Instructor: The next type of cable we need to talk
about is fiber optic cables.
Now fiber optic cables are going to use light
from an LED, a light emitting diode,
or a laser to transmit information
through a thin piece of glass fiber.
Now fiber optic cables are great
because they're immune to electromagnetic interference,
or EMI, because there's no electricity involved
in the data transmission as it's going down that cable.
Also, because we're using light instead of electricity,
our signal can go an extremely long distance
without much attenuation or signal loss.
Whereas our copper cables, specifically CAT3
through CAT7 could only go about 100 meters.
Fiber optic cables can go hundreds
of meters or even hundreds of miles.
After all, we have some really long fiber optic cables
that are sitting on the ocean floor
between the United States and Europe.
And that is a huge distance all the way across the Atlantic.
Now, this is one of the biggest benefits
of fiber optic cables.
It can cover an expansive range and longer distances.
In addition to that, we can turn the light on and off
very quickly adding to higher bandwidth applications
by using fiber.
If you remember from our copper media discussions,
we were talking in terms of 10 megabits per second,
100 megabits per second, one gigabit per second,
10 gigabits per second, and things like that.
But now that we've moved on to fiber, we can start talking
about things in the terabits per second range.
In fact, all the way back in 2012,
the Japanese telecommunications company NTT
was able to send data at one petabit per second.
Now that is really, really fast.
And so fiber is starting to be used
in a lot of extremely fast networks.
And it's usually not the fiber cable that becomes
your limitation in the network anymore.
Instead, it's your other networking equipment,
things like your switches and your routers
and your end user devices, they just can't keep up.
And so for this reason, most business class networks
are still going to use fiber around 10 gigabits per second
because of those switches and routers.
But this is more of a cost benefit decision
than a technical limitation of the fiber cables themself.
So, if fiber is so great with a huge expansive range
and super high speeds,
there's got to be some drawbacks, right?
Why isn't everyone using fiber?
Well, we really do have two main drawbacks of fiber.
First, fiber is expensive.
Now the price of fiber continues to drop
and it has year over year,
but it's still much more expensive than a copper network.
For this reason, most businesses only use fiber
to connect backbones of their networks
to their red switches or they're going to use fiber
if they need to cover a large distance
that they can't cover with copper.
Second, fiber is more difficult to work with than copper.
In fact, when I teach in the classroom,
I teach my students how to build
their own Cat 5e cables.
Now for less than $10, I can get each student a crimper,
a set of connectors, and a cable tester
and they can take it home with them and they can do it
in about 10 minutes to learn how to build their own cables.
It's really easy.
Now, fiber on the other hand is much more difficult
to work with and it requires special tools
and training to learn how to make those fiber cables
or to repair broken fiber cables.
In my experience, it costs about five to 10 times more
to run a fiber cable than it does to run a copper cable
inside an office building or between office buildings.
Now, even with the drawbacks and expense
and difficulty of working with fiber optic cables,
fiber optics definitely have a place
in most enterprise networks.
And so we need to spend some time going
over the different types
of fiber optic cables that you may come across.
First, we need to categorize our fiber optic cables
and we do this as either single mode fibers
or multimode fibers.
Now single mode fibers or SMF is a type
of fiber optic cable that carries a single beam
of light directly from one end of the cable
to the other end of the cable.
To achieve this, a single mode fiber has a smaller
and thinner core than does a multi-mode fiber.
Now single mode fiber is used
for long distance communications
due to its smaller core size
of 8.3 to 10 microns in diameter.
This smaller core size allows
for a more precise signal transmission
over a longer distance because it forces the light to travel
along a single path down the center
of that cable without being dispersed around.
Now, if you see workers with a large roll
of fiber optic cable in your neighborhood,
this is usually going to be a single mode fiber
and they're going to be able to cover a long distance
from their internet service providers facility all the way
into your neighborhood.
And that's why they do it.
The second type of fiber we have is known
as multimode fiber or MMF.
Now multimode fiber is a type
of fiber optic cable that carries a beam of light
as its data transmission media,
just like a single mode fiber,
but it uses a thicker core size.
Now multimode fiber cores are
between 50 to 100 microns in diameter.
This makes them about six to 10 times larger
than a single mode fiber's core.
Now 50 to a 100 microns might sound pretty small
and it is relatively, I mean an average human hair
is only about 70 microns in diameter.
This is still an increased core size
over the size of a single mode fiber.
And it allows light to start bouncing around and refracting
as it's traveling down the cable.
Due to this, multimode fiber is usually going to be used
in shorter distances, up to around two kilometers
or less in size.
And that's about a mile in distance.
Now multimode fibers are commonly used in the same place
you're going to normally use a copper patch cable.
