back to article Fibreless fibre optics developed by US Air Force

US Air Force boffins say they have created wireless links of similar capacity and quality to optical fibre, allowing extremely high mobile bandwidth and - perhaps - the use of quantum encryption methods without a physical connection. US air force airborne fibreless laser link. Credit: AFOSR How to take fibre to a plane in …


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  1. Anonymous Coward

    Okay, so it's got line-of-sight limits

    But couldn't this be useful as a regular point-to-point link, i.e. as opposed to microwave links which are frequently unreliable and can interfere with other microwave-frequency signals?

    Could this be the tech that finally gets high-speed internet to rural areas?

    Also, can it be adapted for normal "home" use- I've got a friend over the river and our unidirectional WiFi link's (a) a bit crap and (b) frequently hijacked by his neighbours son to torrent films and download porn.

  2. SkippyBing

    Fog, Clouds, Rain, Locusts etc.

    I'm guessing they might interfere with it a bit no?

  3. Anonymous Coward

    Free Space Optics

    Quantum crypto aside, isn't this just an incremental improvement to conventional free space optics that have been around for many years? Yes, you'd possibly get longer distances and/or higher bandwidth but it's truly line of sight and I doubt that even adaptive optics can overcome the affects of rain, fog, snow, etc.

  4. Nigel Callaghan Silver badge
    Thumb Down

    Easy to disrupt...

    As the military are behind this they're presumably looking at options for use on the battlefield. But how effective are adaptive optics when some unsporting insurgent floats a nice reflective (or non-reflective) balloon in the path of your link to base? Or will this link have to go straight up to some big balloon that's out of range of ground-to-air missiles? What was that quote about a computer with a bullet in is just a paperweight? - stick to the low tec guys!

  5. Jess Baughan

    Great technology

    as long as there is no rain, snow, fog, smoke or anything else to get in the way.

  6. amanfromMars 1 Silver badge

    Whatever Next for Continuity of Server Services?

    Seems like a novel solution for a perennial problem, Lewis.

  7. James 55

    Damn directional

    Unless you could get physically between the communicating bases/warships/planes then you couldn't even begin to eavesdrop, no?

    If you can't listen in, the next best thing is to stop them talking to each other. Smoke bombs anyone?

  8. aaronlow
    Thumb Up

    This is great news

    One more instance that DoD spending is great news. I hope that this technology will be declassified (assuming it is classified) for the general public to miniaturize. It will however, be expensive for a long while yet.

    For businesses and for RF spectrum users, this will be great news; we might eventually get better quality OTA HDTV signals (with less compression).

  9. Gareth Davies

    So it's Free Space Optics Redux?

    Free space optics have been around for years and have failed to capture any significant market share from P2P Microwave for the simple reason tat the links fail in fog and I can't see what the Air force version will be able to do differently. Fog attenuates light and the only way to overcome attenuation is to either increase receiver sensitivity or transmitted power. If it's powerful enough, the beam could literally 'burn' through the fog, but the power levels required over a 35km link would be astronomical.

    I think the key though is Mobile. The link could be a beacon type system that could be used to communicate point to multipoint across a battlefield, with variable throughput/range determined by the prevailing conditions.

    The answer to AC's question regarding this being the technology that gets high speed broadband to rural areas is no. Standard MW links can already offer an uncontended bandwidth of approximately 1GBPS to a single user over up to 25km these days, so when you factor in the fact that most people can't tell the difference between 24Meg BB and 100Meg BB, that bandwidth is more than enough to satisfy a rural community (20:1 Contention at 24Meg with 1GBPS backhaul gives true high speed internet to over 800 homes! Even at 100Meg it would serve 200 Homes). The reason it isn't being done is that the investment in the kit isn't warranted on the basis of the Customer take up and the price they'd pay. The core couldn't cope, let alone the access network!

  10. Swarthy
    Thumb Up

    I agree with AC 16:54

    This design could, in thoery, down the line, after a few years, be an excellent network bridge, providing you had clear line-of-sight. This could also be useful if we get that proposed colony/station on the moon.

  11. His Geekishness
    Thumb Down

    not news.

    Oh please, the use of adaptive optics in communications is exactly as old as adaptive optics.

    Also, @ac above, no it wont make cheap com links anytime soon; usefull adaptive optics involve a lot of fragile and high precision parts, professional maintainance and calibration. I actually can see how they might be manufactured cheaply, but not how they could be run cheaply and/or reasonably reliably in a mass- market.

  12. Anonymous Coward

    Let me be the 1st post to say

    Beam me down! Scotty!

  13. Anonymous Coward
    Black Helicopters


    "Any attempt to intercept such info would by definition involve changing it, meaning that any eavesdropping would surely be detected"

    i sure hope they're not relying on that! It wouldn't take long with a fog machine to create a light mist that would show the light without blocking it... from there it's trivial to drop a few eaves.

    OK, the lower signal strength might trigger a flag, but if that's enough for them to abandon that comms channel, they're gonna struggle in mist/fog, low cloud, sand storms, smoke from burning tanks, etc, etc!

  14. Anonymous Coward
    Anonymous Coward


    that would be optics then not fibre optics :)

  15. Adam Azarchs

    Freespace optical interconnecct

    A the risk of restating what others have already stated, free-space optical interconnect has been around for a long time now (like ClearMesh). It failed commercially because about the same time it became technologically viable, 802.11b took its market away. Militarily, while less susceptible to traditional jamming technology, it's more susceptible to stuff like, say, smoke. Of which there tends to be a lot of around a war zone as soon as things get interesting. So basically, move along, nothing to see here.

  16. Anonymous Coward
    Thumb Up

    so how far and when...

    great now a question or two...

    "The idea is to use a laser beam through the air to carry information optically in the same way that sending light down fibre works."

    generally speaking, how far can say a 1 millimeter wide generic off the shelf laser with adaptive optics travel before it becomes 10 millimeters wide in air, in water, in space......

    how much micro power is required to produce this beam and modulation.demodulation.

    ;) when can we get SOHO laser fitted ROUTERS with bonded Ethernet interfaced to these point to point, and point to multi-point devices for our chimneys as i want to have my own personal ISP grade community lead laser WAN setup as soon as possible to bypass the UKs ISPs and mandelsons Govt plans for taking over and take away the free internet and making it a totally commercially run ONLY enterprise.....

    if everyone gets few of these and sets up a basic meshed laser-WAN (LWAN) and a few low power freeNAS terabit boxs tucked away in your spare room ,then the commercial ISP's can start paying us all for their P2P traffic and we can kick them off if they are reported as using our copywrited website material :)

  17. Anonymous Coward
    Paris Hilton

    two words

    smoke bomb.

  18. It wasnt me

    @AC 22:16

    Go and read up on quantum encryption. If you still think that eavesdropping by projecting onto fog is "trivial" then go get yourself a job in quantum communications. You will become a very rich man, almost overnight.

    Best of luck ......

    Clearly a boffin.

  19. Paul 4


    Optic comunication is alot more complex than that, but basicly in this case they are talking about quantem encription, which you can't do that with. Anything that messes with the key (i.e. tryes to look at them) will change the state of the photons and will be detected.

  20. M7S

    I thought the police were arresting people shining lasers at aircraft these days

    Also how will that work in a war zone (not the one above South London) with the pilot worrying about a new form of enemy "lock-on"?

  21. Bumbling Fool

    Quantum Hokum?

    Hughes (amongst others) has been working on free space quantum key distribution for some time. The original idea, invented by IBM and the Uni of Montreal, was demonstrated using free space optics over a distance of about 30cm. At that time they didn't think it would work in fibre. A collaboration between BT and the Defence Research Agency (now Qinetiq) established that the technique could be made to work in fibre. Fibre systems can now reliably establish keys over about 150km and free space systems (both commercially available) have managed around 30km (the best I last heard of).

    Calling the thing quantum encryption is a misnomer because it's basically a key distribution system in which the laws of physics guarantee the security of the key (provided everything has been set up right of course - there's more than one way to skin a cat). The key can then be used either in conventional symmetric crypto systems or, if the quantum key rate is high enough, in one-time pad systems which provide perfect secrecy.

    The idea is that the key information is transmitted in a single quantum state. The security is provided by a clever use of, effectively, the Heisenberg uncertainty principle. The information being randomly encoded in one of two complementary bases. Precise measurement of one basis will destroy any information about the other - so if an eavesdropper gets the coding basis wrong she'll destroy the information contained in the actual coding basis.

    Bits that never reach the reciever never form part of the key so the system is robust against loss. If the error rate, caused by an eavesdropper, or some other physical disturbance, is too high then a key cannot be securely established. But below a certain error rate a secret key can be established with precise limits known about how much information could possibly have been leaked about the key to an eavesdropper. This information leakage can be made arbitrarily small by sacrificing enough key bits.

    The comms requirements on the quantum channel are different to those needed for the conventional communication. if you're going to use a symmetric algorithm (say 256 bit AES) then you only need to establish 256 bits of secret key. When this has been established you can use any channel you like to send your encrypted communication hopefully at a much higher data rate.

    The security of QKD depends upon a number of factors

    - the ability to generate, modulate, and measure single quantum states

    - a true random number source

    - establishment of an authenticated channel between sender and receiver

    - the assumption that the laws of quantum mechanics cannot be violated

    In a battlefield scenario, for example, the ability to send keys over free space could be quite useful. The beauty of QKD is that it also allows extremely rapid update of key material - giving it the ability to be used as a technique for securing sessions without the need for dependence upon a more secure 'master' key. Of course, one still needs to have established the necessary authentication mechanism, otherwise man-in-the-middle attacks can be performed (although technically difficult).

    In terms of future threats then QKD may well prove to be an interesting alternative to conventional methods of key distribution, particularly when quantum computers start biting. With a well-designed algorithm the fastest form of attack is exhaustive key search (that's the design requirement). Quantum computers effectively can only reduce the key size by a half (the best they can do in search techniques) so QKD systems will remain secure against quantum computers, provided they don't use asymmetric crypto techniques based on factoring or discrete logs for their authentication.

  22. Charles 9 Silver badge

    @Paul 4

    What people are saying is that while quantum encryption is self-detecting, it does nothing to stop someone whose goal is simply to DISRUPT the communication. After all, in battle, sometimes a message disrupted is as bad as a message intercepted.

  23. Wemb

    Fibreless fibre optics?..

    with line-of-sight restrictions. Doesn't this == semaphore?

  24. Bumbling Fool

    DoS Attacks

    "What people are saying is that while quantum encryption is self-detecting, it does nothing to stop someone whose goal is simply to DISRUPT the communication. After all, in battle, sometimes a message disrupted is as bad as a message intercepted."

    Absolutely and QKD systems are vulnerable to DoS attacks, but because the quantum and conventional channels do not have to share the same properties, ensuring a successful DoS attack on one is not necessarily equivalent to ensuring a successful Dos attack on the other - it certainly can be. Disrupting the quantum channel without disrupting the conventional channel ensures that keys cannot be distributed but does not stop the conventional communication.

    But if your intent is to simply disrupt the conventional communication then no amount of crypto is going to prevent that. I haven't yet seen a key distribution system or crypto algorithm for fibre communications that is proof against a JCB.

  25. Anonymous Coward
    Thumb Up

    Re: Bumbling Fool

    Thank you sir, you answered all of my questions in elegant fashion. Its days like these when I remember why I read the Register!

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