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