We propose the concept of a dynamic eigenstate of polarization (DES) to des
cribe the sensitivity of the output polarization of an optical component re
lative to the change of a key parameter characterizing its birefringent cha
racteristics. The concept is a generalization of the concept of principal s
tates developed for polarization mode dispersion to generalized parameters
such as temperature, pressure, voltage, angular adjustment, etc. We discuss
the application of the DES concept in some detail for polarization control
and polarization sensitivity relative to temperature.