A signal having a predetermined pattern is written in a predetermined region of an optical disc at {TAIL ~ a plurality} of {HEAD ~ different write power levels} Pwm 
A signal having a predetermined pattern is written in a predetermined region of an optical disc at { TAIL ~ a plurality } of { HEAD ~ different write power levels } Pwm
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH