Optical Fiber Telecommunications VA, 5th Edition

40 W while the fiber with reduced acousto-optic overlap (LMA-2) showed a threshold

of between 150 and 200 W. This measurement clearly demonstrates the feasibility of

raising the SBS threshold through dopant profiling in the core of the fiber. Further-

more with the LMA-2 fiber, a fiber laser slope efficiency of over 80% has been

measured, demonstrating that such profiling provides uncompromised laser perfor-

mance. Record high-power, narrow-linewidth fiber amplifiers have also been demon-

strated with this SBS-managed fiber design, and the details are given in Ref. [107].

15.5.5 Conclusions

Vapor-doping, all-glass, double-clad fiber processes have been established through

the OVD method. The major benefits of such processes include ultralow loss,