Slashdot Mirror
Engineers Report Breakthrough in Laser Beam Tech
petralynn writes to tell us the New York Times is reporting that Stanford engineers have discovered a method to modulate a beam of laser light up to 100 billion times a second. The new technology apparently uses materials that are already in wide use throughout the semiconductor industry. From the article: "The vision here is that, with the much stronger physics, we can imagine large numbers - hundreds or even thousands - of optical connections off of chips," said David A.B. Miller, director of the Solid State and Photonics Laboratory at Stanford University. "Those large numbers could get rid of the bottlenecks of wiring, bottlenecks that are quite evident today and are one of the reasons the clock speeds on your desktop computer have not really been going up much in recent years."
The NYT story is pretty light on the technical details....a more detail-oriented write-up can be found here... and you don't have to register to read it.
____
~ |rip/\/\aster /\/\onkey
This work was funded by Intel and DARPA with some assistance from an HP researcher and uses something called the Quantum-Confined Stark Effect with primary application in optical networking gear ... but hey, maybe
we'll see a 100 GHz PC in the not-too-distant future.
The halloween webcam is up ... but X10 technology isn't capable of 100 Billion times/second updates ... ;-)
Hulk SMASH Celiac Disease
Is that the one across the bay from Berkly?
"I'd rather be a lightning rod than a seismometer." -Ken Kesey
But will it pop a huge jiffy-pop container in my professor's house by shooting it from a plane?
...was chips with frickin' laser beams!
I hate all the people that post that without knowing shit about it. As this applies to optics and not semiconductors, it really doesn't have anything to do with moore's law.
From the article:
Several industry executives said the advance was significant because it meant that optical data networks were now on the same Moore's Law curve of increasing performance and falling cost that has driven the computer industry for the past four decades.
Doh! Don't you hate it when you get all high and mighty posting about people who don't know what they're talking about and then find out that you don't know what you're talking about?
That's awesome. I can't wait for Hraverd and Yalle to catch up.
trustedworlds.net - gaming, security, and the gunk that lives in between
So can they attach them to sharks' heads yet?
http://nerdfortress.com/
This sounds silly to me since desktop power (say a $500 system - discounting monitor and keyboard) is increasing exponentially, doubling every two years compared to the price. The machine I built this spring was twice as powerful than a system I built in 2003 for the same money, but 8 times as powerful as a machine I built just 6 years ago and is about 128 times as powerful as the machine I had when I went to college in 92. And I am only considering pure clock speed, not increases in the efficiency of chips, growth of RAM and disk for the price, etc. While Moore's law concerning silicon chips will start faltering as we approach 2020, I have been nothing but impressed with how desktop performance continues to improve.
These new laser improvements, and things like molecular computing, will help us continue on after the 2020 mark with our current exponential growth.
Sorry to go off, I just got done reading The Sigularity Is Near
Great ideas often receive violent opposition from mediocre minds. - Albert Einstein
If I remember correctly, QCSE uses excitons to absorb light.
What is the wavelength of these excitons in SiGe? If it's significantly different than 1.3 microns - 1.5 microns, then this is a short-haul play -- like inside a box. In any case, 100 Gb/s is generally fragile stuff anyway over long distance, so it's highly unlikely that this is part of some global supercomputer, as the article suggests.
That's OK, though. This might be great stuff for optical interconnection buses.
BTW, D.A.B Miller is a big name in the field, so this is likely a big deal.
You need to differentiate the drift speed of the particular electrons (this can be quite slow, esp. in AC) and the speed of propagation of energy, which if I recall is damn fast (near C, but not there...granted, 1/10 of C is still astoundingly fast, so my poor memory of freshman physics may not contradict you, though I think your guess is off)...the real advantage is that the switching speed is far beyond what we can do with current metal/electron based circuits (rtfa) . Additionally, this is big because using electrons generates more heat and is subject to induction/capacitence effects that light isn't. So those would be the main advantages, as I understand it... but I only play a physicist on /. so feel free to correct me, cruel world.
The speed of the electrons is on the order of cm/s, and is related to the current density.
.. . . .
