Variable dispersion compensator

A polarization mode dispersion compensator comprising:

• a polarized wave separator/synthesizer-which separates light into first and second polarized light components serving as two linear polarized light components and synthesizes the first and second polarized light components;
• a first optical waveguide having a first chirped grating which receives the first polarized light component as an input light component and in which Bragg wavelength is changed along the longitudinal direction of the grating;
• a first temperature controller which controls temperature of said first chirped grating;
• a second optical waveguide having a second chirped grating which receives the second polarized light component as input light component and in which Bragg wavelength is changed along the longitudinal direction of the grating;
• and
• a second temperature controller which controls temperature of said second chirped grating;
• wherein temperature distributions based on the first and second functions T1(x) and T2(x) of the distance x are applied to central portions of the first and second gratings defined as a regions where distance x from an end of the first and second grating is a range of 20% to 80% of total length of the first and second grating along the longitudinal direction thereof respectively, and,
• wherein the second function T2(x) has distance dependence different from that of the T1(x).