Marvell's 50G PAM-4 DSP for 5G optical fronthaul
- Marvell has announced the first 50-gigabit 4-level pulse-amplitude modulation (PAM-4) physical layer (PHY) for 5G fronthaul.
- The chip completes Marvell’s comprehensive portfolio for 5G radio access network (RAN) and x-haul (fronthaul, midhaul and backhaul).
Marvell has announced what it claims is an industry-first: a 50-gigabit PHY for the 5G fronthaul market.
Dubbed the AtlasOne, the PAM-4 PHY chip also integrates the laser driver. Marvell claims this is another first: implementing the directly modulated laser (DML) driver in CMOS.
“The common thinking in the industry has been that you couldn’t do a DML driver in CMOS due to the current requirements,” says Matt Bolig, director, product marketing, optical connectivity at Marvell. “What we have shown is that we can build that into CMOS.”
Marvell, through its Inphi acquisition, says it has shipped over 100 million ICs for the radio access network (RAN) and estimates that its silicon is in networks supporting 2 billion cellular users.
“We have been in this business for 15 years,” says Peter Carson, senior director, solutions marketing at Marvell. “We consider ourselves the number one merchant RAN silicon provider.”
Inphi started shipping its Polaris PHY for 5G midhaul and backhaul markets in 2019. “We have over a million ships into 5G,” says Bolig. Now Marvell is adding its AtlasOne PHY for 5G fronthaul.
Mobile traffic
Marvell says wireless data has been growing at a compound annual growth rate (CAGR) of over 60 per cent (2015-2021). Such relentless growth is forcing operators to upgrade their radio units and networks.
Stéphane Téral, chief analyst at market research firm, LightCounting, in its latest research note on Marvell’s RAN and x-haul silicon strategy, says that while 5G rollouts are “going gangbusters” around the world, they are traditional RAN implementations.
By that Téral means 5G radio units linked to a baseband unit that hosts both the distributed unit (DU) and centralised unit (CU).
But as 5G RAN architectures evolve, the baseband unit is being disaggregated, separating the distributed unit (DU) and centralised unit (CU). This is happening because the RAN is such an integral and costly part of the network and operators want to move away from vendor lock-in and expand their marketplace options.
For RAN, this means splitting the baseband functions and standardising interfaces that previously were hidden within custom equipment. Splitting the baseband unit also allows the functionality to be virtualised and be located separately, leading to the various x-haul options.
How the RAN is being disaggregated includes virtualised RAN and Open RAN. Marvell says Open RAN is still in its infancy but is a key part of the operators’ desire to virtualise and disaggregate their networks.
“Every Open RAN operator that is doing trials or early-stage deployments is also virtualising and disaggregating,” says Carson.
RAN disaggregation is also occuring in the vertical domain: the baseband functions and how they interface to the higher layers of the network. Such vertical disaggregation is being undertaken by the likes of the ONF and the Open RAN Alliance.
The disaggregated RAN – a mixture of the radio, DU and CU units – can still be located at a common site but more likely will be spread across locations.
Fronthaul is used to link the radio unit and DU when they are at separate locations. In turn, the DU and CU may also be at separate locations with the CU implemented in software running on servers deep within the network. Separating the DU and the CU is leading to the emergence of a new link: midhaul, says Téral.
Fronthaul speeds
Marvell says that the first 5G radio deployments use 8 transmitter/ 8 receiver (8T/8R) multiple-input multiple-output (MIMO) systems.
MIMO is a signal processing technique for beamforming, allowing operators to localise the capacity offered to users. An operator may use tens of megahertz of radio spectrum in such a configuration with the result that the radio unit traffic requires a 10Gbps front-haul link to the DU.
Leading operators are now deploying 100MHz of radio spectrum and massive MIMO – up to 32T/32R. Such a deployment requires 25Gbps fronthaul links.
“What we are seeing now is those leading operators, starting in the Asia Pacific, while the US operators have spectrum footprints at 3GHz and soon 5-6GHz, using 200MHz instantaneous bandwidth on the radio unit,” says Carson.
Here, an even higher-order 64T/64R massive MIMO will be used, driving the need for 50Gbps fronthaul links. Samsung has demonstrated the use of 64T/64R MIMO, enabling up to 16 spatial layers and boosting capacity by 7x.
“Not only do you have wider bandwidth, but you also have this capacity boost from spatial layering which carriers need in the ‘hot zones’ of their networks,” says Carson. “This is driving the need for 50-gigabit fronthaul.”
AtlasOne PHY
Marvell says its AtlasOne PAM-4 PHY chip for fronthaul supports an industrial temperature range and reduces power consumption by a quarter compared to its older PHYs. The power-saving is achieved by optimising the PHY’s digital signal processor and by integrating the DML driver.
Earlier this year Marvell announced its 50G PAM-4 Atlas quad-PHY design for the data centre. The AtlasOne uses the same architecture but differs in that it is integrated into a package for telecom and integrates the DML driver but not the trans-impedance amplifier (TIA).
“In a data centre module, you typically have the TIA and the photo-detector close to the PHY chip; in telecom, the photo-detector has to go into a ROSA (receiver optical sub-assembly),” says Bolig. “And since the photo-detector is in the ROSA, the TIA ends up having to be in the ROSA as well.”
The AtlasOne also supports 10-gigabit and 25-gigabit modes. Not all lines will need 50 gigabits but deploying the PHY future-proofs the link.
The device will start going into modules in early 2022 followed by field trials starting in the summer. Marvell expects the 50G fronthaul market to start in 2023.
RAN and x-haul IC portfolio
One of the challenges of virtualising the RAN is doing the layer one processing and this requires significant computation, more than can be handled in software running on a general-purpose processor.
Marvell supplies two chips for this purpose: the Octeon Fusion and the Octeon 10 data processing unit (DPU) that provides programmability and as well as specialised hardware accelerator blocks needed for 4G and 5G. “You just can’t deploy 4G or 5G on a software-only architecture,” says Carson.
As well as these two ICs and its PHY families for the various x-haul links, Marvell also has a coherent DSP family for backhaul (see diagram). Indeed, LightCounting’s Téral notes how Marvell has all the key components for an all-RAN 5G architecture.
Marvell also offers a 5G virtual RAN (VRAN) DU card that uses the OcteonFusion IC and says it already has five design wins with major cloud and OEM customers.
Lumentum bulks up with NeoPhotonics buy
Lumentum is to acquire fellow component and module specialist, NeoPhotonics, for $918 million.
The deal will expand Lumentum’s optical transmission product line, broadening its component portfolio and boosting its high-end coherent line-side product offerings.
Gaining NeoPhotonics’ 400-gigabit coherent offerings will enable Lumentum to better compete with Cisco and Marvell. Lumentum will also gain a talented team of photonics experts as it looks to address new opportunities.
Alan Lowe, Lumentum’s president and CEO, stressed the importance of this collective optical expertise.
Speaking on the call announcing the agreement, Lowe said the expanded know-how would benefit Lumentum’s traditional markets and accelerate its entrance into other, newer markets.
Transaction details
Lumentum will pay $16 in cash for each share of NeoPhotonics, valuing the company at $918 million. Lumentum will also pay $50 million to NeoPhotonics “for growth capex and working capital.”
Cost savings of $50 million in annual run-rate are expected within two years of the deal closing, with 60 per cent of the savings coming from the cost of goods sold.
