  Several on-going and future experiments use a Stokes polarimeter (i.e. a
rotating wave plate followed by a steady polarizer and by an unpolarized
detector) to measure the small polarized component of the Cosmic Microwave
Background. The expected signal is typically evaluated using the Mueller
formalism. In this work we carry-out the signal evaluation taking into account
the temperatures of the different optical devices present in the instrument,
their non- idealities, multiple internal reflections, and reflections between
different optical components. This analysis, which exploits a new description
of the radiation transmitted by a half wave plate, can be used to optimize the
experimental setup as well as each of its optical components. We conclude with
an example of application of our analysis, studying a cryogenic polarization
modulator developed for detecting the interstellar dust polarization.
