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