Books of 2024: Final Part
Gazettabyte has been asking industry figures to pick their reads of 2024. In the final part, Professor Polina Bayvel, Hojjat Salemi, Professor Laura Lechuga, and the editor of Gazettabyte share their selections.
Professor Polina Bayvel, Royal Society Research Professor & Head of the Optical Networks Group, Department of Electronic & Electrical Engineering, UCL
I recently attended a Royal Society Discussion Meeting where Leslie Valiant gave a brilliant talk on educability as a better definition than intelligence. A Harvard professor, he has developed many algorithms that underpin today’s networks, including Valiant’s load balancing. He is a profound thinker, and I wanted immediately to read his book, The Importance of Being Educable: A New Theory of Human Uniqueness.’
Although written in a popular style, it argues that educability (a precisely defined computational model) is a better term than intelligence, for which no agreed definition exists. He explains how we, as a human race, have been able to create the technological civilisation that we have and argues that this civilisation enabler is educability. He also implies that current AI models are not educable. The book is masterful in its lucidity in explaining complex concepts in computation. I really could not put it down.
Another read which has taken my breath away is A. N. Tolstoy’s The Road to Calvary (Russian: Хождение по мукам, romanised: Khozhdeniye po mukam, lit. ’Walking Through Torments’), also translated as Ordeal, is a trilogy set just before the Russian Revolution (starting 1914) and follows the lives of two sisters and their lovers/ husbands goes through the revolution and the Russian Civil War. It was a staple in Soviet schools, but leaving at age 12, I missed it and have only recently read it.
It’s a monument to history, and when one reads it, one realises that the well-to-do Russian liberals who argued for change and the removal of the Czarist rules had no idea what fate would face them or how their lives would change forever.
It made me think of today’s parallel – do we always understand the consequences of wanting liberal changes? The Russian pre-Revolution liberals, the intelligentsia, wanted democracy and more power for the people. What they got was the opposite – totalitarian oppression.
I was also struck by the stark realisation that had WWI not occurred, there would not have been a revolution, and the lives of so many people, including that of my own family, would have followed a completely different course.
Hojjat Salemi, Chief Business Development Officer, Ranovus
Several years ago, I decided to avoid social media platforms like Instagram and TikTok, as well as the news channels Fox News and CNN. I found them to be major distractions and wasteful of time.
I used the time instead to read and listen to author interviews (podcasts) on YouTube, which often provide deeper insights into why they wrote their books and their key ideas. One of the best decisions I’ve made is controlling what I watch on YouTube—without ads! If you’re looking for good books about technology, here are my recommendations:
The book that won the Financial Times Business Book of the Year for 2024 is Supremacy: AI, ChatGPT, and the Race that Will Change the World by Party Olson.
It offers a fascinating narrative starting in 2012, focusing on how AI systems have developed, with a spotlight on two main figures: Dennis Hassabis, co-founder of DeepMind, and Sam Altman, the co-founder of OpenAI.
The book explores three major themes:
- how AI could reshape society as it grows increasingly intelligent,
- the unintended consequences of the technologies we create,
- and the moral dilemmas and risks of pushing these innovations too far. It’s a fast-paced, thought-provoking look at the future.
Another suggestion is Read Write Own: Building the Next Era of the Internet by Chris Dixon. The book is written clearly and engagingly and explains complex ideas like blockchain, NFTs, and decentralised networks. Dixon describes the evolution of the internet: the early days of reading information, the read-write era of social media where people shared but didn’t own content, and the emerging read-write-own era (Web3), where blockchain allows users to own digital assets.
While I’ve been thinking about decentralised networks a lot, I’m still not convinced they can take off, given our geopolitical challenges. Take Bitcoin, for example; if something goes wrong, who do you call? Moreover, Web3’s dominant players still rely on centralised computing power. It’s a thoughtful read, but only time will tell how Web3 unfolds.
Lastly, I recommend Ethics of Socially Disruptive Technologies: An Introduction. The book, available as a free PDF, is highly educational on how new technologies disrupt societal norms and ethical frameworks.
The book examines four specific technologies: social media, robots, climate engineering, and artificial wombs. For instance, social media was supposed to give everyone a voice and bring people together. Instead, it has often divided us, spread misinformation, and allowed foreign powers to interfere in elections. It challenges the idea of “government of the people, by the people, for the people” today. This book is perfect for anyone wanting to understand new technologies’ unintended consequences.
Professor Laura Lechuga, Head of the Nanobiosensors and Bioanalytical Application Group at the Catalan Institute of Nanoscience and Nanotechnology (ICN2).
I love reading and do it frequently, especially during the many work trips I take throughout the year.
My favourite reading of 2024 was Chip War: The Fight for the World’s Most Critical Technology by Chris Miller. It is an impressive book about the development of microelectronics and the pivotal role of chips in shaping the world powers.
Having a PhD focused on microelectronics, I enjoyed reading a book that will become a masterpiece. What I appreciated most were the personal stories of the brilliant scientists and engineers who conceived, developed, and solved all the technical obstacles to transforming the semiconductor industry that helped found some of the most influential companies in the world. This is a must-read book.
My second favourite book was The Maniac by Benjamin Labatut. The book is a combination of history and novel in which Labatut tells the story of brilliant physicists such as John von Neumann, a genius able to invent new fields. But the same prodigy whose work impacted future advances in computing terrified the people around him, and his personal life was miserable. The book describes the evolution of von Neumann’s work through to the battle between AI and a world champion player of the game Go. It is a book that reflects on the limits of technology, an original, addictive, and beautiful read.
Another book I loved in 2024 was Lessons in Chemistry by Bonnie Garmus. It is a feminist novel about how difficult a professional career was for women scientists in the 1960s. I felt totally reflected in it, as our position has not changed much. It is a book that mixes funny and sad situations, is easy to read, very enjoyable, and has a clear message.
My last recommendation is the old Atlas Shrugged book by Ayn Rand. It isn’t easy to read due to its length but it is a fascinating futuristic story about a dystopian United States, and is now more actual than ever. It is a story of how human stupidity gains a significant advantage over intelligence and the devastating consequences for the U.S. This could also be extended to the rest of the world, perhaps a prophecy to be fulfilled in the coming years.
Roy Rubenstein, Editor of Gazettabyte
I read many books in 2024 and will highlight three. One is Strength in What Remains by Tracy Kidder. I had read his most recent book, Rough Sleepers: Dr. Jim O’Connell’s Urgent Mission to Bring Healing to Homeless People, and this was my follow-up read. Kidder is a master storyteller who finds the most remarkable individuals to write about. I highly recommend both.
Dame Hilary Mantel is best known for her Wolf Hall trilogy. Last year, a book of her writings—articles for literary magazines, essays, film reviews, and her BBC Reith Lectures—was published. A Memoir of My Former Self: A Life in Writing is an excellent read by a fabulous writer.
Lastly, I recommend the 55-hour audible version of Alexandre Dumas’s The Count of Monte Cristo. While listening, I walked past the local cinema and realised there was a 2024 film version being shown. I entered, showed the attendant the audible version and asked if the film was shorter.
OFC 2024 industry reflections: Final part
Chris Cole, Consultant
OFC and optics were back with a vengeance. The high level of excitement and participation in the technical and exhibit programmes was fueled by artifical intelligence/ machine learning (AI/ML). To moderate this exuberance, a few reality checks are offered.
