Bend-resistant octo-wing silica segmented cladding fiber with high index rings

Abstract

We have proposed a novel segmented cladding fiber (SCF) design and the bending effects were investigated in detail. The proposed SCF with large mode area properties has a uniform circular core and octo-wings of rods with higher refractive index than the silica segments in the cladding. While the high index octo-wings improved the waist of the electrical field distribution of the fundamental mode (FM), the lower index segments enabled SCF to be bend-resistant. We numerically investigated the light guiding properties through the proposed SCF by using finite element method with a perfectly matched layer. SCF was investigated in terms of effective mode area, confinement loss in bent state and it was shown that the proposed SCF is insensitive to the bending angle. By applying high index rings around the rods in octo-wings and optimizing the structure, we obtained an effective mode area as large as 715 µm2 at the wavelength of 1.55 µm with a relatively large loss ratio between FM and first higher order mode of about 137. Effective single mode operation was achieved at a tight bending radius of 10 cm over a wide wavelength range from 1 µm to 1.7 µm. The novel proposed SCF gives the advantages of fabrication feasibility by the method of powder-in-tube process. Octo-wing SCF could be applied for compact amplifiers and high power fiber lasers.