In example embodiments, {HEAD ~ the optical waveguide} and {TAIL ~ the optical input/output section} may transmit or receive an optical signal through the first optical window, the filler and the second optical window 
In example embodiments , { HEAD ~ the optical waveguide } and { TAIL ~ the optical input / output section } may transmit or receive an optical signal through the first optical window , the filler and the second optical window
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL 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 OTH