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Date Submitted Wed. Aug. 21st, 2013 8:39 AM
Revision 1
Syntax Master claireling
Tags cable | Cables | Cabling | Copper | fiber | pair | twisted
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Shielded VS. Unshielded

In Ethernet Cable Wiring system at all levels, there are two main technical types: Shielded and Unshielded cabling systems. Since the earliest fabric cabling standards since its establishment types on these two technologies are widespread in the market. Germany, Australia, Switzerland and France in the first preference or relatively shielded cabling system, while in other parts of the world, the more popular non-shielded cabling system and will soon be adopted. Both shielded and unshielded gigabit transfer rate to meet the requirements, but when the transmission rate up to Gigabit or even higher, the shield system to support the stability of the advantages of the high frequency transmission becomes very apparent.

Cable structure
What is the function of shielded?
F/UTP cable shielding structure is four pairs of wires in the data cable outside the contractor a layer of aluminum foil shielded, this layer of shielding can be reduced to a great extent the total package:
1. This is the root of the signal transmission cable radiated interference signals on the impact of adjacent data cable (for example: the same bundle of cables in the adjacent data cable).
2. Interference from other data cable or other interference source signal for this cable.
3. For a high quality data transmission system, which is significant in two kinds of effects. If the external interference signal is strong enough it will happen with the normal transmission signal stack a plus, resulting in reduced transmission performance even the entire system can not work properly.
S/FTP structure in addition to the total package of braided foil shield, Twisted Pair Cable is respectively in each pair with a layer of aluminum foil shield to protect the transmission signal does not interfere with each other, so near-end crosstalk attenuation (NEXT)performance dramatically. NEXT better performance means higher SNR and better transmission quality and faster system output. S/FTP shielded cables NEXT excellent structural performance of other cables (such as non-shielded U/UTP) can not be compared, therefore, ISO11801 on the Cat 7 (600MHz) and Cat 7a (1000MHz) only provides the S/FTP cable structure, U/UTP cannot meet.
10GBase-T make data cable is facing new problems: Alien Crosstalk
2006 Copper Gigabit Ethernet applications published the proposed new standard transport protocols 10GBASE-T compared to 1000Base-T, its transmission rate increased 10 times.
1000BASE-T copper cabling required parameters (Attenuation, NEXT, Return Loss, etc.) the bandwidth required to reach 1-100MHz, with UTP Cat 5e (Class D) cabling system to meet requirements.
10GBASE-T cabling channel requirements of all component parameters have to be up to 500MHz bandwidth, which requires copper to reach at least Cat.6A (Class Ea) or higher level.
Along with the development of 10GBASE-T, external noise problems become more evident, resulting in a specification for external noise to be used to assess in the same bundle of cables, the interaction between different cables. This is what we call Alien Crosstalk. Alien Crosstalk will increase with the increase of frequency.
Worse, 10GBASE-T confronted with external noise, will not be able to "adaptive" to lower the rate at which the network may be subsequently face paralysis.
Therefore, to support 10GBASE-T cabling system application, the ability to resist alien crosstalk is vital.
. Since 10GBASE-T high transmission frequencies and complex coding method is very sensitive to the external noise.
. Shielding system excellent coupling atttenuation performance makes it naturally have to resist alien crosstalk.
. The unshielded system against alien crosstalk is usually only on the performance of 0dB.
. Shielding system in the design is completely satisfy the application of 10G.
The installation of 10GBase-T: U/UTP VS. FTP
Unshielded system: As far as possible away from power cable during installation; Different applications (1Gb/s and 10Gb/s) in the same pipeline transmission will cause the external crosstalk.
Shielding system: With the power cable can be reduced separation distance; Allow different applications (1 Gb / s and 10 Gb / s) in the same pipeline transmission; Does not need additional external crosstalk test field.
The separation distance between the data cable and power cable

In EN50174 standard defines the content of different coupling attenuation value level of data cable, respectively, from A (low coupling attenuation, worse) to D (high coupling attenuation, good) four levels.

Table 1- Classification of information technology cables
Installers need to know which cable separated levels to determine the choice of the data requirements of the standard cable with power cable between the minimum separation distance. Data cable coupling attenuation higher the value and power cables minimum separation distance between the smaller.
Please refer to the following three examples, screenshots from Nexans Toolkit.
Example 1: U/UTP (Class B - Coupling Attenuation >/= 40dB) -> 225mm
Example 2: F/UTP (Class C - Coupling Attenuation >/= 55dB)-> 114mm
Example 3: S/FTP (Class D - Coupling Attenuation >/= 80dB)-> 24mm
Relative to the shielded cable, the unshielded (U/UTP) separation distance between cable and power cable to further. In the implementation of the project, if need the data cable and power cable isolation far distance, we need a bigger size pipe/bridge, or even additional bridge, doing this will no doubt have higher cost, sometimes limited to the bridge installation space. To make matters worse, these additional requirements often neglected or ignored, resulting in network system is the key point of interference.
For shielded, unshielded systems and Fiber Cables, all need to implement protective grounding. Because of the need to consider personal and equipment safety, therefore no matter adopt what kind of cabling system, the metal part of the system must be grounded.
For the shielding system, also need to implement the functional ground. Grounded shielding system functions with respect to the implementation of non-shielded systems only difference is that when you install the module connector and the cable shielding mask area area connected.
Shielding system relative to the unshielded system has been greatly improved EMC performance. For Gigabit Ethernet applications, shielding against external interference effects is essential, and shielded cabling system had to meet the standards in the design of anti-alien crosstalk (A-XT) requirements, can effectively prevent the cable from the adjacent between the external crosstalk.
Date Submitted Fri. Aug. 16th, 2013 8:06 AM
Revision 1
Syntax Master claireling
Tags cable | Cabling | Copper | pair | twisted
Comments 0 comments
Currently, twisted-pair Copper Cabling is most ubiquitous, particularly UTP cabling, for For LAN and telephone installations. The main method to put connectors on twisted-pair cables is crimping. You use a tool called a crimper to push the metal contacts inside the connector onto the individual conductors in the cable, thus making the connection.
Firstly, we should know the types of twisted-pair cable connectors
Two main types of connectors/plugs are used for connectorizing twisted-pair cable in voice and data communications installations: the RJ-11 and RJ-45 connectors. Figure1 shows examples of RJ-11 and RJ-45 connectors for Twisted Pair Cable. Notice that these connectors are basically the same, except the RJ-45 accommodates more conductors and thus is slightly larger. Also note that the RJ-11 type connector shown in Figure1, while having six positions, is only configured with two metal contacts instead of six. This is a common cost-saving practice on RJ-11 type plugs when only two conductor contacts will be needed for a telephone application. Conversely, you rarely see an RJ-45 connector with less than all eight of its positions configured with contacts.

RJ-11 connectors, because of their small form factor and simplicity, were historically used in both business and residential telephone applications, and they remain in widespread use in homes. RJ-45 connectors, on the other hand, because of the number of conductors they support (eight total), are used primarily in LAN applications. Current recommendations are to install RJ-45 jacks for telephone applications because those jacks support both RJ-11 and RJ-45 connectors.

Both types of connectors are made of plastic with metal ¡°fingers¡± inside them (as you can see in Figure 1). These fingers are pushed down into the individual conductors in a twisted-pair cable during the crimping process. Once these fingers are crimped and make contact with the conductors in the twisted-pair cable, they are the contact points between the conductors and the pins inside the RJ-11 or RJ-45 jack.
Two versions RJ connectors are stranded-conductor and solid conductors
>>Stranded-conductor twisted-pair cables
Stranded-conductor twisted-pair cables are made up of many tiny hairlike strands of copper twisted together into a larger conductor. These conductors have more surface area to make contact with but are more difficult to crimp because they change shape easily. Because of their difficulty to connectorize, they are usually used as patch cables.
>>solid-conductor cables
Most UTP cable installed in the walls and ceilings between patch panels and wall plates is solid-conductor cable. Although they are not normally used as patch cables, solid-conductor cables are easiest to connectorize, so many people make their own patch cords out of solidconductor

Tools for Connector Crimping
The first tool you¡¯re going to need is a Cable Jacket Stripper, as shown in Figure 2. It will only cut through the outer jacket of the cable, not through the conductors inside. Many different kinds of cable strippers exist, but the most common are the small, plastic ones that easily fit into a shirt pocket. They are cheap to produce and purchase.

