9 ms·

Free-space optical links for space communication networks

46 points by privong 6y ago

gioscarab 6y ago
Really cool thanks for the link. I have experimented a lot with the OOK modulation and open-air laser wireless communication. It can be done just using visible light LEDs as detectors and small laser diodes, they just need to be of the same color. A free-space optical link can be built in minutes, see https://github.com/gioblu/PJON/tree/master/src/strategies/AnalogSampling https://github.com/gioblu/PJON/tree/master/src/strategies/An...
arijun 6y ago
I can't wait until Starlink starts implementing their planned optical links and unleashes intercontinental lower-than-fiber latency.
- chokeartist 6y ago
  It is very exciting times. From a business model perspective what is interesting to me is thinking about how the LONDON<->NYC low latency demand (finance/tickers) will effectively offset the cost for Starlink to offer service in remote (rural) areas; they can do this due to the fact that they are in the same orbital coverage area. Add on boats & airplanes - and now we really are in the 21st century (not trying to sound glib, I have wanted this for a long time). :)
- bjeds 6y ago
  They may "unleash intercontinental lower-than-fiber latency", but they also unleash light pollution. Where do you live? In most of Europe and SE Asia you can get gigabit broadband. I think SpaceX is a cool company and I could see myself work there, but StarLink is, IMHO, a shitty project that ruins the night sky and space for everyone. https://en.wikipedia.org/wiki/Starlink#Criticism https://en.wikipedia.org/wiki/Starlink#Criticism
  - toomuchtodo 6y ago
    Would you feel the same way if observatories were lifted beyond Earth orbit where their view was never obstructed? There is so. much. space out there, and it seems silly to argue over the artificial scarcity of clear sky when we can solve this with technology. We’re even putting a global comms network in place that could support high speed science data store and forward from space observatories to science consumers on ground. What if we could churn out orbital science platforms as fast as SpaceX churns out Starship SNs and StarLink satellites?
    - bjeds 6y ago
      If you look at the article I linked, you can clearly see that the satellites are visible from the ground (the photo from Germany). If you search for "starlink" on Flickr you can see more examples. This is light pollution.
      - ethbr0 6y ago
        The reason you're getting downvoted is that your base argument is that we shouldn't have cars because then there won't be picturesque horse pastures to look at. The same has been said about offshore wind. Increasing global networking, and doing so in a ground-infrastructure-agnostic way, has the potential of connecting billions of people to the global internet in a cost-effective way. Sometimes, progress outweighs the cost. And parent comment presented a nice alternative approach for the specific astronomy case.
      - dukodk 6y ago
        That’s because they want photos of them. You don’t see them on images where they were removed by stacking. Try searching for ISS :wink::wink:
      - xoa 6y ago
        >you can clearly see that the satellites are visible from the ground (the photo from Germany) No, you've misunderstood (in numerous ways, but this is a specific one you've cited). That photo you linked is of a satellite "train", which is a temporary state of satellites after deployment as they take themselves the rest of the way to final deployment orbits. At that point they'll be both spread out and the albedo will be vastly lowered because SpaceX has already made design alterations to the sats so that in their operational alignment towards Earth they are far less reflective. They're not going to interfere with the sky from the naked eye, nor even for general photography, even from low light pollution rural areas vs typical urban ones. It doesn't help that you're almost a parody of "entitled, dismissive urbanite". Even in the developed world, tens to hundreds of millions of people have crappy DSL at best. Outside of the developed world that rises to billions. Marine and aircraft stand to make enormous gains as well. The demand for Starlink is clear and well founded, and you do your argument zero favors by trying to hand wave it away (unless you just mean to rant to no constructive end).
- mmmBacon 6y ago
  The capacity of these systems seems really tiny by modern standards as well as highly power inefficient. The fastest link demonstrated was around 5Gb/s at ~160W. This is about 3 orders of magnitude worse from an energy per bit perspective than fiber based systems. From that point alone, it’s hard to imagine these systems being cost competitive with existing fiber infrastructure. From a system capacity perspective these systems are about 500x less capacity. On page 26, it seems the primary application is being able to get more data down to Earth for remote sensing applications. The most important application of lasercom from LEO is direct-to-ground downlinks since the main point is being able to download to Earth the increasing amount of data that remote-sensing missions require
  - crispyambulance 6y ago
    Well, yeah, "space communication" in the title really means "SPACE"-- as in not on Earth. There's interesting considerations in space laser communications that you don't see in fiber such as "point-ahead" optics to account for the fact that the speed of light is finite and the target is moving. This can be thought of as the optical equivalent of peeing into a moving bucket. It's a fascinating review article.
vsareto 6y ago
>lasercom I'm calling it tight-beam and you can't stop me
- gclawes 6y ago
  Banks reference?
  - mrep 6y ago
    Not OP, but it is used in the expanse: https://old.reddit.com/r/TheExpanse/comments/2v9ej6/tightbeam_vs_radio/ https://old.reddit.com/r/TheExpanse/comments/2v9ej6/tightbea...
    - m4rtink 6y ago
      It is used in Expanse but as about any such nomenclature (belter, spaced, burn, etc.) it's using existing tried and tested SF nomenclature as it should instead of creating new one.
jonas_kgomo 6y ago
Free Space Optical Communication(FSOC) enables projects like Taara[0] from the Alphabet's X. This communication enables great internet infrastructure around Africa, especially coupled with already existing Telecommunication companies Fiber Optics(Project Equiano). [0] https://x.company/projects/taara/ https://x.company/projects/taara/
- reaperducer 6y ago
  I'm not sure what's new here. TV companies and others have been beaming data through the air with lasers for at least 30 years. When I worked in the television industry, it was how some of the TV stations in New York world get their skyline video back from their towercams in New Jersey. This was late 1990's. It was my understanding at the time that it didn't work well in rain and fog, but that was O.K., because there was nothing to see then, anyway.

46 points by privong 6y ago

Really cool thanks for the link. I have experimented a lot with the OOK modulation and open-air laser wireless communication. It can be done just using visible light LEDs as detectors and small laser diodes, they just need to be of the same color. A free-space optical link can be built in minutes, see https://github.com/gioblu/PJON/tree/master/src/strategies/AnalogSampling https://github.com/gioblu/PJON/tree/master/src/strategies/An...

arijun 6y ago

I can't wait until Starlink starts implementing their planned optical links and unleashes intercontinental lower-than-fiber latency.

chokeartist 6y ago
It is very exciting times. From a business model perspective what is interesting to me is thinking about how the LONDON<->NYC low latency demand (finance/tickers) will effectively offset the cost for Starlink to offer service in remote (rural) areas; they can do this due to the fact that they are in the same orbital coverage area. Add on boats & airplanes - and now we really are in the 21st century (not trying to sound glib, I have wanted this for a long time). :)
bjeds 6y ago
They may "unleash intercontinental lower-than-fiber latency", but they also unleash light pollution. Where do you live? In most of Europe and SE Asia you can get gigabit broadband. I think SpaceX is a cool company and I could see myself work there, but StarLink is, IMHO, a shitty project that ruins the night sky and space for everyone. https://en.wikipedia.org/wiki/Starlink#Criticism https://en.wikipedia.org/wiki/Starlink#Criticism
- toomuchtodo 6y ago
  Would you feel the same way if observatories were lifted beyond Earth orbit where their view was never obstructed? There is so. much. space out there, and it seems silly to argue over the artificial scarcity of clear sky when we can solve this with technology. We’re even putting a global comms network in place that could support high speed science data store and forward from space observatories to science consumers on ground. What if we could churn out orbital science platforms as fast as SpaceX churns out Starship SNs and StarLink satellites?
  - bjeds 6y ago
    If you look at the article I linked, you can clearly see that the satellites are visible from the ground (the photo from Germany). If you search for "starlink" on Flickr you can see more examples. This is light pollution.
    - ethbr0 6y ago
      The reason you're getting downvoted is that your base argument is that we shouldn't have cars because then there won't be picturesque horse pastures to look at. The same has been said about offshore wind. Increasing global networking, and doing so in a ground-infrastructure-agnostic way, has the potential of connecting billions of people to the global internet in a cost-effective way. Sometimes, progress outweighs the cost. And parent comment presented a nice alternative approach for the specific astronomy case.
    - dukodk 6y ago
      That’s because they want photos of them. You don’t see them on images where they were removed by stacking. Try searching for ISS :wink::wink:
    - xoa 6y ago
      >you can clearly see that the satellites are visible from the ground (the photo from Germany) No, you've misunderstood (in numerous ways, but this is a specific one you've cited). That photo you linked is of a satellite "train", which is a temporary state of satellites after deployment as they take themselves the rest of the way to final deployment orbits. At that point they'll be both spread out and the albedo will be vastly lowered because SpaceX has already made design alterations to the sats so that in their operational alignment towards Earth they are far less reflective. They're not going to interfere with the sky from the naked eye, nor even for general photography, even from low light pollution rural areas vs typical urban ones. It doesn't help that you're almost a parody of "entitled, dismissive urbanite". Even in the developed world, tens to hundreds of millions of people have crappy DSL at best. Outside of the developed world that rises to billions. Marine and aircraft stand to make enormous gains as well. The demand for Starlink is clear and well founded, and you do your argument zero favors by trying to hand wave it away (unless you just mean to rant to no constructive end).
mmmBacon 6y ago
The capacity of these systems seems really tiny by modern standards as well as highly power inefficient. The fastest link demonstrated was around 5Gb/s at ~160W. This is about 3 orders of magnitude worse from an energy per bit perspective than fiber based systems. From that point alone, it’s hard to imagine these systems being cost competitive with existing fiber infrastructure. From a system capacity perspective these systems are about 500x less capacity. On page 26, it seems the primary application is being able to get more data down to Earth for remote sensing applications. The most important application of lasercom from LEO is direct-to-ground downlinks since the main point is being able to download to Earth the increasing amount of data that remote-sensing missions require
- crispyambulance 6y ago
  Well, yeah, "space communication" in the title really means "SPACE"-- as in not on Earth. There's interesting considerations in space laser communications that you don't see in fiber such as "point-ahead" optics to account for the fact that the speed of light is finite and the target is moving. This can be thought of as the optical equivalent of peeing into a moving bucket. It's a fascinating review article.

vsareto 6y ago

>lasercom I'm calling it tight-beam and you can't stop me

gclawes 6y ago
Banks reference?
- mrep 6y ago
  Not OP, but it is used in the expanse: https://old.reddit.com/r/TheExpanse/comments/2v9ej6/tightbeam_vs_radio/ https://old.reddit.com/r/TheExpanse/comments/2v9ej6/tightbea...
  - m4rtink 6y ago
    It is used in Expanse but as about any such nomenclature (belter, spaced, burn, etc.) it's using existing tried and tested SF nomenclature as it should instead of creating new one.

jonas_kgomo 6y ago

Free Space Optical Communication(FSOC) enables projects like Taara[0] from the Alphabet's X. This communication enables great internet infrastructure around Africa, especially coupled with already existing Telecommunication companies Fiber Optics(Project Equiano). [0] https://x.company/projects/taara/ https://x.company/projects/taara/

reaperducer 6y ago
I'm not sure what's new here. TV companies and others have been beaming data through the air with lasers for at least 30 years. When I worked in the television industry, it was how some of the TV stations in New York world get their skyline video back from their towercams in New Jersey. This was late 1990's. It was my understanding at the time that it didn't work well in rain and fog, but that was O.K., because there was nothing to see then, anyway.