Working with fiber optics is quite different than with copper cabling. In this video, you’ll learn about optic fiber communication and the differences between multimode and single-mode fiber.
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We connect many of our network devices together with copper twisted pair cabling. But the other option we might have is to use optic fiber communication. This is transmission between these devices using light instead of radio frequency signals.
Because there’s no RF signal, this becomes a bit more difficult to be able to monitor, or tap. We have to think about how we’re going to be able to see the light that’s inside of this optic fiber. Light is able to communicate over a longer distance without degrading. This means we can connect devices that are very far apart with fiber optic that we could never connect using traditional copper cabling.
This also means if we’re on a manufacturing floor or somewhere with a lot of radio frequency interference, we could use optic fiber to avoid dealing with any of that interference on the network. If we were to look at a cross-section of optical fiber, you would see there is a coating along the outside. There’s usually a protective cladding that is just inside of that coating, and then, of course, you have the optic fiber core that’s right in the middle of that cable.
Here’s an example of what that would look like in practice. It’s usually an orange or yellow outside-protected layer. You can see there is a connector on the end, and inside of this– inside of this very small ferrule– is the optic fiber itself.
Here’s a better view of the end of that optic fiber cable. The fiber itself is this very small dot that’s right in the middle. That’s our fiber core. You’ll often see this white ceramic ferrule that’s on the outside of the connector. That’s used to help protect the fiber as you’re connecting it and disconnecting it from the network equipment.
The optic fiber you would put between two devices will either be multimode fiber or single-mode fiber. Multimode fiber means when the light is going into the fiber core itself, that it is going to bounce around into multiple modes. And when it comes out on the other side, you’ll see the light is in those different modes. Multimode fiber’s commonly used for what we call short-range communication– which, in the fiber world, is around 2 kilometers for most combinations of fiber types and equipment if you’re running 100-megabit ethernet networks. If you’re running up to 10 gig, usually you get about 550 meters or so using multimode fiber.
The equipment that you use to send this light from one end to the other over multimode fiber is usually using an inexpensive light source such as an LED to be able to send that signal. Single-mode fiber is generally a bit smaller. When we’re sending light through single-mode fiber, it’s usually coming out on the other end in a single mode.
Using single-mode fiber, we can go very long distances without having to regenerate the light. It’s not unusual to see 80 kilometers of distance being used for a single-mode fiber connection. To be able to extend such a long distance, we need a very strong light source, and it’s not unusual to use lasers to be able to accomplish that. That’s why, whenever you see something that is designed for single-mode fiber connectivity, it tends to be a bit more expensive than using multimode fiber.