Polarization scrambler and optical network using the same

An optical network in which a continuous wave transmitted via an optical fiber from a light source arranged at one node is input to an optical intensity modulator at the other node, the optical intensity modulator then modulating the continuous wave using an externally input data signal, the resulting modulated signal light being transmitted to a next node, said one node comprising a polarization scrambler converting the continuous wave output by the light source into scrambled light with a zero degree of polarization and then outputting the scrambled light,

• said polarization scrambler comprising:
• an optical pulse generator that generates optical pulses with an intensity waveform repetition period T/2 and an electrical field period T in which the same intensity waveform is repeated every repetition period T/2 and in which phase is inverted every repetition period T/2;
• and
• an orthogonal polarization delay unit which receives each of said optical pulses, separates the optical pulse into two optical pulses with orthogonal states of polarization, and relatively shifts the temporal position of one of the two optical pulses from that of the other optical pulse by (2n−1)T/4 (n is a natural number) to generate light in which each pulse is polarized orthogonally to a succeeding pulse, and
• said other node comprising:
• a polarization-dependent optical intensity modulator used as an optical intensity modulator;
• clock electric signal extracting means for splitting part of power of the input scrambled light, converting this part into an electric signal, and extracting from the electric signal a clock electric signal with a frequency n times (n is an natural number) as high as that of an electric signal driving an optical pulse generator in said polarization scrambler;
• and
• phase synchronization means for synchronizing a phase of a data signal bit rate clock input by said polarization scrambler to a phase of said extracted clock electric signal and inputting the resulting signal to said polarization-dependent optical intensity modulator.