# US 2014/0153934 A1 · Optical modulator and optical transmitter

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- Number: US 2014/0153934 A1
- Document ID: US20140153934A1
- Status: Published application
- Kind: A1
- Application number: 14/049,584
- Filed: 2013-10-09
- Published: 2014-06-05
- Earliest claimed: 2012-12-05
- Assignees: Fujitsu Optical Components Limited
- Applicants: Fujitsu Optical Components Limited
- Inventors: Masaki Sugiyama
- Web page: https://patentgrep.com/patent/US20140153934A1

## CPC

- G02B 6/29355: {Cascade arrangement of interferometers}
- G02F 1/035: in an optical waveguide structure
- H04B 10/5053: {using a parallel, i.e. shunt, combination of modulators}
- G02F 1/212: {Mach-Zehnder type}
- G02F 2201/58: Arrangements comprising a monitoring photodetector
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- H04B: TRANSMISSION

## Abstract

An optical modulator includes a Mach-Zehnder optical waveguide that includes a pair of parallel waveguides, and a two-input-one-output optical coupler that couples light output from the parallel waveguides; a branching waveguide that branches a portion of light output from the optical coupler; and a light receiving unit that receives the light output from the branching waveguide. Orientation of an output end of the branching waveguide is angled toward the light receiving unit, to be oblique with respect to the parallel waveguides, and orientation of an output end of the optical coupler is angled toward a side opposite to that of the output end of the branching waveguide, to be oblique with respect to the parallel waveguides.

## Claims

### Claim 1

An optical modulator comprising:
a Mach-Zehnder optical waveguide that includes:
a pair of parallel waveguides, and
a two-input-one-output optical coupler that couples light output from the parallel waveguides;
a branching waveguide that branches a portion of light output from the optical coupler; and
a light receiving unit that receives the light output from the branching waveguide, wherein
orientation of an output end of the branching waveguide is angled toward the light receiving unit, to be oblique with respect to the parallel waveguides, and
orientation of an output end of the optical coupler is angled toward a side opposite to that of the output end of the branching waveguide, to be oblique with respect to the parallel waveguides.

### Claim 2 (depends on 1)

The optical modulator according to claim 1, wherein
one waveguide of the parallel waveguides includes a length correcting unit that corrects a length of the one waveguide.

### Claim 3 (depends on 2)

The optical modulator according to claim 2, wherein
the length correcting unit is disposed under electrodes.

### Claim 4 (depends on 3)

The optical modulator according to claim 3, wherein
the electrodes are electrodes that apply bias voltage to the parallel waveguides.

### Claim 5 (depends on 4)

The optical modulator according to claim 4, wherein
an electrode is disposed between the electrodes that apply the bias voltage to the parallel waveguides.

### Claim 6 (depends on 1)

The optical modulator according to claim 1, wherein
a waveguide between the optical coupler and the branching waveguide includes a single-mode portion.

### Claim 7 (depends on 6)

The optical modulator according to claim 6, wherein
the waveguide narrows in a tapered shape from the optical coupler toward the branching waveguide.

### Claim 8 (depends on 6)

The optical modulator according to claim 6, wherein
a specific refractive index of the waveguide gradually decreases from the optical coupler toward the branching waveguide.

### Claim 9

An optical transmitter comprising:
a light emitting element that emits light;
a data generating circuit that generates modulated data;
a driver that generates an electrical signal corresponding to the modulated data output from the data generating circuit; and
an optical modulator that based on the electrical signal output from the driver, modulates the light emitted from the light emitting element, wherein
the optical modulator includes:
a Mach-Zehnder optical waveguide that includes:
a pair of parallel waveguides; and
a two-input-one-output optical coupler that couples light output from the parallel waveguides;
a branching waveguide that branches a portion of light output from the optical coupler; and
a light receiving unit that receives the light output from the branching waveguide,
orientation of an output end of the branching waveguide is angled toward the light receiving unit, to be oblique with respect to the parallel waveguides, and
orientation of an output end of the optical coupler is angled toward a side opposite to that of the output end of the branching waveguide, to be oblique with respect to the parallel waveguides.

### Claim 10 (depends on 9)

The optical transmitter according to claim 9, wherein
one waveguide of the parallel waveguides includes a length correcting unit that corrects a length of the one waveguide.

### Claim 11 (depends on 10)

The optical transmitter according to claim 10, wherein
the length correcting unit is disposed under electrodes.

### Claim 12 (depends on 11)

The optical transmitter according to claim 11, wherein
the electrodes are electrodes that apply bias voltage to the parallel waveguides.

### Claim 13 (depends on 12)

The optical transmitter according to claim 12, wherein
an electrode is disposed between the electrodes that apply the bias voltage to the parallel waveguides.

### Claim 14 (depends on 9)

The optical transmitter according to claim 9, wherein
a waveguide between the optical coupler and the branching waveguide includes a single-mode portion.

### Claim 15 (depends on 14)

The optical transmitter according to claim 14, wherein
the waveguide narrows in a tapered shape from the optical coupler toward the branching waveguide.

### Claim 16 (depends on 14)

The optical transmitter according to claim 14, wherein
a specific refractive index of the waveguide gradually decreases from the optical coupler toward the branching waveguide.