The main subject of this thesis is to construct underwater optical wireless communication (UOWC). The 450 nm blue-light laser is selected as the light source because of low absorption characteristics in the water. The open seawater is simulated in the 1.5 m length of water tank filled with water conduct in the laboratory. The blue laser light collimated with collimated lens is injected into the water tank using 1.25 data rate and PRBS 31. The mirror placed inside the water tank to prevent the higher optical loss is also used to reflect the light back and forth to obtain a higher transmission distance. At the end of the transmission light, a focus lens is used to focus the light to be received by the Photo-detector. The bit error rate (BER), eye diagram, and optical power were measured to analyze the UOWC system quality. According to the result, the bigger angle of reflection inside the water tank, the higher BER of 2.967 x 10-8 at -13.06 dBm of received optical power will be obtained. The coupling efficiency of the laser was measured by adjusting the laser spot size diameter. The experiment was also measured in the OptiSystem 15.0 software using the same experimental setup. External parameters such as turbulence, higher temperature, lower temperature, and turbidity were conducted to simulate open seawater in the water tank. According to the sea surface temperature contour chart, the seawater temperature is different in every area. As a result, the depth of the transmission channel from the surface will affect the transmission signal quality, making the BER much worse and need higher optical power to transmit. So, varying temperature experiments were conducted at 10°C, 25°C, and 40°C to simulate the lower temperature, room temperature, and higher temperature. The 25°C has better BER than 10°C and 40°C. However, the signal quality in the 10°C still has better BER than 40°C due to the higher molecule density in the lower temperature. The external parameter, such as the seawater experiment, was conducted using the sea salt inside the water tank. A 520 nm green-light laser and 450 nm blue-light laser was compared to the signal quality in the seawater experiment. The blue laser has better signal quality than the green laser; however, the green laser has better optical power loss, about 4.75 dB difference at a 6-meter distance.

The main subject of this thesis is to construct underwater optical wireless communication (UOWC). The 450 nm blue-light laser is selected as the light source because of low absorption characteristics in the water. The open seawater is simulated in the 1.5 m length of water tank filled with water conduct in the laboratory. The blue laser light collimated with collimated lens is injected into the water tank using 1.25 data rate and PRBS 31. The mirror placed inside the water tank to prevent the higher optical loss is also used to reflect the light back and forth to obtain a higher transmission distance. At the end of the transmission light, a focus lens is used to focus the light to be received by the Photo-detector. The bit error rate (BER), eye diagram, and optical power were measured to analyze the UOWC system quality. According to the result, the bigger angle of reflection inside the water tank, the higher BER of 2.967 x 10-8 at -13.06 dBm of received optical power will be obtained. The coupling efficiency of the laser was measured by adjusting the laser spot size diameter. The experiment was also measured in the OptiSystem 15.0 software using the same experimental setup. External parameters such as turbulence, higher temperature, lower temperature, and turbidity were conducted to simulate open seawater in the water tank. According to the sea surface temperature contour chart, the seawater temperature is different in every area. As a result, the depth of the transmission channel from the surface will affect the transmission signal quality, making the BER much worse and need higher optical power to transmit. So, varying temperature experiments were conducted at 10°C, 25°C, and 40°C to simulate the lower temperature, room temperature, and higher temperature. The 25°C has better BER than 10°C and 40°C. However, the signal quality in the 10°C still has better BER than 40°C due to the higher molecule density in the lower temperature. The external parameter, such as the seawater experiment, was conducted using the sea salt inside the water tank. A 520 nm green-light laser and 450 nm blue-light laser was compared to the signal quality in the seawater experiment. The blue laser has better signal quality than the green laser; however, the green laser has better optical power loss, about 4.75 dB difference at a 6-meter distance.

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