Microscopic distortions where the fiber is pressed against a rough or uneven surface, from cable crush, over-tight cable ties, poor cabling or the jacket shrinking in cold weather. Each one is minute but they add up along the fiber, raising attenuation, often more at longer wavelengths. Loss that appears in winter and disappears in summer points to microbending in the cable.
That loss only shows up when it drops below freezing, I'm betting microbend where the cable is crushed under the tie-wraps.
Hook-and-loop straps instead of plastic ties in racks and trays remove the most common source of microbend loss indoors.
Also heard as
- microbending
Do not mix it up with
- Macrobend: A macrobend is a visible bend of the whole fiber; a microbend is a tiny local distortion caused by pressure.
Related terms
Macrobend
A bend in a fiber tight enough to see, which lets light escape the core and causes loss.
Attenuation
The gradual loss of optical power as light travels along a fiber, expressed in decibels.
Loose-tube cable
Outside plant cable whose fibers float inside gel-filled or dry tubes, protecting them from strain and temperature changes.