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I am looking for examples of an optical phase locked loop (OPLL) used (or planned for) free space optical satellite communication.

I have found one, but in the block scheme there is a photodetector (PD). As I know, PS is a part of a receiver.

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  • $\begingroup$ I've made some adjustments to the wording of your question. It's pretty hard to detect the phase of an optical source without some kind of detector, are you really sure you want an OPLL that has no photodetector? Is it really necessary to exclude any photodetector? $\endgroup$
    – uhoh
    Oct 13 at 9:50
  • $\begingroup$ @uhoh photodetector is a part of a receiver, right? laser terminal ( transmitter) has only a laser diode, or did i understand wrong? $\endgroup$ Oct 13 at 12:53
  • $\begingroup$ What about this, and this? $\endgroup$
    – Ng Ph
    Oct 13 at 13:07
  • $\begingroup$ @NgPh a phase locked loop locks one oscillator to another oscillator of a different frequency such that they nonetheless maintain a specific relationship. Frequency synthesizers use PLLs to generate arbitrary frequencies shifted from a stable oscillator, in spaceflight coherent transponders shift the received signal by some rational number (e.g. frequency shift). In the case of the OP's link and both of your links, there are two lasers beating and the beats are picked up by a photodiode. The photodiode's raison d'etre is phase locking. $\endgroup$
    – uhoh
    Oct 13 at 15:51
  • $\begingroup$ @uhoh, thanks. But I don't catch the problem the OP has with OPLL. $\endgroup$
    – Ng Ph
    Oct 13 at 16:59

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