{HEAD ~ The structure} includes {TAIL ~ a first polymeric sleeve} having a refractive index numerically lower than the refractive index of the exterior cylindrical surface of the glass core 
{ HEAD ~ The structure } includes { TAIL ~ a first polymeric sleeve } having a refractive index numerically lower than the refractive index of the exterior cylindrical surface of the glass core
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH