There are many different connectors used on fiber and copper network links. In this video, you’ll learn about the various kinds of connectors that are used on common networking equipment.
One popular fiber optic connector is the LC or local connector. This connector has two different fibers inside of it, usually this is a send and receive. And you can see that it plugs in with these locking connectors at the top.
To be able to remove this from a connector, you have to push down and then you’re able to remove it from the interface. These are relatively small connectors. And because of that, they’ve become pretty popular on our most recent routers and switches, because you can fit so many of them into such a relatively small space.
Some connectors that are slightly larger than the LC are the ST connectors, the straight tip connectors. And this is a connector type that’s been around for quite some time. These connectors also lock in place, but they use bayonet connectors. So you plug them in and slightly twist them, and they’re locked in place. You have to untwist and then pull to be able to remove an ST connector from a device.
Subscriber connectors are these square connectors. In fact, sometimes you’ll hear the subscriber connector or SC described as a square connector, because they do have this relatively square face. When you’re plugging in SC connectors, they might be connected individually as separate fibers, or you may be plugging into fibers simultaneously. These lock into place with a unique locking mechanism that once you push it in, is locked in place. You have to pull back on the spring-loaded connector around the fiber to release it from that interface.
And the last type of fiber connector we need to know for the Network+ exam is the MT-RJ. This is the mechanical transfer registered jack. You can see that it is a very small connector. It does have two tiny fiber connectors at the end of it. And of the other connectors, this one probably is the one with the smallest amount of real estate that it takes on a switch or router.
If a manufacturer is looking to fit the maximum number of fiber connectors into the smallest available space, then they’re probably going to use this MT-RJ connector. Very similar to the LC connector, the MT-RJ has a locking mechanism at the top. And when you want to remove it from the interface, you push down so that lock disengages, and then you can remove it from the interface.
One of the challenges with fiber optics is that we’re dealing with light as a transfer mechanism. And so there’s all sorts of physics that go into the idea of making sure the optimal amount of light is getting from the beginning to the very end of the connection. One very important statistic is the return loss. This is how much light is reflected back to the source and thereby creating an inefficiency in the amount of light that you’re able to send to the other side.
To be able to minimize the amount of return loss, we have different connectors that we might use. One of these connector types is a UPC connector or an ultra-polished connector where the ferrules are connecting together at a 0-degree angle. They are facing each other directly. This type of connector tends to have a high return loss.
One type of connector that has a lower return loss is an APC or angled polished connector, because there is a very slight 8-degree angle between the connector types. And when you’re using this type, instead of having all of that light reflected directly back to the source, it is reflected back at an angle away from the source.
Here’s a cross section of a UPC connector. You can see that these two sides are connecting right in the middle at 0 degrees. This means that the light going out and hitting that connection is reflecting back a little bit of that light back to the original station, creating the high return loss. This is different than an APC connector where there’s a slight 8-degree angle where those two fibers meet. This means that the light that is moving down the fiber is hitting that angle. And some of that light is being reflected back, but it’s being reflected back at an angle, giving you much less of a return loss than something that is a UPC connection.
Now that we looked at fiber connectors, let’s have a look at some copper connections. One that’s very common with voice communication is an RJ11 connector. That RJ stands for registered jack type 11. This is a sixth-position connector. But only two of the conductors are actually inside of this cable. Sometimes you’ll see this written as a 6P2C.
You can see all six of these positions in this image, but you can see that only two of them have conductors inside of them. If you run into a cable or a connector that has the six positions, but four of those conductors are in use, we commonly also refer to this as an RJ11, but technically it’s an RJ14 because of that slight difference. You’ll commonly see these connectors used for things like DSL connections or analog telephone connections.
We commonly use a slightly larger connector for our ethernet connections. This is an RJ45 connector or register jack type 45. In the case of an RJ45, there are eight positions. And all eight conductors are used for these ethernet connections. Sometimes it’s difficult to differentiate between an RJ11 and an RJ45, because they are constructed very similarly, but the size of the connectors is quite different.
Here’s a view of both RJ11 and RJ45 connectors on the same device. You can see the RJ11 is slightly smaller than the RJ45. And sometimes, when you’re troubleshooting, you’ll find that people might plug in an RJ11 cable into an RJ45 connector, which obviously is not going to work properly. Most of those times you can easily unplug from the RJ45, plug into the correct RJ11, and the user will be up and running.
If you’re using a cable modem, then you’re probably connecting using a coax cable from the cable company. This coaxial connector is called an F-connector. This is the type of connector you will find on a cable modem. And it follows the standards associated with DOCSIS or Data Over Cable Service Interface Specification. Many times this is an RG-6 type of coax cable. And the connector at the end is most commonly threaded to make sure that once that cable is inserted that it can’t easily be removed from that connection.
Here’s a close up of the threaded F-connector on the cable modem and the F-connection that’s on the cable itself. You would insert this cable and twist it until it’s tight, which will help keep it in that connection and won’t allow it to easily pull out of that cable modem.