Beta
×

Welcome to the Slashdot Beta site -- learn more here. Use the link in the footer or click here to return to the Classic version of Slashdot.

Thank you!

Before you choose to head back to the Classic look of the site, we'd appreciate it if you share your thoughts on the Beta; your feedback is what drives our ongoing development.

Beta is different and we value you taking the time to try it out. Please take a look at the changes we've made in Beta and  learn more about it. Thanks for reading, and for making the site better!

Optical Memory Could Speed Up the Internet

timothy posted more than 2 years ago | from the anything-could-anything dept.

Networking 36

ananyo writes "Bits of data travelling the internet have a tough commute — they bounce back and forth between optical signal lines for efficient transmission and electrical signal lines for processing. All-optical routers would be more energy efficient, but their development has been hindered by a lack of optical memory devices. Now, researchers have developed just such a device (journal article abstract), paving the way towards a faster, more energy-efficient internet. The devices are based on optical cavities that can be switched between light-transmitting and light-blocking states to construct digital signals. Researchers have been working on such devices for several years, but previous versions used too much power and could not retain data long enough. The new memory cells use just 30 nanowatts of power, 300 times less than previous designs, and can retain data for one microsecond — long enough to support processing." (See also this paper on all-optical swtiches by four of the same authors.)

Sorry! There are no comments related to the filter you selected.

Optical Keyboards Could Speed Up Posting (-1)

Anonymous Coward | more than 2 years ago | (#39166347)

FROSTY BITCHES

Nonsense (-1, Flamebait)

gweihir (88907) | more than 2 years ago | (#39166397)

As most of the time in long-haul connections is actually spent traveling, this sounds like nonsense to me.

Re:Nonsense (1)

Anonymous Coward | more than 2 years ago | (#39166433)

As most of the time in long-haul connections is actually spent traveling, this sounds like nonsense to me.

If you have a faster processing of a packet then the router can begin work on a new packet, this may help in the speed looking at the whole picture not just the single connection.

Re:Nonsense (4, Informative)

w.hamra1987 (1193987) | more than 2 years ago | (#39166449)

actually no, the travel time is much shorter than that of processing. in fiber-optic networks, latency appears on the nodes.

Re:Nonsense (1)

fluffy99 (870997) | more than 2 years ago | (#39166461)

Plus there is nothing in the optical realm that even approaches the processing power of an electrical based CPU. Optical routing, even with this very transient optical storage ability is still quite a ways off.

Re:Nonsense (3, Informative)

forkazoo (138186) | more than 2 years ago | (#39166491)

Actual link latency doesn't effect throughput, while all the time spent going from optics->CPU->optics does. If you could build an all optical router, it would be theoretically capable of very good results. Also, fiber is frequently used for much shorter hops as well. We have hundreds of optical links at the place where I work, and that's all inside a very small room. If more of the infrastructure was 100% optical, that could improve things a lot over the next few years.

Re:Nonsense (4, Informative)

Anonymous Coward | more than 2 years ago | (#39166515)

Umm, do you know how fast the speed of light is? It's not speed that is the issue, it's the time requires to process the light which is the issue. If it takes 5ms to process light, that means that light has to be made in pulses of 5ms or else signal is lost. Longer pulses = longer travel time in a way. That is why processing purely in optical extremely important as conversion between optical to electron and back is slow in comparison to a pure optical router. When you have lots of routers between endpoints, speed is basically reduced down to switching speed which is the true bottleneck. Remove the switching and you remove the bottleneck. Now, it won't remove the switching speed at the endpoints but it does reduce the latency from switching that occurs in between.

Re:Nonsense (1)

Anonymous Coward | more than 2 years ago | (#39166871)

speed of light in fibre is about 0.6-0.7c. If we assume 0.7c, in 10GE, 1500B IP packet is about 260m long.

Normal router (not low latency switch, which is order of magnitude faster) takes about 10us to process packet, this is equivalent of 2100m of fibre.

So if you consider transatlantic link or even use intracity links of 100km or so, time router spends processing is almost negligible to the observed RTT, it is only limited by speed of light.

Use case for optical switching isn't about reducing latency, it'll make some electrical engineering problems easier to solve.

Re:Nonsense (2)

tibit (1762298) | more than 2 years ago | (#39169431)

This is informative and insightful. Google agrees: (2100 m) / (0.7 * c) = 10.0069229 microseconds. Gotta love their calculator, but one wishes it also provided accuracy in the results that got something to do with presumed accuracy of the constants in the expression. As given, the result should have no more than 2 digits of the significand shown. The way things are, we get grad engineering students who mindlessly put those useless digits in the reports, exams, etc. Never mind all the undergrads who seemingly have a digit fetish (at least in the U.S.).

