Polarized laser light speeds up data center networks

binary data flow

Read an article the other day, Polarizing the data center from IEEE Spectrum, on new optical technology that has the potential to boost data center networking speeds by ~7x beyond what it is today. The research was released in a Nature article, Ultrafast spin lasers (paywall) but a previous version of the paper was released on PLOS (Ultrafast spin lasers) was freely available

It’s still in lab demonstration at this point, but if it does make into the data center, it has the potential to remove local networking as a bottleneck for application workloads, at least for the foreseeable future.

The new technology is based on polarizing (right or left circular) laser light and using plolarization to encode ones and zeros. Today’s optical transceivers seem to use on-off or brightness level to encode data signals, which requires a lot of power (and by definition cooling) to work. On the other hand, polarizing laser light takes ~7% of the power (and cooling), then the old style of on and off laser light. 

How it works

Not sure I understand all the physics but it appears that if you are able to control the carrier spin within a semiconductor, Vertical-Cavity Surface-Emitting Laser (VCSEL), it transmutes carrier spin into photon polarization, and by doing so, emits polarized laser light. And with appropriate sensors, this laser light polarization can be detected and decoded. 

In addition, due to some physical constraints, modulating (encoding) laser intensity will never be faster than modulating (encoding) carrier spin. This has something to do with cycling the laser on and off vs, the polarization process. As such, one should be able to can transmit more information by polarized laser light than by intensified laser light.

Moreover, polarization can be done at room temperature. Apparently, VCSELs operating today typically hit 70C in normal high speed operations, vs. ~21C for VCSELs using polarization.

Lab results

In the lab they are using (I believe) mechanical bending in combination with a pulsed laser to create the spin carriers in the VCSEL’s that polarize the laser light. This is just used for demonstrating purposes. Unclear whether this approach will be useable in a data center application of the technology.

In their lab experiments they were able to demonstrate VCSEL polarization cycles (how quickly they could change polarization) in the 5 ps (pico-second, trillionths of a second) range. This resulted in transmitting something on the order of 214Ghz of polarized light cycles. Somewhere in the PLoS article they mentioned transmitting a random bit string using the technology and not just cycling through 1s and 0s over and over again.

The researchers believe that by moving from mechanical bending, to the use of a photonic crystal or strained quantum well-based VCSELs will allow them to move from signaling at 214Ghz to 1Thz, or ~28X what can be done with laser intensity signaling today. 

I don’t know whether the technology will get out of the lab anytime soon but 1Thz  (~1Tbps) seems something most IT organizations would want, especially if the price is right is similar to today’s technology.

The research mentioned this would be more suitable for data center networking rather than long range data transfers. Not sure why but it could be because 1) it’s still relatively experimental and 2) they have yet to determine distance degradation parameters.

Of course normal (on-off) signaling technology using VCSELs is not standing still. There’s always a potential for moving beyond any current physical constraints to boost some technologies capabilities. Just witness the superparamagnetic barrier in magnetic disk over the years. That physical barrier has moved multiple times during my career.

However, a nearly order of magnitude of speed and more than an order of magnitude of power/cooling improvements are hard to come by with mature technology. I see a polarized optical fiber networking in data centers of the future.

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Comments?

Photo Credit(s):

IT in space

Read an article last week about all the startup activity that’s taking place in space systems and infrastructure (see: As rocket companies proliferate … new tech emerges leading to a new space race). This is a consequence of cheap(er) launch systems from SpaceX, Blue Origin, Rocket Lab and others.

SpaceBelt, storage in space

One startup that caught my eye was SpaceBelt from Cloud Constellation Corporation, that’s planning to put PB (4X library of congress) of data storage in a constellation of LEO satellites.

The LEO storage pool will be populated by multiple nodes (satellites) with a set of geo-synchronous access points to the LEO storage pool. Customers use ground based secure terminals to talk with geosynchronous access satellites which communicate to the LEO storage nodes to access data.

Their main selling points appear to be data security and availability. The only way to access the data is through secured satellite downlinks/uplinks and then you only get to the geo-synchronous satellites. From there, those satellites access the LEO storage cloud directly. Customers can’t access the storage cloud without going through the geo-synchronous layer first and the secured terminals.

The problem with terrestrial data is that it is prone to security threats as well as natural disasters which take out a data center or a region. But with all your data residing in a space cloud, such concerns shouldn’t be a problem. (However, gaining access to your ground stations is a whole different story.

