Chronicles of light – The secret journey of light inside fiber

How does it really work?

In the previous chapter, we explored the origins of fiber optics, from the first experiments to its global deployment. Now we enter its very core: how does this thread sustain our digital lives?

On the outside, a fiber cable looks simple. But inside, data travels as pulses of light that bounce millions of times per second, guided through a glass core of extraordinary purity. Fiber cables are as thin as a human hair, yet they can transmit at speeds close to 70% of the speed of light.

There are different types depending on the use: single-mode fiber, with an ultra-thin core for long distances, and multimode fiber, for shorter runs. And the efficiency is remarkable: the typical signal loss is just 0.2 dB per kilometer.

Installation is also a feat of precision. A fiber splice is made by fusing the ends with micrometric accuracy, something that modern splicing machines can now perform in under a minute. And when the signal needs to be distributed among several homes, an optical splitter comes into play—a high-precision prism that requires no electricity.

Everything must be flawless: a single speck of dust on a connector can interrupt the connection, which is why ceramic ferrules and isopropyl alcohol are used in every installation.

At the network level, intelligence lies in the architecture. Passive Optical Networks (GPON) require no power in the central-to-home segment and assign time slots to each user to prevent collisions, optimizing transmission.

Conclusion
Fiber turns the invisible into the indispensable—a secret journey of light that transforms the way we live and work.

👉 In the next chapter: Light reaches farther than you imagine.