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A Pilot-Carrier Coherent LEO-to-Ground Downlink System Using an Optical Injection Phase Lock Loop (OIPLL) Technique

Figure 1

Figure 1
Concept of a coherent LEO-to-Ground downlink system.

Figure 2

Figure 2
Sample configuration of a pilot-carrier coherent LEO-to-Ground downlink system.

Figure 3

Figure 3
Simplified moving model for a LEO-to-Ground downlink.

Figure 4

Figure 4
Doppler frequency shift and rate-of-change versus relative elapsed time.

Figure 5

Figure 5
Experimental system to test coherent link performance under simulated Doppler frequency shift conditions.

Figure 6

Figure 6
How the Master Laser (ML) frequency was deviated.

Figure 7

Figure 7
Fundamental BER performances versus OSNR (no Doppler frequency shift).

Figure 8

Figure 8
Bit error rate versus frequency deviation rate [Formula$\Delta F =$ 206 MHz (1.1ppm)].

Figure 9

Figure 9
Bit error rate versus frequency deviation rate [Formula$\Delta F =$ 1031 MHz (5.4ppm), BER was measured until the receiver unlocked].

Figure 10

Figure 10
Bit error rate versus frequency deviation rate [Formula$\Delta F =$ 2063 MHz (10.7ppm), BER was measured until the receiver unlocked].

Figure 11

Figure 11
BER performances versus frequency deviation rate, Formula$F_R. [\Delta F =$ 10.3GHz (54 ppm), BER was measured until the receiver unlocked].

Figure 12

Figure 12
Waveforms of loop filter input and output in the PLL circuit for different deviation rate of Formula$F_R [\Delta F =$ 2063 MHz (10.7 ppm)].

Figure 13

Figure 13
Spectrum and phase noise performance of original 5 GHz modulation signal.

Figure 14

Figure 14
Spectrum and phase noise performance of coherently detected 5 GHz signal.

Figure 15

Figure 15
Examples of phase noise of coherently detected 5 GHz signal for ML with simulated Doppler frequency shift [Formula$\Delta F = 2.4$ GHz (12.5 ppm)] (left: Formula$F_R = 1$ Hz, middle: Formula$F_R = 10$ Hz, right: Formula$F_R = 100$ Hz)