A polarization modulation method of photonic pulses includes: generating a plurality of photonic pulses with an unspecified polarization state obtained by the overlapping of both the horizontal and vertical polarization modes thereof, and routing them in a first polarization-maintaining fiber; splitting the horizontal and vertical polarization modes and routing them in respective terminals of a second polarization-maintaining fiber forming a ring, whereby they travel clockwise and counter-clockwise respectively, or vice versa; inducing a respective phase modulation of both polarization modes, in one point of the ring which is spaced from said terminals by optical paths having different length along said ring, thereby a polarization-maintaining fiber delay line is determined; and recombining the polarization modes in one single photonic pulse beam, and routing the resulting beam through the first polarization-maintaining fiber, by obtaining, at the output thereof, a polarization state of the pulses depending upon the difference between said phase modulations.