Specialty Optical Fibers Handbook

Conversely, as light travels up a taper from smaller to larger diameter (‘‘up’’

taper), the angle will decrease (Fig. 18.3). This is important when considering the

NA of the other components of the system and the desired output NA.

Laser systems, which produce high peak powers, can be difficult to couple

into fiber because of the high-power densities involved. Typically, the bulk fiber

material can withstand the high-power density, but the fiber end surface is the

weak link and may become damaged due to surface contamination, end-face

defects, or dielectric breakdown of the surrounding medium, initiating break-

down of the fiber surface. The degradation ...