Another tool you¡¯re going to need when installing connectors on UTP or STP cable is a cable connector crimper. Many different styles of Cable Crimping Tools can crimp connectors on UTP or STP cables. Figure3 shows an example of a crimper that can crimp both RJ-11 and RJ-45 connectors.
Notice the two holes for the different connectors and the cutting bar.


The last tool you¡¯re going to use is a cable tester. This device tests for a continuous signal from the source connector to the destination and also tests the quality of that connection
Installing the Connector
Now we¡¯ll go over the steps for installing the connectors. Pay particular attention to the order of these steps(shown in Figure 4)and be sure to follow them exactly.
Equipment from some manufacturers may require you to perform Warnin g slightly different steps. Check the manufacturer¡¯s instructions before installing any connector.

Check to ensure all conductors are making contact and that all pins have been crimped into their respective conductors. If the connector didn¡¯t crimp properly, cut off the connector and redo it.
Date Submitted Mon. Jul. 22nd, 2013 7:55 AM
Revision 1
Syntax Master claireling
Tags cable | fiber | multiplexer | optic | optical | pair | twisted
Comments 0 comments
Sharing the transmission medium

You are the network manager of a company. You have a Source-User link requirement given to you. In response you install a premises fiber optic data link. However, the bandwidth requirements of the specific source users to adapt to the source for bandwidth speed requirements, is much, much less than is available from the fiber optic data link. The tremendous bandwidth of the installed optical fiber cable is being wasted. On the surface, this is not an economically efficient installation.

You want to prove that the install link to the controller of the company, the person who comment on your budget. The controller don't understand the attenuation benefits of fiber optic cable. The controller doesn't understand the interference benefits of fiber optic cable. The controller hates waste. He just wanted to see most of the bandwidth of the fiber optic cable used waste nothing. There is a solution to this problem. Don't just put the huge bandwidth of optical fiber cable, a single, specific, the source user communication needs. Instead, allow it to be shared by a multiplicity of
Source-User requirements. It allows it to carve a multiplicity of fiber optic data links out of the same fiber optic cable.

The technique used to bring about this sharing of the fiber optic cable among a multiplicity of Source-User transmission requirements is called multiplexing. It is not particular to the fiber optic cable. It happens in any transmission medium, such as wire, microwave, etc., the available bandwidth far surpasses any individual Source-User requirement. However, multiplexing is particularly attractive is a fiber optic cable transmission medium.

Conceptually, multiplexing as shown in figure 1. This figure shows the "N" Source-User pairs indexed as 1, 2, ... There is a multiplexer provided at each end of the fiber optic cable. The multiplexer on the left takes the data provided by each of the source. It combines these data steams together and sends the resultant steam out on the fiber optic cable. Such a single source to generate data flow sharing the fiber optic cable. The multiplexer on the left performs what is called a multiplexing or combining function. The right of the multiplexer takes the combined stream put out by the fiber optic cable. It separates the combined stream into the individual Source streams composing it. It directs each of these component steams to the corresponding User. The multiplexer on the right performs what is called a demultiplexing function.

A few things should be noted about this illustration shown in Figure 1.

Figure 1: Conceptual view of Multiplexing. A single fiber optic cable is "carved" into a multiplicity of fiber optic data links.

First, the Transmitter and Receiver are still present even though they are not shown. Device is considered to be part of the fiber optic multiplexer is on the left and the receiver are considered to be part of the multiplexer is on the right.

Secondly, the Sources and Users are display close to the multiplexer. Multiplexing to understand this is a common situation. Connectioin from the source to the multiplexer and multiplexer to User is called a tail circuit. If the tail circuit is too long a separate data link may be needed just to bring data from the Source to the multiplexer or from the multiplexer to the User. The cost of this separate data link may counter any savings effected by multiplexing.

Thirdly, the link between the multiplexer, the link in this case realized by the fiber optic cable, is termed the composite link. This is the link, the transportation is by all of the source of the river alone.

Finally, sepatate users are shown in figure 1. However, it may be only user provide separate ports and source of all the common user communication. There may be a change in this. The source user does not need all of the same type. They may be completely different types of data devices serve different applications and different speed requirements.

Within the context of premise data communications a typical situation where the need for multiplexing arises is illustrated in figure 2. This shows a cluster of terminals. In this case there are six terminals. All of these terminals are fairly close to one another. All are at a distance from and want to communicate with a multi-user computer. This can be a multi-use PC or a mini-computer. This situation may arise when all of the terminals are co-located on the same floor of an office building and the multi-user computer is in a computer room on another floor of the building.

The communication connection of each of these terminals could be effected by the approach illustrated in figure 3. Here each of the terminals are connected to a dedicated port at the computer by a separated cable. The cable could be a twisted pair cable or a fiber optic cable. Of course, the six cables are required and the bandwidth of each cable may far exceed the terminal to computer speed requirements.

Figure 2: Terminal cluster isolated from multi-user computer
Figure 3: Terminals in cluster. Each connected by dedicated cables to multi-user computer

Figure 4: Terminals sharing a single cable to multi-user computer by multiplexing

A more economically efficient way of communication connection as shown in figure 4. Here each of the six terminals are connected to a multiplexer. The data streams from these terminals are collected by the multiplexer. The streams are combined and then sent on a single cable to another multiplexer located near the multi-user computer. This second multiplexer separates out the individual terminal data streams and provides each to its dedicated port. The connection going from the computer to the terminals is similarly handled. The six cables shown in figure 3 has been replaced by the single composite link cable shown in figure 4. Cable cost has dropped significantly. Of course, this comes at the cost of two multiplexers. Yet, if the terminals are in a cluster the tradeoff is in the direction of a net decrease in cost.

There are two techniques for carrying out multiplexing on fiber optic cable in the premise environment. These two techniques are Time Division Multiplexing (TDM) and Wavelength Division Multiplexing (WDM). These techniques are described in the sequel. Examples of specific products to

implement these technologies are introduced. These products are readily available from FiberStore.

Time Division Multiplexing (TDM) with Fiber Optic Cable

With TDM a multiplicity of communication links, each for a given Source - User pair, share the same fiber optic cable on the basis of time. The multiplexer set up a continuous sequence of time using the clock. The duration of the period depends on a number of different engineering design factors; most notably the needed transmission speeds for the different links. Each communication link assigned a specific time period, TDM channel, during this period it is allowed to send its data from the source to the client. At this time there is no other link allows sending data. The multiplexer in source side receiving data from the source is connected to it. Then load the data from each source to the TDM channel accordingly. In multiplexer uninstall from each channel at the end of the user data and sends it to the corresponding user.

Wavelength Division Multiplexing (WDM) With Fiber Optic Cable

With WDM a multiplicity of communication links, each for a given Source-User pair, share the same fiber optic cable on the basis of wavelength. The data steam from each source is assigned an optical wavelength. The multiplexer has within it the modulation and transmission processing circuitry. The multiplexer modulates each data stream from each source. After the modulation process the resulting optical signal generated for each source data stream is placed on its assigned wavelength. The multiplexer then couples the totality of optical signals generated for all source data streams into the fiber optic cable. These different wavelength optical signals propagate simultaneously. This is in contrast to TDM.

The fiber optic cable is thereby carved into a multiplicity of data links - each data link corresponding to a different one of these optical wavelengths assigned to the Sources. At the user end the multiplexer receives these simultaneous optical signals. It separates these signals out according to their different wavelengths by using prisms. This constitutes the demultiplexing operation. The separated signal corresponding to the different source user data streams. These are further demodulation. The resulting data separated data streams are then provided to the respective users.
Date Submitted Sat. Mar. 6th, 2010 9:13 PM
Revision 1
Scripter Cloudgen
Tags Expression | HTML | pair | Regular
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This is the perfect regular expression for extracting a pair of html tags. For details, please seeThe regular expression for selecting a pair of HTML tag