Manual Fiber Polarization Controllers is made by the principle of birefringence generated by optical fiber under the action of external force. The three rings are equivalent to λ/4, λ/2 and λ/4 wave plates respectively. The light wave passes through the λ/4 wave plate and is converted into linearly polarized light, and then the polarization direction is adjusted by the λ/2 wave plate. The polarization state of the linearly polarized light is changed to an arbitrary polarization state via a λ/4 wave plate. The delay effect caused by the birefringence effect is mainly determined by the cladding radius of the fiber, the radius of the fiber surround and the wavelength of the light wave.