Performance analysis for all-fiber polarization transformer with specific spun rate profile

All-fiber polarization transformer (AFPT) is a length of variably spun birefringence fiber which can transform the state of polarization as a wave plate. A set of complete analytic solutions for the coupled-mode equation of AFPT with a specific function of spun rate is deduced by a modified method through deliberate matrix transformation. And the analytical expressions of the transmitting eigen-modes from the zero spun-rate end to the maximum spun-rate end are derived. Moreover, when the linear polarized light is input as single eigen-mode, the ellipticity of quasi-circular polarization light at the output end is calculated as function of the fiber structure parameters. The equivalent retardation of AFPT is evaluated and the critical constraints between the fiber length and the maximum spun rate are illustrated according to practical requirements.