News & Analysis
DesignCon: Cisco packs silicon photonics on 3-D ICs
Rick Merritt
1/28/2013 9:10 PM EST
SANTA CLARA, Calif. – Cisco Systems is prototyping silicon photonics using 2.5-D silicon interposers, according to a senior engineering executive in a keynote at DesignCon here. The communications giant is one of a handful of companies trying to harness the technology to drive down the costs of next-generation networks.
“The convergence of optical and semiconductor ecosystems will have a huge impact for networking at 40 and 100 Gbits/second and beyond,” said Bill Swift, who leads Cisco’s transceiver and module group.
Swift showed a rough diagram (below) of a 2.5-D chip that included a laser light source, optical lenses and isolators along with what appeared to be a CMOS modulator and multiplexor. “This is stuff we are working on now, and I find it very exciting,” he said.
He declined to comment on reports the company will ship this year samples of 100G silicon optical modules based on the LX4 standard. Cisco bought silicon-photonics startup Lightwire (Allentown, Penns.) in February 2010 for $271 million.
Click on image to enlarge.
Convergence of CMOS and optics will drive next-gen nets, Swift said.
Next: Cisco on SDN and power
“The convergence of optical and semiconductor ecosystems will have a huge impact for networking at 40 and 100 Gbits/second and beyond,” said Bill Swift, who leads Cisco’s transceiver and module group.
Swift showed a rough diagram (below) of a 2.5-D chip that included a laser light source, optical lenses and isolators along with what appeared to be a CMOS modulator and multiplexor. “This is stuff we are working on now, and I find it very exciting,” he said.
He declined to comment on reports the company will ship this year samples of 100G silicon optical modules based on the LX4 standard. Cisco bought silicon-photonics startup Lightwire (Allentown, Penns.) in February 2010 for $271 million.
Click on image to enlarge.
Lightwire’s first generation product used wavelength division multiplexing to put four 25G channels over a single fibre, sources said. Along with startup Luxtera, it is pushing for use of advanced coding techniques such as eight-level pulse amplitude modulation to get to 50G serial links.
Among Cisco’s competitors, Intel announced earlier this month it is shipping engineering samples of 100G silicon photonics modules. Startups Luxtera and Kotura plan to ship 100G silicon photonics modules in 2014. Intel is using CMOS for all the major components including the laser light source; Luxtera and Kotura use external lasers.
Swift said 3-D ICs will reduce chip power and accelerate integration. The 2.5-D version using silicon interposers is the latest version of a technology that’s been around for years, he said.
"In the 1990’s, I used a pcb interposer because I got my BGA wrong, now we can use it to put multiple die on silicon,” he quipped.
Convergence of CMOS and optics will drive next-gen nets, Swift said.
Next: Cisco on SDN and power
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resistion
1/28/2013 11:13 PM EST
The lasers are still non-Si; they are probably InP or the like at the very least.
So it looks like interposers will replace motherboards? That's pretty disruptive. Expect some resistance.
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a.sun
1/29/2013 2:24 PM EST
The laser is made of InP by bonding a 2-4" InP wafer onto a 6-8" Si wafer (the size mismatch is an issue!) and thinning down the InP wafer to a few micrometers for later planar processing steps. As far as I know, Intel's solution uses separate CMOS TIA & laser driver chips in addition to a Si photonics chip (including functions of photo detection, modulation and optical routing) in comparison to a more integrated solution from Luxtera.
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a.sun
1/29/2013 2:25 PM EST
The laser is made of InP by bonding a 2-4" InP wafer onto a 6-8" Si wafer (the size mismatch is an issue!) and thinning down the InP wafer to a few micrometers for later planar processing steps. As far as I know, Intel's solution uses separate CMOS TIA & laser driver chips in addition to a Si photonics chip (including functions of photo detection, modulation and optical routing) in comparison to a more integrated solution from Luxtera.
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resistion
1/31/2013 2:57 AM EST
Thanks for the information. Is this available somewhere? Thanks again.
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a.sun
2/2/2013 11:40 AM EST
First reported bonded laser on SOI was a joint project that Intel and UCSB worked on a couple of years ago. Some collaborating European groups independently developed the same thing but with a different III-V active material nearly the same time. I remember Intel&UCSB published their results in a fast review cycle journal to beat their opponents. Bonded lasers in principal suffer from lower performance by using SOI waveguide as external lasing resonator, let alone the complexity in processing (but which can be conquered) and size mismatch between InP wafers and Si wafers. But I heard some improvement recently. Intel didn't push very hard in fully monolithic integration of photonic components and CMOS circuits for TIA and laser driver. Luxtera spent a ton of money and nearly a decade on incorporating photonic components in a legacy 130nm line of Freescale which is only good for upto 10G. 25G TIA&driver needs at least 65nm which need too much design rule and library changes to have photonics in. This is much harder than mixing digital and analog circuits which still meets troubles from time to time. It may worth doing, but you definitely need someone with deep pocket.
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rick.merritt
1/29/2013 1:07 AM EST
But not as much resistance as an off-chip design ;-)
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Turkman
1/30/2013 10:53 AM EST
I knew that comment would induce someone to make a joke.
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resistion
1/31/2013 2:58 AM EST
It's a good one ;)
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HS_SemiPro
1/29/2013 1:37 AM EST
That's the beauty of 2.5D and full 3D designs, greatly reduce system cost improve signal latency
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a.sun
1/29/2013 2:29 PM EST
Unfortunately, the integration of these different optical components like lens and laser can be done in a identical thus cost effective way like 2.5D electronics. Different bonding/soldering techniques and tolerances exist for different components, i.e. laser requires sub-micro placement accuracy. So up to now, it's merely a reduced scale of optical packaging on Si instead of on submount.
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a.sun
1/29/2013 2:34 PM EST
I meant "can't be done in ...". btw, is there a way to edit one's own posts? It's not uncommon to make typos from time to time. It should be a basic function.
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docdivakar
1/29/2013 2:27 PM EST
Rick, the title is somewhat misleading... I think Mr. Swift was referring to planar Si optical waveguides. Using these in 3D optical interconnect, from today's on-chip optical interconnect technology, is still far away from fruition from a practical view point. Last year's DesignCon I think there was a talk by HP Lab's chief about this but it has remained largely as a research project. There is no doubt that this is the next growth area for transistors.
Underwhelming SDN/OpenFlow by Cisco is not surprising because it is a disruptor to their legacy products!
For those interested, here is the link to presentations from Silicon Valley Comsoc on SDN's by Guru Parulkar & Dan Pitt of Open Networking Research Center:
http://ewh.ieee.org/r6/scv/comsoc/ComSoc_2012_Presentations.php
MP Divakar
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rick.merritt
1/29/2013 4:01 PM EST
@Divakar: Thanks for the SDN link. Yes, a potentially huge disruption for Cisco!
Swift was so vague it's hard to tell exactly what Cisco is planning with 2.5-D and optics but your guess is more technically informed than mine!
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iniewski
1/29/2013 5:04 PM EST
Sounds like pretty disruptive technology if they can pull it off in mass production...would anyone be interested in discussing it at Grenoble emerging technologies symposium, details at www.cmosetr.com? planning a panel discussion on this topic, kris.iniewski@gmail.com
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rick.merritt
1/29/2013 5:40 PM EST
@Kris: I sent an email to Luxtera, Kotura, Intel, Cisco contacts on this
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athose
3/20/2013 12:14 AM EDT
here is some thing that may interest people as possibly some thing that may be ahead of this.
Opel Laser Uses POET Optoelectronic Platform
The III-V gallium arsenide (GaAs) based monolithic platform could change the roadmap for smartphones, tablet and wearable computers
Opel's U.S. affiliate, Odis Inc. has produced an integrated laser device in its Planar Optoelectronic Technology (POET) process.
The laser enables high-performance devices fusing optical and electronic devices together on a single chip.
After years of development, the fabrication of the first Vertical Cavity Laser, (VCL) utilising Odis'patented POET GaAs III-V technology is a significant success.
Incremental progress over the years has led to what many consider to be the next phase of semiconductor development which is to surpass the capabilities of complementary metal oxide semiconductor (CMOS) technology for the next generation of high speed low power applications.
The POET advantage is the merging of optical devices into the growth and fabrication that supports complementary HFET analogue and digital functions.
The intimate connections between diverse device types enables novel gate designs which dramatically reduce the power consumed in the opto-electronic (OE) and electro-optic conversions. The VCL has the small footprint required for dense circuit layout and enables vertical connections from anywhere in the circuit plane to fibre or to other stacked chips.
Moving forward, development will lower the threshold current, increase the output power and optimise the in-plane version of the VCL. Also, the complementary transistor circuit capability will be enhanced by reducing the feature size to the 100 nm scale incorporating Odis' new self-aligned contact technology.
With transistor cutoff frequencies around 38 GHz for a 0.7µm gate, the scaling is expected to produce 260 GHz transistors with big improvements in circuit speed.
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