The structure 2 wherein the index of refraction of the guiding core is smaller than the index of {HEAD ~ refraction} of {TAIL ~ the surrounding distributed gratings} 
of
The structure 2 wherein the index of refraction of the guiding core is smaller than the index of { HEAD ~ refraction } of { TAIL ~ the surrounding distributed gratings }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL