances will further enhance reach and spectral efficiency for 400G and beyond.

The huge bandwidth that will be available to end users through the introduction of 5G is causing network providers to upgrade their transport networks, and Maarten Vissers from Huawei gave us an insight into some of the developments for mobile-optimized multiservice metro cloud OTN (M-OTN). M-OTN is a profile of OTN that has been optimized for metro deployments to support mobile networks. The M-OTN architecture consists of metro-core, metro-aggregation and metro-edge OTN networks. The metro-edge networks directly support cloud and distributed RAN architectures. Key elements of M-OTN network architecture are the use of FlexO interfaces that support a wide range of speeds and support for network slices.

The session was concluded by two professors from Politecnico di Milano in Italy, who shared the results of some of their research and how their works will enhance future optical networks. Professor Massimo Tornatore explained that machine learning gives computers the ability to learn through data observation without being explicitly programmed. The new degrees of freedom in optical networks made available through greatly increased flexibility and software-defined networking (SDN) mean that these networks can significantly benefit from machine learning. A key approach that Prof Massimo has researched involves a quality of transmission (QoT) estimation that is used to optimize routing and spectrum assignments. Machine learning is also being used to identify soft failure modes and ensure early detection to minimize service downtime. Professor Andrea Melloni reviewed the latest developments for photonic integrated circuits (PICs), which view the photonic chip as a complete system including control and calibration, actuators and sensors.

This workshop session was a fascinating insight into some of the latest developments for optical networks and I look forward to future sessions, including an ON2020 workshop being planned for the OFC 2019 show floor.

This article was sponsored by Huawei.

— Simon Stanley, Analyst at Large, Heavy Reading