AWS and Lockheed-Martin supply new ground station service

The other company of interest is not a startup but a link up between Amazon and Lockheed Martin (see: Amazon-Lockheed Martin …) that supplies a new cloud based, satellite ground station as a service offering. The new service will use Lockheed Martin ground stations.

Currently, the service is limited to S-Band and attennas located in Denver, but plans are to expand to X-Band and locations throughout the world. The plan is to have ground stations located close to AWS data centers, so data center customers can have high speed, access to satellite data.

There are other startups in the ground station as a service space, but none with the resources of Amazon-Lockheed. All of this competition is just getting off the ground, but a few have been leasing idle ground station resources to customers. The AWS service already has a few big customers, like DigitalGlobe.

One thing we have learned, is that the appeal of cloud services is as much about the ecosystem that surrounds it, as the service offering itself. So having satellite ground stations as a service is good, but having these services, tied directly into other public cloud computing infrastructure, is much much better. Google, Microsoft, IBM are you listening?

Data centers in space

Why stop at storage? Wouldn’t it be better to support both storage and computation in space. That way access latencies wouldn’t be a concern. When terrestrial disasters occur, it’s not just data at risk. Ditto, for security threats.

Having whole data centers, would represent a whole new stratum of cloud computing. Also, now IT could implement space native applications.

If Microsoft can run a data center under the oceans, I see no reason they couldn’t do so in orbit. Especially when human flight returns to NASA/SpaceX. Just imagine admins and service techs as astronauts.

And yet, security and availability aren’t the only threats one has to deal with. What happens to the space cloud when war breaks out and satellite killers are set loose.

Yes, space infrastructure is not subject to terrestrial disasters or internet based security risks, but there are other problems besides those and war that exist such as solar storms and space debris clouds. .

In the end, it’s important to have multiple, non-overlapping risk profiles for your IT infrastructure. That is each IT deployment, may be subject to one set of risks but those sets are disjoint with another IT deployment option. IT in space, that is subject to solar storms, space debris, and satellite killers is a nice complement to terrestrial cloud data centers, subject to natural disasters, internet security risks, and other earth-based, man made disasters.

On the other hand, a large, solar storm like the 1859 one, could knock every data system on the world or in orbit, out. As for under the sea, it probably depends on how deep it was submerged!!

Photo Credit(s): Screen shots from SpaceBelt youtube video (c) SpaceBelt

Screens shot from AWS Ground Station as a Service sign up page (c) Amazon-Lockheed

Screen shots from Microsoft’s Under the sea news feature (c) Microsoft

Photonic or Optical FPGAs on the horizon

Read an article this past week (Toward an optical FPGA – programable silicon photonics circuits) on a new technology that could underpin optical  FPGAs. The technology is based on implantable wave guides and uses silicon on insulator technology which is compatible with current chip fabrication.

How does the Optical FPGA work

Their Optical FPGA is based on an eraseable direct coupler (DC) built using GE (Germanium) ion implantation. A DC is used when two optical waveguides are placed close enough together such that optical energy (photons) on one wave guide is switched over to the other, nearby wave guide.

As can be seen in the figure, the red (eraseable, implantable) and blue (conventional) wave guides are fabricated on the FPGA. The red wave guide performs the function of DC between the two conventional wave guides. The diagram shows both a single stage and a dual stage DC.

By using imlantable (eraseable) DCs, one can change the path of a photonic circuit by just erasing the implantable wave guide(s).

The GE ion implantable wave guides are erased by passing a laser over it and thus annealing (melting) it.

Once erased, the implantable wave guide DC no longer works. The chart on the left of the figure above shows how long the implantable wave guide needs to be to work. As shown above once erased to be shorter than 4-5µm, it no longer acts as a DC.

It’s not clear how one directs the laser to the proper place on the Optical FPGA to anneal the implantable wave guide but that’s a question of servos and mirrors.

Previous attempts at optical FPGAs, required applying continuing voltage to maintain the switched photonics circuits. Once voltage was withdrawn the photonics reverted back to original configuration.

But once an implantable wave guide is erased (annealed) in their approach, the changes to the Optical FPGA are permanent.

FPGAs today

Electronic FPGAs have never gone out of favor with customers doing hardware innovation. By supplying Optical FPGAs, the techniques in the paper would allow for much more photonics innovation as well.

