Copper Media and Connectors
Twisted pair cable: pairs of wires twisted together to reduce electromagnetic interference (EMI) and crosstalk. UTP (Unshielded Twisted Pair): no additional shielding — flexible, cost-effective, most common for LAN cabling. STP (Shielded Twisted Pair): foil or braid shielding on pairs or the overall cable — used in high-interference environments (near motors, industrial equipment). Connector: RJ-45 (8-pin modular connector). Used for 10BASE-T, 100BASE-TX, 1000BASE-T (Gigabit Ethernet), 10GBASE-T.
Category ratings: Cat5e (1 Gbps, 100m), Cat6 (1 Gbps/100m, 10 Gbps/55m), Cat6a (10 Gbps, 100m), Cat7/8 (40 Gbps+, used in data centers). Maximum segment length: 100 meters (328 feet) for standard Ethernet. Exceeding this causes signal degradation — attenuation and crosstalk errors.
Coaxial cable: center conductor, dielectric insulator, braided shield, outer jacket. Types: RG-6 (cable TV, satellite, broadband internet), RG-58 (old Thin Ethernet 10BASE-2). Connectors: F-type (cable TV/broadband), BNC (legacy networking, video). Coax is rarely used for modern LAN but appears on the exam for legacy context.
RJ-11: 6-pin connector, used for analog telephone lines (POTS), DSL. Smaller than RJ-45 — can be physically inserted into an RJ-45 port but won't work correctly. DB-9 / RS-232: serial console connector, legacy — used for console access to older routers and switches.
Fiber Optic Media and Connectors
Multimode fiber (MMF): larger core (50 or 62.5 microns). Shorter distances — up to 550m for Gigabit Ethernet, up to 400m for 10GbE OM4. Uses LED or VCSEL light sources (lower cost). Orange or aqua jacket. OM1, OM2, OM3, OM4, OM5 grades — higher numbers = better performance at longer distances. OM5 supports wideband multimode (multiple wavelengths) for higher throughput.
Single-mode fiber (SMF): smaller core (8–10 microns). Much longer distances — km to hundreds of km. Uses laser light sources (higher cost). Yellow jacket. Used for campus, metro, and WAN connections. OS1 (tight-buffered, indoor) and OS2 (loose-tube, outdoor) grades.
Fiber connectors: LC (Lucent Connector): small form factor, used in SFP/SFP+ transceivers, data center — most common modern connector. SC (Subscriber Connector/Standard Connector): square snap-in connector, older installations. ST (Straight-Tip): bayonet-style twist-lock, older campus fiber. FC: threaded, used in telecommunications. MTP/MPO: multi-fiber push-on connector — holds 12 or 24 fibers in one connector, used for high-density data center fiber trunk cables.
Fiber polishing: PC (Physical Contact), UPC (Ultra PC), APC (Angled Physical Contact). APC connectors have a green color coding and an 8-degree angled end-face that reduces back-reflection — required for CATV and long-haul links. APC and UPC connectors are NOT compatible despite having the same physical shape.
Transceivers and Media Converters
SFP (Small Form-factor Pluggable): hot-swappable transceiver module that fits in an SFP port. Can be fiber (single-mode or multimode at various wavelengths) or copper (1000BASE-T). Allows one hardware platform to support multiple media types. SFP+ supports 10 Gbps. QSFP (Quad SFP) supports 40 Gbps. QSFP28 supports 100 Gbps. QSFP56 supports 200 Gbps.
DAC (Direct Attach Copper) cables: SFP+ or QSFP at each end, connected by a passive copper cable. Cost-effective for short data center connections (1–7 meters). AOC (Active Optical Cables): SFP+ with embedded optical transceiver and fiber — longer reach than DAC, lighter than individual fiber + transceiver.
Media converter: converts between different media types — copper to fiber, or multimode to single-mode fiber. Used when connecting legacy copper equipment to a fiber uplink, or when two fiber types must interoperate. Transparent to higher layers.