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