Precompensation of the thermal-induced refractive index changes into a fully aperiodic LPF for heat load resilience

In this paper, a strategy consisting in pre-compensating the thermal-induced transverse refractive index changes is undertaken to push further the appearance threshold of a multimode regime. First, a standard air-silica Large Pitch Fiber and a Fully-Aperiodic Large Pitch Fiber are confronted in regard to their heat load resilience and capabilities for singlemode emission. Thereafter, slight refractive index depressions are judiciously introduced into the active core area. This approach enhances the delocalization of the high-order modes even under severe heat load levels. This combination of aperiodic cladding microstructuration and index-pre-compensation theoretically increases the multimode regime threshold while preserving large mode field areas. This investigation is performed at 1.03 and 2μm operating wavelengths.