The time delay unit also includes a reflecting element for reflecting the optical signal back to the dispersive element along an optical path {HEAD ~ whose length} is {TAIL ~ a function} of the angle 
is
The time delay unit also includes a reflecting element for reflecting the optical signal back to the dispersive element along an optical path { HEAD ~ whose length } is { TAIL ~ a function } of the angle
OTH OTH OTH 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 REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH