20-09-2012, 03:25 PM
Underwater Optical Communication
1Underwater Optical.ppt (Size: 1.42 MB / Downloads: 77)
Goals of the Project
Develop a communication system to transmit video between underwater robot and surface platform
Decrease size due to space restrictions.
Find a good combination of communication speed and robustness.
Wireless Communication Technologies
Radio Communication 1
High frequency radio
Attenuation in water is extremely high
Low frequency radio
Attenuation is managable
Maximum BW is limited
Sound Communication 1
For acoustic single transducers the emitter can be considered omnidirectional.
In an acoustical communication system, transmission loss is caused by energy spreading and sound absorption
Energy spreading loss depends only on the propagation distance.
The absorption loss increases with range and frequency. These problems set the limit on the available bandwidth.
Visible Range Optical Communication
Infrared: The light absorption in water
increases towards the red an infrared
part of the espectrum
Blue Light: Minimal light absorption
in water is usually achieved for blue light
around 400-450 nm.
Fast optical communication
AM Optical Transmission
MHz-range frequency response
The driving method is not capable of fully-driving the LED at the highest frequencies
FM Optical Transmission
FM modulation was chosen over AM modulation since it was viewed as being more resistant to fading and variations in the signal amplitude.
This worked fine even though the duty cycle of the pulses was extremely short (4ns at 100kHz).
1Underwater Optical.ppt (Size: 1.42 MB / Downloads: 77)
Goals of the Project
Develop a communication system to transmit video between underwater robot and surface platform
Decrease size due to space restrictions.
Find a good combination of communication speed and robustness.
Wireless Communication Technologies
Radio Communication 1
High frequency radio
Attenuation in water is extremely high
Low frequency radio
Attenuation is managable
Maximum BW is limited
Sound Communication 1
For acoustic single transducers the emitter can be considered omnidirectional.
In an acoustical communication system, transmission loss is caused by energy spreading and sound absorption
Energy spreading loss depends only on the propagation distance.
The absorption loss increases with range and frequency. These problems set the limit on the available bandwidth.
Visible Range Optical Communication
Infrared: The light absorption in water
increases towards the red an infrared
part of the espectrum
Blue Light: Minimal light absorption
in water is usually achieved for blue light
around 400-450 nm.
Fast optical communication
AM Optical Transmission
MHz-range frequency response
The driving method is not capable of fully-driving the LED at the highest frequencies
FM Optical Transmission
FM modulation was chosen over AM modulation since it was viewed as being more resistant to fading and variations in the signal amplitude.
This worked fine even though the duty cycle of the pulses was extremely short (4ns at 100kHz).