Optical Connections Magazine Spring 2024

Bringing the World the Latest in Optical Communications News

ISSUE 36 | Q1 2024



Q&A with Steve Roberts | p8

FIBRE FUTURES: Andreas Rü sseler | p20

BATTLE OF THE BANDS: John Williamson | p16


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8 EXA’s Expansion Plans Steve Roberts 12 Compound Semiconductors Paul Momtahan 16 Battle of the Bands John Williamson 18 Altnet Convergence Matt Reese 20 Fibre for Everything Andreas Rü sseler 22 MPO Connectors Liam Taylor 24 Speeding FTTH Rollout Antony Savvas 26 800ZR/ZR+ Pluggables Eugene Park 28 EPIC CEO Interview Jean-François Vinchant 30 TOP Conference Wrap Peter Dykes

INVESTMENT, CONSOLIDATION, INNOVATION: AN INDUSTRY ON THE MOVE Welcome to the spring 2024 edition of Optical Connections. We kick off with a rare interview with an infrastructure provider in the form of EXA. The proliferation of hyperscale datacentres is now a fact of life for the fibre optic communications industry, so we spoke with the company’s SVP, Strategic Investments and Product Management Steve Roberts , about how the company is meeting the bandwidth challenge through investment and network expansion. Far from expanding however, some companies are more likely to consolidate. So argues Matt Rees , CTO, at Neos Networks. With over 100 altnets in the UK, something’s got to give, he says. Meanwhile, Infinera’s Solutions Marketing Director Paul Momtahan , argues that silicon is not the only strategic semiconductor. To meet the ever-growing volume of traffic being carried globally, veteran journalist John Williamson looks at the possibility of extending the available wavebands, as fibre gets evermore congested. Indeed, demand for fibre is coming from a number of different directions, and Andreas Rü sseler , CMO at R&M examines what the future of fibre will look like. But as governments, businesses and consumers are demanding more extensive and faster fibre- based networks, telecoms writer Antony Savvas asks how the connectivity industry is servicing these needs. Of course, networks need to run smoothly and error-free, so keeping connections free from dust and static is of vital importance, and Liam Taylor , European Business Manager, Fibre Optics, at MicroCare UK Ltd explains the best ways to do it. All this, plus the latest industry news and products, along with a busy events roundup, in another edition packed with discussion and thought-leading features. Peter Dykes Contributing Editor

32 OFC Preview 34 Product Focus


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ISSUE 36 | Q1 2024


AI race begins to impact on optics suppliers

to more business from Nvidia, but the company has not disclosed any of the details yet. Fabrinet (Nvidia’s contract manufacturer) reported 20% growth in datacom revenues, driven primarily by “800G AI programs”, but the company noted that “the rate of sequential growth has begun to moderate”. Fabrinet’s guidance for Q1 2024 is almost flat. LightCounting says all these data points confirm the trend observed in the past: Nvidia manufactures most of the optics internally (at Fabrinet) for the first year of deployments but allocates

According to a research note on the early financial results for Q4 2023 from LightCounting, demand for 4x100G and 8x100G transceivers from Nvidia made its first significant impact on the revenues of two transceiver suppliers in Q4 2023. Coherent reported more than US$100 million in revenues from sales of 800G transceivers – up 100% sequentially and the company expects further growth in 2024. Innolight reported more than US$505 million in Q4 revenue – up 30% y-o-y and 20% sequentially. Most of this growth must be also related

(11%). Q4 2023 spending growth was either “way up” or “way down”. Alphabet reported record high capex and both Alphabet and Microsoft reported spending increases of 45-55%. In stark contrast, Amazon, Apple, and Meta reported spending declines of 12%, 37%, and 15% respectively, but all of them spent more in the last two quarters sequentially. LightCounting concludes that the market momentum is positive as we enter 2024 – a huge change from 12 months ago. AI is the hottest area now, but it expects a recovery in the broader market to start in Q2 2024.

the bulk of the volume to Coherent and Innolight after that. This is exactly what is happening now with 4x100G and 8x100G transceivers. Both Coherent and Innolight have extensive manufacturing capacities to support a sharp ramp in production during 2024. Revenue growth picked up in the third quarter and again in the fourth quarter, with Alphabet, Amazon, Meta, and Microsoft all reporting double-digit year-over-year growth and new record highs. Apple sales improved slightly compared to Q4 2022 (up 2%), although its Services business grew faster

EXA plans hybrid trans-Atlantic route

XGS-PON to fuel new spending cycle beginning 2025

London-based infrastructure company EXA, is planning to introduce a new hybrid microwave-fibre route between New York and London, adding to its ultra- low latency transatlantic connectivity. EXA already owns and operates the lowest latency transatlantic cable, EXA Express, and the company says this additional technology enhancement is crucial in applications like financial trading, where minimal delays are imperative for maintaining a competitive edge. “The demand for accelerated connectivity between leading financial exchanges remains unabated,” said Nicholas Collins, EXA’s chief commercial officer. “We are proud to offer the fastest transatlantic fibre routes for financial exchanges between the US and the UK and will continue to listen to our customers when making strategic investments in our network to deliver additional

value that supports their growth. Market leading

latencies for trade execution means greater financial returns for our customers.” Ciaran Delaney, EXA’s chief operating officer, added, “The hybrid microwave-fibre route will see microwave technology introduced between Slough- LD4 and EXA’s Cable Landing Station in Cork, Ireland. The network build is a testament to our commitment to enhancing routes and adopting cutting- edge technologies to consistently achieve industry- leading low latencies and maximise availability.” The announcement follows a number of recent steps by EXA to expand its transatlantic offerings for customers. The addition of Dunant, Havfrue and Amitie subsea cables to its portfolio now provides customers with six separate transatlantic routes and multiple landing points between North America and Europe.

