  Brillouin light scattering spectroscopy (BLS) is applied to study the
micromechanics of cellulosic viscose fibers, one of the commercially most
important, man-made biobased fibers. Using an equal angle scattering geometry,
we provide a thorough description of the procedure to determine the complete
transversely isotropic elastic stiffness tensor. From the stiffness tensor the
engineering-relevant material parameters such as Young's moduli, shear moduli,
and Poisson's ratios in radial and axial fiber direction are evaluated. The
investigated fiber type shows that, at ideal conditions, the material exhibits
optical waveguide properties resulting in spontaneous Brillouin backscattering
which can be used to obtain additional information from the Brillouin spectra,
enabling the measurement of two different scattering processes and directions
with only one scattering geometry.
