fiber optic cables (what you NEED to know) // FREE CCNA // EP 13

About this video

In episode 13 of his free CCNA series, the creator explains fiber optic cables using the AT&T fiber connection to his own home, which he says gives him gigabit (1,000 Mbps) internet. Fiber carries data as light pulses instead of electrical signals, giving speed close to light (he notes light in fiber runs about 31% slower than in a vacuum because of refraction), very low attenuation over distance, and no electromagnetic interference. He explains the cable’s structure — a core surrounded by cladding of about 125 microns, plus strengthening material and a jacket — and how total internal reflection at the critical angle keeps light bouncing inside the core. The two types are contrasted: multimode fiber has a larger core of 50 to 62.5 microns, light bounces around inside it, and it suits shorter in-building runs; his OM3 multimode example is rated for 300 metres at 10 Gbps. Single-mode fiber has a much smaller core of 5 to 9 microns, light travels straight through, and it can run up to 100 kilometres (about 60 miles) with higher bandwidth, making it the choice for building-to-building, campus, provider and undersea links (with repeaters). Ethernet still wins on cost, ease of termination and universal RJ45 ports, and fiber cannot carry Power over Ethernet. Practical points include connector types — LC (most common in his experience), SC and ST — duplex cables with separate transmit and receive strands, colour coding (yellow usually single-mode, aqua or orange multimode), and SFP ports on switches that accept interchangeable modules for fiber or RJ45.

Key takeaways

• Fiber uses light pulses, giving very high speed, low attenuation over long distances, and immunity to electromagnetic interference compared with copper Ethernet
• Multimode fiber (50-62.5 micron core) is cheaper and used for shorter in-building runs; single-mode (5-9 micron core) goes far — up to 100 km per the creator — and carries more bandwidth
• Light stays in the core via total internal reflection, with the cladding keeping it from escaping; never kink or sharply bend fiber, as it breaks and cannot be easily re-terminated
• Ethernet persists because it is cheaper, easy to make and terminate, universally supported via RJ45, and can deliver Power over Ethernet, which fiber cannot
• Match connectors to your gear (LC, SC, ST), note duplex cables have separate send/receive strands, and use SFP modules to add fiber ports to switches

Episode details: published May 30, 2021 · 19:08 long. Summary written by Self Growth Videos from the episode itself. Business results and any income figures mentioned are NetworkChuck’s own claims, shared for education — they are not typical or guaranteed.

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