Boffins smash 3Gbps speed barrier with 542GHz T-Rays
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Japanese geniuses have maintained a 3Gbit/s radio link at 542GHz, opening up more of the electromagnetic spectrum to the voracious appetite of wireless data.
Not that the research will lead to super-Wi-Fi any time soon - but if the proof-of-concept tech built by the Tokyo Institute of Technology can be commoditised then it will provide a useful point-to-point link albeit one that will struggle to penetrate non-conducting materials. The system has been described in Electronics Letters.
Lower frequencies tend to have better range and can pass through almost anything, which is why wireless technologies started at the lower end. But once we'd filled the low end with analogue radio and then television we ended up with mobile telephony at 900MHz, and by the time 3G came along it got pushed to 2.1GHz despite the difficulty that band has pushing through building walls and even our own atmosphere.
Commercial fixed links, and spectrum licences, run up to about 80GHz. You'll find BT, UK Broadband and a few universities with holdings in that space, used for point-to-point connection which are quite short range thanks to the irritating preponderance of oxygen in our atmosphere (which absorbs waves at about 60GHz just as water sucks up 2.4GHz signals from Wi-Fi or Bluetooth kit).
Ofcom has opened up some frequencies above those bands, pegging out some spectrum above 100GHz for unlicensed use should anyone take an interest in using it. But it's the cost of signal generating and detection equipment that is preventing exploitation of the upper end of the radio spectrum rather than any practical problems with the waves themselves.
It's the production of radio signals up to 300GHz that makes body-scanners so expensive. Perv-scan kit uses millimetre waves* running up to 300GHz, which penetrate clothing, but not skin, to reveal concealed bombs (as long as they're not strapped to one's side), but making and detecting radio waves at such frequencies calls for expensive kit.
Last year Korean semiconductor biz ROHM managed to sustain a 1.5Gb/sec connection at 300GHz using a technique similar to the Japanese team. ROHM continues working on the kit, and is promising 30Gb/s links within a few years, which should work fine through our atmosphere and penetrate walls as long as they're not made of conductive material.
The UK frequency plan tops out at 275GHz, and the last couple of hundred GHz is allocated, in huge chunks, to satellite communications and research projects as the cost of the kit discourages any other application.
300GHz radio has a wavelength of 1mm, while 3,000GHz (three terahertz) is a tenth that and the range is known as the T-Ray spectrum. The top end of that is pushing against (and into) infrared, which stretches up to 400THz and then we're into visible light and talking lasers.
That will be the absolute limit, but it's still a very long way off. The Japanese development, and the ROHM work which proceeded it, are useful steps to exploiting what politicians like to call a limited natural resource when they're auctioning it off. Research like this demonstrates just how much spectrum there is yet to be filled without having to retune our tellies or give up our wireless microphones. ®
* or backscatter X-rays, but let's not confuse things further. Half the perv-scanners use millimetre waves.
COMMENTS
"which stretches up to 400THz and then we're into visible light and talking lasers"
Where can one purchase one of these talking lasers? Is it like siri?
Re: If these wavelengths can hardly penetrate anything...
"For outside sure , its probably a non starter. But for across a room there should be an issue."
If you're only doing cross-room stuff, then modern 60ghz+ radio stuff would be absolutely fine, no? I thought the article was about longer ranged outdoor transmissions, which are a rather more tricky prospect. Indoors stuff though... I'd want to use radio, because my house is full of things which are opaque to visible, near and far infrared light. Some sort of IR strobe that bounces a signal off the walls sounds like it would just cause all sorts of crazy multipath degraded signals.
"Doesn't have to be a laser. Non lased light can do the job just as well using fast switched LEDs."
Oh sure; RONJA uses LEDs. That doesn't mean you'd want to stick your head under the rain hood, or peer at the emitter with a pair of binoculars to see if it is turned on.
Re: If these wavelengths can hardly penetrate anything...
You mean like your TV remote?
Fast switching of LEDs is how TOSLINK optical and TV remotes work. The bandwidth is very low as it can only use brightness for data transfer, because the LEDs emit relatively wide band, unpolarised random phase radiation.
That also makes them extremely reliable in terrible conditions.
In proper fibre optics the bandwidth is much higher because the laser diodes are extremely narrow band and in phase - if not polarised as well. So much more possibility for data transfer.
Which of course means they need very tightly controlled conditions - the inside of a glass fibre.
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