a laser optically coupled to {TAIL ~ said first light input} via a first optical fiber and optically coupled to said second light input via {HEAD ~ a second optical fiber} 
a laser optically coupled to { TAIL ~ said first light input } via a first optical fiber and optically coupled to said second light input via { HEAD ~ a second optical fiber }
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD