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