The deal is reminiscent of Lumentum’s acquisition of Oclaro for $1.8 billion in 2018. Oclaro was also focussed on transmission components and modules.
The acquisition is expected to close in the second half of 2022, subject to the approval of NeoPhotonics’ stockholders and regulatory bodies.
Background
Lumentum’s announcement follows its failed bid early this year for the laser company, Coherent. II-VI ended up winning the bid, paying $6.9 billion.
Coherent’s lasers are used in many markets and the deal would have diversified Lumentum’s business beyond communications and smartphones.
Now, the proposed acquisition of NeoPhotonics boosts Lumentum’s core communications business unit. NeoPhotonics’ focus is cloud and networking although the company has been using its coherent expertise to address LiDAR and medical markets.
Vladimir Kozlov, CEO of market research firm LightCounting, does not see any inconsistency in Lumentum’s strategy to first diversify and then strengthen its core business. “There are many directions to accelerate company growth,” he says.
Lumentum tried one way with Coherent, it didn’t work out, now it is trying another with NeoPhotonics. “You take opportunities as they come along,” says Kozlov.
NeoPhotonics has also been impacted by the trade restrictions on Huawei, a significant customer of the company. NeoPhotonics has had to adapt to on-off sales to Huawei in recent years. Huawei also has a long-term strategy to develop its optical components including tunable lasers for which NeoPhotonics has been their leading supplier.
“That certainly added pressure on NeoPhotonics to be acquired,” says Kozlov.
Business opportunities
Lumentum’s business is split 60 per cent cloud and networking and 40 per cent 3D Sensing, LiDAR, and commercial lasers for industrial applications.
Lumentum’s cloud and networking products include reconfigurable optical add-drop multiplexing (ROADM) sub-systems, optical components for high-speed client-side and line-side modules, and coherent optical modules.
NeoPhotonics brings ultra narrow-linewidth tunable lasers, silicon photonics-based components and transceivers, and high-speed coherent modules and components. NeoPhotonics also has passive and planar lightwave circuit components and an RF chip design capability using gallium arsenide and silicon germanium.
Tim Jenks, president, CEO and chairman of NeoPhotonics, said combining the two firms would accelerate its business developing high-speed optical communications.
In turn, their combined R&D and technology teams can address new markets such as the life sciences, industrial applications, and green markets such as energy efficiency, electric vehicles and climate change green manufacturing concerns.
But no detail was forthcoming on the call beyond Lowe saying the merger will expand the collective know-how and accelerate its entrance into these markets.
Lowe also highlighted the strong growth in high-speed ports due to the 30 per cent year-on-year growth in internet bandwidth.
LightCounting says the dense wavelength division multiplexing (DWDM) coherent market will experience a compound annual growth rate (CAGR) of 20 per cent over the next five years; the general optical market is growing at a 14 per cent CAGR.
Both companies have indium-phosphide components for coherent systems while NeoPhotonics has pluggable 400ZR and ZR+ products as well as silicon photonics components for coherent. Gaining NeoPhotonics’ ultra-narrow linewidth lasers will make Lumentum an even stronger laser supplier.
LightCounting’s Kozlov notes the importance of scale, especially when target markets are not huge and the number of large customers is limited. This is the case with 400ZR/ ZR+ coherent DWDM transceivers that NeoPhotonics started selling in 2021.
Amazon is the biggest buyer of such modules and it uses three suppliers. NeoPhotonics is a distant third in the race behind Acacia, now part of Cisco, and Inphi, part of Marvell. But unlike Acacia and Inphi, NeoPhotonics does not have its own coherent DSP.
Joining forces with Lumentum, NeoPhotonics is more likely to win a larger share of business at key customers, says LightCounting. The new Lumentum may still be third in the race, but it is no longer a distant third.
Recent announcements
Lumentum started shipping its 400-gigabit CFP2-DCO coherent module earlier this year. Its range of indium-phosphide coherent components operates at a 96-gigabaud (GBd) symbol rate that supports up to 800-gigabit wavelengths. Lumentum is developing components that will operate at 128GBd.
Lumentum also has a directly modulated laser (DML) supporting 100-gigabit wavelengths. Such a laser is used for 100-gigabit and 400-gigabit client-side pluggables. The company is also developing electro-absorption modulated laser (EML) technology that supports 200 gigabits and higher performance per lane.
Meanwhile, NeoPhotonics is shipping 400ZR QSFP-DD and OSFP 400ZR coherent optical modules. NeoPhotonics also has a multi-rate CFP2-DCO module with a reach of 1,500km at 400 gigabits. And like Lumentum, the company has indium-phosphide technology that supports 130GBd coherent components.
Kozlov believes Lumentum is in a good position.
On the call announcing the deal, Lumentum also delivered its latest quarterly results. “They can hardly keep up with demand,” he says.
The issue of shortages is getting worse. This is not because the shortages themselves are getting worse but that demand is ramping faster than the shortage issue can be resolved. “It’s a good problem to have,” says Kozlov.
Industry consolidation
The Lumentum-NeoPhotonics deal follows the recent announcement of the merger of two other mature optical players such as the systems vendors: ADTRAN and ADVA.
LightCounting’s Kozlov agrees consolidation is happening among mature optical component and optical networking companies but he points out that many new optical start-ups are emerging and not just in China.
“At the telecommunications part of CIOE (China International Optoelectronic Exposition), 500 companies were exhibiting,” says Kozlov. “And with the trade barriers, there is an extra incentive for companies in the West to double down on what they have been doing and maybe new companies to be formed.”
Companies have concerns about buying stuff from overseas so local companies are getting more business.
“We are going to see more consolidation but also new vendors entering the market and competing with the bigger guys,” says Kozlov.
ADTRAN-ADVA's metro-access play
ADTRAN and ADVA have agreed to merge after a long courtship.
The two CEOs have spoken regularly over the years but several developments spurred them to act.
The merger combines ADTRAN’s expertise in access technologies with ADVA’s metro wavelength-division multiplexing (WDM) know-how to create a ‘metro-core-to-door’ company with revenues of $1.2 billion.
ADTRAN and ADVA a better path forward together than separately
As such, the merger promises to double their size and networking skills. Yet the stock market appeared underwhelmed by the announcement, with ADTRAN’s shares down 16% for the rest of the week after the deal was announced.
Market research analysts, however, are more upbeat.
“ADTRAN and ADVA have a better path forward together than separately,” said John Lively, principal analyst at LightCounting Market Research, in a research note.
The deal is expected to close in the second or third quarter of 2022 but only after several hurdles are overcome in what is described as a complex deal.
Motivation
The two companies describe the merger as a logical outcome given recent developments in the marketplace.
“Our combination will make us one of the largest Western suppliers for the markets we serve,” said Tom Stanton, CEO and chairman of ADTRAN, on the call announcing the deal. The word “Western” is noteworthy, reflecting how geopolitics is one catalyst motivating the merger.
The deal will also reposition the two companies with their rivals. ADTRAN will distance itself from broadband competitors such as Calix while ADVA will diversify its business from its current larger competitors, Ciena and Infinera. The new company’s revenues will also approach those of the two players.
The product portfolios of ADTRAN and ADVA have almost no overlap. ADTRAN offers fibre access and connectivity solutions while ADVA addresses metro WDM, data centre interconnect, business Ethernet, network synchronisation and network functions virtualisation (NFV) expertise.
Once combined, each company will seek to expand its sales in the other’s main market.
The US accounts for 74 per cent of ADTRAN’s revenues, while Europe accounts for 21 per cent. Meanwhile, Europe accounts for 62 per cent of ADVA’s business while the US is 29 per cent. The remaining revenues come from the Asia Pacific: ADTRAN, 5 per cent, and ADVA, 9 per cent.
Also cited as a factor is the wave of investment in fibre, not just by communications service providers (CSPs) and public utilities but also government-backed stimulus plans in the US and Europe.
In the US, $66 billion in investment was mentioned spread across programmes such as the infrastructure bill, the second phase of the Rural Digital Opportunity Fund (RDOF), and state-level funding for high-speed broadband.
In Europe, the sum is similar: $35 billion in government funding for high-speed broadband in the European Union, and $30 billion in public and private funding for fibre builds in the UK alone.
“There is an ongoing global fibre investment opportunity that we believe will create sustained momentum for years to come,” said Stanton.
Moreover, having access and second-mile technologies, the new company can better win business. “There is not a customer that we sell to today that, when they are upgrading their access infrastructure, is not also upgrading their middle-mile,” said Stanton.
Becoming a larger player will help, he said: “We see our customers making a significant capital investment to transition their supply chain to trusted vendors.”
Another merger catalyst is the opportunity created by US and European service providers that no longer use Chinese vendors and in some cases are replacing equipment already deployed.
In the US, this is less of an issue due to the fewer deployments while in Europe the process started 18 months ago. Stanton expects Latin America to follow.
“The market opportunity is not just created by all the stimulus but it is also because of the displacement of Eastern vendors,” said Stanton.
There is a land grab going on, he says, and the company that gets there first wins.
“Once you get entrenched in a carrier, regardless of size – the larger ones tend to have two [vendors] and the smaller ones, one – once you are entrenched, it is very difficult to get pulled out,” said Stanton.
Analysis
LightCounting’s view of the merger is positive.
Lively says the merger will not reshape the optical networking industry but it will be attractive to Tier 2 and Tier 3 CSPs that want to buy access and aggregation equipment from a single supplier.
LightCounting notes that the deal values ADVA at $931 million, 1.3x its most recent four quarters of sales.
This is a relatively low valuation: the 2015 Infinera-Transmode merger was 2.6x while the Cisco-Acacia Communications deal, which closed earlier this year, was 7.7x. Of recent deals, only the 2020 Ribbon-ECI Telecom deal was lower, at 1.2x.
LightCounting says one reason for the lower valuation could be ADVA’s port shipments; the vendor is one of the smallest dense WDM suppliers.
The merger’s impact will mostly be felt by the competitors of the existing two companies, says Lively. The new ADTRAN’s sales will be 20 per cent greater than Infinera but still a third of the size of Fiberhome and Ciena.
The importance of size is something both companies stress.
“Our industry has been consolidating and there is an underlying notion that scale matters,” says Stephan Rettenberger, senior vice president, marketing and investor relations at ADVA.
Doubling in size, the new company will be in the same bracket as Infinera while Ciena will be about 3x its size, notes Rettenberger: “The companies that we used to worry about the most are not as distant as before.”
At first glance, the merger between a US and an European company raises questions about the integration challenge. But both firms have American CEOs and both have operations in the US and Germany.
ADTRAN acquired Nokia Siemens Networks’ fixed-line broadband access unit in 2011 while ADVA more recently acquired US firms, MRV Communications and Overture.
Brian Protiva, CEO of ADVA and a co-founder of the company in 1994, is the longest-serving CEO in the optical industry. As such he will have thought long and hard about the deal.
“This business combination is not only about growing the business,” says Protiva. “These two businesses fit perfectly together to address existing market and technology requirements, and we are well-positioned to lead the transition to access and edge convergence.”
Service providers do not need separate infrastructure for business services, residential broadband, and/ or 5G xHauling, he says.
Mechanics
The proposed deal is an all-stock one with ADTRAN and ADVA combining to form ADTRAN Holdings.
Each ADVA share will be swapped for 0.8244 shares of the new company while ADTRAN shares will be exchanged on a one-for-one basis. ADTRAN shareholders will own 54 per cent of the combined company while ADVA shareholders will own 46 per cent, assuming all of the ADVA shares are swapped.
But the new holding company must first be approved by German regulators, expected to occur by November. A three-month offer period then starts during which a minimum of 70 per cent of ADVA shares must be surrendered.
Stanton will continue as CEO and chairman at the new company while ADVA’s Protiva will join as executive vice chairman.
“I’m convinced that Tom is the right person to run the combined company,” says Protiva. “He executes to plan, is well-liked by customers, and thinks very similarly to our ADVA leadership around people first and the customer experience.” Stanton is also a long-serving CEO, heading ADTRAN since 2005.
Protiva will support Stanton during the integration period and then be involved in the corporate strategic direction of ADTRAN, as a board member, using his many long-term relationships in the combined markets.
After that, Protiva says he may return to Egora, a holding company out of which ADVA was born.
ADVA’s CTO, Christoph Glingener, will retain his role with the new company. ADTRAN and ADVA will have a combined annual R&D budget of $250 million.
”The stock exchange offer needs to pass all types of regulatory groups and needs to be accepted by the ADTRAN and ADVA shareholders,” stresses Rettenberger. “There is still a long path to closing.”
Marvell’s latest acquisition: switch-chip firm Innovium
- Innovium will be Marvell’s fifth acquisition in four years
Marvell is buying switch-chip maker, Innovium, for $1.1 billion to bolster its revenues from the lucrative data centre market.
The combination of Innovium with Inphi, Marvell’s most recent $10 billion acquisition, will enable the company to co-package optics alongside the high-bandwidth, low-latency switch chips.
Marvell returns to the market to gain a scalable, low-latency architecture
“Inphi has quite a bit of experience shipping silicon photonics with the ColorZ and ColorZ II [modules],” says Nariman Yousefi, executive vice president, automotive, coherent DSP and switch group at Marvell. “And we have programmes inside the company to do co-packaged optics as well.”
Innovium
Innovium’s Teralynx family addresses the needs of large-scale data centres and will complement Marvell’s Prestera switch-chip portfolio that addresses enterprise and carrier applications.
Formed in 2014, Innovium is a private company with a staff of 230, 185 of which are engaged in R&D. The company has also raised a total of $400 million in funding.
Innovium is already shipping its 12.8-terabit Teralynx 7 to a leading cloud provider and expects revenues of $150 million in 2022. And earlier this year, it announced it shipped over 1 million 400-gigabit switch-silicon ports in 2020.
“The top cloud players are the ones that drive most of the revenues,” says Yousefi. “But there is a long list of customers that are engaged with Innovium at different capacities and there are a bunch of Tier-2s [data centre operators].”
Marvell gained the Xpliant programmable switch-chip architecture for the data centre when it acquired Cavium Networks in 2018, says Devan Adams, principal analyst at LightCounting.
But soon after the acquisition, the Xpliant switch chip line was discontinued as Marvell decided to concentrate on expanding its Prestera chip family.
Now Marvell has returned to the market to gain a scalable, low-latency architecture that addresses the needs of the mega data centre players.
“When you think of the overall data centre market and how it is booming, Innovium makes Marvell’s solutions more attractive to the key cloud customers by helping them expand their switch-chip offerings,” says Adams.
Marvell says it was impressed with the Innovium design team and with the Teralynx architecture when assessing the company as a potential buy. “We also liked the fact that customers have validated the architecture and that it is shipping and in live networks,” says Yousefi.
Broadcom dominates the switch-chip market. According to the market research company, 650 Group, Broadcom had 72 per cent of the 50-gigabit serialiser-deserialiser (serdes) cloud-based switch market in the first quarter, 2021, while Innovium had 27 per cent.
The cloud players want a choice of suppliers, not just for procurement reasons but to ensure sufficiently strong suppliers that can address their needs.
This latest acquisition, expected to close before the year-end, will be Marvell’s fifth acquisition in four years.
Marvell acquired Inphi earlier this year and two custom ASIC companies in 2019: Avera Semiconductor, originally the ASIC group of IBM Microelectronics, and Aquantia that has multi-gigabit PHY expertise. A year before that, Marvell acquired Cavium, as mentioned.
Marvell will use its sales force to promote Innovium’s products to a larger customer base including customers using its Prestera switch chips.
Adams also notes that Marvell has a broad supply chain and a strategic relationship with leading foundry TSMC that will benefit Innovium in the making of its chips, especially when semiconductors are currently in short supply.
Switch chip styles
There are two types of Ethernet switch chips. For the mega data centres, what is important is capacity and the chip’s throughput per Watt (gigabit-per-second/ Watt). Cloud players need to move traffic efficiently in the data centre and with a low latency. Such chips have a streamlined packet-processing capability. Examples include Broadcom’s Tomahawk and Innovium’s Teralynx lines.
In contrast, enterprises need to support various networking protocols and that requires a broad feature set and packet-processing capability. Marvell’s Prestera and Broadcom’s Trident portfolios fall into this category.
“It is hard to design one device that addresses both,” says Yousefi. “That is why there are two different architectures, design teams, databases and chips.”
Marvell highlights Innovium’s Teralynx portfolio’s low power and low latency. “Even though the application for these devices is supposed to be streamlined, Innovium has managed to put in programmability features that makes the architecture more flexible,” says Yousefi. “These are important differentiators.”
Innovium’s Teralynx 8 family includes a 7nm CMOS, 25.6-terabit chip with 112 gigabit-per-second (Gbps) serialisers-deserialisers (serdes). “The Teralynx 8 switch chip is in the bring-up phase with customers; it is not shipping in volume yet,” says Yousefi.
A future Teralynx 9 has also been mentioned.
Yousefi confirms there will be a next-generation 51.2-terabit switch chip and devices beyond that; what the next device will be called is to be determined.
The Marvell acquisition will also combine the serdes expertise of Inphi and Innovium. “We are going to help, but right now we can’t really do much as two separate companies,” says Yousefi.
Integration
Yousefi is also definitive about Marvell’s co-packaged optics plans but points out that the adoption of the technology will take time for the whole industry.
The integration of the Innovium team within Marvell will be fine-tuned once the two companies formally merge. At a high-level, the Innovium team will continue to focus on what it does best: the high-capacity product line, says Yousefi.
“The real opportunity is how do you leverage the collective teams’ knowledge and efficiencies, share the best practices, help each other out during peak resource crunches, and release products more efficiently,” he says.
More acquisitions
The Innovium deal follows the likes of Intel buying Barefoot Networks and Nvidia buying networking specialist Mellanox which designs its own switch chips.
For Adams, it was those deals that suggested it was only a question of time before someone bid for Innovium.
Adams admits he has no insight into Marvell’s acquisition plans, but he points to how Marvell had its own server CPU chip, the ThunderX3 chip based on ARM cores, which was cancelled last year. Could Marvell decide to re-enter the market via the acquisition route?
Another potential technology Marvell could acquire is programmable logic. FPGAs are used in the data centre as accelerators. Adams also points out that certain switch vendors have added FPGAs to their platforms for niche applications such as high-frequency trading.
As for artificial intelligence (AI) hardware, Marvell has its own IP and has added hardware blocks for AI as part of it Octean 10 design. So perhaps the buying of an AI chip start-up is less likely for now.
Yousefi does not rule out more Marvell acquisitions. “The industry is all about growth and how you can position yourself to do many things,” he says.
But he stresses it will take Marvell time to absorb the latest acquisitions of Inphi and Innovium: “That is just as important as acquiring the right assets.”
Open Eye gets webscale attention
Microsoft has trialled optical modules that use signalling technology developed by the Open Eye Consortium.
The webscale player says optical modules using the Open Eye’s analogue 4-level pulse-amplitude modulation (PAM-4) technology consume less power than modules with a PAM-4 digital signal processor (DSP).
Brad Booth
“Open Eye has shown us at least an ability that we can do better on power,” says Brad Booth, director, next cloud system architecture, Azure hardware systems and infrastructure at Microsoft, during an Open Eye webinar.
Optical module power consumption is a key element of the total power budget of data centres that can have as many as 100,000 servers and 50,000 switches.
“You want to avoid running past your limit because then you have to build another data centre,” says Booth.
But challenges remain before Open Eye becomes a mainstream technology, says Dale Murray, principal analyst at market research firm, LightCounting.
Open Eye MSA
When the IEEE standards body developed specifications using 50-gigabit PAM-4 optical signals, the assumption was that a DSP would be needed for signal recovery given the optics’ limited bandwidth.
But as optics improved, companies wondered if analogue circuitry could be used after all.
Such PAM-4 analogue chips would be similar to non-return-to-zero (NRZ) signalling chips used in modules, as would the chip assembly and testing, says Timothy Vang, vice president of marketing and applications, signal integrity products group, Semtech. The analogue chips also promised to be cheaper than DSPs.
This led to the formation of the Open Eye multi-source agreement (MSA) in January 2019. Led by MACOM and Semtech, the MSA now has 37 member companies.
“We felt that if we could enable that capability, you could use the same low-cost optics and, with an Open Eye specification - an eye-mask specification - you get a manufacturable low-cost ecosystem,” says Vang. “That was our goal and we were not alone.”
But a key issue is whether Open Eye solutions will work with existing DSP-based PAM-4 modules that have their own testing procedure.
“Can they eliminate all concerns for interoperability between analogue and DSP based modules without dual testing?” says Murray. “And will end users go with a non-standard solution rather than an IEEE-standard solution?”
“We do face the dilemma LightCounting points out,” says Vang. “It is possible there are poor or older DSP-based modules that wouldn’t pass the Open Eye test, and that could lead data centres to say: ‘Well, that is not good enough’.”
Dale Murray
“It is a concern,” says Microsoft’s Booth. The first Open Eye samples Microsoft received didn't talk to all the DSP-based modules, he says, but the next revision appeared to address the issue.
“Digital interfaces are certainly easier, but we're burning a lot of power with the DSPs, in the modules and the switch ASIC,” says Booth. “The switch ASIC needs it for direct attach copper (DAC) cables.”
However, the MSA believes that the cost, power and latency advantages of the Open Eye ICs will prove decisive.
Data centre considerations
Microsoft’s Booth outlined the challenges data centre operators face as bandwidth requirements grow exponentially.
The drivers for greater bandwidth include more home-workers using cloud services during the Covid-19 pandemic and the adoption of artificial intelligence and machine learning.
“With machine learning, the more machines you have talking to each other, the more intensive jobs you can handle,” says Booth. “But for distances greater than a few meters you fall into the realm of the 100m range, and that drives you to an optical solution.”
