In the world of copper cables we looked at earlier (power, telephone, UTP network), things are simple. If a wire is accidentally cut, you take a cutter, strip some of the copper, twist it with your fingers, put on some electrical tape or a "clamp" and you're done.
In the world of FTTH (Fiber to the Home), however, we are not dealing with metal. We are dealing with light traveling through glass. If the fiber is cut (or if the cable from the street needs to be joined to the cable in your apartment), you can't tape it. This is where one of the most impressive and "surgical" procedures of modern engineering enters: Fusion Splicing.
Let's see exactly how we manage to join two strands of glass without losing a single photon, and why this is a no-go DIY.
To understand the challenge, you need to understand the anatomy of the fiber. An optical fiber (Singlemode) coming to your home has an outer diameter of 125 micrometers (μm) – about the size of a human hair.
But, light does not travel through the entire thickness. It only travels to the central core (Core), which is only 9 micrometers (µm) in diameter! For light (the internet) to pass from one wire to the other, these two invisible cores must align with a deviation of less than one nanometer. If the joint goes even slightly wrong, the light will "hit" the walls, reflect back and the connection will drop (Attenuation / Loss).
The work of alignment cannot be done by a human hand. That's why we use Fusion Splicer.
It is a portable, ultra-high precision robotic machine. It has built-in microscopes (X and Y axis cameras) that view the fiber, and micro-motors that move the glass. A professional Splicer (such as the Japanese Fujikura or Sumitomo ones) costs from €3,000 to €10,000. Even cheap Chinese copies start at €800. It is by far the most expensive tool in a telecom technician's bag.
The joining of the fibers takes place in 4 strict steps:
On YouTube you will see various videos of "Mechanical Splices", that is, cheap plastic clips that promise to join the fiber without the expensive Splicer machine. If you are thinking of making it your home, stop now. The reasons are not only technical, but mainly safety and health reasons:
When the technician cuts the fiber (Cleaving), glass scraps 1-2 millimeters long are created. These fragments are practically invisible and sharp as a scalpel. If such a fragment lands on your carpet and you step on it, it will pierce your skin, enter the blood and not show up on x-rays to be removed. If it gets in the eye or is swallowed (e.g. by a crawling child or pet), the consequences are tragic. Professionals have special, sealed cans for their disposal.
The light sent by the provider through the fiber operates in the Infrared region, usually at 1310nm or 1550nm. This light is completely invisible to the human eye. If you cut the cable and look at the end of it to see "if internet is coming", you won't see anything light up, but the provider's powerful Laser will burn your retina at that moment, causing permanent, irreversible blindness without you even feeling pain.
DIYers' mechanical joints (without thermal bonding) have huge signal losses, collect dust and usually fall apart after a few months due to contractions, throwing the speed into the tartar.
Optical fiber is a marvel of physics, but its manipulation requires laboratory conditions. Fusion Splicing is the art of melting and joining two strands of glass at the micrometer level. Due to the exorbitant cost of the equipment and the extreme health risks (shards of glass and invisible Lasers), this is a job that belongs strictly and exclusively to the providers' certified technicians. All you have to do is provide them with the clean pipes we saw in the previous chapter!
Next Step: Now that we understand how glass is put together, it's time to look at its types. There are two big "worlds" in optical fibers: Singlemode and Multimode. Which of the two does the internet bring to your home and which is a trap?
Moving on to the guide: Singlemode vs. Multimode Optical Fibers: What is their difference and which is used exclusively in residential / building installations.
Return to category.
Go to categoryReturn to the central guide.
Go to guide
