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