OFC 2025 industry reflections - Final Part
Gazettabyte has been asking industry figures for their thoughts after attending the OFC conference held in San Francisco.
In the final part, Arista’s Vijay Vusirikala and Andy Bechtolsheim, Chris Doerr of Aloe Semiconductor, Adtran’s Jörg-Peter Elbers, and Omdia’s Daryl Inniss share their learnings. Vusirikala, Doerr, and Elbers all participated in OFC’s excellent Rump Session.
Vijay Vusirikala, Distinguished Lead, AI Systems and Networks, and Andy Bechtolsheim, Chief Architect, at Arista Networks.
OFC 2025 wasn’t just another conference. The event felt like a significant momentum-gaining inflexion point, buzzing with an energy reminiscent of the Dot.com era optical boom.
This palpable excitement, reflected in record attendance and exhibitor numbers, was accentuated for the broader community by the context set at Nvidia’s GTC event held two weeks before OFC, highlighting the critical role optical technologies play in enabling next-generation AI infrastructure.
This year’s OFC moved beyond incremental updates, showcasing a convergence of foundational technologies and establishing optics not just as a supporting player but a core driver in the AI era. The scale of innovation directed towards AI-centric solutions – tackling power consumption, bandwidth density, and latency – was striking.
Key trends that stood out were as follows:
Lower Power Interconnect technologies
The overarching topic was the need for more power-efficient optics for high-bandwidth AI fabrics. Legacy data centre optics are impacting the number of GPUs that fit into a given data centre’s power envelope.
Three main strategies were presented to address the power issue.
First, whenever possible, use copper cables, which are far more reliable and cost less than optics. The limitation, of course, is copper’s reach, which at 200 gigabit-per-lane is about 1-2m for passive copper cables and 3-4m for active redriven copper cables.
Second, eliminate the traditional digital signal processor (DSP) and use linear interface optics, including Linear Pluggable Optics (LPO), Near Package Optics (NPO), and Co-Packaged Optics (CPO), all of which offer substantial (60%) power savings, lower latency, and higher reliability compared to traditional DSP solutions.
The biggest difference between linear pluggable optics and co-packaged optics is that linear pluggable optics retains the well-known operational advantages of pluggable modules: configurability, multi-vendor support, and easy field serviceability (hot-swapping at module level), compared to fixed optics like co-packaged optics, which require chassis-level RMAs (return materials authorisation). It remains to be seen whether co-packaged optics can overcome the serviceability issues.
Third, developments in a host of new technologies – advances in copper interconnects, microLED-based interconnects, and THz-RF-over-waveguides – promise even lower power consumption than current silicon photonics-based interconnect technologies.
We look forward to hearing more about these new technologies next year.
Transition from 200 gigabit-per-lambda to 400 gigabit-per-lambda
With the 200 gigabit-per-lambda optical generation just moving into volume production in 2025-26, attention has already turned to the advancement and challenges of 400 gigabit-per-lambda optical technologies for future high-speed data transmission, aiming towards 3,200 gigabit (8×400 gigabit) modules.
Several technical approaches for achieving 400 gigabit-per-lambda were discussed, including PAM-4 intensity modulation direct detection (IMDD), PAM-4 dual-polarisation, and optical time division multiplexing (OTDM). The technology choices here include indium phosphide, thin-film lithium niobate (TFLN), and silicon photonics, which are compared based on RF (radio frequency) loss, integration, cost, and high-volume readiness.
For 400 gigabit lambda optics, indium phosphide and thin-film lithium niobate are strong candidates, as silicon photonics will struggle with the high bandwidth.
At this point, it is impossible to predict which platform will emerge as the high-volume winner. Delivering power and cost-effective 400-gigabit lambda optics will require a concerted industry effort from optical component suppliers, connector suppliers, and test and measurement vendors.
Multi-core fibre
A new pain point in large AI data centres is the sheer number of fibre cables and their associated volume and weight. One way to solve this problem is to combine multiple fibre cores in a single fibre, starting initially with four cores, which would offer a 4:1 reduction in fibre count, bulk, and weight.
Hollow-core fibre
Innovation continues in the foundational fibre itself. Hollow-core fibre generated significant buzz, with its potential for lower latency and wider bandwidth attracting intense interest.
The maturing hollow-core fibre ecosystem, including cabling and interconnection progress, suggests deployments beyond niche applications like high-frequency trading may be approaching, reaching areas like distributed AI processing.
AI-driven network evolution
AI isn’t just driving network demand, it is increasingly becoming a network management tool.
Numerous demonstrations showcased AI/machine learning applications for network automation, traffic prediction, anomaly detection, predictive maintenance – e.g., analysing optical time-domain reflectometer (OTDR) traces, configuration management, and resource optimisation. This represents a fundamental shift towards more efficient, reliable, self-configuring, self-healing, and self-optimising networks.
Along with the many technical talks and tutorials, show floor demos, and customer and supplier meetings, OFC attendees also had a chance to combine technology with some light-hearted fun at the rump session.
This year’s topic was rebuilding global communication infrastructure after an alien invasion, and three teams came up with thought-provoking ideas for this theme.
Chris Doerr, CEO of Aloe Semiconductor
The best way to describe OFC 2025 is a giant Mars dust storm that raged for days. The swirling sand made it difficult to see anything clearly, and the sound was so loud you couldn’t think.
Acronyms ending in “O” were hitting you from all sides: LPO, LRO, NPO, CPO, OIO. The wind blew away sand that had buried old technologies, such as lithium niobate, electro-optic polymer, and indium-phosphide modulators, and they joined the fray.
Only now that the storm has somewhat subsided can we start piecing together what the future holds.
The main driver of the storm was, of course, artificial intelligence (AI) systems. AI requires a vast number of communication interconnects. Most interconnects, at least within a rack, are still copper. While copper keeps making incredible strides in density and reach, a fibre-optic interconnect takeover seems more and more inevitable.
The Nvidia announcements of co-packaged optics (CPO), which go beyond co-packaged optics and deserve a new name, such as optical input-output (OIO) or system-on-chip (SOC), created a great deal of excitement and rethinking. Nvidia employs a silicon interposer that significantly increases the electrical escape density and shortens the electrical links. This is important for the long-term evolution of AI computing.
The CPO/OIO/SOC doesn’t mean the end of pluggables. Pluggables still bring tremendous value with attributes such as time-to-market, ecosystem, replaceability, etc.
Most pluggables will still be fully retimed, but 100 gigabit-per-lane seems comfortable with linear pluggable optics (LPO), and 200 gigabit-per-lane is starting to accept linear receive optics (LRO).
For 200 gigabit per lane, electro-absorption modulated lasers (EMLs) and silicon photonics have comfortably taken the lead. However, for 400 gigabit per lane, which had two main demos on the show floor by Ciena and Marvell, many technologies are jockeying for position, mostly EMLs, thin-film lithium niobate (TFLN), indium phosphide, and silicon photonics.
Many companies are abandoning silicon photonics, but this author feels this is premature. There were demos at OFC of silicon photonics attaining near 400 gigabit-per-lane, and the technology is capable of it.
An important thing to remember is that the new OIO/SOC technology is silicon photonics and comes from a CMOS foundry. Putting non-CMOS materials such as thin-film lithium niobate or indium phosphide in such a platform could take years of expensive development and is thus unlikely.
In summary, OFC 2025 was very active and exciting. Significant technology improvements and innovations are needed.
The dust is far from settled, so we must continue wading into the storm and trying to understand it all.
Jörg-Peter Elbers, Senior Vice President, Advanced Technology, Standards and IPR, Adtran
OFC 2025 marked its largest attendance since 2003 with nearly 17,000 visitors, as it celebrated its 50th anniversary.
Discussions in 1975 centred around advances in fibre technology for telecommunications. This year’s hottest topic was undoubtedly optical interconnects for large-scale AI clusters.
Following an insightful plenary talk by Pradeep Sindhu from Microsoft on AI data centre architecture, sessions were packed in which co-packaged optics (CPO) and associated technologies were discussed. The excitement had been fueled by Nvidia’s earlier announcement of using co-packaged optics in its next generation of Ethernet and Infiniband switches.
The show floor featured 800 gigabit-per-second (Gbps), 1.6 terabit-per-second (Tbps), and the first 3.2Tbps interconnect demonstrations using different interface standards and technologies.
