How to shepherd a company’s technologies for growth
CTO interviews part 3: Dr Julie Eng
- Eng is four months into her new role as CTO of Coherent.
- Previously, she headed Finisar’s transceiver business and then the 3D sensing business, first at Finisar and then at II-VI. II-VI changed its name to Coherent in September 2022
- “CTO is one of these roles that has no universal definition,” says Eng
ulie Eng loved her previous role.
She had been heading II-VI’s (now Coherent’s) 3D sensing unit after being VP of engineering at Finisar’s transceiver business. II-VI bought Finisar in 2019.
She moved across to a new 3D sensing business while still at Finisar. The 3D sensing unit was like a start-up within a large company, she says.
II-VI and Finisar had been competitors in the 3D sensing market. Eng headed the combined units after Finisar’s acquisition.
She enjoyed the role and wasn’t looking to change when the CEO asked her to become Coherent’s CTO.
“To become CTO of the new Coherent – to help define the future of this company which is a five-plus going on six billion dollar company – that is pretty exciting,” says Eng.
The “New” Coherent
Coherent combines a broad portfolio of technologies from II-VI, Finisar, and the firm Coherent which II-VI acquired in 2022.
Just within lasers, Coherent’s portfolio spans from devices 1mm wide that are sold into mobile phones to the former Coherent’s lasers that are meters wide and used for OLED manufacturing.
Being CTO is different from Eng’s line-management roles, which had set, tangible annual goals.
Her role now is to shepherd the company’s technologies and grow the business over the long term.
Eng has been familiarising herself with the company’s technologies. To this aim, Eng is drawing on deep technological expertise across the company’s units.
Luckily, lasers are already covered, she quips.
“One of the things that I always somehow had a knack for is interacting with customers, sensing opportunities, and then figuring out how our technologies can help customers solve their problems,” says Eng.
It is a skill she successfully transferred to the consumer – 3D sensing – business but now it will be needed on a broader scale.
Eng is also making connections across technology units within the company as she seeks to identify new technologies and new market opportunities.
Her CTO role also allows her to engage with every Coherent customer across the company’s many markets.
She admits being CTO is challenging. One issue is grappling with the breadth of technologies the company has. Another is how to assess her works’ impact.
She and the CEO have discussed how best to use her time to benefit the company. Eng has also talked to other companies’ CTOs about the role and what works for them.
“It’s very interesting; CTO is one of these roles that has no universal definition,” says Eng.
Technologies to watch
Eng highlights several developments when asked about noteworthy technologies.
For communications, this is the year when 200 gigabits per lane will likely be achieved.
“The first transceivers I worked on were [SONET/SDH] OC-3 which is 155 megabits per second (Mbps),” she says. “Is wasn’t even a transceiver back then; it was discrete transmitters and receivers.”
That the industry has accelerated technology to achieve multiple lanes of 200 gigabit-per-second (Gbps) in a pluggable module is remarkable, she says.
Eng also notes Coherent’s work on a continuous-wave laser integrated with a Mach-Zehnder modulator – a DMZ – to enable 200 gigabits per lane.
The company is also active in life sciences and health monitoring. Communications, especially during the pandemic, showed its importance in people’s lives. “But life sciences and health-related products have a much more direct impact on people,” says Eng. “That is not something I’ve had direct exposure to.”
Life sciences and health monitoring is a segment where optics and optical devices will play a growing role over time.
Medical devices often originate in research environments such as hospital labs before becoming medical instruments. From the lab, they go to clinical. “What we are talking about here is going from lab to clinical to therapeutics,” she says.
The US Chips Act also heartens Eng: “It was about time for the US to prioritise semiconductors.”
Low-power coherent DSPs
Coherent and ADVA jointly developed a low-power coherent digital signal processor (DSP) and optics design for a 100-gigabit ZR (100ZR) design that fits within a QSFP28 module.
“We have an internal DSP team, and they are developing DSPs for the coherent optics market,” says Eng, adding that having the design team gives Coherent options.
Meanwhile, the debate about direct detection technology versus coherent optics continues.
