Fiber dependence and coupling efficiency limitation for a lensed fiber integrated with a long period fiber grating

We analyze the fiber dependence and the efficiency limitation for optical coupling using a lensed fiber integrated with a long period fiber grating. In summary, the fiber dependence and the efficiency limitation is analyzed for optical coupling using a lensed fiber integrated with a long-period fiber grating (LPFG). We found that a dispersion-shifted fiber is more efficient for the proposed coupling scheme than a standard single-mode fiber. The coupling efficiency seems to be strongly reduced for a small beam waist owing to the effects of fiber truncation and spherical aberration. A high coupling efficiency may be obtained for the LD-to-fiber coupling scheme if a hyperbolic lensed fiber is used.