{HEAD ~ The method} 12, further comprising affixing the birefringent displacer on {TAIL ~ a mounting frame} with respect to an optical path of the input beam after the minimum PDL is found 
{ HEAD ~ The method } 12 , further comprising affixing the birefringent displacer on { TAIL ~ a mounting frame } with respect to an optical path of the input beam after the minimum PDL is found
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH