Introduction, development, and testing of structured cabling systems

Before giving you a detailed introduction to the structured cabling system, let's first take a look at the introduction and development of the structured cabling system, and then give a comprehensive introduction to the structured concepts and questions about the testing of the structured cabling system, I hope you will understand the structured cabling system after reading it.

1. Introduction to structured cabling systems

With the rapid development of computer and communication technologies, network applications have become a growing demand. Structured Cabling is the basis for network implementation, it can support the transmission requirements of data, voice, graphics and images, and become a powerful supporting environment for today's and future computer networks and communication systems.

Structured cabling systems are closely related to the development of smart buildings and are the basis for the implementation of smart buildings. Smart buildings are characterized by comfort, safety, convenience, economy, and advancement.

It generally includes: central computer control system, building automatic control system, office automation system, communication automation system, fire automation system, security automation system structured wiring system, etc, through the design of four basic elements of a building (structure, system, service and management) and their inner connection optimization, it provides an elegant, comfortable, convenient, fast, and highly secure environment with reasonable investment and high efficiency.

The structured cabling system is the foundation for achieving this goal.

Ii. development of structured cabling

The initial implementation of structured cabling has been around for more than a decade. In 1984, the world's first smart building was created. People used computers to monitor air conditioners, elevators, lighting, and fire prevention systems in a type building in Hatford, United States, it provides customers with information services such as voice communication, text processing, electronic parcels, and intelligence materials. At the same time, a number of companies transfer to the cabling field, but the product compatibility between manufacturers is poor.

Iii. Concept of structured cabling

1. Definition

A structured cabling system is a telecommunications cabling system that supports voice, data, and image applications selected by any user. The system should be able to support transmission of voice, graphics, images, data multimedia, security monitoring, sensing and other information, and support various transmission carriers such as UTP, optical fiber, STP, and coaxial cable, supports multi-user and multi-type product applications and high-speed network applications.

2. Features

Structured cabling systems have the following features:

1) Practicality: supports a variety of data communication, multimedia technology and information management systems to adapt to the development of modern and future technologies;

2) Flexibility: Any information point can be connected to different types of devices, such as computers, printers, terminals, servers, and monitors. 3) Openness: it can support any network products of any manufacturer, supports any network structure, such as bus, Star, and ring. 4) Modularization: All connectors are modular standard parts for ease of use, management, and expansion;

5) Scalability: The Structured Cabling System after implementation can be expanded, so that devices can be installed and connected easily when there will be greater demands in the future;

6) Economy: one-time investment, long-term benefits, low maintenance costs, and minimal overall investment.

3. Composition of the cabling system

The structured cabling system consists of six subsystems: Workspace subsystem, horizontal trunk subsystem, management subsystem, vertical trunk subsystem, equipment subsystem, and complex trunk subsystem.

1) main subsystems of Buildings

Connect external buildings with cabling in the building. The EIA/TIA569 Standard specifies the physical specifications of network interfaces to achieve the connection between buildings.

2) device Subsystem

It is the primary management area of the cabling system, and data on all floors is transmitted by cables or optical fiber cables. Generally, this system is installed in the host room of the computer system, network system, and NC control system.

3) Vertical trunk Subsystem

It connects communication rooms, equipment rooms, and entry devices, including trunk cables, intermediate switches and main switches, mechanical terminals, and connectors or plugs used for Trunk-to-trunk switches. The main wiring should adopt a star topology, And the grounding should comply with the requirements stipulated by EIA/TIA607.

4) Management Subsystem

This part is placed in telecommunications cabling system equipment, including horizontal and trunk cabling systems for mechanical terminals and 1 or exchange.

5) level trunk Subsystem

Connect the management subsystem to the work zone, including horizontal cabling, information outlets, cable terminals and exchanges. The specified topology is a star topology.

Three types of media available for horizontal cabling (100 ohm UTP cable, 150 ohm STP cable, and 62.5/125 Micron Optical Cable) are available, with the maximum extension distance of 90 meters, in addition to the 90-meter horizontal cable, the total length of the connector and cross-wiring cable between the work zone and the management subsystem can reach 10 meters.

6) Workspace Subsystem

The work zone is extended from the information outlet to the station device. The workspace wiring requirements are relatively simple, which makes it easy to move, add, and change devices.

4. performance specifications of media and connected hardware

In the Structured Cabling System, the cabling hardware mainly includes the distribution frame, transmission medium, communication socket, plug-in board, cable trough and pipeline.

1) Media

It mainly includes twisted pair wires and optical fiber cables. It is mainly used in China to mix unshielded twisted pair wires and optical fiber cables. Optical fiber is mainly used for high-quality information transmission and trunk connection. It can be divided into Multimode Optical Fiber and single-mode optical fiber based on signal transmission methods, with a wire diameter of 62.5/125 micron. Multi-mode optical fiber is used for horizontal connection and single-mode optical fiber is used for vertical trunk. At present, the use of 100 ohm unshielded twisted pair has become a consensus, which is divided into three categories, four categories and five categories.

2) connectors and sockets

Each workspace should have at least two information sockets, one for voice and one for data. Pin combinations of sockets are: 1 & 2, 3 & 6, 4 & 5, 7 & 8.

3) Selection of blocked and unshielded Systems

China basically adopts the North American Structured Cabling strategy, that is, the hybrid cabling method with no shielded twisted pair wires and 10 optical fibers.

(1) Meaning of Blocking

The shielding system is used to ensure the transmission performance of the system in an interference environment. Anti-interference performance includes two aspects: the ability of the system to resist external electromagnetic interference and the ability of the system itself to intercept external electromagnetic interference. For the latter, Europe has passed the EMC standard for electromagnetic compatibility testing. The general method of shielding is to mask the metal on the outer layer of the connected hardware to filter out unnecessary electromagnetic waves. There are two kinds of shield lines with different structures: STP and SCTP.

(2) shielding system defects

A. grounding problem

The shielding layer of the shielding system should be grounded. When the frequency is lower than 1 MHz, a ground connection is enough. When the frequency is higher than 1 MHz, EMC deems it best to ground the ground at multiple locations. The common practice is to ground at a length of 1/12 at a wavelength, and the length of the grounding line should be less than of the wavelength. If the grounding is poor (the grounding resistance is too large, the ground potential is not balanced, etc.), it will generate a potential difference, which will constitute the biggest obstacle and hidden danger to ensure the shielding of system performance.

B. System Integrity

Shielded Cables cannot determine the overall EMC performance of the system. The integrity of the shielding system depends on the weakest component in the system. Such as jumper panel, connector information port, and equipment. Therefore, if an attack occurs during the installation of the shielding wire, it constitutes the most dangerous link in the Child shielding system.

C. Anti-interference performance of screen substreams

The shielding layer of the shielding system does not reduce the noise of low frequency. at low frequency, the noise of the shielding system is at least the same as that of the non-shielding system. In addition, because of the absence of uniform standards for the shielded 8-core module plug, and the absence of on-site test shielding of effective procedures, people generally do not use shielded twisted pair wires.

Iv. Wiring Test

LAN installation starts with cables, which are the basis of the entire network system. The test of the structured cabling system is essentially a test of the cable. According to statistics, more than half of network faults are related to cables. The quality of cables and the quality of Installation directly affect the healthy operation of networks. In addition, it is difficult to maintain the cables after construction is completed.

Currently, five unshielded twisted pair wires are widely used for structured cabling. Most of users' current application environments are based on 10 m networks. Therefore, it is necessary to test the performance of structured cabling systems to ensure future applications.

For cable testing, the principle of "installation with test" is generally followed. According to the definition of TSB67, field tests generally include wiring diagram, link length, attenuation, And NEXT crosstalk.

1. Wiring Diagram

This test verifies the correct connection of the link. It is not only a simple logical connection test, but also confirms the connection between each needle at one end of the link and the corresponding needle at the other end. At the same time, it tests the string bypass problem, locate the problem and promptly correct it. It is a very important test item to ensure that the cables are properly twisted.

2. link length

According to the T1A/E1A606 standard, the length of each link should be recorded in the management system. The length of the link can be estimated by measuring the electronic length. The electronic length measurement is based on the transmission delay of the link and the NVP value of the cable. Since NVP has an error of 10%, the stability factors should be considered during measurement.

3. Attenuation

Attenuation is the measurement of signal loss along the link. The attenuation varies with the frequency. Therefore, the attenuation of all frequencies within the application range should be measured. Generally, the maximum step size is 1 MHz. The TSB-67 defines a formula for Link attenuation and provides a table of allowable attenuation values for the two measurement modes. It defines the allowed value at 20 ℃.

4. Transient crosstalk (NEXT) Loss

The NEXT loss measures the signal coupling from one line to the other line in one link, that is, when the signal runs on one line, at the same time, a small amount of signals will be sensed to other line pairs. This phenomenon is crosstalk.

According to the TSB-67 standard, five types of links must be tested within 1-10 MHz bandwidth, the test step is:

◆ The maximum step size is 0.1 MHz within the 1-MHz frequency range;

◆ The maximum step size is 31.26 MHz within the 0.25-MHz frequency.

All tests require a line time test. For example, 6 groups of tests are required for 4 pairs of cables.

At the same time, the NEXT test should be performed at both ends. NEXT is not a measure of the crosstalk produced at the near-endpoint, but a measure of the crosstalk measured at the near-endpoint. This value will decrease with the attenuation of the cable length, and the signal at the remote end will also decrease, and the crosstalk on other lines will also decrease.

Experiments show that only the NEXT measured within 40 meters is more realistic. If the other end is an information outlet farther than 40 meters, it will produce a certain degree of crosstalk, however, the measurement instrument may not be able to measure the crosstalk value. Therefore, a two-way test is required.