The scattering effect could be observed at time of
collision between photon and a molecule of the material of
the optical fiber. Approximately one thousandth (10 -3) of
the optical power contributes to the elastic collisions. During
the elastic collision the energy of the molecule and the
photon is not changed (in Fig. 2 denoted E) and the wavelength
of the incident light does not change. This leads to
the Rayleigh scattering. Rayleigh scattering behaves like
a lot of point sources, because it emits the light into all angles.
Considerably smaller part of the power (cca 10-8)
contributes to the nonelastic collisions. During the nonelastic
collision the incident photon transmits some part of
energy to the molecule of the material or receives some
energy from the molecule. Regarding to the fact, that
energy of the photon corresponds with its frequency, transmission
or acceptance of energy leads to changes in
frequency and wavelength of the light. This phenomenon is
called Raman scattering [1], [2].