As optical lane speed increases from 100 gigabits to 200 gigabits, the question remains what reach will direct detection achieve before running out of steam?
With 200 gigabits per lane, 800 gigabit modules can be achieved using four optical lanes, while for 1.6 terabits, eight lanes will be used.
Eng is confident that direct detection will support 10km at these speeds. Beyond 10km, direct detection becomes much more of a challenge, and coherent is an option.
“The real question is will coherent optics meet the size, cost and power consumption expectations of the data centre customers on a timeframe that meets their needs,” says Eng.
Having in-house DSP technology means Coherent can undertake design trade-offs and make the right decisions, she says.
After 1.6 terabits, the design options include increasing the lane rate, using more than eight channels or adopting more advanced modulation schemes.
“We look at the application, the timeline that the product needs to be released, the readiness of the technology, we do measurements – simulations – and we make objective decisions based on the results,” says Eng.
Whatever the prevalent technology is, says Eng, that technology will continue to improve since that is the livelihood of many companies.
“All of us, as an industry, are going to put our all into extending the technologies we currently have,” says Eng. So, when it comes to direct detection versus coherent, everyone will push direct detect technology as far as possible.
“Getting up to 1.6 terabits [using direct detect], that is pretty good,” says Eng. “That is going to last us a pretty long time.”
Materials
Coherent’s toolbox of material systems covers indium phosphide, silicon photonics, and gallium arsenide. It also has silicon carbide, a semiconductor suited for high-power transistors used for power electronics applications.
“We have all the technologies, we use the best technology for the product, and we use good engineering judgement,” says Eng.
Rather than favour indium phosphide or silicon photonics, Eng’s segmentation starts with whether the design is directly modulated or externally modulated.
Until now, up to 50 gigabits per lane has been well served by directly modulated lasers. This has used indium phosphide or, in the case of VCSELs, gallium arsenide.
“In general, directly modulated is the lower cost because the die is tiny, and often it is the lowest power,” says Eng.
But increasing the speed beyond 50Gbps gets more complicated with directly modulated lasers. This is where externally modulated lasers come in.
“Once you are already talking about an externally modulated solution, we start looking at the trade-offs between indium phosphide and silicon photonics,” says Eng.
The laser remains indium phosphide, so the bake-off concerns the modulator and the passive optics.
What indium phosphide brings is better electro-optics performance, while silicon photonics brings the benefits of integration.
“So if there is a high-lane count – lots of passives – or an opportunity to use one laser over multiple modulators, these can be complicated designs, and silicon photonics can help reduce the size,” says Eng.
Pluggables and co-packaged optics
With 200 gigabits per lane becoming available, there is a clear roadmap for 800-gigabits and 1.6-terabit pluggables.
“Customers like pluggables, and I don’t think people should underestimate that,” says Eng, adding that continued innovation will extend their lifetime.
“There are flyover cables between the switch ASIC and the modules, vertical line cards have been proposed, and we have shown board-mounted optical assemblies,” she says.
At some point, co-packaged optics may be the right solution, says Eng. But that will depend on the application’s specification, issues such as bandwidth, size, cost, power consumption and reliability.
“People will only transition to optical input-output when extending pluggables doesn’t make sense anymore,” says Eng. “I think it is probably five-plus years away, but there are probably error bars on that.”
Coherent’s activities include using indium phosphide manufacturing for external laser sources for co-package optics. “And we are working on silicon photonics,” she says.
Coherent is also working on co-packaging VCSELs with high-performance chips. “Not all applications require a 2km reach,” she says.
The coming decade’s opportunities
Eng’s thoughts about the growth opportunities for the coming decade are, not surprisingly, viewed through Coherent’s markets focus.
She highlights four segments: communications, industrial, instrumentation, and electronics.
Fibre-optics communications will continue to grow with bandwidth. The opportunities for innovation include datacom and coherent optics.
She also notes growing interest in free-space optics and satellite communications.
“I see money being spent on that and maybe that is a place where someone like ourselves, with a lot of optics as well as bigger lasers, can play a role,” says Eng.
Precision manufacturing uses lasers in the industrial segment. Eng cites cutting, welding and marking as examples.
“We have elements used for battery manufacturing which is increasing due to electric cars,” she says.
Excimer lasers are also used for OLED and microLED display manufacturing.
“We even have optics in extreme UV steppers [used for advanced process node chip manufacturing],” she says.
For instrumentation, much of the growth is around health life sciences. Coherent makes optics that are used inside PCR testers for COVID-19. It also has engineers working on solid state lasers used for flow cytometry (the sorting of cells). She also cites gene sequencing equipment and medical imaging.
Coherent’s electronics segment refers to the consumer market. Growth here for optics and lasers include AR/VR goggles and the metaverse, wearable health monitoring, and automotive.
For automotive, lasers are used for lidar and in-cabin sensing, such as driver and passenger monitoring.
Silicon carbide is also a growth market, and its uses include the wireless market and power devices for electric vehicles.
“I like the communications market, which we see as growing, but for us, with such a broad portfolio, there are many of these other markets and products that I see as exciting for the remainder of this decade,” says Eng.
OFC announcements and market trends
More compact transceiver designs at 10, 40 and 100 Gigabit, advancements in reconfigurable optical add-drop multiplexer (ROADM) technology and parallel optical engine developments were all in evidence at this year’s OFC/NFOEC show held in Los Angeles in March.
“MSAs are designed by committee, and when you have a committee you throw away innovation and you throw away time-to-market”
Victor Krutul, Avago Technologies
Finisar said that the show was one of the busiest in recent years. “There was an increasing system-vendor presence at OFC, and there was a lot more interest from investor analysts,” says Rafik Ward, vice president of marketing at Finisar.
Ethernet interfaces
Opnext demonstrated an IEEE 100GBASE-ER4 module design at the show, the 100 Gigabit Ethernet (GbE) standard with a 40km reach. Based on the company’s CFP-based 100GBASE-LR4 10km module, the design uses a semiconductor optical amplifier (SOA) on the receive path to achieve the extended reach. The IEEE standard calls for an SOA in front of the photo-detectors for the 100GBASE-ER4 interface.
“We don’t have that [SOA] integrated yet, we are just showing the [design] feasibility,” says Jon Anderson, director of technology programme at Opnext. The extended reach interface will be used to connect IP core routers to transport system when the two platforms reside in separate facilities. Such a 40km requirement for a 100GbE interface is not common but is an important one to meet, says Anderson.
Opnext’s first-generation LR4, currently shipping, is a discrete design comprising four discrete transmitter optical sub-assemblies (TOSAs) and four receiver optical sub-assemblies (ROSAs) and an optical multiplexer and demultiplexer. The company’s next-generation design will integrate the four lasers and the optical multiplexer into a package and will be used in future more compact CFP2 and CFP4 modules.
The CFP2 module is half the size of the CFP module and the CFP4 is a quarter. In terms of maximum power, the CFP module is rated at 32W, the CFP2 12W and the CFP4 5W. “The CFP4 is a little bit wider and longer than the QSFP,” says Anderson. The first CFP2 modules are expected to become available in 2012 and the CFP4 in 2013.
System vendors are interested in the CFP4 as they want to support over one terabit of capacity on a 15-inch faceplate. Up to 16 ports can be supported –1.6Tbps – on a faceplate using the CFP4, and using a “belly-to-belly” configuration two rows of 16 ports will be possible, says Anderson.
Finisar demonstrated a distributed feedback laser (DFB) laser-based CFP module at OFC that implements the 10km 100GBASE-LR4 standard. The adoption of DFB lasers promises significant advantages compared to existing first-generation -LR4 modules that use electro-absorption modulated lasers (EMLs). “If you look at current designs, ours included, not only do they use EMLs which are significantly more expensive, but each is in its own package and has its own thermo-electric cooler,” says Ward.
Finisar’s use of DFBs means an integrated array of the lasers can be packaged and cooled using a single thermo-electric cooler, significantly reducing cost and nearly halving the power to 12W. “Now that the power [of the DFB-based] LR4 is 12W, we can place it within a CFP2 with its 25-28 Gigabit-per-second (Gbps) electrical I/O,” says Ward.
Moving to the faster input/output (I/O) compared to the CFP’s 10Gbps I/O means that that serialiser/ deserialiser (serdes) chipset can be replaced with simpler clock data recovery (CDR) circuitry. “By the time we move to the CFP4, we remove the CDRs completely,” says Ward. “It’s an un-retimed interface.” Finisar’s existing -LR4 design already uses an integrated four-photodetector array.
An early application of the 100GbE -LR4, as with the -ER4, is linking core routers with optical transport systems in operators’ central offices. Many Ethernet switch vendors have chosen to focus their early high-data efforts at 40GbE but Finisar says the move to 100GbE has started.
Finisar argues that the adoption of DFBs will ultimately prove the cost-benefits of a 4-channel 100GbE design which faces competition from the emerging 10x10 multi-source agreement (MSA). “Everything we have heard about the 10x10 [MSA] has been around cost,” says Ward. “The simple view inside Finisar is that by the time the Gen2 100GbE module that we showed at OFC gets to market, this argument [4x25Gig vs. 10x10Gig] will be a moot point.”
“40Gig is definitely still strong and healthy”
Jon Anderson, Opnext
By then the second-generation -LR4 module design will be cost competitive if not even lower cost than the 10x10 MSA. “If you look at optoelectronic components, at the end of the day what really drives cost is yield,” says Ward. “If we can get our yields of 25Gig DFBs down to a level that is similar to 10Gig DFB yields- it doesn’t have to match, just in the ballpark - then we have a solution where the 4x25Gig looks like a 4x10Gig solution and then I believe everyone will agree that 4x25Gig is a less expensive architecture.” Finisar expects the Gen2 CFP -LR4 in production by the first half of 2012.
Opnext demonstrated a 40GBASE- LR4 (40Gbps, up to 10km) standard in a QSFP+ module at OFC. Anderson says it is seeing demand for such a design from data centre operators and from switch and transport vendors.
Avago Technologies announced a 40Gbps QSFP+ module at OFC that implements the 100m IEEE 40GBASE-SR4. “It will interoperate with Avago’s SFP+ modules,” says Victor Krutul, director of marketing for the fibre optics division at Avago Technologies. The QSFP+ can interface to another QSFP+ module or to four 10Gbps SFP+ modules.
Avago also announced a proprietary mini-SFP+ design, 30% smaller than the standard SFP+ but which is electrically compatible. According to Krutul, the design came about following a request from one of its customers: “What it allows is the ability to have 64 ports on the front [panel] rather than 48.”
Did Avago consider making the mini-SFP+ design an MSA? “What we found with MSAs is that they are designed by committee, and when you have a committee you throw away innovation and you throw away time-to-market,” says Krutul.
Krutul was previously a marketing manager for Intel’s LightPeak before joining Avago over half a year ago.
“There was an increasing system-vendor presence at OFC, and there was a lot more interest from investor analysts”
Rafik Ward, Finisar.
Line-side interfaces
Opnext will be providing select customers with its 100Gbps DP-QPSK coherent module for trialling this quarter. The module has a 5-inch by 7-inch footprint and uses a 168-pin connector. “We are working to try and meet the OIF spec [with regard power consumption] which is 80W.” says Anderson. “It is challenging and it may not be met in the first generation [design].”
The company is also moving its 40Gbps 2km very short reach (VSR) transponder to support the IEEE 40GBASE-FR standard within a CFP module, dubbed the “tri-rate” design. “The 40BASE-FR has been approved, with the specification building on the ITU’s 40Gig VSR,” says Anderson. “It continues to support the [OC-768] SONET/SDH rate, it will support the new OTN ODU3 40Gbps and the intermediate 40 Gigabit Ethernet.”
Opnext and Finisar are both watching with interest the emerging 100Gbps direct detection market, an alternative to 100 Gigabit coherent aimed shorter reach metro applications.
