Optical Data Transmission - A tribute to

by Martijn Wester

Background

In the late nineteenth century, Alexander Graham Bell and his assistant invented the photo phone. It was the first form of optical communication in history and was used to pass along audio messages by a beam of light of which its movement encoded the signal. Since 1970, when fiber optics were invented, optical data transmission became a worldwide used technique as carrier for e.g. audio and internet data. Data is encoded by light pulses that represent digital data. The modern optical communication uses laser beams as light source and transmits through optical fiber cables.

My project

For this project, I pay a tribute to Optical Data Transmission by visualizing the transfer of data through optics. The project consists of three stages: First, the optical signal is encoded and transmitted; Secondly, the encoded signal is intercepted between sender and receiver to make the signal visible within the medium; And at last, the beam is received by a black box representing the signal receiver.

1) The data that's being transferred is encoded in a visual conceivable manner. This way the displayed signal appeals to the imagination of messages being transferred. A strong laser beam is led via a diverging lens projected through a disk with small letters cut out. Thereby, the beam adopts the shape of the letter, just like Batman's "Bat-Signal". To select the desired letter, a servo motor was attached to the letter wheel. By rotating the disk, the static laser can beam all the letters.

2) In between, the laser beam (with the shape of the letters) is "intercepted" by a rotating flag. This flag is rotating so fast that it looks like the letter is projected in mid air. The flag is powered by a 450W blender motor that is switched by a relay. I reduced speed by using a diode to halve the AC power going to the motor and took off the blades for safety reasons.

3) The data is received at the other end by the black box, which also prevents hazardous beams shining through the exhibition space.

The letters are projected one after another to spell out words. During the rotations of the letter wheel, the laser is temporary turned off. While testing and presenting, the project displayed the words "OPTICAL DATA TRANSMISSION". But of course, every other string could be displayed as well.

For the design of the letter wheel, the letter occurrence frequencies of the English language were used. The most commonly used letters (such as 'A' and 'E') were placed in the middle and the least frequently used letters (such as 'J' and 'Z') were placed to the sides. Funny fact, a similar technique was used in the '80s with the Daisy Wheel Printer, which acted as a wheel like typewriter and it made even more noise while printing than the blender motor of my project. The whole project is interconnected and driven by an Arduino Uno which controls the servo, laser and relay module. It uses a 9V battery to power the Arduino and needs a 230V AC socket to power the motor.

Further improvements

For future improvements, there should be some form of user input to improve 

interaction with the object. Also, the letter disk should be laser cut so the projection of letters would be of better quality. The size of the project could be increased to emphasize that data can be sent over a large distance, and so that letters could be projected larger and thus more clearly.

Source code

The Arduino code used for this project can be found HERE.

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