Cladding defects in hollow core fibers for surface mode suppression and improved birefringence Michieletto, M. ; Lyngsø, J. K. ; Lægsgaard, J. ; Bang, O. Abstract Publication: Optics Express Pub Date: September 2014 DOI: 10.1364/OE.22.023324 Bibcode: 2014OExpr..2223324M