Quick answer
XLPO stands for Cross-Linked Polyolefin. Like XLPE, the polymer chains are cross-linked into a thermoset, so the insulation resists heat, won't melt or drip, and lasts longer than ordinary PVC — but XLPO compounds are also formulated to be low-smoke and halogen-free for better fire safety.
It is used where both durability and fire performance matter. APAR's Mahashakti Round and Mahashakti Flat multicore cables use a specially developed XLPO compound.