Specialty Optical Fibers Handbook

mitigated by introducing the depressed cladding feature to the waveguide design.

A careful study shows that the matched cladding design can be reoptimized for

improved macrobending loss performance using the higher effective D to pull the

field into the core for a slightly smaller MFD of 8:8 mm, while using a depressed

cladding to maintain the cable cutoff less than 1260 nm.

2.5.2 Phenomenology of Macrobending Loss

Macrobending occurs in a large deflection of the fiber axis, where large is

defined relative to the fiber core diameter, such as that associated with spooling

or the presence of loops. The resulting loss consists of the transition loss and

pure bending loss [25, 26]. The transition loss occurs at the transitions from

straight to bent sections ...