A gel or fluid with a refractive index close to that of the fiber core, about 1.46, placed between two fiber ends in mechanical splices and some prepolished connectors. By removing the glass-to-air interface it cuts the roughly 4 percent Fresnel reflection to a small fraction. A dab at the far end of a fiber also kills end reflections that create OTDR ghosts.
Put a drop of index-matching gel on the far end so that reflection stops throwing ghosts on the trace.
Also heard as
- index-matching fluid
- index gel
- matching gel
Related terms
Mechanical splice
A joint that holds two cleaved fiber ends together in an alignment device with index-matching gel, no arc needed.
Reflectance
The fraction of light reflected by a single event such as a connector, in dB, where more negative is better.
Ghost
A false event on an OTDR trace caused by a strong reflection bouncing back and forth in the fiber.