Transmission Media
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The document explains the concept of transmission media, which refers to substances that propagate energy waves, either through guided mediums like cables or unguided methods like wireless transmission. It describes various types of wired media such as twisted pair wires, coaxial cables, and fiber optic cables, alongside unguided media that utilize antennas. Key distinctions are made between the usage and characteristics of wired versus wireless media, emphasizing their applications in telecommunications.
Transmission Media
- 1. TRANSMISSION MEDIA A GUIDED AND UNGUIDED APPROACH TO INTERNET…
- 2. TRANSMISSION MEDIUM • A transmission medium is a material substance (solid, liquid, gas, or plasma) that can propagate energy waves. For example, the transmission medium for sounds is usually a gas, but solids and liquids may also act as a transmission medium for sound. • The absence of a material medium in vacuum may also constitute a transmission medium for electromagnetic waves such as light and radio waves. While material substance is not required for electromagnetic waves to propagate, such waves are usually affected by the transmission media they pass through, for instance by absorption or by reflection or refraction at the interfaces between media. • The term transmission medium also refers to a technical device that employs the material substance to transmit or guide waves. Thus, an optical fiber or a copper cable is a transmission medium. Not only this but also is able to guide the transmission of networks. • Electromagnetic radiation can be transmitted through an optical medium, such as optical fiber, or through twisted pair wires, coaxial cable, or dielectric-slab waveguides. It may also pass through any physical material that is transparent to the specific wavelength, such as water, air, glass, or concrete. Sound is, by definition, the vibration of matter, so it requires a physical medium for transmission, as do other kinds of mechanical waves and heat energy.
- 3. TRANSMISSION AND TELECOMMUNICATION • A physical medium in data communications is the transmission path over which a signal propagates. • Many transmission media are used as communications channel. • For telecommunications purposes in the United States, transmission media are classified as one of the following: 1. Wired (or guided)—waves are guided along a solid medium such as a transmission line. 2. Wireless (or unguided)—transmission and reception are achieved by means of an antenna.
- 4. CLASSES OF TRANSMISSION MEDIA • Wired or guided media • Use a conductor such as a wire or a fiber optic cable to move the signal from sender to receiver. • Examples include telephone networks, cable television or internet access, and fiber-optic communication. • Wireless or unguided media • Use radio waves of different frequencies and do not need a wire or cable conductor to transmit signals. • Examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mice, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones.
- 5. GUIDED OR WIRED TRANSMISSION MEDIA Twisted Pair Wires • Consists of two insulated copper wires arranged in a regular spiral pattern to minimize the electromagnetic interference between adjacent pairs Coaxial Cable (or Coax) • Used for cable television, LANs, telephony Fiber Optic Cable • Relatively new transmission medium used by telephone companies in place of long- distance trunk lines
- 6. TWISTED PAIR WIRES • Consists of two insulated copper wires arranged in a regular spiral pattern to minimize the electromagnetic interference between adjacent pairs • Often used at customer facilities and also over distances to carry voice as well as data communications • Low frequency transmission medium • Types of Twisted Pair: • STP (shielded twisted pair) The pair is wrapped with metallic foil or braid to insulate the pair from electromagnetic interference • UTP (unshielded twisted pair) Each wire is insulated with plastic wrap, but the pair is encased in an outer covering
- 7. COAXIAL CABLE (OR COAX) • Used for cable television, LANs, telephony • Has an inner conductor surrounded by a braided mesh • Both conductors share a common center axial, hence the term “co-axial” • Coax Advantages: • Higher bandwidth • 400 to 600Mhz • up to 10,800 voice conversations • Can be tapped easily (pros and cons) • Much less susceptible to interference than twisted pair • Coax Disadvantages: • High attenuation rate makes it expensive over long distance • Bulky
- 8. FIBER OPTIC CABLE • Relatively new transmission medium used by telephone companies in place of long-distance trunk lines • Also used by private companies in implementing local data communications networks • Require a light source with injection laser diode (ILD) or light-emitting diodes (LED) • Fiber Optic Types: • Multimode step-index fiber • the reflective walls of the fiber move the light pulses to the receiver • Multimode graded-index fiber • acts to refract the light toward the center of the fiber by variations in the density • Single mode fiber • the light is guided down the center of an extremely narrow core
- 9. UNGUIDED OR WIRELESS TRANSMISSION MEDIA • Transmission and reception are achieved by means of an antenna • Directional • Transmitting antenna puts out focused beam • Transmitter and receiver must be aligned • Omni-Directional • Signal spreads out in all directions • Can be received by many antennas • Wireless Examples : • Terrestrial Microwave • Satellite Microwave • Broadcast Radio • Infrared
- 10. TERRESTRIAL MICROWAVE • Used for long-distance telephone service • Uses radio frequency spectrum, from 2 to 40 Ghz. • Parabolic dish transmitter, mounted high • Used by common carriers as well as private networks • Requires unobstructed line of sight between source and receiver • Curvature of the earth requires stations (repeaters) ~30 miles apart
- 11. SATELLITE MICROWAVE • Television distribution • Long-distance telephone transmission • Private business networks • Satellite Microwave Transmission • A microwave relay station in space • Can relay signals over long distances • Geostationary Satellites • Remain above the equator at a height of 22,300 miles (geosynchronous orbit) • T0ravel around the earth in exactly the time the earth takes to rotate • Satellite Transmission Works • Earth stations communicate by sending signals to the satellite on an uplink • The satellite then repeats those signals on a downlink • The broadcast nature of the downlink makes it attractive for services such as the distribution of television programming
- 12. RADIO • Radio is omnidirectional and microwave is directional. • Radio is a general term often used to encompass frequencies in the range 3 kHz to 300 GHz. • Mobile telephony occupies several frequency bands just under 1 GHz. • Repeaters need to be placed after few miles.
- 13. INFRARED • Uses transmitters/receivers (transceivers) that modulate noncoherent infrared light. • Transceivers must be within line of sight of each other (directly or via reflection ). • Unlike microwaves, infrared does not penetrate walls.
- 14. Thank You Presented By: Hemant Sarthak