Constructing a DIY laser modem


Constructing a DIY laser modem

Arduino GroupAugust eighth, 2022

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

In principle, this must 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 velocity. The second problem is that it isn’t at all times apparent what’s a zero bit (no gentle) and what’s an absence of information transmission altogether.

Fortunately, laptop scientists solved the second problem many many years 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 capable of 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 all sides of the communication), two pink 650nm solid-state laser diodes, and two photoresistors. Ivanov wasn’t capable of overcome the sluggish transmission time — there is no such thing as a overcoming the physics of ordinary photoresistors and Ivanov didn’t wish to change to costlier photodetectors.

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

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