For example, if you're going to be using a multimode fiber
to connect a router to a switch
or a switch to a switch or switches to servers,
any place you'd normally use a patch cable
or even a cable run between your patch cable
and your wall jack, could be a place you use
a multimode fiber instead.
For the exam, you do not need to memorize
the exact size of the cores
for single mode or multimode fibers.
They're not going to ask you that.
Instead, you need to remember the multimode fibers
are going to have a larger core size,
therefore they cannot cover longer distances
the way a single mode fiber can.
If you need to pick out a cable to cover a longer distance,
you want to make sure you're selecting a single mode fiber.
Remember, single mode fibers have a much smaller core size
and therefore, light can only travel in one direction
down that cable.
If you have a multimode fiber,
the light can bounce around more
because of the larger core size.
And therefore you're going to have less distance
with multimode fiber because you have more noise.
This means multimode fibers tend to be less
expensive to build and buy, and they're cheaper to install
than a single mode fiber.
So a lot of network designers will actually
implement solutions that use multimode fibers
over single mode fibers whenever possible.
And to do that, they'll make sure they have lower distances.
So maybe they'll go 500 meters between switches
instead of two kilometers per switch.
Now, if you happen to be working in the field
and you're trying to identify a cable
as either a single mode or multimode fiber,
the easiest way to do this is by simply looking
at the color of the cable.
If the cable has a yellow sheath on it,
it's a single mode fiber or SMF cable.
If the cable has an Aqua blue or orange color sheath,
it means it's a multimode fiber or MMF cable.
Now, regardless of whether you use single mode or multimode,
you still have to terminate these cables
with some kind of a connector
so you can plug 'em in your devices.
Now there's going to be four different connector types
that you're going to come across.
SC, ST, LC and MTRJ.
For the exam, you need to be able to visually identify
each of these connectors.
If I showed you a picture of one,
you need to be able to describe it
and pick it out on the exam.
So how are you going to remember which one is which?
Well, don't worry.
I got some memory aids to help you with this
and make sure you get it right on the exam.
First let's look at SC,
which stands for Subscriber Connector.
Now SC is fairly popular because they're low cost,
they're durable, and they're easy to install.
Some people call these the square connector
or the standard connector.
But personally, I like to call it the stick
and click connector, 'cause it helps
remember what it looks like on exam day.
Now, when you look at an SC or a stick and click connector,
you're going to see a little ridge
on the top of it, a lot like an RJ45 connector.
And when you push the SC into a network jack or wall jack,
you're going to hear a little click that tells you
it's inserted properly.
Now this is why I call it the stick and click,
because you stick it into the jack
and you hear the click.
With SC, you're usually going to see two cables
bundled together, each one with its own SC connector on it
and that way you can plug them into the jack.
Each of these cables is going to be used
for transmitting or receiving the data.
So to transmit and receive, you need two cables.
Next, we have an ST or Straight Tip Connector.
Now the ST connector is also relatively low cost
and easy to use.
The ST is one of the older types
of fiber connectors we have and just like SC,
it has a transmit and receive cable
each with its own ST connector on it.
I like to call the ST connectors
the stick and twist connector,
because you're going to insert it into the jack
and then turn it about half a turn
to the right until it locks in place.
Now you're not going to hear it click like an SC connector,
but you are going to stick it in place and twist it
until it locks and stops turning.
Third, we have an LC or Lucent Connector.
This is a newer and smaller version of an SC connector.
Like the SC connector, it does use
a stick and click connection to the jack.
Now to remember the LC connector,
instead of the SC connector,
I like to call this the love connector.
This is because you're almost always going to find
the LC connector with its transmit and receive
sides attached side by side, like lovers.
You can actually place them together and they lock together.
Whereas the SC is often found as two individual cables,
the LC or love connector is almost always married together
and they're coupled up right next to each other.
Fourth, we have the MTRJ for Mechanical Transfer
Registered Jack.
MTRJ is a fiber optic cable connector
that's very popular and widely used
with networking devices because it is a smaller form factor.
It's much smaller than the other three we talked about.
Each MTRJ connector is going to have both the transmit
and receive pins terminated
inside a single plastic connector.
And this is about half the size of an SC, ST,
or LC connector.
This means that by using an MTRJ, you can have a switch
that fits 24 fiber reports in the same chassis size
as a regular RJ45 24 port copper switch.
Whereas with ST, SC, or LC, you'd only be able to get
about 12 switch ports in there.
Now, often you're going to see MTRJ used on fiber switches
and they're going to connect to fiber patch distribution panels
on one side, and the other side will convert it to SC, ST,
or LC for distribution out to a wall jack into an office.