During the Optica Executive Forum, held on the Monday, one of the panels was with optics industry CEOs. They were asked if AI/ML is a bubble. All five said no. They are right that there is a real, dramatic increase in optics demand driven by AI/ML, with solid projections showing exponential growth.
At the same time, it is a bubble because of the outrageous valuations for anything with an AI/ML label, even on the most mundane products. Many booths in the Exhibit Hall had AI/ML on their panels, for the same product types companies have been showing for years. Some of the start-ups and public companies presenting and exhibiting at OFC have frothy valuations by claiming to solve compute bottlenecks. An example is optically interconnecting memory, which sends investors into a frenzy, as if this has not been considered for decades.
The problem with a bubble is that it misallocates resources to promises of near-term pay off, at the expense of investment into long-term fundamental technology which is the only way to enable a paradigm shift to optical AI/ML interconnect.
I presented a version of the below table at the OFC Executive Forum, pointing out that there have only been two paradigm shifts in optical datacom, and these were enabled by fundamentally new optical components and devices which took decades to develop.
My advice to investors was to be skeptical of any optically-enabled breakthrough claims which simply rearrange or integrate existing components and devices. As with previous bubbles, this one will self-correct, and many of the stratospheric valuations will collapse.
Source: Chris Cole
A second dose of reality was provided by Ashkan Seyedi of Nvidia, in several OFC forums, illustrated by the Today’s Interconnect Details table below (shared with permission).
Source: Ashkan Seyedi, Nvidia
He pointed out that the dominant AI/ML interconnect continues to be copper because it beats optics by integer or decade better metrics of bandwidth density, power, and cost. Existing data centre optical networking technology cannot simply be repackaged as optical compute input-output (I/O), including optical memory interconnect, because that does not beat copper.
A third dose of reality came from Xiang Zhou of Google and Qing Wang of Meta in separate detailed analysis presented at the Future of LPO (Linear Pluggable Optics) Workshop. They showed that not only does linear pluggable optics have no future beyond 112 gigabits per lane, but even at that rate it is highly constrained, making it unsuitable for general data centre deployment.
Yet linear pluggable optics was one of the big stories at OFC 2024, with many highly favourable presentations and more than two dozen booths exhibiting it in some form. This was the culmination of a view that has been advanced for years that optics development is too slow, especially if it involves standards. LPO was moved blazingly fast into prototype hardware without being preceded by extensive analysis. The result was predictable as testing in typical large deployment scenarios found significant problems.
At OFC 2025, there will be few if any linear pluggable optics demos. And it will not be generally deployed in large data centres.
Coincidently, the OIF announced that it started a project to standardise optics with one digital signal processor (DSP) in the link, located in the transmitter. This was preceded by analysis, including by Google and Meta, showing good margin against the types of impairments found in large data centres. The expectation is that many IC vendors will have DSP on transmit-only chips soon, including likely at OFC 2025.
A saving grace of linear pluggable optics may be the leveraging of related OIF work on linear receiver specification methodology. Another benefit may be the reaffirmation that real progress in optics is hard and requires fundamental understanding. Shortcutting of well-established engineering practices leads to wasted effort.
Real advances require large investment and take many years, which is what is necessary for optical AI/ML compute interconnect. Let’s hope investors realise this.
Hojjat Salemi, Chief Business Development Officer, Ranovus
Hyperscalers are increasingly recognising that scaling AI/ML compute demands extensive optical connectivity, and the conventional approach of using pluggable optical modules is proving inadequate.
The network infrastructure plays a pivotal role in the compute architecture, with various optimisation strategies depending on the workload. Both compute scale-up and scale-out scenarios necessitate substantial connectivity, high-density beach-front, cost-effectiveness, and energy efficiency. These requirements underscore the advantages of co-packaged optics (CPO) in meeting the evolving demands of AI/ML compute scaling.
It is great to see prominent tier-1 vendors like Nvidia, AMD, Broadcom, Marvell, GlobalFoundries, and TSMC embracing co-packaged optics. Their endorsement shows a significant step forward, indicating that the supply chain is gearing up for high-volume manufacturing by 2026. The substantial investments being poured into this technology underscore the collective effort to address the pressing challenge of scaling compute efficiently. This momentum bodes well for the future of AI/ML compute infrastructure and its ability to meet the escalating demands of various applications.
What surprise me was how fast low-power pluggable optics fizzled. While initially shown as a great technology, linear pluggable optics ultimately fell short in meeting some critical requirements crucial to Hyperscalers. Although retimed pluggable optical modules have been effective in certain applications and are likely to continue serving those needs for the foreseeable future, the evolving demands of new applications such as scaling compute necessitate innovative solutions like co-packaged optics.
The shift towards co-packaged optics highlights the importance of adapting to emerging technologies that can better address the unique challenges and requirements of rapidly evolving industries like hyperscale computing.
Harald Bock, Vice President Network Architecture, Infinera
I am impressed by the range of topics, excellent scientific work and product innovation each time I attend OFC.
Normally, the show's takeaways differ among the participants that I talk to. This year, most of the attendees I chatted agreed on the main topics. The memorable items this year ranged from artificial intelligence (AI) data centres, 800 gigabit-per-second (Gbps) pluggables, to the Full Spectrum Concert at Infinera’s OFC party that was held on the USS Midway.
AI is becoming the key driver for network capacity. While we are a very technology-driven industry, the interest in different technologies is driven by the business opportunities we expect. This puts AI at the top of the list. It is not the AI use cases in network operations, planning, and analytics, which are all progressing, but rather the impact that deploying AI data centres will have on network capacity and particularly on optical interfaces within and between data centres.
The interest was clearly amplified by the fact that recovery of the telecom networks business is only expected in the year’s second half.
Short term, AI infrastructure creates massive demand for short-reach interconnect within data centres, with longer-reach inter-data centre connectivity also being driven by new buildouts. So, we can expect AI to be the key driver of network bandwidth in the coming years.
It is in this context that linear pluggable optics has become an important candidate technology to provide efficient, low-energy interconnect, and as a result, it generated a huge amount of interest this year, stealing some of the attention that co-packaged optics or similar approaches have received in the past. Overall, AI use cases drove huge interest in 800Gbps pluggable optics products and demonstrations at the show.
Reducing interface and network power consumption have become key industry objectives. In all of these use cases and products, power consumption is now the main optimisation goal in order to drive down overall data centre power or to fit all pluggable optics into the same existing form factors (QSFP-DD and OSFP), even at higher rates such as 1.6Tbps.
I do believe that reducing power consumption, be it per capacity, or per reach x capacity depending on use case, has become our industry’s main objective. Looking at projected capacity growth that will continue at 35 to 40 per cent per year across much of cloud networks, that is what we all should be working on.
Another observation is that power consumption and capacity per duct have replaced spectral efficiency as the figure of merit. You could say that this is starting to replace the objective of increasing fibre capacity that our industry has been working under for many years.
We have all discussed the fact that we are no longer going to be able to easily increase spectral efficiency as we are approaching Shannon’s limit. In order to further increase fibre capacity, we have been talking about additional wavelength bands, with products now achieving beyond 10-terabit transmission bandwidth with Super C- and Super L-band and the option to add the S-, O-, and U- bands, as well as about spatial division multiplexing, which today refers to the use of multiple fibre cores to transmit data.