The electromotive force, or voltage, travels at about the speed of light.
Picture a hose of water. The water (electrons) takes a long time to get from one end to the other... but the effect of putting water in one end is immediately seen at the other end (within reason).
With AC, electrons never really gain ground in a balanced load situation. Back and forth and
Dude.
Your tinfoil hat slipped loose.
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
The modulation. The signal travels at about the same time, but you can turn it on and off much much faster... so the density of bits per unit of time is much higher.
Normal signal: ____----____----____----
0 1 0 1 0 1
New hawtness: _-_-_-_-_-_-_-_-_-_-_-_-
010101010101010101010101
Both took the same amount of time to travel down the pipe. But one conveyed 4x the information.
"Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
Standford engineers have discovered a method to modulate a beam of laser light up to 100 billion times a second.
So, you still have the same "speed" but you have way higher modulation than what is possible through a traditional chip.
So, if you have two highways, both going the same speed, but one is filled with dinky cars and one is filled with transport trucks....in which highway can you have more total cars get through?
So the data gets there in the same length of time, but you have data sending/arriving much more frequently, so total throughput is up.
[I can picture a world without war, without hate. I can picture us attacking that world, because they'd never expect it]
The Silicon Solution
It describes what I believe is the same breakthrough in considerable detail. The Big Deal is that lasers can now be made from standard CMOS silicon fab processes, meaning you can integrate the lasers and optoelectronics directly into the chip without needing radically new chip fab techniques. Really interesting stuff!
If you don't know where you are going, you will wind up somewhere else.
It would also be interesting to know how much heat is generated by the absorbtion of the light. How does this compare to electrical units' heat?
At least then you'll never need to get up to get rid of that monitor tan and you can fix a grilled cheese sammich at the same time!
BRRRRRRRRiiiiilliant!!
Cliff Claven
K.E.G. Party Chairman
Founding Leader of: Koncerned for Egalitarin Governance
The speed of electricity in a wire is not really the issue (it's about half the speed of light, I think. I'm sure someone will correct me). The real issue is signal propagation. When a transistor switches from closed to open or back, the electrical signal travelling through the wire is not a perfect on/off. The voltage ramps up or ramps down as some function of the length of the connection, width of the wire, conductivity, leakage from the transistor, inductance, ... The system needs a bit of time to "settle" into the new high or low state. This is a big limiting factor in the clocking of modern CPUs. For communication off the chip, it's far worse. Now the lines are no longer 90nm (or whatever the chip was made at) in width, and have to go through a far longer distance. That's why today's processors are limited at around 1GHz to the outside world, while internally they can be faster.
Optical interconnects alleviate many of these problems. With a laser, the ramp up time is significantly shorter, there's no capacitance in the system, and it is far less prone to interference. So, on a 100 GHz optical link you can multiplex 100 1GHz pins (essentially running a P4's FSB on two wires instead of something like 180), thereby significantly reducing the pin count. Or you could run the pins 100 times as fast, meaning much less processor waiting on RAM or bus data.
Yeah, that's not true. I don't know how fast an electron moves (I'm assuming not the speed of light, since they have mass, and that quantum physics I know little about probably comes into play), but in a normal conductor they don't move very far before slamming into something. Individual electrons don't move that far or fast on their own, it's the aggregate and resulting field that really moves.
But that's not really the problem. Transmit time is still quite low (I've heard 1ns per 6 in of trace on a board). Latency isn't really the problem. The problem is -- how fast can you change the signal? That's bandwidth. Here electrical conductors suffer because of parasitic capacitance and inductance, skin effects, reflections, induced current from nearby conductors, and a whole host of other signal integrity issues. It gets worse the longer the channel is and the more things you have connected to it. If you're wondering why the MP Pentium 4s have been on a 100MHz QDR front side bus since they were released, this is why. It's also why even point-to-point interconnect like AMDs has only recently broken 1 GHz.
Optics don't really have this issue. Two fiber optic cables next to each other don't interfere with each other. You don't have to overcome the capacitance of the channel to change from one value to the next. You just send photons of one frequency, and then switch to the next. As fast as you can switch is how much bandwidth you can get.
Alright, I'm not really liking this explanation anymore. To just directly answer your question: the advantage is 100 GHz interconnect in a way that could potentially be built into chips.
The enemies of Democracy are
You can build what's called an "aritficial transmission line" in just such a manner. It simulates the effect of a much longer pair of wires for lab purposes.
I am not a crackpot.
The first company to develop a low-cost, high-quality tech for "printing" optical traces will make a mint once these interconnects become common. I'd bet that the ultimate technology will be a sandwich of resins with etched channels and vapor-deposited reflective layers, walls, corners (or high-index resin filling). For most applications, the optical interconnect can be single-layer because the non-interference on crossing beams will let two traces/channels cross each other with interference.
Inventions like this one are a great start. But until they find away to make cheap circuits to route optical connections on a board, this tech won't see widespread adoption.
Two wrongs don't make a right, but three lefts do.
...to come up with a frickin' shark that can keep up wih these new lasers.
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
Quantum computers are great, in theory, but even if we are able to figure out how to build one that actually works they are only capable of solving certain types of problems. Our present understanding of quantum physics tells us that you can't design a quantum computer that can do all the same math problems as a generic Intel/AMD CPU (e.i. run Windows; play Counterstrike; etc.).
That being said, the problems that can be solved by quantum computers tend to be the ones that would take a regular CPU until the end of the universe to perform (break strong encryption, large traveling salesman problems, etc.). At some point, if we can make a quantum computer compact enough, we might end up having quantum co-processors built into out PCs but we'll probably never see the CPU of our PC replaced by a quantum computer.
The tech being discussed in the article would be directly applicable to making generic PCs run faster (though it could also have the potential to improve communication speeds with a hypothetical quantum computer as well). Another tech that will probably be leveraged to make generic systems faster is the replacement of silicon in computer chips with diamond. Since diamond can handle vastly higher temperatures than silicon, without melting, it is theoretically possible to push the clock speed on a diamond based CPU much higher than on today's silicon CPUs.
-GameMaster
Rules of Conduct:
#1 - The DM is always right.
#2 - If the DM is wrong, see rule #1
Now for the fun part - What is the velocity of propagation?
For frequencies were the inductive reactance of the conductor is significantly larger than the resistance of that conductor at that frequency (think skin effect), then the velocity of propagation is c divided by the square root of the effective relative dielectric constant. This is often referred to as an LC transmission line since propagation is dominated by the series inductance and shunt capaitance. LC lines have a propagation velocity independent of frequency (at least to the first order). As an example, coaxial cable with a solid polyethylene dielectric will have a propagation velocity of 0.66c, which would be valid from a few hundred kHz to several GHz.
When the the conductor resistance is greater than the inductive reactance, then the line becomes an RC line where the "propagation velocity" is dependent on frequency (dispersive) and the time for a transition to propagate is proportional to the square of the line length. The effective "propagation velocity" is going to be a lot less than c. Turns out that the interconnects on chips are RC lines - and it is often necessary to insert inverters on a line to speed things up (recall that propagation time varies with the square of the line length) - a good rule of thumb is to space the inverters so the the propagation delay equals the gate delay.
The RC problem is why loading coils were put on phone lines - the inductive reactance of the coils is larger than the resistance and the line becomes an LC. The loading coils are bad news for DSL - and an unloaded line looks like an LC line at the frequencies used by the DSL modems.
A good reference for this is High Speed Digital Design, a Handbook of Black Magic by Johnson and Graham.
It's not all that accurately worded, but it is relevant. The lack of accuracy is likely due to trying to keep that comment short.
In any case, while Moore's Law is specific to transitor based circuitry, the pattern is applicable to other technologies, such as Kryder's Law which covers rigid magnetic media (hard drives). In fact, looking at these cases in general within a field of technology suggests a more abstract pattern. After all, the original component technologies with which Moore worked when he made his observations have been replaced over the years, some of them multiple times, with the the common thread to all of them being that they ultimately deal with transitors.
If optical technologies get pulled in by the same economic factors that drive Moore's and Kryder's Laws, they'll very like fall into a similar pattern: doubling of a particular characteristic over constant intervals.
