The percentage of {HEAD ~ crossover points} of the exposed sacrificial fiber channels is preferably {TAIL ~ 25 to 75%, most preferably 30 to 50%} 
The percentage of { HEAD ~ crossover points } of the exposed sacrificial fiber channels is preferably { TAIL ~ 25 to 75 % , most preferably 30 to 50 % }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL