Use the wrong fiber cable in the wrong environment and you are setting yourself up for premature failures, water damage, and irritated customers. Outdoor and indoor cables look similar at a glance, but the construction differences are significant. Choosing correctly depends on where the cable runs, what hazards it faces, and how it is terminated.
Outdoor Cable Types: Armored, Aerial, and Direct Burial
Outdoor cables must handle UV exposure, temperature swings, moisture, and physical stress. The three main outdoor variants are loose-tube, armored, and self-supporting aerial cables.
Loose-Tube Cables
The most common outdoor cable. Fibers sit loosely inside gel-filled or dry-water-blocking tubes. The loose buffer means temperature changes don't transfer stress to the fiber itself. Gel-filled versions need cleaning before splicing. Dry-block versions cost slightly more but save prep time. For long outdoor runs between buildings, loose-tube is the default choice.
Armored Cables
When the cable runs through areas with rodent activity or risk of accidental digging, armor is your friend. Steel tape or corrugated steel armor sits between the cable core and the outer jacket. It adds weight and stiffness but prevents rodents from chewing through to the fibers. Pair armored cables with the 96-core splice closure at transition points for a watertight, rodent-resistant solution.
Self-Supporting Aerial Cables
For pole-to-pole installations, figure-8 cables with an integral messenger wire eliminate the need for a separate lashing strand. These handle wind loading and ice buildup better than lashed cables. The messenger wire takes the tensile load; the fiber core hangs below, protected from direct UV exposure by the jacket.
Indoor Cable Types: Tight Buffer and Distribution
Inside buildings, fire codes matter more than water ingress. Indoor cables use tight-buffer construction where a thermoplastic coating surrounds each fiber directly. This makes the cable stronger per-fiber and easier to connectorize.
Tight-Buffer Cables
Each 900-micron tight-buffered fiber can be terminated directly with a connector — no breakout kit needed. This saves time in data center and building riser installations. Tight-buffer cables are available in plenum (OFNP) and riser (OFNR) ratings. Plenum-rated jackets emit low smoke and are required for air-handling spaces like dropped ceilings.
Distribution Cables
For shorter runs within a floor or between patch panels in the same room, distribution cables group multiple tight-buffered fibers under a single jacket. They are smaller and more flexible than breakout cables but less rugged. The 12-port wall-mount terminal box works well for indoor distribution cable termination points.
Converting from Outdoor to Indoor
When outdoor cable enters a building, transition at the demarcation point. A splice closure or wall-mount box on the outside wall handles the splice from outdoor loose-tube to indoor tight-buffer cable. Inside, SC/APC patch cords from the SC/APC patch cable line connect the termination panel to your OLT or ONT equipment.
Quick Selection Guide
Between buildings or down a street: loose-tube outdoor cable. Through a field or rodent-prone area: armored loose-tube. Pole to pole: self-supporting aerial. Inside a building riser: tight-buffer riser-rated. Inside a dropped ceiling: tight-buffer plenum-rated. Between racks in the same room: distribution cable or pre-terminated patch cords.
