In this video,
we're going to discuss the various issues you may experience
with connectivity that are caused by cable signaling issues.
This includes attenuation, interference, and decibel loss.
First, we have attenuation.
Attenuation is a loss of signal strength on a network cable
or connection over the length of the cable.
This is a common occurrence in both wired
and wireless connections,
but for right now, we're going to focus
on wired connections only.
When we're using a copper cable, such as a twisted pair
or a coaxial cable,
we're going to transmit data across the cable
by sending electrical signals of varying voltages
that represent our binary ones and zeros
of the data being sent.
The copper conduit inside these cables
are going to carry those signals,
but that copper has a natural level of resistance,
and the longer the cable becomes,
the higher that resistance becomes,
and the data has a harder time
traveling down the copper cable.
This causes the signal to weaken
or attenuate as it travels along the distance of the cable.
When you learned about twisted pair cable, I told you
that we had this maximum distance of about a hundred meters.
Now, this is caused because of attenuation.
Once you get further than a hundred meters,
the signal's going to weaken and become unreliable.
With coaxial cables, you have more shielding
or insulation around it.
Therefore, you can reach distances
of up to about 500 meters.
But when you pass that limit,
the attenuation again becomes too much,
and the signal strength weakens to an unusable level.
So distance is going to be our main factor when we're dealing
with attenuation, but there's a couple other factors
that can affect your signal strength too.
This includes frequencies that are used by the connection,
the noise in the environment,
and the physical surroundings near the connection.
You see, all networking
and electrical cables operate at a specific frequency.
For example, power cables in a residential
or office setting are usually going to operate at 60 hertz
in the United States and Canada.
But if you're in another country,
it may operate at 50 hertz.
Ethernet cables though,
operate at different frequencies too.
If you're using a CAT 5e cable, for instance,
it uses a frequency of a hundred megahertz.
Well, a CAT 6 cable is going to use a frequency
of 250 megahertz.
A CAT 6a cable uses a frequency of 500 megahertz,
and a CAT 7 cable uses a frequency of 600 megahertz.
Now, in general, the higher the frequency,
the higher the bandwidth
that a particular cable is going to be able to produce.
This is because each hert is one cycle per second
in frequency, and so the more cycles you have in a second,
the more times you could put a one
or a zero down that cable.
So if you're going to use a network cable
that uses a frequency similar to the frequencies
of the cable surrounding it, you can have something known
as crosstalk or interference that's going to occur.
Now, this brings us to the concept
of noise in your environment.
If there's additional electrical frequency
or radio frequency noise in your area,
this can cause your network cables to have problems
and increase the rate of attenuation
and decreasing your associated signal strength.
For example, if you have a network cable
that's located near an area where heavy machinery
or power generators are being used, this will create noise
and signal interference that will decrease the distance
that cable is going to be able to support
because there's more attenuation
and more noise across that signal.
Finally, the physical surroundings
you're using your copper cables in
can also increase your attenuation.
Things like temperature, the construction of the walls
or other barriers, and the type of wire insulation itself,
can all negatively affect your signal strength.
If you have freezing temperatures, for instance,
your copper cables will become more brittle
and inflexible, which in turn slows down the connection
and attenuates the signal.
When you're experiencing hotter temperatures,
the signals can actually overheat
and the network cable could potentially even catch fire
if the outside plastic melts away
and the inside wire becomes exposed to flammable materials.
For this reason, it's always important
to have well insulated wires
and attempt to maintain the proper temperature control
that your network connection needs
to maintain a strong signal and minimal attenuation.
So, what can you do when you experience attenuation?
First, you can make sure you're using the proper cables
for the physical environment you're operating within.
If you're operating in a hotter
or colder environment, you may need to switch
to shielded twisted pair instead
of unshielded twisted pair, for example.
Second, you can shorten the distance.
While the maximum length is a hundred meters
for these cables,
it's a good idea to use cables
that are a bit shorter than that
to ensure you always have a good, clear signal
on all of your connections.
Personally, I tend to implement an 80 meter limit
on all of my twisted pair cables inside my networks.
