  Temperature ($2.3<T<40$\ K) and magnetic field ($0<B<17$\ T) dependent far
infrared absorption spectroscopy on the spin-Peierls coumpound CuGeO$_3$\ has
revealed several new absorption processes in both the dimerised and high field
phase of CuGeO$_3$. These results are discussed in terms of the modulation of
the CuGeO$_3$\ structure. At low fields this is the well known spin-Peierls
dimerisation. At high fields the data strongly suggests a field dependent
incommensurate modulation of the lattice as well as of the spin structure.
