What Are Communication Cables?

Communication cables are physical transmission media used to carry electrical or optical signals between devices, systems, and networks. They form the foundational infrastructure of wired telecommunications, data networking, and signal distribution, enabling the transfer of voice, video, and data over distances ranging from a few meters to thousands of kilometers. Cables differ in their construction, bandwidth capacity, susceptibility to interference, and suitability for specific environments, making the choice of cable type a critical engineering decision in any networked system.

The principal categories of communication cable are twisted-pair copper, coaxial cable, and optical fiber. Each category reflects a different approach to the core problem of moving signals efficiently while minimizing losses and interference.

Twisted-Pair Copper Cable

Twisted-pair cable consists of pairs of insulated copper conductors wound around each other to reduce electromagnetic interference between adjacent pairs. Unshielded twisted pair (UTP) is the dominant medium for structured cabling in commercial buildings, supporting the Ethernet standards codified in IEEE 802.3 at data rates from 10 Mb/s to 40 Gb/s depending on cable category. Shielded twisted pair (STP) adds a foil or braid layer to further suppress crosstalk, making it preferable in electrically noisy industrial settings. The cabling categories defined by the ANSI/TIA-568 series, from Cat5e through Cat8, specify the frequency range, insertion loss, and return loss tolerances that govern which Ethernet speeds a given cable can reliably support.

Coaxial Cable

Coaxial cable uses a central copper conductor surrounded by a dielectric insulator, a braided metallic shield, and an outer jacket. The coaxial geometry keeps the signal contained within the shield, allowing it to carry radio-frequency signals with low radiation loss. This property made coaxial cable the medium of choice for cable television distribution and for early Ethernet installations, and it remains in widespread use for antenna feedlines and cable-modem access networks. The inner conductor and shield share the same geometric axis, the origin of the "coaxial" name, and the characteristic impedance of the cable, commonly 50 ohm for data and 75 ohm for video, is set by the ratio of the conductor and shield diameters.

Optical Fiber

Optical fiber transmits data as pulses of light through a glass or silica core surrounded by a cladding of lower refractive index, which confines the light by total internal reflection. Single-mode fiber uses a core diameter of approximately 9 micrometers, supporting transmission over distances of hundreds of kilometers at terabit-per-second aggregate capacities through wavelength-division multiplexing. Multi-mode fiber, with a core diameter of 50 or 62.5 micrometers, is suited to shorter-reach data-center and campus applications. Because fiber carries light rather than electrical current, it is immune to electromagnetic interference and ground-loop effects, which makes it the preferred medium for long-haul telecommunications backbones, submarine cables, and environments with high electrical noise. The ITU-T G-series recommendations specify fiber characteristics, splicing procedures, and measurement methods used throughout the industry.

Fault Location

Maintaining cable infrastructure requires the ability to detect and localize faults without physically tracing every meter of cable. For copper cables, time-domain reflectometry sends an electrical pulse down the cable and measures the reflection from an impedance discontinuity to compute the distance to a break or short. For optical fiber, optical time-domain reflectometry (OTDR) performs the analogous measurement using light pulses, and standards from the IEC define test procedures and acceptance criteria for installed fiber links.

Applications

Communication cables have applications across a wide range of fields, including:

• Broadband internet access via cable-modem and fiber-to-the-home deployments
• Enterprise and data-center structured cabling supporting Ethernet and storage-area networks
• Submarine cable systems linking continents for international voice and internet traffic
• Cable television distribution and hybrid fiber-coax access networks
• Industrial automation and process control wiring in factories and refineries