# US 2023/0058741 A1 · Demultiplexer

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- Number: US 2023/0058741 A1
- Document ID: US20230058741A1
- Status: Published application
- Kind: A1
- Application number: 17/793,914
- Filed: 2021-01-22
- Published: 2023-02-23
- Earliest claimed: 2020-01-22
- Assignees: Rockley Photonics Limited
- Applicants: Rockley Photonics Limited
- Inventors: Thomas Pierre SCHRANS; Andrea TRITA; Adam SCOFIELD
- Web page: https://patentgrep.com/patent/US20230058741A1

## CPC

- G02B 6/12016: {characterised by the input or output waveguides, e.g. tapered waveguide ends, coupled together pairs of output waveguides}
- G02B 6/4215: {the intermediate optical elements being wavelength selective optical elements, e.g. variable wavelength optical modules or wavelength lockers (G02B6/4246 takes precedence)}
- G02B 6/12007: {forming wavelength selective elements, e.g. multiplexer, demultiplexer}
- G02B 6/12019: {characterised by the optical interconnection to or from the AWG devices, e.g. integration or coupling with lasers or photodiodes (coupling integrated waveguide to fibre G02B6/30, to optoelectronic element G02B6/42; monolithic integration of integrated waveguides with other optical elements G02B6/12004)}
- G02B 6/12026: {characterised by means for reducing the temperature dependence}
- G02B 6/29344: {operating by modal interference or beating, i.e. of transverse modes, e.g. zero-gap directional coupler, MMI}
- G02B 6/29352: {in a light guide}
- G02B 6/2938: {for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM}
- H04B 10/2581: Multimode transmission
- G02B 6/12004: {Combinations of two or more optical elements}
- G02B 6/29328: {Diffractive elements operating in reflection}
- G02B 6/29398: {Temperature insensitivity}
- G02B 2006/1209: {Multimode}
- G02B 2006/12109: {Filter}
- G02B 2006/12123: {Diode}
- G02B 2006/12164: {Multiplexing; Demultiplexing}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H04B: TRANSMISSION

## Abstract

A demultiplexer for use in a wavelength division multiplexed system. The demultiplexer comprises: an input waveguide, configured to receive a wavelength division multiplexed signal; a demultiplexing element, configured to demultiplex the multiplexed signal received from the input waveguide into a plurality of multi-mode demultiplexed signal components; a multi-mode output waveguide, the multi-mode output waveguide being coupled to the demultiplexing element and configured to receive one of the multi-mode demultiplexed signal components; and a splitter, coupled to the multi-mode output waveguide, and configured to split the received multi-mode demultiplexed signal component into two single-mode outputs.

## Claims

### Claim 1

A demultiplexer, for use in a wavelength division multiplexed system, the demultiplexer comprising:
an input waveguide, configured to receive a wavelength division multiplexed signal;
a demultiplexing element, configured to demultiplex the multiplexed signal received from the input waveguide into a plurality of multi-mode demultiplexed signal components;
a multi-mode output waveguide, the multi-mode output waveguide being coupled to the demultiplexing element and configured to receive one of the multi-mode demultiplexed signal components; and
a splitter, coupled to the multi-mode output waveguide, and configured to split the received multi-mode demultiplexed signal component into two single-mode outputs.

### Claim 2 (depends on 1)

The demultiplexer of claim 1, wherein the splitter is configured to split the received multi-mode demultiplexed signal asymmetrically.

### Claim 3 (depends on 1)

The demultiplexer of claim 1, wherein the splitter is configured to split the received multi-mode demultiplexed signal symmetrically.

### Claim 4 (depends on 1)

The demultiplexer of claim 1, wherein the splitter is configured to provide each single-mode output to a respective transfer waveguide.

### Claim 5 (depends on 4)

The demultiplexer of claim 4, wherein the demultiplexer is a receiver and includes a waveguide photodiode, connected at a first end to one of the transfer waveguides and connected at a second end to the other of the transfer waveguides.

### Claim 6 (depends on 5)

The demultiplexer of claim 5, wherein the waveguide photodiode is configured to absorb at least 90% of the signal received from either end within a half of a length of the waveguide photodiode.

### Claim 7 (depends on 4)

The demultiplexer of claim 4, wherein the demultiplexer includes an output Mach-Zehnder interferometer, connected to each of the respective transfer waveguides and operable as a wavelength filter.

### Claim 8 (depends on 1)

The demultiplexer of claim 1, wherein the demultiplexer includes an input Mach-Zehnder interferometer, connected between the input waveguide and the demultiplexing element, the input Mach-Zehnder interferometer being operable as a wavelength filter.

### Claim 9 (depends on 4)

The demultiplexer of any of claim 4, wherein the transfer waveguides have a similar or substantially identical optical path length.

### Claim 10 (depends on 1)

The demultiplexer of claim 1, wherein the demultiplexing element is an arrayed waveguide grating, or an echelle grating.

### Claim 11 (depends on 1)

The demultiplexer of claim 1, wherein the multi-mode output waveguide comprises a pair of waveguide ridges projecting from a shared waveguide slab.

### Claim 12 (depends on 11)

The demultiplexer of claim 11, wherein each waveguide ridge is configured to support a single mode.

### Claim 13 (depends on 1)

The demultiplexer of claim 1, wherein the splitter is a multi-mode interference coupler.

### Claim 14 (depends on 1)

The demultiplexer of claim 1, comprising a plurality of multi-mode output waveguides, each being coupled to the demultiplexing element and configured to receive a respective one of the multi-mode demultiplexed signal components.

### Claim 15 (depends on 14)

The demultiplexer of claim 14, wherein each multi-mode output waveguide is coupled to a respective splitter, each splitter being configured to split the received multi-mode demultiplexed signal component into two single-mode outputs.