OFC/NFOEC 2013 industry reflections - Part 2
Bill Gartner, vice president and general manager of high-end routing and optical business unit at Cisco Systems.
There were several key themes during this year’s OFC conference, but what I found most compelling were the disruptive trends and technologies that stand to significantly impact the optical communications market in the coming years.
"SDN could be the single biggest disruptor in the transport industry and has the potential to transform network programmability and orchestration"
One of the hottest themes at this year’s OFC conference is the role of silicon photonics and the benefits it presents to service providers and carriers. Silicon photonics is truly one of the most interesting advancements taking place in the industry as it has the potential to drastically lower the density, power and overall cost of ASICs.
Several carriers at the show, including CenturyLink and AT&T, presented their view that optics is becoming a larger portion of their spend and now exceeds the cost of packet switching technologies.
A second key trend coming out of the show is software-defined networking (SDN) and its impact on networking. There is tremendous industry interest around this topic and it extended to the Anaheim Convention Center.
With SDN, our customers can increase flexibility in terms of selecting the features and protocols that make sense for their network application – whether it is a data centre application, a service provider application or a large-scale enterprise application.
The last theme that resonated during OFC was around the convergence of packet and optical solutions. As service providers look for ways to decrease both CapEx and OpEx related to the network, incremental technology improvements will decrease costs. However, for many customers, their network capacity is growing far faster than their revenues, so incremental improvements will not yield required reductions.
"As an industry we have to evolve organisationally and technically. Those who fail to recognise that face extinction."
This shows us that we need to explore more fundamental shifts in architectures that have the potential to yield significant savings in OpEx and CapEx. Enter the convergence of IP and optical – this may take the form of converged platforms, but will also involve multi-layer control planes that allow the exchange of information between the packet and optical layers. This convergence helps answer questions like: How well is the network utilised? Can it be optimised? Are there multi-layer protection/ restoration schemes that make better use of the available resources?
During the conference, I had the opportunity to present at the OSA Executive Forum, which brought together more than 150 senior-level executives to discuss key themes, opportunities and challenges facing the next generation in optical communications.
What struck me is that this industry is constantly evolving, which presents challenges and opportunities. We are looking at an industry that is highly fragmented at the moment and requires further streamlining.
You have new players at every level of the value chain that bring exciting, unique perspectives and advanced technologies that increase efficiency and decrease costs. But none of this innovation comes without change; as an industry we have to evolve organisationally and technically. Those who fail to recognise that face extinction.
"This is like solving a simultaneous equation where the variables are power, cost and density – you need to solve for all three"
The key themes discussed at OFC are an indication of what is to come in optical transport and mirror our top priorities at Cisco.
In the coming year, we expect to see CMOS photonics technology enable lower power pluggables. This is the case with CPAK, but more broadly, we will see this technology find its way into low cost board-to-board interconnect and chassis-to-chassis interconnect.
As an industry, we have made great progress in reducing the cost of transmitting bits over a long distance but much more remains to be done. As bit rates increase to beyond 100 Gigabit, we must look for ways to drive this cost down faster, while decreasing both power and size. This is like solving a simultaneous equation where the variables are power, cost and density – you need to solve for all three.
During the next five years, I think that SDN could be the single biggest disruptor in the transport industry and has the potential to transform network programmability and orchestration.
We will see an entire software industry emerge around SDN, but it is important to note that this is really all about multilayer control – Layer 0 to Layer 3. SDN is not simply an optical transport problem to be solved. The advantage will go to those who are looking at this holistically.
Brandon Collings, CTO of the communications and commercial optical products group at JDSU
I found it interesting that the major network equipment manufactures had a significantly increased presence on the exhibition floor.
"This year’s focus and buzz was all on silicon photonics with researchers leveraging it against nearly every function in telecom and datacom"
I learned a lot about SDN at levels above the photonic network. This is a very complex topic likely to take some time to fully mature within telecom networks; however, the potential values appear compelling.
This year’s focus and buzz was all on silicon photonics with researchers leveraging it against nearly every function in telecom and datacom. I expect it will be interesting for industry watchers how this promising technology evolves within the industry, where it achieves its promise and where it runs into practical roadblocks.
Vladimir Kozlov, CEO of LightCounting
This was the best OFC since 2000. The optical community is once again energised. Some attribute the improved mood to high-value acquisitions of companies LightWire and Nicira that were made last year, but this is just part of the story.
Yes, the potential of silicon photonics and software-defined networking (which LightWire and Nicira were focussed on, respectively) do broaden the horizon for optical technologies in communication networks and data centres. But the excitement is not limited to just these two ideas. All the new - and old or forgotten - ideas, technologies and products once again have a shot at making a difference. Demand for optics is strong and the customers are hungry for innovation.
"Demand for optics is strong and the customers are hungry for innovation"
In contrast to 2000, few people are getting carried away with the excitement. The mood is much more constructive this time and it makes me hope that most of this new energy will not be wasted.
I would not single out a specific technology or application to watch out for in the next few years. All of them have opportunities and challenges ahead. We will keep track of as many developments as we can and make sure that hype does lead the industry off the tracks this time.
Effie Favreau, marketing, Sumitomo Electric
One hundred Gigabit technology is here. Last year there was a lot of hype about 100 Gigabit and now it is reality; vendors have products that are shipping.
Sumitomo and ClariPhy partnered on pluggable coherent modules. Together, we hosted an impressive demonstration with all the components to make pluggable coherent modules available next year.
"For the enterprise/ data centre, vendors requiring low cost, high density equipment really need the CFP4"
One thing I learned from the show is that vendors need to re-purpose their existing equipment. There was much discussion regarding software-enabled applications and passives to enhance the performance of networks and make them more intelligent.
There was the introduction of the CFP2 from several vendors as well as Cisco's CPAK. For the enterprise/ data centre, vendors requiring low cost, high density equipment really need the CFP4. At Sumitomo, we are concentrating our R&D efforts on the CFP4.
See also:
Part 1: Software-defined networking: A network game-changer? click here
Part 3: OFC/NFOEC 2013 industry reflections, click here
Part 4: OFC/NFOEC industry reflections, click here
Part 5: OFC/NFEC 2013 industry reflections, click here
Luxtera's interconnect strategy
Part 1: Optical interconnect
Luxtera demonstrated a 100 Gigabit QSFP optical module at the OFC/NFOEC 2013 exhibition.
"We're in discussions with a lot of memory vendors, switch vendors and different ASIC providers"
Chris Bergey, Luxtera
The silicon photonics-based QSFP pluggable transceiver was part of the Optical Internetworking Forum's (OIF) multi-vendor demonstration of the 4x25 Gigabit chip-to-module interface, defined by the CEI-28G-VSR Implementation Agreement.
The OIF demonstration involved several optical module and chip companies and included CFP2 modules running the 100GBASE-LR4 10km standard alongside Luxtera's 4x28 Gigabit-per-second (Gbps) silicon photonics-based QSFP28.
Kotura also previewed a 100Gbps QSFP at OFC/NFOEC but its silicon photonics design uses two chips and wavelength-division multiplexing (WDM).
The Luxtera QSFP28 is being aimed at data centre applications and has a 500m reach although Luxtera says up to 2km is possible. The QSFP28 is sampling to initial customers and will be in production next year.
100 Gigabit modules
Current 100GBASE-LR4 client-side interfaces are available in the CFP form factor. OFC/NFOEC 2013 saw the announcement of two smaller pluggable form factors at 100Gbps: the CFP2, the next pluggable on the CFP MSA roadmap, and Cisco Systems' in-house CPAK.
Now silicon photonics player Luxtera is coming to market with a QSFP-based 100 Gigabit interface, more compact than the CFP2 and CPAK.
The QSFP is already available as a 40Gbps interface. The 40Gbps QSFP also supports four independent 10Gbps interfaces. The QSFP form factor, along with the SFP+, are widely used on the front panels of data centre switches.
"The QSFP is an inside-the-data-centre connector while the CFP/CFP2 is an edge of the data centre, and for telecom, an edge router connector," says Chris Bergey, vice president of marketing at Luxtera. "These are different markets in terms of their power consumption and cost."
Bergey says the big 'Web 2.0' data centre operators like the reach and density offered by the 100Gbps QSFP as their data centres are physically large and use flatter, less tiered switch architectures.
"If you are a big systems company and you are betting on your flagship chip, you better have multiple sources"
The content service providers also buy transceivers in large volumes and like that the Luxtera QSFP works over single-mode fibre which is cheaper than multi-mode fibre. "All these factors lead to where we think silicon photonics plays in a big way," says Bergey.
The 100Gbps QSFP must deliver a lower cost-per-bit compared to the 40Gbps QSFP if it is to be adopted widely. Luxtera estimates that the QSFP28 will cost less than US $1,000 and could be as low as $250.
Optical interconnect
Luxtera says its focus is on low-cost, high-density interconnect rather than optical transceivers. "We want to be a chip company," says Bergey.
The company defines optical interconnect as covering active optical cable and transceivers, optical engines used as board-mounted optics placed next to chips, and ASICs with optical SerDes (serialiser/ deserialisers) rather than copper ones.
Optical interconnect, it argues, will have a three-stage evolution: starting with face-plate transceivers, moving to mid-board optics and then ASICS with optical interfaces. Such optical interconnect developments promise lower cost high-speed designs and new ways to architect systems.
Currently optics are largely confined to transceivers on a system׳s front panel. The exceptions are high-end supercomputer systems and emerging novel designs such as Compass-EOS's IP core router.
"The problem with the front panel is the density you can achieve is somewhat limited," says Bergey. Leading switch IC suppliers using a 40nm CMOS process are capable of a Terabit of switching. "That matches really well if you put a ton of QSFPs on the front panel," says Bergey.
But once switch IC vendors use the next CMOS process node, the switching capacity will rise to several Terabits. This becomes far more challenging to meet using front panel optics and will be more costly compared to putting board-mounted optics alongside the chip.
"When we build [silicon photonics] chips, we can package them in QSFPs for the front panel, or we can package them for mid-board optics," says Bergey.
"If it [silicon photonics] is viewed as exotic, it is never going to hit the volumes we aspire to."
The use of mid-board optics by system vendors is the second stage in the evolution of optical interconnect. "It [mid-board optics] is an intermediate step between how you move from copper I/O [input/output] to optical I/O," says Bergey.
The use of mid-board optics requires less power, especially when using 25Gbps signals, says Bergey: “You dont need as many [signal] retimers.” It also saves power consumed by the SerDes - from 2W for each SerDes to 1W, since the mid-board optics are closer and signals need not be driven all the way to the front panel. "You are saving 2W per 100 Gig and if you are doing several Terabits, that adds up," says Bergey.
The end game is optical I/O. This will be required wherever there are dense I/O requirements and where a lot of traffic is aggregated.
Luxtera, as a silicon photonics player, is pursuing an approach to integrate optics with VLSI devices. "We're in discussions with a lot of memory vendors, switch vendors and different ASIC providers," says Bergey.
Silicon photonics fab
Last year STMicroelectronics (ST) and Luxtera announced they would create a 300mm wafer silicon photonics process at ST's facility in Crolles, France.
Luxtera expects that line to be qualified, ramped and in production in 2014. Before then, devices need to be built, qualified and tested for their reliability.
"If you are a big systems company and you are betting on your flagship chip, you better have multiple sources," says Bergey. "That is what we are doing with ST: it drastically expands the total available market of silicon photonics and it is something that ST and Luxtera can benefit from.”
Having multiple sources is important, says Bergey: "If it [silicon photonics] is viewed as exotic, it is never going to hit the volumes we aspire to."
Part 2: Bell Labs on silicon photonics click here
Part 3: Is silicon photonics an industry game-changer? click here
Kotura demonstrates a 100 Gigabit QSFP
“QSFP will be the long-term winner at 100 Gig; the same way QSFP has been a high volume winner at 40 Gig”
Arlon Martin, Kotura
The device is aimed at plugging the gap between vertical-cavity surface-emitting laser (VCSEL) -based 100GBASE-SR10 designs that have span 100m, and the CFP-based 100GBASE-LR4 that has a 10km reach.
“It is aimed at the intermediate space, which the IEEE is looking at a new standard for," says Arlon Martin, vice president of marketing at Kotura.
The device is similar to Luxtera's 100 Gigabit-per-second (Gbps) QSFP, also detailed at the OFC/NFOEC 2013 exhibition, and is targeting the same switch applications in the data centre. “Where we differ is our ability to do wavelength-division multiplexing (WDM) on a chip,” says Martin. Kotura also uses third-party electronics such as laser drivers and transimpedance amplifiers (TIA) whereas Luxtera develops and integrates its own.
The Kotura QSFP uses four wavelengths, each at 25Gbps, that operate around 1550nm. “We picked 1550nm because that is where a lot of the WDM applications are," says Martin. “There are also some customers that want more than four channels.” The company says it is also doing development work at 1310nm.
Although Kotura's implementation doesn't adhere to an IEEE standard - the standard is still work in progress - Martin points out that the 10x10 MSA is also not an IEEE standard, yet is probably the best selling client-side 100Gbps interface.
Optical component and module vendors including Avago Technologies, Finisar, Oclaro, Oplink, Fujitsu Optical Components and NeoPhotonics all announced CFP2 module products at OFC/NFOEC 2013. The CFP2 is the next pluggable form factor on the CFP MSA roadmap and is approximately half the size of the CFP.
The advent of the CFP2 enables eight 100Gbps pluggable modules on a system's front panel compared to four CFPs. But with the QSFP, up to 24 modules can be fitted while 48 are possible when mounted double sidedly - ’belly-to-belly’ - across the panel. “QSFP will be the long-term winner at 100 Gig; the same way QSFP has been a high volume winner at 40 Gig,” says Martin.
The QSFP uses 28Gbps pins, which is also called the QSFP28, but Kotura refers to it 100Gbps product as a QSFP. The design consumes 3.5W and uses two silicon photonic chips. Kotura says 80 percent of the total power consumption is due to the electronics.
