What the Tech: Fiber Jumpers Part 1

If you’ve ever been involved in setting up a network, even as an observer, you’ve probably seen fiber of various colors and connectors. And similar to that dryer mysteriously eating socks, if you lay one perfectly coiled jumper on top of another and look away for a moment, it will transform into a horrible tangled bird’s nest.

In this multi-part series, you’ll learn about the different attributes of fiber optic cables and available offerings. Let’s start with the basics.

What is a fiber optic cable? (Yes, we are taking a second to get THIS basic)

It all starts with a thread of glass that carries a signal (1). Around that thread of glass, you have the cladding (2), which traps light in the core. The cladding is surrounded by a protective buffer (3) that keeps out moisture and protects from damage. At this point, additional layers of jacket (4) and strengthening fibers are added to make the fiber more rugged and less prone to damage.

What’s the deal with Single Mode and Multi-Mode?

Now, we suspect you have heard quite a few terms for fiber, including SMF, OS1, and OS2, which are all single-mode fiber. You’ve probably also heard the terms OM1, OM2, OM3, OM4, OM5, MMF, and MM, which are all multi-mode fiber.

Now, let’s break it all down: what is a mode? Quite simply, a mode is a path of light. In a single mode fiber, there’s just one path for a signal to follow down which lets a signal travel a few (or a few thousand ) meter. A multi-mode fiber takes a less focused signal and gathers it down a larger core with different paths the light rays are taking. Since the rays intersect and interfere, the signal goes shorter distance. The higher the bandwidth you’re trying to push over multi-mode fiber, the shorter the distance you can go. unless there was multimode fiber specifically designed to reduce interference…you probably see where this is going…

The different specifications of multimode fiber, OM1 – OM5 have different “modal bandwidths”.

  • The granddaddy of the group, OM1, has a 62.5nm core, with cladding up to 125nm to carry a 100Mb signal up to 2km! Unfortunately, it can only carry a 10G signal about 33 meters and you’re out of luck if you’re trying to pass 40Gb or 100Gb.
  • OM2 has a little bit of a smaller core, requiring a bit more focus, but can carry a 10Gb signal further, up to 82 meters.
  • As multi-mode fiber evolved, it was optimized for laser signals, and now with OM3, OM4, and OM5, 100Gb is possible over the span.

Now Let’s Talk Colors, SO. MANY. COLORS.

There are many different colors of fiber, which can be overwhelming when you are trying to understand what each color indicates. The good news is that there are standards that broadly dictate the colors certain fiber types should use. The bad news is that the standards have different variations for commercial and military specifications. Adding a layer of complexity on top of that is the fact that fiber jumper manufacturers can actually make any jumper, in any color you want. So if you’re setting up a network at Ohio State, you don’t have to hang your legacy on ‘the one who installed all those blue and yellow cables’.

So how do you understand which each color indicates? We have a handy cheat-sheet for you!

That’s all for Part 1 of this 3-part series. You’re well on your way to understanding the variety of jumpers you may encounter. Stay tuned for Part 2 where we will dive into flexibility standards, jacket ratings, and special requirements fiber jumpers need to meet.

In the meantime, if you are ready to talk to an optics expert about your fiber needs, you can start chatting live with them now!