ECOC '15 Reflections: Part 2
Martin Zirngibl, head of network enabling components and technologies at Bell Labs.
Silicon Photonics is seeming to gain traction, but traditional component suppliers are still betting on indium phosphide.
There are many new start-ups in silicon photonics, most seem to be going after the 100 gigabit QSFP28 market. However, silicon photonics still needs a ubiquitous high-volume application for the foundry model to be sustainable.
There is a battle between 4x25 Gig CWDM and 100 Gig PAM-4 56 gigabaud, with most people believing that 400 Gig PAM-4 or discrete multi-tone with 100 Gig per lambda will win.
Will coherent make it into black and white applications - up to 80 km - or is there a role for a low-cost wavelength-division multiplexing (WDM) system with direct detection?
One highlight at ECOC was the 3D integrated 100 Gig silicon photonics by Kaiam.
In coherent, the analogue coherent optics (ACO) model seems to be winning over the digital coherent one, and people are now talking about 400 Gig single carrier for metro and data centre interconnect applications.
As for what I’ll track in the coming year: will coherent make it into black and white applications - up to 80 km - or is there a role for a low-cost wavelength-division multiplexing (WDM) system with direct detection?
Yukiharu Fuse, director, marketing department at Fujitsu Optical Components
There were no real surprises as such at ECOC this year. The products and demonstrations on show were within expectations but perhaps were more realistic than last year’s show.
Most of the optical component suppliers demonstrated support to meet the increasing demand of data centres for optical interfaces.
The CFP2 Analogue Coherent Optics (CFP2-ACO) form factor’s ability to support multiple modulation formats configurable by the user makes it a popular choice for data centre interconnect applications. In particular, by supporting 16-QAM, the CFP2-ACO can double the link capacity using the same optics.
Lithium niobate and indium-phosphide modulators will continue to be needed for coherent optical transmission for years to come
Recent developments in indium phosphide designs has helped realise the compact packaging needed to fit within the CFP2 form factor.
I saw the level of integration and optical engine configurations within the CFP2-ACO differ from vendor to vendor. I’m interested to see which approach ends up being the most economical once volume production starts.
Oclaro introduced a high-bandwidth lithium niobate modulator for single wavelength 400 gigabit optical transmission. Lithium niobate continues to play an important role in enabling future higher baud rate applications with its excellent bandwidth performance. My belief is that both lithium niobate and indium-phosphide modulators will continue to be needed for coherent optical transmission for years to come.
Chris Cole, senior director, transceiver engineering at Finisar
ECOC technical sessions and exhibition used to be dominated by telecom and long haul transport technology. There is a shift to a much greater percentage focused on datacom and data centre technology.
What I learned at the show is that cost pressures are increasing
There were no major surprises at the show. It was interesting to see about half of the exhibition floor occupied by Chinese optics suppliers funded by several Chinese government entities like municipalities jump-starting industrial development.
What I learned at the show is that cost pressures are increasing.
New datacom optics technologies including optical packaging, thermal management, indium phosphide and silicon integration are all on the agenda to track in the coming year.
Hybrid integration specialist Kaiam acquires Gemfire
Kaiam Corp. has secured US $16M in C-round funding and completed the acquisition of Gemfire.
"We have a micro-machine technology that allows us to use standard pick-and-place electronic assembly tools, and with our micro-machine, we achieve sub-micron alignment tolerances suitable for single-mode applications"
Byron Trop, Kaiam
With the acquisition, Kaiam gains planar lightwave circuit (PLC) technology and Gemfire's 8-inch wafer fab in Scotland. This is important for the start-up given there are few remaining independent suppliers of PLC technology.
Working with Oplink Communications, Kaiam has also demonstrated recently a 100 Gigabit 10x10 MSA 40km CFP module.
Hybrid integration technology
Kaiam has developed hybrid integration technology that achieves sub-micron alignment yet only requires standard electronic assembly tools.
"With single-mode optics, it is very, very difficult to couple light between components," says Byron Trop, vice president of marketing and sales at Kaiam. "Most of the cost in our industry is associated with aligning components, testing them and making sure everything works."
The company has developed a micro-machine-operated lens that is used to couple optical components. The position of the lens is adjustable such that standard 'pick-and-place' manufacturing equipment with a placement accuracy of 20 microns can be used. "If you set everything [optical components] up in a transceiver with a 20-micron accuracy, nothing would work," says Trop.
Components are added to a silicon breadboard and the micro-machine enables the lens to be moved in three dimensions to achieve sub-micron alignment. "We have the ability to use coarse tools to manipulate the machine, and at the far end of that machine we have a lens that is positioned to sub-micron levels," says Trop. Photo-diodes on a PLC provide the feedback during the active alignment.
Another advantage of the technique is that any movement when soldering the micro-machine in position has little impact on the lens alignment. "Any movement that happens following soldering is dampened over the distance to the lens," says Trop. "Therefore, movement during the soldering process has negligible impact on the lens position."
Kaiam buys its lasers and photo-detector components, while a fab make its micro-machine. Hybrid integration is used to combine the components for its transmitter optical sub-assembly (TOSA) and receiver optical sub-assembly (ROSA) designs, and these are made by contract manufacturers. Kaiam has a strategic partnership with contract manufacturer, Sanmina-SCI.
The company believes that by simplifying alignment, module and systems companies have greater freedom in the channel count designs they can adopt. "Hybrid integration, this micro-alignment of optical components, is no longer a big deal," says Trop. "You can start thinking differently."
"We will also do more custom optical modules where somebody is trying to solve a particular problem; maybe they want 16 or 20 lanes of traffic"
For 100 Gigabit modules, companies have adopted 10x10 Gigabit-per-second (Gbps) and 4x28Gbps designs. The QSFP28 module, for example, has enabled vendors to revert back to four channels because of the difficulties in assembly.
"Our message is not more lanes is better," says Trop. "Rather, what is the application and don't consider yourself limited because the alignment of sub-components is a challenge."
With the Gemfire acquisition, Kaiam has its own PLC technology for multiplexing and de-multiplexing multiple 10Gbps and, in future, 25Gbps lanes. "Our belief is that PLC is the best way to go and allows you to expand into larger lane counts," says Trop.
Gemfire also owned intellectual property in the areas of polymer waveguides and semiconductor optical amplifiers.
Products and roadmap
Kaiam sells 40Gbps QSFP TOSAs and ROSAs for 2km, 10km and 40km reaches. The company is now selling its 40km 10x10 MSA TOSA and ROSA demonstrated at the recent OFC/NFOEC show. Trop says that the 40km 10x10 CFP MSA module is of great interest to Internet exchange operators that want low cost, point-to-point links.
"Low cost, highly efficient optical interconnect is going to be important and it is not all at 40km reaches," says Trop. "Much of it is much shorter distances and we believe we have a technology that will enable that."
The company is looking to apply its technology to next-generation optical modules such as the CFP2, CFP4 and QSFP28. "We will also do more custom optical modules where somebody is trying to solve a particular problem; maybe they want 16 or 20 lanes of traffic," says Trop.
