With the OEC, {HEAD ~ the optical signal} coupled thereon is converted into {TAIL ~ an electrical signal} 
With the OEC , { HEAD ~ the optical signal } coupled thereon is converted into { TAIL ~ an electrical signal }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL