The high-index center of the fiber that guides the light, surrounded by lower-index cladding so rays striking the boundary at shallow angles reflect back inward by total internal reflection. Core diameter defines the fiber family: about 9 µm for singlemode, 50 or 62.5 µm for multimode. Most connector and splice loss comes down to how well two cores line up and how closely their sizes match.
Splicer's showing the cores offset on the Y axis, clean the V-grooves and redo it before you heat the sleeve.
Also heard as
- fiber core
Do not mix it up with
- Cladding: Cladding is the 125 µm glass layer around the core that keeps the light inside it; it does not carry the signal.
Related terms
Cladding
The layer of slightly lower-index glass around the core that keeps light trapped inside it.
Singlemode fiber
Optical fiber with a core so small that light travels in a single path, used for long-haul, metro, FTTH and campus backbones.
Multimode fiber
Fiber with a 50 or 62.5 µm core that carries many light paths at once, used for short links inside buildings and data centers.
Mode field diameter
The effective width of the light spot traveling in a singlemode fiber, slightly larger than the physical core.
Numerical aperture
A measure of how wide a cone of light a fiber can accept and guide, written as a number such as 0.20.
Same word, different worlds
Fully cured laminate with copper on both sides, etched into inner layers and bonded with prepreg into a multilayer.
Concrete & CementA cylinder of hardened concrete drilled out of a structure to test its strength or inspect its condition.
Asphalt PavingA cylinder of pavement drilled out of the finished mat and sent to the lab for density and thickness.
NonwovensTube, usually paperboard, on which nonwoven fabric is wound to make a roll.