Fig. 2. Intensity distribution of a laser beam after transmitting through (a) 30 m and (b) 60 m in clean sea water.
Fig. 3. Experimental setup of the proposed RGB LD-based WDM UWOC system. Inset: (a) the transmitter module, (b) the receiver module, and (c) the water tank.
Fig. 4. Schematic diagram of the working principle of a DM-DPSSL.
Fig. 5. Possible application scenario of the proposed underwater Fi-Wi system.
Fig. 6. Leaky POF-based distributed UWOC system. Inset: a “ZJU” symbol generated by a leaky POF originally used for decorative applications.
Fig. 7. (a) Experiment setup of the 46 m UWOC system using an MPPC receiver. (b) The 46 m PVC tube filled with tap water to simulate a 46 m underwater channel.
Fig. 8. Transmitting optical power for different
Fig. 9. Histogram of incident photon number in each pulse slot for different
Fig. 10. (a) Waveform and (b) spectrum of the captured 32-QAM OFDM signal with an ROP of −19.9 dBm.
Fig. 11. Constellations after 2 m underwater transmission: (a) 256-QAM with bit loading, (b) 16-QAM with bit loading, (c) 256-QAM without bit loading.
Fig. 12. Experimental setup for the proposed MIMO-OFDM-based UWOC system. The inset shows the schematic arrangement of transmitters (TXs) and receivers (RXs).
Fig. 13. Experimental setup for verifying information leakage using an MPPC placed aside the light beam.
Fig. 14. Experimental setup of the air–water laser communication scheme. Inset: (a) the transmitter module, (b) the receiver module, and (c) the water tank.
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