Five turns of the multimode launch jumper around a mandrel whose diameter is chosen for the core size and jacket. The bends strip the loosely guided high-order modes that an LED or overfilled source launches, approximating the encircled flux launch condition that cabling standards assume. Without it, multimode loss measurements read too high and vary from tester to tester.
Your multimode numbers are all a half dB high, did you put the mandrel wrap on the launch jumper?
Also heard as
- mandrel
Related terms
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.
OLTS
Optical Loss Test Set: a light source and power meter used together to measure end-to-end link loss.
One-jumper reference
A loss-test reference set with a single launch jumper between source and meter, so both link end connectors are counted.
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.