Tag Archives: optical time-domain reflectometer

The Core Technology Of WIRING

1. High-precision Optical Time Domain Reflectometer(ODTR)

OTDR Price technology through sending a test signal in the measured line while monitoring signal in the line of reflection phase and intensity. If the signal through the cable encounter mutation of an impedance, part or all of the signals will be reflected back, the reflected signal delay, size and polarity indicate the discontinuity position and feature of the special impedance in the cable.

2. Split Pairs

UTP(Unshielded Twisted Pair) cable is two insulated Copper Ethernet Cable twisted together to each other by a certain density, which reduces the degree of signal interference, each wire in the transmission of radiation waves are offset by radio waves from the other line.

The so-called split pairs is the original two pairs are opened and yet again to reform a new pair. Because when this failure occurs, the end-to-end connectivity is good, so use a multimeter or hand tool such tools can not check it out. Only with a dedicated cable tester to check it out. Since crosstalk on the related lines of no kink, so online pairs when signal through will produce a high near-end crosstalk (NEXT).

Split pairs normally also be used, but often crosstalk index is large, only to run in the 10M application, can not achieve the 100M application.

3. The Standard Twisted Pair Terminations

Twisted pair eight lines are inserted into the plug (or termination) according to the standard. There are two termination criteria: EIA/TIA T568A/T568B, no essential difference between them, but the difference between color. The natural problem of termination is to ensure that: 1, 2 are a pair; 3, 6 are a pair; 4, 5 are a pair; 7, 8 are a pair. Note: Do not one cable end with T568A, but the other end with T568B. The mix use of T568A/T568B is a special connection method of cross connection. Projects more use T568B wire method.

In Ethernet, Pin1, Pin2 is a twisted pair responsible for network data transmission, Pin3, pin6 is a twisted pair responsible for network data reception, so 1, 2 a pair, 3, 6 a pair, 4, 5 a pair, 7, 8 a pair, it is a must, and not 1, 2, 3, 4, 5, 6, 7, 8 pairs, so called split pairs, will lead to serious signal leakage.

4. Wire Map

Ware Map: This is to confirm the integrity of link connection, mainly to check each pair of 8-core Twisted Pair Cable whether meets the required standards EIA/TIA- 568A/568B, whether the wire at both ends of cable is matching. If wrong, there are five cases include open circuit, short circuit, crossed pairs, reversed pair and split pairs.

● Open circuit: refers to the phenomenon of line off, generally due to bad crystal head cable connection, common with the cable test equipment can locate the fault point.

● Short circuit: refers to one or more wires touch each other in a metal core, resulting in a short circuit.

● Crossed pairs: refers to wire at both ends error in the routing process, which is one end with 568A and the other end with the 568B, usually such wire method used in network equipments level, or network cards connection, but as a general wiring to say, as long as the two ends of the wire method consistent, as for the module wire method can refer to the color above.

● Reversed pairs: this error is due to both ends of a pair line connected to the positive and negative error, is generally believed that the odd line number for the positive electrode, the even line as the negative electrode, for example, 568B Pin1 orange white lines to the first pair of positive, Pin2 Orange Line is negative, it can form a direct current loop, reverse connection is positive and negative confused in the same pair line.

● Split pairs: this is one of the common wire error, which is not strictly comply with wire standard, it is specified in the standard that 1, 2 is the first pair, 3, 6, is the second pair, if 3, 4 into the second pair will cause large signal leakage, which produces NEXT (near end crosstalk), this will cause the user’s Internet difficulties or indirect interrupts, especially in the 1000Mbps network it is particularly obvious.

Cable Testing With Fluke Cable Tester

No matter installing new cable, or troubleshooting the existing cable, cable testing plays an essential role in the process. Common tests for datacom cabling include length, wiremap, attenuation, NEXT, DC loop resistance, and return loss. When doing cable testing must with the Fibre Tester, and the Fluke Network Cable Tester is popular.

As networks evolve, so do the requirements of the cabling infrastructure to support them. New standards are continuously being developed to provide guidelines for cabling professionals when installing, testing, troubleshooting, and certifying either copper and fibre. Whether it’s 10BASE-T, 100BASE-TX or 1000BASE-T, there are specific requirements and potential pitfalls in implementing these technologies. And 10GBASE-T, it becomes even more critical to keep current with the latest proliferations in cabling and cable testing.

Cable testing provides a level of assurance that the installed cabling links provide the desired transmission capability to support the data communication desired by the users. Cable test instruments are designed with a variety of focused features for particular field tasks. They vary in price, performance, and application.

For example, there are typically two types of tools for checking network connectivity: the network tester tool and the Fluke tester. Sometimes an engineer will carry a noise generator which not only checks ethernet networks but also telephone lines. Network tester tool is the network checker which plugs directly into the line and reads out what line is connected on that drop, or if there is no signal there. This can also be done with a laptop computer, but it is easier to carry a network tester, since it is far smaller. The Fluke tester will read all four twisted pairs of a cable right from the drop at the workstation all the way back to the server room and will show exactly which pairs are good and if any are crossed or open. The engineer can put a noise on the line and trace it back to the complex loom of cables in the server room all arriving in the same area at the main switch or patch panel.

Verification test tools perform basic continuity functions, they assure that all wires in a cabling link are connected to the proper termination points and not to any other conductors. In twisted pair cabling, it is critical to maintain the proper pairing of the wires. Better verification test tools also verify wire pairing and detect installation defects like “split pairs”. Verification test tools may also assist in troubleshooting by providing a toner to locate a cabling link. Verification tools sometimes include additional features such as an Fibre OTDR to determine length of a cable or distance to a break or short circuit. These test tools do not provide any information on bandwidth or suitability for high-speed data communication.