In a data communication system, a transmission medium is a physical path between the sender and the receiver. A transmission medium is divided into two types known as guided media and unguided media. For data cabling, we use guided media. Data cabling basically means cabling for all types of communication like networks, telecommunications, etc.
Guided media are broadly divided into three types: Twisted pair cable, Coaxial cable and Optical fiber.
Factors on which data cabling depends
- Bandwidth: Greater the bandwidth, higher is the data rate.
- Transmission impairment: Impairments such as noise limits the distance. This impairment is more in twisted pair cables than in coaxial cable than in optical fibers.
- Interference: Interloping due to noise or weather may wipe out a signal. It is caused due to close cable connections.
- Number of receivers: Guided media can be used for a point to point connection or a shared link with multiple attachments. Due to many attachments, the data rate decreases due to distortion and noise.
Twisted Pair Cable
- It consists of two insulated copper wires arranged in regular spiral fashion.
- A number of these pairs are bundled together into a cable by wrapping them into a though protective sheath.
- Twisting generally decreases the cross-talk interference.
- Twisted length typically varies from 2 to 6 inches. It has a thickness range of 0.016 to 0.036 inches.
- Mostly used in data cabling of telephone lines for offices with individual telephone sets.
- Can be used to connect all the telephones in a building.
- Also used for LAN supporting PCs.
- It is also used in DSL lines, used in telephone companies to achieve higher data rate.
- It can be used to transmit both digital and analog signal.
Coaxial Cable
- It consists of a single inner wire conductor surrounded by a hollow cylinder outside. The inner conductor is held in place by either regularly spaced insulation rings or a solid dielectric material.
- Because of the shield, it is much less susceptible to interference and crosstalk than twisted pair cable.
- It is widely used in television distribution. Long distance telephone transmission, short-run computer system links and LANs.
- This is also used for both analog and digital transmission.
- It has higher data rate because of its frequency.
- It is much less susceptible to interference.
- It is mostly affected by thermal noise and intermodulation noise.
- Amplifiers and repeaters are used for long-distance communication.
Optical Fiber
- It is a thin flexible medium capable of conducting an optical ray. It is cylindrical in shape. It has three sections which are concentric.
- This is mostly used for data cabling for long distance communication. The reasons are listed below:
- Small size and lighter weight
- Lower noise
- Electromagnetic isolation
- Greater repeater spacing
Categories of optical fibers are as follows
- Long Haul Trunks: These routes in an average of about 900 miles in length multiplexing 20,000 to 60,000 voice channels. It is an economic approach to connect trunk routes.
- Metropolitan Trunks: This has an average length of 7.8 miles and around 1 lac voice channels in a trunk group. Most facilities are installed in underground conduits and are repeater less joining telephone exchanges in a metropolis.
- Rural Exchange Trunks: Circuit lengths range from 25 to 100 miles that link towns and villages. Have less than 5000 voice channels.
- Subscriber loops: Fibers run directly from thecentralr exchange to the destination. These networks are capable of handling voice, data, images and videos.
- Local Area Network (LAN): A typical optical fiber LAN id FDDI (Fiber Distributed Data Interference) is mostly used for data cabling.
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