8.1 General wiring test overview
8.1.1 Contents of comprehensive wiring test
â— The connectivity between the workshop and the equipment; â— The connectivity of the trunk line; â— The jumper test; â— The test of information transmission rate, attenuation, distance, wiring diagram, near-end crosstalk and other parameters.
8.1.2 Two tests for cables
At present, the most widely used cables are optical cables and unshielded twisted pair (commonly called UTP).
1. Cable verification test
8.1.3 Relevant standards for cable testing
The main content of TSB-67 test standard:
(1) Definition of two connection models. The cable connection model is divided into a channel model and a basic link model.
(2) Definition of various parameters to be tested.
(3) Pass and fail test limits of various parameters are defined for each connection model and various links (category 3, category 4, category 5).
(4) The performance requirements of the field tester and the definition of how to verify these requirements.
(5) The method of comparing field test results with laboratory test results.
8.2 Test technology of twisted pair
8.2.1. Verification test of twisted pair
In the construction process of the wiring project, common connection failures are: cable label error, connection open circuit, twisted pair cable wiring diagram error (such as wrong pair, reversed polarity, series winding, etc.) and short circuit.
1. Open and short
Open circuit means that the continuity of the cable link from one end to the other end cannot be guaranteed; a short circuit usually means that more than one pin in the socket is connected to the same copper wire.
2. Reverse connection
The wrong connection of the same pair of wires at the two ends, such as 1-2 at one end and 2-1 at the other end.
3. Wrong
The unified standard TIA / EIA-568-A or TIA / EIA-568-B must be used in the twisted pair wiring process. If two cables are connected, 1-2 of one cable is connected to 3- of the other cable. On the 6-pin, it is wrong.
4. Tandem
Cross-winding is to separate the original two pairs of wires and form a new pair.
8.2.2 Certification test of twisted pair
1. Test standards
â— TIA / EIA-568 "Commercial Building Telecommunication Wiring Standard";
â— TSB-67 "Technical Specification for Field Test and Transmission Performance of Unshielded Twisted Pair Cabling";
â— ISO / IEC 11801: 1995 (E) international wiring standard.
2. Certification test model
In order to test the UTP wiring system, the horizontal connection should include information sockets / connectors, conversion points, 90mUTP (category 3 to 5), a cross-connect device including two terminal blocks or sockets, and a patch cord with a total length of 10m. During the test, you can choose the channel model or the basic link model.
3. Certification test parameters
1) Wiring diagram (WireMap)
2) Link length
3) attenuation
4) Near-end crosstalk (NEXT) loss
(1) It should be tested in an environment where there are no electric welding, electric drills that generate severe electric sparks, or equipment that generates strong magnetic interference.
(2) The temperature at the test site is about 20 to 30 ° C, and the humidity should be 30% to 85% RH.
8.2.3 Methods to resolve test errors
When testing the twisted pair, the possible problems are: the wiring diagram fails, the length fails, the attenuation fails, the near-end crosstalk fails, and it may also cause test errors due to problems with the tester.
1. Wiring diagram failed
The reasons may be: â— The connectors at both ends are broken, short-circuited, crossed, broken open; â— The jumper is wrong. Some networks need to be connected between the sending end and the receiving end. When constructing test links for these networks, the test wiring diagram will be crossed due to the cross-connection of equipment lines.
2. Length failed
The reasons may be: â— The NVP setting is incorrect, you can use a known good line to determine and re-calibrate the NVP; â— The actual length is too long; â— Open or short circuit; â— The total length of the device wiring and jumper is too long.
3. Attenuation failed
The reasons may be: â— The length of the twisted pair is too long; â— The temperature is too high; â— There is a problem with the connection point; â— There is a problem with the performance of the link cable and the connector, or it is not the same type of product; â— There is a problem with the quality of the termination of the cable .
4. Near-end crosstalk failed
The reasons may be: â— There is a problem at the near-end connection point; â— A short circuit at the far-end connection point; â— String pair; â— External noise; â— There is a problem with the performance of the link cable and the connector, or it is not the same type of product; â— The end of the cable There is a problem with the quality of the connection.
5. Tester problem
â— When the tester does not start, you can replace the battery or charge; â— When the tester does not work or can not perform remote calibration, you should ensure that both testers can start, and have enough batteries or replace the test line; â— Tester settings When the cable type is not correct, the parameters, category, impedance and transmission speed of the tester should be reset; â— When the tester is set to an incorrect link structure, it should be reset to the basic link or channel link as required; â— When the tester cannot store automatic test results, confirm whether the selected test result name is unique, or check the available memory capacity; â— When the tester cannot print the stored automatic test results, the interface parameters of the printer and tester should be determined and the Set to the same or confirm that the test result has been selected as the printout.
8.3 Test equipment for twisted pair
8.3.1 Audio generator and audio amplifier
It is a test device often used by voice testers and wiring personnel. These two devices are relatively simple.
