In sum, the total time that it takes {HEAD ~ the optical signal} to travel from the input element to {TAIL ~ the output element} depends on its wavelength 
In sum , the total time that it takes { HEAD ~ the optical signal } to travel from the input element to { TAIL ~ the output element } depends on its wavelength
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH