The mandrel wrap takes advantage of

The mandrel wrap takes advantage of the high loss of high-order modes caused by excessive bending of the optical ber. The mandrel wrap removes the high-order modes by inserting a series of macrobends in the transmit test jumper. Figure 33.29 shows the high-order modes in the core of the optical fiber refracting into the cladding because of a 90-degree macrobend.
The five small-radius nonoverlapping loops around the mandrel wrap shown in figure 33.27
significantly attenuate the high-order modes with minimal attenuation of the low-order modes. The mandrel wrap is actually a low-order or low-pass mode lter. It allows the low-order modes to pass with very little attenuation while greatly attenuating the high-order modes. The mandrel wrap should be on the transmit test jumper at every stage of testing when you’re making insertion loss measurements.