Before Bluetooth Ruled: When Devices Talked With Light
Infrared was once the future of mobile data. Decades later, light-based links are finding a new purpose
Today you see someone you’re interested in, and you might go and ask for an Instagram account. Back in the day though, all the cool kids used light to trade numbers.
Powered by a tech that's still in use today yet faded into consumer obscurity thanks to the quick uptake of Bluetooth, it might surprise you to learn that for a long time, infrared provided cable-free, high-speed data communication purely by light exchange. That’s right, we did it via the same thing you use to turn the TV on when you want to watch Netflix.
You didn’t have a passkey. There was no pairing ritual, simply alignment. And there was no radio involved whatsoever. This was how it worked in a world before Bluetooth, yet once the new tech arrived, it was out with the old. The square window that was common on devices would simply disappear.
Most people didn’t even notice that it was gone. 
Light But On The Spectrum
We’ve talked plenty about the electromagnetic spectrum as part of this publication, and it’s worth revisiting that for this so we can understand where exactly infrared sits in the spectrum with regard to RF.
A quick look at the above chart helps us to clear that up pretty quickly. We can see that it sits at the part of the spectrum that is just above the microwave bands and before the visible light section.
In principle, higher frequencies can carry more data. In practice, the limit was the cheap LEDs and photodiodes inside a handset, not the spectrum. The Infrared Data Association (IrDA) standards worked in the near infrared, at roughly 850–900 nm.
The IrDA
The development of standardisation and compatible hardware thanks to the IrDA would help to set the framework for adopting and enabling high-speed data transmissions via light.
The IrDA would do this by assessing infrared transmissions in a similar way that we do standard radio transmitters. This would help establish parameters around communication distance, the bitrates and the types of infrared systems that would be used for the exchange.
The result of this would be a layered protocol architecture that drew on established networking concepts while helping to work within the limitations that came with using infrared.
As we can see from the image below, while it doesn’t have some of the performance characteristics that we’ve come to expect from Bluetooth, it was still capable of high-speed data exchange at reasonably good distances. Not a bad effort with the tech of the era.
Ironically enough, while the concept of standardisation has led to some epic format wars over the years, the adoption of infrared at scale happened pretty quickly, all things considered.
There were reasons for this. The incentive to actually use common specifications like bitrates and hardware already existed, as this laid the groundwork for making it successful. The IrDA had essentially done all the work in creating these technical standards that were ready to implement, meaning that all manufacturers had to do was implement them.
The biggest reason, though, would be demand. With phones, computers and PDAs all going through rapid growth during this timeframe, an organic need would develop as a result of this.
In practical terms, this led to some pretty impressive technology. In 1994, speeds provided performance that made the modems of the time seem positively archaic. 115.2kbps was the starting point, and in a later revision, 4Mbps was configurable by the new standards of the time. Not bad considering we were still plugging into telephone outlets to get the internet.
When the solution is aligned with the problem, sometimes we all win.
Why It Lost The War
Like VHS moving to DVD and DVD moving to streaming, all good things must come to an end. But it’s worth spending some time looking at why exactly that happened.
IR didn’t fail because the technology was bad. In fact, considering the technology of the day, it was pretty good all things considered. It lost out because the practical limitations of using it simply didn’t stand up as modern, radio-based systems evolved.
It was short-range and, to work effectively, both ports needed to be correctly aligned to allow the transmissions to occur. This usually involved moving at least one of the devices, and in a world starting to take phones and laptops basically anywhere, this was an inefficient and painful process.
As the chipsets would undergo rapid iteration through the early 2000s, it simply became a case of Bluetooth winning on convenience, flexibility and, eventually, industry momentum.
One day, infrared was king; the next, it would be unglamorously dethroned. 
Light Isn’t Finished Yet
Despite Bluetooth eventually winning this format war, the utility and development of light-based transmissions hasn’t stopped. In fact, NASA used a prototype laser-based payload called O2O for the recent Artemis II mission around the Moon. This system sent high-resolution imagery and scientific data, but was sensitive to alignment and weather issues. When stable, it provided throughput of up to 260Mbps.
We also regularly use light for our television remotes and industrial systems, and while your remote sends out data at a trickle, infrared is capable of much, much more.
NASA’s O2O system wasn’t an extension of the original IrDA frameworks that helped us to become comfortable with using light as a transmission medium. While IrDA would keep going and give the world Giga-IR at up to 1Gbps, O2O was a modern iteration of previous units like LCRD that had undergone development and optimisation.
O2O was then brought into service, showing how these systems can help enable communications during space travel, helping to prove their worth in supporting spaceflight operations.
The square window disappeared, but the light never did.
Investigator515 explores the RF spectrum, cybersecurity, and the hidden tech behind modern espionage.
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