According to a new report by Dell’Oro Group, the sales of Broadband Access Equipment are expected to decline by 1% from 2023, with the first half of 2024 seeing continued weakness followed by an improved spending environment in the second half of the year. Ongoing subsidisation efforts, the shift from copper to fibre, and the rollout of cable distributed access architectures will all propel the Broadband Equipment market from 2025 on. The Broadband Access & Home Networking 5-Year January 2024 Forecast Report says that PON equipment revenue is expected to grow from US$10.8 B in 2023 to US$11.8 B in 2028, driven largely by XGS-PON deployments

in North America, EMEA, and CALA and early 50 Gbps deployments in China. Revenue for Cable Distributed Access Equipment (Virtual CCAP, Remote PHY Devices, Remote MACPHY Devices, and Remote OLTs) is expected to reach US$1.3 B by 2028, as operators continue their DOCSIS 4.0 and early fibre deployments. Revenue for Fixed Wireless CPE is expected to reach US$2.5 B by 2028, led by shipments of 5G sub-6GHz and a growing number of 5G Millimetre Wave units. Additionally, revenue for Wi- Fi 7 residential routers and broadband CPE with WLAN will reach US$9.3B by 2028, as the technology is rapidly adopted by consumers and service providers alike.


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ISSUE 36 | Q1 2024


Network automation can save operators up to 81% in management costs.

According to research carried out by Nokia, in collaboration with research firm Analysys Mason, operators can expect up to 81% cost savings after deploying optical network automation for network and service lifecycle management. To quantify optical network automation’s benefits across CAPEX, OPEX and revenue generation opportunities, Nokia and Analysys Mason interviewed global operators who have deployed network operations and service automation processes with Nokia WaveSuite. WaveSuite is a complete platform that

90% savings in operational costs. This enabled a Tier-1 North American operator to improve their win rates by 5x. Nokia says optical network automation is a key enabler for network operators to maximise optimisation, efficiency, reliability and scale, as well as TCO savings and asset monetisation for revenue generation. This comes amid surges in data traffic from sources such as AR/VR, AI/ML and IoT, as well as the growing trend of more programmable optical networks. Despite this, adoption remains slow due to new challenges with increasing OPEX.

labour taken to complete service order orchestration, service fulfilment and service assurance processes; CAPEX avoidance of 26% by optimising network resources and retiring legacy network equipment; up to 10% uplift in anticipated revenue from the improved win rates, combined with an accelerated time-to-market for services and the ability to offer differentiated services through optical network slicing and network-as-a- service business models; and decreased time taken for service order fulfilment, from an average of 10 days to 24 hours, contributing to around

automates optical transport to lower costs and increase reliability and go to market faster with new services for increased revenue. Analysys Mason found the benefits of optical network automation spanned multiple areas of network and service lifecycle management, including reduced network lifecycle management operational costs by up to 56% by simplifying complex network operations tasks for shorter time to provision, configure, deploy and manage optical networks; operational cost savings

of up to 81% for service delivery by reducing the

Top firms trial hollow core fibre

Telia Lithuania taps Ciena for 800Gbps wavelength service

lyntia, Nokia, OFS|Furukawa Solutions and Digital Realty (Interxion) have successfully carried out a field trial in a real environment to demonstrate the potential of hollow core fibre technology. Prior to implementing the technology in a real environment, pilot tests were carried out in a laboratory in Paris by Nokia Bell Labs. The initial results showed a significant reduction in latency by more than 30% and a considerable decrease in non-linear effects compared to traditional optical fibre. The pilot tests in Paris demonstrated data rates of 800 Gbps and 1.2 Tbps. The results showed that hollow fibres have the potential to break through the non-linear Shannon capacity limit of solid-core fibres.

The recently completed field trial in Madrid confirms the feasibility and effectiveness of hollow core technology. The trial demonstrated a round-trip latency reduction of 4.287μs over a 1.386km link; a latency reduction of more than 30% relative to conventional single mode fibre. The capacity deployed during the field trial was 6x100Gbps on a single 600Gbps wavelength, and 10x10Gbps on a single 100Gbps wavelength. lyntia’s strategic location in Madrid served as the starting point from which a 1.4km link was deployed to a Digital Realty (Interxion) data centre using AccuCore® HCF fibre optic cable developed by OFS| Furukawa Solutions. In addition, Nokia provided the transmission equipment and field and lab testing.

additional Ciena optical and network management solutions including Ciena

Telia Lithuania, a Telia Company subsidiary, is deploying Ciena’s WaveLogic 5 Extreme

6500 packet-optical platform powered by

(WL5e) coherent optics to upgrade its countrywide network to support 400G and higher services and deploy the first 800Gbps wavelength service between major cities in Lithuania. With this deployment, Telia Lithuania

WL5e and WaveLogic Ai programmable coherent optics Ciena says the upgrade will mean increased capacity, network reach, and power efficiency; faster wavelength restoration with the 6500’s flexible photonics and intelligent Layer 0 control plane; quicker issue resolution and improved timing distribution for applications requiring highly reliable synchronisation; and simpler service deployment and network operations with Navigator Network Control Suite (Navigator NCS).