One of the two chips is the silicon transmitter which houses the platform for the four lasers (gain chips) combined as a four-channel array. Each is an external cavity laser where part of the cavity is within the indium phosphide device and the rest in the silicon photonics waveguide. The gain chips are flip-chipped onto the silicon. The transmitter also includes a grating that sets each laser's wavelength, four modulators, and a WDM multiplexer to combine the four wavelengths before transmission on the fibre.
Kotura's 4x25 Gig transmitter and receiver chips. Source: Kotura
The receiver chip uses a four-channel demultiplexer with each channel fed to a germanium photo-detector. Two chips are used as it is easier to package each as a transmitter optical sub-assembly (TOSA) or receiver optical sub-assembly (ROSA), says Martin. The 100Gbps QSFP will be generally available in 2014.
Disruptive system design
The recent Compass-EOS IP router announcement is a welcome development, says Kotura, as it brings the optics inside the system - an example of mid-board optics - as opposed to the front panel. Compass-EOS refers to its novel icPhotonics chip combining a router chip and optics as silicon photonics but in practice it is an integrated optics design. The 168 VCSELs and 168 photodetectors per chip is massively parallel interconnect, says Martin.
“The advantage, from our point of view of silicon photonics, is to do WDM on the same fibre in order to reduce the amount of cabling and interconnect needed,” he says. At 100 Gigabit this reduces the cabling by a factor of four and this will grow with more 25Gbps wavelength channels used to 10x or even 40x eventually.
“What we want to do is transition from the electronics to the optical domain as close to those large switching chips as possible,” says Martin. “Pioneers [like Compass-EOS] demonstrating that style of architecture are to be welcomed."
Kotura says that every company that is building large switching and routing ASICs is looking at various interface options. "We have talked to quite a few of them,” says Martin.
One solution suited to silicon photonics is to place the lasers on the front panel while putting the modulation, detection and WDM devices - packaged using silicon photonics - right next to the ASICs. This way the laser works at the cooler room temperature while the rest of the circuitry can be at the temperature of the chip, says Martin.
Aurrion mixes datacom and telecom lasers on a wafer
"There is an inevitability of the co-mingling of electronics and optics and we are just at the beginning"
Eric Hall, Aurrion
Aurrion's long-term vision for its heterogeneous integration approach to silicon photonics is to tackle all stages of a communication link: the high-bandwidth transmitter, switch and receiver. Heterogeneous integration refers to the introduction of III-V material - used for lasers, modulators and receivers - onto the silicon wafer where it is processed alongside the silicon using masks and lithography.
In a post-deadline paper given at OFC/NFOEC 2013, the fabless start-up detailed the making of various transmitters on a silicon wafer. These include tunable lasers for telecom that cover the C- and L-bands, and uncooled laser arrays for datacom.
The lasers are narrow-linewidth tunable devices for long-haul coherent applications. According to Aurrion, achieving a narrow-linewidth laser typically requires an external cavity whose size makes it difficult to produce a compact design when integrated with the modulator.
Having a tunable laser integrated with the modulator on the same silicon photonics platform will enable compact 100 Gigabit coherent pluggable modules. "The 100 Gig equivalent of the tunable XFP or SFP+," says Eric Hall, vice president of business development at Aurrion.
Hall admits that traditional indium-phosphide laser manufacturers will likely integrate tunable lasers with the modulator to produce compact narrow-linewidth designs. "There will be other approaches but it is exciting that we can now make this laser and modulator on this platform," says Hall. "And it becomes very exciting when you make these on the same wafer as high-volume datacom components."
Aurrion's vision of a coherent transmitter and a 16-laser array made on the same wafer. Source: Aurrion
The wafer's datacom devices include a 4-channel laser array for 100GBASE-LR4 10km reach applications and a 400 Gigabit transmitter design comprising 2x8 wavelength division multiplexing (WDM) arrays for a 16x25Gbps design, each laser spaced 200GHz apart. These could be for 10km or 40km applications depending on the modulator used. "These arrays are for uncooled applications," says Hall. "The idea is these don't have to be coarse WDM but tighter-spaced WDM that hold their wavelength across 20-80oC."
Coarse WDM-based laser arrays do not require a thermo-electric cooler (TEC) but the larger spacing of the wavelengths makes it harder to design beyond 100 Gigabit, says Hall: "Being able to pack in a bunch of wavelengths yet not need a TEC opens up a lot of applications."
Such lasers coupled with different modulators could also benefit 100 Gigabit shorter-reach interfaces currently being discussed in the IEEE, including the possibility of multi-level modulation schemes, says the company.
Aurrion says it is seeing the trend of photonics moving closer to the electronics due to emerging applications.
"Electronics never really noticed photonics because it was so far away and suddenly photonics has encroached into its personal space," says Hall. "There is an inevitability of the co-mingling of electronics and optics and we are just at the beginning."
OFC/NFOEC 2013 to highlight a period of change
Next week's OFC/NFOEC conference and exhibition, to be held in Anaheim, California, provides an opportunity to assess developments in the network and the data centre and get an update on emerging, potentially disruptive technologies.
Source: Gazettabyte
Several networking developments suggest a period of change and opportunity for the industry. Yet the impact on optical component players will be subtle, with players being spared the full effects of any disruption. Meanwhile, industry players must contend with the ongoing challenges of fierce competition and price erosion while also funding much needed innovation.
The last year has seen the rise of software-defined networking (SDN), the operator-backed Network Functions Virtualization (NFV) initiative and growing interest in silicon photonics.
SDN has already being deployed in the data centre. Large data centre adopters are using an open standard implementation of SDN, OpenFlow, to control and tackle changing traffic flow requirements and workloads.
Telcos are also interested in SDN. They view the emerging technology as providing a more fundamental way to optimise their all-IP networks in terms of processing, storage and transport.
Carrier requirements are broader than those of data centre operators; unsurprising given their more complex networks. It is also unclear how open and interoperable SDN will be, given that established vendors are less keen to enable their switches and IP routers to be externally controlled. But the consensus is that the telcos and large content service providers backing SDN are too important to ignore. If traditional switching and routers hamper the initiative with proprietary add-ons, newer players will willing fulfill requirements.
Optical component players must assess how SDN will impact the optical layer and perhaps even components, a topic the OIF is already investigating, while keeping an eye on whether SDN causes market share shifts among switch and router vendors.
The ETSI Network Functions Virtualization (NFV) is an operator-backed initiative that has received far less media attention than SDN. With NFV, telcos want to embrace IT server technology to replace the many specialist hardware boxes that take up valuable space, consume power, add to their already complex operations support systems (OSS) while requiring specialist staff. By moving functions such as firewalls, gateways, and deep packet inspection onto cheap servers scaled using Ethernet switches, operators want lower cost systems running virtualised implementations of these functions.
The two-year NFV initiative could prove disruptive for many specialist vendors albeit ones whose equipment operate at higher layers of the network, removed from the optical layer. But the takeaway for optical component players is how pervasive virtualisation technology is becoming and the continual rise of the data centre.
Silicon photonics is one technology set to impact the data centre. The technology is already being used in active optical cables and optical engines to connect data centre equipment, and soon will appear in optical transceivers such as Cisco Systems' own 100Gbps CPAK module.