For access, 50G-PON was showcased in triple PON coexistence mode, while interest in next-generation very high-speed PON spurred the technical sessions.
Other standout topics included numerous papers on fibre sensing, stimulating discussions on optical satellite communications, and a post-deadline paper demonstrating unrepeated hollow-core fibre transmission over more than 200km.
OFC 2025 was fun too. When else do you get to reimagine communications after an alien attack, as in this year’s rump session?
No visit to San Francisco is complete without trying one of Waymo’s self-driving taxis. Having been proud of Dmitri Dolgov, Waymo’s CEO, for his plenary talk at OFC 2019, it was thrilling to see autonomous driving in action. I love technology!
Daryl Inniss, Omdia Consultant, Optical Components and Fibre Technologies
I worked on commercialising fibre technology for emerging applications at OFS – now Lightera – from 2016 to 2023. I spent the prior 15 years researching and analysing the optical components market.
Today, I see a market on the cusp of a transition due to the unabated bandwidth demand and the rise of computing architectures to support high-performance computing (HPC) and artificial intelligence (AI).
Even optical fibre, the fundamental optical communications building block, is under intense scrutiny to deliver performance suitable for the next 30 to 50 years. Options include hollow-core and multi-core fibre, two of the three fibre technologies that caught my attention at OFC 2025.
The third, polarisation-maintaining fibre arrays for co-package optics, is one part of the conference’s biggest story. OFC 2025 provided a status update on these technologies.
Hollow-core fibre
OFC’s first day hollow-core fibre workshop (S2A) illustrated its niche status and its potential to remain in this state until the fibre is standardised. The industry ecosystem was well represented at the session.
Not surprisingly, challenges highlighted and summarised by Russ Ellis, Microsoft’s Principal Cloud Network Engineer, included manufacturing, field installation, field splicing, cabling, and termination inside the data centre. These are all expected topics and well understood.
I was surprised to hear Microsoft report that the lack of an established ecosystem was a challenge, and I’ll explain why below.
Coming into OFC, the biggest market question was fibre manufacturing scalability, as most reported draws are 5km or less. Supplier YOFC put this concern to rest by showcasing a +20 km spool from a single fibre draw on the show floor. And Yingying Wang, CEO of Linfiber, reported that 50 to 100km preforms will be available this year.
In short, suppliers can scale hollow-core fibre production.
From a field performance perspective, Microsoft highlighted numerous deployments illustrating successful fibre manufacturing, cabling, splicing, termination, installation, and testing. The company also reported no field failures or outages for cables installed over five years ago.
However, to my knowledge, the hollow-core fibre ecosystem challenge is a consequence of a lack of standardisation and discussion about standardisation.
Each fibre vendor has a different fibre design and a different glass outer diameter. Microsoft’s lack-of-an-ecosystem comment mentioned above is therefore unsurprising. Only when the fibre is standardised can an ecosystem emerge, generating volumes and reducing costs,
Today, only vertically integrated players benefit from hollow-core fibre. Until the fibre is standardised, technology development and adoption will be stunted.
Multi-core fibre
I was pleasantly surprised to find multiple transceiver vendors showcasing modules with integrated fan-in/fan-out (FIFO). This is a good idea as it supports multi-core fibre adoption.
One vendor is targeting FR4 (TeraHop for 2x400G), while another is targeting DR8 (Hyper Photonix for 8x100G). There is a need to increase core density, and it is good to see these developments.
However, we are still very far from multi-core fibre commercialisation as numerous operational factors, for example, are impacted. The good news is that multi-core fibre standardisation is progressing.
Polarisation-maintaining fibre
According to Nick Psaila, Intel’s principal engineer and technology development manager, polarisation-maintaining fibre arrays remain expensive.
The comment was made at Optica’s February online Industry Meeting and verified in my follow-up conversation with Psaila.
Using an external laser source is the leading approach to deliver light for co-packaged optics, highlighting an opportunity for high-volume, low-cost polarisation-maintaining fibre arrays.
Co-packaged optics were undoubtedly the most significant topic of the show.
Coherent showcased a 3Tbps concept product of VCSELs to be used in co-packaged optics. Given that multimode fibre is used in the shortest optical connections in data centres and that VCSELs have very low power consumption, I’m surprised I’ve not heard more about their use for this application.
Testing of emerging photonic solutions for HPC and AI devices has been identified as a bottleneck. Quantifi Photonics has taken on this challenge. The company introduced an oscilloscope that provided quality results comparable to industry-leading ones and is designed for parallel measurements. It targets photonic devices being designed for co-packaged optics applications.
Multiple channels, each with wavelength-division multiplexing lasers, must be tested in addition to all the electrical channels. This is time-consuming, expensive process, particularly using existing equipment.
Polymer modulators continue to be interesting because they have high bandwidth and the potential to be inexpensive. However, reliability is their challenge. Another vendor, NLM Photonics, is targeting this application.
The many vendors offering optical circuit switches was a surprising development. I wonder if this opportunity is sufficiently large to justify the number of vendors. I’m told that numerous internet content providers are interested in the technology. Moreover, these switches may be adopted in telecom networks. This is a topic that needs continual attention, specifically regarding the requirements based on the application.
Lastly, Lightmatter provided a clear description of its technology. An important factor is the optical interposer that removes input-output connectivity from the chip’s edge, thereby overcoming bandwidth limitations.
I was surprised to learn that the laser is the company’s design, although Lightmatter has yet to reveal more.
ECOC 2024 industry reflections - Final Part
In the final part, industry figures share their thoughts after attending the recent 50th-anniversary ECOC show in Frankfurt. Contributions are from Adtran’s Jörg-Peter Elbers, Lightwave Logic’s Michael Lebby, and Heavy Reading’s Sterling Perrin.
ECOC exhibition floor
Jörg-Peter Elbers, senior vice presendent, advanced technology, standards and IPR, Adtran, and a General Chair at this year’s ECOC.
ECOC celebrated its 50th anniversary this year. It was great to see scientists, engineers, and industry leaders from all around the globe at a vibrant gathering in Frankfurt.
ECOC dates to September 1975 when the inaugural event – dubbed the “European Conference on Optical Fiber Technology” – was held in London. In the early days, the focus was on megabit-per-second transmission for telephony applications. Now, we are advancing to petabit-per-second speeds to meet AI and cloud services demands.
This year’s ECOC explored various cutting-edge topics, including 1.6 and 3.2 terabit-per-second (Tb/s) transceivers, multi-band and spatial division multiplexing (SDM) transmission, and innovations in access and home networks. Other discussions centred on the merits of linear drive versus regenerated optics, pluggable modules versus co-packaged engines, and the latest IP-over-DWDM architectures and technologies for the coherent edge.
The 50 years of ECOC symposium celebrated the amazing progress of optical communications in the past and painted a promising picture for the future.
David Payne, one of the luminary speakers, stated that hollow-core fibre would enable a new generation of WDM transmission systems (“amplifier-less”) with simpler terminals and higher fibre capacity. In a post-deadline paper, Linfiber reported a hollow-core fibre deployment with a fibre loss lower than solid-core fibre and progress on manufacturing and deployment issues, critical for mass-market adoption.
In the ECOC plenary session, Arista’s Andy Bechtolsheim discussed the race to build AI clusters for generative AI learning and inference. He emphasized that the next generation of hyperscale AI data centres could contain a million AI nodes requiring more than 3GW of electrical power—comparable to the output of a vast nuclear plant. These data centres present opportunities for millions of cost-efficient, low-power terabit-per-second optical interconnects.
The theme of optics for AI was complemented by exploring AI for optics, with multiple contributions examining how generative AI and agent-based models could streamline network operations. The accuracy, predictability, and the explainability of results remain active research topics.
Another highlight was the optical satellite symposium, which discussed using 100 gigabit-per-second (Gbps) coherent optics for satellite communications. While inter-satellite links in commercial low-earth orbit (LEO) constellations use coherent transceiver technology, the use of optical ground links is still in its infancy. Panelists emphasised the challenges of maintaining cloud-free line-of-sight conditions and compensating for atmospheric turbulence to ensure continuous communication. They agreed that combining adaptive optics with time diversity (e.g., by interleaving) offers the best solution for turbulence mitigation, though it adds latency.
Other discussions covered fibre sensing for infrastructure and environmental monitoring and the commercial potential of quantum technologies, sparking much interest and heated debate in this year‘s Rump Session.
