In the present work we report an experimental investigation by electron paramagnetic resonance spectroscopy on the hyperfine structure of the E'<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$_\gamma$</EquationSource> </InlineEquation> point defect, probing the local arrangement of the network (range-II order), and by Raman spectroscopy on the D<Subscript>1</Subscript> and D<Subscript>2</Subscript> lines, probing mean...</subscript></subscript></equationsource></inlineequation>