“We certainly are watching this segment and do have an interest, but we don’t have any product plans to share at this point,” says Anderson.
“The [100Gbps] direct-detection market is very interesting,” says Ward. Coherent is not going to be the only way people will deploy 100Gbps light paths. “There will be a market for shorter reach, lower performance 100 Gigabit DWDM that will be used primarily in datacentre-to-datacentre,” he says. Tier 2 and tier 3 carriers will also be interested in the technology for use in shorter metro reaches. “There is definitely a market for that,” says Ward.
Opnext also announced its small form-factor – 3.5-inch by 4.5-inch - 40Gbps DPSK module. “With a smaller form factor, the next generation could move to a CFP type pluggable,” says Anderson. “But that is if our customers are interested in migrating to a pluggable design for DPSK and DQPSK.”
Are there signs that the advent of 100 Gigabit is affecting 40Gbps uptake? “We definitely not seeing that,” says Anderson. “We are continuing to see good solid demand for both 40G line side – DPSK and DQPSK – and a lot of pull to being this tri-rate VSR.”
Such demand is not just from China but also North Ametican carriers. “40 Gig is definitely still strong and healthy,” says Anderson “But there are some operators that are waiting to see how 100G does and approved in for major build-outs.”
At 10Gbps, Opnext also had on show a tunable TOSA for use in an XFP module, while Finisar announced an 80km, 10Gbps SFP+ module. “SFP+ has become a very successful form factor at 10Gbps,” says Ward. “All the market data I see show SFP+ leads in overall volumes deployed by a significant margin.” Its success has been achieved despite being a form factor was not designed to achieve all the 10Gbps reaches required initially. This is some achievement, says Ward, since the XFP+ form factor used for 80km has a power rating of 3.5W while the 80km SFP+ has to work within a less than 2W upper limit.
Parallel Optics
Avago detailed its main parallel optic designs: the CXP module and its two optical engine designs.
The company claims it seeing much interested from high-performance computing vendors such as IBM and Fujitsu for its CXP 120 Gigabit (12x10Gbps) parallel transceiver module. Avago is sampling the module and it will start shipping in the summer.
The company also announced the status of its embedded parallel optics devices (PODs). Such parallel optic designs offer several advantages, says Krutul. Embedding the optics on the motherboard offers greater flexibility in cooling since the traditional optics is normally at the edge of the card, furthest away from the fans. Such optics also simplify high-speed signal routing on the printed circuit board since fibre is used.
Avago offers two designs – the 8x8mm MicroPod and the 22x18mm MiniPod. The 12x10Gbps MicroPods are being used in IBM’s Blue Gene computer and Avago says it is already shipping tens of thousands of the devices a month. “The [MicroPod’s] signal pins have a very tight pitch and some of our customers find that difficult to do,” says Krutul. The MiniPod design tackles this by using the MicroPod optical engine but a more relaxed pitch. At OFC, Avago said that the MiniPod is now sampling.
Gridless ROADMs
Finisar demonstrated what it claims is the first gridless wavelength-selective switch (WSS) module at the show. A gridless ROADM supports variable channel widths beyond the fixed International Telecommunication Union's (ITU) defined spacings. Such a capability enables ROADMs to support variable channel spacings that may be required for transmission rates beyond 100Gbps: 400Gbps, 1Tbps and beyond.
“We have an increasing amount of customer interest in this [FlexGrid], and from what we can tell, there is also an increasing amount of carrier interest as well,” says Ward, adding that the company is already shipping FlexGrid WSSs to customers.
Finisar is a contributing to the ongoing ITU work to define what the grid spacings and the central channels should be for future ROADM deployments. Finisar demonstrated its FlexGrid design implementing integer increments of 12.5GHz spacing. “We could probably go down to 1GHz or even lower than that,” says Ward. “But the network management system required to manage such [fine] granularity would become incredibly complicated.” What is required for gridless is a balance between making good use of the fibre’s spectrum while ensuring the system in manageable, says Ward.