Optics are primarily used in communications and storage (CD-DVDs) today. But quantum computing could potentially use photonics and there’s been talk of a 100% optical computer for a long time. As more and more photonics circuitry comes online, the need for an optical FPGA grows. The fact that it’s able to be grown on today’s fab lines makes it even more appealing.

But an FPGA is more than just directional control over (electronic or photonic) energy. One needs to have other circuitry in place on the FPGA for it to do work.

For example, if this were an electronic FPGA, gates, adders, muxes, etc. would all be somewhere on the FPGA

However, once having placed additional optical componentry on the FPGA, photonic directional control would be the glue that makes the Optical FPGA programmable.

Comments?

Photo Credit(s): All photos from Toward an optical FPGA – programable silicon photonics circuits paper

 

A “few exabytes-a-day” from SKA

A number of radio telescopes, positioned close together pointed at a cloudy sky
VLA by C. G. P. Grey (cc) (from Flickr)

ArsTechnica reported today on the proposed Square Kilometer Array (SKA) radio telescope and it’s data requirements. IBM is in collaboration with the Netherlands Institute for Radio Astronomy (ASTRON) to help develop the SKA called the DOME project.

When completed in ~2024, the SKA will generate over an exabyte a day (10**18) of raw data.  I reported in a previous post how the world was generating an exabyte-a-day, but that was way back in 2009.

What is the SKA?

The new SKA telescope will be a configuration of “millions of radio telescopes” which when combined together will create a telescope with an aperture of one square kilometer, which is no small feet.  They hope that the telescope will be able to shed some light on galaxy evolution, cosmology and dark energy.  But it will go beyond that to investigating “strong-field tests of gravity“, “origins and evolution of cosmic magnetism” and search for life on other planets.

But the interesting part from a storage perspective is that the SKA will be generating a “few exabytes a day” of radio telescopic data for every full day of operation.   Apparently the new radio telescopes will make use of a new, more sensitive detector able to generate data of up to 10GB/second.

How much data, really?

The team projects final storage needs at between 300 to 1500 PB per year. This compares to the LHC at CERN which consumes ~15PB of storage per year.

It would seem that the immediate data download would be the few exabytes and then it would be post- or inline-processed into something more mangeable and store-able.  Unless they have some hellaciously fast processing, I am hard pressed to believe this could all happen inline.  But then they would need at least another “few exabytes” of storage to buffer the data feed before processing.

I guess that’s why it’s still a research project.  Presumably, this also says that the telescope won’t be in full operation every day of the year, at least at first.

The IBM-ASTRON DOME collaboration project

The joint research project was named for the structure that covers a major telescope and for a famous Swiss mountain.  Focus areas for the IBM-ASTRON DOME project include:

  • Advanced high performance computing utilizing 3D chip stacks for better energy efficiency
  • Optical interconnects with nanophotonics for high-speed data transfer
  • Storage for both high access performance access and for dense/energy efficient data storage.

In this last focus area, IBM is considering the use of phase change memories (PCM) for high access performance and new generation tape for dense/efficient storage.  We have discussed PCM before in a previous post as an alternative to NAND based storage today (see Graphene Flash Memory).  But IBM has also been investigating MRAM based race track memory as a potential future storage technology.  I would guess the advantage of PCM over MRAM might be access speed.

As for tape, IBM has already demonstrated in their labs technologies for a 35TB tape. However storing 1500 PB would take over 40K tapes per year so they may need another even higher capacities to support SKA tape data needs.

Of course new optical interconnects will be needed to move this much data around from telescope to data center and beyond.  It’s likely that the nanophotonics will play some part as an all optical network for transceivers, amplifiers, and other networking switching gear.

The 3D chip stacks have the advantage of decreasing chip IO and more dense packing of components will make efficient use of board space.  But how these help with energy efficiency is another question.  The team projects very high energy and cooling requirements for their exascale high performance computing complex.

If this is anything like CERN, datasets gathered onsite are initially processed then replicated for finer processing elsewhere (see 15PB a year created by CERN post.  But moving PBs around like SKA will require is way beyond today’s Internet infrastructure.

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Big science like this gives a whole new meaning to BIGData. Glad I am in the storage business.  Now just what exactly is nanophotonics, mems based phote-electronics?