The SOAs are operated in {HEAD ~ a co ordinated switching mode} to route {TAIL ~ the corresponding channel} selectively to at least one of the multiplexers, and may also contribute gain 
to route
The SOAs are operated in { HEAD ~ a co ordinated switching mode } to route { TAIL ~ the corresponding channel } selectively to at least one of the multiplexers , and may also contribute gain
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH