what is physical medium

Want to build rock-solid networks? Start with the cables. Network physical media are the highways for data. They connect our computers, routers, switches, and servers in the digital world. These transmission channels operate in the Physical Layer. This is the first layer of the OSI framework. They fall into two main types: guided systems that use physical cables and unguided wireless transmissions. When choosing the best option for your needs, consider these factors: how far your signal travels, the amount you’re sending, environmental issues that could disrupt the signal, your budget, and the layout your network needs.

This hands-on guide covers the basics of modern networking hardware. It starts with simple twisted pairs, then moves to fast fiber optics and advanced wireless tech. We’ll dig into specs, real-world uses, pros, cons, and where the industry’s headed next. Whether you’re setting up a small office LAN, building wide-area networks (WANs), or configuring data center setups, mastering these basics is key. It can turn a network that just works into one that performs.

Network Foundations: How Physical Media Works

At their core, physical transmission media simply provide pathways for digital information. These pathways come in different forms. Some carry electrical pulses through metal. Others transmit light beams through glass strands. Wireless options use electromagnetic radiation in open air. The media you choose affects three key parts of your network’s performance: speed, reliability, and distance. Let’s break down the main options:

• Metal-Based Conductors: Your workhorses, like twisted pairs and coax, that push data via electrical signals
• Glass/Plastic Light Pipes: Fiber optic cables send information as pulses of light
• Air-Based Transmission: Wireless systems broadcasting data through electromagnetic waves

Each approach has its sweet spot. Metal cables deliver affordable solutions when covering shorter distances. Fiber optics shine (literally) in scenarios demanding massive bandwidth over long hauls. Wireless options bring freedom and flexibility but face their own set of interference hurdles compared to hardwired alternatives.

Copper cable Media

Types of cable include unshielded twisted-pair (UTP), shielded twisted-pair (STP), and coaxial cable. Copper-based cables are inexpensive and easy to work with compared to fiber-optic cables. Still, as you’ll learn when we get into the particulars, the main disadvantage of copper cable is that it offers a limited range that cannot handle advanced applications.

The most commonly used physical media for data communications is cabling (copper media), which uses copper wires to send data and control bits between network devices. Cables used for data communications generally consist of individual copper wires from circuits dedicated to specific signaling purposes. There are three main types of copper media used in networking:

• Unshielded Twisted-Pair (UTP)
• Shielded Twisted-Pair (STP)
• Coaxial

The above cables interconnect computers on a LAN and other devices such as switches, routers, and wireless access points. Each type of connection and the associated devices have cabling requirements specified by physical layer standards. The physical layer standards also specify the use of different connectors for different types, the mechanical dimensions of the connectors, and the acceptable electrical properties of each type.

Guided Media: Wired Networking Solutions

Guided media use physical cables to direct data signals along a specific path. These are the most common media in enterprise networks, data centers, and home LANs due to their reliability and high performance.

Unshielded Twisted Pair (UTP)

Unshielded twisted-pair (UTP) cabling is the most common networking media for voice and data communications. UTP cable consists of four pairs of color-coded wires that have been twisted

Together, they are encased in a flexible plastic sheath that protects them from minor physical damage. Twisting wires helps decrease electromagnetic and radio-frequency interference induced from one wire to the other.

UTP cabling is terminated with RJ-45 connectors for interconnecting network hosts with intermediate networking devices, such as switches and routers. In the figure, the color codes identify the individual pairs and wires and help in cable termination.

• Characteristics:
  • Cost: Inexpensive and easy to install.
  • Bandwidth: Varies by category (e.g., Cat5e supports up to 1 Gbps, Cat6 up to 10 Gbps).
  • Distance: Typically up to 100 meters.
  • Connectors: Uses RJ45 connectors for Ethernet networks.
  • Applications: Home and office LANs, Ethernet connections, VoIP systems.
• Advantages:
  • Cost-effective and widely available.
  • Easy to terminate and install.
  • Supports a range of data rates and standards.
• Disadvantages:
  • Susceptible to EMI in high-interference environments.
  • Limited distance compared to fiber optics.

Shielded Twisted-Pair Cable(STP)

Shielded twisted-pair (STP) cabling provides better noise protection than UTP cabling. However, STP cables are more expensive and difficult to install. Like UTP cables, STP uses an RJ-45 connector.

The extra covering in shielded twisted pair wiring protects the transmission line from electromagnetic interference leaking into or out of the cable. STP cabling is often used in Ethernet networks for, speedy data rate.

Shielded twisted-pair (STP) cables also combine shielding to counter EMI and RFI and wire twisting to counter crosstalk. To take full advantage of the shielding, STP cables are also terminated with special shielded STP data connectors. If the cable is improperly grounded, the shield may act as an antenna and pick up unwanted signals.

• Characteristics:
  • Cost: More expensive than UTP due to shielding.
  • Bandwidth: Similar to UTP but with better noise resistance.
  • Distance: Up to 100 meters.
  • Connectors: Uses shielded RJ45 or other specialized connectors.
  • Applications: Fast Ethernet, Token Ring, industrial networks.
• Advantages:
  • Superior noise resistance.
  • Suitable for high-speed Ethernet in noisy environments.
• Disadvantages:
  • Higher cost and installation complexity.
  • Less flexible than UTP.

Categories of Twisted Pair Cables

Twisted pair cables are classified based on their performance specifications, defined by the TIA/EIA-568 standards. Below is a summary of common categories:

Category	Max Data Rate	Max Bandwidth	Applications
Cat1	Voice only	1 MHz	Telephone lines (POTS)
Cat3	10 Mbps	16 MHz	Early Ethernet (10BASE-T)
Cat5	100 Mbps	100 MHz	Fast Ethernet
Cat5e	1 Gbps	100 MHz	Gigabit Ethernet
Cat6	10 Gbps (55m)	250 MHz	Gigabit Ethernet, 10GBASE-T
Cat6a	10 Gbps (100m)	500 MHz	10GBASE-T, data centers
Cat7	40 Gbps (50m)	600 MHz	High-speed networks, emerging use
Cat8	40 Gbps (30m)	2000 MHz	Data centers, 25G/40GBASE-T

Note: Cat5, Cat3, and earlier categories are outdated for modern networks, while Cat7 and Cat8 are gaining traction in high-performance environments.

Coaxial Cable

Coaxial cables consist of a central copper conductor surrounded by a shield, insulation, and an outer jacket. They were widely used in early LANs (e.g., 10BASE2, 10BASE5) but have largely been replaced by twisted pair and fiber optics in modern networks.

Structure and Types

• Components:
  • Core: A copper conductor that carries signals.
  • Insulation: Separates the core from the shield to prevent short circuits.
  • Shield: A braided or foil layer that protects against EMI.
  • Jacket: An outer layer for physical protection.
• Types:
  • Thinnet (10BASE2): Thin coaxial cable (RG-58), used in early Ethernet networks, with a maximum segment length of 185 meters and 10 Mbps speed.
  • Thicknet (10BASE5): Thicker coaxial cable (RG-8), with a maximum segment length of 500 meters and 10 Mbps speed.
  • RG-6: Used in broadband and cable TV, with higher bandwidth than Thinnet/Thicknet.

Applications in Networking

• Historical Use: Coaxial cables were used in bus topologies for early Ethernet networks (1980s–1990s).
• Modern Use: Primarily in cable TV, broadband internet (HFC networks), and some legacy installations.
• Advantages:
  • High bandwidth for broadband applications.
  • Good resistance to EMI due to shielding.
  • Supports longer distances than UTP in some cases.
• Disadvantages:
  • Difficult to install and less flexible.
  • Largely obsolete for modern LANs.
  • Susceptible to lightning damage in outdoor setups.

Fiber Optics Cable Media

Fiber Optic cable is another type of physical media. It offers huge data bandwidth, protection against many types of noise and interference, and enhanced security.

So, fiber provides clear communications and a comparatively noise-free environment. The disadvantage of fiber is that it is costly to purchase and it requires specialized equipment and techniques for installation.

Properties of Fiber-Optic Cabling

Fiber optic cable can send data over long distances with higher bandwidths than any other networking media. It can also send signals with less attenuation and is totally protected from EMI and RFI. OFC is generally used to connect network devices.

Fiber optic cable is flexible but very thin—a transparent strand of very pure glass, not bigger than a human hair. Bits are encoded on the fiber as light impulses. The fiber-optic cable acts as a waveguide or “light pipe” to send light between the two ends with minimal signal loss.

As an analogy, consider an empty paper towel roll with the inside coated like a mirror. It is a thousand meters long, and a small laser pointer sends a Morse code signal at the speed of light. Essentially, that is how a fiber-optic cable operates, except that it is smaller in diameter and uses advanced light technologies.

Fiber-optic cabling is now being used in four types:

• Enterprise Networks: Used for backbone cabling and interconnecting infrastructure devices.
• Fiber-to-the-Home: Used to give always-on broadband services to homes and small businesses.
• Long-Haul Networks: The service providers use this type to connect countries and cities.
• Submarine Networks provide reliable, high-speed, high-capacity solutions that survive in harsh undersea environments up to transoceanic distances.

Fiber Optic Cable Structure

The optical fiber is composed of two kinds of glass (core and cladding) and a protective outer shield (jacket), shown in Figure 3-8.

Core

The core is the light transmission element at the center of the optical fiber. This core is typically silica or glass. Light pulses travel through the fiber core.

Cladding

It is made from slightly different chemicals than those used to make the core. It behaves like a mirror by reflecting light into the fiber’s core, keeping the light in the core as it travels down the fiber.

Buffer

Used to help shield the core and cladding from damage.

Strengthening Member

The buffer surrounds the fiber cable, preventing it from stretching out when it is pulled. The material used is often the same as that used to manufacture bulletproof vests.

Jacket

Typically, a PVC jacket protects the fiber against abrasion, moisture, and other contaminants. This outer jacket composition can vary depending on cable usage.

Types of Fiber Media

Light pulses instead of the transmitted data as bits on the media are generated by either:

• Lasers
• Light-emitting diodes (LEDs)

Electronic semiconductor devices called photodiodes detect the light pulses and convert them to voltages. The laser light transmitted over fiber-optic cabling can damage the human eye. Care must be taken to avoid looking into the end of active optical fiber. Fiber-optic cables are mostly classified into two types:

• Single-mode fiber (SMF): its core is very small and uses very expensive laser technology to send a single ray of light, as shown in Figure Popular, in long-distance situations spanning hundreds of kilometers, such as those required in long-haul telephony and cable TV applications. The following are single-mode cable characteristics.
  • Small core
  • Less dispersion
  • Use laser as the light source
  • Suited for long-distance application
  • Commonly used with campus backbone for the distance of several thousand meters.

• Multimode fiber (MMF): Its core is very large, and this cable type uses LED emitters to send light pulses. Specifically, light from an LED enters the multimode fiber at different angles, as shown in Figure 3-10. They are popular in LANs because they are powered by low-cost LEDs. It provides bandwidth up to 10 Gb/s over link lengths of up to 550 meters. Following are single-mode cable characteristics.
• Larger core than single-mode cable
• Uses LEDs as the light source
• Allows more excellent dispersion and, therefore, loss of signal
• Suited for long-distance applications but shorter than single-mode
• Commonly used with LANs or distances of a couple of hundred meters within a campus network.

Unguided Media: Wireless Technologies

Wireless media include radio frequencies, microwave, satellite, and infrared. The deployment of wireless media is faster and less costly than cable deployment, primarily when there is no existing infrastructure. There are a few disadvantages associated with wireless. It supports much lower data rates than wired media. Wireless is also greatly affected by external environments, such as the impact of weather, and reliability can be difficult to guarantee. It carries data through electromagnetic signals using radio or microwave frequencies.

Wireless media provides the best mobility options, and the number of wireless-enabled devices continues to increase. As network bandwidth options increase, wireless is quickly gaining in popularity in enterprise networks, and it has some important points to consider before planning:-

• Coverage area: Wireless data communication technologies work well in open environments. However, certain construction materials used in buildings, structures, and the local terrain will limit effective coverage.
• Interference: Wireless is at risk of intrusion and can be disrupted by standard devices such as household cordless phones, fluorescent lights, microwave ovens, and other wireless communications.
• Security: Wireless communication coverage requires no access to a physical media strand. Thus, devices and users not authorized to access the network can access the transmission. Network security is the main component of wireless network administration.
• Shared medium: WLAN works in half-duplex, which means just one device can be sent or received at a time. The wireless medium is shared among all wireless users. The more users need to access the WLAN simultaneously, the less bandwidth each user will need.

Types of Wireless Media

The IEEE and telecommunications industry standards for wireless data communications cover both the data link and physical layers. Cellular and satellite communications can also provide data network connectivity. However, we are not discussing these wireless technologies in this chapter. In each of these standards, physical layer specifications are applied to areas that include:

• Transmission Frequency
• The transmission power of the transmission
• Data to radio signal encoding
• Signal reception and decoding requirements
• Antenna design and construction

Wi-Fi is a trademark of the Wi-Fi Alliance. The certified product uses that belong to WLAN devices that are based on the IEEE 802.11 standards. Different standards are the following:-

WI-FI standard IEEE 802.11

WLAN technology is commonly referred to as Wi-Fi. WLAN uses a protocol called Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA). The wireless NIC must first listen before transmitting to decide if the radio channel is clear. If another wireless device is transmitting, the NIC must wait until the channel is clear. We will briefly discuss CSMA/CA.

Bluetooth standard IEEE 802.15

Wireless Personal Area Network (WPAN) standard, commonly known as “Bluetooth”, uses a device pairing process to communicate over distances from 1 to 100 meters.

WI-MAX Standard IEEE 802.16

Usually known as Worldwide Interoperability for Microwave Access (WiMAX), a point-to-multipoint topology gives wireless broadband access.

Wireless LAN (WLAN)

General wireless data implementation, wireless LAN requires the following network devices:

• Wireless Access Point (AP): In a wireless local area network (WLAN), an access point (AP) is a station that transmits and receives data. An access point also connects users to other users within the network and can serve as the interconnection point between the WLAN and a fixed wire network. Each access point can serve multiple users within a defined network area, so when people move beyond the range of one access point, they are automatically handed over to the next one. A small WLAN may only need a single access point; the number required increases the function of the number of network users and the physical size of the network.
• Wireless NIC adapters: Provide wireless communication ability to each network host.

As technology has developed, several WLAN Ethernet-based standards have emerged. Therefore, more care needs to be taken when purchasing wireless devices to ensure compatibility and interoperability.

The benefits of wireless data communications technologies are clear, notably the savings on costly premises wiring and the convenience of host mobility.

Comparison of Physical Media

The table below compares the key attributes of physical media to aid in decision-making:

Media Type	Max Data Rate	Max Distance	EMI Resistance	Cost	Applications
UTP	40 Gbps (Cat8)	100 m	Moderate	Low	LANs, Ethernet
STP	40 Gbps (Cat7)	100 m	High	Moderate	Industrial LANs
Coaxial (Thinnet)	10 Mbps	185 m	High	Moderate	Legacy LANs
Coaxial (RG-6)	1 Gbps+	500 m+	High	Moderate	Broadband, HFC
SMF	100 Gbps+	40 km+	Complete	High	WANs, data centers
MMF	10 Gbps	2 km	Complete	High	LANs, data centers
Radio Waves (Wi-Fi)	7 Gbps (Wi-Fi 6)	100 m+	Low	Low	Home, office Wi-Fi
Microwave	1 Gbps+	45 km	Low	High	Backhaul links
Satellite	1 Gbps	Global	Low	Very High	Remote connectivity
Infrared	1 Gbps	10 m	Moderate	Low	Short-range devices

Standards and Specifications

Physical media are governed by standards to ensure interoperability and performance. Key standards include:

• TIA/EIA-568: Defines twisted pair categories (e.g., Cat5e, Cat6) and cabling standards.
• IEEE 802.3: Specifies Ethernet standards for twisted pair, coaxial, and fiber optic cables.
• ISO/IEC 11801: International standard for structured cabling.
• ANSI/TIA-942: Data center cabling standards, emphasizing fiber optics.
• ITU-T G.652: Defines SMF characteristics for telecommunications.

These standards ensure that cables and connectors meet performance requirements for modern networks.

Emerging Trends in Physical Media

1. Cat8 and Beyond: Cat8 cables support 25/40 Gbps over short distances, catering to data centers and high-performance computing.
2. 400G Ethernet: Fiber optics are evolving to support 400 Gbps and beyond, driven by cloud computing and 5G backhaul.
3. Wi-Fi 7 and 6G: Next-generation wireless technologies promise multi-gigabit speeds and lower latency.
4. Hybrid Fiber-Coaxial (HFC): Combining fiber and coaxial for broadband networks, offering high bandwidth with existing infrastructure.
5. Software-Defined Networking (SDN): Impacts physical media by requiring flexible, high-capacity cabling for dynamic network configurations.
6. Green Networking: Energy-efficient cables and wireless solutions to reduce power consumption in data centers.

Choosing the Right Physical Media

Selecting the appropriate physical media depends on several factors:

• Distance: Fiber optics for long distances, UTP for short-range LANs.
• Bandwidth: Fiber for high-bandwidth needs, UTP/STP for moderate needs.
• Environment: STP or fiber in high-EMI areas, wireless for mobility.
• Budget: UTP for cost-sensitive projects, fiber for future-proofing.
• Scalability: Fiber and Cat6a/Cat8 for growing networks.

For example, a small office might use Cat6 UTP for cost-effective Gigabit Ethernet, while a data center would opt for MMF or SMF for high-speed interconnects.

Installation and Maintenance Best Practices

1. Cabling Standards: Adhere to TIA/EIA-568 for proper cable installation and termination.
2. Cable Management: Use cable trays, labels, and patch panels to organize wiring.
3. Testing: Use certified cable analyzers to verify performance (e.g., Fluke testers for Cat6).
4. Avoiding Interference: Keep copper cables away from power lines and fluorescent lights.
5. Fiber Handling: Avoid bending fiber cables beyond their minimum bend radius.
6. Documentation: Maintain detailed records of cabling layouts for troubleshooting.

Conclusion

Physical media are the foundation of network connectivity, enabling data transmission across LANs, WANs, and data centers. From the cost-effective and versatile UTP cables to the high-bandwidth, long-distance capabilities of fiber optics, each media type serves unique purposes. Wireless technologies like Wi-Fi and 5G offer mobility, while emerging trends like Cat8 and 400G Ethernet push the boundaries of speed and scalability. By understanding the characteristics, applications, and standards of these media, network professionals can design robust, future-proof networks.