Function: Mainly used to identify and locate communication cables. Generally, every wiring technician should have these two devices, as shown in Figure 8.6.
The audio generator can be connected to the cable pair by inserting a standard plug into the socket or clamping the pair with an alligator clip. After the audio generator is connected to the cable pair, the cable is activated.
There is a metal probe at one end of the audio amplifier, which can be connected to the wire pair of the multi-pair trunk cable or the clip of the punching module.
8.3.3 Connectivity Tester
Function: Mainly used for testing the connectivity of the cable, its test speed is much faster than the multimeter.
It consists of two parts: the base part and the distal part. The base part is placed at one end of the link, and the remote part is placed at the other end of the link. During the test, the tester applies a voltage along all pairs of the twisted-pair cable, and the remote part is connected to each pair with an LED light-emitting diode.
The twisted pair link faults that the connectivity tester can detect are: open circuit; short circuit; wire pair crossover; poor cable termination.
8.3.4 Cable analyzer
The cable analyzer is a more complex test and evaluation device. In addition to the basic connectivity test, this tester can also perform more complex cable performance tests. The cable analyzer is also used to determine whether it can support high-speed networks when testing cable links.
1. DSP-100 tester
1) Composition of DSP-100 tester
The DSP-100 tester consists of a host (base part) and a remote part. The four function keys of the main unit depend on the current screen display.
2) Quick use of DSP-100 tester
2. Fluke620 LAN cable tester
The Fluke620 is the only cable tester that requires neither a remote connector nor an installer to help at the other end of the cable. The Fluke620 allows the installer to use it freely during installation and testing. As long as a connector is fitted, the installer can immediately confirm the cable connection and wiring through the Fluke620.
(1) Cable test. If the cable installer is equipped with a cable identifier, the Fluke620 can detect more errors (wrong pair of twisted pairs, reverse connection), and makes the identification of the cable connection path (trend) very easy.
(2) Specific operation.
(3) Cable length. The specific requirements are as follows: ◠Range: 0.5 ~ 300m; ◠Resolution: 0.5m; ◠Accuracy: ± 1m.
(4) Power supply. Using two AA-type 1.5V alkaline batteries, it can work continuously for 50 hours. Using a backlight will reduce battery life. Because the product has an automatic power management function, the battery can work for several months under normal use.
(5) Input protection. Enter a voltage that can withstand the ringing of the phone, and a warning sound when overvoltage.
(6) The attached accessories are: ◠User manual; ◠Quick check card; ◠Portable soft case; ◠Cable identifier (No. 1); ◠1 RJ-45—RJ-45 cable (TIA / EIA4 to 5); ◠1 RJ-45-RJ-45 coupling socket.
(7) Optional parts. It mainly includes:
â— N6210 cable identifier No. 2 ~ 4; â— N6202 cable identifier No. 5 ~ 8; â— N6203 STP cable assembly, including: connecting STP (IBMTYPE1) cable; IBM data connector and DB9 adapter, the neutral line length is 1m; data connector With RJ-45 adapter, the neutral line is 0.3m long.
3. Wire Scope 155 tester
1) Wire Scope155 performance summary
Wire Scope155 is mainly for super 5 types of high-speed network maintenance and comprehensive wiring engineering acceptance work, only the size of a multimeter, easy to carry.
WireScope155's optical fiber test module is the smallest and most powerful in the world. It can not only test the attenuation of optical fiber, but also test the length and propagation delay.
8.3.5 UTP cable certification test report
After a twisted pair cable is tested by the tester, a certification test report will be provided to the user. The content of the report is shown in Table 8.5.
8.4 Optical cable test technology
8.4.2 Fiber test parameters
1. Fiber continuity 2. Fiber attenuation 3. Fiber bandwidth
8.4.3 Various causes of fiber attenuation
1. The main factors that cause fiber attenuation are: intrinsic, bending, extrusion, impurities, unevenness and docking.
2. The classification of fiber loss can be roughly divided into the inherent loss of the fiber and the additional loss caused by the use conditions after the fiber is made.
Inherent loss includes scattering loss, absorption loss and loss caused by imperfect fiber structure;
Additional losses include microbending loss, bending loss and connection loss.
3. Material absorption loss
4. Scattering loss
5. Imperfect structure of optical fiber itself
8.4.4 Test method of optical fiber
Generally, we have four test methods for optical cables in specific projects: connectivity test, end-to-end loss test, transceiver power test, and reflection loss test.
8.4.5 Loss of optical fiber link
Connection loss is a problem that must be considered when using optical fiber transmission media. Any equipment connected to the optical fiber may cause different levels of loss in the light wave power. The light wave itself will also produce a certain loss when propagating in the fiber. The laying of optical cables requires that the total connection loss between any two end nodes should be controlled within a certain range, for example, the connection loss of multimode fiber should not exceed 11dB.
In general, the end-to-end connection loss includes the following aspects:
(1) Connection loss between the node and the distribution frame, such as various connectors;
(2) The attenuation of the fiber itself;
(3) Loss caused by the interconnection of optical fibers and optical fibers, such as optical fiber fusion or mechanical connection;
(4) The amount of loss allowance reserved for the future, including maintenance connection, thermal deviation, safety considerations and the impact of the aging of the transmission device, etc.
(5) The combination of optical fiber coupling devices of different sizes will also produce losses, and this loss varies with the transmission power.
8.5 Optical cable test equipment
Commonly used optical cable testing equipment are: visual cable tracer and fault locator; optical power meter; optical fiber test light source; optical loss tester; optical time domain reflectometer.
8.5.1 Flash
The flash is the first test device used before testing the performance of the fiber link segment. This device can easily detect both ends of the fiber. When the fiber is marked incorrectly or the installed patch panel port is not correct, using the flash test can save a lot of time.
Disadvantages: The light level emitted by the device is relatively low, so that the actual light entering the fiber is relatively small. These lights are difficult to see or cannot be seen at all after long-distance transmission.
8.5.2 Visual cable tracer and fault locator
It is a simple optical cable testing device that can be used to locate unmarked optical cables or diagnose faults in wiring links. It can test optical link segments with a length of more than 5km. Using these two devices to locate and handle fiber link faults is very time-saving.
8.5.3 Optical power meter
Optical power meter is the basic test equipment for testing fiber link loss. It can measure the optical fiber output power of the optical cable. In the optical fiber link section, the loss and attenuation of the transmitted signal can be measured with an optical power meter.
Most optical power meters are portable devices and are generally used in conjunction with fiber optic test light sources. The test wavelength of the optical power meter used in the multimode optical cable wiring system is 850nm and 1300nm, which is the test equipment used for wiring optical cables in the building and the building area; the test wavelength of the optical power meter used to test the single mode optical cable is 1310nm and 1550nm , Is the most commonly used equipment for field optical cable testing.
8.5.4 Optical fiber test light source
The optical fiber test light source is used together with the optical power meter. When the optical power meter is used for measurement, there must be a stable light source. The optical fiber test light source can generate stable light pulses, so that the optical power meter can test the loss of the optical fiber link segment.
8.5.5 Optical loss tester
The optical loss tester (OLTS) is composed of an optical power meter and an optical fiber test light source. It also includes all optical fiber jumpers, connectors and couplers necessary for link testing.
8.5.6 Optical time domain reflectometer
Optical time domain reflectometer (OTDR) is the most complex optical fiber test equipment. The device can be used to test fiber loss and length, and to determine the cause and location of faults in the fiber link.
There are currently two types of optical time domain reflectometers:
â— Comprehensive optical time domain reflectometer. This type is expensive, but has good performance and many functions.
â— Small optical time domain reflectometer. The price of this type is lower, but the function is less than the full type.
8.5.7 Optical fiber test procedure
1. Hardware and purpose required for testing fiber links
(1) Two optical fiber loss testers (OLTS) for testing optical fiber transmission loss;
(2) In order to enable conversation between the operators who are testing at two locations, a wireless phone or walkie-talkie is required;
(3) 4 optical fiber jumpers to establish the connection between the tester and the optical fiber link;
(4) Infrared display, used to determine whether light energy exists;
(5) Glasses (testers must wear glasses).
2. Optical fiber link loss test procedure
â‘´. Set up the test equipment according to the instructions provided by the tester.
⑵. Zero the OLTS to eliminate energy level offset. When testing very low light levels, non-zero adjustment will cause a large error, and zero adjustment can also eliminate the loss of the jumper.
⑶. Press and hold the ZEROSET button for more than 1 second, and wait for 20 seconds to complete the calibration.
â‘·. Test the loss in the fiber link (loss in the direction from position A to position B).
â— Disconnect the jumper S1 at the detector socket (IN socket) at position A, and connect S1 to the fiber link under test;
â— Disconnect the jumper S2 at the detector socket (IN socket) of position B;
â— Connect another fiber jumper between the detector socket (input port) at position B and the end of position B at the fiber path under test;
â— Test the loss in the A to B direction on the tester at position B.
⑸. Test the loss in the fiber link (loss in the direction from position B to position A).
â— Disconnect the jumper D2 at the fiber link in position B;
â— Connect jumper S2 (at position B) to the fiber link;
â— Disconnect the jumper S1 from the fiber link from position A;
â— Use another jumper D1 to connect the detector socket (IN port) at position A to the fiber link at position A;
â— Test the loss in the B to A direction on the tester at position A.
⑹. Calculate the transmission loss on the fiber link, and then carefully record the data.
⑺. When a fiber link is established, the initial loss of the fiber link is tested. Carefully record the initial loss that was tested when installing the system.
â‘». If the measured data is higher than the originally recorded loss value, then all fiber optic connectors should be cleaned.Special Material Braided Sleeve
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