The Vital Role of Transmission Medium in Data Transmission

Transmission medium is the physical path between transmitter and receiver in a data transmission system.The characteristics and quality of data transmission are determined both by the characteristics of the signal.

Factors Effecting Data Communication Of Medium

Bandwidth:
All other factors remaining constant, the greater the bandwidth of a signal, the higher the data rate can be achieved.
Transmission Impairments:
Impairment, such as attenuation,
limit the distance. For guided media, twisted pair generally suffers more impairment than coaxial cable, which in turn suffers more than optical fiber.

Number of Receivers:

A guided media can be used to construct a point to point link or a shared link with multiple attachments.

Transmission media can be classified or unguided. In both cases, communication is in the form of electromagnetic waves. With guided media, the waves are guided along a solid medium, such as copper twisted pair, copper coaxial cable, and optical fiber. The atmosphere and outer space are examples of unguided media that provide a means of transmitting electromagnetic signals but do not guide them; this form of transmission is usually referred to as wireless transmission systems.

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Coaxial cable

CHARACTERISTICS OF COAXIAL CABLE
•Low cost
•Easy to install
•Up to 10Mbps capacity
•Medium immunity form EMI
•Medium of attenuation
ADVANTAGES COAXIAL CABLE
•Inexpensive
•Easy to wire
•Easy to expand
•Moderate level of EMI immunity
DISADVANTAGE COAXIAL CABLE
•Single cable failure can take down an entire network
Twisted Pair Cable

The most popular network cabling is Twisted pair. It is light weight, easy to install, inexpensive and support many different types of network.

It also supports the speed of 100 mps. Twisted pair cabling is made of pairs of solid or stranded copper twisted along each other. The twists are done to reduce vulnerably to EMI and cross talk. The number of pairs in the cable depends on the type. The copper core is usually 22-AWG or 24-AWG, as measured on the American wire gauge standard. There are two types of twisted pairs cabling

1. Unshielded twisted pair (UTP)
2. Shielded twisted pair (STP)
1. Unshielded twisted pair (UTP)
UTP is more common. It can be either voice grade or data grade depending on the condition. UTP cable normally has an impedance of 100 ohm. UTP cost less than STP and easily available due to its many use.

UTP
There are five levels of data cabling
Category 1
These are used in telephone lines and low speed data cable.
Category 2
These cables can support up to 4 mps implementation.
Category 3
These cable supports up to 16 mps and are mostly used in 10 mps.
Category 4
These are used for large distance and high speed. It can support 20mps.
Category 5
This is the highest rating for UTP cable and can support up to 100mps. UTP cables consist of 2 or 4 pairs of twisted cable. Cable with 2 pair use RJ-11 connector and 4 pair cable use RJ-45 connector. Characteristics of UTP

• low cost
•easy to install
•High speed capacity
•High attenuation
•Effective to EMI
•100 meter limit
Advantages of UTP
•Easy installation
•Capable of high speed for LAN
•Low cost
Disadvantages of UTP
•Short distance due to attenuation
2. Shielded twisted pair (STP)
It is similar to UTP but has a mesh shielding that’s protects it from EMI which allows for higher transmission rate.
STP
IBM has defined category for STP cable.
Type 1
STP features two pairs of 22-AWG
Type 2
This type include type 1 with 4 telephone pairs
Type 6
This type feature two pairs of standard shielded 26-AWG
Type 7
This type of STP consist of 1 pair of standard shielded 26-AWG Type 9
This type consist of shielded 26-AWG wire
Characteristics of STP
•Medium cost
•Easy to install
•Higher capacity than UTP
•Higher attenuation, but same as UTP
•Medium immunity from EMI
•100 meter limit
Advantages of STP:
•Shielded
•Faster than UTP and coaxial
Disadvantages of STP:
•More expensive than UTP and coaxial
•More difficult installation
•High attenuation rate

Fiber Optics

Fiber optic cable uses electrical signals to transmit data. It uses light. In fiber optic cable light only moves in one direction for two way communication to take place a second connection must be made between the two devices. It is actually two stands of cable. Each stand is responsible for one direction of communication. A laser at one device sends pulse of light through this cable to other device. These pulses translated into “1’s” and “0’s” at the other end. In the center of fiber cable is a glass stand or core. The light from the laser moves through this glass to the other device around the internal core is a reflective material known as CLADDING. No light escapes the glass core because of this reflective cladding.

