Patent ID: 7760977

Claim:
A step-index optical fiber composed of multicomponent glass, comprising: a lanthanum-containing core glass having a circumferential wall; and a cladding glass completely enclosing said lanthanum-containing core glass on said circumferential wall; said lanthanum-containing core glass having a material composition, containing: SiO 2 from 42 to 60% by weight; ZnO from 20 to 38% by weight; Na 2 O <14% by weight; K 2 O <12% by weight; Na 2 O + K 2 O ≧2% by weight; La 2 O 3 from >0 to 10% by weight; and BaO ≦0.9% by weight; said cladding glass having a material composition, containing: SiO 2 from 60-72% by weight; B 2 O 3 <20% by weight; Al 2 O 3 <10% by weight; Na 2 O <18% by weight; K 2 O <15% by weight; Li 2 O <5% by weight; and F ≦1% by weight.