says it will be able to deliver more flexible,

higher-capacity, and cost- effective transport services with the resiliency and power efficiency required by 5G, Internet of Things (IoT), and other bandwidth- intensive applications. Telia Lithuania’s new network will also utilise


| ISSUE 36 | Q1 2024


ZOONA Closure For today‘s hybrid fibre optical access networks

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ISSUE 36 | Q1 2024


Carrier meets bandwidth challenge with investment HYPERSCALER GROWTH DRIVES EXA EXPANSION PLANS

The proliferation of hyperscale datacentres is now a fact of life for the fibre optic communications industry, as is the commensurate rise in demand for national and international bandwidth. Optical Connections editor Peter Dykes , spoke with Steve Roberts , SVP, Strategic Investments and Product Management at EXA Infrastructure, a leading international wholesale carrier, about how the company is meeting the bandwidth challenge through investment and network expansion.

EXA’s network is massive. Does the company own the entire network?

or one of the other large DC providers planning to open a new site in a city or a country, for example, that’s a pretty good invitation to us. It’s somewhere we ought to be going to because they spend a lot of time on their research, deciding which markets to go into. Also, subsea cables are a big driver of our demand. When we hear rumours about new subsea cables being built, again, that’s a trigger for us to think should we be building to that particular location. For the other 50% of our projects, what we call anchored investments, and that’s where a hyperscaler might say they want to buy a lot of capacity between two particular cities, and want us to build it, so it’s a mixture of approaches. With regard to EXA’s fibre strategy, particularly for subsea cables, do you see microfiber as a solution for increasing capacity, or are you relying more on developments in optics and photonic technologies? PD

comes along with a new generation of optics, which is going to be cheaper, lower cost per bit and lower power, and you have to do it all again. We’re using the current generation of Infinera technology which gets us between 25Tbps and 30Tbps per fibre pair in the in the C band. We expect to be able to push that to 40Tbps or 45Tbps, as subsequent releases of technology come out, but then we’re getting ever closer to the Shannon limit.


The total footprint of what’s in existence and what is currently in build is 151,000 kilometres. Of that,


about 30,000 kilometres is our own duct and cable and the rest is fibre pairs on third-party terrestrial or submarine cables, which means we can offer 100 gigabit and 400 gigabit wavelengths across pretty much the entire footprint, along with spectrum services. PD What is your strategy for strategic investment? Do you connect PoPs and then market to the various companies that are likely to use them, or do you look for geographies where demand is likely to grow in the future? SR It’s a bit of both. When EXA was launched in September 2021, our network was 115,000 kilometres at that point. That had been built up over the last 23 years, starting with Interoute in Europe, and Hibernia, which were two of the companies that came together via GTT to form EXA, so it’s a network that has grown over time. In recent times, particularly in the two years since we’ve been under I Squared ownership, we’ve committed to date €286 million of investment and network expansion. And that’s pretty much a 50-50 split between what we would call anchored investments, and speculative investments. Think of speculative as “build it, and they will come”, though about half of what we do is driven by watching industry trends and seeing where our customers are planning to build data centres. If we see Equinix,

Are you thinking of exploiting other bands such as the L- band?


Where we have our own fibre and are fibre-rich, we typically run in the C-band, but where we’re using


expensive third-party fibres, we want to really get as many terabits as we can, so that’s where we run L-band in some routes. I think the challenge has always been that L-band has always been more expensive, and requires retrofitting, but if you haven’t built for L-band already, you have to go back to all the intermediate amplifiers, retrofit the splitters and add an L-band amplifier as well. It makes sense, but the focus at the moment is extended C-band or Super C- band, which squeezes about another 20% out of the C band spectrum. Our expectation is that photonics will plateau when the Shannon limit is reached, then the alternatives are multi core fibre for higher density, or perhaps spatial division multiplexing, or something like hollow core fibre which will eventually become commercially and technically viable. At that point however, there will need to be another evolution in the electronics to use the wider bandwidth offered by hollow core.

Again, I’d say it’s a combination of both. The original Interoute network was built over 20 years


ago largely using 96 fibre cables. Now, when we’re installing new cables, the minimum would be round about 288 fibres, and we are now starting to use micro cables and micro ducts. So, in the space where we used to just be able to get a 96-fibre cable, we can now fit multiple 288-fibre cables, thereby increasing density. But with optical equipment, it’s almost a continuous exercise of having to upgrade the photonics. You roll out a new generation of technology which takes several years to upgrade the entire network, then a company like Infinera


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Talking about capacity leads us to how generative AI is driving demand. Is this an issue for you? AI is a real trend that really does create demand in our in our industry and is here to stay,

the hyperscalers and some have said they expect the impact of AI to be a five to 10 times increase in capacity between their core data centres, and that they are in the process of very quickly looking to procure more capacity between their datacentres, and we’re talking many, many pairs of fibres between centres. What I’m also hearing is we’re very much on the back end of this in Europe, and the US is a year or so ahead, so actually, the impact in the US is far more significant than anything we’ve yet seen in Europe.



hopefully for good reasons. Everyone is talking about it, but what does it actually mean for us? I think for lots of companies that build and operate datacentres, it’s more impactful than for the telecom operators right now, particularly when there is a need for megawatt datacentres with 100 kilowatts per rack, just for training AI large language models. That doesn’t seem to be driving a lot of increase in telecoms bandwidth requirements, because our understanding is that the training is done once, in one place. That takes a long time to do but once the model is launched, it switches to inference. We are however seeing more demand for services to the Nordics, from startup companies or ones that have only been around for about a year, where a lot of AI workloads are going, because it’s cold and you get a better PUE [Power Usage Effectiveness] when you’ve got a low ambient temperature. But I think it’s also because energy is cheap in the Nordics, and is generally very green, if not 100% renewable. The uptick in capacity in the Nordics is not in itself transformational, however. For us, what is interesting is that we deal with

Steve Roberts, SVP Strategic Investments & Product Management, EXA Infrastructure.

