In order to install a high performance and reliable Category 6 (CAT 6) system, testing should be done. Contractors and installers rely on test results to warrant their installations and ensure their customers that they have received professional services. Testing for CAT 6 performance is the best solution in maintaining a secure network; through component, permanent link, and channel.
Component compliance is the most crucial part in testing a CAT 6 system. Without component compliance, any modifications and changes to the system may result in a lower performance. Only top manufactures will perform extensive component test plug de-embedded testing, component patch cord testing, and provide tests results to acknowledge that contractors and installers will receive reliable CAT 6 products.
In the permanent link we have learned CAT 6 cable is good for distances up to 90 meters / 295’, The permanent link test is for the horizontal cable from the patch panel to the RJ-45 jack in the faceplate or a maximum of 90 meters / 295’. This will certify that the link is good first and also help in trouble shooting.
Patch cords can be added to the permanent link for up to a total of 10 meters, or 33’ for a total of 100 meters/ 328, and this is the channel. The channel test is adding in the patch cables with both ends for a total of 100 meters/ 328’. When the link is good, but the channel is not then you know almost certainly that one or more of the added patch cords are bad. (see Figure 1.)
a. Field Test Equipment
b. Begin Channel
c. End Channel
d. Begin Permanent Link
e. End Permanent Link
f. CAT 6 Patch Cord
g. CAT 6 Telecommunications Outlet/Connector
h. CAT 6 Cable (optional transition cabling)
i. Transition or Consolidation Point (optional)
j. CAT 6 Cable Horizontal Cabling
k.CAT 6 Patch Panel
l. CAT 6 Patch Cord Horizontal Cross-Connect
m. CAT 6 Patch Panel
n. CAT 6 Patch Cord
o. Field Test Equipment
What test should be performed? Contractors and installers should perform several tests in order to meet true CAT 6 performance for permanent link and channel compliance.
Return Loss test is a measure of the reflected energy caused by impedance variations in the cable and is especially important for applications that use simultaneous bi-directional transmission. Impedance mismatches cause reflections, which distort high speed data signals. A cable with good return loss will tend to have few signal reflections in the pair due to changes in impedance. A cable with poor return loss characteristics will lose signal strength or be highly distorted due to the signals being reflected.
The Insertion Loss, or also known as Attenuation, measured in dB, occurs when a device is inserted into a copper or fiber optic transmission line. In a telecommunications circuit void of any connections, each jack, plug or splice added will increase the attenuation of the circuit
Attenuation is the change in transmission signal strength between two points. The measure is in decibel(s), dB. For copper the measurement is usually taken at a certain frequency (or several), and for fiber at a specific wavelength. Attenuation is one of the major performance affecting factors of data cable, both copper and fiber. The signal at the distant end must be "loud" enough for the receiver to "hear" it. If it is not loud enough, an error may occur in the network causing retransmissions and impacting the network performance.
NEXT (near-end crosstalk) shows the level of noise interference between each pair of signals at one end of the channel measured against a transmitted signal at that same end. A familiar example of cross talk in general is when you hear a second conversation on the telephone while you are talking. If there is too much crosstalk, it may interfere with transmitted signals. The noise is mainly generated where the connectors mate because the twisted pairs must run straight for a short distance.
PSNEXT (power sum near-end crosstalk) shows the level of noise interference from all three of the other pairs summed together on each pair of signals at the near end to the transmitter. This is the noise level when all four pairs are used at the same time as with Gigabit Ethernet. Crosstalk can be minimized by retaining the cable pair twist configuration as much as possible when terminating the cable on the connecting hardware.
Attenuation to Crosstalk
Attenuation to Crosstalk (akin to ACR) shows the frequency range for which the signal is strong enough to be detected over the noise when using any two pairs. This is probably your most useful graph because this gives you a visual depiction of your frequency bandwidth, as you can see the point where your signal is no longer discernable from the noise.
Attenuation to PSNEXT
Attenuation to Power Sum Crosstalk (akin to PSACR) shows that the signal is strong enough to be detected over the noise when you are using all four pairs at one time. This is probably your most useful graph for because this gives you a visual depiction of your bandwidth for Gigabit Ethernet, as you can see the frequency at which your signal is no longer discernable from the noise.
FEXT (far end crosstalk) is the measurement of crosstalk in dB at the opposite end of the cable from which the signal originated. FEXT is important, but with today's transmission schemes Power Sum ELFEXT is much more important.
ELFEXT (equal level far-end crosstalk) shows the level of noise interference between each pair of signals at one end of the channel measured against a transmitted signal coming from the opposite end of the channel with the effects of attenuation removed. As with NEXT (near-end crosstalk) the noise is mainly generated where the connectors mate because the twisted pairs must run straight for a short distance. ELFEXT removes the impact of insertion loss on Far End Crosstalk.
PSELFEXT (power sum equal level crosstalk) is one of the mandatory tests under ANSI/TIA/EIA 568-B.1 and B.2 Standard. It shows the level of noise interference from all three of the other pairs summed together on each pair of signals at one end of the channel measured against a transmitted signal coming from the opposite end of the channel.
ACR (attenuation to crosstalk ratio) is the ratio of attenuation and crosstalk measured in dB at a given frequency. Sometimes known as Signal to noise ratio, this measurement is one of the defining tests for data cabling. If the result of this measurement is too low, then the receiving end will not hear the signal over the noise created on the line from other pairs. EIA/TIA specifies specific values for ACR in order to meet the various categories of cable. In Category 5e and 6 cables systems, Power Sum ACR is used, which is the cross talk calculation using 4 energized pairs.
PSACR (power sum attenuation to crosstalk ratio) is similar to ACR except that Power Sum NEXT is used in the calculation instead of NEXT. PS-ACR is one of the main tests used when comparing various cables to determine which cable is better. PS-ACR is the difference between Attenuation and PSNEXT. The result is referred to as "head room". The more head room a cable or system has the more forgiving it will be with installation errors (apart from miss wiring).