By matching the phases, {TAIL ~ the light} from the coupler is input to the fiber traveling in a circular direction, i.e., the path of the light down the fiber forms {HEAD ~ a corkscrew} 
By matching the phases , { TAIL ~ the light } from the coupler is input to the fiber traveling in a circular direction , i.e. , the path of the light down the fiber forms { HEAD ~ a corkscrew }
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH 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