Hackers extend Toslink audio cables to 143 kilometers, achieve IP data transmission

What just happened? Two hackers have successfully extended the range of Toslink optical audio cables, enabling data transmission over unprecedented distances. While the practical applications may be limited, their efforts could pave the way for future advancements in optical data transmission and networking technologies. Their ingenuity exemplifies the hacker ethos: continuously questioning, exploring, and pushing the limits of what technology can achieve.

Two hackers have challenged the boundaries of optical data transmission, demonstrating that even outdated technology can be repurposed in unexpected ways. At the 38th Chaos Communication Congress (38C3) in Germany, a gathering known for attracting tech enthusiasts and hackers, Benjojo presented his work on extending Toslink traffic far beyond its intended range.

Toslink, an optical fiber connection primarily used for audio transmission, is typically limited to distances of around 10 meters. However, Benjojo’s experiment stretched this distance to an astonishing 143 kilometers.

Building on Benjojo’s work, another hacker, known as Manawyrm, took the concept further. Just one day after Benjojo’s presentation, Manawyrm demonstrated the transmission of IP data over Toslink, effectively creating a basic fiber optic network using audio cables.

Benjojo’s experiment involved a complex setup of data center equipment and various contraptions to achieve the extended range. This included Small Form-factor Pluggable (SFP) ports, Toslink analog-to-digital and digital-to-analog converters, and an oscilloscope.

The long-distance test connected two data centers in London’s Docklands area – Telehouse North and IP House – which are approximately 650 meters apart. The setup also utilized a fiber pair linking the data centers, a CWDM multiplexer to maximize the inter-building fiber connection, and a fiber loop installed at the Telehouse end to enable testing from a single location. Benjojo documented the entire process in a detailed blog post and a YouTube video.

While the speeds achieved were far from competitive with modern networking standards, the proof of concept was significant. Manawyrm’s IP-over-Toslink hack achieved real-world transmission speeds of approximately 1.47 Mb/s (0.18 MB/s), just shy of Toslink’s maximum theoretical limit.

It’s important to note that these experiments don’t herald a revolution in networking technology. The speeds achieved are impractical for modern data transmission needs, with Toslink cables capping out at roughly 1,536 kbit/s (0.19 MB/s).

Nonetheless, these experiments underscore an important principle: with the right modifications, cables designed for specific purposes can be adapted for uses far beyond their original intent. This flexibility in optical data transmission could inspire new approaches to networking in unconventional environments.

While these Toslink experiments are unlikely to replace conventional networking cables, they highlight the innovative potential hidden within seemingly obsolete technology.