MULTILEVEL OPTICAL PHASE MODULATOR

• US 20090086303A1
• Filed: 08/11/2008
• Published: 04/02/2009
• Est. Priority Date: 09/28/2007
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Ide, Satoshi, Tsunoda, Yukito
• Granted Patent: US 7,876,491 B2
• Time in Patent Office: Days
• US Class Current: 359/279
• CPC Class Codes: H04B 10/5053 using a parallel, i.e. shunt, combination of modulators
• CPC Class Codes: H04B 10/5561 Digital phase modulation

Abstract

To take out monitor light unaffected by a multilevel optical phase-modulated component. For the purpose, a phase-shift unit that controls phases of plural (n, n is an integral number equal to or greater than 2) input lights, plural (n, n is an integral number equal to or greater than 2) phase modulating units that respectively phase-modulate the input lights from the phase-shift units, a first coupling unit that couples and outputs the phase-modulated lights from the plural phase modulating units as multilevel optical phase-modulated signal light, and a second coupling unit that couples and outputs non-phase-modulated lights from the plural phase modulating units as coupled light are provided.

Claims

1. A multilevel optical phase modulator comprising:

a phase-shift unit that controls phases of plural (n, n is an integral number equal to or greater than

     2) input lights;

plural (n, n is an integral number equal to or greater than

     2) phase modulating units that respectively phase-modulate the input lights from the phase-shift units;

a first coupling unit that couples and outputs the phase-modulated lights from the plural phase modulating units as multilevel optical phase-modulated signal light; and

a second coupling unit that couples and outputs non-phase-modulated lights from the plural phase modulating units as coupled light.

2. The multilevel optical phase modulator according to claim 1, further comprising a first dividing unit that divides input light into at least the n, and configured to supply the n lights from the first dividing unit as the input lights to the plural phase-shift units.

5. The multilevel optical phase modulator according to claim 1, wherein the second coupling unit includes plural input routes according to the number of the phase modulating units, and m (m is an integral number equal to or greater than 1) output route(s) that guide(s) the coupled light of the lights from the plural input routes.

7. The multilevel optical phase modulator according to claim 1, wherein the second coupling unit includes plural input routes according to the number of the phase modulating units, and m (m is an integral number equal to or greater than 1) pairs of (first and second) output routes that guide the coupled light of the lights from the plural input routes.

9. The multilevel optical phase modulator according to claim 1, further comprising at least one photodetector that receives the coupled light from the second coupling unit, and a phase-shift control unit that controls an amount of phase shift in the phase-shift unit based on the coupled light received by the photodetector.

11. The multilevel optical phase modulator according to claim 1, further comprising at least one pair of (first and second) photodetectors that receive the coupled light from the second coupling unit, and a phase-shift control unit that controls an amount of phase shift in the phase-shift unit based on the coupled light received by the photodetectors.

13. The multilevel optical phase modulator according to claim 2, further comprising at least one photodetector that receives the coupled light from the second coupling unit, and a phase modulation bias control unit that controls biases in the phase modulating units based on the coupled light received by the photodetector.

14. The multilevel optical phase modulator according to claim 2, further comprising at least one pair of (first and second) photodetectors that receive the coupled light from the second coupling unit, and a phase modulation bias control unit that controls biases in the phase modulating units based on the coupled light received by one of the first and second photodetectors.

15. The multilevel optical phase modulator according to claim 1, further comprising optical waveguides that respectively guide the non-phase-modulated lights from the plural phase modulating units.

16. The multilevel optical phase modulator according to claim 1, wherein the phase modulated light is light formed by phase-modulating the input light according to a phase modulation sign by the phase modulating unit, and the non-phase-modulated light is light having intensity inverted with respect to the light formed by phase-modulating the input light according to the phase modulation sign.

17. The multilevel optical phase modulator according to claim 1, wherein the non-phase-modulated light output from the phase modulating unit has a substantial phase difference of 90 degrees from that of the phase-modulated light output form the phase modulating unit.

3. A multilevel optical phase modulator comprising:

a phase-shift unit that controls phases of plural (n, n is an integral number equal to or greater than

     2) input lights;

plural (n, n is an integral number equal to or greater than

     2) phase modulating units that respectively phase-modulate the input lights from the phase-shift units;

a first coupling unit that couples and outputs the phase-modulated lights from the plural phase modulating units as multilevel optical phase-modulated signal light;

a second dividing unit that divides a part of the input lights to the plural phase modulating units; and

a second coupling unit that couples and outputs divided lights from the second dividing unit as coupled light.

4. The multilevel optical phase modulator according to claim 3, further comprising a first dividing unit that divides input light into at least the n, and configured to supply the n lights from the first dividing unit as the input lights to the plural phase-shift units.

6. The multilevel optical phase modulator according to claim 3, wherein the second coupling unit includes plural input routes according to the number of the phase modulating units, and m (m is an integral number equal to or greater than 1) output route(s) that guide(s) the coupled light of the lights from the plural input routes.

8. The multilevel optical phase modulator according to claim 3, wherein the second coupling unit includes plural input routes according to the number of the phase modulating units, and m (m is an integral number equal to or greater than 1) pairs of (first and second) output routes that guide the coupled light of the lights from the plural input routes.

10. The multilevel optical phase modulator according to claim 3, further comprising at least one photodetector that receives the coupled light from the second coupling unit, and a phase-shift control unit that controls an amount of phase shift in the phase-shift unit based on the coupled light received by the photodetector.

12. The multilevel optical phase modulator according to claim 3, further comprising at least one pair of (first and second) photodetectors that receive the coupled light from the second coupling unit, and a phase-shift control unit that controls an amount of phase shift in the phase-shift unit based on the coupled light received by the photodetectors.