Optical modulator

An optical modulator comprising:

• first and second optical modulation units that are formed on a substrate;
• a polarization beam rotating unit that rotates at least one polarization beam of modulated light beams modulated by the first and second optical modulation units;
• and
• a polarization beam combining unit that is disposed outside the substrate and that includes a polarization beam combining element combining the polarization beams of the modulated light of which the polarization beams are rotated by the polarization beam rotating unit,
• wherein the polarization beam combining unit includes an optical system in which two opposed collimating systems are arranged,
• wherein the two opposed collimating systems include a first collimator to which the modulated light beams modulated by the first and second optical modulation units are input, and a second collimator to which an output light beam of the polarization beam combining element is input,
• wherein an input position of the second collimator is substantially located at the center of a position gap varying depending on the polarization beams of the output light of the polarization beam combining element, and wherein the first collimator includes a V-grooved block including a two-hole, and the second collimator includes a V-grooved block including a one-hole.

An optical modulator comprising:

• first and second optical modulation units that are formed on a substrate;
• a polarization beam rotating unit that rotates at least one polarization beam of modulated light beams modulated by the first and second optical modulation units;
• and
• a polarization beam combining unit that is disposed outside the substrate and that includes a polarization beam combining element combining the polarization beams of the modulated light of which the polarization beams are rotated by the polarization beam rotating unit,
• wherein the polarization beam combining unit includes an optical system in which two opposed collimating systems are arranged,
• wherein the two opposed collimating systems include a first collimator to which the modulated light beams modulated by the first and second optical modulation units are input, and a second collimator to which an output light beam of the polarization beam combining element is input,
• wherein an input position of the second collimator is substantially located at the center of a position gap varying depending on the polarization beams of the output light of the polarization beam combining element,
• wherein at least one of the two opposed collimating systems include fiber collimators, respectively, and
• wherein at least one of the two opposed collimating systems is configured to include a V-grooved block.

An optical modulator comprising:

• first and second optical modulation units that are formed on a substrate;
• a polarization beam rotating unit that rotates at least one polarization beam of modulated light beams modulated by the first and second optical modulation units;
• and
• a polarization beam combining unit that is disposed outside the substrate and that includes a polarization beam combining element combining the polarization beams of the modulated light of which the polarization beams are rotated by the polarization beam rotating unit,
• wherein the polarization beam combining unit includes an optical system in which two opposed collimating systems are arranged,
• wherein the two opposed collimating systems include a first collimator and a second collimator, the first collimator includes a two-hole used in a portion to which the modulated light beams modulated by the first and second optical modulation units are input, and the second collimator includes a one-hole used in a portion to which an output light beam of the polarization beam combining element is input,
• wherein at least one of the two opposed collimating systems includes a fiber collimator, and
• wherein the second collimator is located between outputs of both the polarization beams of the modulated light beams modulated by the first and second optical modulation units, the second collimator has such an input position as to reduce a polarization dependency loss.