What is your strategy going forward?


our radar. There’s a lot of datacentres being built in Atlanta right now, some of which are fuelled by AI, and some by hyperscale. We also think there’s need for more diversity across the Atlantic, so there make possibly be another trans- Atlantic cable in the future. In Europe, you may well see us making some additional investments heading East and Southeast, certainly extending further across the Mediterranean. We’re not planning to enter the Middle East or North Africa, but we probably do want to explore how we can take a bit more demand from there. So, for example, creating a PoP in Egypt, to take some subsea traffic that’s landing there or traffic that’s coming from Africa.

SR I think our strategy has really been over the last couple of years has been catch up. We’ve been a little bit under invested when we were under previous ownership, and I think some of the other private equity owned companies had invested more than we had. So now we have 37,000 kilometres in construction, and we’ve been looking at infilling areas where we were a little bit weak, but we’re also looking at what we believe the next growth areas are, and what are the adjacent geographies we can connect to that will help drive more traffic onto our network. We’re focused a lot on Southern Europe and trans-Atlantic markets, but we will be expanding further west and south in the US but not into Latin America. I certainly I think Miami and Atlanta would be on

Thank you.


EXA Infrastructure network Image: EXA



ISSUE 36 | Q1 2024


Optical network automation delivers the goods

Analysys Mason & Nokia study shows automation can save operators up to 81% in network and service management costs

D o you remember when all freight trains had cabooses (or brake vans for the European readers)? The little red car at the back of the train carried the conductor, who was responsible for issues like wheel defects or dragging equipment that would affect safe and timely operations. They were phased out in the 1980s when railroads installed track-side equipment to automatically detect those issues, allowing for the trains to be run more efficiently. A similar transition is happening in transport optical networks. Automation is incorporating new technologies like artificial intelligence (AI) and machine learning (ML) to make it easier to run the networks more efficiently and with less human intervention. But like a train, it’s taking a while for the new

in which the optical transport network could save you time and money by managing itself. One in which the network, for example: • can detect events in the network such a line cut, locate them precisely and proactively reroute traffic and notify a repair crew to restore the connection • has a complete picture of all its network elements, sees where capacity limits are being reached and proactively begins the planning process to add scale • can take over configuration processes and add new devices or services with little to no human intervention (or human error) • can exchange information programmatically with BSS/OSS systems to significantly reduce the time it takes to deliver new services to customers But if you’ve been holding off on getting on board with automation until you can see the benefits are worth the effort, there’s good news: The evidence is in and it’s extremely positive. Nokia recently worked with the research firm Analysys Mason to quantify the real-world benefits of our optical network automation. A variety of Tier 1 network operators around the globe were interviewed to better understand how they operated their networks before introducing automation, and how that changed after they deployed automation in terms of CAPEX, OPEX and time to market for network management tasks and service delivery.

technology to get up to speed because automation represents a fundamental transformation to how network operators plan, commission, provision, analyze and optimize their networks. And like our freight train infrastructure, the importance – and complexity – of transport optical networks is only growing as we ask more and more from them— connect to more devices, carry data for more applications, provide ultra-low latency and highly reliable connectivity to support specific use cases, address new markets to expand revenue, and do it all at higher speeds. Emerging technologies such as AI, ML, edge computing, Internet of Things (IoT), smart cities or autonomous vehicles can’t succeed without robust and efficient optical transport.

This is where automation can really make a difference, by helping to create a world

WaveSuite Quantifying the benefits of optical network automation The study

The results were compelling. Here are some of the high-level findings:

• Automating network lifecycle management processes led to OPEX savings of up to 56 percent through simpler network operations that made it faster and easier to deploy, configure and manage optical networks.


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time to market and higher revenue. Get on board now and arrive at the land of automation benefits sooner or be forced to compete at a significant disadvantage with those who’ve already invested.

• Automating service virtualization reduced OPEX up to 81 percent by reducing the labor required to complete service order fulfilment and service assurance processes. • Automating network planning for both planned and deployed networks optimizes network resources and enables legacy network equipment to be retired, which contributes to CAPEX avoidance of up to 30%. • Operators expect automation to provide up to 10 percent uplift in revenue from improved win rates, faster time to market for services, the ability to offer differentiated services through optical network virtualization and the inclusion of network-as-a-service business models. The network operators interviewed also revealed secondary benefits of adopting network automation: • Consolidating IP and optical processes into a single integrated system helped reduce the costs associated with manual processing and software integration between different systems • Hardware cost can be reduced through more efficient network designs, helping reduce network CAPEX for some services by up to 30 percent. • Integrating new third-party applications into a single planning and optimization platform can reduce the number of applications required to run the network, along with associated costs. One operator achieved a 30 percent CAPEX savings by retiring the middleware software it used for integration and connecting WaveSuite to other operations support systems (OSSs). • Automation enabled one operator to offer more stringent network service- level agreements (SLAs) and use enhanced monitoring to reduce SLA violations, leading to fewer service outages and lower operational cost. • Automation improved average service order fulfillment time from ten days to 24 hours, contributing to 90 percent savings in operational costs. This enabled a Tier-1 North American operator to improve its win rates by a factor of five. If you’ve been sitting on the fence about starting your optical network automation journey, this report clearly shows the time for debate is over. The automation train is leaving the station for a destination that will bring lower CAPEX and OPEX, faster

Visit the Nokia website to get the full report and learn how the features and benefits of the Nokia WaveSuite automation platform can help your transport optical network succeed well into the future.

WaveSuite Simplify your optical network with automation

WaveSuite Scan the QR code to find out how optical network automation can benefit you



ISSUE 36 | Q1 2024



Semiconductors are strategic. According to the Semiconductor Industry Association, total global chip sales reached US$574 billion in 2022. Furthermore, these chips are key for a wide range of huge industries, including computing (US$414 billion in 2022), automotive (US$2.9 trillion in 2022), communications (US$1.8 trillion in 2022), and consumer electronics (US$723 billion in 2022). Semiconductors are also key for many industries of the future, such as artificial intelligence, quantum computing, clean technology, and robotics, writes Paul Momtahan ,

Solutions Marketing Director at Infinera. G overnments around the world now recognise the strategic importance of the ability to design and manufacture semiconductors domestically, including securing the supply of key manufacturing equipment and Examples of government recognition and action include the US CHIPS and Science Act and the European Chips Act. The US CHIPS (Creating Helpful Incentives to Produce Semiconductors) and Science

electronics and computing. While silicon- based semiconductors are clearly strategic, compound semiconductors, combining two or more elements, and in particular the photonic products they enable, are equally strategic in the modern world. Photonic technology obviously plays a critical role in optical communications, enabling tens of terabits per second to be transmitted over the submarine and long-haul terrestrial fibres that provide the backbone for the internet, while also facilitating high-speed metro, mobile backhaul, and broadband access networks. It also enables the hyperscale data centres from Google, Meta, Amazon, and Microsoft, delivering scalable communications between servers and switches. It even has a role to play in the future of space communications. These metro, long haul and submarine networks are powered by coherent optical engine technology. As shown in Figure 1, coherent optical engines include a number of components and functions. First, we have the digital ASIC which provides the digital signal processing (DSP), digital-to-

Act supports domestic semiconductor production in the United States through legislation and financial support to the value of US$52 billion. This US$52 billion comprises US$39 billion in subsidies for chip manufacturing and US$13 billion for semiconductor research and workforce training. The act was passed by Congress in July 2022 and signed into law by President Joe Biden in August 2022. Following the approval by the European Parliament and Council, the European Chips Act entered into force on September 21, 2023. The aim of this legislation is to increase the European percentage of semiconductor production from less than 10% to at least 20% with the aid of a €43 billion investment. However, when many people hear of semiconductors and chips, they naturally think of the silicon-based semiconductors that manipulate electrons for digital

materials. This importance was highlighted by the COVID-19 pandemic, when entire industries were hampered by a lack of critical semiconductors, and by recent geopolitical tensions and the ongoing threat of supply chain disruption resulting from new or increased tensions. In addition to mitigating supply chain disruption risks, benefits of domestically manufactured semiconductors include high-value jobs, faster innovation, GDP growth, and increased tax revenue. The semiconductor industry, and industries it enables such as artificial intelligence, are also strategically important for national security, with applications including defence technology and preventing cyber threats, including cyber espionage and cyber warfare.

Figure 1: Coherent optical engine high-level building blocks


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optical communications. Gallium arsenide also provides VCSEL arrays for 3D sensing in devices such as smartphones, smartwatches, and VR headsets, and in automotive applications such as in- cabin sensing and LiDAR. Additional gallium arsenide applications include gas sensing, biomedical sensing, and computer mice. Indium phosphide PICs also have a wide range of emerging and potential applications. These include defence, automotive LiDAR, 3D sensing for wearables and cell phones, solar cells, and medical sensing. Indium phosphide PICs could also have a role in quantum computing and in neuromorphic computing for artificial intelligence and machine learning. For example, Eindhoven University of Technology demonstrated an indium phosphide photonic neuromorphic PIC in 2020. Compound semiconductors even have an evolving role to play in electronic applications. Indium phosphide and

Furthermore, as silicon photonics modulators are unlikely to be efficient in enabling symbol rates much beyond 120 to 140 Gbaud, future generations of coherent optical engines at 1.6 Tbps per wavelength and beyond will be dependent on compound semiconductor modulators, with indium phosphide and thin-film lithium niobate (LiNbO3) the leading candidates. In addition, indium phosphide can detect DWDM light, so can also be used for the photodetectors, though germanium can also provide this function in silicon photonics. Indium phosphide uniquely enables all these photonic functions to be integrated into a single photonic integrated circuit (PIC) in contrast to the photonics for early coherent optical engines that comprised of hundreds of discrete components connected with coupling optics, which resulted in bulky and expensive devices with a less than optimal mean time between failure (MTBF).

