Optical fiber

摘要

The present invention provides an optical fiber for use in fiber lasers and amplifiers wherein the optical fiber has a core member surrounded by a cladding member for receiving pump energy and transferring the pump energy to the core member. The optical fiber also has an outer layer surrounding the cladding member. The cladding member has a circular exterior periphery and a predetermined refractive index (nc). The cladding member has an index modified region that directs light to the core member. The index modified region has a stress field portion with a predetermined refractive index (ns). The difference between the refractive index of the cladding member and that of the stress field portion (nc - ns) is within such a range that the stress field portion does not affect the polarization properties of the light traveling in the core. Preferably, the difference between the refractive index of the cladding member and that of the stress field portion (nc - ns) is less than 10<-4>, and more preferably 10<-5>. <IMAGE>