Silicon photonics promises to enable designs that disrupt existing equipment. Start-up Compass-EOS has announced a compact IP core router that is already running live operator traffic. The router makes use of a scalable chip coupled to huge-bandwidth optical interfaces based on 168, 8 Gigabit-per-second (Gbps) vertical-cavity surface-emitting lasers (VCSELs) and photodetectors. The Terabit-plus bandwidth enables all the router chips to be connected in a mesh, doing away with the need for the router's midplane and switching fabric.
The integrated silicon-optics design is not strictly silicon photonics - silicon used as a medium for light - but it shows how optics is starting to be used for short distance links to enable disruptive system designs.
Some financial analysts are beating the drum of silicon photonics. But integrated designs using VCSELs, traditional photonic integration and silicon photonics will all co-exist for years to come and even though silicon photonics is expected to make a big impact in the data centre, the Compass-EOS router highlights how disruptive designs can occur in telecoms.
Market status
The optical component industry continues to contend with more immediate challenges after experiencing sharp price declines in 2012.
The good news is that market research companies do not expect a repeat of the harsh price declines anytime soon. They also forecast better market prospects: The Dell'Oro Group expects optical transport to grow through 2017 at a compound annual growth rate (CAGR) of 10 percent, while LightCounting expects the optical transceiver market to grow 50 percent, to US $5.1bn in 2017. Meanwhile Ovum estimates the optical component market will grow by a mid-single-digit percent in 2013 after a contraction in 2012.
In the last year it has become clear how high-speed optical transport will evolve. The equipment makers' latest generation coherent ASICs use advanced modulation techniques, add flexibility by trading transport speed with reach, and use super-channels to support 400 Gigabit and 1 Terabit transmissions. Vendors are also looking longer term to techniques such as spatial-division multiplexing as fibre spectrum usage starts to approach the theoretical limit.
Yet the emphasis on 400 Gigabit and even 1 Terabit is somewhat surprising given how 100 Gigabit deployment is still in its infancy. And if the high-speed optical transmission roadmap is now clear, issues remain.
OFC/NFOEC 2013 will highlight the progress in 100 Gigabit transponder form factors that follow the 5x7-inch MSA, 100 Gigabit pluggable coherent modules, and the uptake of 100 Gigabit direct-detection modules for shorter reach links - tens or hundreds of kilometers - to connect data centres, for example.
There is also an industry consensus regarding wavelength-selective switches (WSSes) - the key building block of ROADMs - with the industry choosing a route-and-select architecture, although that was already the case a year ago.
There will also be announcements at OFC/NFOEC regarding client-side 40 and 100 Gigabit Ethernet developments based on the CFP2 and CFP4 that promise denser interfaces and Terabit capacity blades. Oclaro has already detailed its 100GBASE-LR4 10km CFP2 while Avago Technologies has announced its 100GBASE-SR10 parallel fibre CFP2 with a reach of 150m over OM4 fibre.
The CFP2 and QSFP+ make use of integrated photonic designs. Progress in optical integration, as always, is one topic to watch for at the show.
PON and WDM-PON remain areas of interest. Not so much developments in state-of-the-art transceivers such as for 10 Gigabit EPON and XG-PON1, though clearly of interest, but rather enhancements of existing technologies that benefit the economics of deployment.
The article is based on a news analysis published by the organisers before this year's OFC/NFOEC event.
Fibre-to-the-NPU: optics reshapes the IP core router
Start-up Compass Electro-Optical Systems has announced an IP core router based on a chip with a Terabit-plus optical interface.
Asaf Somekh, vice president of marketing, showing Gazettabyte Compass-EOS's novel icPhotonics chip
Having an optical interface linking directly to the chip, which includes a merchant network processor, simplifies the system design and enables router features such as real output queuing. The r10004 IP router is in production and is already deployed in an operator's network.
The company's icPhotonics chip integrates 168, 8 Gigabit VCSELs and 168 photodetectors for a bandwidth of 1.344 Terabit-per-second (Tbps) each direction. Eight of the chips are connected in a full mesh, doing away with the need for a router's switch fabric and mid-plane used to interconnect the router cards.
The resulting architecture saves power, space and cost, says Asaf Somekh, vice president of marketing at Compass-EOS. The start-up estimates that its platform's total cost of ownership over five years is a quarter to a third of existing IP core routers.
The high-bandwidth optical links will also be used to connect multiple platforms, enabling operators to add routing resources as required. Compass-EOS is coming to market with a 6U-high standalone platform but says it will scale up to 21 platforms to appear as one logical router.
The 800Gbps-capacity r10004 comes with 2x100 Gigabit-per-second (Gbps) and 20x10Gbps line cards options. The platform has real output queuing where all the input ports' packets are queued with quality of service applied prior to the exit port. The router also supports software-defined networking (SDN) that enables external control of traffic routing.
The company has its own clean room where it makes its optical interface. Compass-EOS has also developed its own ASICs and the router software for the r10004.
Somekh says developing the optical interface has been challenging, requiring years of development working with the Fraunhofer Institute and Tel-Aviv University. One challenge was developing a glue to fix the VCSELs on top of the silicon.
The start-up has raised US $120M with investors such as Cisco Systems, Deutsche Telekom and Comcast as well as several venture capitalist firms.
icPhotonics technology
Compass-EOS refers to its optical interface IC as silicon photonics but a more accurate description is integrated silicon-optics; silicon itself is not used as a medium for light. But its use of embedded optics to the chip has created a disruptive system.
The optical-interconnect addresses two chip design challenges: signal integrity for long transmission lengths and chip input/output (I/O).
With high-speed interfaces, achieving signal integrity across a high-speed line card and between boards is challenging. Routers use a midplane and switch fabric to connect the the router cards within a platform and parallel optics to connect chassis.
Compass-EOS has taken board-mounted optics one step further and integrated VCSELs and photodetectors to the packaged chip. This simplifies the platform by connecting cards using a mesh architecture, and allows scaling by linking systems.
The chip window shows the VCSELs and photodetectors Source: Compass-EOS
The design also addresses chip I/O issues. "The I/O density is about 30x higher than traditional solutions and the gap will grow in future," says Somekh.
Directly attaching the optical interconnect to the CMOS chip overcomes limitations imposed by ball grid array and printed circuit board (PCB) technologies.
Typically data is routed from the host PCB to an ASIC via a ball grid array matrix which has a ball pitch of 0.8mm. Shrinking this further is non-trivial given PCB signal integrity issues. Moreover, each electrical serdes (serialiser/ deserialiser) for data I/O uses at least eight bumps (transmit, receive, signal and ground) occupying a cell of 3.2×1.6 mm. For a 10Gbps device the resulting duplex data density is 2Gbps/mm2, increasing to 5Gbps/mm2 if a 25Gbps device is used, according to Compass-EOS.
The start-up says its optical-interconnect achieves a chip I/O of 61Gbps/mm2. "This will increase to 243Gbps/mm2 once we move to 32Gbps."
The resulting design uses 10 percent of the total CMOS area for I/O. "This is a more efficient chip design," says Somekh. "Most of the silicon is used for logic tasks."
The serdes on chip still need to interface to hundreds of 8Gbps channels. And moving to 32Gbps will present a greater challenge. In comparison, silicon photonics promises to simplify the coupling of optics and electronics.
