A hierarchical version including multiple star couplers and selection devices is also disclosed, to handle {TAIL ~ a relatively large number} of {HEAD ~ stations} 
A hierarchical version including multiple star couplers and selection devices is also disclosed , to handle { TAIL ~ a relatively large number } of { HEAD ~ stations }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD