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