Optical phase shifter and demodulator

An optical phase shifter comprising:

• a thermo-optical element where a refractive index of the thermo-optical element with respect to an input optical signal is temperature dependent;
• a temperature change section contacting one end of the thermo-optical element, and a temperature of the temperature change section changes a temperature of the thermo-optical element to a desired temperature;
• a heat dissipation section disposed on an opposite side of the thermo-optical element than the temperature change section and which enters a state of thermal equilibrium at a different temperature than the temperature of the temperature change section;
• and
• a temperature buffer section disposed between and contacting the temperature change section and the heat dissipation section where the temperature buffer section has a heat resistance greater than the heat dissipation section,
• wherein the thermo-optical element is surrounded by a vacuum, and
• wherein a product R1×S×To3 of a heat resistance R1 of the thermo-optical element, an area S of a surface of the thermo-optical element surrounded by the vacuum, and a cubed absolute temperature To of the thermo-optical element is less than a product 4000000×δ of a desired refractive index distribution ratio δ of the thermo-optical element and a constant 4000000.

An optical phase shifter comprising:

• a thermo-optical element where a refractive index of the thermo-optical element with respect to an input optical signal is temperature dependent;
• a temperature change section contacting one end of the thermo-optical element, and a temperature of the temperature change section changes a temperature of the thermo-optical element to a desired temperature;
• a heat dissipation section disposed on an opposite side of the thermo-optical element than the temperature change section and which enters a state of thermal equilibrium at a different temperature than the temperature of the temperature change section;
• and
• a temperature buffer section disposed between and contacting the temperature change section and the heat dissipation section where the temperature buffer section has a heat resistance greater than the heat dissipation section,
• wherein a product C2×R2 of a heat capacity C2 of the temperature buffer section and a heat resistance R2 of the temperature buffer section is in the range of half to double of a product C1×R1 of a heat capacitor C1 of the thermo-optical element and a heat resistance R1 of the thermo-optical element.