1. The Energy Directors Jeremy Nash, Chris Lamb, Kelsey Whitesell, Josh Chircus

2.  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:  Military communications  Space communications  High bandwidth applications  Advantages:  Fast (high bandwidth)  Lack of interference with other signals  Secure (directed) JEREMY

4.  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. Signal Source Encryption AM Modulator (laser diode) Optics Demodulator Decryption Signal output * For tw0-way communication, this same system will be mirrored and added JEREMY

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

7.  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.  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. ● Class IIIa (continuous wave, 1 to 5 mW) ● Visible Wavelengths (350 – 800 nm) ● Low power/area (typically < 2 mW/cm 2 ) ● 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  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

12.  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. MCU – Comm Motors MCU – Motor MuxDe-Mux Hardware Encoder LaserPhotodiode Transimpedance Amplifier Alignment StatusAlign command Motor control

14.  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. WDMTDM Less coding – combination and synchronization done through hardware Can accommodate modulation at high data rates 1 wavelength per channelSometimes requires optical 3R regeneration (re-amplify, re-shaping, re-timing) Requires more lasers/diodesCombination of signal channels is done within the software before it is even sent to the laser to be transmitted Works better for fiber optics system, since the channels are combined into the fiber upon transmission and demuxed from it after being received Often requires synchronization with start/stop signals, as well as error channels For non fiber system, requires lots of space and optical combination equipment (i.e. prism) to achieve combination and transmission as well as demuxing KELSEY

16. Four Quadrant DetectorCamera systemNeither Small area (requires approximate alignment by eye) Guess and check alignment, but with limited accuracy More expensiveMore complex processingNo additional complexity Tx Laser Beam Beam Splitter Focusing lens Four Quadrant Detector Rx KELSEY

17.  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.  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.  Filtering noise  ADC/DAC  Motor Control for alignment  Encryption/Decryption  Switching between modes of operation  Audio, Raw Data Transfer, and Video options KELSEY

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

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

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

23.  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. TaskPrimarySecondary Optoelectric CircuitryChrisKelsey Mechanical Structure/AlignmentJosh/ChrisJeremy Microcontroller (Communication)JeremyJosh/Chris Microcontroller (Motor Control)KelseyJeremy Board Layout/ConstructionJeremyChris/Kelsey Digital Signal ProcessingJoshKelsey Design DocumentationKelseyChris/Josh/Jeremy JOSH

26. EquipmentPurpose Estimated Price Laser DiodesTransmits encoded information$670 PhotodiodesDetects laser signal$60 MicrocontrollerProcesses signal (see CPU tasks)$50 PCB parts (board, resistors, etc.) Decodes voltage from photodiode and filters noise$50 Motorized Track Actuators Precision adjustment of photodiodes and lasers for automatic alignment $340 4 Quadrant SensorUsed in alignment system$500 LensesUsed in alignment system$100 Beam SplitterUsed in alignment system$90 TripodsUsed for Mounting Transceivers$100 TOTAL$2300 JOSH

27.  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.  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