{HEAD ~ A proportionate signal} may be split off from each channel and taken to {TAIL ~ a photodetector} to enable the gain of the associated SOAs to be adjusted to equalize or otherwise balance the signal levels 
taken to
{ HEAD ~ A proportionate signal } may be split off from each channel and taken to { TAIL ~ a photodetector } to enable the gain of the associated SOAs to be adjusted to equalize or otherwise balance the signal levels
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH REL REL 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