Third, you can use an amplifier or a repeater.
These are layer one devices
that take in the signal on one end, boost up the signal
and retransmit it out the other side.
This means if I need to run a twisted pair
of cable over 150 meters, I could use a 75
or 80 meter cable connected to a repeater,
and then I can go the next 75 to 80 meters
to make the total 150 meters.
By using this repeater, there's going to be no signal loss
because we essentially re-broadcast out a new signal again
from that repeater as we start over our distance limitation.
If you're dealing with fiber cables instead
of copper cables, you have a lot of the same issues in terms
of attenuation because of distance,
but they don't begin to occur until much further out.
This is because we're using light
instead of electricity here.
Now, for example, let's say you have a single mode fiber
that is a maximum distance of 40 kilometers.
You're not going to really suffer much signal loss
until you get around 30 to 40 kilometers from your source,
depending on your environmental conditions.
Another cause of attenuation in fiber cables tends
to occur if you have cheaply constructed fiber cables
or you have fiber cables that have dirty connectors.
Let's imagine you have a pair of sunglasses on
and you have fingerprints all over the lenses.
That makes it really hard to see through 'em, right?
Because you have dirty glasses.
Well, the same thing happens with fiber connectors.
When you're dealing with fiber connections
and your fiber connectors are dirty, this can lead
to signal loss and attenuation
because the light can't cleanly pass
through those connectors because it's dirty.
This adds to attenuation and signal loss for you.
Now, if you're experiencing this attenuation
with fiber cables, the first thing I recommend you do
is change up the fiber cable for a higher quality cable,
or you clean and polish both ends of that fiber
and make sure those connectors are really clean.
You want to make sure there is not a dirty connector there
'cause even something as little
as your fingerprints on it
can cause this attenuation to occur.
Next, we have interference.
Interference occurs when multiple cables operate
in the same frequency band and they operate
in close proximity to each other.
To help prevent this,
we want to use high quality twisted pair cables
or use higher category rated cables.
Now, this is because higher category rated cables
are going to have more internal twists per inch
inside their internal twisted pairs.
These internal twists can help overcome the interference
that can occur within a single cable inside
of its own wired twisted pairs.
Now additionally, if you see a twisted pair network cable
that's being run over
or near a high power cable, this can cause interference
as well and a large amount of signal loss.
To solve this problem,
you always want to plan your cable runs to operate in parallel
and not directly next to any high power cables running
in your cable trays or your risers.
Finally, we have decibel or dB loss.
Now, decibel loss is used to measure the amount
of signal deterioration
that we're experiencing on a given connection.
This can be used to measure the signal on a copper
or fiber cable.
For copper cables,
we see this reported as a dB loss to represent the amount
of voltage that is decreased
since we sent the signal out originally
over that twisted pair cable.
For fiber connections though,
this dB loss is instead going to represent the amount
of light that's lost
as it travels across the cable or the connection.
If you're experiencing a high amount
of dB loss on a copper cable, you need to replace that cable
with a higher quality twisted pair cable
with additional shielding
or a higher number of twists per inch.
If you're experiencing a high amount
of dB loss on a fiber cable, you want to replace that cable
with a higher quality fiber cable, such
as a glass one instead of a plastic one.
Or you need to clean and polish both ends of your cable
and the associated connectors.
Alright, we just covered
our three big cable signaling issues
that you are going to experience in the field
as a network technician.
Just a reminder, these are attenuation,
interference, and decibel loss.
When you're testing your network for attenuation conditions,
always use a cable certifier
to measure the amount of attenuation.
For fiber connections, you're going to use a fiber light meter
to test for attenuation as well.
If you need a test a connection for interference,
you can connect a spectrum analyzer to the cable
to see the exact frequencies
and signals that are being sent over that connection.
If you want to test for decibel loss,
you're going to use a cable certifier, a cable analyzer,
or a fiber light meter to measure the signal being sent
and received across a given cable
and report back that loss in decibels.
For the exam,
it's important to understand the tool you might use
to troubleshoot the different cable connectivity issues.