Open-Air Laser Communication

Project Type: Lasers and Optics

Project Information

Project Description:

The task is to design and build a line-of-sight laser communication system that will transmit and receive voice and music over a distance of 1000 meters.  The transmitter will use a green (532 nm) laser diode and current amplifier to send an intensity-modulated beam to the receiver.  The light will be gathered by a large parabolic mirror and focused onto a small silicon photodiode where the modulated light is converted back into an electrical signal.  Unwanted optical noise will be reduced by using a laser line filter and light-tight box to house the photodiode.  The system is battery powered for use in the field.  For safety, the laser’s average optical power will not exceed 5 mW.

Level of Difficulty: Medium

Keywords/Technologies:

diode laser, operational amplifier, line filter, parabolic reflector, PIN diode, amplitude modulation, bias point, wavelength, bandwidth

References:

“Make Your Own Laser Communication System,” by All About Circuits, Maker.IO, 2016 https://www.digikey.com/en/maker/projects/019e23c629644c86a0a077caa228b4d2

Laser Communication Relay Demonstration, NASA Goddard Media Studios, October 31, 2013 https://svs.gsfc.nasa.gov/11357

Team Roles

Electrical Engineer (2) – Electrical Engineers on the project will design the analog green-laser transmitter and photodiode receiver.  The transmitter will have the bandwidth to support voice and music transmissions.  The receiver will have the same bandwidth capability plus amplification to speakers so that the message can be heard by a group.  Audio filters may be required for sound quality.

Mechanical Engineer (2) – Mechanical Engineers are responsible for the system’s portable mounting and pointing hardware.  The transmitter and receiver will be supported by adjustable tripods that collapse for easy carry.  Either transmitter or receiver may be carried into the field and set up by a single person.

Optical Engineer (2) – Optical Engineers are responsible for sending a well-collimated beam to the receiver.  At the receiver, the OEs will use a parabolic mirror and laser line filter to collect the laser light and focus it down to a small photodiode with no stray light contamination.

Computer Scientist (2) – After an analog system is up and running, the Computer Scientists are responsible for converting the optical communication link from analog to digital.  The link will act as a 1-km long serial port.  Message quality will be compared to analog signals.

Designer (2) – The Designers will work closely with the Engineers to manufacture a system that is portable and safe to operate around untrained personnel.  The transmitter and receiver must each fit in a backpack for one-person transport.  Electronic and sensitive optical components must be mounted in water-tight enclosures to protect them from harsh operating conditions (fog, rain, snow)

Journalist (1) – The Journalist documents the project’s progress on the website, communicates with the local media, and is responsible for a final report to the principal sponsors and Power Mountain Engineering.  The Journalist also works closely with the Multimedia Artist to provide video and graphic art displays for demonstrations that explain the project to the public.  The whole project is your project.

Multimedia Artist (1) – The Artist also documents the project’s progress on the website and works with the Journalist to maintain the project’s presence on social media.  Additionally, the Artist designs and organizes all public relations events to assure spectator safety and to enhance the community’s awareness of science and technology.  The whole project is your project.

Business Manager (1) – The Business Manager is responsible for reporting the project’s progress against a predetermined schedule, determines critical path items to completion, and tracks project spending to assure that costs remain within a fixed budget.  The Manager works with all team members to identify problems early and resolve them quickly.  The whole project is your project.

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