Exploring new frontiers in optical networking
The world’s appetite for bandwidth continues to grow with no obvious limits in sight. Current projections are 30 - 40 percent per year, and within a dozen years, we’ll be looking at networks needing to supply 100X of their current capacity. But when it comes to the physics involved in moving bits across fiber optic networks, there are some very real limits. One of these is the Shannon Limit, which has now been reached when it comes to spectral efficiency, or the maximum capacity that can be achieved on a fiber. There are also very real boundaries on network power use, associated with economics and climate change. These limits call for innovative approaches that will help us to open new frontiers in optical networking and continue to meet the world’s growing need for connectivity.
For the last decade, we’ve expanded bandwidth in the network by increasing the performance of coherent modem implementations. With fiber capacity and spectral efficiency now limited by the Shannon Limit, we must look for other ways to enable further scale and performance that will drive ongoing reductions in network TCO. We can add more optical components and boost power, but then we run into other limits like the cost of electricity and the size of our carbon footprint.
The trick is to get more bandwidth while reducing the overall “cost per bit”. This can be done in several ways: reducing power used, reducing the number of optical Interfaces in the network by increasing the reach of transmission, and enabling more capacity to be deployed per line card, while leveraging existing platforms to avoid forklift upgrades.
Power use has always been part of the calculation of total cost of ownership (TCO) by network operators, but with the rise in energy costs and the geo-political uncertainties around future supplies, it has taken on added importance. Power use is also a pretty good proxy for carbon footprint; reducing this has now become a global priority for our planet. This is changing as utilities slowly shift to renewables, but, with a few exceptions, the power consumed by the world’s networks is still largely generated by burning fossil fuels, so reducing power use usually means less CO2 produced.
Delivering the most advanced coherent optics
One approach to the cost per bit issue is to deploy fewer optic components for a given amount of capacity. The PSE-6 super-coherent DSP (digital signal processor) leverages the latest silicon CMOS 5-nm process technology, which is allowing us to achieve ~130GBaud operation for greater wavelength capacity per linecard, and transmission distances that go 3X further than the previous generation of 7-nm DSPs.
Figure 1: PSE-6s delivers the most advanced super-coherent technology for today's networks
Because there is inverse relation between distance and capacity, the alternative approach, more attractive to regional and metro carriers, is to fit more services on shorter links. Using two PSE-6s bonded together and able to share client capacity in a single linecard, we now offer a 2.4Tb/s optical transport engine. This allows network operators to transport three 800GE services per linecard compared to current coherent solutions operating at 800Gb/s that can only carry one 800GE service, or single-wavelength 1.2Tb/s solutions that strand the additional available capacity.
Meanwhile PSE-6s also gives ultra-long-haul networks a boost by enabling them to transmit 800GE services over 2000kms without regeneration, which can significantly reduce the number of interfaces used in the network.
Both approaches reduce the cost per bit for new bandwidth, along with the costs of deployment, by leveraging the new power of the PSE-6s in different ways.
Very importantly, the same technical advances in PSE-6s that enable more scale and better performance also enable significant reductions in power consumption. By reducing the power per bit with the latest generation of 5nm coherent optics, combined with a reduction in the number of optical linecards and facilities to house and cool them, network operators can reduce network power by up to 60 percent, as shown in figure 2. If we compare our first-generation PSE optical engine, the PSE-6 is 95 percent more efficient in terms of cost per bit. That’s an impressive reduction.
Figure 2. How PSE-6s reduces total power consumption improves for a range of networks
At Nokia, we’ve always designed for the longevity of our platforms, and the PSE-6s is no exception. The PSE-6s can be implemented across our entire 1830 platform from compact modular rack-mounted units to our OTN switching and SLTE platforms. It is managed by the same software with no integration needed. The ability to introduce it into existing network platforms reduces equipment obsolescence, landfill waste, and enables network operators to extend the life their investments, lowering capex spend as well as improving opex.
I’m proud of what the Nokia team has accomplished over the last decade in bringing continual innovations in coherent optics that directly impact our customers' top and bottom lines, and the challenge continues to inspire us. What can we achieve in the next?
Our future depends on building networks that have the capacity and scalability to help the world act together with a smaller environmental footprint. Network operators can meet those needs, helping us to explore new frontiers in the emerging new high-bandwidth applications such as AR/VR, Industry 4.0 and 5G, and some which haven't even been invented yet.
The Nokia PSE-6 super-coherent optical engine is opening these new frontiers while staying within the limits imposed by economics and the environment. It helps network operators scale while reducing TCO, supports transport of new 800GE services over three times the distance, and can require up to 60 percent less network power.
Faster, farther, greener. The math has never looked more sustainable.
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