Terabit-Per-Second Class Connections over FTTH

Big Fat Dave writes "Thanks to research from Japan's Tohoku University, an article at Tech.co.uk wonders if someday the megabit and gigabit classes of net connections will join kilobits in the 'antique tech' bin. By doing some advanced mathematics and 'tweaking' existing network protocols, researchers may be able to enable standard fiber-optic cables to carry data at hundreds of terabits per second. 'At that speed, full movies could be downloaded almost instantaneously in their hundreds. At the heart of the development is a technique already used in some digital TV tuners and wireless data connections called quadrature amplitude modulation (QAM). One glance at the Wikipedia explanation shows that it's no easy science, but the basics of QAM in this scenario require a stable wavelength for data transmission. As the radio spectrum provides this, QAM-based methods work fine for some wireless protocols, however the nature of the optical spectrum means this has not been the case for fibre-optic cables ... until now.'"

Re:ya but..

[gad_zuki!]

>No "PC"s on "backbones" I think.

Then no terabit connection for you. I dont care how fast the backbone is. Where I live the last-mile technology is DSL which for my location maxes out at 1.5mbps.

I think the "OMG LOOK HOW FAST TIS IS" kiddie-mentality of movies-per-second ignores the whole issue of last-mile distribution. And PC buses. And practility. And economics.

Youd think slashdot would have better things to post than PR releases.

Hasn't the cable company been doing this for years

[NuttyBee]

I get something like 70 NTSC channels and everything above oh 400 Mhz on my cable system is QAM 256. I believe the cable company trucks the signal over fiber (QAM and all) to a local node where it is converted to RF and split into the house..

How is this new or different?

the vision

[Tumbleweed]

Actually, this opens up some interesting possibilities for people like the RIAA and MPAA. When you can download a whole CD or DVD in seconds, there's no longer much point to someone who's system is connected, in having physical media, or even a copy of the media, on their own machine. Whatever type of business model they'd wind up with could take that into account, and they could come up with a Netflix-type model, or something new and appropriate to the new reality (when have they ever done THAT, though?) - pay $x/mo, or $x/mo/bitrate/resolution, or whatever. The online rental business could be huge.

There's also the benefit of being able to do real-time offsite storage. The people who would care about needing massive amount of storage for their movie collection - no longer need to store their movies locally. Your whole machine could wind up being nothing more than an online access point with it being customized to be the HCI that you prefer: curvy keyboard (w/ or w/o lights) or not, big-ass widescreen display ... or not, your choice of colour, and a big honkin' net connection. Lots of RAM and a SSD boot drive, and something (magnetic card, keyfob, whatever, or nothing - just swipe your retina across a scanner or something) you can take with you to plug into whatever other machines you use to let that machine know it's you and to configure to your preferences. And nothing more. No moving parts other than the keyswitches and GP/CPU fan.

This is the kind of technology advancement that can change almost everything in its field if enough people with vision can take advantage of it and work together to make it seamless.

separate channels

[j1m+5n0w]

True, but the routers and repeaters on the backbone have buses don't they?

The way a lot of telco hardware gets around the limitation that no computer exists that's fast enough to process the full available throughput, is that the connection is split into hundreds of separate channels, each one on a separate wavelength. A particular router interface need only deal with one channel, not all of them at once. (A single channel might be an OC-192, which runs about 10 gbps.)

The channels are combined and split apart by a dense wavelength division multiplexer; I don't really know how they work, but if you think of it as an expensive prism you're probably not far off.

Re:QAM

[Wierdy1024]

I call foul, While technically possible to get the 1/4 phase difference to do QAM from very stable lasers, with two optical paths very slightly different lengths, and amplitude modulation of both, transmission of such a signal over long distances is going to be impossible. QAM suffers very badly from multipath, where different parts of the signal travel different distances. In the case of light, if the route the light takes varies more than ~100nm, the signal will be unrecoverable. Also, the laser must be fully stable and coherant for the full length of a transmission frame, and the optical path length must not change by more than ~100nm during the frame transmit time. In addioion, I don't think there is currently a way to modulate light that fast. Normally it would be done by modulating the current to the laser diode, but that can't work if seperate modulation of two phases is required. Theoretically, if this sort of thing was possible, my quick calculations indicate that making an assumption of 1 bit/Hz, and using approximately the entire visible spectrum, data rates of would be about ~300Tbits/sec. It's worth noting that due to the way current optical fibres are made, different frequencys travel at different speeds through the fiber, so QAM would never work using this much bandwidth. Instead, something like OFDM would be required on top of a lot of QAM channels. I don't know much about radio and modulation, so if an expert wants to correct me, I'd be pleased to learn more from them...

Re:ya but..

[evilviper]

Where I live the last-mile technology is DSL which for my location maxes out at 1.5mbps.

So because it won't specifically affect your internet connection, it isn't news?

I think the "OMG LOOK HOW FAST TIS IS" kiddie-mentality of movies-per-second ignores the whole issue of last-mile distribution.

FTTH is last-mile distribution.