Before OFC, I was puzzled about the steps we, as an industry, would take since all of these require more than a single product from one company. Indeed it is an ecosystem of related components, amplifiers, wavelength handling, even splicing procedures. After OFC, I am now confident that uncoupled multi-core fibre is a good candidate for a next step, with progress on additional wavelength bands not at all out of the picture.
There is one additional point I learned from looking at this topic. In real-world deployments today, multi-core fibre will accelerate a massive increase in parallel fibres that are being deployed in fibre ducts across the world. To me, that means that while we are going to all focus on power consumption as a key measure for innovation, we should really use capacity per duct as an additional figure of merit.
In terms of technological progress, I would like to call out the area of quantum photonics.
We all saw the results from an impressive research push in this area, with complex photonic integration and interesting use cases being explored. The amount of work done in this area makes it difficult for me to keep up to speed. I continue to be fascinated and excited about the work done.
An entirely different category of innovation was shown in the post-deadline session where Microsoft and University of Southampton presented hollow-core fiber with a record 0.11 dB/km fiber loss. While we have been talking about the great promise of anti-resonant hollow-core fiber for a while as it offers significantly reduced latency, it reduces signal distortion by removing nonlinearity and offering low dispersion. All that has been shown before, but achieving a fibre loss that is considerably lower than that of all other fibre types is excellent news.
It confirms that hollow-core fiber could change the systems and the networks we build, and I will continue to keep close tabs on the progress in this area.
Overall, OFC 2024 was a great show, with my company launching new products and having a packed booth full of visitors, a large number of customer engagements, and meetings with most of our suppliers.
I left San Diego already looking forward to next year's OFC.
A coherent roadmap for co-packaged optics
Is coherent optics how co-packaged will continue to scale? Pilot Photonics certainly thinks so.
Part 1: Co-packaged optics
Frank Smyth, CTO and founder of Pilot Photonics, believes the firm is at an important inflection point.
Known for its comb laser technology, Pilot Photonics has just been awarded a €2.5 million European Innovation Council grant to develop its light-source technology for co-packaged optics.
The Irish start-up is also moving to much larger premises and is on a recruitment drive. “Many of our projects and technologies are maturing,” says Smyth.
Company
Founded in 2011, the start-up spent its early years coupled to Dublin City University. It raised its first notable investment in 2017.
The company began by making lab instrumentation based on its optical comb laser technology which emits multiple sources of light that are frequency- and phased-locked. But a limited market caused the company to pivot, adding photonic integration to its laser know-how.
Now, the start-up has a fast-switching, narrow-linewidth tunable laser, early samples of which are being evaluated by several “tier-one” companies.
Pilot Photonics also has a narrowband indium-phosphide comb laser for optical transport applications. This will be the next product it samples.
More recently, the start-up has been developing a silicon nitride-based comb laser for a European Space Agency project. “The silicon nitride micro-resonator in the comb is a non-linear element that enables a very broad comb for highly parallel communication systems and for scientific applications,” says Smyth. It is this laser type that is earmarked for the data centre and for co-packaged optics applications.
Smyth stresses that while still being a small company, the staff has broad expertise. “We cover the full stack,” he says.
Skills range from epitaxial wafer design, photonic integrated circuit (PIC)s and lasers, radio frequency (RF) and thermal expertise, and digital electronics and control design capabilities.
“We learned early on that it’s all well making a PIC, but if no one can interface to it, you are wasting your time,” says Smyth.
Co-packaged optics
Co-packaged optics refers to adding optics next to an ASIC that has significant input-output (I/O) data requirements. Examples of applications for co-packaged optics include high-capacity Ethernet switch chips and artificial intelligence (AI) accelerators. The goal is to give the chip optical rather than electrical interfaces, providing system-scaling benefits; as electrical signals get faster, their reach shrink.
The industry has been discussing co-packaged optics for over a decade. Switch-chip players and systems vendors have shown prototype designs and even products. And more than half a dozen companies are developing the optical engines that surround, and are packaged with, the chip.
However, the solutions remain proprietary, and while the OIF is working to standardise co-packaged optics, end users have yet to embrace the technology. In part, this is because pluggable optical modules continue to advance in data speeds and power consumption, with developments like linear-drive optics.
The ecosystem supporting co-packaged optics is also developing. Hyperscalers will only deploy co-packaged optics in volume when reliability and a broad manufacturing base are proven.
Yet industry consensus remains that optical I/O is a critical technology and that deployments will ramp up in the next two years. Ethernet switch capacity doubles every two years while AI accelerator chips are progressing rapidly. Moreover, the number of accelerator chips used in AI supercomputers is growing fast, from thousands to tens of thousands.
Pilot Photonics believes its multi-wavelength laser technology, coupled with the intellectual property it is developing, will enable co-packaged optics based on coherent optics to address such scaling issues.
Implementations
Co-packaged optics uses optical chiplets or ‘engines’ that surround the ASIC on a shared substrate. The optical engines typically use an external laser source although certain co-packaged optics solutions such as from Intel and Ranovus can integrate the laser as part of the silicon-photonics based optical engine.
Designers can scale the optical engine’s I/O capacity in several ways. They can increase the number of fibres connected to the optical engine, send more wavelengths down each fibre, and increase the wavelength’s data rate measured in gigabits per second (Gbps).
In co-packaged optics designs, 16 engines typically surround the chip. For a 25.6-terabit Ethernet chip, 16 x 1.6-terabit engines are used, each 1.6-terabit engine sending a 100Gbps DR1 signal per fibre. The total fibres per engine equals 32: 16 for the transmit and 16 for the receive (see table).
| Switch capacity/Tbps | Optical engine/Tbps | Optical engines | Data rate/fibre | No. fibres/ engine* |
| 25.6 | 1.6 | 16 | 100G DR, 500m | 32 |
| 25.6 | 3.2 | 8 | 100G DR, 500m | 64 |
| 51.2 | 6.4 | 8 | 400G FR4, 2km | 32 |
| 102.4 (speculative) | 6.4 | 16 | 400G FR4, 2km | 16 |
| 102.4 (speculation) | 12.8 | 8 | 400G FR4, 2km | 32 |
*Not counting the external laser source fibre.
Broadcom’s co-packaged optical approach uses eight optical engines around its 25.6-terabit Tomahawk 4 switch chip, each with 3.2Tbps capacity. For the Tomahawk 5, 51.2-terabit Bailly co-packaged optics design, Broadcom uses eight, 6.4Tbps optical engines, sending 400-gigabit FR4, or 4-wavelength coarse WDM wavelengths, across each fibre. Using FR4 instead of DR1 halves the number of optical engines while doubling overall capacity.
The co-packaging solutions used in the next-generation 102.4-terabit switch chip are still to be determined. Capacity could be doubled using twice as many fibres, or by using 200-gigabit optical wavelengths based on 112G PAM-4 electrical inputs, twice the speed currently used.
But scaling routes for the generation after that – 204.8-terabit switch chips and beyond – and the co-packaged optics design become unclear due to issues of dispersion and power constraints, says Smyth.