But optics are costly while going from 100-gigabit to 400-gigabit optical modules has not reduced power consumption. Booth says 400-gigabit SR8 modules consume about 10W while the 400-gigabit DR4 and FR4, it is 12W. Yet for 100-gigabit modules the power consumed is a quarter of these figures.
Low latency is another requirement if data centres are to adopt disaggregated servers where memory is pooled and shared between platforms. “Adding latency to these links, which are fairly short, is an impediment to do this disaggregation scenario,” says Booth.
Microsoft trialled an eight-lane on-board optics COBO module using Open-Eye and achieved a 30 per cent power saving compared to QSFP-DD or OSFP DSP-based pluggable modules.
Open Eye technology could also be used for co-packaged optics, promising a further 10 per cent power saving, says Booth.
Given future 51.2-terabit and 102.4-terabit switch silicon, with their significant connectivity, this will help reduce the overall thermal load and hence cooling which is part of a data centre’s overall power consumption.
“Anything that keeps that heat lower as I increase the bandwidth is an advantage,” says Booth.
Cost, power and latency
The Open Eye MSA claims it will cost a company $80 million to develop a next-generation 5nm CMOS PAM-4 DSP. Such a hefty development cost will need to be recouped, adding to a module's price.
Semtech says its Open Eye analogue ICs use a BiCMOS process which is a far cheaper approach.
Timothy Vang
The PAM-4 DSPs may consume more power, says Vang, but that will improve with newer CMOS processes. First-generation DSPs were implement using 16nm CMOS while the latest devices are at 7nm CMOS.
So the power advantage of Open Eye devices will shrink, says Vang, although Semtech claims its second-generation Open Eye devices will reduce power by 20 per cent.
Open Eye also has a latency advantage. Citing analysis from Nvidia (Mellanox), a PAM-4 DSP-based optical module adds 100ns of latency per link.
In a multi-hop network linking servers, the optical modules account for 40 per cent of the total latency, the rest being the switch, the network interface card and the optical flight time. Using Open Eye-based modules, the optical module portion shrinks to eight per cent only.
Specification status
The Open Eye MSA has specified 53-gigabit PAM-4 signalling for long-reach and short-reach optical links.
In particular, to its 200-gigabit FR4 specification, the MSA is adding 50-gigabit LR1, while an ER1 lite and 200-gigabit LR4 will be completed in early 2021. Meanwhile, the multi-mode 50-gigabit SR1, 200-gigabit SR4 and 400-gigabit SR8 specifications are done.
The third phase of the Open Eye work, producing a 100-gigabit PAM-4 specification, is starting now. Achieving the specification is important for Open Eye since modules are moving to 100-gigabit PAM-4, says Murray.
A 200-gigabit QSFP56-FR4 module block diagram. Source: CIG.
Products
Semtech is already selling 200-gigabit Open Eye short-reach chips, part of its Tri-Edge family. The two 4x50-gigabit devices are dubbed the GN2558 and GN2559.
The GN2558 is the transmitter chip. It retimes four 50-gigabit signals from the host and feeds them to the integrated VCSEL drivers that generate the optical PAM-4 signals sent over four fibres. The four photo-detector outputs are the receiver are then fed to the GN2559 that includes trans-impedance amplifiers (TIAs) and clock data recovery.
Equalisation is used within both devices. “The eye is opened on the transmitter as well as on the receiver; they equalise the signal in each direction,” says Vang.
The Semtech devices are being used for a 200-gigabit SR4 module and for a 400-gigabit SR8 active optical cable where two pairs of each chip are used.
Semtech will launch Tri-Edge long-reach Open Eye chips. The chips will drive externally-modulated lasers (EMLs), directly- modulated lasers (DMLs) and silicon photonics-based designs for single-mode fibre applications.
“We have early versions of these chips sampled and demonstrated,” says Vang. “In the Open Eye MSA, we have shown the chips interoperating with, for example, MACOM’s chipset.”
Semtech’s Tri-Edge solutions are in designs with over two dozen module customers, says Vang.
Meanwhile, pluggable module maker CIG detailed a 200-gigabit QSFP56-FR4 while Optomind discussed a 400-gigabit QSFP56-DD active optical cable design as part of the Open Eye webinar.
Optical supply chain set to withstand the COVID-19 crisis
The optical supply chain will not experience any lasting damage as a result of the COVID-19 pandemic. So argues LightCounting in a research note.
The market research company notes how the experience of the Coronavirus pandemic has highlighted the many benefits of the digital economy.
And the jolt the world is experiencing will if anything, strengthen it.
“All kind of things are happening as a result of the pandemic,” says John Lively, principal analyst at LightCounting and author of the research note. “Telecommuting, telelearning and telemedicine have all been used before, but never on a scale like this.”
Pandemic toll
Given how governments have shut down activities to contain the spread of the virus, it comes as no surprise the severity with which the world’s economy has been hit during the first quarter of 2020.
LightCounting cites startling figures concerning the world’s two largest economies.
Some 6.6 million Americans filed unemployment claims in the week ending April 1st, double the previous record that was set just a week earlier. And up to 47 million jobs could be lost, a third of the total US workforce, according to the US Federal Reserve Bank.
Meanwhile, in China, the gross domestic product (GDP) in the first quarter is expected to plummet 9 per cent, the first decline in three decades.
Looking more closely at the telecom and datacom industries, LightCounting highlights four developments that overall give cause for optimism.
Returning to work
First, China is returning to work. LightCounting cites figures from China that claim that factories are now staffed at 80-90 per cent of their full production levels. However, figures published by the American Chamber of Commerce in China are less rosy. Of the 120 member companies it surveyed, a quarter said all their staff continued to work from home (as of March 13th).
Talking to Chinese optical component companies, LightCounting says each firm has gone through a process with their local governments to reopen such as meeting the various hygiene protocols and ensuring a suitable distance between staff.
The second development is notable growth in network traffic as a result of people working from home and families being in lockdown.
The growth in the use of the videoconferencing tool, Zoom, is well documented, but strong growth has been witnessed elsewhere. Microsoft’s Teams collaboration application reached 44 million daily users, up 12 million in a week, while the use of its Windows Virtual Desktop has tripled.
In turn, AT&T and Verizon have reported double-digit growth in viewers of their TV and streaming demand content, while Netflix, YouTube and Disney have cut by a quarter their streaming video quality in Europe to lessen the network burden.
Spending on infrastructure by the operators, the third pointer highlighted by LightCounting, promises encouraging growth. The main three Chinese operators plan to increase their 5G spending in 2020. China Mobile, for example, is spending 100 billion yuan on 5G infrastructure, 4x what it spent on 5G in 2019.
Lastly, telecom equipment and component sales are expected to be down in the first quarter, with five companies – Ciena, Infinera, Lumentum, II-VI and NeoPhotonics – issuing guidance warnings.
These range from Ciena which lowered its previous guidance by 3 per cent to NeoPhotonics which expects a 10 per cent drop in the first quarter.
The responses of Chinese optical component players range from not expecting sales to be hit at all to a 15 per cent decline in 2020. LightCounting also noted that companies with sales predominantly outside China were more worried about demand in the coming two quarters.