Another design challenge is that the VCSELs are co-packaged with a large chip consuming 30-50W and generating heat. The design needs to make sure that the operating temperature of the VCSELs is not affected by the heat from the chip.
This is another promised advantage of silicon photonics where the operating temperature of the optics and silicon are matched.
Analysts' perspective
Gazettabyte asked two analysts - IDC's Vernon Turner and ACG Research's Eve Griliches - about the significance of Compass-EOS's announcement. The analysts were also asked for their views on the router's modularity, the total cost of ownership claims, the support for SDN and real output queueing, and whether the platform will gain market share from the IP core router incumbents.
IDC
Vernon Turner, senior vice president & general manager enterprise computing, network, telecom, storage, consumer and infrastructure.
One of the hardest places to innovate in the ICT (information and communications technology) world is at or around the speed of light. Anytime you can make things run faster, the last hurdle tends to be the speed by which things travel over an optical network.
Therefore, to see something that changes the form factor of a network router and innovates at the interconnect speed, it may be able to disrupt a significant part of the network industry.
"Separating the interconnect with the physical building block is huge. It means that you scale the pieces that you need, when and where you want them; this is not just a repackaging announcement"
Building the capacity of a router as needed is great for service providers and large enterprises since you deploy capacity only as you need it. Second, by using a photonics interconnect, the speed and distance over which two devices can sit is enhanced greatly, changing the way one builds network infrastructures.
Separating the interconnect with the physical building block is huge. It means that you scale the pieces that you need, when and where you want them; this is not just a repackaging announcement.
Regarding the total-cost-of-ownership claims, if these are valid, they are of a magnitude that does fit into a 'disruptive innovation' class where it will deliver network services to an underserved market and create new network services markets.
SDN is the latest buzzword [regarding the router's support for SDN]. But it is the last part of the virtualised data centre as the compute and I/O have already been figured out. SDN is not new, but the need to separate the data plane from the control plane for the service provider industry means that they can begin to create network services through virtualisation without impacting the network performance, something that already happens in server and storage performance.
Existing core router vendors use their own ASIC designs as the last-stop differentiation, so to do this [as Compass-EOS has done] on merchant silicon could have wide implications on router commoditisation, or at least at a faster rate than current trends.
ACG Research
Eve Griliches, vice president of optical networking
As to the significance of the announcement, it is not huge in the scheme of things, but it does bring the optical component use of replacing a backplane to market earlier than what has been quoted to ACG Research.
"Virtual output queueing is a smart way to do quality of service"
In theory, the router should be a smaller footprint which results in better total cost of ownership due to the optical modules. The advantage with this optical patch-panel approach is that it allows a much higher bandwidth to cross the backplane which is now an optical interconnect. That means you don't have to do as much flow control, or drop as many packets, or keep the utilization of the router so low. You can bring up the utilisation rate from let's say 15 percent to maybe 25 percent or higher. All that results in lower total cost of ownership in theory.
SDN in a bit nebulous. Virtual output queueing is a smart way to do quality of service, but there are key software features like how many BGP (border gateway protocol) peers are supported, multicast capability, as well as signaling for MPLS (multiprotocol label switching), do they support RSVP-TE (resource reservation protocol - traffic engineering) or LDP (label distribution protocol)? Or both? Building a real router still takes years of work.
Faster interconnects are the way to go across routing and optical platforms, period. This [Compass-EOS platform] can help. Do I see this optical piece fitting nicely into an already existing router? Yes. I think if that doesn't happen, they will have a bit of an uphill battle nudging the incumbents.
On the other hand, if full router functionality is not needed at some junctures, as we've seen with the LSR (label switch router) technology, then they may have a place in the network. But operators don't like to play around with their routed network too much, so it may be greenfield application that are mostly available to them [Compass-EOS] initially.
OFC/NFOEC 2013: Technical paper highlights
Source: The Optical Society
Network evolution strategies, state-of-the-art optical deployments, next-generation PON and data centre interconnect are just some of the technical paper highlights of the upcoming OFC/NFOEC conference and exhibition, to be held in Anaheim, California from March 17-21, 2013. Here is a selection of the papers.
Optical network applications and services
Fujitsu and AT&T Labs-Research (Paper Number: 1551236) present simulation results of shared mesh restoration in a backbone network. The simulation uses up to 27 percent fewer regenerators than dedicated protection while increasing capacity by some 40 percent.
KDDI R&D Laboratories and the Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Spain (Paper Number: 1553225) show results of an OpenFlow/stateless PCE integrated control plane that uses protocol extensions to enable end-to-end path provisioning and lightpath restoration in a transparent wavelength switched optical network (WSON).
In invited papers, Juniper highlights the benefits of multi-layer packet-optical transport, IBM discusses future high-performance computers and optical networking, while Verizon addresses multi-tenant data centre and cloud networking evolution.
Network technologies and applications
A paper by NEC (Paper Number: 1551818) highlights 400 Gigabit transmission using four parallel 100 Gigabit subcarriers over 3,600km. Using optical Nyquist shaping each carrier occupies 37.5GHz for a total bandwidth of 150GHz.
In an invited paper Andrea Bianco of the Politecnico de Torino, Italy details energy awareness in the design of optical core networks, while Verizon's Roman Egorov discusses next-generation ROADM architecture and design.
FTTx technologies, deployment and applications
In invited papers, operators share their analysis and experiences regarding optical access. Ralf Hülsermann of Deutsche Telekom evaluates the cost and performance of WDM-based access networks, while France Telecom's Philippe Chanclou shares the lessons learnt regarding its PON deployments and details its next steps.
Optical devices for switching, filtering and interconnects
In invited papers, MIT's Vladimir Stojanovic discusses chip and board scale integrated photonic networks for next-generation computers. Alcatel-Lucent's Bell Labs' Nicholas Fontaine gives an update on devices and components for space-division multiplexing in few-mode fibres, while Acacia's Long Chen discusses silicon photonic integrated circuits for WDM and optical switches.
Optoelectronic devices
Teraxion and McGill University (Paper Number: 1549579) detail a compact (6mmx8mm) silicon photonics-based coherent receiver. Using PM-QPSK modulation at 28 Gbaud, up to 4,800 km is achieved.
Meanwhile, Intel and the UC-Santa Barbara (Paper Number: 1552462) discuss a hybrid silicon DFB laser array emitting over 200nm integrated with EAMs (3dB bandwidth> 30GHz). Four bandgaps spread over greater than 100nm are realised using quantum well intermixing.
Transmission subsystems and network elements
In invited Papers, David Plant of McGill University compares OFDM and Nyquist WDM, while AT&T's Sheryl Woodward addresses ROADM options in optical networks and whether to use a flexible grid or not.
Core networks
Orange Labs' Jean-Luc Auge asks whether flexible transponders can be used to reduce margins. In other invited papers, Rudiger Kunze of Deutsche Telekom details the operator's standardisation activities to achieve 100 Gig interoperability for metro applications, while Jeffrey He of Huawei discusses the impact of cloud, data centres and IT on transport networks.
Access networks
Roberto Gaudino of the Politecnico di Torino discusses the advantages of coherent detection in reflective PONs. In other invited papers, Hiroaki Mukai of Mitsubishi Electric details an energy efficient 10G-EPON system, Ronald Heron of Alcatel-Lucent Canada gives an update on FSAN's NG-PON2 while Norbert Keil of the Fraunhofer Heinrich-Hertz Institute highlights progress in polymer-based components for next-generation PON.
Optical interconnection networks for datacom and computercom
Use of orthogonal multipulse modulation for 64 Gigabit Fibre Channel is detailed by Avago Technologies and the University of Cambridge (Paper Number: 1551341).
IBM T.J. Watson (Paper Number: 1551747) has a paper on a 35Gbps VCSEL-based optical link using 32nm SOI CMOS circuits. IBM is claiming record optical link power efficiencies of 1pJ/b at 25Gb/s and 2.7pJ/b at 35Gbps.
Several companies detail activities for the data centre in the invited papers.
Oracle's Ola Torudbakken has a paper on a 50Tbps optically-cabled Infiniband data centre switch, HP's Mike Schlansker discusses configurable optical interconnects for scalable data centres, Fujitsu's Jun Matsui details a high-bandwidth optical interconnection for an densely integrated server while Brad Booth of Dell also looks at optical interconnect for volume servers.
In other papers, Mike Bennett of Lawrence Berkeley National Lab looks at network energy efficiency issues in the data centre. Lastly, Cisco's Erol Roberts addresses data centre architecture evolution and the role of optical interconnect.
Optical transceiver market to grow 50 percent by 2017
- The optical transceiver market will grow to US $5.1bn in 2017
- The fierce price declines of 2012 will lessen during the forecast period
- Stronger traffic growth could have a significant positive effect on transceiver market growth
"The price declines in 2012 were brutal but they will not happen again [during the forecast period]"
Vladimir Kozlov, LightCounting
The global optical transceiver market will grow strongly over the next five year to $5.1bn in 2017, from $3.4bn in 2012. So claims market research company, LightCounting, in its latest telecom and datacom forecast.
"That [market value] does not include tunable lasers, wavelength-selective switches, pump lasers and amplifiers which will add some $1bn or $2bn more [in 2017]," says Vladimir Kozlov, CEO of LightCounting.
One key assumption underpinning the forecast is that competitive pressures will ease. "The price declines in 2012 were brutal but they will not happen again [during the forecast period]," says Kozlov.
Optical transceivers
The optical transceiver market saw price declines as high as 30 percent last year. These were not new products ramping in volume where sharp price declines are to be expected, says Kozlov. Last year also saw fierce competition among the service providers while the steepest price declines were experienced by the telecom equipment makers.
One optical transceiver sector that performed well last year is high-speed optical transceivers and in particular Ethernet.
The 100 Gigabit Ethernet (GbE) market saw revenue growth due to strong demand for the 100GBASE-LR4 10km transceiver even though its unit price declined 30 percent. This is a sector the Chinese optical transceiver players are eyeing as they look to broaden the markets they address.
One unheralded market that did well was 40 Gigabit transceivers for telecoms and the data centre. "This is 40 Gig short reach mostly - up to 100m - but also 10km reach transceivers did well in the data centre," says Kozlov.
LightCounting expects the steady growth of 40GbE to continue; 40GbE transceivers use 10 Gig technology co-packaged into one module, offer improved port density and have a lower power and cost compared to four 10GbE transceivers.
Even the veteran 10GbE market continues to grow. Some 7-8M 10GbE short reach and long reach units were sold in 2012 growing to 10M units this year.
Meanwhile, the 100 Gigabit coherent long-haul transponder market was small in 2012. The optical vendors only started selling in volume last year and most of the system vendors manufacture their own 100 Gigabit-per-second (Gbps) designs using discrete components. "Those companies that sell modulators and receivers for 100 Gig did really well in 2012," says Kozlov.
LightCounting expects the 100Gbps coherent transponder market will grow in 2013 as system vendors embrace more third-party 100 Gig transponders. "We estimate that the optical transceiver vendors captured 10-15 percent of the 40 and 100 Gig market and this will grow to 18-20 percent in 2013," says Kozlov.
Other markets that grew in 2012 include optical access. The fibre-to-the-x (FTTx) continues to grow in terms of units shipped, with transceivers and board optical sub-assembly (BOSA) designs sharing the volumes.
LightCounting says that the number of optical network units (ONU) exceeded by more than double the number of FTTx subscribers added in 2012: 35-40M ONU transceivers and BOSAs compared to 15M new subscribers.
The result was a market value of $700M in 2012 compared to $300M in 2009. But because of the excess in shipments compared to new subscribers, Kozlov expects the FTTx market to slow down. "That is probably a sure sign that it is going to grow again," he quips.
Market expectations
Kozlov will be watching how the optical interconnect market does this year. The active optical cable market did well in 2012 and this is likely to continue. Kozlov is interested to see if silicon photonics starts to make its mark in the transceiver market, citing as an example Cisco's in-house silicon photonics-based CPAK transceiver. He also expects the 40G and 100Gbps module makers to do well.
LightCounting stresses the wide discrepancy between video traffic growth through 2017 as forecast by Bell Labs and by Cisco Systems. This is important because the optical transceiver forecast model developed by LightCounting is sensitive to traffic growth. LightCounting has averaged the two forecasts but if video traffic grows more quickly, the overall transceiver market will exceed the market research company's 2017 forecast.
Another reason why Kozlov is upbeat about the market's prospects is that while the system vendors suffered the sharpest price declines - up to 35 percent in 2012 - this will not continue.
The sharp falls in equipment prices were due largely to the fierce competition provided by the Chinese giants Huawei and ZTE. But relief is expected with government initiatives in Europe and the United States to limit the influence of Huawei and ZTE, says Kozlov.
The U.S. government has effectively restricted sales of Huawei and ZTE networking equipment to major U.S. carriers due to cyber security concerns, while the European Commission has determined that Huawei and ZTE are both inflicting damage on European equipment vendors by dumping products onto the European market.
Q&A with Kotura's CTO: Integration styles and I/O limits
The second, and final part, of the Q&A with Mehdi Asghari, CTO of silicon photonics start-up, Kotura.
Part 2 of 2
"When do the big players adopt a new technology and go from an electrical to an optical solution? In my experience, usually when they absolutely have to."
Mehdi Asghari, CTO, Kotura
Q: Silicon photonics comes in two integration flavours: the monolithic approach where the modulators and detectors are implemented monolithically while the lasers are coupled externally (e.g. Kotura and Luxtera); and heterogeneous integration where III-V materials such as indium phosphide are bonded to the silicon to form a hybrid design yet are grown on a single die (e.g. Aurrion). Does one approach have an advantage?
A: I have a III-V background and converted to silicon photonics over 15 years ago. The key issue here is what are you trying to do? Why are we going from III-V processing to silicon? Is it the yield and process maturity or the device performance for actives?
If it is the former, then heterogeneous integration does not really solve the problem since you are still processing III-V devices and are likely to need multiple fabs to do it. If it is the latter then you should stick to III-V wafers.
The fact is that silicon provides passive performance that is far superior to III-V while the active performance – the detector and modulator - is good enough. In fact our germanium detectors could be better and our electro-absorption modulators can be lower power and exhibit a broader working spectral range.