Re:Nonsense (0)

Anonymous Coward | more than 2 years ago | (#39172133)

Right. 0.07+0.07 ~= 0.1 and 0.11-0.022 ~= 0.088.

That's what we've been told so it must be correct.

Re:Nonsense (2)

LordLimecat (1103839) | more than 2 years ago | (#39166899)

A) electricity does not always propagate at the full speed of light.
B) assuming it does, it is still a significant latency factor-- ping times of 200ms from New York to Shanghai are reasonable (depending on your ISP), and speed-of-light delays would contribute 50+ms to that each way assuming a straight westbound path (which is unlikely). (Note that it IS shorter to fly north instead of west, but that is not how the cables are laid).

If you were to ping all the way into a local chinese endpoint, you would see significant latency occur at the transition from US routers to Chinese routers, but I assume that is because of the crazy IDS / DPI stuff they do.

Re:Nonsense (1)

necro81 (917438) | more than 2 years ago | (#39171401)

A) electricity does not always propagate at the full speed of light.

The speed of light in an optical fiber is about 60-70% of c. This can be divined from fiber's refractive index (1.50 [wikipedia.org] ). Or you could just Google it [google.com] .

So light travels at about 200,000,000 m/s in an optical fiber. That would make the propagation time to encircle the equator (40,000,000 m) about 200 ms. NYC to Beijing (11,000 km most directly, 14,000 km westerly) around 50-75 ms each way. Overall, propagation time in long-haul situations is still about 1/2 the total latency. But there are lots of situations that use fiber in the short- and medium-haul, and oftentimes several hops along the way, where the propagation time is negligible compared to the time lost in switching.

Re:Nonsense (1)

LordLimecat (1103839) | more than 2 years ago | (#39179289)

Switching time is generally on the order of microseconds. Routing time COULD be longer, that depends. Number of hops to local destinations is generally going to vary between 4 and 8 hops, depending on ISP.

For local destinations, latency should be around 15-30ms. The majority seems to happen when you shift from one ISP to another; I dont know the full reasons. If you are staying all within comcast, your latency can be astonishingly low. (10ms)

Re:Nonsense (1)

Ferzerp (83619) | more than 2 years ago | (#39168277)

The speed of light is a huge issue.

Try to design a system for a synchronous data replication from, say, New York to San Francisco. You can't without killing performance because the round trip time between the two for fiber or copper connections is 40ms. Even with 0 switching time, the speed of light is too slow to do such a thing.

Re:Nonsense (0)

Anonymous Coward | more than 2 years ago | (#39167099)

you're confusing latency for throughput

No - do not accept bad language (-1)

Anonymous Coward | more than 2 years ago | (#39166399)

"300 times less". So if the previous energy was 1 watt, "300 times less" means that it's producing 299 watts of power. Is it so hard to say "1/300th" or 0.33%?

The heart of the "memory" (3, Interesting)

arnoldo.j.nunez (1300907) | more than 2 years ago | (#39166451)

From the Nature News link:

When a particular wavelength of light shines on the cell, the material’s refractive index changes so that it either will or will not transmit a pulse of light, to create either a "1" or "0" bit. Another light pulse can reverse it. A second laser provides constant background light, called bias, which helps the memory cell maintain its state.

So the key is that the medium is able to change its refractive index sufficiently so that there is total external reflection apparently (0) and (almost) complete transmittance (1). Thus, the medium's optical properties (index of refraction which is ultimately a measure of the speed of light in that medium due to the material's permittivity and permeability) dictates its nonvolatile memory applications. You change the medium's optical properties itself with a "write" laser.

The "read" laser (which they call bias but is a bit confusingly used to me) allows you to read off the "memory value" (really just transmittance as a function of the index of refraction set again by the "write" laser).

So the power consumption comes from using two lasers. So it makes me wonder, can you cut down the power requirements by using an LED with a monochromatic wavelength filter? Sure it won't be very efficient in getting a single wavelength, but perhaps you don't need that much optical energy?

Re:The heart of the "memory" (1)

Pseudonym (62607) | more than 2 years ago | (#39168281)

So the power consumption comes from using two lasers. So it makes me wonder, can you cut down the power requirements by using an LED with a monochromatic wavelength filter? Sure it won't be very efficient in getting a single wavelength, but perhaps you don't need that much optical energy?

LED + feedback cavity = laser diode

MOD PARENT +1 INSIGHTFUL!!! (0)

Anonymous Coward | more than 2 years ago | (#39169181)

this dude is FUCKING smart as shit!

Lack of optical memory devices? (4, Funny)

jovius (974690) | more than 2 years ago | (#39166469)

The researchers seem to have missed the huge leftover stock of photographic film. Stopping it completely provides indefinite storage while spinning it 1 mega frame / second satisfies microsecond processing needs.

Re:Lack of optical memory devices? (3, Informative)

Sulphur (1548251) | more than 2 years ago | (#39166573)

The researchers seem to have missed the huge leftover stock of photographic film. Stopping it completely provides indefinite storage while spinning it 1 mega frame / second satisfies microsecond processing needs.

I remember someone spinning a bit of metal at 10^6 rev/sec. It was the size of the period on a typewriter. At 1.5x10^6 or so it exploded. I suspect that the gelatin would spin off much earlier.

Re:Lack of optical memory devices? (0)

Anonymous Coward | more than 2 years ago | (#39173465)

.5 mm diameter (size of a printed period) @ 1MHz induces about 10^9 g's.

Re:Lack of optical memory devices? (1)

jmottram08 (1886654) | more than 2 years ago | (#39166635)

You do know that film has to be developed first, right?

Re:Lack of optical memory devices? (1)

ericloewe (2129490) | more than 2 years ago | (#39166771)

I'm pretty sure you're trolling, but somebody should try that kind of approach. Just for the laughs.

The most efficient way to speed up the internet (-1)

Anonymous Coward | more than 2 years ago | (#39166651)

Keep niggers from pirating.

How many bits can they store? (3, Interesting)

Animats (122034) | more than 2 years ago | (#39166845)

The article skips over the issue of how many bits they can store. It does indicate that numbers > 1 have been achieved, but RAM in megabit, let alone gigabit size, seems to be a long way off.

There have been a few optical switches with fiber optic delay loops. If a packet comes in and the outgoing link is busy, the packet is shunted to a delay loop for one packet time. This works best if the packets are all the same size, like ATM, but it's been made to work with variable sized packets. So far, there's not much commercial technology in the area. Lots of papers, though. People have been working on this problem for over a decade, and there's a little progress each year.

A few bits of pure optical storage and logic will help. If there's enough to handle packet routing and tags, a useful switch can be all-optical, even if storing the data packets themselves in "optical RAM" isn't feasible.

Cool beans! (0)

Anonymous Coward | more than 2 years ago | (#39167391)

So...anyone got any super-fast optical memory?

"Pay for article here" (1)

nurb432 (527695) | more than 2 years ago | (#39167615)

They can go to hell. Where was this done? Did they use ANY public funds? If so, i already own it, so give me the damned article.

Re:"Pay for article here" (1)

Amorymeltzer (1213818) | more than 2 years ago | (#39168679)

This work was supported by the National Institute of Information and Communications Technology (NICT).

NICT [wikipedia.org] , for the record, is in Japan, so unless you are a Japanese taxpayer (who, based on your sig, also feels very strongly about slavery during the 1860s in the USA) no, you do not own the article.

Re:"Pay for article here" (0)

Anonymous Coward | more than 2 years ago | (#39169267)

The United States forced Japan into submission with its atomic bombs; the US owns Japan, eternally and utterly. That would include the output of such a puppet institute.

So, begging pardon, he does still "own it."

submarine cable repeaters (1)

kupojsin (681728) | more than 2 years ago | (#39168835)

Fiber optic or not submarine cables still need optical repeaters every 100km or so. Moving these to optical switches would allow for easier deployments.

hm... (1)

Anonymous Coward | more than 2 years ago | (#39169385)

I can't see optical memory being a big improvement by itself; you'd still have to switch to electrons to go through the processor, then convert back to photons for transmission.

Now optical processors, that would make a BIG difference.

Re:hm... (1)

tibit (1762298) | more than 2 years ago | (#39169461)

And that should end the discussion. Right there. Because in a router, or a switch, you actually process data. As in, you know, making decisions based on the values of those bits coming in, and shit. It makes no sense to try hard to make only a small part of it optical, as in optical memory. You need the whole thing optical or else it won't make any sense, economically, energy-consumption-wise, or otherwise.

Re:hm... (1)

gagol (583737) | more than 2 years ago | (#39170145)

One have to start somewhere...

Re:hm... (1)

tibit (1762298) | more than 2 years ago | (#39172043)

Sure, but that's of no practical importance right now. It's a step in the right direction perhaps, but only of academic interest at the moment. When they do a whole router using optical computation, then it'll be big news. I'd hope they'll be there in another 25 years.

you could improve all you want (0)

Osgeld (1900440) | more than 2 years ago | (#39169453)

it does not change the fact that my internet connection is on shared bandwidth copper for dozens if not hundreds of miles, hitting a 20$ netgear router

increase speeds by 10 fold, doesnt matter to me, cause the price to home service is retarded and I will not feel a single bit of it ... or in other words get your shit straight

Check for New Comments
Slashdot Login

Need an Account?

Forgot your password?