  The optical activity in a helically-coiled optical fiber is reexamined. It is
proven that not only is there no circular birefringence in the fiber but the
polarization relative to the laboratory reference frame is not rotated along
the fiber. The reason for this is that in contrast with the polarization
vector, the Jones vector does not give a complete description of the
polarization. As a mathematical entity in some local reference frame that
depends on the instantaneous propagation direction, it can only describe the
state of polarization relative to that reference frame. With the new
implication of the Jones vector, the results of the experiment reported by Papp
and Harms in 1977 are explained satisfactorily. In particular, it is shown that
the state of polarization relative to the Tang frame remains unchanged along
the fiber. The optical activity appears only relative to the Serret-Frenet
frame.
