New point of view about optical activity in helically-coiled fiber

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.