We have seen repeatedly that being good enough is all that silicon has to show it can do to win and that it is certainly doing.
"It is not enough to offer a 10%, 20% or even a 50% cost saving when you are offering the customer a brand new solution that comes with all the risks and unknowns associated with that technology."
Kotura has developed components for telecom (variable optical attenuators, and the functions needed for a 100 Gig coherent receiver) yet its focus is on datacom. Why is that?
We started in telecom as we looked for low hanging fruit that could give us a good margin and an easy start in our early days. This is important for a start-up with a new technology. The well-entrenched incumbent technologies are hard to displace.
You have to find an application with a clear value proposition to get started. Once you have established yourself, your supply chain and manufacturing infrastructure, you can take on more challenging and larger market opportunities.
We see certain areas in datacom that are not well served by either the short reach optics or the telecom grade solutions. Extended reach data centre is one key area where short-reach optics based on VCSELs cannot cover the reach needed and conventional telecom solutions are inherently over-engineered and do not meet the power, cost and size needed.
We think silicon photonics can play a key role here as a starting point in datacom. A key advantage of our platform here is that we can do WDM [wavelength division multiplexing] and hence offer 100 Gig on a single fibre (per direction). This is a major cost saving for longer reaches (>>50m) deployed in such links.
There are some big system players with silicon photonics (Cisco Systems, Alcatel-Lucent) and several small merchant silicon photonics players, such as the companies mentioned in the previous question, which must develop products to sell while funding the development of their technologies. How do you expect the silicon photonics marketplace to evolve, especially now that the technology is being more widely embraced?
For silicon photonics to succeed commercially, we need a multitude of vibrant and successful players in the field. Some of these can be start-ups that lead the innovation in technology and manufacturing but others can be larger organisations that have invested to service an internal need or leverage an existing dominance in the market.
There is room and a necessity for both. It takes a village to raise a child. One single company will not turn silicon photonics into a successful commercial reality.
Cisco Systems has been talking about its proprietary CPAK transceiver. Here is an example of a system vendor using in-house silicon photonics for its own use. Why do you think about such a development? And is Kotura being approached by equipment vendors that want to work with you to develop a custom design?
It is not new for a large company like Cisco to try and make sure that is has its own proprietary components to go into its systems to protect their product and their margins. We see that in all industries.
In terms of other companies coming up with their own proprietary solutions, we do see more and more of this - and a lot more this year than last year - especially when you come off the telecom bandwagon and into the datacom environment: data centres and high-performance computing.
That is because the customer is in charge of the entire environment, the two ends of the link, they can leverage more value from the solution you have to offer without worrying about standards. This is one way for systems companies to leverage value from components.
People are starting to see that the conventional technologies they have deployed are hitting a wall. When they are deploying a new solution they are rethinking their hardware strategy, and how they leverage it to add more value and differentiation to their system.
New ways to architect systems are becoming possible. If you are able to avoid limitations such as distance between the processor and memory, the router and switches and so on, you can come up with a very different architecture for your system and solution.
When do the big players adopt a new technology and go from an electrical to an optical solution? In my experience, usually when they absolutely have to. Most people don't adopt a new solution until they really, really need to; when the value proposition completely outweighs the risk.
It is not enough to offer a 10%, 20% or even a 50% cost saving when you are offering the customer a brand new solution that comes with all the risks and unknowns associated with that technology.
You have to offer them something new, to enable a new application, to add value by enabling a feature, something they can leverage in their product.
When you say systems people adopt new technology when they hit a wall, can you highlight examples of these hurdles?
When you look at the adoption of optics coming from the copper-dominated connectivity, it is very interesting.
Originally, for optics to work its way into the copper world, it had to hide itself and look like a copper solution. People had no idea how to create connectors and they were worried about fibre. So it was disguised as a copper solution.
As customers have got used to it, we can now come out and be more open. We can now do more innovative things with optical transceivers. If you look at the adoption rate, it is being accelerated by customers' demand such as 25 Gigabit signalling.
We can see that the processors and the ASICs - a switch from Broadcom or a processor from Intel or AMD - they are running into I/O [input/ output] density bottlenecks. The chip area is pretty constant, the packages are about the standard size, the number of pins are going beyond what they can support, they have to ramp up the pin rate to about 25 Gigabit-per-second (Gbps), while there are also some 10Gbps pins.
But the number of 25Gbps pins are becoming so high, potentially many hundreds, that they are not going to be able to trace them into the PCB (printed circuit board). The PCB can only take a 25Gbps signal for about 4 inches (~10cm) and then you need serdes [serialiser/ deserialiser) and repeaters.
You may imagine a current router or switch ASIC having ten 25Gbps pins and 100 10Gbps pins. The 10Gbps pins I can take to the edge and use 10Gbps transceivers; and the ten 25Gbps pins I can still do something about it. I may need a lot of electronics and serdes, and use pre-emphasis and equalisation.
But the next generation, when it becomes 100 25Gbps pins, you just cannot do that at the board level. That is where we will start to have to use optics close to the chip.
Will they go for very compact transceivers that sit next to the ASIC or would they try and co-package it with the ASIC?
My perception is that the first generation will be next to the ASIC. People will not integrate an unknown technology into a multi-billion dollar business, they will hedge their bets and have an external solution that offers them some level of assurance that if one solution does not work, they can change to another. But once they get used to it, they can start to integrate these in a multi-chip module solution.
What are the timescales?
I see transceivers next to the ASICs being deployed around 2017-18, maybe a bit sooner, with the co-packaging around 2018-20. People are already talking about it but usually these things take longer.
For part 1 of the Q&A, click here
Further reading:
Silicon photonics: Q&A with Kotura's CTO
A Q&A with Mehdi Asghari, CTO of silicon photonics start-up, Kotura. In part one, Asghari talks about a recent IEEE conference he co-chaired that included silicon photonics, the next Ethernet standard, and the merits of silicon photonics for system design.
Part 1
"Photons and electrons are like cats and dogs. Electrons are dogs: they behave, they stick by you, they are loyal, they do exactly as you tell them, whereas cats are their own animals and they do what they like. And that is what photons are like."
Mehdi Asghari, CTO of Kotura
Q: You recently co-chaired the IEEE International Conference on Group IV Photonics that included silicon photonics. What developments and trends would you highlight?
A: This year I wanted to show that silicon photonics was ready to make a leap from an active area of scientific research to a platform for engineering innovation and product development.
To this end, I needed to show that the ecosystem was ready and present. Therefore, a key objective was to get the industry more involved with the conference. "This has always been a challenge," I was told.
To address this issue I asked my co-chair, MIT's Professor Jurgen Michel, that we appoint joint-session chairs, one from industry and one from academia. We got people we knew from Google, Oracle and Intel as co-chairs, and paired them with prominent academics and asked them to ensure that there were an equal number of industry-invited talks in the schedule. We knew this would be a major attraction to industry attendees. We also got the industry to fund the conference at a level that set an IEEE record.
A key highlight of the show was a boat cruise journey on San Diego bay with Dr. Andrew Rickman as speaker, sharing his experiences and thoughts about setting up the first silicon photonics company - Bookham Technology - over 20 years ago.