Scaling challenges
Assuming eight engines were used alongside the 200-terabit ASIC , each would need to be 25.6Tbps. The fibre count per engine could be doubled again or more wavelengths per fibre would be needed. One player, Nubis Communications, scales its engines and fibres in a 2D array over the top of the package, an approach suited to fibre-count growth.
Doubling the wavelength count is another option but adopting an 8-wavelength CWDM design with 20nm spacing means the wavelengths would cover 160nm of spectrum. Over a 2km reach, this is challenging due to problems with dispersion. Narrower channel spacings such as those used in the CW-WDM MSA (multi-source agreement) require temperature control to ensure the wavelengths stay put.
Keeping the symbol rate fixed but doubling the data rate is another option. But adopting the more complex PAM-8 modulation brings its own link challenges.
Another key issue is power. Current 51.2-terabit switches require 400mW of laser launch power (4 x 100mW lasers) per fibre and there are 128 transmit fibers per switch.
“Assuming a wall plug efficiency of 20 per cent, that is around 250W of power dissipation just for the lasers,” says Smyth. “Getting to 4Tbps per fibre appears possible using 16 wavelengths, but the total fiber launch power is 10 times higher, requiring 2.5kW of electrical power per switch just for the lasers.”
In contrast, single-polarisation coherent detection of 16-QAM signals through a typical path loss of 24dB could match that 4Tbps capacity with the original 250W of laser electrical power, he says.
The optimised total laser power improvement for coherent detection versus direct detection as a function of the additional losses in the signal path (the losses not also experienced by the local oscillator). Source: Pilot Photonics
Coherent detection is associated with a high-power digital signal processor (DSP). Are such chips feasible for such a power-sensitive application as co-packaged optics?
Coherent detection adds some DSP complexity, says Smyth, but it has been shown that for pluggable-based intra data centre links using 5nm CMOS silicon, 400-gigabit coherent and direct-detection are comparable in terms of ASIC power but coherent requires less laser power.
“Over time, a similar battle will play out for co-packaged optics. Laser power will become a bigger issue than DSP power,” he says.
The additional signal margin could be used for 10km links, with tens of terabits per fibre and even 80km links at similar per-fibre rates to current direct detection.
“We believe coherent detection in the data centre is inevitable,” says Smyth. “It’s just a question of when.”
Comb-based coherent co-packaged optics
Coherent co-packaged optics brings its own challenges. Coherent detection requires alignment between the signal wavelength and the local oscillator laser in the receiver. Manufacturing tolerances and the effects of ageing in simple laser arrays make this challenging to achieve.
“The wavelengths of a comb laser are precisely spaced, which greatly simplifies the problem,” says Smyth. “And combs bring other benefits related to carrier recovery and lack of inter-channel interference too”.
Pilot Photonics’ comb laser delivers 16 or 32 wavelengths per fibre, up to 8x more than existing solutions. Smyth says the company intends to fit its comb laser inside the OIF’s standardised External Laser Source pluggable form-factor,
The start-up is also developing a coherent ring resonator modulator for its design. The ring modulator is tiny compared with Mach-Zehnder interferometer modulators used for coherent optics.
Pilot Photonics is also developing IP for coherent signal processing. Because its comb laser locks the frequency and phase of the wavelengths generated, the overall control and signal processing can be simplified.
While it will offer the comb laser, the start-up does not intend to develop the DSP IC nor make optical engines itself.
“A strategic partnership with a company with its own manufacturing facilities would be the most effective way of getting this technology to market,” says Smyth.
First co-packaged optics switches set for next year
Ranovus says two of its lead customers will deploy co-packaged optics next year.
They will deploy 25.6-terabit Ethernet switch chips but these will be proof-of-concept designs rather than volume deployments.
The deployments will be used to assess the software and gain experience with their maintenance including replacing optics if needed.
“I do think 2024 is going to be the volume year,” says Hamid Arabzadeh, CEO of Ranovus, who expects to announce the customers before the year-end.
Disaggregated server untangles compute, memory and storage elements
Applications
Ranovus is focussed on the emerging integrated optical input-output (I/O) market for Ethernet switches and disaggregated server designs.
A disaggregated server untangles the compute, memory and storage elements found on a server card and pools them separately. This enables a CPU or compute node to access far more memory. It also means each of the server elements can be upgraded independently.
Pooling the memory suits artificial intelligence (AI)/ machine learning applications that process huge data sets. Such applications also require considerable computing.
For machine learning applications, graphic processing unit (GPU) chips are tightly coupled in clusters. But it is a challenge to continually grow the number of GPUs in a cluster and support inter-cluster communications using eletrical interfaces.
Data centre operators want processing performance that scales linearly as more GPUs are adding to a cluster and more clusters are used. This requires longer-reach, high-bandwidth, low-latency links. Limiting the power consumption of such links is also key.
Such system design challenges explain the industry’s interest in adding optical I/O to high-end processors like GPUs. The same applies to Ethernet switch-chips that are doubling in capacity every two years. Moving from electrical to optical interfaces promises longer, energy efficient (measured in pJ/bit), low-latency links.
For Ethernet switch designs, the optical I/O end-point bandwidth needed is at least 3.2 terabits per second (Tbps), says Arabzadeh, whereas for AI it is 0.5-1Tbps.
Odin optical engine
Ranovus recently expanded its optical interconnect portfolio by developing an Odin design that doesn’t need an accompanying retimer chip.
The optical engine combines CMOS and silicon photonics circuits in a monolithic chip, resulting in a smaller, cheaper and power-efficient design.
This second-generation Odin means Ranovus can now offer digital and analogue drive options for co-packaged optics and address more cost-conscious applications such as chip interconnect in servers.
Arabzadeh says its first Odin design that uses a retimer chip helped secure its lead customers.
“We have two lead customers where we are doing the co-packaging of their [switch] chips operating at 100-gigabit PAM-4,” he says. “And we also have an AI customer, where their chip talks PCI Express 5.0 (PCIe 5.0) to our Odin.”
Ranovus first unveiled its Odin-8 800-gigabit design at OFC 2020 and demonstrated it sending eight 100 gigabit PAM-4 (4-level pulse-amplitude modulation) signals, each on a separate fibre.
The design includes a digital retimer IC which takes the OIF-standard extra short reach (XSR) signal – for example, from a switch chip – and recreates (retimes) the PAM-4 signal before forwarding it to Ranovus’ chip. Such a configuration is referred to as a digital-drive design.
“This retimer is not a chip we do and it is expensive,” says Arabzadeh. “It also consumes half the power of the [Odin] chiplet design.”
Ranovus also detailed over a year ago its Odin-32 design that supports four wavelengths per fibre for a total bandwidth of 3.2Tbps.
Since then, Ranovus has developed its Odin-8 for use in an 800-gigabit DR8 optical module. The module will sample and be in the hands of customers for testing in the coming quarter.
The Odin-based 800G-DR8 optical module has a power consumption of 13W; 4W less than rival designs, says Arabzadeh, adding that the optical engine is cost-effective at 400 gigabits, even when using half its capacity.
ODIN version 2.0
The latest monolithic chip is an analogue-drive design. It features radio frequency (RF) drivers, trans-impedance amplifiers (TIAs), silicon photonics transmitters and receivers, and control logic to oversee the components.
The chip does away with clock data recovery (CDR) while integrating the TIAs on-chip. This reduces system costs. “We have the first TIA at 100 gigabits in CMOS,” says Arabzadeh.
To work without the retimer, the monolithic chip is placed much closer to the driving ASIC, with both sharing a common substrate. “It works because it is parked right next to the other chip,” says Arabzadeh.
Ranovus uses a software model of a vendor’s ASIC’s serialiser/ deserialiser (serdes) to ensure the serdes will drive its analogue input.
Being an analogue drive, it is bit-rate and protocol agnostic. “This allows us to get customers beyond the Ethernet market,” says Arabzadeh. These include 100-gigabit PAM-4 signals and the PCIe 5.0 protocol, as mentioned.
For machine learning applications, a proprietary protocol can be used between the end points. NVLink, a serial multi-lane communications link developed by Nvidia, is one such protocol.
Arabzadeh says Ranovus has achieved 1 terabit-per-mm in pitch interface densities: “The stuff we have got involved in with folks in machine learning and AI dwarfs the Ethernet market.”
Laser source
Ranovus’ co-packaged designs use an external laser source. But the company has patented technlogy that allows lasers to be attached directly to the monolithic chip.
This is done at the wafer level, before slicing a wafer to its constituent die. As a result, Ranovus now has two Odin-8 optical engines, one that uses an external laser source (Odin-8ELS) and one with integrated lasers (Odin-8IL)
The laser-attach technology suits optical module designs and expands the company’s optical interconnect toolkit.
The industry has yet to decide whether to adopt a digital or analogue drive approach for co-packaged optics, but the latest Odin design means Ranovus can do both.
Packaging
The company has also been addressing the tricky issue of packaging the chip. “The packaging is a very difficult challenge,” says Arabzadeh.
Ranovus has used the Odin-8 to verify its packaging approach. Two sets of eight fibres are required for the optical I/O (a set to send and a set to receive) and four more fibres are used for the external laser source.
The Odin-32 will use the same packaging and fibre count. What will change is the chip that will support four wavelengths per fibre; instead of the single ring resonator modulator per output, four will be used.
Arabzadeh says each ring modulator is 25 micron so using one or four per path has little impact on the chip’s area.
Market development
Ranovus is addressing both the co-packaged optics and module designs with its Odin designs.
At the OFC conference and exhibition this summer, Arista Networks outlined how pluggable optics will be able to address 102.4 terabit Ethernet switches while Microsoft said it expects to deploy co-packaged optics by the second half of 2024.
Because of the uncertainty as to when co-packaged optics will take off, Ranovus will also supply its optics for the 400-gigabit and 800-gigabit pluggable module market.
“That is why we have yet to tape out the Odin-32,” he says. “We didn’t want to have the technology and there is nobody on the other side of it.”
But the key is to have an optical interface portfolio that secures designs early.
“If you can get the wins and through that, modify your chip, then you are designed in,” says Arabzadeh.
Coherent optics players target the network edge for growth
Part 1: Coherent developments
The market for optical links for reaches between 10km and 120km is emerging as a fierce battleground between proponents of coherent and direct-detection technologies.
Interest in higher data rates such as 400 gigabits is pushing coherent-based optical transmission from its traditional long-distance berth to shorter-reach applications. “That tends to be where the growth for coherent has come from as it has migrated from long-haul to metro,” says Tom Williams, senior director of marketing at Acacia Communications, a coherent technology supplier.
Source: Acacia Communications, Gazettabyte
Williams points to the Optical Internetworking Forum’s (OIF) ongoing work to develop a 400-gigabit link for data centre interconnect. Dubbed 400ZR, the project is specifying an interoperable coherent interface that will support dense wavelength-division multiplexing (DWDM) links for distances of at least 80km.
Meanwhile, the IEEE standards group defining 400 Gigabit Ethernet has issued a Call-For-Interest to determine whether to form a Study Group to look at 400-Gigabit applications beyond the currently defined 10km 400GBASE-LR8 interface.
“Coherent moving to higher-volume, shorter-reach solutions shows it is not just a Cadillac product,” says Williams. Higher-volume markets will also be needed to fund coherent chip designs using advanced CMOS process nodes. “Seven nanometer [CMOS] becomes a very expensive prospect,” says Williams. “The traditional business case is not going to be there without finding higher volumes.”
Coherent moving to higher-volume, shorter-reach solutions shows it is not just a Cadillac product
Pico DSP
Acacia detailed its next-generation high-end coherent digital signal processor (DSP) at the OFC show held in Los Angeles in March.
Tom WilliamsDubbed Pico, the DSP will support transmission speeds of up to 1.2 terabits-per-second using two carriers, each carrying 600 gigabits of data implemented using 64-ary quadrature amplitude modulation (64QAM) and a 64 gigabaud symbol rate. The 16nm CMOS dual-core DSP also features an internal crossbar switch to support a range of 100-gigabit and 400-gigabit client interfaces.
ADVA Optical Networking is using the Pico for its Teraflex data centre interconnect product. The Teraflex design supports 3.6 terabits of line-side capacity in a single rack unit (1RU). Each 1RU houses three “sleds”, each supporting two wavelengths operating at up to 600 gigabits-per-second (Gbps).
But ADVA Optical Networking also detailed at OFC its work with leading direct-detection technology proponents, Inphi and Ranovus. For the data centre interconnect market, there is interest in coherent and direct-detection technologies, says ADVA.
Detailing the Pico coherent DSP before it is launched as a product is a new development for Acacia. “We knew there would be speculation about ADVA’s Teraflex technology and we preferred to be up front about it,” says Williams.
The 16nm Pico chip was also linked to an Acacia post-deadline paper at OFC detailing the company’s progress in packaging its silicon photonics chips using ball grid array (BGA) technology. Williams stresses that process issues remain before its photonic integrated circuit (PIC) products will use BGA packaging, an approach that will simplify and reduce manufacturing costs.
“You are no longer running the board with all the electronics through a surface mount line and then have technicians manually solder on the optics,” says Williams. Moreover, BGA packaging will lead to greater signal integrity, an important consideration as the data rates between the coherent DSP and the PIC increase.
It is an endorsement of our model but I do not think it is the same as ours. You still have to have someone providing the DSP and someone else doing the optics
Coherent competition
Ciena's recent announcement that it is sharing its WaveLogic Ai coherent DSP technology with optical module vendors Lumentum, Oclaro and NeoPhotonics is seen as a response to Acacia’s success as a merchant supplier of coherent modules and coherent DSP technologies.
Williams says Acacia’s strategy remains the same when asked about the impact of the partnership between Ciena and the optical module makers: to continue being first to market with differentiated products.
One factor that has helped Acacia compete with merchant suppliers of coherent DSPs - NEL and ClariPhy, now acquired by Inphi - is that it also designs the silicon photonics-based optics used in its modules. This allows a trade-off between the DSP and the optics to benefit the overall system design.
A challenge facing the three optical module makers working with Ciena is that each one will have to go off and optimise their design, says Williams. “It is an endorsement of our model but I do not think it is the same as ours,” he says. “You still have to have someone providing the DSP and someone else doing the optics.”
Coherent roadmap
Acacia has managed to launch a new coherent DSP product every year since 2011 (see diagram, above). In 2015 it launched its Denali DSP, the first to operate at line rates greater than 100Gbps.
Last year it announced the Meru, a low-power DSP for its CFP2-DCO module. The CFP2-DCO operates at 100Gbps using polarisation multiplexing, quadrature phase-shift keying, (PM-QPSK) and two 200Gbps modes: one using 16-ary quadrature amplitude modulation (PM-16QAM) and a longer reach variant, implemented using a higher baud rate and 8-ary quadrature amplitude modulation (PM-8QAM). The CFP2-DCO is already starting to be designed into platforms.
Since 2014, Acacia has launched a low-power DSP design every even year and a high-end DSP every odd year, with the Pico being the latest example.
Acacia has not said when the Pico coherent DSP will be generally available but ADVA Optical Networking has said it expects to launch the Teraflex in early 2018.
Reflections on OFC 2017
Mood, technologies, notable announcements - just what are the metrics to judge the OFC 2017 show held in Los Angeles last week?
It was the first show I had attended in several years and the most obvious changes were how natural the presence of the internet content providers now is alongside the telecom operators, as well as systems vendors exhibiting at the show. Chip companies, while also present, were fewer than before.
Source: OSA
Another impression were the latest buzz terms: 5G, the Internet of Things and virtual reality-augmented reality. Certain of these technologies are more concrete than others, but their repeated mention suggests a consensus that the topics are real enough to impact optical components and networking.
It could be argued that OFC 2017 was the year when 400 Gigabit Ethernet became a reality
The importance of 5G needs no explanation while the more diffuse IoT is expected to drive networking with the huge amounts of data it will generate. But what are people seeing about virtual reality-augmented reality that merits inclusion alongside 5G and IoT?
Another change is the spread of data rates. No longer does one rate represent the theme of an OFC such as 40 Gigabits or 100 Gigabits. It could be argued that OFC 2017 was the year when 400 Gigabit Ethernet became a reality but there is now a mix of relevant rates such as 25, 50, 200 and 600 gigabits.
Highlights
There were several highlights at the show. One was listening to Jiajin Gao, deputy general manager at China Mobile Technology, open the OIDA Executive Forum event by discussing the changes taking place in the operator's network. Gao started by outlining the history of China Mobile's network before detailing the huge growth in ports at different points in the network over the last two years. He then outlined China Mobile's ambitious rollout of new technologies this year and next.
China's main three operators have 4G and FTTx subscriber numbers that dwarf the rest of the world. Will 2017 eventually be seen as the year when the Chinese operators first became leaders in telecom networking and technologies?
The Executive Forum concluded with an interesting fireside discussion about whether the current optical market growth is sustainable. The consensus among representatives from Huawei, Hisense, Oclaro and Macom was that it is; that the market is more varied and stable this time compared to the boom and bust of 1999-2001. As Macom’s Preetinder Virk put it: "The future has nothing to do with the past". Meanwhile, Huawei’s Jeffrey Gao still expects strong demand in China for 100 gigabits in 2017 even if growth is less strong than in 2016. He also expects the second quarter this year to pick up compared to a relatively weak first quarter.
OFC 2017 also made the news with an announcement that signals industry change: Ciena's decision to share its WaveLogic Ai coherent DSP technology with optical module vendors Lumentum, Oclaro and NeoPhotonics.
The announcement can be viewed several ways. One is that the initiative is a response to the success of Acacia as a supplier of coherent modules and coherent DSP technology. System vendors designed their own coherent DSP-ASICs to differentiate their optical networking gear. This still holds true but the deal reflects how the progress of merchant line-side optics from the likes of Acacia is progressing and squeezing the scope for differentiation.
The deal is also a smart strategic move by Ciena which, through its optical module partners, will address new markets and generate revenues as its partners start to sell modules using the WaveLogic Ai. The deal also has a first-mover advantage. Other systems vendors may now decide to offer their coherent DSPs to the marketplace but Ciena has partnerships with three leading optical module makers and is working with them on future DSP developments for pluggable modules.
The deal also raises wider questions as to the role of differentiated hardware and whether it is subtly changing in the era of network function virtualisation, or whether it is a reflection of the way companies are now collaborating with each other in open hardware developments like the Telecom Infra Project and the Open ROADM MSA.
Another prominent issue at the show is the debate as to whether there is room for 200 Gigabit Ethernet modules or whether the industry is best served by going straight from 100 to 400 Gigabit Ethernet.
Facebook and Microsoft say they will go straight to 400 gigabits. Cisco agrees, arguing that developing an interim 200 Gigabit Ethernet interface does not justify the investment. In contrast, Finisar argues that 200 Gigabit Ethernet has a compelling cost-per-bit performance and that it will supply customers that want it. Google supported 200 gigabits at last year’s OFC.
Silicon photonics
Silicon photonics was one topic of interest at the show and in particular how the technology continues to evolve. Based on the evidence at OFC, silicon photonics continues to progress but there were no significant developments since our book (co-written with Daryl Inniss) on silicon photonics was published late last year.
One of the pleasures of OFC is being briefed by key companies in rapid succession. Intel demonstrated at its booth its silicon photonics products including its CWDM4 module which will be generally available by mid-year. Intel also demonstrated a 10km 4WDM module. The 4WDM MSA, created last year, is developing a 10km reach variant based on the CWDM4, as well as 20km and 40km based designs.
Meanwhile, Ranovus announced its 200-gigabit CFP2 module based on its quantum dot laser and silicon photonics ring resonator technologies with a reach approaching 100km. The 200 gigabit is achieved using 28Gbaud optics and PAM-4.
Elenion Technologies made several announcements including the availability of its monolithically integrated coherent modulator receiver after detailing it was already supplying a 200 gigabit CFP2-ACO to Coriant. The company was also demonstrating on-board optics and, working with Cavium, announced a reference architecture to link network interface cards and switching ICs in the data centre.
I visited Elenion Technologies in a hotel suite adjacent to the conference centre. One of the rooms had enough test equipment and boards to resemble a lab; a lab with a breathtaking view of the hills around Los Angeles. As I arrived, one company was leaving and as I left another well-known company was arriving. Elenion was using the suite to demonstrate its technologies with meetings continuing long after the exhibition hall had closed.
Two other silicon photonics start-ups at the show were Ayar Labs and Rockley Photonics.
Ayar Labs in developing a silicon photonics chip based on a "zero touch" CMOS process that will sit right next to complex ASICs and interface to network interface cards. The first chip will support 3.2 terabits of capacity. The advantage of the CMOS-based silicon photonics design is the ability to operate at high temperatures.
Ayar Labs is using the technology to address the high-bandwidth, low-latency needs of the high-performance computing market, with the company expecting the technology to eventually be adopted in large-scale data centres.
Rockley Photonics shared more details as to what it is doing as well as its business model but it is still to unveil its first products.
The company has developed silicon photonics technology that will co-package optics alongside ASIC chips. The result will be packaged devices with fibre-based input-output offering terabit data rates.
Rockley also talked about licensing the technology for a range of applications involving complex ICs including coherent designs, not just for switching architectures in the data centre that it has discussed up till now. Rockley says its first product will be sampling in the coming months.
Looking ahead
On the plane back from OFC I was reading The Undoing Project by Michael Lewis about the psychologists Danny Kahneman and Amos Tversky and their insights into human thinking.
