In a digital world, optical transport networks are the critical links connecting communities and industries. As bandwidth, reach and latency demands increase, network owners must continue to expand and evolve their optical networks. Advances such as next-generation transponders and more capable ROADM technologies are indeed enabling optical networks to perform at levels unimagined ten years ago. Yet, the continuing advancement of high-speed optical transport networks comes at a time when the world is coming to grips with the unintended, but very real, consequences of manmade climate change.
While the ICT industry only accounts for an estimated 1.4% of global greenhouse gas emission, that impact may very well rise in the near future. A 2021 report by the International Energy Agency noted:
“Since data transmission networks generally have high fixed energy costs (even at low utilisation), the build-out of infrastructure to accommodate greater anticipated peak capacity could raise overall network energy use in the long run. Furthermore, emerging digital technologies such as blockchain, machine learning, 5G and virtual reality are also poised to raise demand for data services.”
Developing optical networks that can meet the growing needs of a data-driven world, while minimizing our environmental impact requires new, more innovative technologies designed to balance performance and enhanced sustainability. Recent technology developments are now making that possible.
Liquid Cooling Technology
Optical network speeds are steadily increasing while blade and server designs shrink. An unintended consequence is the increased thermal loading concentrated in ever-smaller boxes and cabinets. Managing this heat buildup has typically involved use of large air-cooling fans which consume a relatively large amount of energy. As processing speeds increase, more powerful and faster-spinning fans are needed to dissipate the heat. This, in turn, is driving energy requirements of cooling parts higher and decreasing their lifespan.
The introduction of liquid cooling systems provides energy savings on two fronts. First, the higher density DSP needed to operate at terabit rates will generate higher temperatures then previous versions in the same footprint. Liquid cooling provides far better heat transfer than pure air cooling, and thus maintains a lower operating temperature. Second, the energy consumed by the cooling system itself is lower for liquid cooling compared to air cooling.
In principle, the liquid cooling system operates much in the same way as a car air conditioner or refrigerator. A coolant flows through the system, soaking up the heat, and delivers the heat to a metal radiator where it dissipates into the air with the help of small fans. But unlike a car or refrigerator, this cooling technology is maintenance-free – it never needs a coolant top-up or replacement. The system also supports drip-free, leak-free insertion and removal of modules without the need for specialized tools or processes. While fans are still used in the system, they are far smaller and operate at lower speeds compared to a purely air-cooled system. This results in a compact footprint, quieter operation and having a longer replacement and maintenance cycle. Hence this technology can be deployed without changing the operating environment or operating procedures.
A second important trend that promises to help networks reduce their carbon footprint are the recent developments that enable extended optical reach and enhanced wavelength and fiber capacity. These include a new generation of 135 GBaud transponders and a recent break-through in RAMAN amplification.
Compared to today’s 100 GBaud class transponders, new 135 GBaud transponders support significantly higher maximum bit rates—1.2 TBps vs. 800 Mbps—on a single wavelength. Perhaps more important from a sustainability perspective, the 135 GBaud transponders use a denser 5nm DSP that requires about 39% less energy than 100 GBaud transponders with 7nm DSPs.
Meanwhile, an important recent advance in RAMAN amplification has opened the door for greatly enhanced distances or capacity. Until now, Raman amplification has been limited to backward-facing applications in which the Raman amplifier is on the receiving end of the fiber span (Backward RAMAN). Adding a second amplifier at the beginning of the span (Forward RAMAN) could significantly boost the optical reach but creates unacceptable levels of relative intensity noise (RIN).
Working with Furukawa Electric Co., Ltd. as key technological partners, Fujitsu has developed a Forward Raman amplifier that minimizes RIN distortion. This development makes it practical and highly beneficial to deploy Backward + Forward RAMAN to increase optical reachability or fiber capacity.
There are two benefits of these advances: extended reach enables network operators to reduce or even eliminate regeneration equipment for some optical links, resulting in significant reduction in power consumption/bit/km. Also, Forward Raman can be used to increase fiber capacity. Given the same distance, a Forward Raman amplified signal has a higher GSNR. This means a higher order modulation (more bits per Hz) can be used within the spectral width, and hence increase overall fiber capacity, which can be used with larger channels (more Hz) resulting in fewer transponders needed. In either case, the impact on the environment is positive.
A Systems-Based Approach to Enhanced Sustainability
Given the rapid escalation of global warming, any one of these technology advancements, while positive, is not enough. When combined in a systematic approach, however, the benefits are multiplied. If applied to the global ICT sector, at scale, they are multiplied yet again. This is what Fujitsu has done with our new hyper-reliable 1FINITY™ Ultra Optical System.
Designed for terabit networking, the 1FINITY Ultra Optical System helps network owners address the need for high-speed/extended reach performance while pursuing more aggressive sustainability goals. Its unique systems design delivers up to 40% more capacity or up to 40% longer reach compared to current systems, while lowering cost/bit/km and providing significant energy and environmental savings.
Pursuing a bigger goal
The enhanced sustainability of the new 1FINITY Ultra Optical System reflects Fujitsu’s deeper commitment to the environment that suffuses everything we do. Our goal is to achieve zero CO2 emissions by 2050 through innovative energy conservation using cutting-edge technologies and strategic use of renewable energy and carbon credits. Leveraging HPC, AI and other technologies, we are developing more responsible infrastructure solutions that help the ICT sector and the world reduce and reverse the damage caused by climate change.
Recent and ongoing extreme climate events across the globe are now sounding a warning that is impossible to ignore. As an industry, we have the ability to make a significant contribution to help the world change course. Fujitsu’s vision of a more responsible and sustainable network blends the benefits of converged technologies with environmental sensitivity. It’s taking shape today.
The Fujitsu 1FINITY Ultra Optical System
The ideal balance of speed, reach & capacity – simplified
[i] Building sustainable 5G networks for a net-zero world; Fierce Wireless; Dec. 13, 2021
[ii] Data Centres and Data Transmission Networks; International Energy Agency, report; November 2021