analogue converter (DAC) and analogue- to-digital converter (ADC) and additional functions such as forward error correction (FEC), framing, multiplexing, encryption, and performance monitoring. The digital ASIC, often referred to as simply the DSP, is made of silicon leveraging the same state-of-the- art CMOS process node technologies (ie 7nm, 5nm, 3nm) used in premium smart phones and the latest high-end computing, graphics and artificial intelligence chips. Next, an analogue ASIC integrates multiple drivers and transimpedance amplifiers (TIAs). The drivers take the low voltages from the DAC and convert them to the higher voltages required by the modulator. In the receive direction, the TIAs take the currents from the photodetectors and convert them to the voltages required by the ADC. The analogue ASIC is typically made from silicon germanium (SiGe). And finally, we have the photonics. This includes the laser that generates the light with the desired frequency/wavelength. Then we have the modulator that takes the light from the laser, and by changing the phase and amplitude, encodes the data. It does this by using an electric field to change the refractive index of the material the light is passing through. The coherent modulator itself includes four individual Mach-Zehnder modulators (MZMs) in addition to splitters, combiners, phase shifters, a polarisation rotator, and a polarisation beam combiner. Then on the receive side we have the photodetectors and passive photonics including a polarisation beam splitter and 90° hybrid. Some coherent optical engines may also include an optical amplifier to boost the power of the signal and a tuneable optical filter (TOF) to minimise any out-of-band noise resulting from this amplification. Only the compound semiconductor indium phosphide can provide laser and optical amplification functions at DWDM frequencies, so some amount of indium phosphide will always be required in all coherent optical engines. Silicon cannot perform these functions as it is an indirect bandgap semiconductor, meaning that excited electrons produce heat, not light. Indium phosphide also has an inherently superior modulation effect compared to silicon. This enables more bandwidth (GHz), higher symbol rates (Gbaud), and higher date rates (Gbps), thus reducing cost and power consumption. This performance advantage is especially important for the highest- performance embedded segment of the coherent optical engine market. Indium phosphide modulators also require less voltage and length for a given phase change compared to silicon, resulting in lower power consumption and more compact devices, which can especially be an advantage for coherent pluggables.

Figure 2- Compound Semiconductor Applications

gallium arsenide are already used today for some niche applications such as high-radio-frequency electronics for mobile communications. However, as we reach the limits on shrinking silicon chip geometry, the industry is also looking at compound semiconductors, with their higher electron mobility and superior temperature stability, as potential successors. Silicon carbide (SiC) and gallium nitride (GaN) are the primary compound semiconductor R&D candidates for succeeding silicon as the mainstream semiconductor material. So, to summarise, in addition to silicon, domestic production of compound semiconductors including indium phosphide should also be considered a strategic imperative. Furthermore, indium phosphide PIC fabrication is a scarcer resource, and domestic production of key supply inputs such as indium phosphide wafers also needs to be considered. Infinera applauds the passage of the CHIPS and Science Act and the equivalent European legislation, which will help compound semiconductor manufacturers such as Infinera to expand domestic production of indium phosphide PICs and boost US and European countries’ global competitiveness.

As is the case with conventional electronics, with advanced fabrication and integration capabilities in production, manufacturing one PIC is far more cost- effective than manufacturing individual optical components and then integrating and packaging them. PICs also have a dramatic impact on footprint, enabling the miniaturisation of optical devices. Power consumption is also reduced, while performance can be improved due to minimised optical coupling losses when connecting optical functions with waveguides inside the PIC, as opposed to coupling optics between discrete components. And equipment failures are reduced, as these coupling optics are eliminated as a source of failure. These benefits have enabled indium phosphide PICs to play a key role in evolving coherent optical engines, with potential future applications inside the data centre including coherent lite and linear drive optics. Another compound semiconductor, gallium arsenide (GaAs), provides the vertical-cavity surface-emitting lasers (VCSELs) and photodetectors for short- reach optics over multi-mode fibre at 850 nm. Compound semiconductors also have important applications beyond



ISSUE 36 | Q1 2024


Amidst the surge of fibre to the home/building (FTTx) across the European Union’s 39 member states (EU39), Fujikura Europe stands at the forefront of delivering high speed customer connections. The landscape is transforming rapidly, with the total number of homes passed reaching a staggering 219 million in September 2022, reflecting a remarkable year-over-year growth. CONNECTIVITY EXCELLENCE: FUJIKURA’S ROLE IN EUROPE’S FIBRE REVOLUTION

centric design, providing efficient solutions for the growing demand in high-speed connectivity. It not only enhances operational efficiency but also sets new standards for ease of use and performance in cladding alignment splicers.” Yuji Ohba, Sales Director at Fujikura Europe, sheds light on the company’s instrumental role in conquering the challenges of the access network. He emphasises, “At Fujikura, we recognise the critical nature of this phase and through a progressive, technology-led approach, we’re enabling telcos throughout the UK to keep pace with customer demand and government aims for ultra-fast broadband coverage. We know what it takes to speed up FTTH deployments and reduce total cost of ownership and we invite you to discuss your network deployment goals with us at the FTTH Conference in Berlin.”

