Understanding Data Transmission Mediums: Twisted Pair, Coaxial, Fiber Optics, and Wireless
1. Twisted Pair Cable
Twisted pair cable consists of two conductors, usually copper, each with its own plastic insulation, twisted together. One cable carries signals to the receiver, and the other acts as a signal ground reference. Twisting the cables helps balance the impact of interference and noise, as it ensures both cables are equally affected by external sources.
Types of Copper Twisted Pair
- UTP (Unshielded Twisted Pair): The most common type, lacking additional shielding.
- FTP (Foiled Twisted Pair): Includes a foil shield surrounding each pair of conductors for improved noise reduction.
- STP (Shielded Twisted Pair): Developed by IBM, features a woven mesh shield around each pair, offering superior noise protection but at a higher cost and bulk.
Categories of Twisted Pair Cable
Twisted pair cables are categorized based on their quality and performance, ranging from Category 1 (lowest) to Category 7 (highest).
- Category 1: Basic cable used in telephone systems.
- Category 2: Unshielded twisted pair, originally used in T-type lines.
- Category 3: Improved Category 2, used in LANs.
- Category 4: Enhanced Category 3, used in Token Ring networks.
- Category 5: 24 AWG cable with a jacket and shield.
- Category 5e: Extended Category 5 with features to minimize noise and electromagnetic interference.
- Category 6: A newer category adhering to specific manufacturer components.
- Category 7: Sometimes called SSTP (Screened Shielded Twisted Pair), offers superior shielding for reduced interference and increased data speeds.
2. Coaxial Cable
Coaxial cable consists of a central conductor surrounded by a shield. It can carry higher frequency signals than twisted pair cable.
- Coaxial cables are classified by Radio Government (RG) ratings.
- Common types include RG-59 (cable TV), RG-58 (thin Ethernet), and RG-11 (thick Ethernet).
- Connectors include BNC, BNC-T, and BNC terminator.
Coaxial cables are used in cable TV networks and traditional Ethernet networks.
3. Fiber Optics
Fiber optic cables consist of an inner glass or plastic core surrounded by cladding and an outer sheath. They transmit data as light signals, which propagate through the core via reflection.
Advantages:
- Resistance to noise
- Low attenuation
- High bandwidth
Disadvantages:
- Unidirectional light propagation
- Cost
Fiber optic cables are used in backbone networks, cable TV networks, and fast Ethernet networks.
4. Wireless Communication
Types of Propagation
Wireless data transmission occurs through surface spreading, sky spreading, and line-of-sight propagation. Wireless waves are classified as radio waves, microwaves, or infrared.
- Radio waves are omnidirectional.
- Microwaves are unidirectional.
Microwaves are used for mobile phones, satellite communications, and wireless LANs.
Microwave
Microwaves are electromagnetic waves with frequencies between 1 and 300 GHz. They are unidirectional and require aligned transmitting and receiving antennas. Microwave antennas are typically parabolic dishes or horn antennas.
Microwaves are used in unicast communications, including mobile phones, satellite networks, and wireless networks.
Infrared
Infrared waves are used for short-range communication, such as between a PC and a peripheral or within an internal LAN.
Key Features:
- Direct reflection
- Use of transducers that modulate noncoherent infrared light
- Require line-of-sight or direct reflection
- Cannot penetrate obstacles
- Fast installation, no permit required
- Unsuitable for open environments due to weather interference