Of course, all of this also depends on how how close a class of technology is to its fundamental extreme physical limits. For instance, density of transistors is ultimately limited by the size of atoms; the limit there may be somewhere around a "one molecule transitor." In the particular case of the article, the technology is optical modulators and the measure is switching rates. For that, one limit may be the frequency of the transmitted light. The visible spectrum runs from 384-769 THz, with the higher frequencies more difficult (in general) to generate. All this in turn suggests an upper limit of around 700 trillion switchings per second. With a Moore's or Kryder's Law like rate, say doubling bit rate every two years, today's 10 billion bps goes to 700 trillion in about 33 years.
T. M. Pederson
"Lies, Damn Lies, and Documentation"
Slightly more correctly, the drift velocity of electrons in standard copper cable is on the order of (tens of) cm/s. Actual electron velocity is close to c (as they bounce around in a cable), and electron drift velocities can be on the order of 10^7 m/s in some media.
What these guys have found is a physical effect that possibly could lead to fast modulation of light. Neglected in the press release are a few fairly important issues:
All that being said, this is still very exciting. It is a new physical effect demonstrated in a silicon-based material, and a physical effect that has been used elsewhere to do useful things. Hopefully a real modulation device will come along shortly.
Climbing the corporate ladder != Innovation
Innovation?! C'mon! This is a culture in which people really do use words like "synergy" and "value-added" with straight faces! I know; I've worked with them!
Each time I've worked in a corporate environment, I've been thoroughly appauled. People don't pursue good ideas! Rather, they make sure that they have all the right "check marks" on their "report cards." At the last place I worked, there were so many half-assed useless projects lying around -- wastes of time and money -- which could have been made useful if the resources had been put into them to do them right. But they weren't, because that's not how the incentive structure works.
When the end of the quarter comes around, you're faced with a choice: Have I "met my goals" (your immediate supervisor will be inclined to say that you did, because it'll make him look good), and pick up a fat bonus -- or do you finish the job right?. Of course you choose option 1; you play the "incentive structure" for all it's worth.
You make the right moves. You cozy up to the right people. You do everything you can to look good. You do not investigate great new ideas.
Political scientists speak of "collective action problems." The corporation is a legal construct, and the laws that govern it seem tailor-made to create collective action problems. The individual incentives that corporatism puts in place spur individual actions which do not sum to positive collective action. That is, each worker puts the right checkmarks on his report card, but the company does not pursue goals - like investing in new technology - on which its future ultimately depends.
It's because of the "incentive horizon." People pursue goals "within their horizons." Investment culture, and legal obligations to shareholders, dictate that the incentive horizon is approximately three months long. Why don't we have decent broadband in the US? Because infrastructure takes time and has delayed returns. Successful cultures emphasize the importance of 'delayed returns,' but corporatism as it is currently practiced does not. There's a famous explanation in political science for why hereditary monarchy is rationally preferable for a people than is a series of dictatorships by unrelated people: The monarch has a larger "incentive horizon," and so will seek to build a country that will serve him and his decendants. He will tax at the maximum level which does not significantly harm economic growth, because, integrated over time, this represents his largest possible profit. The despot, in contrast, has a shorter incentive horizon, and so it is not rational for him to pursue delayed returns: He taxes everything immediately, seizing farms and industrial equipment. His actions mean that soon the public will not be able to generate new tax income to tax, but, in the short time-span in which he is operating, that is entirely rational. The problem is that modern corporatism creates this second incentive structure. Other countries, like South Korea and Japan, have succeeded in developing good broadband because they have succeeded in using government regulation to effectively change the incentive structure for corporations. The incentive horizon is longer for them. Probably still not optimally large, but longer.
So what is an innovator to do? Certainly don't get caught up in the mess that is corporate culture. Me, I'm seriously thinking about a PhD and research. I've been nothing but impressed with academic scientists.
Mommy, can I have $25,000 to buy the new 10k Ghz Dell Diamond Dimension pleeeeeeeeeeeeeeeeeease?
Horns are really just a broken halo.