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