Integrated optical device

1. An integrated optical device, comprising:

a housing;

a liquid-crystal optical power attenuator, an optical splitter, and an optical power monitor housed inside the housing;

an aperture disposed on a light-receiving face of the optical power monitor; and

a first optical fiber and a second optical fiber both housed inside the housing, wherein

the first optical fiber inputs an optical signal from outside of the housing to the optical power attenuator,

in a polarized state, the optical power attenuator attenuates the optical signal from the first optical fiber,

the second optical fiber outputs the attenuated optical signal from the optical power attenuator to the outside of the housing,

the optical splitter generates a split signal by splitting at least one of:

the optical signal input to the optical power attenuator from the first optical fiber, and

the attenuated optical signal output from the optical power attenuator to the second optical fiber, and

the optical power monitor receives the split signal and detects a power of the split signal.

2. The integrated optical device of claim 1 , wherein

the optical splitter generates:

a first split signal by splitting the optical signal input from the first optical fiber to the optical power attenuator, and

a second split signal by splitting the attenuated optical signal output from the optical power attenuator to the second optical fiber, and

the integrated optical device comprises a plurality of the optical power monitor including:

a first optical power monitor that receives the first split signal and detects a power of the first split signal, and

a second optical power monitor that receives the second split signal and detects a power of the second split signal.

3. The integrated optical device of claim 1 , wherein

the optical power attenuator comprises:

a birefringent crystal wherethrough the optical signal from the first optical fiber passes; and

a liquid-crystal element that:

comprises a drive voltage controlled by a controller, and

reflects the optical signal that passes through the birefringent crystal as a returning light to the birefringent crystal in a deflected state according to the drive voltage, wherein

a quantity of the returning light that passes through the birefringent crystal from the liquid-crystal element and that is coupled to the second optical fiber changes according to the deflected state of the returning light, and

the attenuated optical signal corresponds to a portion of the returning light that passes through the birefringent crystal and that is coupled to the second optical fiber.

4. The integrated optical device of claim 3 , wherein

the birefringent crystal converts the optical signal from the first optical fiber into two mutually orthogonal linearly polarized components, and

the liquid-crystal element has a liquid-crystal orientation angle tilted 45 degrees relative to the two mutually orthogonal linearly polarized components.

5. The integrated optical device of claim 4 , wherein

the optical power attenuator comprises the plurality of liquid-crystal element that comprises a first liquid-crystal element and a second liquid-crystal element,

the first liquid-crystal element has a first liquid-crystal orientation angle tilted 45 degrees relative to the two linearly polarized components, and

the second liquid-crystal element has a second liquid-crystal orientation angle tilted 45 degrees relative to the two linearly polarized components and is orthogonal to the first liquid-crystal orientation angle.

6. The integrated optical device of claim 3 , further comprising:

a first collimator lens disposed between the first optical fiber and the birefringent crystal; and

a second collimator lens disposed between the second optical fiber and the birefringent crystal, wherein

the optical signal from the first optical fiber is propagated to the liquid-crystal element through the first collimator lens and the birefringent crystal, and

the returning light from the liquid-crystal element is propagated to the second optical fiber through the birefringent crystal and the second collimator lens.

7. The integrated optical device of claim 6 , further comprising:

one optical path conversion prism disposed between the first and second collimator lenses and the birefringent crystal, wherein the optical path conversion prism:

refracts the optical signal from the first optical fiber that passes through the first collimator lens to pass through the birefringent crystal and head to the liquid-crystal element, and

refracts the returning light from the birefringent crystal so the returning light heads to the second collimator lens.

8. The integrated optical device of claim 3 , further comprising:

a convertor that converts a DC voltage input from the controller into an AC voltage, wherein the liquid-crystal element is driven by the AC voltage.

9. The integrated optical device of claim 1 , further comprising:

an aperture on a light receiving face of the optical power monitor, wherein the aperture:

is integrated with or independent of the optical power monitor,

suppresses stray light from reaching the light receiving face, and

selectively irradiates the split signal to the light receiving face.

10. An integrated optical device, comprising:

a housing;

a liquid-crystal optical power attenuator, an optical splitter, and a plurality of optical power monitors housed inside the housing; and

a first optical fiber and a second optical fiber both housed inside the housing,

wherein:

the first optical fiber inputs an optical signal from outside of the housing to the optical power attenuator,

in a polarized state, the optical power attenuator attenuates the optical signal from the first optical fiber,

the second optical fiber outputs the attenuated optical signal from the optical power attenuator to the outside of the housing,

the optical splitter generates:

a first split signal by splitting the optical signal input from the first optical fiber to the optical power attenuator, and

a second split signal by splitting the attenuated optical signal output from the optical power attenuator to the second optical fiber, and

the plurality of optical power monitors includes:

a first optical power monitor that receives the first split signal and detects a power of the first split signal, and

a second optical power monitor that receives the second split signal and detects a power of the second split signal.