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The OIF has started work on 800-gigabit coherent interfaces, a follow-on to its 400-gigabit 400ZR specification work.

Two requirements are being addressed: an 800-gigabit dense wavelength division (DWDM) interface with a 80-120km span for data centre interconnect, and an unamplified single-channel fixed-wavelength 2-10km coherent link for campuses.

The need for 800 gigabit

“When we hit that 90 per cent mark on 400ZR, we had people stand up and say: ‘We are ready to start 800ZR’,” says Karl Gass, OIF, physical link layer working group – optical vice-chair.

But completing the work has taken time. “The first 90 per cent of a project takes about half the time and the last 10 per cent takes the other half,” says Gass.

So only in mid-2020 did the OIF’s attention turn to the new standard, starting with determining the use cases.

“For some time there has been a subset of folks that felt this was the next logical step after 400ZR and I think 800 gigabit in general has been building momentum,“ says Tad Hofmeister, technical lead, optical networking technologies at Google and OIF vice president. “That has helped reach the critical mass to take this formal next step.”

800-gigabit specification

Recent developments for 800-gigabit include the maturing of 800-gigabit pluggable multi-source agreements (MSAs), the emergence of 25.6-terabit Ethernet switch-chips and network processing silicon using 100-gigabit electrical interfaces.

The IEEE has also started work on the next Ethernet standard after 400 Gigabit Ethernet (GbE).

With 400ZR, it took time to develop the required coherent digital signal processors (DSPs) and the optical components that could operate at the required symbol rate, says Hofmeister, so it is the right time to start the 800-gigabit coherent work.

The OIF’s 400ZR specification is known for its 80-120km DWDM interface but it also specified an unamplified single-channel fixed-wavelength 2-10km link.

“One reason there wasn't nearly as much attention paid to that application was that there were at 400 gigabit, direct-detect solutions that go to 10km, at LR8 and LR4 now,” says Hofmeister.

For 800 gigabit, however, it is unclear the reach of a direct-detect solution, hence the interest in pursuing a coherent solution, says Hofmeister.

The two 800-gigabit applications are independent but the goal is to make the two designs as common as possible in terms of the components, DSPs and modules.

“The 2-10km application is going to be more cost-sensitive so there may be opportunities to pare down the specs,“ says Hofmeister.

A tunable laser is not needed for the 2-10km link, reducing significantly the module cost.

“In that case, somebody may choose to develop a modulator with a fixed laser that only meets that 2-10km application,” says Hofmeister. “Yet internally it may have the same DSP and the same transmitter optical subassembly and optical receiver as the DWDM variant.”

As for demand for each of the applications, it is too early to say, notes Hofmeister.

Design considerations

The OIF says its latest work will be similar to what was done for 400ZR in that the OIF will not specify the modules to be used.

400ZR uses QSFP-DD and OSPF pluggable form factors while 800-gigabit coherent will use the OSFP and QSFP-800DD modules.

The client-side rates supported will be 8x100-gigabit, 2x400-gigabit and 800-gigabit while the optical output will be a single 800-gigabit wavelength.

The 400ZR uses a 64 gigabaud (GBd) symbol rate and 16-ary quadrature amplitude modulation (16-QAM). The 800-gigabit coherent interfaces won’t necessarily double the symbol rate used for 400ZR.

Instead, the symbol rate may reside between 64GBd and 128GBd which will determine the modulation scheme used. The choice will depend on the state of the component technologies when the decision is made.

“This will be one of the early steps of the OIF discussion,” says Tom Williams, vice president of marketing at Acacia Communications. “My personal opinion is that doubling the baud rate is likely because it would be simpler from a link budget perspective.”

The forward error correction (FEC) scheme also needs to be determined. The signal gain achieved is dependent on the symbol rate and modulation scheme used; the higher the symbol rate, the less powerful the FEC needs to be for a given reach.

Also, the more complex the FEC scheme is, the higher the latency it introduces.

“On latency, it’s not as simple as higher gain means higher latency; the class of algorithm chosen can have a bigger effect,” says Acacia’s Williams. “Of course, the 800ZR application is very power-sensitive as well, so these decisions need to be discussed and worked out in the OIF.”

Gass says the DSP power consumption is one of the concerns with a higher-gain FEC.

