Constructing a DIY laser modem

All digital communication in the end comes all the way down to transmitting ones and zeroes, however there are various methods to realize that. One can encode that binary knowledge as modulation in a radio sign or just pulse electrical energy by a wire. However one of the crucial attention-grabbing strategies is optical. Flashing a lightweight is an effective way to transmit knowledge over lengthy distances at excessive pace. Fiber optic cables are the commonest medium, however it’s also attainable to shine gentle by open air. To reveal this idea, Nino Ivanov constructed his personal laser modem.

In idea, this needs to be a really easy machine: simply level a laser at a photoresistor. Pulse the laser in order that it’s on for ones and off for zeroes. Then measure the resistance of the photoresistor to learn these ones and zeroes. However as Ivanov explains, there are two points with this setup. The primary is that photoresistors are sluggish to answer gentle modifications and that severely limits the information transmission pace. The second situation is that it isn’t all the time apparent what’s a zero bit (no gentle) and what’s an absence of information transmission altogether.

Fortunately, pc scientists solved the second situation many a long time in the past. There are a number of transmission protocols that make the most of tips like parity bits and handshakes to make sure synchronicity. Ivanov was in a position to make the most of these methods for half-duplex laser communication together with his customized {hardware} setup. That {hardware} consists of two Arduino Nano boards (one for both sides of the communication), two purple 650nm solid-state laser diodes, and two photoresistors. Ivanov wasn’t in a position to overcome the sluggish transmission time — there isn’t a overcoming the physics of normal photoresistors and Ivanov didn’t need to change to dearer photodetectors.

Because it stands, this laser modem can transmit round 10 bits per second. That’s very sluggish, however this challenge remains to be a enjoyable method to experiment with laser knowledge transmission. If you wish to play with sooner speeds, specialised photodiodes for the telecom business can detect optical indicators modulated at a number of gigahertz — although they’re fairly costly.