Specialty Optical Fibers Handbook

of the guided light, which penetrate into the cladding, the optical properties of

the materials of the cladding still have an influence on the overall fiber trans-

mission characteristics, but these optical properties become much less of a

constraint. In particular, the overall losses or nonlinearities of the fiber can

now be orders of magnitude smaller than the intrinsic losses and nonlinearities

of the solid materials used to manufacture the fiber. It has been predicted, for

example, that hollow-core silica fibers could someday lead to even lower trans-

mission losses [6] than solid-core silica fibers, whose losses—0.2 dB/km at

l ¼ 1:55 mm—are already extremely low. Similarly, the high-peak-power mater-

ial breakdown can now be shifted to much