# US 8,787,713 B2 · Optical device, optical hybrid circuit, and optical receiver

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- Number: US 8,787,713 B2
- Document ID: US8787713B2
- Status: Granted
- Kind: B2
- Application number: 12/956,156
- Filed: 2010-11-30
- Published: 2011-06-02
- Granted: 2014-07-22
- Earliest claimed: 2009-12-01
- Assignees: Fujitsu Limited
- Applicants: Seok-Hwan Jeong
- Inventors: Seok-Hwan Jeong
- Web page: https://patentgrep.com/patent/US8787713B2

## CPC

- G02B 6/26: Optical coupling means (G02B6/36, G02B6/42 take precedence)
- G02B 6/2813: {based on multimode interference effect, i.e. self-imaging}
- G02B 6/29344: {operating by modal interference or beating, i.e. of transverse modes, e.g. zero-gap directional coupler, MMI}
- H04B 10/677: {for differentially modulated signal, e.g. DPSK signals}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H04B: TRANSMISSION

## Abstract

According to aspects of embodiments, an optical device includes a first coupler configured to split an optical signal; a second coupler configured to cause optical signals to interfere with each other, a first waveguide configured to couple the first coupler to the second coupler, the first waveguide includes a first phase shifter region having a section narrower in width than an end of the first phase shifter region, the second waveguide includes a second phase shifter region having a section wider in width than an end of the second phase shifter region.

## Claims

### Claim 1

An optical device, comprising:
a first coupler configured to split an optical signal;
a second coupler configured to cause optical signals to interfere with each other;
a first waveguide configured to couple the first coupler to the second coupler, the first waveguide includes a first phase shifter region having a section narrower in width than an end of the first phase shifter region; and
a second waveguide configured to couple the first coupler to the second coupler, the second waveguide includes a second phase shifter region having a section wider in width than an end of the second phase shifter region, wherein the first phase shifter region and the second phase shifter region are aligned at substantially the same length-wise position and have substantially the same length;
wherein each of the first phase shifter region and the second phase shifter region has a longitudinal length of 50 μm or less; and
wherein the first phase shifter region includes a tapered section extending from an input end of the first phase shifter region and then linearly tapering in a longitudinal direction to an end of the tapered section, where a reverse-tapered section begins linearly-reverse tapering and then extending to an output end of the first phase shifter region in the longitudinal direction.

### Claim 2 (depends on 1)

The optical device according to claim 1,
wherein the second phase shifter region includes a reverse-tapered section extending from an input end of the second phase shifter region and then linearly-reverse tapering in a longitudinal direction to an end of the reverse-tapered section, where a tapered section begins linearly tapering and then extending to an output end of the second phase shifter region in the longitudinal direction.

### Claim 3 (depends on 1)

The optical device according to claim 1,
wherein the whole of the first waveguide is the first phase shifter region, and wherein the whole of the second waveguide is the second phase shifter region.

### Claim 4 (depends on 1)

The optical device according to claim 1, wherein a part of the first waveguide is the first phase shifter region, and wherein a part of the second waveguide is the second phase shifter region.

### Claim 5 (depends on 1)

The optical device according to claim 1, wherein each of the first phase shifter region and the second phase shifter region comprises a waveguide structure that is symmetrical with respect to the lengthwise center position in the longitudinal direction thereof.

### Claim 6 (depends on 1)

The optical device according to claim 1, wherein each of the first phase shifter region and the second phase shifter region comprises a waveguide structure that is asymmetrical with respect to the lengthwise center position in the longitudinal direction thereof.

### Claim 7 (depends on 1)

The optical device according to claim 1, wherein each of the first coupler and the second coupler comprises a 2:2 coupler, the 2:2 coupler having two channels at the input side thereof and two channels at the output side thereof.

### Claim 8 (depends on 1)

The optical device according to claim 1, wherein the first coupler comprises a 1:2 optical coupler, having one channel at the input side thereof, and two channels at the output side thereof, and
wherein the second coupler comprises a 2:1 optical coupler, having two channels at the input side thereof and one channel at the output side thereof.