As ECOC 2024 concluded, it was clear that the conference not only celebrated five decades of advancement in optical communications but also set the stage for future innovations and challenges.
Dr. Michael Lebby, CEO, Lightwave Logic
As the Chair of the Market Focus at ECOC’s Industry Exhibit, I can say that this year, we had probably the best sessions in ECOC’s 50-year history. For three days, each seat was taken at the Market Focus, which featured wall-to-wall programming on commercial trends, technologies, and roadmaps in optical communications.
Presentations at the market focus sessions supported the big-show exhibition themes. Many talks focused on modules and subsystems. Lightwave Logic showed polymer silicon slot modulators with reliability data operating at 200Gbps with less than 1V drive, with initial results of polymer-plasmonic modulators operating with open 400Gbps eyes. While 400Gbps lanes are still on the roadmap, there were many discussions on what technologies could reach this level of performance, especially modulators. Polymer-plasmonic-based modulators seem to be the leader, with optical bandwidths exceeding 500GHz.
While incumbent technologies are hard to displace, the emerging area of co-packaged pluggables is gaining interest among suppliers, especially for the terabit-per-second data rates sought. While progress was impressive, the reach of silicon photonics modulators for 200Gbps and beyond was a show floor concern.
NewPhotonics discussed how to double data rates using its integrated optical equaliser, while others, such as Pilot Photonics, conveyed the exciting progress with comb laser arrays. Several speakers discussed the metrics of standards that support the AI/ machine learning trends for data centre operators and how optics can support the drive to higher data rates and lower power consumption.
Areas of power consumption driven in part by digital signal processor (DSP) evolution were discussed. The interesting perspective is that if coherent optics are to be developed to serve the edge of the network, then using electronics to help the optics may not be enough; the optics need to perform better so that the electronics can be scaled down to reduce power consumption. It is a trade-off at the heart of many approaches to bring coherent optics to compete with direct-detect solutions for pluggable transceivers.
The indication is that direct detection in data centre optics is not waning as quickly as the community once thought and looks to be a mainstay for pluggable transceiver solutions from 800Gbps, 1.6Tbps, 3.2Tbps, and even 6.4Tbps.
A fireside chat explored the opportunities for copper at super short interconnects where the direct-attach copper (DAC) cables dominate. This 1m to 3m range has been evolving to active electrical copper (AEC) interconnects using smart electronics in recent years. Those of us who are solidly in the optics camp, while acknowledging that copper has owned this segment forever, are still hoping that platforms such as silicon photonics could sneak in and take share in the next five years. However, displacing an incumbent technology such as copper will not be easy, especially when metrics such as economies of scale, cost, and reliability come into play.
Several talks looked at next-generation implementations, such as quantum-dot lasers and photonic wire bonding, and driving VCSELs to ever-increasing speeds. Discussions took place that wondered if VCSELs have reached their limit in bandwidth and speed and if electronics could help them push performance further. A common theme evident was the innovative ideas and concepts to address 224Gbps per lane with optical technologies. While it has been generally accepted that this metric is emerging, several companies are still deciding how to address this speed and 400Gbps per lane.
One big takeaway is that if you have a new and innovative platform to enable things like 3.2Tbps transceivers that is disruptive, think very carefully about whether that disruptive technology needs the infrastructure to be disruptive, too.
Sterling Perrin, Senior Principal Analyst, Heavy Reading
Although I’ve attended nearly every OFC show over the past 25 years, this was my first ECOC. Most of my meetings were centred around an IP-over-DWDM project I’ve worked on for several months, including video interviews conducted at the show with the partnering companies: the OIF, Ciena, Juniper, and Infinera. These are all posted on Light Reading.
Building on its work at OFC 2024, the OIF’s pluggables demo at ECOC spotlighted four applications:
- 400ZR and 800ZR,
- Open ZR+ at 400GbE,
- OpenROADM at 400GbE, and
- 100ZR
The expanding scope of coherent pluggable is impressive, and the interop work includes optics that the OIF is not directly defining—such as Open ZR+, OpenROADM, and 100ZR. ECOC 2024 marked OIF’s first interoperability demonstration of 100ZR modules, an application driven by telecom operators as opposed to hyperscalers.
Another key aspect of the OIF’s IP-over-DWDM work demonstrated at ECOC is the common management interface specification (CMIS) for plug-to-host interoperability between routers and pluggable optics. Plug-to-host interop is essential for wider IP-over-DWDM adoption among telecom operators, so the work is timely.
Related to pluggables management in IP-over-DWDM networks, I attended the Open XR Forum’s symposium on the show floor. The organisation is promoting a dual management approach to pluggables that includes host independent management to support pluggables features that aren’t yet supported in the routers or in CMIS.
During a Q&A, Telefonica’s Oscar Gonzales de Dios acknowledged that host-independent management is controversial (including within Telefonica) but said it is the only way to add point-to-multipoint functions on pluggables for now.
Quantum-safe encryption is another area of research interest, particularly quantum key distribution (QKD), and ECOC 2024 was a great place to get up to date. I attended the rump session debate on quantum technologies, expertly hosted by Peter Winzer (Nubis), Rupert Ursin (QTlabs), and David Neilson (Nokia Bell Labs). It was standing-room-only, and I anticipated strong pro-QKD sentiment. I was wrong! The dominant view was that QKD is impractical, technically limited, too expensive, and needs more real customer demand. Several people argued that post quantum cryptography (PQC) algorithms are sufficient to meet the market needs, without the complexity and costs that QKD brings.
For analysts, conferences like ECOC are the most efficient means of quickly learning what’s hot in the industry. Conferences are equally great places to know what is not hot. I didn’t hear the words “5G,” “xHaul,” “fronthaul,” “6G,” or even “mobility” uttered once during the four days I was in Frankfurt.
OFC 2024 industry reflections: Part 4
Gazettabyte is asking industry figures for their thoughts after attending the recent OFC show in San Diego. This penultimate part includes the thoughts of Cisco’s Ron Horan, Coherent’s Dr. Sanjai Parthasarathi, and Adtran’s Jörg-Peter Elbers.
Ron Horan, Vice President Product Management, Client Optics Group, Cisco
Several years ago, no one could have predicted how extensive the network infrastructure required to support artificial intelligence (AI) and machine learning (ML) back-end networks in data centres would be. This year’s OFC answered that question. In a word, immense.
By 2025, the optics total addressable market for AI/ML back-end networks is expected to equal the already substantial front-end network optics market. By 2027, the back-end network optics total addressable market is projected to significantly exceed that of the front-end network. Additionally, the adoption of higher speeds and interface densities in the AI/ML back-end network will likely surpass that of the front-end.
Last year, linear pluggable optics (LPO) advocates heralded the power and cost savings associated with removing the digital signal processor (DSP) from an optics module and driving it directly from the host ASIC. Cisco and others have shown, using data and demos, that the overall power and cost savings are significant. However, in the last year, enthusiasm for this disruptive technology has been checked as concerns about link robustness and accountability have surfaced.
Enter linear receive optics (LRO), where the transmit path gets retimed while the high-power module receiver path moves to a linear receiver, which drives directly to the host ASIC. While not as power or cost friendly as linear pluggable optics, it does reduce power and some cost from the module compared to a fully retimed module while providing some diagnostic support for the link.
Only time and significant interoperability testing will determine whether linear pluggable optics or linear receive links will be robust enough to make them deployable at scale. Additionally, today’s linear pluggable and linear receive solutions have only been shown at 100 gigabits per lane. It is unclear whether 200 gigabits per lane for both approaches can work. Many think not. If not, then 100 gigabit per lane linear pluggable and linear receive optics may be a one-generation technology that is never optimal. The LPO-MSA, an industry effort that included many of the industry’s key companies, was announced before OFC to specify and resolve interoperability and link accountability concerns.
The overall concern about reducing power in the data centre was a strong theme at the show. The linear pluggable optics/ linear receive optics theme was born from this concern. As optics, switches, routers, and GPU servers become faster and denser, data centres cannot support the insatiable need for more power.
However, end users and equipment manufacturers seek alternative ways to lower power, such as liquid cooling and immersion. Liquid cooling uses liquid-filled pipes to remove the heat, which can help cool the optics. Liquid immersion further amplifies the cooling approach by immersing the optics, along with the host switch or GPU server, directly into an inert cooling fluid or placing them just above the fluid in the vapour layer. The ultimate result is to operate the optics at a lower case temperature and save power. It seems each customer is approaching this problem differently.
Last year’s OFC produced the first optics with 200 gigabit per optical lane technology. These solutions assumed a gearbox to a host interface that used 100-gigabit electrical channels. While some early adopters will use systems and optics with this configuration, a more optimal solution using 200 gigabits per lane electrical channels between the host and optics will likely be where we see 200 gigabits per lane optics hit their stride. This year’s show revealed a broader set of optics at 200 gigabit per lane rates. The technology maturity was markedly improved from last year’s early feasibility demos.
This is an exciting time in the optics industry. I look forward to learning what technologies will be introduced at OFC 2025.
Dr. Sanjai Parthasarathi, Chief Marketing Officer, Coherent
The progress in making 200-gigabit VCSELs ready for 200-gigabit PAM-4 optical transmission was a pleasant surprise of the event.
We at Coherent presented a paper on our lithographic aperture VCSEL, while Broadcom’s presentation outlined the technical feasibility of 200-gigabit PAM4 links. While both mentioned that more work is needed, the historic success of VCSEL-based links in short-reach interconnects suggests that the arrival of 200G-capable VCSELs will significantly impact the datacom market.
The feasibility of linear pluggable optics has likely delayed the market acceptance of co-packaged optics. There seems to be widespread consensus that LPO can reduce cost and power while retaining all the advantages of pluggable transceivers – a vibrant ecosystem, deployment flexibility, and a clear distinction of link accountability.
Jörg-Peter Elbers, senior vice president, advanced technology, standards and IPR, Adtran.
At this year’s OFC, discussions were much hotter than the weather. Who would have anticipated rain, winds and chilly temperatures in an always-sunny San Diego?
AI infrastructure created the most buzz at OFC. Accelerated compute clusters for generative AI are expected to drive massive demands for high-speed interconnects inside cloud-scale data centres. Consequently, 800-gigabit, 1.6-terabit, and future 3.2-terabit pluggable optical transceivers for front-end and back-end data centre fabrics stirred a lot of interest. Progress on co-packaged optics was also exciting, yet the technology will only go into deployments where and when pluggable transceivers hit unsurmountable challenges.
Silicon Photonics, indium phosphide, thin-film lithium niobate and VCSEL-based optics compete for design slots in a very competitive intra-data centre market, leading to new partnerships across the pluggable transceiver value chain. Linear receive optics and linear transmit & receive pluggable optics offer opportunities to reduce or eliminate DSP functions where electrical signal integrity permits.
While green ICT (information and communications technology) received a lot of attention at the conference, comments at the OFC Rump Session on this topic were somewhat disenchanting: time-to-market and total-cost-of-ownership drive deployment decisions at hyperscale data centres; lower energy consumption of optics is welcome but not a sufficient driver for architectural change.
On the inter-data centre side, a range of companies announced or demonstrated 800G-ZR/ZR+ transceivers at the show. More surprising was the number of transceiver vendors – including those not traditionally active in this market domain – who have added 400G-ZR QSFP-DD transceivers to their product portfolio. This indicates that the prices of these transceivers may decline faster than anticipated.
As for the next generation, industry consensus is building up behind a single-wavelength 1.6T ZR/ZR+ ecosystem using a symbol rate of some 240 gigabaud. There was a period in which indium phosphide and silicon photonics seemed to have taken over, and LiNbO3 appeared old-fashioned. With the move to higher symbol rates, LiNbO3 – in the form of thin-film Lithium Niobate – is celebrating a comeback: “Lithium Niobate is dead – long live Lithium Niobate!”
The OIF’s largest ever interop demo impressively showed how 400G-ZR+ modules can seamlessly interoperate over long-haul distances using an open-line system optimized for best performance and user-friendly operation. Monitoring and controlling such pluggable modules in IPoWDM scenarios can create operational and organizational challenges and is the subject of ongoing debates in IETF, TIP and OIF. A lean demarcation unit device can be a pragmatic solution to overcome these challenges in the near term. In the access/aggregation domain, the interest in energy-efficient 100G-ZR solutions keeps growing.
As the related OFC workshop showed, growing is also the support for a coherent single-carrier PON solution as the next step in the PON roadmap after 50Gbps very high-speed PON (VHSP).
Overall, there was excitement and momentum at OFC, with the conference and show floor returning to pre-Covid levels.
This is a good basis for the 50th anniversary edition of ECOC, taking place in Frankfurt, Germany, on September 22-26, 2024.
ECOC 2023 industry reflections - Final Part
Gazettabyte has been asking industry figures to reflect on the recent ECOC show in Glasgow. The final instalment emphasises coherent technology with contributions from Adtran, Cignal AI, Infinera, Ciena, and Acacia.
Jörg-Peter Elbers, head of advanced technology at Adtran
The ECOC 2023 conference and show was a great event. The exhibition floor was busy and offered ample networking opportunities. In turn, the conference and the Market Focus sessions provided information on the latest technologies, products, and developments.
One hot topic was coherent 800ZR modems. Several vendors demonstrated coherent 800ZR modules and related components. Importantly, these modules also boast new and improved 400 gigabit-per-second (Gbps) modes. The 120 gigabaud (GBd) symbol rate enables 400-gigabit dual-polarisation quadrature phase shift keying (DP-QPSK) transmission over demanding links and long-haul routes. In turn, the advent of 5nm CMOS digital signal processor (DSP) technology enables lower power DP-16QAM than 400ZR modules.
There is broad agreement that the next step in coherent transmission is a 240GBd symbol rate, paving the way to single-wavelength 1.6 terabit-per-second (Tbps) optical transport.
Meanwhile, the use of coherent optical technology closer to the network edge continues. Several players announced plans to follow Adtran and Coherent and jump on the low-power 100 gigabit-per-second ZR (100ZR) ‘coherent lite’ bandwagon. Whether passive optical networking (PON) systems will adopt coherent technology after 50G-PON sparked lively debate but no definitive conclusions.
The OIF 400ZR+ demonstration showed interoperability between a dozen optical module vendors over metro-regional distances. It also highlighted the crucial role of an intelligent optical line system such as Adtran’s FSP3000 OLS in automating operation and optimising transmission performance.
The post-deadline papers detailed fibre capacity records by combining multiple spectral bands and multiple fibre cores. The line-system discussions on the show floor focused on the practical implications of supporting C-, L-, extended, and combined band solutions for customers and markets.
From workshops to the regular sessions, the application of artificial intelligence (AI) was another prominent theme, with network automation a focus area. Examples show not only how discriminative AI can detect anomalies or analyse failures but also how generative AI can improve the interpretation of textual information and simplify human-machine and intent interfaces. For network engineers, ‘Copilot’-like AI assistance is close.
After ECOC is also before ECOC, so please mark in your calendars September 22-26, 2024. ECOC will celebrate its 50th anniversary next year and will take place in Frankfurt, Germany. As one of the General Chairs of the ECOC 2024 event, and on behalf of the entire organising committee, I look forward to welcoming you!
Andrew Schmitt, founder and directing analyst, Cignal AI
ECOC is a great show, it’s like OFC (the annual optical communications and networking event held in the US) but refined to only the critical elements. Here are my key takeaways.
The most impressive demonstration was 800ZR test boards and modules from Marvell and its partners Coherent and Lumentum. Within eight weeks of the first silicon, Marvell has demos up and running in-house and at its partners. The company has at least a 6-month lead in the 800ZR market, making intelligent tradeoffs to achieve this.
Lumentum showed an 8-QAM mode of operation that allows 800 gigabit transmission within a 100GHz channel spacing, which should be interesting. After the massive success of 400ZR, it’s natural to extrapolate the same success for 800ZR, but the use cases for this technology are substantially different. We also heard updates and broader support for 100ZR.
Linear drive pluggable optics (LPO) was a hot topic, although it was our impression that, while optimism ruled public discussion, scepticism was widely expressed in private. There was more agreement than disagreement with our recent report (see the Active Insight: The Linear Drive Market Opportunity). No one is more confident about LPO than the companies who view this as another opportunity to bid for business at hyperscale operators they don’t currently have.
The 200 gigabit per lane silicon/ physical media device (PMD)/ optics development continues, and it is on track to enable 1.6-terabit optics by 2024. Marvell had a more advanced and mature demo of what they showed behind closed doors at OFC. The advancements here are the real threat to adopting LPO, and people need to realise that LPO is competing with the power specs of 200 gigabits per lane, not 100 gigabits per lane solutions.
Also impressive was the comprehensive engineering effort by Eoptolink to show products that covered 100 gigabit and 200 gigabit per lane solutions, both retimed and linear. The company’s actions show that if you have the engineering resources and capital, rather than pick the winning technology, do everything and let the market decide. Also impressive is the CEO, who understood the demos and the seasoned application engineers. Kudos to keeping engaged with the products!
System vendors had a more significant presence at the show, particularly Ciena and Infinera. It’s unsurprising to see more system vendors since they are increasing investments in pluggables, particularly coherent pluggables.
We had many discussions about our forecasts for IPoDWDM deployment growth. This disruption is something that component vendors are excited about, and hardware OEMs view it as an opportunity to adjust how they deliver value to operators (see the Active Insight: Assessing the Impact of IP-over DWDM).
Lastly, the OIF coordinated 400ZR+ and OpenROADM interoperability testing despite the organisation not being directly involved in those industry agreements. The OIF is a fantastic organisation that gets valuable things done that its members need.
Paul Momtahan, director, solutions marketing, Infinera
ECOC 2023 provided an excellent opportunity to catch the latest trends regarding transponder innovation, coherent pluggables and optical line systems. A bonus was getting to the show without needing a passport.
Transponder innovation topics included coherent digital signal processor (DSP) evolution, novel modulators, and the maximum possible baud rate. DSP sessions included the possibility of offloading DSP functions into the photonic domain to reduce power consumption and latency.
There were also multiple presentations on constellation shaping, including enhanced nonlinear performance, reduced power consumption for probabilistic constellation shaping, and potential uses for geometric shaping.
Novel modulators with very high baud rates, including thin-film lithium niobate, barium titanate, plasmonic, and silicon-organic hybrid, were covered. The need for such modulators is the limited bandwidth potential of silicon photonics modulators, though each face challenges such as integration with silicon photonics and manufacturability.
From the baud rate session, the consensus was that 400GBd symbol rates are probable, up to 500GBd might be possible, but higher rates are unlikely. The critical challenges are the radio frequency (RF) interconnects and the digital-to-analogue and analogue-to-digital converters. However, several presenters wondered whether a multi-wavelength transponder might be more sensible for symbol rates above 200 to 250GBd.
Coherent pluggables were another topic, especially at 800 gigabit. However, one controversial topic was the longevity of coherent pluggables in routers (IPoDWDM). Several presenters argued the current period would pass once router port speeds and coherent port speeds no longer align.
As the coherent optical engines approach the Shannon limit, innovation is shifting towards optical line systems and fibres as alternative way to scale capacity.
Several presentations covered ROADM evolution to 64 degrees and even 128 degrees. A contrasting view is that ROADMs’ days are numbered to be replaced by fibre switches and full spectrum transponders, at least in core networks.
Additional options for scaling capacity included increasing the spectrum of existing bands with super-C and super-L. Lighting different bands, such as the S-band (in addition to C+L bands), is seen as the best candidate, with commercial solutions three to five years away.
Overall, it was a great event, and I look forward to seeing how things evolve by the time of next year’s ECOC show in Frankfurt. (For more, click here)
Helen Xenos, senior director, portfolio marketing, Ciena
This was my third year attending ECOC, and the show never disappoints. I always leave this event excited and energised about what we’ve accomplished as an industry.
Every year seems to bring new applications and considerations for coherent optical technology. This year, ECOC showcased the ever-growing multi-vendor ecosystem for 400-gigabit coherent pluggable transceivers, considerations in the evolution to 800-gigabit pluggables, evolution to coherent PON, quantum-secure coherent networking, and the evolution to 200 gigabaud and beyond. When will coherent technology make it into the data centre? A question still open for debate.
Ciena’s optical engineer wizards were on hand to share specifics about our recently announced 3nm CMOS-based WaveLogic 6 technology, which includes the industry’s first performance-optimised 1.6 teraburs-per-second (Tbps) optics as well as 800-gigabit pluggables.
It was exciting for me to introduce customers, suppliers and research graduates to their first view of 3nm chip performance results and show how these enable the next generation of products. And, of course, Ciena was thrilled that WaveLogic 6 was awarded the Most Innovative Coherent Module Product at the event.
Tom Williams, director of technical marketing at Acacia
From my perspective, while there weren’t as many major product announcements as OFC, several trends and technologies continued to progress, including OIF interoperability, 800ZR/ZR+, linear pluggable optics (LPO) and terabit optics.
The OIF interop demonstration was once again a highlight of the show. The booth was at the entrance to the exhibition and seemed to be packed with people each time I passed by.
OIF has expanded the scope of these demonstrations with each show, and this year was the largest ever. In addition to having the participation of 12 module vendors (with 34 modules), the focus was on the ZR+ operation. What was successfully demonstrated was a single-span 400ZR network and a multi-span network.
As co-chair of the OpenZR+ MSA, I was excited by the great collaboration with OIF. These efforts help to drive the industry forward. Karl Gass is not only the most creatively dressed person at every trade show; he is exceptional at coordinating these activities.
It is clear that linear drive pluggable optics (LPO) works in some situations, but views differ about how widespread its adoption will be and how standardisation should be addressed. I lived through the analogue coherent optics (ACO) experience. ACO was essentially a linear interface for a coherent module where the digital processing happened outside the module. For ACO, it was a DSP on the host board and for LPO it is the switch ASIC. The parameters that need to be specified are similar. There is a precedent for this kind of effort. Hopefully, lessons learned there will be helpful for those driving LPO. I am interested to see how this discussion progresses in the industry as some of the challenges are discussed, such as its current limited interoperability and support for 200 gigabits per lane.
There have been announcements from several companies about performance-optimised coherent optics in what we call Class 3 (symbol rates around 140 gigabaud), which support up to 1.2 terabits on a wavelength. Our CIM 8 module has been used in multiple field trials, demonstrating the performance benefits of these solutions.
Our CIM 8 (Coherent Interconnect Module 8) achieves this performance in a pluggable form factor. The CIM 8 uses the same 3D siliconisation technology we introduced for our 400-gigabit pluggables and enables operators to scale their network capacity in a cost- and power-efficient way.
ECOC '22 Reflections - Final Part
Gazettabyte has been asking industry and academic figures for their thoughts after attending ECOC 2022, held last month in Basel, Switzerland. In particular, what developments and trends they noted, what they learned, and what, if anything, surprised them.
In the final part, Dr. Sanjai Parthasarathi of Coherent, Acacia’s Tom Williams, ADVA’s Jörg-Peter Elbers and Fabio Pittalà of Keysight Technologies share their thoughts.
Dr. Sanjai Parthasarathi, Chief Marketing Officer, Coherent
The ECOC event represents an excellent opportunity for us – a vertically-integrated manufacturer selling at all levels of the value chain – to meet with customers, end-customers and partners/ suppliers.
There was a refreshing sense of optimism and excitement for optical communications, driven by relentless bandwidth growth, despite the macroeconomic backdrop.
The roadmap for optical transceivers is dictated by the electrical interface used for Ethernet switch chips. We have seen that play out yet again for 100-gigabit electrical lanes used for 25-terabit and 50-terabit Ethernet switches.
Several transceiver suppliers demonstrated products with 100 gigabit-per-lane electrical interfaces in quad and octal form factors. The optical lane of a transceiver typically begins at the same speed as the electrical lane and then progresses to a faster rate. This transition should be expected for 800-gigabit transceivers as well.
While 100 gigabit-per-lane transceivers, such as the 800G-DR8 and the 2x400G-FR4 devices, there were devices demonstrated that enable the transition to optical 200-gigabit lanes. It was satisfying to see a warm response for the demonstration of Coherent’s 200-gigabit electro-absorption modulated laser (EML) and Semtech’s 200-gigabit EML driver. I am confident that direct detection will play a predominant role in 800-gigabit and 1.6-terabit data centre links.
Despite the great interest in co-packaged optics, nearly all the working demonstrations at the show used pluggable transceiver modules. Industry colleagues are preparing for pluggable transceiver modules using the next 200-gigabit electrical interface. Indeed, at ECOC, there was an OIF-CEI 224G demo by Keysight and Synopsys.
One key topic at the show concerned whether ‘coherent lite’ or direct detect is the preferred solution for data centres and edge aggregation. The debate remains open and no one solution fits all. It will depend on the specific application and architecture. A broad portfolio supported by different technology platforms frees you to select the best approach to serve the customer’s needs.
I saw the industry responding to the need for disaggregation and innovative solutions for access and telecom. Coherent’s 100G ZR announcement is one such example, as well as the extra performance of high-power 400ZR+ coherent transceivers.
We started this trend and we now see others announcing similar solutions.
Arista’s demo, which featured 400ZR connections over a 120km data centre interconnect (DCI) link, enabled by our pluggable optical line system in a QSFP form factor, received much attention and interest.
Tom Williams, Senior Director of Marketing for Acacia, now part of Cisco.
Many of us are still of a mindset where any opportunity to get together and see industry friends and colleagues is a great show.
My focus is very much on the success of 400-gigabit pluggable coherent solutions.
We’ve been talking about these products for a long time, back to the initial OIF 400ZR project starting in late 2016. Since then, 400ZR/ZR+ has been a hot topic at every conference.
The commercial success of these solutions, and the impact that they’re having on network architectures, has been gratifying. These products have ramped in volumes not seen by any previous coherent technology.
The industry has done a great job at 400 gigabits, striking the right balance of power and performance. Now, we’re looking at 800 gigabits and working through some of the same questions. Discussions around 1.6 terabits have even started.
Much work is still required but what we heard from customers at ECOC is that the trend toward pluggable coherent will likely continue.
Jörg-Peter Elbers, Senior Vice President, Advanced Technology, Standards and IPR at ADVA
‘Never say never’ captures well ECOC’s content. There was no one groundbreaking idea but topics discussed in the past are back on the agenda, either because of a need or the technology has progressed.
Here are several of my ECOC takeaways:
- The 130 gigabaud (GBd) class of coherent optics is coming, and the generation after that – 240GBd – is on the horizon.
- Coherent optics continue to push towards the edge. Will there be a Very-High Speed Coherent PON after 50G High-Speed PON?
- Whether co-packaged optics or front-pluggable modules, electro-photonic integration is rapidly advancing with some interesting industry insights shared at the conference.
- Quantum-safe communication is becoming part of the regular conference program.
- Optical Satcom is gaining traction. Optical ground-to-space links are promising yet challenging.
Fabio Pittalà, Product Planner, Broadband and Photonics – Center of Excellence, Keysight Technologies
This was my first ECOC as an employee of Keysight. I spent most of my time at the exhibition introducing the new high-speed Keysight M8199B Arbitrary Waveform Generator.
There were a lot of discussions focusing on technologies enabling the next Ethernet rates. There is a debate about intensity-modulation direct detection (IMDD) versus coherent but also what modulation format, symbol rate or degree of parallelisation.
While the industry is figuring out the best solution, researchers achieved important milestones by transmitting the highest symbol rate and the highest net bitrate.
Nokia Bell-Labs demonstrated record-breaking transmission of 260-gigabaud dual-polarisation quadrature phase-shift keying (DP-QPSK) over 100km single-mode fibre.
Meanwhile, NTT broke the net bitrate record by transmitting more than 2 terabit-per-second using a probabilistic-constellation-shaped dual-polarisation quadrature amplitude modulation (DP-QAM) over different data centre links.
ADVA adds quantum-resistant security to its optical systems
ADVA has demonstrated two encryption techniques for optical data transmission to counter the threat posed by quantum computing.
“Quantum computers are very powerful tools to solve specific classes of mathematical problems,” says Jörg-Peter Elbers, senior vice president, advanced technology at ADVA. “One of these classes of problems is solving equations behind certain cryptographic schemes.”
The use of three key exchange schemes over one infrastructure: classical public-key encryption using the Diffie-Hellman scheme, the quantum-resistant Neiderreiter algorithm, and a quantum-key distribution (QKD) scheme. Source: ADVA
Public-key encryption makes use of discrete logarithms, an example of a one-way function. Such functions use mathematical operations that for a conventional computer are easy to calculate in one direction but are too challenging to invert. Solving such complex mathematical problems, however, is exactly what quantum computers excel at.
A fully-fledged quantum computer does not yet exist but the rapid progress being made in the basic technologies suggests it is only a matter of time. Once such computers exist, public key based security will be undermined.
The looming advent of quantum computers already threatens data that must remain secure for years to come. There are agencies that specialise in tapping fibre, says Elbers, while the cost of storage is such that storing huge amounts of data traffic in a data centre is affordable. “The threat scenario is certainly a real one,” says Elbers.
Demonstrations
ADVA has demonstrated two techniques, one using quantum-key distribution (QKD) and the other a quantum-resistant algorithm.
For quantum-key distribution, ADVA’s FSP 3000 platform is being used as part of the UK’s first quantum communication network that includes a metro network for Cambridge that is also linked to BT Labs in Ipswich, 120km away.
ADVA’s platform enables the exchange of keys between sites used for encoding the data traffic. In the Cambridge metro, a quantum system from Toshiba is used to encode the keys while between Cambridge and BT Labs the equipment used is from ID Quantique.
The threat scenario is certainly a real one
For ADVA’s second demonstration, a quantum-resistant encryption algorithm - one invulnerable to quantum computing attacks - is incorporated into its FSP-3000 platform to encrypt 100 gigabit-per-second traffic flows over long-haul distances. ADVA has shown secure transmissions over 2,800km, spanning three European national research and educational networks.
“There is never 100 percent security in one system but you can increase security using multiple independent systems,” says Elbers. “You can use your classical encryption methods in use today and add quantum-key distribution or a quantum-resistant algorithm or use all three over one infrastructure.” (See diagram, top.)
Quantum key distribution
Public key cryptography, comprising a public and a private key pair, is an example of an asymmetric key scheme. The public key, as implied by the name, is published with a recipient’s name. Any party wanting to send data securely to the user employs the published public key to scramble the data. Only the recipient, with the associated private key, can decode the sent data. The Diffie-Hellman algorithm is a widely used public key encryption scheme.
Jörg-Peter ElbersWith a symmetric scheme, the same key is used at both ends to lock and unlock the data. A well-known symmetric key algorithm is the Advanced Encryption Standard. AES-256, for example, uses a 256-bit key.
Although being much more efficient than asymmetrical algorithms, the issue with the symmetrical scheme is getting the secret key to the recipient without it being compromised. The key can be sent manually with armed guards. A more practical approach is to send the key over a secure link using public key cryptography; the asymmetric key exchange scheme protects the transmission of the symmetric key used for the subsequent encryption of the payload.
Quantum computing is a potent threat because it undermines all asymmetric encryption schemes in widespread use today.
Quantum key distribution, which uses particles of light or photons, is a proposed way to secure the symmetric key’s transfer. Here, single photons are used to transmit a binary signal that is then used to generate the same secret key at both ends. Should an adversary eavesdrop with a photo-detector and steal the photon, the photon will not arrive at the other end. Should the hacker be more sophisticated and try to measure the photon before sending it on, they are stymied by the laws of physics since measuring a photon changes its parameters.
Given these physical properties of photons, the sender and receiver can jointly detect a potential eavesdropper. If the number of missing or altered photons is too high, the assumption is the link is compromised.
But with quantum key distribution, the distance a photon can travel is a few tens of kilometres only. A photon is inherently low-intensity light. For longer transmission distances, intermediate trusted sites are required to regenerate the key exchange along the way. BT uses two such trusted sites on the link between Cambridge and BT Labs.
ADVA along with Toshiba have been working on an open interface that allows secure quantum key distribution over a dense wavelength division multiplexing (DWDM) link, independent of the systems used. Having an open interface also means operators using different quantum key distribution systems can interoperate and chat, says Elbers.
The US National Institute of Science and Technology (NIST) is assessing candidate quantum-resistant algorithms with the goal of standardising a suite of protocols by 2024
One way to enable single-photon streams is to use a dedicated fibre. But to avoid the expense of a separate fibre, ADVA sends the photons over a dedicated channel alongside the data transmission channels that carry much higher intensity light.
“Ideally you want a single quantum but, in practice, you might work with a highly attenuated laser source that emits less than a single quantum on average,” says Elbers. “Everything you have on your co-propagating channels can impact the performance.” ADVA uses optical filtering to ensure the data channels don’t spill over and adversely affect the key’s transfer.
Quantum-resistant algorithms
The second approach uses maths rather than fundamental physics to make data encryption invulnerable to quantum computing. The result is what is referred to as quantum-resistant techniques.
The US National Institute of Science and Technology (NIST) is assessing candidate quantum-resistant algorithms with the goal of standardising a suite of protocols by 2024.
The maths behind these schemes is complicated but what unifies them is that none are based on the mathematical problems susceptible to known quantum computing attacks.
ADVA uses the Niederreiter key exchange algorithm, one of NIST’s candidate schemes, for its system. To ensure the highest level of security for high-speed optical transmission a new symmetric key is sent frequently. The Neiderreiter algorithm uses comparatively long key lengths but Elbers points out that with a 100-gigabit payload, the overhead of long keys is minimal. Moreover, ADVA communicates key exchange information in the Optical Transport Network’s (OTN) OTU-4 frame’s overhead field.
Customers are already showing interest in quantum security, says Elbers, and is one of the reasons why ADVA is active in the UK’s Quantum Communications Hub initiative. “We are showing people that the technology is here, ready for deployment and can be integrated with existing systems,” says Elbers.
For organisations keen to ensure the long-term secrecy of their data, they need to be considering now what they should be doing to address this, he adds.
Meeting the many needs of data centre interconnect
High capacity. Density. Power efficiency. Client-side optical interface choices. Coherent transmission. Direct detection. Open line system. Just some of the requirements vendors must offer to compete in the data centre interconnect market.
“A key lesson learned from all our interactions over the years is that there is no one-size-fits-all solution,” says Jörg-Peter Elbers, senior vice president of advanced technology, standards and IPR at ADVA Optical Networking. “What is important is that you have a portfolio to give customers what they need.”
Jörg-Peter Elbers
Teraflex
ADVA Optical Networking detailed its Teraflex, the latest addition to its CloudConnect family of data centre interconnect products, at the OFC show held in Los Angeles in March (see video).
The platform is designed to meet the demanding needs of the large-scale data centre operators that want high-capacity, compact platforms that are also power efficient.
A key lesson learned from all our interactions over the years is that there is no one-size-fits-all solution
Teraflex is a one-rack-unit (1RU) stackable chassis that supports three hot-pluggable 1.2-terabit modules or ‘sleds’. A sled supports two line-side wavelengths, each capable of coherent transmission at up to 600 gigabits-per-second (Gbps). Each sled’s front panel supports various client-side interface module options: 12 x 100-gigabit QSFPs, 3 x 400-gigabit QSFP-DDs and lower speed 10-gigabit and 40-gigabit modules using ADVA Optical Networking’s MicroMux technology.
“Building a product optimised only for 400-gigabit would not hit the market with the right feature set,” says Elbers. “We need to give customers the possibility to address all the different scenarios in one competitive platform.”
The Teraflex achieves 600Gbps wavelengths using a 64-gigabaud symbol rate and 64-ary quadrature-amplitude modulation (64-QAM). ADVA Optical Networking is using Acacia’s Communications latest Pico dual-core coherent digital signal processor (DSP) to implement the 600-gigabit wavelengths. ADVA Optical Networking would not confirm Acacia is its supplier but Acacia decided to detail the Pico DSP at OFC because it wanted to end speculation as to the source of the coherent DSP for the Teraflex. That said, ADVA Optical Networking points out that Teraflex’s modular nature means coherent DSPs from various suppliers can be used.
The 1 rack unit Teraflex
The line-side optics supports a variety of line speeds – from 600Gbps to 100Gbps, the lower the speed, the longer the reach.
The resulting 3-sled 1RU Teraflex platform thus supports up to 3.6 terabits-per-second (Tbps) of duplex communications. This compares to a maximum 800Gbps per rack unit using the current densest CloudConnect 0.5RU Quadflex card.
Markets
The data centre interconnect market is commonly split into metro and long haul.
The metro data centre interconnect market requires high-capacity, short-haul, point-to-point links up to 80km. Large-scale data centre operators may have several sites spread across a city, given they must pick locations where they can find them. Sites are typically no further apart than 80km to ensure a low-enough latency such that, collectively, they appear as one large logical data centre.
“You are extending the fabric inside the data centre across the data-centre boundary, which means the whole bandwidth you have on the fabric needs to be fed across the fibre link,” says Elbers. “If not, then there are bottlenecks and you are restricted in the flexibility you have.”
Large enterprises also use metro data centre interconnect. The enterprises’ businesses involve processing customer data - airline bookings, for example - and they cannot afford disruption. As a result, they may use twin data centres to ensure business continuity.
Here, too, latency is an issue especially if synchronous mirroring of data using Fibre Channel takes place between sites. The storage protocol requires acknowledgement between the end points such that the round-trip time over the fibre is critical. “The average distance of these connections is 40km, and no one wants to go beyond 80 or 100km,” says Elbers, who stresses that this is not an application for Teraflex given it is aimed at massive Ethernet transport. Customers using Fibre Channel typically need lower capacities and use more tailored solutions for the application.
The second data centre interconnect market - long haul - has different requirements. The links are long distance and the data sent between sites is limited to what is needed. Data centres are distributed to ensure continual business operation and for quality-of-experience by delivering services closer to customers.
Hundreds of gigabits and even terabits are sent over the long-distance links between data centres sites but commonly it is about a tenth of the data sent for metro data centre interconnect, says Elbers.
Direct Detection
Given the variety of customer requirements, ADVA Optical Networking is pursuing direct-detection line-side interfaces as well as coherent-based transmission.
At OFC, the system vendor detailed work with two proponents of line-side direct-detection technology - Inphi and Ranovus - as well as its coherent-based Teraflex announcement.
Working with Microsoft, Arista and Inphi, ADVA detailed a metro data centre interconnect demonstration that involved sending 4Tbps of data over an 80km link. The link comprised 40 Inphi ColorZ QSFP modules. A ColorZ module uses two wavelengths, each carrying 56Gbps using PAM-4 signalling. This is where having an open line system is important.
Microsoft wanted to use QSFPs directly in their switches rather than deploy additional transponders, says Elbers. But this still requires line amplification while the data centre operators want the same straightforward provisioning they expect with coherent technology. To this aim, ADVA demonstrated its SmartAmp technology that not only sets up the power levels of the wavelengths and provides optical amplification but also automatically measures and compensates for chromatic dispersion experienced over a link.
ADVA also detailed a 400Gbps metro transponder card based on PAM-4 implemented using two 200Gbps transmitter optical subassemblies (TOSAs) and two 200Gbps receiver optical subassemblies (ROSAs) from Ranovus.
Clearly there is also space for a direct-detection solution but that space will narrow down over time
Choices
The decision to use coherent or direct detection line-side optics boils down to a link’s requirements and the cost an end user is willing to pay, says Elbers.
As coherent-based optics has matured, it has migrated from long-haul to metro and now data centre interconnect. One way to cost-reduce coherent further is to cram more bits per transmission. “Teraflex is adding chunks of 1.2Tbps per sled which is great for people with very high capacities,” says Elbers, but small enterprises, for example, may only need a 100-gigabit link.
“For scenarios where you don’t need to have the highest spectral efficiency and the highest fibre capacity, you can get more cost-effective solutions,” says Elbers, explaining the system vendor’s interest in direct detection.
“We are seeing coherent penetrating more and more markets but still cost and power consumption are issues,” says Elbers. “Clearly there is also space for a direct-detection solution but that space will narrow down over time.”
Developments in silicon photonics that promise to reduce the cost of optics through greater integration and the adoption of packaging techniques from the CMOS industry will all help. “We are not there yet; this will require a couple of technology iterations,” says Elbers.
Until then, ADVA’s goal is for direct detection to cost half that of coherent.
“We want to have two technologies for the different areas; there needs to be a business justification [for using direct detection],” he says. “Having differentiated pricing between the two - coherent and direct detection - is clearly one element here.”
OpenFlow extends its control to the optical layer
"We see OpenFlow as an additional solution to tackle the problem of network control"
Jörg-Peter Elbers, ADVA Optical Networking
The largest data centre players have a single-mindedness when it comes to service delivery. Players such as Google, Facebook and Amazon do not think twice about embracing and even spurring hardware and software developments if they will help them better meet their service requirements.
Such developments are also having a wider impact, interesting traditional telecom operators that have their own service challenges.
The latest development causing waves is the OpenFlow protocol. An open standard, OpenFlow is being developed by the Open Networking Foundation, an industry body that includes Google, Facebook and Microsoft, telecom operators Verizon, NTT and Deutsche Telekom, and various equipment makers.
OpenFlow is already being used by Google, and falls under the more general topic of software-defined networking (SDN). A key principle underpinning SDN is the separation of the data and control planes to enable more centralised and simplified management of the network.
OpenFlow is being used in the management of packet switches for cloud services. "The promise of software-defined networking and OpenFlow is to give [data centre operators] a virtualised network infrastructure," says Jörg-Peter Elbers, vice president, advanced technology at ADVA Optical Networking.
The growing interest in OpenFlow is reflected in the activities of the telecom system vendors that have extended the protocol to embrace the optical layer. But whereas the content service provider giants need only worry about tailoring their networks to optimise their particular services, telecom operators must consider legacy equipment and issues of interoperability.
OFELIA
ADVA Optical Networking has started the ball rolling by running an experiment to show OpenFlow controlling both the optical and packet layers of the network. Until now the protocol, which provides a software-programmable interface, has been used to manage packet switches; the adding of the optical layer control is an industry first, the company claims.
The OpenFlow demonstration is part of the European “OpenFlow in Europe, Linking Infrastructure and Applications” (OFELIA) research project involving ADVA Optical Networking and the University of Essex. A test bed has been set up that uses the ADVA FSP 3000 to implement a colourless and directionless ROADM-based optical network.
"We have put a network together such that people can run the optical layer through an OpenFlow interface, as they do the packet switching layer, under one uniform control umbrella," says Elbers. "The purpose of this project is to set up an experimental facility to give researchers access to, and have them play with, the capabilities of an OpenFlow-enabled network."
"The fact that Google is doing it [SDN] is not a strong indication that service providers are going to do it tomorrow"
Mark Lutkowitz, Telecom Pragmatics
Remote researchers can access the test bed via GÉANT, a high-bandwidth pan-European backbone connecting national research and education networks.
ADVA Optical Networking hopes the project will act as a catalyst to gain useful feedback and ideas from the users, leading to further developments to meet emerging requirements.
OpenFlow and GMPLS
A key principle of SDN, as mentioned, is the separation of the data plane from the control plane. "The aim is to have a more unified control of what your network is doing rather than running a distributed specialised protocol in the switches," says Elbers.
That is not that much different from the Generalized Multi-Protocol Label Switching (GMPLS), he says: "With GMPLS in an optical network you effectively have a data plane - a wavelength switched data plane - and then you have a unified control plane implementation running on top, decoupled from the data plane."
But clearly there are differences. OpenFlow is being used by data centre operators to control their packet switches and generate packet flows. The goal is for their networks to gain flexibility and agility: "A virtualised network that can be run as you, the user, want it," said Elbers.
But the protocol only gives a user the capability to manage the forwarding behavior of a switch: an incoming packet's header is inspected and the user can program the forwarding table to determine how the packet stream is treated and the port it goes out on.
And while OpenFlow has since been extended to cater for circuit switches as well as wavelength circuits, there are aspects at the optical layer which OpenFlow is not designed to address - issues that GMPLS does.
To run end-to-end, the control plane needs to be aware of the blocking constraints of an optical switch, while when provisioning it must also be aware of such aspects as the optical power levels and optical performance constraints. "The management of optical is different from managing a packet switch or a TDM [circuit switched] platform," says Elbers. “We need to deal with transmission impairments and constraints that simply do not exist inside a packet switch.”
That said, having GMPLS expertise, it is relatively simple for a vendor to provide an OpenFlow interface to an optical controlled network, he says: "We see OpenFlow as an additional solution to tackle the problem of network control."
Operators want mature and proven interoperable standards for network control, that incorporate all the different network layers and that use GMPLS.
"We are seeing that in the data centre space, the players think that they may not have to have that level of complexity in their protocols and can run something lower level and streamlined for their applications," says Elbers.
While operators see the benefit of OpenFlow for their own data centres and managed service offerings, they also are eyeing other applications such as for access and aggregation to allow faster service mobility and for content management, says Elbers.
ADVA Optical Networking sees the adding of optical to OpenFlow as a complementary approach: the integration of optical networking into an existing framework to run it in a more dynamic fashion, an approach that benefits the data centre operators and the telcos.
"If you have one common framework, when you give server and compute jobs then you know what kind of connectivity and latency needs to go with this and request these resources and reconfigure the network accordingly," says Elbers.
But longer term the impact of OpenFlow and SDN will likely be more far-reaching: applications themselves could program the network, or it could be used to enable dial-up bandwidth services in a more dynamic fashion. "By providing software programmability into a network, you can develop your own networking applications on top of this - what we see as the heart of the SDN concept," says Elbers. “The long term vision is that the network will also become a virtualised resource, driven by applications that require certain types of connectivity.”
Providing the interface is the first step, the value-add will be the things that players do with the added network flexibility, either the vendors working with operators, or by the operators' customers and by third-party developers.
"This is a pretty significant development that addresses the software side of things," says Elbers, adding that software is becoming increasingly important, with OpenFlow being an interesting step in that direction.
100 Gigabit for the metro
The firm claims this is an industry first: a direct-detection-based 100 Gigabit-per-second (Gbps) design using four, 28Gbps channels rather than current 10x10Gbps schemes.
"Data centre operators want to make best use of the fibre insfrastructure and get lower overall cost, footprint and power consumption"
Jörg-Peter Elbers, ADVA Optical Networking
The card, designed for the FSP 3000 platform, delivers a 2.5x greater spectral efficiency compared to 10Gbps dense WDM (DWDM) systems. In turn, the 100Gbps metro card has half the cost of a 100 Gigabit coherent design while requiring half the power and space.
ADVA Optical Networking is using a CFP optical module to implement the 100Gbps metro design. This allows the card to use other CFP-based interfaces such at the IEEE 100 Gigabit Ethernet (GbE) standards. The design also benefits from the economies of scale of the CFP as the module of choice for 100GbE, and from future smaller modules such as the CFP2 and CFP4 being developed as the 100GbE market evolves.
The 100Gbps metro CFP's four, 28Gbps signals are modulated using optical duo-binary. By choosing duo-binary, cheaper 10Gbps optics can be used akin to a 4x10Gbps design. Duo-binary is also more resilient to dispersion than standard on-off keying.
The CFP-based card requires 200GHz of spectrum for each 100Gbps light path. This is 2.5x more spectrally efficient than 10x10Gbps based on 50GHz channel spacings. However, while the design is cheaper, denser and less power hungry than 100Gbps coherent, it has only a quarter of the spectral efficiency of coherent (see chart).
Jörg-Peter Elbers, vice president, advanced technology at ADVA Optical Networking, says duo-binary delivers closer channel spacing such that a doubling in spectral density will be possible in a future design (100Gbps in a 100GHz channel). The 100Gbps metro card supports 500km links using dispersion-compensated fibre.
Non-coherent designs for the metro are starting to appear despite 100Gbps optical transport being in its infancy. Besides ADVA Optical Networking's design, a component vendor is promoting a 100Gbps direct detection DWDM design for the metro. The 10x10 MSA has also announced a DWDM extension that will support four and eight 100Gbps channels.
The 100G metro card showing the CFP. Source: ADVA Optical Networking
Metro direct-detection also faces competition from system vendors developing coherent designs tailored for the metro.
System vendors, module makers, optical and IC component companies all believe there is a market for lower cost 100Gbps metro transport. This is backed by keen interest from service providers and large content providers that want cheaper 100Gbps interfaces to connect data centres.
Elbers highlights two such applications that will first likely use the 100 Gigabit metro card.
One is connecting the data centres of enterprises that use rented fibre. "They have a multitude of interfaces and services - 10GbE, 8 Gigabit Fibre Channel - and they often rent fibre," says Elbers. "They need to get as much capacity as possible to make the fibre rent worthwhile while being constrained on rack space and power."
The second application is to connect 100GbE-enabled IP routers across the metro. Here service providers may not have heavily loaded DWDM networks and can afford to use a 100Gbps metro link rather than the more spectrally efficient, if more expensive, 100Gbps coherent interface. Equally, such links may be less than 500km while coherent is designed for long-haul links, 1000km or greater.
Elbers says samples of the metro card are available now with volume production beginning at the end of 2011.
Introducing 100G Metro (ADVA Optical video)