  Nodal links are special configurations of band degeneracies in the momentum
space, where nodal line branches encircle each other. In PT symmetric systems,
nodal lines can be topologically characterized using the eigenvector frame
rotations along an encircling loop and the linking structure can be described
with non-Abelian frame charges interacting among adjacent bands. In this paper,
we present a photonic multiple nodal links system, where non-adjacent band
topology is proposed to characterize the hidden relation between nodal lines
from non-adjacent band pairs. Through an orthogonal nodal chain, the nodal line
from the lower two bands predicts the existence of nodal lines formed between
the higher bands. We designed and fabricated a metamaterial, with which the
multiple nodal links and non-adjacent band topology are experimentally
demonstrated.
