High-speed, silicon-based electro-optic modulator with feedback control

A free-carrier based electro-optic interferometer comprising

• a first arm including a first optical waveguide;
• a second arm including a second optical waveguide;
• an optical splitter for dividing an optical input signal into a first input signal to be coupled into the first arm and a second input signal to be coupled into the second arm;
• a first free carrier-based modulation element disposed along the first arm, the first modulation element having a first region of a first conductivity type and a second region of a second conductivity type and utilizing changes in carrier density to generate a first modulated optical output signal, wherein the application of the modulating electrical input signal to the first free carrier-based modulation element generates free carrier movement so as to modulate the free carrier density in the first and second regions and introduce a modulation in the refractive index of the waveguide, thereby creating the first modulated optical output signal;
• and
• a second free carrier-based modulation element disposed along the second arm having a first region of the first conductivity type and a second region of the second conductivity type and utilizing changes in carrier density to generate a second modulated optical output signal, wherein the application of the modulating electrical input signal to the second free carrier-based modulation element generates free carrier movement so as to modulate the free carrier density in the first and second regions in the second modulation element and introduce a modulation in the refractive index of the waveguide, thereby creating the second modulated optical output signal;
• an optical combiner disposed at the output of the first and second arms to combine the first and second modulated optical output signals from the first and second arms, wherein the electrical modulating signal is applied to at least one of the first and second modulation elements to form a modulated optical output signal;
• an electrical signal source for generating a first reference voltage (REF0A) representative of a logic “0” value for the first modulation element, a second reference voltage (REF0D) representative of a logic “0” value for the second modulation element, a third reference voltage (REF1A) representative of a logic “1” value for the first modulation element, a fourth reference voltage (REF1D) representative of a logic “1” value for the second modulation element, and a non-modulating potential voltage (REF) to be applied to one region of each modulation element;
• and
• a feedback module, responsive to the modulated optical output signal, to adjust at least one modulator parameter selected from the group consisting of:
• the first, second, third and fourth reference levels, and the non-modulating potential voltage to optimize interferometer performance as a function of time.