Among other distinguished industry speakers we had Samsung telling us of the role of silicon photonics in consumer applications, Broadcom on the need for on-chip optical communication, Cisco on the role of silicon photonics in the future of the Internet, and Google on its broadband fibre-to-the-home (FTTh) initiative and what silicon photonics could offer in this area.
Oracle also shared its latest development in silicon photonics and the application of the technology in their systems, while Luxtera discussed the latest developments in its CMOS photonics platform, particularly the 4x25 Gigabit-per-second (Gbps) platform.
We also heard about the latest germanium laser development at MIT and had an invited speaker to talk about what III-V devices could do and to provide a comparison to silicon to make sure we are not blinded by our own rhetoric.
We ended up with a record number of attendees for the conference and, perhaps more importantly, close to half from industry; a record and vindicated my motivation and perspective for the conference and that silicon photonics is ready and coming.
Was there a trend or presentation at the IEEE event that stood out?
There are two areas creating excitement. One is the germanium laser. This is a topic of significant interest because these devices can operate at very high temperatures and therefore they can be next to the processor or ASIC. This can be a game-changer in how we envisage photonics and electronics being integrated.
We have germanium detectors and at Kotura we are working very hard to get a germanium electro-absorption modulator. We have shown this device can be extremely small and low power. And it can operate at very high speed - we have observed 3dB bandwidths in excess of 70GHz which means you can think of 100 Gigabit direct modulation for a device only 40 microns long and with a capacitance of a few femtofarads. So in terms of RF power, the dissipation of this device is virtually zero.
I would say the MIT group is probably leading the [germanium laser] efforts. They reported on room-temperature, current-driven laser emission which is very exciting. The efficiency of these lasers are still low for commercial applications; they probably have to improve by a factor of 100 or so. But given the progress we've seen in the last two years, if they keep going at that pace we may have viable germanium lasers in a couple of years. Then someone in industry has to take that on and turn it into a product and that is usually the hardest part.
This is exciting because that enables us to forget about off-the-chip lasers and integrate them in the device. We can then give up a whole bunch of problems. For example, the high temperature operation of the III-V devices is a real limit for us. Electronic devices can give off 100W and operate at 120oC, whereas optical devices often have to be stabilised, may go through multiple packaging layers, and the heat dissipation is usually directly related to cost.
If you could end up with a germanium laser that is happy at high temperatures - and we know our detectors and modulators work at high temperatures, and we know we can use electronic packaging to package these devices - then we can put these lasers next to the processor and address the bandwidth limitations that ASICs are facing today.
"Wavelength division multiplexing (WDM) is effectively a zero-power gearbox"
What was the second area?
The other area that was very interesting is graphene, a new material people are starting to work with and putting on silicon. They [researchers] are showing very low power, very high speed operation. It is still at a research level but that is another area we should watch.
The IEEE has started a group looking at the next speed Ethernet standard. No technical specification has been mentioned but it looks that 400 Gigabit Ethernet (GbE) will be the approach. Do you agree and what role can silicon photonics play in making the next speed Ethernet standard possible?
Industry is busy arguing about the different ways of doing 100 and 400GbE, and perhaps forgetting the fact that we have been here before.
The simple fact is that people always go for higher bit rate when it is cost-efficient and power-efficient to do so. After that, wavelengths are used.
Wavelength division multiplexing (WDM) is effectively a zero-power 'gearbox', mixing the signals in the optical domain. You do pay a power penalty for it in the form of photons lost in the multiplexer and demultiplexer. However that is not significant compared to the power consumption of an electronics gearbox chip.
Once we have exploited line rate and wavelength division multiplexing, we come to more complex modulation formats and pay the associated power and complexity penalty. Of course, more channels of fibre can always carry more information bandwidth but that is just a brute force solution that works while density and bandwidth requirements are moderate.
I think the right 100 Gigabit is based on a WDM 4x25 Gig solution. This can then scale to 400 Gigabit by adding more wavelengths, and can then scale to 1.6 Terabits. We have already demonstrated this in a single chip and will demonstrate this later in the form of a QSFP 100Gbps.
How does the interface scale to 1.6Tbps?
Our devices are capable of running at 40 or 50Gbps, depending on the electronics. The electronics is going to limit the speed of our devices. We can very easily see going from four channels at 25Gbps to 16 channels at 25Gbps to provide a 400 Gigabit solution.
We can also see a way of increasing the line rate to 50Gbps perhaps, either a straightforward NRZ (non-return-to-zero) line rate or some people are talking about multi-level modulation, PAM-4 (pulse amplitude modulation) type of stuff, to get to 50Gbps.
The customers we are talking to about 100Gbps are already talking about 400Gbps. So we can see 16x25Gbps, or 8x50Gbps if that is the right thing to do at the time based on the availability of electronics.
To go to 1.6 Terabit transceivers, we envisage something running at 40Gbps times 40 channels or 50Gbps times 32 channels. We already have done a single receiver chip demonstrator that has 40 channels, each at 40Gbps.
These things in silicon are not a big deal. The III-V guys really struggle with yield and cost. But you can envisage scaling to that level of complexity in a silicon platform.
Silicon photonics is spoken of not just as an optical platform like traditional optical integration technologies, but also as a design approach, making use of techniques associated with semiconductor design. The implication is that the technology will enable designs and even systems in a way that traditional optics can't. Can you explain how silicon photonics is a design approach and just what the implications are?
I think this is a key promise of silicon photonics, but perhaps one that has been oversold in recent years.
The key here is that given the maturity of the silicon processing capabilities, process simulation tools available and inherent properties of silicon, it is possible to predict the performance of the optical circuits far better in this platform than in any other before it. I think this is true and very valuable, potentially even a game changer.
However, we have to realise that there still remains an inherent difference between electrons and photons and their behavior in such circuits. Photons remain in a quantum world in such circuits, where the wavelength of light is comparable to feature sizes we manufacture. Hence we are dealing with a statistical quantum process whether we like it or not.
In summary, silicon will be a key enabler for on-chip system design, but it is too early for the university courses to stop graduating photonics PhDs!
So there is an advantage to silicon photonics but are you saying it is not that simple as using mature semiconductor design techniques?
Photons and electrons are like cats and dogs. Electrons are dogs: they behave, they stick by you, they are loyal, they do exactly as you tell them, whereas cats are their own animals and they do what they like. And that is what photons are like.
So it is really hard to predict what a photon does. The dimensions that we use for the structures we make are of the size of the wavelength of a photon. And that means it is more of a hit-and-miss process - there is always stray light, the stray light has a habit of interfering and you can always get unpredicted results.
When I interact with my electronic partners I find that they go through 6-9 months of very detailed simulation. They have very complex simulation tools.
When you come to photonics for sure we can borrow some of these simulation tools, we can simulate the process because we are using silicon. However some of the tolerances that we need are beyond what the silicon guys need, and the way the photons behave is very different. So in the end we don't spend 9 months simulating; we spend a month simulating and 3 months running the process and optimising it and re-running it and re-optimising it.
We end up with a reverse situation where the design is only 3 months, and the interaction with the designer and the manufacturing process is a 9-month process. So this is more of an iterative process. It is not as mature and a little bit more statistical.