Punctuated Equilibrium
LightCounting cites a concept coined by Stephen J. Gould, the late evolutionary biologist, of punctuated equilibrium which argues that species do not evolve at a constant rate. Rather, they experience long periods of stability followed by rapid bursts of change due to significant disturbances in their environment.
“The same applies to societies and economies,” says Lively.
This explains why LightCounting believes the coronavirus of 2020-21 will accelerate trends that promote the digital economy.
Lively cites the tens of millions of US students and adult workers now operating from home. “Once the genie is out of the bottle it may prove difficult to put back,” says Lively who, as an analyst, has worked from home for over two decades.
In turn, the need for social hygiene and new habits such as touch-free shopping will boost adoption of digital wallet technology.
Current events also highlight the importance of broadband and the disparity in the quality of service being delivered, especially in rural areas. This too will cause change.
The hyperscalers – Alphabet (Google), Amazon, Apple, Facebook and Microsoft – are well-positioned to weather the storm, being providers of the hubs of the digital economy and having deep pockets. Malls and other brick-and-mortar retailers, in contrast, will suffer greatly.
Lively stresses that it is early days and that the analysis is speculative. It also assumes that massive damage won’t be done to huge swathes of the global economy.
But he is confident that the optical industry will not be badly damaged, and nowhere near the scale of the bursting of the dotcom bubble in 2000 that then crashed the optical industry.
“The oversupply of bandwidth [which developed during the dotcom boom] resulted in a drastic cutback in demand, and that hit our industry directly,” he says. Revenues shrank 30 per cent in 2001 and 30 per cent again in 2002.
“It took years to recover and many companies went out of business including hundreds of start-ups,” says Lively. “But the big players remain, even if some have changed their names.”
Current events will not be as severe as two decades ago since the epic oversupply of bandwidth directly impacted the optical industry, says Lively.
He also ends on a positive note: “It is difficult to think of another industry we would rather be in as we ride this storm.”
Lumentum completes sale of certain datacom lines to CIG
Brandon Collings, CTO of Lumentum, talks CIG, 400ZR and 400ZR+, COBO, co-packaged optics and why silicon photonics is not going to change the world.
Lumentum has completed the sale of part of its datacom product lines to design and manufacturing company, Cambridge Industries Group.
The sale will lower the company's quarterly revenues by between $20 million to $25 million. Lumentum also said that it will stop selling datacom transceivers in the next year to 18 months.
The move highlights how fierce competition and diminishing margins from the sale of client-side modules is causing optical component companies to rethink their strategies.
Lumentum’s focus is now to supply its photonic chips to the module makers, including CIG. “From a value-add point of view, there is a lot more value in selling those chips than the modules,” says Brandon Collings, CTO of Lumentum.
400ZR and ZR+
Lumentum will continue to design and sell line-side coherent optical modules, however.
“With coherent, there is a lot of complexity and challenge in the module’s design and manufacture,” says Collings. “We believe we can extract the value we need to continue in that business.”
The emerging 400ZR and 400ZR+ are examples of such challenging coherent interfaces.
The 400ZR specification, developed by the Optical Internetworking Forum (OIF), is a 400-gigabit coherent interface with an 80km reach. The 400 gigabit-per-second (Gbps) line rate will be achieved using a 64-gigabaud symbol rate and a 16-QAM modulation scheme.
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“[400ZR] is not client-side. Sixty-four gigabaud is very hard to do in such an extremely compact form factor.
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Module makers will implement the 400ZR interface using client-side pluggable modules such as the QSFP-DD and the OSFP to enable data centre operators to add coherent interfaces directly to their switches.
But implementing 400ZR will be a challenge. “This is not client-side,” says Collings. “Sixty-four gigabaud is very hard to do in such an extremely compact form factor.”
First samples of 400ZR modules are expected by year-end.
The 400ZR+ interface, while not a specification, is a catch-all for a 400-gigabit coherent that exceeds the 400ZR specification. The 400ZR+ will be a multi-rate design that will support additional line rates of 300, 200 and 100Gbps. Such rates coupled with more advanced forward-error correction (FEC) schemes will enable the 400ZR+ to span much greater distances than 80km.
The 400ZR+ interface helps the developers of next-generation coherent DSP chips to recoup their investment by boosting the overall market their devices can address. “It is basically a way of saying I’m going to spend $50 million developing a coherent DSP, and the 400ZR market alone is not big enough for that investment,” says Collings.
Lumentum says there will be some additional functionality that will be possible to fit into a QSFP-DD such that at least one of the ZR+ modes will be supported. But given the QSFP-DD module’s compactness and power constraints, the ZR+ will also be implemented in the CFP2 form factor that has the headroom needed to fully exploit the coherent DSP’s capabilities to also address metro and regional networks.
400ZR+ modules are expected in volume by the end of 2020 or early 2021.
DSP economics
Lumentum will need to source a coherent DSP for its 400ZR/ ZR+ designs as it does not have its own coherent chip. At the recent OFC show held in San Diego, the talk was of new coherent DSP players entering the marketplace to take advantage of the 400ZR/ZR+ opportunity. Collings says he is aware of five DSP players but did not cite names.
NEL and Inphi are the two established suppliers of merchant coherent DSPs. Lumentum (Oclaro) has partnered with Acacia Communications to use its Meru DSP for Lumentum’s CFP2-DCO design, although it is questionable whether Acacia will license its DSP for 400ZR/ ZR+, at least initially.
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“God forbid if 10 or more players are doing this as no matter how you slice it, people will be losing [money]”
Lumentum and Oclaro also partnered with Ciena to use its WaveLogic Ai for a long-haul module. That leaves room for at least one more provider of a coherent DSP that could be a new entrant or an established system vendor that will license an internal design.
Collings points out that it makes no sense economically to have more than five players. If it takes $50 million to tape out a 7nm CMOS coherent DSP, the five players will invest a total of $250 million. And if the investment cost for the module, photonics and everything else is a comparable amount, that equates to $500 million being spent on the 400-gigabit coherent generation.
As for the opportunity, Collings talks of about a total of up to 500,000 ports a year by 2020. That equates to an investment return in the first year of $1,000 per device sold. “God forbid if 10 or more players are doing this as no matter how you slice it, people will be losing [money].”
Beyond Pluggables
The evolution of optics beyond pluggables was another topic under discussion at OFC.
The Consortium of On-Board Optics (COBO), the developerof an interoperable optical solution that embeds optics on the line card, had a stand at the show and a demonstration of its technology. In turn, co-packaged optics, the stage after COBO in the evolution of optical interfaces that will integrate the optics with the silicon in one package, is also now also on companies' agenda.
Collings explains that COBO came about because the industry thought on-board optics would be needed given the challenge of 400-gigabit pluggables meeting the interface density needed for 12.8-terabit switches . “I shared that opinion four to five years ago,” he says, adding that Lumentum is a member of COBO.
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“That problem is real. It is a matter of how far the current engineering can go before it becomes too painful.”
But 400-gigabit optics has been engineered to meet the required faceplate density, including ZR for coherent. As a result, COBO is less applicable. “That need to break the paradigm is a lot less,” he says.
That said, Collings says COBO has driven valuable industry discussion given that the data centre is heading in a direction where 32 ports of 800-gigabit interfaces will be needed to get data in and out of next-generation, 25-terabit switches.
“That problem is real,” says Collings. “It is a matter of how far the current engineering can go before it becomes too painful.” Scaling indefinitely what is done today is not an option, he says.
