eee-1109 ECE-1109 Introduction to ECE Guided Transmission Mediums
1. Twisted-pair Cable
• Construction:
◦ Consists of separately insulated conductors.
◦ These conductors are twisted together.
◦ Often “bundled” into larger cables.
◦ Usually installed in buildings during construction.
◦ A typical twisted pair is made of solid copper wires with polyethylene sheathing. For example, a copper strand with a diameter of 0.4 mm is referred to as #26 on the American Wire Gauge (26 AWG).
• Applications:
◦ It is the most common transmission medium.
◦ Telephone networks.
▪ Specifically, it’s the fundamental medium for connecting homes to local exchanges (subscriber loops).
▪ Used within buildings for private branch exchanges (PBX).
◦ Local Area Networks (LANs), supporting speeds like 10Mbps or 100Mbps Ethernet.
◦ Utilized for Digital Subscriber Line (DSL) internet services. DSL service transmits high-speed data over twisted pairs to homes, approximating a wideband channel by a set of narrowband channels.
2. Coaxial Cable
• Construction:
◦ A guided physical medium for transmitting data signals.
◦ Its structure includes an inner conductor.
◦ Surrounded by an insulating layer.
◦ An outer conductor (shield), often a copper mesh.
◦ Followed by another insulating layer.
◦ And an outer plastic cover.
• Applications:
◦ A most versatile medium.
◦ Television distribution.
▪ From aerial to TV.
▪ For Cable TV services.
◦ Long-distance telephone transmission, historically capable of carrying up to 10,000 voice calls simultaneously, though it’s being replaced by fiber optic cable.
◦ Short-distance computer system links.
◦ Local area networks.
◦ Also serves as a typical channel for internet services.
3. Fiber-optic Cable
• Construction:
◦ A guided medium that transmits signals using light [Previous response].
◦ Typically consists of a glass or plastic core, surrounded by a cladding, and then a protective jacket [Previous response].
◦ Light travels through the core primarily via total internal reflection, which prevents it from being absorbed in the jacket [Previous response].
◦ Light sources for transmission can include Light Emitting Diodes (LEDs) or more efficient Injection Laser Diodes (ILDs) [Previous response].
• Applications:
◦ Extensively used in trunk lines, including metropolitan, rural exchange, and subscriber loops [Previous response].
◦ Employed in Local Area Networks (LANs) [Previous response].
◦ Crucial for high-speed data transmission in metro networks [Previous response].
◦ Forms the physical layer of global internet infrastructure, such as trans-Atlantic cables [Previous response].
◦ Often used in optical fiber communications today for laser-intensity modulation in Amplitude Shift Keying (ASK).