The application of the Jones calculus to optical circuits in which counterpropagating light beams are present is discussed, with particular attention to the conventions associated with the Jones calculus for the description of the polarization state of an optical beam and to the reference system adopted. The reference system adopted here differs from that used by Jones, but it exploits a simpler formalism when used to describe complex optical systems where multiple reflections take place. The differences between these two reference systems are pointed out with particular attention to the behavior of nonreciprocal optical devices and reflectors. An application of the results to a simple optical circuit is presented.