It is possible with the next generation of switch chip to simply use a two-rack-unit box with twice as many 400-gigabit modules. “That has already been done at the 100-gigabit generation that lasted longer because it doubled up the 100-gigabit port count,” he says.
“In the generation after that, you are now asking for stuff that looks very challenging with today’s technology,” he says. “And that is where co-packaging is focused, the 50-terabit switch generation.” Switches using such capacity silicon are expected in the next four years.
But this is where it gets tricky, as co-packaging not only presents significant technical challenges but also will change the supply chain and business models.
Collings points out that hyperscalars do not like making big pioneering investments in new technology, rather they favour buying commodity hardware. “They don’t like risk, they love competition, and they like a healthy ecosystem,” he says.
“There is a lot of talk from the technology direction of how we can solve this problem [using co-packaged optics] but I think on the business side, the riskside, the investment side is putting a lot of pressure on that actually happening,” says Collings. “Where it ends up I don’t honestly know.”
Silicon photonics
One trend evident at OFC was the growing adoption of silicon photonics by optical component companies.
Indeed, the market research firm, LightCounting, in a research note summarising OFC 2019, sees silicon photonics as a must-have technology given co-packaged optics is now clearly on the industry’s roadmap.
However, Collings stresses that Lumentum’s perspective remains unchanged regarding the technology.
“It’s a fabless exercise so we can participate in silicon photonics and, quite frankly, that is why a lot of other companies are participating because the barrier to entry is quite low,” says Collings. “Nevertheless, we look at silicon photonics as another tool in the toolbox: it has advantages in some areas, some significant disadvantages in others, and in some places, it is simply comparable.”
When looking at a design from a system perspective such as a module, other considerations come into play besides the cost of the silicon photonics chip itself. Collings cites the CFP2 coherent module. While the performance of its receiver is good using silicon photonics, the modulator is questionable. You also need a laser and a semiconductor optical amplifier to compensate for silicon photonics higher loss, he says,
The alternative is to use an indium phosphide-based design and that has its own design issues. “What we are finding when you look at the right level is that the two are the same or indium phosphide has the advantage,” says Collings. “And as we go faster, we are finding silicon is not really keeping up in bandwidth and performance.”
As a result, Lumentum is backing indium phosphide for coherent operating at 64 gigabaud.
“A lot of people are talking about silicon photonics because they can talk about it,” says Collings. “It’s not worthless, don’t get me wrong, but its success outside of Acacia has been niche, and Acacia is top notch at doing this stuff.”
Finisar demonstrates its first silicon photonics transceiver
- Finisar unveiled its first silicon photonics-based product, a 400-gigabit QSFP-DD DR4 module, at the recent ECOC event.
- The company also showed transceiver technology that simplifies the setting up of dense wavelength-division multiplexing (DWDM) links.
- Two 200-gigabit QSFP56 client-side modules and an extended reach 30km 400-gigabit eLR8 were also demonstrated by Finisar.
- A 64-gigabaud integrated tunable transmitter and receiver assembly (ITTRA) was used to send a 400-gigabit coherent wavelength.
Finisar is bringing to market its first silicon photonics-based optical module.
Christian UrricarietThe 400GBASE-DR4 is an IEEE 500m-reach 400-gigabit parallel fibre standard based on four fibres, each carrying a 100-gigabit 4-level pulse amplitude modulation (PAM-4) signal. Finisar’s DR4 is integrated into a QSFP-DD module.
“The DR4 is the 400-gigabit interface that most of the hyperscale cloud players are interested in first,” says Christian Urricariet, senior director of global marketing at Finisar.
The company demonstrated the module at the recent European Conference on Optical Communication (ECOC), held in Rome.
Silicon photonics-based DR4
The DR4 is an integrated design, says Finisar, comprising modulators and photo-detectors as well as modulator drivers and the trans-impedance amplifiers (TIAs).
Finisar chose silicon photonics for the DR4 after undertaking an extensive technology study. Silicon photonics emerged as ‘a clear winner’ in terms of cost and performance for photonic designs made up of similar functions in parallel, such as the four-channel DR4. Silicon photonics manufacturing is also scalable, making it ideal for high-volume designs.
The DR4 is the 400-gigabit interface that most of the hyperscale cloud players are interested in first
The DR4 can also be used in a breakout mode to interface to four 100GBASE-DR modules. Also referred to as the DR1, the 100GBASE-DR fits within an SFP-DD or a QSFP28 module.
The DR4-DR1 combination can link four servers, each using a 100-gigabit link, to a 400-gigabit port on a top-of-rack or mid-row switch. The top-of-rack 400-gigabit DR4 can also connect to a leaf switch with multiple 100-gigabit ports. “The DR4 can be used ‘top-of-rack down’ [to servers] or ‘top-of-rack up’ [to leaf switches],” says Urricariet. “This is similar to what people are doing with the [100-gigabit parallel fibre] PSM4.”
400-gigabit eLR8
Finisar also showcased an extended reach version of the IEEE 400GBASE-LR8 standard.
Dubbed the eLR8, the QSFP-DD module is a technology demonstrator not a product that extends the reach of the LR8 from 10km to 30km.
Finisar already has an LR8 product in a CFP8 pluggable module and is moving the design to the smaller QSFP-DD. The LR8 is an eight-wavelength duplex interface where each wavelength carries a 50-gigabit PAM-4 signal.
“The 400GBASE-LR8 is a low-risk approach to achieving a 400-gigabit duplex single-mode link in the short term,” says Urricariet. “You don’t have to wait for 100-gigabit PAM-4 [ICs] to be manufactured in high volume.”
Urricariet says the IEEE is considering developing an extended LR8 standard with a 40km reach but such distances could also be addressed using inexpensive coherent technology.
Finisar’s design achieves the extended range using the same components as its LR8 module - directly modulated DFB lasers and PIN photodetectors. “There is plenty of margin with that [LR8 design],” says Urricariet. This suggests Finisar picked the best performing DFBs and PINs for the eLR8 design.
The QSFP-DD 10km LR8 design is sampling now, with general availability from the first half of 2019.
Flextune
Configuring DWDM links can be likened to two groups of people separated in a wood at night. Each individual has a flashlight and is tasked with finding a counterpart from the second group, a process repeated until everyone is paired.
Setting up DWDM links is comparable to telling each individual the exact path to take to find their counterpart. The Flextune technology that Finisar has developed can be viewed as giving each individual the confidence to stride out - sweeping their flashlights as they go - till they find a counterpart.
Currently, setting up a DWDM link requires coordination between a field engineer and network operations staff. Each tunable transceiver that is plugged into a port is told which wavelength to tune to. The system itself may tell the transceiver the wavelength to use or a field engineer programs each transceiver before it is plugged into the platform.
Equally, the transceiver output fibre must be connected to the right optical multiplexer and demultiplexer (mux-demux) port, as do the transceivers at the link’s other end.
The result is a time-consuming process that is prone to human error.
With Flextune, the tunable transceivers are plugged into the equipment’s ports and connected to the mux-demux’s ports. “It does not matter which port,” says Urricariet. “The transceivers search for each other and self-configure to the right wavelength.”
Each Flextune-enabled transceiver operates independently of the transceiver at the other end; there is no master-slave arrangement, says Urricariet, although a master-slave arrangement can be used if requested.
