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