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