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Why couldn’t intersatellite laser links have similar capacity to fiber? In principle, if not practice? Is it because ISLs will require more powerful lasers bec
by rlt 6y ago
Why couldn’t intersatellite laser links have similar capacity to fiber? In principle, if not practice?
Is it because ISLs will require more powerful lasers because the light is focused through a lens instead of guided through a fiber?
- andbberger 6y agoprobably less (literal) bandwidth, lasers are expensive
- walrus01 6y agoThat and because the atmosphere is not clear (this is why 1Gbps free space laser network bridges have very limited range), the links from satellite to earth in any rf band will be very small in capacity as compared to a singlemode fiber cable. Space to space lasers, sure... Much clearer.
- andbberger 6y agoStarlink ground links are RF
- walrus01 6y agoThat's what I said
- andbberger 6y agooops my bad
- bbarnett 6y agoHigh end fibre routers use multi-spectral bandwith, effectively allowing for multiple data streams to be transmitted on one fibre cable, and re-broken out at the other end. This significantly increases bandwidth. I doubt the laser links support this, and I wonder if any could, when in a non-encapsulated environment. EG, spectral pollution from sunlight/etc.
- sandworm101 6y ago>> Why couldn’t intersatellite laser links have similar capacity to fiber? In principle, if not practice? Because laser energies, signal paths, traveling through free space must literally share that space with each other. It is effectively one wire. An underground cable can have hundreds, thousands, even millions of wires lying beside each other without interference. It is comparable to the difference between a wifi connection and bundle of ethernet cables. One can scale and one cannot.
- binaryblitz 6y agoI'll start by saying my understanding of the laser connection on the satellites is virtually nil. Could you just add more beams on each satellite?
- sandworm101 6y agoNo. The beams would overlap, which is fine of they are on different frequencies, but eventually you run out of frequencies to use. Fiber confines the beam to inside the fiber. No overlap between one fiber and another means you can run multiple down the same pipe.
- mleonhard 6y agoWhy would they overlap?
- Melkman 6y agoBecause a beam in an open medium always diverges due to wavefront errors and diffraction. A very good laser system might possibly have a divergence of only 1 microradians. For reference a typical laser pointer has a divergence angle of 1 to 2 milliradians. With the 2000km or so between satellites for Starlink the laser "spot" on the receiving satellite with the very good laser will be about 2 meter. Not enough to receive multiple beams on one satellite without overlapping.