Airstream Gate 5 Fiber Optic Practice Test 2026 – Complete Exam Prep

The outer protective layer in many fiber optic cables is the jacket. This outermost covering shields everything inside—the delicate glass fiber, buffer coating, and any strength members—from moisture, chemicals, abrasion, and everyday handling. It’s designed to withstand environmental conditions and provide a durable, fire-rated enclosure, using materials like PVC or flame-retardant polymers.

Inside the jacket, the primary buffer coating sits directly around the glass fiber to cushion it and reduce microbending and stress. Aramid strength members, such as Kevlar, run along the length to provide tensile strength and prevent breaking when the cable is pulled. The outer shield, when present, adds electromagnetic shielding or extra protection, but it is not what most cables rely on for the main outer protection—that role belongs to the jacket.