Analysis of the optical and thermal characteristics of a hexagonally shaped six-core fiber for kilowatt-class amplifiers

The optical and thermal properties of six-core fibers with hexagonal geometry are numerically investigated to model high-power fiber amplifiers. Numerical simulations with finite element methods are conducted for two core/cladding/coating dimensions: 10/250/380 μm and 25/400/550 μm. To ensure independent amplification in all six channels, we define the conditions required for isolated-mode operation by adjusting core-to-core spacing. We then calculate the temperature distribution in these designs and identify the cooling requirements to maintain the coating temperature below 85 °C for thermally stable operation. The beam propagation and rate equations are solved to quantify the output-related heat generation along the fiber length. Under these thermal constraints, we analyze power scaling with respect to the convective heat transfer coefficient, identify its limitations, and compare performance for different cladding sizes to suggest approaches for improvement. Finally, we examine the amplifier’s power capacity under conduction cooling regimes.