The Energy Directors

Jeremy Nash, Chris Lamb, Kelsey Whitesell, Josh Chircus

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

Applications: Military communications Space communications High bandwidth applications

Advantages: Fast (high bandwidth) Lack of interference with other signals Secure (directed) JEREM

Y

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

* For tw0-way communication, this same system will be mirrored and

addedJEREMY

JEREMY

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

Need short processing time to avoid long delays in transmission

Need line-of-sightMechanical stabilityLaser beam attenuation constrainedCostManpowerNeed spacing between laser beams

for two-way communication JEREMY

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

● 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

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 troubleshootCHRIS

CHRIS

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

CHRIS

MCU – Comm

MotorsMCU – Motor

Mux De-Mux

Hardware Encoder

Laser Photodiode

Transimpedance Amplifier

Alignment Status

Align comman

d

Motor control

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 measurePower Supply

OTS power supply for each system ▪ AC/DC converter from wall to DC, probably 15V for

rail powerCHRIS

WDM TDM

Less coding – combination and synchronization done through hardware

Can accommodate modulation at high data rates

1 wavelength per channel Sometimes requires optical 3R regeneration (re-amplify, re-shaping, re-timing)

Requires more lasers/diodes Combination 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

Four Quadrant Detector

Camera system Neither

Small area (requires approximate alignment by eye)

Small area (requires approximate alignment by eye)

Guess and check alignment, but with limited accuracy

More expensive More complex processing

No additional complexity

TxLaser Beam

Beam Splitter

Focusing lens

Four Quadrant Detector

Rx

KELSEY

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 KELSE

Y

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

Filtering noiseADC/DACMotor Control for alignmentEncryption/DecryptionSwitching between modes of

operation Audio, Raw Data Transfer, and Video

options KELSEY

Turn on laser

Alignment Procedure

Optics

ADC, Encryption, signal modulated

onto the laser

DAC

Noise filtering

OutputKELSEY

KELSEY

Input Signal

Input Signal with DC Offset

Digital Signal After ADC

Example Sample

Example Transmit-Ready Signal

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

JOSH

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

Task Primary Secondary

Optoelectric Circuitry Chris Kelsey

Mechanical Structure/Alignment

Josh/Chris Jeremy

Microcontroller (Communication)

Jeremy Josh/Chris

Microcontroller (Motor Control)

Kelsey Jeremy

Board Layout/Construction Jeremy Chris/Kelsey

Digital Signal Processing Josh Kelsey

Design Documentation Kelsey Chris/Josh/Jeremy JOSH

JOSH

Equipment Purpose Estimated Price

Laser Diodes Transmits encoded information $670Photodiodes Detects laser signal $60

Microcontroller Processes signal (see CPU tasks) $50PCB 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 Sensor

Used in alignment system $500

Lenses Used in alignment system $100Beam Splitter Used in alignment system $90

Tripods Used for Mounting Transceivers $100TOTAL $2300

JOSH

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

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