The 250 µm acrylate coating applied to fiber at the draw tower, and by extension the bare coated fiber found inside loose tubes and ribbons. Splicers say two-fifty to tell it apart from nine hundred, the 900 µm tight-buffered fiber in indoor cable, because the two need different holders, strippers and sometimes connectors. Some high-count cables use thinner 200 µm coatings.
Pigtails are nine hundred but the cable side is two-fifty, so swap the fiber holders before you start burning.
Also heard as
- 250 micron
Do not mix it up with
- Buffer: The coating is the thin layer on the glass; a tight buffer is a thicker 900 µm plastic jacket extruded over that coating.
Related terms
Buffer
The protective plastic layer or tube around coated fiber, either a tight 900 µm jacket or a loose gel-filled tube.
Loose-tube cable
Outside plant cable whose fibers float inside gel-filled or dry tubes, protecting them from strain and temperature changes.
Cladding
The layer of slightly lower-index glass around the core that keeps light trapped inside it.
Strip, clean, cleave
The three-step fiber prep routine done before every splice or splice-on connector.