Specialty Optical Fibers Handbook

many applications in spectroscopy and frequency conversion, for materials

processing, the line width is less important and the threshold can be increased

considerably.

7.7.2 Methods to Improve Performance

7.7.2.1 Core Design

For both SBS and SRS impairments, as well as other limits like four-wave

mixing and self-phase modulation, mitigation is possible by increasing the modal

area and decreasing the fiber length. To increase mode area, the core diameter

can be increased while the core index is decreased to maintain single-mode

operation. For example, a core with Dn ¼ 0:0012 will remain single mode at

1060 nm up to core diameter of about 20 mm. At such a low core index, the fiber

becomes sensitive to external perturbations, which can cause excessive