In structured cabling and campus backbones, fibre-optic cable is often chosen to address which primary requirement when copper Ethernet reaches its physical limits?

Introduction / Context:
Choosing between copper and fibre is a design decision driven by distance, bandwidth, and environmental factors. Unshielded twisted pair (UTP) Ethernet links are typically limited to about 100 m per channel. When links need to span floors, buildings, or noisy conduits shared with power or telephone cabling, fibre-optic media become the preferred choice due to low attenuation and immunity to electromagnetic interference (EMI).

Given Data / Assumptions:

• Standard copper Ethernet (e.g., 1000BASE-T) is constrained to ~100 m per run.
• Backbone and inter-building links often exceed 100 m and traverse EMI-prone environments.
• Designers want reliable, high-bandwidth connectivity without repeaters every 100 m.

Concept / Approach:
Fibre offers orders-of-magnitude longer runs (hundreds of meters to tens of kilometers, depending on multimode or single-mode) and excellent EMI immunity because it carries light rather than electrical signals. This makes it ideal for building risers, campus backbones, and long horizontal runs that copper cannot support economically or reliably. While fibre prices have fallen, claiming it is “always cheaper” than UTP is inaccurate once optics and transceivers are included. Desktop drops within one room remain economical with copper, and dial-up analog WAN traffic is unrelated to fibre backbones.

Step-by-Step Solution:

Verification / Alternative check:
Standards such as 1000BASE-SX/LX and 10GBASE-SR/LR specify distances far beyond copper limits. Real-world deployments place fibre in risers and between buildings specifically to address distance and EMI, confirming the rationale.

Why Other Options Are Wrong:

• Cheaper in all cases: false; optics and transceivers add cost.
• Desktop wall outlets: copper is typically sufficient and economical for short runs.
• Dial-up analog lines: unrelated to fibre-based Ethernet backbones.
• Provide power over fibre: standard fibre does not deliver electrical power (PoE is for copper).

Common Pitfalls:
Assuming fibre is always more expensive or always cheaper; overlooking EMI in shared conduits; forgetting transceiver compatibility (SFP/SFP+ types, connector and modal considerations).

Final Answer:
Overcome distance limitations and electromagnetic interference