# US 2019/0170939 A1 · Optical module and inputting method

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2019/0170939 A1
- Document ID: US20190170939A1
- Status: Published application
- Kind: A1
- Application number: 16/208,134
- Filed: 2018-12-03
- Published: 2019-06-06
- Earliest claimed: 2017-12-04
- Assignees: Fujikura Ltd.
- Applicants: Fujikura Ltd.
- Inventors: Takuya Oda; Akira Oka
- Web page: https://patentgrep.com/patent/US20190170939A1

## CPC

- G02B 6/126: using polarisation effects {(G02B6/1226 takes precedence)}
- G02B 6/2726: {in or on light guides, e.g. polarisation means assembled in a light guide}
- G02B 6/2766: {Manipulating the plane of polarisation from one input polarisation to another output polarisation, e.g. polarisation rotators, linear to circular polarisation converters}
- G02B 6/2793: {Controlling polarisation dependent loss, e.g. polarisation insensitivity, reducing the change in polarisation degree of the output light even if the input polarisation state fluctuates}
- G02B 6/241: {Light guide terminations}
- G02B 2006/12061: {Silicon}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical module includes: an output section that outputs TM light; and a substrate-type optical waveguide. The substrate-type optical waveguide includes: a waveguide that guides the TM light outputted from the output section; a polarization rotating element that converts the TM light guided through the waveguide into TE light; and a function element that receives the TE light. In the optical module equation (a×L)>(b×L+c) is satisfies, where L is a length of the waveguide, a is a propagation loss of the TE light per unit length of the waveguide, b is a propagation loss of the TM light per unit length of the waveguide, and c is an insertion loss by the polarization rotating element.

## Claims

### Claim 1

An optical module comprising:
an output section that outputs TM light; and
a substrate-type optical waveguide comprising:
a waveguide that guides the TM light outputted from the output section;
a polarization rotating element that converts the TM light guided through the waveguide into TE light; and
a function element that receives the TE light,
wherein formula (1) below is satisfied:
(a×L)>(b×L+c), where (1)
L is a length of the waveguide,
a is a propagation loss of the TE light per unit length of the waveguide,
b is a propagation loss of the TM light per unit length of the waveguide, and
c is an insertion loss by the polarization rotating element.

### Claim 2 (depends on 1)

The optical module according to claim 1, wherein
the output section is another polarization rotating element that converts the TE light into TM light out putting the output section, and
formula (2) below is satisfied:
(a×L)>(b×L+c+c′), (2)
where c′ is an insertion loss by the output section.

### Claim 3 (depends on 2)

The optical module according to claim 2, wherein the output section is disposed in the substrate-type optical waveguide.

### Claim 4 (depends on 2)

The optical module according to claim 2, wherein the output section is disposed outside the substrate-type optical waveguide.

### Claim 5 (depends on 1)

The optical module according to claim 1, wherein
the output section is a light emitting element disposed outside the substrate-type optical waveguide, and
the output section emits light having an electric field that oscillates orthogonal to a main surface of the substrate-type optical waveguide.

### Claim 6 (depends on 1)

The optical module according to claim 1, wherein
the output section is a polarization maintaining fiber disposed outside the substrate-type optical waveguide, and
the output section emits light having an electric field that oscillates orthogonal to a main surface of the substrate-type optical waveguide.

### Claim 7 (depends on 1)

The optical module according to claim 1, wherein the function element is a modulator, a switch, or a light receiver.

### Claim 8

A method of inputting light into a function element disposed in a substrate-type optical waveguide, comprising:
inputting TM light into the substrate-type optical waveguide;
guiding the inputted TM light through a waveguide having a length L disposed in the substrate-type optical waveguide;
converting the TM light guided through the waveguide into TE light in the substrate-type optical waveguide; and
inputting the TE light into the function element disposed in the substrate-type optical waveguide, wherein formula (1) below is satisfied:
(a×L)>(b×L+c), where (1)
a is a propagation loss of the TE light per unit length of the waveguide,
b is a propagation loss of the TM light per unit length of the waveguide, and
c is an insertion loss in the conversion of the TM light into the TE light.