In this lesson,
we're going to discuss the various fiber cable issues
you may experience, such as incorrect transceivers,
transmit receiver being reversed or dirty optical cables.
Now, first we might experience issues
with incorrect transceivers.
A transceiver is a transmitter
and a receiver in a single device.
Transceivers are going to be used
to convert a network connection from one type to another,
and they work at layer one of the OSI model.
In your routers and switches,
it's common to use a transceiver for your fiber connections,
but if you're going to be using the wrong transceiver,
this connection simply won't work.
Many transceivers are considered hot-pluggable,
and they can be taken out and replaced without shutting down
the associated router, switch or SAN device.
If a transceiver fails and you need to replace it,
this becomes quite easy
since you can simply unplug the bad transceiver
and plug in your replacement,
but you need to ensure you're using the correct transceiver.
Otherwise, you're going to have problems.
If you put in the wrong type of SFP transceiver,
you're going to have data loss
and a loss of connectivity over time.
Remember, transceivers are designed
to support a certain type of connection
and a certain type of cable.
If you're using a longwave SFP transceiver,
but then connect a shortwave fiber cable to them,
that's not going to work.
Therefore, if you have a device that's no longer working
and you recently changed out your transceiver,
you should go back and double check
that you're using the right model for your device
and your associated cabling.
Next, we can sometimes have issues when our transmit
and receive ends are being reversed.
Now, while this may occur
in a twisted pair network occasionally,
this is really going to be the biggest issue
inside your fiber-based networks.
Remember, most of our fiber connections are going to consist
of two individual cables, one for transmission of data,
and one for receiving that data.
For example, if you're connecting a switch
to a workstation using a network interface card,
that is ST connections on it,
one of those is going to be labeled TX for transmit.
The other one is going to be RX for receive.
Now, if you connect the transmit cable to the RX connection
and the receive cable to the TX connection,
you're not going to get a valid link or connection
to that switch.
If this happens, you can quickly identify
and fix this by simply disconnecting the TX
and RX port cables and swapping those cables.
Then when you do that,
you can check the LED link activity lights on your NIC,
and you're going to see the link is now online
and available as indicated by a solid orange light
or a blinking orange light if the network
is actively communicating again.
Finally, we have dirty optical cables.
Dirty fiber optic cables
and connectors can cause major performance issues
or connection problems inside your network.
A dirty fiber just means something is interfering
with the clear optical connection between the cable,
the connector, and the connection port
for the fiber connection.
Even something as small as some dust or dirt
or your fingerprints can really severely block the light
being sent down that cable.
Now remember, multimode fibers are only 50
to 62 microns in diameter,
so it really doesn't take much to block these connections.
If you find yourself with a dirty optical cable
or connector, you really just need to clean it
using a dry cleaning or wet cleaning method.
Dry cleaning involves simply using light pressure
while rubbing the end face of a fiber cable or connector
using a dry cleaning cloth in one direction.
This will usually be used when you need to clean dust
or dirt off the face of a connector.
This same technique can be used
for a fiber connection port on a switch
or network interface card too.
Wet cleaning involves lightly moistening a piece
of lint-free cloth with a fiber optic cleaning solution,
and then wiping the end face of the cable
in one direction as well.
This cleaning solution should be 91% or higher
isopropanol alcohol if you're using a solution.
Now, wet cleaning is considered more invasive
than dry cleaning, but it is useful
when trying to remove oil residues or films
off those cables and connectors,
such as if somebody has put their fingerprints on them.
You're going to have to use wet clean
to get those fingerprints off.
Now, if you start receiving a large amount
of errors over a fiber connection
or your performance begins to slow down,
it could be the indication
that you need to clean a dirty fiber.
This can also be quantitatively determined
if you're using a fiber light meter
because you can compare the decibel reading
from your baseline of a clean fiber versus this dirty fiber.