The 2-10km 800-gigabit campus link will also require FEC but not as high-gain as the data centre interconnect interface.

“Most likely a higher-gain FEC will be needed than what Ethernet includes, even for the 2-10km application,” says Hofmeister. “If a different scheme is used, we could reduce latency and power consumption for the 2-10km application. For the shorter distance, the latency of the FEC is a larger impact as there is less latency on the fibre path.”

The symbol rate chosen also affects channel spacing.

“For 400ZR, the original effort used 100GHz channels, but there is active work in IEEE and OIF to support 75GHz channels,” says Williams. “Most people are assuming that 800ZR will utilise 150GHz channels.”

Timescales

The OIF has not given a date as to when the 800-gigabit interfaces will be completed.

It took over three years to complete the 400ZR specification work which suggests it will be late 2023 at the earliest.

But Gass says OIF members now have more experience including issues such as interoperability.

“We have a maintenance effort for 400ZR to add the 75GHz grid spacing, but are also updating performance parameters that weren’t normative in the original 400ZR release,” says Gass.

Deutsche Telekom is redesigning its domestic optical network and has chosen Nokia as its equipment supplier.

“They are re-architecting and rolling out, in a short time, a huge portion of their optical network,” says Kyle Hollasch, director of optical portfolio marketing, Nokia. “We are displacing in many parts of the network four different vendors.”

Network architecture

Deutsche Telekom’s legacy mesh-based wavelength-division multiplexing (WDM) network uses equipment from several vendors. In the last decade, Deutsche Telekom also added to the core an IP-optical solution from Cisco Systems.

Now, the CSP is replacing the mesh-WDM network and the Cisco IP-optical core with an OTN-WDM core from Nokia.

“They are unifying their traffic from all of their business services, government services, 5G anyhaul and the core IP network onto one core WDM network,” says Hollasch.

The pandemic made obvious that government was not prepared in terms of their WAN connectivity while businesses are re-evaluating the connectivity requirements they have, he says.

Nokia is the key vendor supplying the OTN-WDM core and ‘close-to-sole-vendor’ for some 900 aggregation sites.

Sitting between the core and the 900 sites are regional horseshoes: open WDM rings that collect traffic from the aggregation sites and passed to the core.

“That is yet to be awarded and we hope to have a portion with another vendor at a later phase of the project,” says Hollasch.

The deployment provides an end-to-end OTN network that offers diverse path, 50-millisecond protection and guaranteed bandwidth. “That is something government and businesses require and that wasn’t easily possible on the existing legacy infrastructure,” he says.

Deployment will start in the second half of this year.

Equipment

Nokia is supplying various chassis from its 1830 Photonic Service Switch (PSS) portfolio that use its PSE-V coherent digital signal processor (DSP) technology and it is also providing its WaveSuite and WaveHub software.

“In the core, it is what you’d expect: it’s scalable WDM with the PSE-V transponders and muxponders, and CDC-F (colourless, directionless, contentionless with flexible grid) multi-degree ROADMs (reconfigurable optical add-drop multiplexers),” says Hollasch.

“It is all about 400 Gigabit Ethernet (GbE) so they can use combinations of the high-end PSE-Vs [super coherent DSP] and we can do 600-gigabit wavelengths anywhere in the country,” he says, enabling combinations of 400GbE and 100-gigabit wavelengths.

For the metro regional, Nokia offers pluggable solutions using its PSE-Vc Compact DSP in a CFP2-DCO pluggable module.

OTN will be supported by Nokia’s 1830 PSS 24x, 12x and 8x platforms, depending on the location in the network. “That platform is largely used in the 900 aggregation sites,” says Hollasch. “For these 900 sites, one of our OTN boxes has 3 terabits of capacity.”

A further Nokia product is the 1830 PSD (photonic service demarcation), a 10-gigabit network interface device (NID) that is the size of a hardback book.

“It can be an OTN NID or an Ethernet NID,” says Hollasch. “That is part of our end-to-end business services solution; they can use that at customer locations.” Nokia also has a product for 100-gigabit demarcation.

WaveSuite and WaveHub software

Nokia is providing what it calls its “digital twin” service which allows real-time simulation of complex networks and preparation for the end-to-end management and control of the network. This software is part of Nokia’s WaveHub ecosystem programme.