The final stretch access network of FTTH deployment holds unique challenges which are addressed by our connectivity and splicing technology. Existing infrastructure, physical structures, access, congestion at the point of distribution and cost (particularly in rural areas) all contribute to the complexity of connecting customers. Our connectivity portfolio, which includes termination and distribution boxes, demarcation, and customer outlets, eases this stage. The 45S clad alignment splicer serves as a catalyst to help overcome the hurdles of last mile and customer connections. The 45S fusion splicer embodies Fujikura’s dedication to innovation, delivering up to a 30% reduction in operational cycle time. Neil Bessant, Divisional Manager of the Fusion Splicer Division, explains, “It exemplifies our commitment to innovation and user-

Key countries like the United Kingdom, France, Turkey, and Italy are setting the pace, contributing to the significant annual growth rates. Belgium leads with a phenomenal 60% growth rate, closely followed by the United Kingdom (+51%), Serbia (+40%), The Netherlands (+34.7%), and Greece (+34.5%). While countries like Iceland top the European FTTH/B penetration ranking, these nations are undeniably pioneers in the rapid expansion of high-speed full fibre connections, fuelled by the growing needs of the digital age. The urgency of fibre to the building and fibre to the home rollouts has become more than a necessity; it’s a fundamental requirement for the functioning of modern society. Businesses are moving critical operations to the cloud, and individuals rely on seamless connections for work, education, and leisure. We all understand that the role of ultra-fast connectivity has evolved beyond a mere convenience to an absolute necessity, driven not just by the demands of remote work but also online education, and the increasing complexity and proliferation of technologies like artificial intelligence. Thanks to a culture of innovation and engineering excellence, Fujikura Europe is playing a key role in the acceleration of full fibre rollout across the United Kingdom. Our innovative Wrapping Tube Cable with SpiderWeb Ribbon fibre is a technology that brings multiple benefits for service providers. Notably, because of a design which enables a high fibre density and small diameter cables, using our cables means getting more fibre into the available duct space – maximising value and reducing the need for civil works. WTC with SWR is easy to work with because it’s gel-free and has easily identifiable fibre bundles, which when used with the Fujikura 90R mass fusion splicer makes deployments faster and simpler.



ISSUE 36 | Q1 2024


Fixes For Looming Optical Network Traffic Jams? BATTLE OF THE BANDS

As is widely reported, the amount of traffic carried over the world’s optical fibre networks has been growing on some routes at a prodigious rate in recent years, and the expectation is that the volumes involved should only get larger in the future. In that eventuality it’s likely that the development and introduction of effective measures to circumvent conceivable optical system traffic jams will become more commonplace, writes veteran tech journalist John Williamson .

NOT A WALK IN THE PARK However, the use of L-band and

the only extant C- and L- band subsea system is Pacific Light Cable Network. There could be others in the pipeline, but Howard Kidorf, Managing Partner at Pioneer Consulting, reasons that C+L, is not the preferred method of the undersea system suppliers for increasing the capacity of an undersea cable. “Space- Division Multiplexing (SDM) – i.e. just more fibre and amplifiers - and to a lesser extent multi-core fibre (MCF), are preferred as the engineering is more straightforward and by some metrics, the capacity is greater,” reckons Kidorf.” Putting more fibre in the cable is a relatively small additional cost to a cable.” TERRA IS FIRMER, THOUGH The C- and L-band pairing picture is somewhat different in the long-haul terrestrial cable sector. As described by Brown, many of his company’s Communications Service Provider (CSP) customers are utilising spectrum-based C+L-band DWDM solutions in terrestrial networks to effectively double the capacity per fibre pair and avoid the cost of leasing additional fibre pairs. “Although commercial C+L-band solutions have existed for several years, the recent availability of more highly integrated and application-optimised line system solutions has enabled a broader adoption of C+L in metro and long-haul networks by CSPs (and) cable operators, as well as enterprises,” adds Brown.

Daryl Inniss, optical fibre and device expert with a focus on commercialising technologies, says that, on the fibre side, there is industry debate on how to support traffic growth at some 30% per year. Inter alia, Inniss sits on the European Conference on Optical Communications (ECOC) Market Focus Committee. Fleshing traffic volumes out, and citing his own company’s ‘Global Network Traffic 2030’ report, Dave Brown, Senior Product Marketing Manager, Line Systems, Nokia Optical Networks, says overall global network traffic demand is expected to reach between 2,443 to 3,109 Exabytes per month in 2030. This is around 100 times the total monthly Internet traffic generated in 2012 WAVELENGTH COMBINATIONS? One possible capacity augmentation strategy is to use different or additional wavelengths to the C-band. “The thought is by 2030 the industry will need more bandwidth per fibre; higher transmission rate in the C-band is not sufficient,” judges Inniss. Referring to potential C- and L-band combinations, he observes that transmission lines have to be provisioned with hardware to accept both C- and L-band transponders. “While the line may not use L-band today, the necessary hardware is going in so that it is easy to increase capacity,” Inniss contends. The C-band currently dominates DWM systems in the trans-national submarine cable arena. But it’s reported that, so far,

