A new design of segmented cladding fiber (SCF) was proposed and fabricated in silica glass. The silica glass SCF had a central core and hexagonal wings with higher refractive indices than silica cladding. The proposed SCF was analyzed numerically in terms of the confinement loss and the effective mode area using finite element method (FEM). In experiments, SCF preform was prepared by a stack-and-draw method using two types of pre-drawn rods: silica rods for the cladding and Al-doped silica rods for the higher refractive index segments and the central core. The latter was fabricated in the powder in tube (PIT) process by optimizing the heating cycles and the bubble removal during the sintering process. Light guidance along the SCF was experimentally confirmed and its intensity patterns in the near-field at the wavelengths 0.980 μm and 1.550 μm were characterized. With the proposed SCF, all silica SCF fabrication feasibility was confirmed, which can open a new alternative for large mode area fibers.

Design and fabrication of a segmented cladding fiber (SCF) which is a large mode area fiber with granulated silica based on stacking and two-time drawing technique is proposed in this article.

In this work, we have proposed and optimized a segmented cladding fiber (SCF) with a large mode area (LMA) consisting of a uniform core and a double cladding. The outer cladding of the SCF consisted of a periodic alternation of high- and low-refractive-index segments, while the inner cladding consisted of a resonant layer of rods surrounded by high-refractive-index rings. The three geometrical parameters chosen as design variables were the (a) doped rod refractive index differences, (b) refractive index differences of rings, and (c) ring thickness. Using the Box–Behnken approach, we selected thirteen different design cases and modeled them numerically using the finite element method (FEM). In order to optimize the features of the proposed fiber, such as the effective mode area (EMA), we applied response surface methodology (RSM). The EMA of the optimal SCF was significantly improved and markedly enlarged to about 706 µm² at a wavelength of 1.550 µm. Different properties of the optimized double-cladding octo-wing SCF (DC-OW-SCF), such as confinement losses in the core mode and the first higher-order mode, were studied. The DC-OW-SCF offers the advantages of feasibility in fabrication using the powder-in-tube (PIT) method and provides the possibility of utilization in compact amplifier devices and high-power fiber lasers.