Shop talk for the visible red laser of a VFL, as in throw red light on it or put red light down that fiber. Crews use it to trace jumpers through crowded panels, check continuity on short runs and spot the glow from a bad connector or kinked cord in a tray. It only reaches a few kilometers and does not show faults inside opaque cable.
Heard on the job
Throw red light on fiber 23 from the hut, I'll tell you which pigtail lights up in the cabinet.
Also heard as
- VFL
Related terms
VFL
Visual Fault Locator: a bright red laser pen that shows breaks, bends and bad connectors as visible glowing points.
Macrobend
A bend in a fiber tight enough to see, which lets light escape the core and causes loss.
Fiber identifier
A clip-on tester that detects light in a fiber through a gentle bend, without cutting it or interrupting traffic.