1. Underwater Optical Communication Semester Project
López Estepa, Pedro
Assistant: Konstantinos Karakasiliotis
Professor: Auke Jan Ijspeert
Final presentation
13 January 2009

2. Underwater Optical Communication - Pedro López Estepa
Summary
Goals
Initial Problems
Wireless Communication Technologies
Designed System
Experiments
Conclusions
Future work
Only general
Underwater Optical Communication - Pedro López Estepa

3. Underwater Optical Communication - Pedro López Estepa
Goals
Project Description
Radio
Blue light
[receiver]
[transmitter]
video and data
accompanying vehicle control
Underwater Optical Communication - Pedro López Estepa

4. Underwater Optical Communication - Pedro López Estepa
Goals
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.
Underwater Optical Communication - Pedro López Estepa

5. Initial Problem Initial Problem
Most of the current underwater optical communication systems can be clasified in two groups in terms of their limitations.
Size Limitations
Power Limitations
We are not included in only one of them!
Optical Communication System
Size Limitations
Power Limitations
Underwater Optical Communication - Pedro López Estepa

6. Wireless Communication Technologies 31.09.2008 – 16.10.2008
High frequency radio wave is highly absorbed in water.
Acoustic communication systems are relatively low bandwidth.
Optical communication with LASER is monidirectional.
Optical communication in Visible Spectrum
Omnidirectional
Bandwidth up to some MHz
Minimal light absorption
in water is usually achieved
for blue light around nm.
Felix Schill , Uwe R. Zimmer , and Jochen Trupf. “Visible Spectrum Optical Communication and Distance Sensing For Uncerwater Applications”. The Australian National University, ACT 0200.
Underwater Optical Communication - Pedro López Estepa

7. Underwater Optical Communication - Pedro López Estepa
Designed System –
System Designed – TX
Water RX
Video signal
Modulation
XOR
LED Driver
LED
CLK
Vdd
GND
Lens
As big as we need the receive platform
Demodulated signal
Vdd
Demodulation
Filtering
Amplification
Photodiode
GND
Underwater Optical Communication - Pedro López Estepa

8. Underwater Optical Communication - Pedro López Estepa
Designed System –
Transmitter
LED Driver
Modulation XOR
Underwater Optical Communication - Pedro López Estepa

9. Underwater Optical Communication - Pedro López Estepa
Designed System –
Transmitter
Underwater Optical Communication - Pedro López Estepa

10. Underwater Optical Communication - Pedro López Estepa
Designed System –
Transmitter
LUXEON III Blue
700 mA - 3W
Underwater Optical Communication - Pedro López Estepa

11. Designed System 16.10.2008 – 20.12.2008 Receiver
Signal Treatment Amplification
The video will be already processed in the FPGA so it will be easy to extract the XOR of the signal and give it as an input to the TX
Filtering
Underwater Optical Communication - Pedro López Estepa

12. Underwater Optical Communication - Pedro López Estepa
Designed System –
Receiver
Underwater Optical Communication - Pedro López Estepa

13. Underwater Optical Communication - Pedro López Estepa
Experiments
Air experiments
Signal is clear in 0,5 we can amplifier
Underwater Optical Communication - Pedro López Estepa

14. Underwater Optical Communication - Pedro López Estepa
Experiments
Air experiments
Underwater Optical Communication - Pedro López Estepa

15. Underwater Optical Communication - Pedro López Estepa
Experiments
Underwater experiments-Hardware Setup
Depth 10 cm
Underwater Optical Communication - Pedro López Estepa

16. Underwater Optical Communication - Pedro López Estepa
Experiments
Underwater experiments
Underwater Optical Communication - Pedro López Estepa

17. Underwater Optical Communication - Pedro López Estepa
Experiments
Underwater experiments
Underwater Optical Communication - Pedro López Estepa

18. Underwater Optical Communication - Pedro López Estepa
Experiments
Underwater experiments
Underwater Optical Communication - Pedro López Estepa

19. Underwater Optical Communication - Pedro López Estepa
Conclusions
The experiments have shown that the range is not decreased while working in underwater
The wide angular coverage of 30º, due to the used lens, doesn’t allow more than 10 cm range around the perpendicular point of movement
To obtain omnidirectional coverage it’s necessary to include an improved lens system in the receiver with several photo diodes to increase the detection range
Underwater Optical Communication - Pedro López Estepa

20. Underwater Optical Communication - Pedro López Estepa
Conclusions
It’s necessary to try to decrease the power consumption after the lenses analysis is finished.
The experiments show that the system has a good response in the range of 500 kHz to 1.50 MHz, which could be increased to 2 MHz by using a better lens system.
According to the initial project requirements
We have completed the electronic hardware fabrication, which means, design and build the physical layer for an underwater communication system.
Even if we didn’t manage to get the transmitter underwater, the setup we used resembles in a good way the final one.
A systematic analysis to determine the most efficient lenses system is not completed.
Underwater Optical Communication - Pedro López Estepa

21. Time Frame Time Completed task Actual task
W. Communication technologies
Communication type selection
Preliminary experiments
Fast optical communications
Trasmitter design
Transmitter build
Receiver design
Receiver build
Air experiments
Underwater experiments
Improvements
Time
Completed task
Actual task
Underwater Optical Communication - Pedro López Estepa

22. Underwater Optical Communication - Pedro López Estepa
Future work
Improvements
Analyze and improve lenses system
High Frequency amplification in receiver
PCB Reduce
Build platform
Enchance harware for underwater emplacenment
Implement Software demodulation …
Underwater Optical Communication - Pedro López Estepa

23. Underwater Optical Communication - Pedro López Estepa
Questions
Underwater Optical Communication - Pedro López Estepa