The mux-demux must also be a blocking architecture for Flextune to work. “If the mux-demux does not block the other wavelengths on each port, then you have a mess,” says Urricariet. With such a mux-demux, the channels scanned are blocked until the transceiver’s output is passed to the right channel. Once the link is established, the two transceivers set permanently to that wavelength.
“It [the process] happens at both ends simultaneously and on all the ports,” says Urricariet. “The basic technique can self-tune up to 96 [DWDM] channels in around five minutes.”
Being able to tune independently of the host equipment means that the Flextune-enabled transceivers can also be sold directly to operators and plugged into any of their equipment.
Urricariet says Flextune promises welcome operational savings given DWDM’s increasing adoption in the access network with developments such as 5G fronthaul.
The basic technique can self-tune up to 96 [DWDM] channels in around five minutes
Flextune will also be used for metro and data centre interconnect applications, as well as connecting Remote PHY nodes being deployed in cable networks. “The Remote PHY is also a big focus for this type of feature,” says Urricariet.
Finisar demonstrated Flextune with its 10-gigabit tunable SFP+ modules that are now sampling. Flextune will also be adopted for its 25-gigabit SFP+ that will sample ‘very soon’, followed by coherent modules.
“We do have a CFP2-ACO module in production and other coherent products on our roadmap,” says Urricariet. “We will be looking to implement Flextune technology in these products as well.”
Google has started deployments of 2x200GbE
200 Gigabit Ethernet: a growing interim solution
Finisar also demonstrated two 200-gigabit modules. The QSFP56 implements the 2km FR4 specification. The 200-gigabit FR4 uses four coarse WDM (CWDM) wavelengths, each carrying a 50-gigabit PAM-4 signal.
Finisar has previously said it will develop 200-gigabit modules for the large-scale data centres interested in the technology as an interim solution before 400-gigabit modules ramp. Such an intermediate market for “one hyperscaler and maybe two” is sufficient to justify making 200-gigabit modules, says Urricariet.
Market research firm LightCounting has increased its forecast for 200 Gigabit Ethernet (GbE) modules due to interest from Facebook.
A presentation by Facebook at ECOC suggested that 400 GbE is far from being ready, says Vladimir Kozlov, CEO of LightCounting. “It looks like 200GbE is being considered now, but Facebook may change its mind again,” says Kozlov. “In the meantime, Google has started deployments of 2x200GbE [in an OSFP module] as planned.”
As with the 400-gigabit eLR8, Finisar also demonstrated an extended reach version of the 200-gigabit FR4 to achieve a 10km reach. “This is not to be confused with the 10km 200-gigabit LR4 that is a LAN-WDM grid based design,” says Urricariet. “The extended FR4 uses a CWDM grid.”
ITTRA
At OFC 2018 in March, Finisar unveiled its 32-gigabaud (Gbaud) integrated tunable transmitter and receiver assembly (ITTRA) that combines the optics and electronics required for an analogue coherent optics interface.
The ITTRA comprises a tunable laser, an optical amplifier, modulators, modulator drivers, coherent mixers, a photo-detector array and the accompanying TIAs. All the components of the 32Gbaud ITTRA are integrated within a gold box that is 70 percent smaller than the size of a CFP2 module. The integrated assembly also has a power consumption below 7.5W.
At ECOC, the company demonstrated its second ITTRA design operating at 64Gbaud to transmit a 400-gigabit wavelength using 16-ary quadrature amplitude modulation (16-QAM). Finisar would not detail the power consumption of the 64Gbaud ITTRA.
“The doubling of the speed to 64Gbaud will enable 400-gigabit DCO modules as well as 400ZR,” says Urricariet. Digital coherent optics (DCO) refers to coherent modules that integrate the optics and the coherent digital signal processor (DSP).
Samples and production of the 64Gbaud ITTRA are due in 2019.
Optical integration and silicon photonics: A view to 2021
LightCounting’s report on photonic integration has several notable findings. The first is that only one in 40 optical components sold in the datacom and telecom markets is an integrated device yet such components account for a third of total revenues.
Another finding is that silicon photonics will not have a significant market impact in the next five years to 2021, although its size will grow threefold in that time.
By 2021, one in 10 optical components will be integrated and will account for 40% of the total market, while silicon photonics will become a $1 billion industry by then.
Integrated optics
“Contrary to the expectation that integration is helping to reduce the cost of components, it is only being used for very high-end products,” says Vladimir Kozlov, CEO of LightCounting.
He cites the example of the cost-conscious fibre-to-the-home market which despite boasting 100 million units in 2015 - the highest volumes in any one market - uses discrete parts for its transceivers. “There is very little need for optical integration in this high-volume, low-cost market,” he says
Where integration is finding success is where it benefits device functionality. “Where it takes the scale of components to the next level, meaning much more sophisticated designs than just co-packaged discrete parts,” says Kozlov. And it is because optical integration is being applied to high-end, costlier components that explains why revenues are high despite volumes being only 2.4% of the total market.
Defining integration
LightCounting is liberal in its definition of an integrated component. An electro-absorption modulated laser (EML) where the laser and modulator are on the same chip is considered as an integrated device. “It was developed 20 years ago but is just reaching prime time now with line rates going to 25 gigabit,” says Kozlov.
Designs that integrate multiple laser chips into a transceiver such as a 4x10 gigabit design is also considered an integrated design. “There is some level of integration; it is more sophisticated than four TO-cans,” says Kozlov. “But you could argue it is borderline co-packaging.”
LightCounting forecasts that integrated products will continue to be used for high-end designs in the coming five years. This runs counter to the theory of technological disruption where new technologies are embraced at the low end first before going on to dominate a market.
“We see it continuing to enter the market for high-end products simply because there is no need for integration for very simple optical parts,” says Kozlov.
Silicon photonics
LightCounting does not view silicon photonics as a disruptive technology but Kozlov acknowledges that while the technology has performance disadvantages compared to traditional technologies such as indium phosphide and gallium arsenide, its optical performance is continually improving. “That may still be consistent with the theory of technological disruption,” he says.
There are all these concerns about challenges but silicon photonics does have a chance to be really great
The market is also developing in a way that plays to silicon photonics’ strengths. One such development is the need for higher-speed interfaces, driven by large-scale data centre players such as Microsoft. “Their appetite increases as the industry is making progress,” says Kozlov. “Six months ago they were happy with 100 gigabit, now they are really focused on 400 gigabit.”
Going to 400 gigabit interfaces will need 4-level pulse-amplitude modulation (PAM4) transmitters that will provide new ground for competition between indium phosphide, VCSELs and silicon photonics, says Kozlov. Silicon photonics may even have an edge according to results from Cisco where its silicon photonics-based modulators were shown to work well with PAM4. This is where silicon photonics could even take a market lead: for 400-gigabit designs that require multiple PAM4 transmitters on a chip, says LightCounting.
Another promise silicon photonics could deliver although yet to be demonstrated is the combination of optics and electronics in one package. Such next-generation 3D packaging, if successful, could change things more dramatically than LightCounting currently anticipates, says Kozlov.
“This is the interesting thing about technology, you never really know how successful it will be,” says Kozlov. “There are all these concerns about challenges but silicon photonics does have a chance to be really great.”
But while LightCounting is confident the technology will prove successful sooner of later, getting businesses that use the technology to thrive will require overcoming a completely different set of challenges.
“It is a challenging environment,” warns Kozlov. “There is probably more risk on the business side of things now than on the technology side.”