If you are networking over an extended distance, you’re probably using optical fiber. In this video, you’ll learn about multimode and single mode optical fiber technologies.
Many of us are accustomed to using twisted pair copper, especially if we have networks that we use at home or even at our office. But you may occasionally have a need for fiber optic connectivity, and that fiber optic connectivity allows you to send traffic across the network using light. These are often used on very secure networks because it is very difficult to tap into a fiber optic connection without having some type of notification. This is very different than a copper based network which uses RF and is relatively easy to tap and gain information from.
Fiber optics are also used over very long distances because the signal doesn’t degrade as fast as a radio frequency might. So the same signal that we can send over 100 meters of a copper network might be able to be sent over kilometers if you were using fiber optics. And, of course, light is not susceptible to any type of radio frequency interference. And if you’re working in an environment where there is interference, you might want to use fiber optics to avoid any type of problem with your network.
Just as there are many different standards and many different connectors for copper based networks, there are also many different standards and connectors for fiber optic networks as well. So you’ll want to check the configuration and documentation of your devices and make sure that the fiber optics that you’re connecting are using the right type of fiber and the right type of connector.
If we were to deconstruct a fiber optic cable, you would have something very similar to this. On one side of the cable is the light source. This might be an LED or a laser. And on the other side is the receiver. This LED is sending a light through this fiber optic and that consists of a core that is very reflective, and you can see the light bouncing through this core as it receives on the other side. Around the core is a low reflective cladding, and the entire fiber optic run is protected with a buffer coating around the outside.
Here’s the connector that’s at the end of a fiber optic cable. It has a protective ferrule around the outside of the fiber. And if you look very closely at the very middle of this connection, you can just barely make out the core of the fiber that’s in the middle. I’ll highlight it here so that you can really see where that happens to be. Let’s remove that highlight. Now you can start to see that discoloration where the fiber is connected on the end of that cable.
We will generally install one of two different types of fiber optic cables. One is a multi-mode fiber and the other is a single-mode fiber. Multi-mode fiber is commonly used for relatively short range communication. This would be up to around 2 kilometers in distance. And often this uses an inexpensive light source, such as a light emitting diode or an LED.
The core of the fiber optic is relatively large, certainly larger than the wavelength of the light. And because of that, the light itself can use different modes to be able to transmit through that fiber. And you can see the different modes bouncing off the edges of the fiber optic cable itself. Because there are different modes that are being communicated through this fiber, we refer to that as multi-mode fiber.
If we’re communicating over a much longer distance, we may want to use single-mode fiber. Some standards of fiber based ethernet can communicate up to 100 kilometers without a need to regenerate the signal. Because we’re going a longer distance, we may be using a very bright and intense LED or we may be using laser to be able to extend this signal much further. A single-mode fiber also has a smaller core, which can only allow a single mode of light to propagate through the fiber.