[time-nuts] laser as clock source

[Hal Murray]

jimlux at earthlink.net said:
> Well, in deep space optical comm, we send many photons with a laser, and  we
> use pulse position modulation at the receiver detecting single  photons (or
> "few photons"), by which we can send "many bits/photon"  (e.g. if you have
> 256 possible time slots in which the photon can  arrive, you have 8 bits/
> photon) 

Neat.  Could you please say a bit more.

What sort of distance?  Bandwidth?  Error rate?

How big is the laser and telescope?   What sort of optics on the receiver?  
How hard is it to point the receiver in the right direction?  How hard is it 
to point the transmitter telescope?  ...

How does the receiver get timing?


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