The book describes the tendency of people to take observed facts, neglecting the many facts that are missed or could not be seen, and make them fit a confident-sounding story. Or, as the late Amos Tversky put it: "All too often, we find ourselves unable to predict what will happen; yet after the fact, we explain what did happen with a great deal of confidence. This 'ability' to explain that which we cannot predict, even in the absence of any additional information, represents an important, though subtle, flaw in our reasoning."
So, what to expect at OFC 2018? More of the same and perhaps a bombshell or two. Or to put it another way, greater unpredictability based on the impression at OFC 2017 of an industry experiencing an increasing pace of change.
Ranovus shows 200 gigabit direct detection at ECOC
Ranovus has announced it first direct-detection optical products for applications including data centre interconnect.
Saeid AramidehThe start-up has announced two products to coincide with this week’s ECOC show being held in Dusseldorf, Germany.
One product is a 200 gigabit-per-second (Gbps) dense wavelength-division multiplexing (WDM) CFP2 pluggable optical module that spans distances up to 130km. Ranovus will also sell the 200Gbps transmitter and receiver optical engines that can be integrated by vendors onto a host line card.
The dense WDM direct-detection solution from Ranovus is being positioned as a cheaper, lower-power alternative to coherent optics used for high-capacity metro and long-haul optical transport. Using such technology, service providers can link their data centre buildings distributed across a metro area.
The cost [of the CFP2 direct detection] proves in much better than coherent
“The power consumption [of the direct-detection design] is well within the envelope of what the CFP2 power budget is,” says Saeid Aramideh, a Ranovus co-founder and chief marketing. The CFP2 module's power envelop is rated at 12W and while there are pluggable CFP2-ACO modules now available, a coherent DSP-ASIC is required to work alongside the module.
“The cost [of the CFP2 direct detection] proves in much better than coherent does,” says Aramideh, although he points out that for distances greater than 120km, the economics change.
The 200Gbps CFP2 module uses four wavelengths, each at 50Gbps. Ranovus is using 25Gbps optics with 4-level pulse-amplitude modulation (PAM-4) technology provided by fabless chip company Broadcom to achieve the 50Gbps channels. Up to 96, 50 Gbps channels can be fitted in the C-band to achieve a total transmission bandwidth of 4.8 terabits.
Ranovus is demonstrating at ECOC eight wavelengths being sent over 100km of fibre. The link uses a standard erbium-doped fibre amplifier and the forward-error correction scheme built into PAM-4.
Technologies
Ranovus has developed several key technologies for its proprietary optical interconnect products. These include a multi-wavelength quantum dot laser, a silicon photonics based ring-resonator modulator, an optical receiver, and the associated driver and receiver electronics.
The quantum dot technology implements what is known as a comb laser, producing multiple laser outputs at wavelengths and grid spacings that are defined during fabrication. For the CFP2, the laser produces four wavelengths spaced 50GHz apart.
For the 200Gbps optical engine transmitter, the laser outputs are fed to four silicon photonics ring-resonator modulators to produce the four output wavelengths, while at the receiver there is an equivalent bank of tuned ring resonators that delivers the wavelengths to the photo-detectors. Ranovus has developed several receiver designs, with the lower channel count version being silicon photonics based.
The quantum dot technology implements what is known as a comb laser, producing multiple laser outputs at wavelengths and grid spacings that are defined during fabrication.
The use of ring resonators - effectively filters - at the receiver means that no multiplexer or demultiplexer is needed within the optical module.
“At some point before you go to the fibre, there is a multiplexer because you are multiplexing up to 96 channels in the C-band,” says Aramideh. “But that multiplexer is not needed inside the module.”
Company plans
The startup has raised $35 million in investment funding to date. Aramideh says the start-up is not seeking a further funding round but he does not rule it out.
The most recent funding round, for $24 million, was in 2014. At the time the company was planning to release its first product - a QSFP28 100-Gigabit OpenOptics module - in 2015. Ranovus along with Mellanox Technologies are co-founders of the dense WDM OpenOptics multi-source agreement that supports client side interface speeds at 100Gbps, 400Gbps and terabit speeds.
However, the company realised that 100-gigabit links within the data centre were being served by the coarse WDM CWDM4 and CLR4 module standards, and it chose instead to focus on the data centre interconnect market using its direct detection technology.
Ranovus has also been working with ADVA Optical Networking with it data centre interconnect technology. Last year, ADVA Optical Networking announced its FSP 3000 CloudConnect data centre interconnect platform that can span both the C- and L-bands.
Also planned by Ranovus is a 400-gigabit CFP8 module - which could be a four or eight channel design - for the data centre interconnect market.
Meanwhile, the CFP2 direct-detection module and the optical engine will be generally available from December.
COBO acts to bring optics closer to the chip
The goal of COBO, announced at the OFC 2015 show and backed by such companies as Microsoft, Cisco Systems, Finisar and Intel, is to develop a technology roadmap and common specifications for on-board optics to ensure interoperability.
“The Microsoft initiative is looking at the next wave of innovation as it relates to bringing optics closer to the CPU,” says Saeid Aramideh, co-founder and chief marketing and sales officer for start-up Ranovus, one of the founding members of COBO. “There are tremendous benefits for such an architecture in terms of reducing power dissipation and increasing the front panel density.”
On-board optics refers to optical engines or modules placed on the printed circuit board, close to a chip. The technology is not new; Avago Technologies and Finisar have been selling such products for years. But these products are custom and not interoperable.
Placing the on-board optics nearer the chip - an Ethernet switch, network processor or a microprocessor for example - shortens the length of the board’s copper traces linking the two. The fibre from the on-board optics bridges the remaining distance to the equipment’s face plate connector. Moving the optics onto the board reduces the overall power consumption, especially as 25 Gigabit-per-second electrical lanes start to be used. The fibre connector also uses far less face plate area compared to pluggable modules, whether the CFP2, CFP4, QSFP28 or even an SFP+.
“The [COBO] initiative is going to be around defining the electrical interface, the mechanical interface, the power budget, the heat-sinking constraints and the like,” says Aramideh.
To understand why such on-board optics will be needed, Aramideh cites Broadcom’s StrataXGS Tomahawk switch chips used for top-of-rack and aggregation switches. The Tomahawk is Broadcom’s first switch family that use 25 Gbps serialiser/ deserialiser (serdes) and has an aggregate switch bandwidth of up to 3.2 terabit. And Broadcom is not alone. Cavium through its Xplaint acquisition has the CNX880xx line of Ethernet switch chips that also uses 25 Gbps lanes and has a switch capacity up to 3.2 terabit.
“You have 1.6 terabit going to the front panel and 1.6 terabit going to the back panel; that is a lot of traces,” says Aramideh. “If you make this into opex [operation expense], and put the optics close to the switch ASIC, the overall power consumption is reduced and you have connectivity to the front and the back.”
This is the focus of Ranovus, with the OpenOptics MSA initiative. “Scaling into terabit connectivity over short distances and long distances,” he says.
OpenOptics MSA
At OFC, members of the OpenOptics MSA, of which Ranovus and Mellanox are founders, published its WDM specification for an interoperable 100 Gbps WDM standard that will have a two kilometer reach.
The 100 Gigabit standard uses 4x25 Gbps wavelengths but Aramideh says the standard scales to 8, 16 and 32 lanes. In turn, there will also be a 50 Gbps lane version that will provide a total connectivity of 1.6 terabit (32x50 Gbps).
