Minggu, 05 Februari 2017

Fiber-optic cabling

We strongly recommend you to read the article first to increase knowledge about the Fiber Optic, The Physical Network before proceeding to the next page.

 The Network+ exam talks a lot about fiber-optic cabling. So in this episode, what I want to do is introduce you to fiber-optics, and talk about the many, many connectors that you're going to be seeing on Network+. But before we talk about the connectors, let's first make sure we understand what a fiber-optic cable actually is. So what I have in front of me here is a chunk of fiber-optic cable. And a fiber-optic cable, well, it's hard for me to show you, so let me put up a little graphic so you could see.

So a fiber-optic cable is going to have a fiber optic, which actually carries the light, and it's going to be surrounded by a Cladding, and that's what the light is actually reflecting off of as it stays inside the fiber itself. And then outside of that is a fiber-optic Jacket, that actually just protects the entire setup. So, now that you've seen at a microscopic level what it looks like, there are two types of fiber-optic cable out there. There's Multimode and there is Single-mode. Multimode is designed to propagate light.

So if you were to take a look at a fiber-optic network card, you would see first of all it always has two connectors, always has two connectors, and that fiber-optic network card, if it's Multimode, actually just has a little LED in there that lights up. And the LED lights up and that's what propagates the light down through the cable. Single-mode, I actually have a piece here, Single-mode cable is designed to be used with lasers, so a Single-mode cable, it actually has a much thinner piece of fiber-optic in it, and the Cladding is a little bit tighter, and it's designed to go really, really long distances, and again there'll always be two connectors into your network card, or your switch, or whatever it is, and that's really the only difference there is.

You can't, like, have a switch that's designed for Multimode and just plug Single-mode into it. You have to have the right type of device for the right type of cabling. Okay. So color does come into play a little bit. Multimode is almost always orange, and Single-mode is almost always yellow. You can run into exceptions with this. This aqua is a very special type of Multimode. But for the exam, make sure you recognize these two colors. Okay.

This next thing I need you to take a look at is the fact that, remember I just told you you always use two connectors. So, I'm want to zero in on this guy a little bit. And what I want you to look at is that you could see there are two connectors. It almost looks like a lamp cord. We call this duplex. So most of the time when you're dealing with fiber-optic, you're going to be dealing with duplex cables. Alright. Now for the fun part. Network+ loves to talk about all the different types of connectors.

So we're going to have a little march-through of the many, many types of connectors that have been used over the years in fiber-optic. You'll see all of these connector types on the Network+ exam, but I need to warn you, there's a lot more connectors than this. This is just kind of a, the ones you'll see on the exam. But these are the big ones. Alright. So let's start off with one of the grand-daddy's. This is an ST connector. ST connectors are one of the earliest types of connectors that were ever out there. You'll notice that it looks kind of like a B&C.

You punch it in and you twist it, and then it stays in place. So that is an ST. Notice that an ST is a round connector. Equally old and equally popular are these guys. This is an SC connector. SC connectors are square, and you punch them in, and then you pull them out. So they just go straight in. Now there's another type of connector that looks a whole lot like an ST, but it's not.

So I'm going to put an ST right next to this guy so you compare them. So I want you to look at these two connectors. Now if you look at them really close, I'm going to pull these little protective tabs off. If you look at them real close, they seem to be the same. They're both round, but if you'll notice this one is the ST right here, and that's a, you push it in and twist. This is an FC. The FC screws in, just like for your cable television or something like that.

So, make sure you can appreciate the difference between the ST and FC. And that's just because one twists in, and the other one screws in. All three of these connectors, ST, SC, and FC, are old. Now just 'cause they're old, that doesn't mean that nobody uses them anymore. But one of the challenges we ran into with fiber-optic is that we were always running duplex. It was always two. So people started to get the bright idea of saying, "Why don't we just make one connector that holds two fibers." And that's where we get in a lot of these high-density type connections, and I want to show you these next.

So let's start off with this fellow right here. This is an LC connector. LC connectors are, notice how much smaller it is. This is two connectors, but kind of built into one, although you can still see there's two very clear separate cables. So LC connectors are used a lot, especially when you have a whole bunch of fiber-optic connections together. The last one is MT-RJ. Now MT-RJ is a little bit hard to see, even with this, but there really are two connectors in there.

And if you look at the cable, it doesn't reflect the duplex. But there are. There's two connectors in there. So MT-RJ's are also another real popular type of high density connector. Alright. The last thing I want to talk about is color and connections. When you cut a piece of fiber-optic, you have to go through all this polishing stuff before you put on the ferrule, the connector piece. And there's a term for that. We call it polishing. And over the years there's been a few different types of polishing.

So let's take a quick peek at the three types you're going to see. This first one on the left is a classic regular polish. And they call this a PC connector. The one in the middle is called Ultra PC. Now PC stands for Polish Connector here. And you'll notice that the Ultra is a little bit more rounded than the other one. The rounded-ness actually allows it to propagate light better than the PC Connector.

Now if you really want a great connection, you use an APC, or an Angled Polish Connector. APC's have an angle, and when these two mesh, there is very little little light loss. So we see APC in situations where we want a really, really good connection. And by the way, these two types of connectors, the UPC and APC, are substantially more difficult, and more expensive, than the regular PC-type connector. Now this is just an overview of the different types of fiber-optics you're going to be running out there and seeing today.

Keep in mind that, unlike with a lot of different types of cabling, where I bet a lot of you know about an RJ45, a lot of different types use that. There isn't a perfect correlation there. You can have one type of connection, and you actually create interchanges between those connections based on what you need to use at any given moment. So there's no perfect thing to say, like, "100BaseT only always uses ST." It doesn't. It's got its own set-up and its own rule sets for that.

The important thing I need you to get out of this episode is Multimode uses LED's. Single-mode uses lasers. And make sure, that if you see a picture of any of these connectors, you can identify the type of connector that it is.
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