In another embodiment, {HEAD ~ an optical fiber} is provided with {TAIL ~ reflective gratings} , each of which are reflective at different wavelengths 
is provided with
In another embodiment , { HEAD ~ an optical fiber } is provided with { TAIL ~ reflective gratings } , each of which are reflective at different wavelengths
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH