About 50% faster if the speed of light in fibre is 2c/3.
If you transmitted data straight up 700 miles, and then around the constellation all at 700 miles elevation, and then back down 700 miles, it would need to go 16165 miles (700*2 + 2pi4700/2) @ 187,000 miles per second (1c), or take 0.086 seconds.
This seems like pretty exciting stuff.
https://en.wikipedia.org/wiki/Optical_amplifier
In the end it is probably mostly a matter of how many hops that will determine which is the faster path, the two paths are mostly equal in other respects, I suspect the latency incurred for each hop is roughly the same, assuming they use error correction and re-transmission on the link layers between the satellites.
If it all gets passed through blindly then it will be a bit quicker because there is no decoding step involved but I highly doubt that because it would lead to substantial inefficiencies and loss of capacity (the difference between a switched and hub). Smarter to be a bit slower and to maximize the routing capabilities of the satellites so as to optimize for the scarce resource: inter-satellite bandwidth.
I'm quite curious to see what their antenna setup looks like in practice that's going to be an engineering marvel.
https://en.wikipedia.org/wiki/Laser_communication_in_space
But optical signal amplification is a trick that really only works when you are on a very long run where the signal gets attenuated to the point that you need to boost it. There is no routing option in such a system, it is essentially point-to-point with in-line amplifiers.
So even if they may use laser based comms I don't think optical amplification will be used, the more likely avenue is to decode the optical signal, decide where it has to go next and then fire off another burst.
Alternatively they may use radio waves instead of lasers, I'm not sure what system SpaceX will use for this particular system, given the accuracy required for laser based communications I would assume they will use radio.
https://www.cnet.com/news/spacex-starlink-satellite-broadban...
We were planning on tracking satellites in adjacent orbital planes (which were orbiting in the opposite direction) as well as in-plane. So, yeah, moving parts.
Whenever this topic comes up, I wonder what happened to all the work we did at Motorola in 98-99. There were several hundred engineers in Tempe generating thousands of pages of design documents for over a year. We archived all our work in spring 1999 sand were all shuffled off to other projects.
Presuming a flat surface of 200 X 200, and a random line across half of that, and presuming that satellites only communicate with nearest neighbours you can guesstimate that the extra distance is significant (ignoring other factors).
If they can communicate with more distant satellites then distance could decrease (short cut segments around great circle).
Since the earth is 6,378 km in radius, adding another 1,150 km only makes the circumference about 18% longer.
In fact, the SpaceX proposal looks a lot like the Iridium concept in general, but with thousands of little satellites instead of dozens of larger ones (which probably makes the implementation very different).
http://www.outfittersatellite.com/blog/iridium-next/whats-ir...
Which one to buy !
- Arizona - Hawaii (Military only) - Russia
and then it is routed through the fibre backbone.
With the SpaceX proposal there will be more ground egress points, so it will be able to get closer to the destination before grounding.
SpaceX's 2 test satellites were 400 kg.
The concept 'Size, Weight, and Power' (SWaP) is commonly used when comparing FSO vs. RF systems. Incidentally, FSO systems have lower SWaP than RF systems. They're smaller and lighter payloads, and the system requires less poweR.
Hopefully the telecoms market has changed enough since then (cf Iridium's recent profitability, even while launching a whole new constellation) to make it suddenly viable.
SpaceX's network seems to work the other way around by being designed around fast-moving satellites and complex ground terminals that do the tracking and hand-overs by means of phase array antennas (ie. completely solid-state). In comparison to Inmarsat it is not GEO-bounce and in comparison to Iridium they seem to have some solution for having fully connected mesh of satellites (original Iridium is not fully connected sphere as there isn't even attempt to have link between satellites with oposite orbits)
But at the altitude the satellites (will) operate, that adds about 8ms delay (round trip for satellite immediately above, might be slightly worse). In contrast, the fastest round-trip to a geostationary sat is 233ms. That's a big improvement.