An optical assembly is provided that can mitigate thermal damage that could otherwise occur in the region near where the optical fiber emerges from a high-power optical device package. The optical assembly includes an optical medium to guide stray light, along the fiber axis but substantially outside of the fiber core, from the interior to the exterior of a housing. The assembly further includes a transition region external to the housing, where at least one optical mode guided by the optical medium transitions to at least one optical mode confined by a polymer coating as a guided mode of the cladding. In embodiments, the optical medium is provided by the fiber cladding together with overlying materials of relatively low refractive index that help to confine the stray light within the cladding.