# US 10,122,466 B2 · Photonic vector signal generation using heterodyne beating

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

- Number: US 10,122,466 B2
- Document ID: US10122466B2
- Status: Granted
- Kind: B2
- Application number: 15/338,224
- Filed: 2016-10-28
- Published: 2017-05-04
- Granted: 2018-11-06
- Earliest claimed: 2015-10-29
- Assignees: Zte Corporation
- Applicants: ZTE Corporation
- Inventors: Jianjun Yu; Xinying Li
- Web page: https://patentgrep.com/patent/US10122466B2

## CPC

- H04B 10/5161: {Combination of different modulation schemes}
- G02F 1/2255: {controlled by a high-frequency electromagnetic component in an electric waveguide structure}
- H04B 10/556: Digital modulation, e.g. differential phase shift keying [DPSK] or frequency shift keying [FSK]
- H04B 10/572: Wavelength control
- H04B 10/70: Photonic quantum communication
- G02F 1/212: {Mach-Zehnder type}
- H04B: TRANSMISSION
- 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

## Abstract

An exemplary technique of optical signal transmission in which modulated optical signals are generated using photonic heterodyne beating and operating a digital to analog converter at baseband includes receiving information bits, modulating the information bits to generate a precoded vector signal at baseband, generating, using photonic heterodyne beating, from the precoded vector signal at baseband, a precoded vector signal at an upconverted frequency, and transmitting the precoded vector signal at the upconverted frequency on the optical communication network.

## Claims

### Claim 1

A method of optical communication, implemented at a transmitter in an optical communication network, comprising:
receiving information bits;
modulating, using in-phase and quadrature modulation, the information bits to generate a precoded vector signal at baseband;
generating, using photonic heterodyne beating, from the precoded vector signal at baseband, a precoded vector signal at an upconverted frequency, wherein the photonic heterodyne beating includes:
modulating a first optical carrier signal using the precoded vector signal at baseband to generate a carrier-modulated precoded vector signal,
combining, in an optical domain, the carrier modulated precoded vector signal with a second optical carrier signal, wherein the first optical carrier signal and the second optical carrier signal have different frequencies, and
passing a resulting signal of the combining through a photo-detector to generate the precoded vector signal at the upconverted frequency; and
transmitting an optical transmission signal, generated from the precoded vector signal at the upconverted frequency, on the optical communication network.

### Claim 2 (depends on 1)

The method of claim 1, wherein the receiving includes:
receiving information bits from an external network device, wherein the information bits includes data multiplexed together from multiple users.

### Claim 3 (depends on 1)

The method of claim 1, wherein the receiving includes:
receiving information bits locally generated in the transmitter.

### Claim 4 (depends on 1)

The method of claim 1, wherein the modulating includes:
operating a first Mach-Zehnder modulator (MZM) to generate an in-phase modulation output from the precoded vector signal; and
operating a second MZM to generate a quadrature modulation output from the precoded vector signal.

### Claim 5 (depends on 4)

The method of claim 4, wherein the first MZM and the second MZM are operated by biasing at their respective null points and driven at their respective full voltage swings.

### Claim 6 (depends on 1)

The method of claim 1,
wherein the upconverted frequency is equal to a frequency difference between frequencies of the first optical carrier signal and the second optical carrier signal.

### Claim 7 (depends on 1)

The method of claim 1, wherein the modulating the information bits includes using a quadrature phase shift keying (QPSK) modulation scheme.

### Claim 8 (depends on 7)

The method of claim 7, wherein the QPSK modulation scheme is an 8-QPSK modulation scheme.

### Claim 9 (depends on 7)

The method of claim 7, wherein the QPSK modulation scheme is a balanced QPSK modulation scheme.

### Claim 10 (depends on 1)

The method of claim 1, wherein the modulating the information bits includes using an unbalanced modulation scheme.

### Claim 11 (depends on 1)

The method of claim 1, wherein the combining, in the optical domain, the carrier modulated precoded vector signal with a second optical carrier signal, includes combining using an optical coupler.

### Claim 12 (depends on 1)

The method of claim 1, wherein the transmitting is performed by:
performing intensity modulation of a third optical carrier signal to generate two first-order modulated optical subcarriers; and
generating the optical transmission signal by heterodyne beating the two first-order modulated optical subcarriers through a photodetector.

### Claim 13 (depends on 12)

The method of claim 12, wherein the performing intensity modulation includes operating an intensity modulator at a minimum transmission point to implement optical carrier suppression modulation.

### Claim 14 (depends on 1)

The method of claim 1, further including operating the photodetector in a single-ended configuration.

### Claim 15 (depends on 1)

The method of claim 1, wherein the modulating the information bits includes modulating the information bits using a quadrature amplitude modulation (QAM) scheme.

### Claim 16

An optical transmitter apparatus, comprising:
a data interface that receives information bits;
an I/Q modulator that modulates the information bits to generate a precoded vector signal at baseband;
a photonic heterodyne beating subsystem that generates, using photonic heterodyne beating, from the precoded vector signal at baseband, a precoded vector signal at an upconverted frequency, wherein the photonic heterodyne beating subsystem includes:
a first source of a first optical carrier signal is coupled to the I/Q modulator such that the I/Q modulator modulates first optical carrier signal using the precoded vector signal at baseband to generate a carrier-modulated precoded vector signal,
a second source of a second optical carrier signal is coupled to an optical combiner, wherein the first optical carrier signal and the second optical carrier signal have different frequencies,
the optical combiner having two inputs of which a first input is coupled to an output of the I/Q modulator and the second input is coupled to the second source of the second optical carrier signal, thereby combining, in an optical domain, the carrier modulated precoded vector signal with a second optical carrier signal,
a photo-detector coupled to an output of the optical combiner to generate the precoded vector signal at the upconverted frequency; and
an optical transmitter that transmits an optical signal generated from the precoded vector signal at the upconverted frequency on an optical transmission medium.

### Claim 17 (depends on 16)

The transmitter apparatus of claim 16, wherein the I/Q modulator includes:
a first Mach-Zehnder modulator (MZM) having a first input coupled to the data interface and a first output coupled to an adder, the first MZM generating an in-phase modulation output from the precoded vector signal;
a second MZM having a second input coupled to the data interface and a second output coupled to the adder through a phase shifter, the second MZM generating a quadrature modulation output from the precoded vector signal; and
the adder having an adder output for outputting the precoded vector signal at baseband.

### Claim 18 (depends on 17)

The transmitter apparatus of claim 17, wherein the first MZM and the second MZM are operated by biasing at their respective null points and driven at their respective full voltage swings.

### Claim 19 (depends on 16)

The transmitter apparatus of claim 16,
wherein the upconverted frequency is equal to a frequency difference between frequencies of the first optical carrier signal and the second optical carrier signal.

### Claim 20 (depends on 16)

The transmitter apparatus of claim 16, wherein the I/Q modulator is capable of modulating the information bits with a quadrature phase shift keying (QPSK) modulation scheme.

### Claim 21 (depends on 20)

The transmitter apparatus of claim 20, wherein the QPSK modulation scheme is an 8-QPSK modulation scheme.

### Claim 22 (depends on 20)

The transmitter apparatus of claim 20, wherein the QPSK modulation scheme is a balanced QPSK modulation scheme.

### Claim 23 (depends on 16)

The transmitter apparatus of claim 16, wherein the I/Q modulator is capable of modulating the information bits with an unbalanced modulation scheme.

### Claim 24 (depends on 16)

The transmitter apparatus of claim 16, wherein the optical transmitter includes:
an intensity modulator (IM) having an IM input to receive the precoded vector signal at the upconverted frequency, a carrier input to receive an optical carrier signal and an IM output to output a signal that includes two first-order modulated optical subcarriers; and
a photodetector (PD) that includes a PD input coupled to the IM output and a PD output to output the optical transmission signal by heterodyne beating the two first-order modulated optical subcarriers.

### Claim 25 (depends on 24)

The transmitter of apparatus of claim 24, wherein the intensity modulator is capable of operating at a minimum transmission point to implement optical carrier suppression modulation.

### Claim 26 (depends on 24)

The transmitter apparatus of claim 24, wherein the PD is capable of operating in a single-ended configuration.

### Claim 27 (depends on 16)

The transmitter apparatus of claim 16, wherein the I/Q modulator is capable of modulating the information bits using a quadrature amplitude modulation (QAM) scheme.

### Claim 28 (depends on 24)

The transmitter apparatus of claim 24, wherein the intensity modulator (IM) is a Mach-Zehnder modulator (MZM).