Fiber optic cable has bandwidth more than 2 gbps (Gigabytes per Second) These cables are designed for long distance and very high bandwidth (gigabit speed) network communications. Fiber optic cables carry communication signals using pulses of light. While expensive, these cables are increasingly being used instead of traditional copper cables, because fiber offers more capacity and is less susceptible to electrical interference. So-called Fiber to the Home (FTTH) installations are becoming more common as a way to bring ultra high speed Internet service (100 Mbps and higher) to residences.

Characteristics Of Fiber Optic Cable:
•Expensive
•Very hard to install
•Capable of extremely high speed
•Extremely low attenuation
•No EMI interference
Advantages Of Fiber Optic Cable:
•Fast
•Low attenuation
•No EMI interference
Disadvantages Fiber Optics:
•Very costly
•Hard to install

TYPES

Simplex and Zip Cord: Simplex cables are one fiber, tight-buffered (coated with a 900 micron buffer over the primary buffer coating) with Kevlar (aramid fiber) strength members and jacketed for indoor use. The jacket is usually 3mm (1/8 in.) diameter. Zipcord is simply two of these joined with a thin web. It's used mostly for patch cord and backplane applications, but zipcord can also be used for desktop connections.

Distribution Cables: They contain several tight-buffered fibers bundled under the same jacket with Kevlar strength members and sometimes fiberglass rod reinforcement to stiffen the cable and prevent kinking. These cables are small in size, and used for short, dry conduit runs, riser and plenum applications. The fibers are double buffered and can be directly terminated, but because their fibers are not individually reinforced, these cables need to be broken out with a "breakout box" or terminated inside a patch panel or junction box.

Breakout Cables: They are made of several simplex cables bundled together. This is a strong, rugged design, but is larger and more expensive than the distribution cables. It is suitable for conduit runs, riser and plenum applications. Because each fiber is individually reinforced, this design allows for quick termination to connectors and does not require patch panels or boxes. Breakout cable can be more economic where fiber count isn't too large and distances too long, because is requires so much less labor to terminate.

Loose Tube Cables: These cables are composed of several fibers together inside a small plastic tube, which are in turn wound around a central strength member and jacketed, providing a small, high fiber count cable. This type of cable is ideal for outside plant trunking applications, as it can be made with the loose tubes filled with gel or water absorbent powder to prevent harm to the fibers from water. It can be used in conduits, strung overhead or buried directly into the ground. Since the fibers have only a thin buffer coating, they must be carefully handled and protected to prevent damage.

Conclusion

In summary,transmission media are essential for communication system.signals that carry information can be transmitted on a transmission medium for communication purposes.the transmission characteristics of a medium in use are important because they directly affect the communication quality.since different types of transmission media have different transmission characteristics and costs, they are used in different(and most suited) applications.

REFERNCES
https://docs.google.com/viewer?a=v&q=cache:_8qjoy1U02oJ: www.dia.unisa.it/~vitsca/RC-0809I/ch04.pdf+solved+term+paper+of+guided+transmission+media&hl=en&pid=bl&srcid=ADGEESgXCmFOkptqNN-4HzU7Y5gZ3qUDmtzeOT2xA3vOTe_IoJogr69nt0LC-lSB28imrCvBit9KDS2056mavHGzG6i2wrINVwBwHhWVuC1rBly1rIdRO01bYSJ13zJQZEcv3L7sG1pq&sig=AHIEtbRkgHpEjo6vjvjBjOtXTRifinR5XA.. http://www.studymode.com/essays/Transmission-Media-721773.html.. http://ninjacraze.hubpages.com/hub/Data-Communication.

http://www.slideshare.net/sourav894/transmission-media-2006854 http://compnetworking
.about.com/od/networkcables/g/fiberopticcable.htm
http://www.lanshack.com/fiber-optic-tutorial-cable.aspx