Fiber LIEKKITM Yb1200-20/125DC LIEKKITM Yb1200-20/125DC-PM Optical Peak Cladding Absorption at 976 nm (nominal) dB/m 29 30 Cladding Absorption at 920 nm dB/m 6.8 ± 1.7 7.1 ± 1.7 Core Numerical Aperature 0.08 ± 0.01 0.08 ± 0.01 Birefringence > 8.0E-05 Geometrical and Mechanical Core Diameter μm 20 ± 2 20 ± 2 Core Concentricity Error μm < 1.5 0.46 > 0.46 Proof Test Kpsi > 100 > 100