As shown in the figure, {HEAD ~ a wave} 201 representing {TAIL ~ data} is trapped in a ring cavity 202 
representing
As shown in the figure , { HEAD ~ a wave } 201 representing { TAIL ~ data } is trapped in a ring cavity 202
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH