Mandrels (for use with an LED source only) - DTX Fiber Test Kit

ANSI/TIA/EIA-568-B.1 mandrel guidelines
The mandrel diameter and number of mandrel wraps is specified in TIA/EIA-568-B.1 clause 11.3.3. The diameter varies depending upon the fiber core size and launch cable diameter.

Short link lengths of multimode optical fiber may appear to have higher than expected attenuation due to the power lost in the high-order modes. To remove high-order mode transient losses from multimode optical fiber measurements when using a source that excites these transient high-order modes, the reference jumper should be wrapped in five non-overlapping turns around a smooth round mandrel (rod) during the reference calibration of the source to the detector and for all loss measurements. The mandrel diameter depends on fiber core size and shall be as specified in table 11-15 (shown below). 
TIA/EIA-568-B-compliant multimode mandrels for 3 mm test jumpers are available for purchase from Fluke Networks. 


Place mandrels on the testers output fiber, as shown in the reference diagram (Figure 2). 

.. and the test connection diagram (Figure 3).