A Secure, Multi-Channel Laser Communication System for Operation in High Noise Environments The LaserShark

1. The Energy Directors Jeremy Nash, Chris Lamb, Kelsey Whitesell, Josh Chircus A Secure, Multi-Channel Laser Communication System for Operation in High Noise Environments The LaserShark

2. Project Objectives • Create a free-space laser communication system capable of: • Functioning in a high noise environment • Encryption for secure transmission • Transmitting multiple signals simultaneously • Long-range, line-of-sight communication JEREMY

3. Applications and Advantages • Applications: • Military communications • Space communications • High bandwidth applications • Advantages: • Fast (high bandwidth) • Lack of interference with other signals • Secure (directed) JEREMY

4. Goals • Low Priority • Transmits digital audio and plays back audio successfully (one-way) over 1 ft • Performs well in high noise environment • Encryption • Medium • Time division multiplexing (TDM) • 2 way communication • Alignment feedback system at beginning of/during transmission • Long distance transmission (>10 ft) • High • Video transmission and raw data (digital) • Continuous automatic alignment including beam splitter/Quad-Detector feedback JEREMY

5. Functional Outline of Approach * For tw0-way communication, this same system will be mirrored and added JEREMY

6. Packaged Transceiver Units Side view Laser and photodiode on optical mounts clamp Back view Diagram of Design clamp power ground Bracket and motorized stages front Two-way communication Inside the package Alignment system Tripods Transceiver Unit Detail PCB JEREMY

7. Constraints • Need short processing time to avoid long delays in transmission • Need line-of-sight • Mechanical stability • Laser beam attenuation constrained • Cost • Manpower • Need spacing between laser beams for two-way communication JEREMY

8. Safety and Environmental Impact • Environmental impact • Hard to dispose of parts • Beam doesn’t interfere with the environment because it’s directed energy at optical frequency (no FCC regulation yet) • Safety • Laser can damage eye • Low power laser (Class IIIa) CHRIS

9. Laser Safety • Class IIIa (continuous wave, 1 to 5 mW) • Visible Wavelengths (350 – 800 nm) • Low power/area (typically < 2 mW/cm2) • Corneal damage only (safe viewing time is 0.25 seconds) • Damage includes non-permanent retinal damage if viewed for 1 or 2 seconds, permanent retinal damage if viewed longer than a few seconds • Translated: Don't look into the laser (duh). CHRIS

10. Manufacturability and Sustainability • Manufacturability • Photodiode needs to be accurate • Motors need to be high resolution • Sustainability • Low power consumption • Resilient parts and reliable processors • Easy to fix because its relatively straight-forward to troubleshoot CHRIS

11. Details of Design CHRIS

12. Details of Design • Signal Source(s): one or more current/voltage signal source(s), for example the output from an iPod • Analog to Digital Converter: Allows for encryption of analog signal • Encryption: performed by encoding data from signal source with a standard encryption algorithm, implemented on a MCU • Laser diode: output depends on current input, so the laser diode itself is an AM modulator • Optics: Optical systems could include the following: • Neutral density filters and mirrors to simulate longer distances in the lab • Spatial filters and collimating lenses to improve signal quality • Demodulator: at the receiver; this will consist of a photodiode to detect the optical signal and turn it into an electrical signal • Decryption: also implemented on an MCU • Digital to Analog: Allows for playback of decrypted analog signal • Output: signal could be output to a speaker for playing a sound, to a computer to display the received signal, etc. CHRIS

13. Block Diagram of Tranceivers Motor control Motors MCU – Motor Align command Alignment Status Mux De-Mux MCU – Comm Hardware Encoder Transimpedance Amplifier Laser Photodiode CHRIS

14. Power • Power Requirements • Laser: 5 V DC/3 A = 15W • MCU on PCB (x2 per transceiver = 4 total): 5 V DC /1.6 A= 8W • Transimpedance amplifier: currently unknown, will measure • Power Supply • OTS power supply for each system • AC/DC converter from wall to DC, probably 15V for rail power CHRIS

15. Wavelength Division Multiplexing versus Time Division Multiplexing KELSEY

16. Four-quadrant system versus Camera System Beam Splitter Laser Beam Rx Tx Focusing lens KELSEY Four Quadrant Detector

17. Photodiodes (Rx) and Laser Diodes (Tx) • Photodiodes-Thorlabs FDS100 • 350 - 1100 nm • High Responsivity in red (635 nm) range • Fast recovery time (35MHz) • Laser Diodes from Edmund Optics • Built-in safety circuitry • Maintains functionality • Prevents back-current • Provides some temperature control • Max 5mW power (class 3a laser) • 635 nm (red) center wavelength • Narrow bandwidth (± 10 nm) • Low current draw • Modulation bandwidth 6Hz-2MHz KELSEY

18. Additional Optical Components • Components to simulate additional distance due to limited lab space • Neutral Density (ND) filters for attenuation • Mirrors • Beam Splitter • Focusing lens • If necessary: lenses for improving quality and/or collimating KELSEY

19. Main CPU Functions/Requirements for High Goals • Filtering noise • ADC/DAC • Motor Control for alignment • Encryption/Decryption • Switching between modes of operation • Audio, Raw Data Transfer, and Video options KELSEY

20. Software Flow Turn on laser Alignment Procedure ADC, Encryption, signal modulated onto the laser Optics DAC Noise filtering KELSEY Output

21. Encoding Digital Signal After ADC Input Signal Example Sample Input Signal with DC Offset Example Transmit-Ready Signal KELSEY

22. Processor • MSP430 xxx series • 8-16MHz • ADC/DAC options • Up to 64 GPIO options • Up to 120kB of RAM • Ultra-low power usage JOSH

23. Mechanical Components • Motorized track actuators for lateral translations • Stepper Motor for tilt adjustment • Plastic packaging for transceiver circuits and components • Stands (possibly tripod) • Clamps and Brackets for securing transceiver units • Various Mounts (can be machined, if need be) JOSH

24. Division of Labor JOSH

25. Schedule JOSH

26. Budget JOSH

27. Funding and Grants • DEPS Funding (Granted) • $2200 all purpose funding • Requires a report upon completion • UROP Funding (Pending) • Up to $1000 funding • Requires a report upon completion • These grants should be enough to fund our project. JOSH

28. Potential Schedule and Budget Related Issues • Failure to implement automated alignment due to cost of motors or unforeseen mechanical issues. • Mitigate by finding low-cost motors and seeking advice from mechanical engineer. • Failure to implement video transmission due to insufficient time. • Budget time effectively and seek advice for video transmission requirements. • If a rock gets into the system: • There is no possible mitigation – all members perform Hari Kari. • Chris loses energy – not possible. JOSH

29. Questions?