Optical Fiber – N10-008 CompTIA Network+ : 1.3

Fiber networking allows a network administrator to send traffic over long distances and through areas of high electromagnetic interference. In this video, you’ll learn about fiber networking and understand the differences between multimode and single-mode fiber communication.

If you’re physically connecting to a network and you’re not using copper, then you’re probably using fiber optics. This is network communication using light to communicate instead of electrical signals. This means there’s no radio frequency that someone could listen in to, to be able to hear what’s happening on the network.

And because we’re communicating with light, we can send the signal over very long distances without having that signal degrade. Fiber optics are also immune to radio frequency interference, which makes them perfect for environments where copper cable couldn’t be used.

Here’s a close up of some fiber optic connectors. You can see where the connector is plugging into the equipment is quite large. It has a large protector around the fiber, itself. The fiber is, actually, inside is very small and very thin. We use fiber optic cables by sending light from one end of the cable to the other. This light is often created using an LED, but it might also use a laser. The light is sent inside of the fiber, finds its way through, and ultimately is received on the other side.

This fiber optic cable is made of many different layers. The internal layer is the core of the fiber optic. This is a highly reflective core, which allows the light to come into the fiber and bounce around the fiber until it makes its way to the other side. Protecting the core is a cladding. The cladding is a low refractive index, which means if any light does leak out into the cladding, it won’t be reflected back into the core.

And on the outside is a protective coating that is usually colored to designate what type of fiber might be on the inside. Here’s a close up of an SC connector. Inside of this SC connector is a fiber optic. You can see in the very middle is a very light colored fiber, and all around that is a protective ferrule. This allows you to plug in this connector and unplug it without damaging the fiber that might be on the inside.

When you’re installing fiber in your facility or connecting two devices with a fiber optic connection, you’re probably using one of two different types of fiber, a multimode fiber and a single-mode fiber. Multimode fiber, usually, is for short-range communication, often up to two kilometers or so. And it often uses an LED or some other inexpensive light source.

We call this multimode fiber because the core of the fiber, itself, is larger than the wavelength of light that is being sent through it. And you’ll find that the light is reflecting through multiple modes as it goes from one side to the other. In this case, you can see an example of different modes as they’re passing through this fiber.

The other type of fiber you might see is single-mode fiber. Single-mode fiber has a smaller core than multimode fiber, and it only allows one mode of light to transmit through that core. We often see single-mode fiber used for very long distances. Some implementations of ethernet can run over single-mode fiber up to 100 kilometers without needing to recreate, or retransmit, that light.

To be able to send a signal over that very long distance, we need a light that’s stronger than an LED, which is why you’ll commonly see laser beams being used to send traffic over single-mode fiber. This is why the cost of single-mode equipment and single-mode fiber, itself, tends to be more expensive than multimode fiber.