Slashdot Mirror

← Back to Stories (view on slashdot.org)

Researchers Unveil High-Speed Laser Communications Device For Space

Posted by samzenpus on from the saving-your-laser-minutes dept.

coondoggie writes "Using lasers to communicate quickly through the long distances of space has generally been the purview of science fiction. But researchers at the National Institute of Standards and Technology (NIST) and NASA's Jet Propulsion Laboratory (JPL) are out to change that notion with a prototype array (pdf) that can read more information — and allow much higher data rates than conventional systems — than usual from single particles of light. Lasers can transmit only very low light levels across vast distances, so signals need to contain as much information as possible, NASA said."

8 of 40 comments (clear)

  1. Not *that* new by cheesybagel · · Score: 4, Informative

    Using lasers to communicate quickly through the long distances of space has generally been the purview of science fiction.

    The ESA Artemis satellite used the SILEX laser link to communicate with the SPOT-4 satellite. It was not the first project to use laser communications in space either. The datarates mentioned in this article are better than those of SILEX though.

    1. Re:Not *that* new by bigpat · · Score: 2

      And LADEE recently demonstrated a laser communications system with data rates about ten times over what Artemis demonstrated.

      I think these articles and summaries that appear on Slashdot would better serve the community if they took a moment to figure out what the new part of "the news" really is. This sounds like an improvement which will enable more efficient laser communication over longer distances than was demonstrated with LADEE. So, an improvement more applicable to deep space probes or maybe allow the packing of more sensors on Earth observing satellites which will then have more bandwidth to transmit all that data.

  2. photons are photons by Anonymous Coward · · Score: 2, Informative

    Does it matter whether the emitted photons are from RF or Light? They both travel at the same speed.

    1. Re:photons are photons by EmperorArthur · · Score: 4, Informative

      Yes. The energy that gets you one single green photon gets you 75000 radio photons at the Cassini probe's X-band comm frequencies, for example. Having 75000 times more quanta means your system can be built on well-known classical principles (i.e. standard microwave radios) and work as expected.

      But can one green photon hold more information than an RF photon?

      The trick is when you're talking about bandwidth. "A key characteristic of bandwidth is that any band of a given width can carry the same amount of information, regardless of where that band is located in the frequency spectrum." Visible light is approximately "430–790 THz." While X-Band is "8.0 to 12.0 GHz" So you're talking about hundreds of THz vs 4 GHz.

      Nyquist says the absolute maximum symbol rate is equal to twice the bandwidth. This means that once you've hit that cap, the only way to send more data is to either increase the number of bits per symbol or increase the frequency. Increasing the symbol rate can end up taking expensive delicate equipment, so it's easier to just throw a second transceiver at the problem. The second one would be exactly like the first, but would be operating at a slightly different frequency. The spectrum for light is a much larger playground for this than X-Band is.

      https://en.wikipedia.org/wiki/...
      https://en.wikipedia.org/wiki/...
      https://en.wikipedia.org/wiki/...
      https://en.wikipedia.org/wiki/...
      https://en.wikipedia.org/wiki/...

      --
      So lets pretend that we've just completed writing this code, as opposed to having just completed sabotaging it -Altera
  3. Re:About Time! by Seranfall · · Score: 2

    I've invested way too much time to movies and books to not see laser communications, to at the very least, to the moon in my lifetime. There are many authors that have enjoyed my 25 cents or less of royalties they received that should finally be vindicated by including laser based communications in their books!

    to...to... to.. damnit..

  4. High-speed? High bitrate... by Anonymous Coward · · Score: 2

    ...unless their laser can send signals traveling faster than the speed of light.

  5. Hard To Aim by Githaron · · Score: 2

    According to the article, they use positioning information to generate additional bits of information. My question is how do they determine position at large distances when both bodies are obviously not standing still. The only thing I can think of is having one constant laser being used as a position reference for all communication lasers. Of course, they still have to be able to hold the laser on the detector array.

  6. optical multiplexing... by sugarmatic · · Score: 2

    ...also exploits polarization to a high degree. In fact, many developmental optical communication systems exploit polarization purity for higher base digital transmission, and even if polarization modulation slows things down for some schemes, the resulting bandwidth can overcome the obstacles by an order of magnitude or more over the reduced rate of the mux/demux. The issues with these schemes is more about cost. But most of these programs are directed at n-fold increases in existing optical fiber network bandwidth. Their time will come.