1. Short-Range Digital Laser Communication System

2. Team Members
Timothy Vitou, team leader (laser safety, Helmet receiver circuit and diode array)
Cory Yambor (transmitter circuit)
Steven Young (receiver circuit cellphone, assisted with transmitter circuit design)
Chase Novack (cell phone software demodulation and playback)

3. Background RF communication is very common, but can have limitations
Wireless signals can be intercepted and run into interference
The laser communication system cannot be remotely hacked and is very secure

4. Advantages No remote hacking or jamming Versatile
Low Power (No more than 200 mW)
Varying wavelengths of light may be used based on needs of user
Has potential in tactical applications
High speed

5. Disadvantages Not meant for long distances Potential hazards of lasers
Aiming can be difficult at longer ranges
Prone to poor environmental conditions
Performance affected by weather
Line of sight requirement

6. How it works A microphone picks up a person’s voice
Analog signal is converted into a digital signal
Modulates a laser using Pulse Coded Modulation
Photodetectors send the signal to a DAC for the user to hear it
Our project does this using a helmet and a cell phone
Transmitter
Receiver
Cellphone
with
Android
Application

7. Transmitter Flow Diagram
Amplifier
Buffer
A/D Conversion
Microphone
Pulse Coded Modulation
Digital Laser Transmission

8. Transmitter components
LM386
OPA2134

9. Transmitter components
PCM4201
DIT4096

11. Receiver Flow Diagram Receiver Laser Reception D/A Conversion
Signal Amplification
D/A Conversion
Audio Output

12. Receiver Array of phototransistors Comparator circuit (Demodulation)
Cell phone software
Helmet’s TLV320DAC23 (DAC)
Serial to USB FT312 for cell phone
Again be technical. Describe how the receiver can take digital signals and convert them.

13. FT312
Receiver Components
TLV320DAC23

14. Software (Overall)
The cell phone module is developed for the Android OS platform
Targets version 2.3 and above
Makes use of the AudioRecord, AudioTrack, and MediaPlayer Application Programming Interfaces
Saves and plays back voice data as MP3 files (utilizing the free LAME encoder library)

15. Software (Transmitter Module)
Built-in microphone takes in user’s voice
The signal is passed to AudioRecord, and then AudioTrack which record and playback the audio, respectively
The played back audio is sent via the auxiliary jack to the transmitter circuitry
Is tested and verified working

16. Software (Receiver Module)
Receives modulated digital voice signal from the receiver circuitry via serial to USB cable
Converts the received signal back to analog, saves it (via AudioRecord), then plays it back (with AudioTrack and MediaPlayer APIs) via the phone’s speaker
Code is in development, and waiting on the completion of the hardware and the arrival of the serial to USB cable and accompanying IC

17. Remaining Work System integration testing
Cell phone integration testing
Timing for A/D and D/A (8 - 96kHz)

18. Laser Safety
The biggest concern for this project is the potential level of danger
The laser is a class 3A
When used improperly, the system can cause eye injury
Proper training must be conducted to avoid misuse

19. Calculations (at 50 feet)
Laser Wavelength
MPE (8KHz)
MPE(96KHz)
Visible Red (650nm)
1.111x10-4 W/m2
3.943x10-5 W/m2
Infrared (980nm)
W/m2
2.1144x10-5 W/m2
Infrared (1550nm)
W/m2
W/m2

20. Potential Developments
Open to modifications and other applications
Possible use for situations with poor radio reception
Air to ground communications

21. Conclusion
Digital laser communication offers a strategic advantage for law enforcement/military
Concept can be applied over a wide range of applications
Over time, the system can be made to be more secure and efficient
Wrap it up! Basically go full circle and summarize what the heck you just talked about.

22. Questions?