  In this paper, we present a study of orthogonal polarization modes in the
radio emission of PSR B1133+16, conducted within the frame of simultaneous,
multi-frequency, single-pulse observations. Simultaneously observing at two
frequencies (1.41 GHz and 4.85 GHz) provides the means to study the bandwidth
of polarization features such as the polarization position angle. We find two
main results. First, that there is a high degree of correlation between the
polarization modes at the two frequencies. Secondly, the modes occur more
equally and the fractional linear polarization decreases towards higher
frequencies. We discuss this frequency evolution and propose propagation
effects in the pulsar magnetosphere as its origin.
