{HEAD ~ A controller} is used for monitoring {TAIL ~ intensity} of the beam of light emerging from the optical switch and for providing a feedback signal to the phase shifters 
is used for monitoring
{ HEAD ~ A controller } is used for monitoring { TAIL ~ intensity } of the beam of light emerging from the optical switch and for providing a feedback signal to the phase shifters
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH