Patent ID: 8107154

Claim:
An optical modulator comprising: a first polarization separation and combination portion that comprises a first input and output terminal, at which signal light that is linearly polarized light is input, a second input and output terminal, which is provided at a side opposite from the first input and output terminal, and a third input and output terminal, which outputs modulated signal light; a second polarization separation and combination portion that comprises a first input and output terminal, a second input and output terminal, which is provided at a side opposite from the first input and output terminal, a third input and output terminal, and a fourth input and output terminal, which is provided at a side opposite from the third input and output terminal and outputs a polarization cross-talk component of the signal light; a first polarization plane-maintaining optical fiber of which a first end is coupled with the second input and output terminal of the first polarization separation and combination portion; a second polarization plane-maintaining optical fiber of which a first end is coupled with the first input and output terminal of the second polarization separation and combination portion; a polarization plane rotation adjustment portion that comprises a half-wavelength plate which optically communicates with a second end of the first polarization plane-maintaining optical fiber and a second end of the second polarization plane-maintaining optical fiber, an optical axis direction of the half-wavelength plate being rotatable; a third polarization plane-maintaining optical fiber of which a first end is coupled with the second input and output terminal of the second polarization separation and combination portion, the third polarization plane-maintaining optical fiber including a first optical coupler, to which control light that is linearly polarized light is input; a fourth polarization plane-maintaining optical fiber of which a first end is coupled with the third input and output terminal of the second polarization separation and combination portion; and a first polarization plane conversion portion that optically communicates with a second end of the third polarization plane-maintaining optical fiber and a second end of the fourth polarization plane-maintaining optical fiber, the first polarization plane conversion portion converting a polarization plane of input signal light.