“One example of what Deutsche Telekom can do with it is third-party integration with open APIs (application programming interfaces) into a digital twin of their exact network,” says Hollasch. “So even before any box has shipped, they can start integrating ther multi-vendor end-to-end transport controller onto our gear.”

One element of Nokia’s WaveSuite software tools offered is the Commission Expert that simplifies the deployment of customer premise devices. Another component is Network Insight which uses telemetry data from the DSPs as input to machine learning techniques to manage optical wavelengths, make best use of network capacity and predict network failures.

“This [Network Insight] is a product that has almost become a selling point in any large core network,” says Hollasch.

Nokia offers its software to CSPs and points to the value it believes it adds. “But the table stakes are the APIs and being able to integrate to those,” says Hollasch.

Transition year

Nokia says 2021 is a transition year for the industry regarding the emergence of pluggable coherent modules: 400ZR, ZR+ and CFP2-DCOs.

“We need to see hardware in networks sending bits and we haven’t yet, except for small trials,” says Hollasch.

There will also be industry announcements regarding next-generation pluggables that will use 5nm CMOS DSPs and operate at a symbol rate of up to 130 gigabaud.

Such pluggables will send 800-gigabit wavelengths over longer distances and be able to transmit two 400GbE streams.

“400GbE will be the predominant interface for a long time; the IEEE doesn’t even know what the next Ethernet rate will be,” says Hollasch.

Last summer several individuals, including representatives from Telefonica and Deutsche Telekom, published a White Paper on the need to boost innovation in the telecom industry.

Six months and many conversations later, the group published its second paper, this time focussing on the communications service providers (CSPs), vendors and the investor community.

The paper, entitled Developing a Code of Conduct Framework for the Telecom Ecosystem, highlights four areas to spur innovation: Funding, Innovation Processes, Competition and Procurement.

The code-of-conduct paper offers guidelines as to how CSPs can work with vendors, especially small and medium-sized ones that lack the resources of the larger established vendors.

Innovation

The group’s White Paper argues that, in an era of accelerating and disruptive change, the CSPs are proving to be an impediment.

The CSPs’ networking infrastructure has its own inertia; networks are complex, vast, and have long-investment cycles, measured in years. Operators also need a solid business case before undertaking expensive network upgrades.

Meanwhile, the return on investment for vendors bringing new products to market is lengthy, making it harder to justify product development and limiting the risk vendors are willing to take.

Accordingly, diminished innovation is costly, not just for the CSPs but for the industries dependent on their connectivity services. Practices must change if the CSPs are to boost innovation.

This is what the group’s latest paper tackles: it pinpoints areas that must be improved if CSPs are to attract smaller players and startup that can inject much-needed innovation.

“We have initiated a conversation in the industry that hasn’t been had before,” says Don Clarke, formerly of BT and CableLabs and co-author of the two papers.

The conversation Clarke refers to is how to solve the issues of deploying technology that has nothing to do with the technology itself.

These barriers are caused by issues of organisations and processes, what Clarke calls ‘the telco culture’.

Issues addressed

The Code of Conduct paper lists practical steps for each of the four categories. “Each one on its own isn’t going to solve the problem,” says Clarke.

Under Funding, the paper considers how the telecom industry can become more appealing for investors and how capital can be injected to help smaller vendors and start-ups.

“If venture capitalists are not willing to invest in start-ups in our industry because it takes too long before their stuff gets into the network, or telcos don’t want to buy from them because they are too small, what do we do about the funding problem?” says Clarke.

He also highlights telecom’s lack of high-profile entrepreneurs, the equivalent of an Elon Musk or a Jeff Bezos. “There is no supernova that is pulling people into our industry; the industry is moribund,” says Clarke.

One idea the paper promotes is for the CSPs to set up a fund to help start-ups. Another refers to actions to attract investors to the telecom industry.

Governments can also play a role in aiding Competition, the second issue addressed.

“Governments might give tax breaks to smaller companies,” says Clarke. The group is in discussion with the UK Government’s Steering Committee on Telecoms.

One issue for Innovation Processes, says Clarke, is that the operations departments of the CSPs have so much to deal with daily that they have little time for anything new: “How does innovation get consumed by telecom companies when operations is so reluctant to take on new things?”

