Figure 6 | Scientific Reports

Figure 6

From: High-Capacity Free-Space Optical Communications Between a Ground Transmitter and a Ground Receiver via a UAV Using Multiplexing of Multiple Orbital-Angular-Momentum Beams

Figure 6

Bit-error-rate (BER) measurements in flight environment. Each channel transmits a 40-Gbit/s quadrature phase shift keying (QPSK) signal. (a) BERs in a 60-second period and (b) BERs measurements for OAM +3 and −1, when OAM +3 and −1 beams are transmitted. At each transmitted power level, 10 data frames (each has 4096 bits) over ~30-second period are measured. The number at the bottom represents the number of error-free frames during the measurement period at a certain transmitted power level. (c) BER measurements when two OAM beams with different mode spacing are transmitted. The UAV is hovering ~10 m above the ground and ~50 m away from the ground station. (d) BER measurements for OAM +3 when OAM +3 and −1 are transmitted. The UAV is hovering at different distances away from the ground station. FEC: forward-error-correction.

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