combination C- and L-band frequencies isn’t necessarily a slam dunk. “For better or worse now there’s been a huge amount of investment within the C-band. And like with any technology, you get economies of scale. So you now have extremely cost effective solutions within the C- band,” admits Rob Shore, Senior Vice President of Marketing at Infinera. “L-band is much, much less utilised because you need a completely different type of amplifier to amplify frequencies in that range.” Kidorf points out that the L-band is not disadvantageous, per se, but the need to manage C-band and L-Band introduces additional design constraints on equalisation, cross-talk, fibre testing and many other areas. “Even after this work, the separate L-band amplifier in the repeater still requires space and electrical power,” he comments. .”L-band amplifiers are not the most straightforward way to maximise the number of Terabits transmitted per Watts of electrical power.” Kidorf clarifies that these caveats apply to both submarine and terrestrial to some extent, but are a much larger issue with submarine due to the limitations on space and deployment complexity. The considerations for terrestrial application are extremely small by comparison. Cost and earnings are, of course, pivotal considerations in shaping which proposed capacity enhancement


| ISSUE 36 | Q1 2024



the baud rate (bit rate per symbol on the modulation constellation) and realise a trade-off in link capacity versus span length. “By adjusting the baud rate in fine increments, roughly around 0.1 Gbaud, system flexibility increases to operate at a desirable span length for a given capacity, and within a desired optical channel plan,” he offers. “In subsea cable systems, this allows the operator to increase the number of deployed channels (and the resulting total lit capacity), increase system link margins, or reduce the number of operating optical transponders.” Infinera’s Shore is a supporter of turning up additional fibres in parallel. “Rather than a single pair of fibres between two locations where you expend a lot of energy to maximise the capacity of that single fibre pair, you use multiple fibre pairs between locations,” he asserts. ”This enables network operators to focus more on using cost and power efficient solutions.” Shore reasons that with this approach, spectrum becomes a much lower premium. “The value of spectrum is lower enabling people to better leverage much more cost-effective optical engines that maybe aren’t as spectrally efficient.” This, he believes, paves the way for increased use of pluggable coherent optical engines. “This class of optical engines are extremely cost effective, and extremely power efficient, but are generally quite a bit less spectrally efficient.” He likens the difference between pluggables and the embedded optical engines historically designed to maximise spectral efficiency as the difference between thumb drives and computer hard drives. WHAT IS MORE? There’s a spectrum of opinion about what’s next in terms of how to head off potential optical cable capacity short-falls. Janson believes the trends

to consider are the development of advanced fibre cables, including issues surrounding inherent fibre impairments and practical, physical limitations of SDM. “It is also worth watching future developments in SLTE coherent detection and signal processing as they will impact the capacity capabilities of future systems.” Inniss predicts that it’s likely that operators serving different market segments will, at different times, adopt different capacity boosting solutions for these segments. “Thinner fibre and MCF, for example, will go into subsea first,” he calculates. According to Kidorf, one trend is to reduce the power and space required for undersea amplifiers and to increase the electrical power-carrying capability of the cable. “I also look forward to an increased eco-system for multi-core components (a multi-core amplifier?) so that N-core fibre does not require N independent amplifiers in the repeater,”

mechanisms will be viable and which won’t. Here it’s worth repeating the remarks of Kidorf that, despite 30% (or more) growth rate of required capacity on some subsea routes, this is accompanied by a decline in the price charged for capacity. “There is not a fantastic growth rate in the total money exchanged for undersea traffic, but, for now, we are getting more Gbit/s for the same money.” At the same time, C- and L-band may not always be friendly neighbours. “There are some interplays that happen when you try to put C- and L-bands on the same fibre where the C-band signals actually lose power to the L-band signals. You get this kind of Raman effect where the L-band signals steal power from the C-band” notes Shore. It’s also the case that C- and L-bands are not the only available wavelengths in town. Inniss says that the S-, E-, O- and U-bands are being assessed to understand the challenges. “WDM can scale beyond the C and L-bands,” he acknowledges.” But, again, there are downsides here. “Cost is a big challenge,” allows Inniss. “Transponders, amplifiers, and ROADMs are needed for other bands. They are not readily available today.” OTHER ROUTES OUT OF OPTICAL GRID-LOCK A number of other avenues aimed at side-stepping would-be optical cable capacity log jams are being implemented or explored. As well as the SDM and multicore fibre instanced by Kidorf, one of Nokia’s takes on maximising spectral utilisation in subsea transmission is what is termed ‘water filling’. As explained by Chris Janson, Senior Product Marketing Manager, Subsea Systems, Nokia Optical Networks, water filling makes very fine adjustments in link baud rate to optimise spectral efficiency, line capacity, and optical span reach. He observes that for a fixed bit rate, shaped modulation format, and FEC scheme, you can adjust

SUPERSIZING THE C-BAND Over time, the optical networking

industry has extended the capacity of C-band operations. According to Infinera literature, the deliverables of the original C-band (4 THz amplification giving 80 channels at 50 GHz spacing) were upped in Extended C-band to a flat gain of 4.8THz, giving 96 channels at 50GHz. More recently advances have been made in C-band amplifiers, extending the effective range to about 6.1 THz and offering up to 120 channels 50 GHz. These solutions typically referred to as Super C-band. “The benefit of this approach is that network operators can get 25 to 30% more capacity while still using a single set of amplifiers, filters, and ROADMs,” comments Shore. “Additionally, tuneable lasers that can now be tuned across the entire 6.1 THz of spectrum.”

Daryl Inniss Member of the ECOC Market Focus Committee

Dave Brown Senior Product Marketing Manager, Line Systems, Nokia Optical Networks

Howard Kidorf Managing Partner, Pioneer Consulting

Rob Shore Senior Vice President, Marketing, Infinera.

Chris Janson Senior Product Marketing Manager, Subsea Systems, Nokia. Optical Networks



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