Suggestions include highlighting innovative new technology requirements in Request For Information (RFI) and Request for Proposal (RFP) documents and limiting the time it takes for new technology to get to the lab (6 months) and field trials (18 months).

Procurement, the fourth and final category, must be streamlined since the demands exclude smaller companies from getting a foothold. For example, CSPs could pay software licences up-front and not when the code is finally used.

“We are talking about procurement processes that are too onerous; it doesn’t matter what the technology is, the procurement process is broken,” says Clarke.

Next steps

The group aims to expand its influence by adding individuals that will help drive these threads in parallel. One person that has joined the group and that contributed to the second paper is Andrew Coward, the CEO of Lumina Networks, a software-defined networking start-up that folded in August 2020 yet was working with AT&T and Verizon.

The group will also meet strategic staff at CSPs. “We already know they are aware of our work,” he says.

What gives the group confidence its initiative will spur innovation?

Telecoms must retain control of its destiny, says Clarke eventually; it is so fundamentally important, to countries and the world.

“Telecoms must continue to evolve; it can’t afford to decay with a stagnant infrastructure,” he says. However, such evolution is threatened because of diminished innovation.

“This initiative is about figuring out how to reboot innovation in the industry,” says Clarke. “I don’t know which of these areas is the most important; maybe all have a role to play as all influence the culture.”

The output of innovation in the telecoms industry is a Request For Proposal (RFP), he says, an order for a capability or something being bought from the industry.

If CSPs buy only from large vendors, they become less motivated to innovate. Equally, the vendors depend on the CSPs moving fast enough. “If there is no buying, there is no investment,” he says.

Telecoms is also experiencing disruption. The global pandemic has if anything made telecom even more important. There are also geopolitical issues such as Brexit, and the trade war between the US and China.

“What we are experiencing and the disruption will force the changes that need to be done,” says Clarke.

A successful outcome of the group’s work will be if two or three of the initiatives highlighted in the Code of Conduct document are embraced by several CSPs, says Clarke.

Further Information:

The Telecom Ecosystem Group, click here

Each year Gazettabyte asks industry figures to pick their reads of the year. Industry analysts and regular contributors Dana Cooperson and Andrew Schmitt kick off this year's highlighted books.

Dana Cooperson, independent analyst

I had difficulty concentrating enough to read during the lockdown despite having more time. Eventually, events spurred my overdue fiction/ non-fiction exploration of the underpinnings of systemic racism as well as some escapism through journeys that the pandemic made impossible.

Five of my books fit the first category: four explore the legacy of human slavery in the US and the African-American experience, while the fifth, Trevor Noah’s memoir, traces similar terrain in apartheid/ post-apartheid South Africa.

Just Mercy: A Story of Justice and Redemption by the lawyer and equal justice advocate, Bryan Stevenson, uses statistics and egregious cases of the miscarriage of justice that lead to the unequal application of capital punishment.

Stevenson intersperses the shocking case of Walter McMillian, a young, self-sufficient Black man who was wrongly accused of killing a white woman, with tales of his founding of the Montgomery, Alabama-based non-profit Equal Justice Initiative (EJI), and a procession of cases EJI litigated on behalf of poor, minority, and juvenile clients.

One wonders how Stevenson and his team could work doggedly on these cases while facing death threats and obstacles. There are few happy endings for the accused yet the book is ultimately hopeful.

The Warmth of Other Suns: The Epic Story of America's Great Migration by journalist Isabel Wilkerson is a history of the migration of six million African Americans from the agrarian Jim Crow South to the urban north and west of the country between 1915 and 1970.

The book weaves broad historical and sociological data with the bittersweet stories of three individuals who migrated to escape terrorism and lack of opportunity. It also helped me piece together historical underpinnings of today’s fight for justice, as epitomised by the Black Lives Matter movement.

If the statistics don’t move you, the stories of Ida Mae Brandon Gladney, George Swanson, and Robert Joseph Pershing Foster will. (Note: Wilkerson recently published a follow-up, Caste, which my reading buddies recommend.)

