In this way the total optical path length of {HEAD ~ the signal} in {TAIL ~ the time delay unit} depends on its optical wavelength 
In this way the total optical path length of { HEAD ~ the signal } in { TAIL ~ the time delay unit } depends on its optical wavelength
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH