# US 8,787,708 B2 · Endless phase shifting

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- Number: US 8,787,708 B2
- Document ID: US8787708B2
- Status: Granted
- Kind: B2
- Application number: 13/210,299
- Filed: 2011-08-15
- Published: 2013-02-21
- Granted: 2014-07-22
- Earliest claimed: 2011-08-15
- Assignees: Alcatel Lucent
- Applicants: Christopher Doerr
- Inventors: Christopher Doerr
- Web page: https://patentgrep.com/patent/US8787708B2

## CPC

- G02F 1/225: in an optical waveguide structure
- G02F 1/3136: {of interferometric switch type}
- H04B 10/615: {Arrangements affecting the optical part of the receiver}
- H04B 10/671: {for controlling the input optical signal}
- G02B 2006/12142: {Modulator}
- G02F 1/212: {Mach-Zehnder type}
- 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
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

Endless phase shifting apparatus, structures, and methods useful—for example—in MIMO optical demultiplexing.

## Claims

### Claim 1

An optical apparatus comprising:
a first Mach-Zehnder interferometer (MZI) switch including a phase shifter;
a second MZI switch including a phase shifter; and
a line phase shifter structure optically connecting the first MZI to the second MZI, said line phase shifter structure including two waveguides, at least one of the waveguides having a phase shifter;
wherein the phase shifter included in the first MZI switch and the phase shifter included in the second MZI switch are configured to substantially simultaneously switch from π/2 to 3π/2 and 3π/2 to π/2 respectively, in response to a value of substantially 0 or 4π exhibited by the line phase shifter.

### Claim 2 (depends on 1)

The optical apparatus of claim 1 wherein the two waveguides in the line phase shifter structure have a path-length difference less than 10 microns.

### Claim 3 (depends on 1)

The optical apparatus of claim 1 wherein the line phase shifter structure is optically connected to the first MZI switch and the second MZI switch by a first and second 2×2 optical coupler, respectively.

### Claim 4 (depends on 1)

The optical apparatus of claim 1 wherein the overall phase of the optical apparatus is preserved after the substantially simultaneous switch.

### Claim 5 (depends on 1)

The optical apparatus of claim 1 further comprising a controller connected to at least one of the phase shifters.

### Claim 6 (depends on 5)

The optical apparatus of claim 5 wherein the controller is connected to an output signal of the apparatus.

### Claim 7 (depends on 1)

The optical apparatus of claim 1 operable to reset the phase shifter in one of the waveguides when there is no light in that waveguide.

### Claim 8 (depends on 5)

The optical apparatus of claim 5 operable to monotonically increase an optical phase of an optical signal by an amount of more than 1000 radians.

### Claim 9 (depends on 1)

The optical apparatus of claim 1 further comprising a controller connected to the phase shifters in the first MZI, the second MZI, and the line phase shifter structure, for controlling the phase(s) of the respective phase shifters.

### Claim 10 (depends on 9)

The optical apparatus of claim 9 operable to monotonically increase an optical phase of an optical signal by an amount of more than 1000 radians.