James Baldwin’s Go Tell It on the Mountain is a semi-autobiographical novel about an African-American boy growing up in 1930s Harlem. This beautifully written, structurally interesting book focusses on fourteen-year-old John, who is struggling with poverty, abuse, and religious faith; and John’s father, Gabriel, mother Elizabeth, and Aunt Florence, all of whom escaped Jim Crow and who all struggle. Baldwin writes with imagery and passion. I had not read Baldwin before.

This year I also returned to Tony Morrison, with Sula, another tale of African-American diaspora that begins in 1919 Ohio. Like Baldwin’s book, Sula deals with intergenerational trauma and features indelible characters and powerful prose. A slim book, deep in characterisation and emotional punch.

A no less passionate book, infused with its author’s gift for making people laugh, is comedian Trevor Noah’s memoir, Born a Crime: Stories From a South African Childhood.

The book’s title refers to South Africa’s Immorality Act of 1927, which made his birth by a black Xhosa mother and white Swiss father in the waning days of apartheid punishable by five years in prison.

The book details the hoops his family jumped through to avoid incarceration during apartheid and Noah’s chameleon-like abilities to navigate South Africa’s bizarre race-based caste system and a thriving black-market economy.

A polyglot, Noah’s facility with languages was key to his ability to navigate situations, some of which were life-and-death serious.

Rounding out this year’s recommendations are four excellent books that took me to different times and places.

The Awakening, published in 1899, deals with protagonist Edna Pontellier’s search for meaning and escape from the strict social customs of nineteenth-century New Orleans society.

The book, which treats adultery unapologetically, created such a backlash against author Kate Chopin that she stopped writing. My daughters, who read the book in school, tipped me off to this classic. The ending, which I won’t spoil, leaves one wondering whether this a feminist tale and the ending's meaning.

If you are looking for a diverting read, you can’t do better than something— anything— by Bill Bryson. Bryson is an Iowa-born journalist and author who ruminates on such topics as language, culture and history.

This year I read Bryson’s At Home: A Short History of Private Life which uses the Victorian parsonage where he lived in “a part of England where nothing of any great significance has happened since the Romans decamped” to anchor a room-by-room history and cultural reflection on the evolution of private life.

His writing roams across ten thousand years of history, etymology, and sociology, such as how the “hall” evolved from the most important room in a domicile to “a place to wipe feet and hang hats” and how “limelight” became associated with the theatre.

Circe by Madeline Miller is a retelling of Homer’s The Odyssey from the perspective of the titular sorceress, who is banished by Zeus to a remote island. Confusing at first, the novel is ultimately rewarding for those interested in mythology. Spoiler alert: Odysseus does not fare well in this version of the tale.

News of the World by Paulette Giles is a sweet little book "soon to be a major motion picture" starring Tom Hanks.

The book is set in the aftermath of the US Civil War in 1870s Texas. Septuagenarian war veteran, Captain Jefferson Kyle Kidd, is an honourable man who makes his living travelling to towns and charging a fee for reading newspapers from around the world. He agrees to take a young German orphan girl, who has been recaptured (and questionably “liberated”) from the Kiowa tribe that killed her parents, to her relatives 400 miles away. What is the right path for the Captain and his charge? Don’t wait for the movie to find out.

Let’s hope 2021 is a better year for all.

Andrew Schmitt, founder and Directing analyst at Cignal AI

I was told The Bitcoin Standard was the book to read to get a perspective on the technology. It is indeed a good book though heavily biased in favour of bitcoin and against the global government fiat money scheme. It keeps the politics in the background and is a good primer to understand what is supposedly happening with Bitcoin.

I re-read Dune by Frank Herbert in anticipation of the new movie after first reading it decades ago. It's a great book but requires investment, and the payoff is just entertainment. I never read the sequels after reading the first book and I don't want to now.

In American War by Omar El Akkad, a future America is torn by civil war due to climate change. The book was recommended to me; I can't recommend it myself. I'm just not into bleak disaster themes anymore. It will probably become another Netflix series.

I also re-read The Good Shepherd by C. S. Forester in anticipation of the movie that was never generally released. I read it when I was young; I don't remember why. It's well-written and now I want to look at his other works.

I ended up seeing the movie on AppleTV, which tried to capture the captain's deep thinking that the book expresses so well. But this was a battle fought in the captain's mind and you need to read the book to see it correctly.