sensors for identifying types of {HEAD ~ the installed optical parts} which have been installed in {TAIL ~ the main equipment}; and 
installed in
sensors for identifying types of { HEAD ~ the installed optical parts } which have been installed in { TAIL ~ the main equipment } ; and
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH