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