A geometrical optics approach to scattering from an optical fiber side
-illuminated by a laser beam at oblique incidence is presented. Our ap
proach describes the interference pattern appearing in a region center
ed at a scattering angle of 180 degrees from the direction of the inci
dent beam. It will be shown that there exists a critical incidence ang
le for which a bright spot in the pattern of backscattered light arise
s.