Ranovus has not detailed what modulation scheme it will use to achieve 50 Gbps lanes, but Aramideh says that PAM-4 is one of the options and an attractive one at that. “There are also a lot of chipsets [supporting PAM-4] becoming available,” he says.
Ranovus’s first products will be an OpenOptics MSA optical engine and an QSFP28 optical module. “We are not making any product announcements yet but there will be products available this year,” says Aramideh.
Meanwhile, Ciena has become the sixth member to join the OpenOptics MSA.
Ranovus readies its interfaces for deployment
- Products will be deployed in the first half of 2015
- Ranovus has raised US $24 million in a second funding round
- The start-up is a co-founder of the OpenOptics MSA; Oracle is now also an MSA member.
Ranovus says its interconnect products will be deployed in the first half of 2015. The start-up, which is developing WDM-based interfaces for use in and between data centres, has raised US $24 million in a second stage funding round. The company first raised $11 million in September 2013.
Saeid Aramideh"There is a lot of excitement around technologies being developed for the data centre," says Saeid Aramideh, a Ranovus co-founder and chief marketing and sales officer. He highlights such technologies as switch ICs, software-defined networking (SDN), and components that deliver cost savings and power-consumption reductions. "Definitely, there is a lot of money available if you have the right team and value proposition," says Aramideh. "Not just in Silicon Valley is there interest, but in Canada and the EU."
The optical start-up's core technology is a quantum dot multi-wavelength laser which it is combining with silicon photonics and electronics to create WDM-based optical engines. With the laser, a single gain block provides several channels while Ranovus is using a ring resonator implemented in silicon photonics for modulation. The company is also designing the electronics that accompanies the optics.
Aramideh says the use of silicon photonics is a key part of the design. "How do you enable cost-effective WDM?" he says."It is not possible without silicon photonics." The right cost points for key components such as the modulator can be achieved using the technology. "It would be ten times the cost if you didn't do it with silicon photonics," he says.
The firm has been working with several large internet content providers to turn its core technology into products. "We have partnered with leading data centre operators to make sure we develop the right products for what these folks are looking for," says Aramideh.
In the last year, the start-up has been developing variants of its laser technology - in terms of line width and output power - for the products it is planning. "A lot goes into getting a laser qualified," says Aramideh. The company has also opened a site in Nuremberg alongside its headquarters in Ottawa and its Silicon Valley office. The latest capital will be used to ready the company's technology for manufacturing and recruit more R&D staff, particularly at its Nuremberg site.
Ranovus is a founding member, along with Mellanox, of the 100 Gigabit OpenOptics multi-source agreement. Oracle, Vertilas and Ghiasi Quantum have since joined the MSA. The 4x25 Gig OpenOptics MSA has a reach of 2km-plus and will be implemented using a QSFP28 optical module. OpenOptics differs from the other mid-reach interfaces - the CWDM4, PSM4 and the CLR4 - in that it uses lasers at 1550nm and is dense wavelength-division multiplexed (DWDM) based.
It is never good that an industry is fragmented
That there are as many as four competing mid-reach optical module developments, is that not a concern? "It is never good that an industry is fragmented," says Aramideh. He also dismisses a concern that the other MSAs have established large optical module manufacturers as members whereas OpenOptics does not.
"We ran a module company [in the past - CoreOptics]; we have delivered module solutions to various OEMs that are running is some of the largest networks deployed today," says Aramideh. "Mellanox [the other MSA co-founder] is also a very capable solution provider."
Ranovus plans to use contract manufacturers in Asia Pacific to make its products, the same contract manufacturers the leading optical module makers use.
Table 1: The OpenOptics MSA
End markets
"I don't think as a business, anyone can ignore the big players upgrading data centres," says Aramideh. "The likes of Google, Facebook, Amazon, Apple and others that are switching from a three-tier architecture to a leaf and spine need longer-reach connectivity and much higher capacity." The capacity requirements are much beyond 10 Gig and 40 Gig, and even 100 Gig, he says.
Ranovus segments the adopters of interconnect into two: the mass market and the technology adopters. "Mass adoption today is all MSA-based," says Aramideh. "The -LR4 and -SR10, and the same thing is happening at 100 Gig with the QSFP28." The challenge for the optical module companies is who has the lowest cost.
Then there are the industry leaders such as the large internet content providers that want innovative products that address their needs now. "They are less concerned about multi-source standard-based solutions if you can show them you can deliver a product they need at the right cost," says Aramideh.
Ranovus will offer an optical engine as well as the QSFP28 optical module. "The notion of the integration of an optical engine with switch ICs and other piece parts in the data centre are more of an urgent need," he says.
Using WDM technology, the company has a scalable roadmap that includes 8x25 Gig and 16x25 Gig (400 Gig) designs. Also, by adding higher-order modulation, the technology will scale to 1.6 Terabit (16x100 Gig), says Aramideh.
I don't see a roadmap for coherent to become cost-effective to address the smaller distances
Ranovus is also working on interfaces to link data centres.
"These are distances much shorter than metro/ regional networks," says Aramideh, with the bulk of the requirements being for links of 15 to 40km. For such relatively short distances, coherent detection technology has a high-power consumption and is expensive. "I don't see a roadmap for coherent to become cost-effective to address the smaller distances," says Aramideh.
Instead, the company believes that a direct-detection interconnect that supports 15 to 40km and which has a spectral efficiency that can scale to 9.6 Terabit is the right way to go. If that can be achieved, then switching from coherent to direct detection becomes a no-brainer, he says. "For inter-data-centres, we are really offering an alternative to coherent."
The start-up says its technology will be in product deployment with lead customers in the first half of 2015.
Ranovus developing DWDM links for the data centre
Ranovus has raised US $11 million in funding to develop Terabit capacity links for the data centre. The Ottawa-based start-up plans to use dense wavelength-division multiplexing (DWDM) technology to create huge data pipes that reduce significantly the power consumption, and cost, per bit.
The company says that it is not a silicon photonics start-up but rather a user of the technology to make its interface. Ranovus will use a foundry to make its optical chips.
Ranovus includes former staff of the coherent transmission and DSP specialist, CoreOptics, acquired by Cisco Systems in 2010. "Electronics, as we learnt from our previous endeavour, can impact in a big way the cost-performance of links," says Aramideh. "It doesn't have to be expensive equaliser technology we developed in the past, but there are ways of using similar technology in CMOS ICs to solve some of the network problems."
This suggests that DSP will be used to help cram the multiple channels in the fibre as well as achieve several hundred kilometers of reach. But the DSP will use simpler algorithms than those for long-distance coherent transmission.
Aramideh says its Terabit interface is inevitably a proprietary design. "[Industry] standards are important and you need to have dual sourcing, but people value having disruptive technologies," he says. "The challenge the industry has is that there hasn't been a lot of innovation going into technologies specifically for the data centre."
The start-up's technology is being validated with several lead customers. "It is early proof of technology and the platform in terms of configurations that the customers will be using," he says.
The $11m funding raised will be used to commercialise the technology and make the first products for lead customers. "We are very advanced in our plans with respect to delivery of our product," says Aramideh. Ranovus expects to provide first details of its product at OFC 2014.