The model used is essentially that used in Part I, modified by the introduction of anisotropic optical properties associated with the chain links. Equations are derived for the differences of principal polarizabilities for the biaxially strained network. These are evaluated by numerical computation, as in part I. The variations of polarizability differences with strain are found to follow a very similar pattern to the corresponding principal stresses. Comparisons are made also with the Gaussian optical theory and with a simplified `3-chain' non-Gaussian model analogous to that of James & Guth. The theory predicts one important effect not derivable from the simpler theories.