# US 9,882,650 B2 · Optical differential signal sending method, apparatus and system

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- Number: US 9,882,650 B2
- Document ID: US9882650B2
- Status: Granted
- Kind: B2
- Application number: 15/189,719
- Filed: 2016-06-22
- Published: 2016-10-13
- Granted: 2018-01-30
- Earliest claimed: 2013-12-23
- Assignees: Huawei Technologies Co., Ltd.
- Applicants: Huawei Technologies Co., Ltd.
- Inventors: Daxin Luo; Tongtong Cao
- Web page: https://patentgrep.com/patent/US9882650B2

## CPC

- H04B 10/548: Phase or frequency modulation
- G02F 1/011: {in optical waveguides, not otherwise provided for in this subclass}
- G02F 1/225: in an optical waveguide structure
- H04B 10/25: Arrangements specific to fibre transmission
- H04B 10/503: {Laser transmitters}
- H04B 10/516: Details of coding or modulation
- H04B 10/677: {for differentially modulated signal, e.g. DPSK signals}
- 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

A system for transmitting optical differential signal includes: an optical source configured to generate two channels of optical signals having different wavelengths; an input end for a to-be-modulated electrical signal configured to input a to-be-modulated electrical signal; a unique optical modulator configured to perform optical modulation on the two channels of optical signals using the to-be-modulated electrical signal, to obtain two channels of modulated optical differential signals; an optical sending unit, configured to send the two channels of modulated optical differential signals to optical transmission media; an optical receiving unit, configured to receive the two channels of optical differential signals; an optical detector, configured to perform optical-to-electrical conversion separately on the two channels of modulated optical differential signals, to obtain two channels of electrical signals; and a comparator configured to perform a differential operation to obtain one channel of electrical signal.

## Claims

### Claim 1

An optical differential signal transmission system, comprising:
a transmit end;
an optical transmission media; and
a receive end;
wherein the transmit end comprises:
an optical source, configured to generate two channels of optical signals having different wavelengths, wherein the wavelengths are respectively λ1 and λ2, and λ1≠λ2;
an input end for a to-be-modulated electrical signal, configured to input a to-be-modulated electrical signal;
a unique optical modulator, configured to perform optical modulation separately on the two channels of optical signals having different wavelengths using the to-be-modulated electrical signal, to obtain two channels of modulated optical differential signals; and
an optical transmitter, configured to send the two channels of modulated optical differential signals to the optical transmission media;
wherein the optical transmission media is connected to the transmit end and the receive end, and is configured to transmit the two channels of modulated optical differential signals; and
wherein the receive end comprises:
an optical receiver, configured to receive the two channels of modulated optical differential signals that are transmitted by the optical transmission media;
an optical detector, configured to perform optical-to-electrical conversion separately on the two channels of modulated optical differential signals that are received by the optical receiver, to obtain two channels of electrical signals; and
a comparator, configured to perform a differential operation on the two channels of electrical signals obtained by the optical detector, to obtain a channel of electrical signal; and output the channel of electrical signal.

### Claim 2 (depends on 1)

The transmission system according to claim 1, wherein the unique optical modulator is an MZI modulator, λ1 and λ2 and meet the following conditions:
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

(
2
⁢
⁢
k
+
1
)
⁢
π
-
ΔΦ
2
<
λ
1
<
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
,
and
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
<
λ
2
<
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

(
2
⁢
⁢
k
-
1
)
⁢
π
-
ΔΦ
2
,
wherein L1 and L2 are respectively lengths of two arms of the MZI modulator, ΔΦ is a variation between phase differences between the two arms of the MZI modulator existing when a modulated electrical input signal applied in the MZI modulator is at a high level and a low level, n is an effective refractive index of a waveguide in the MZI modulator, n>1, k is an integer, and k≧1.

### Claim 3 (depends on 1)

The transmission system according to claim 1, wherein the unique optical modulator is a micro-ring resonant modulator, λ1 and λ2 and meet the following conditions:
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
(
2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
)
<
λ
1
<
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
(
2
⁢
⁢
k
-
1
)
⁢
π
-
ΔΦ
2
,
and
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
(
2
⁢
⁢
k
+
1
)
⁢
π
-
ΔΦ
2
<
λ
2
<
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
,
wherein R is a radius of a micro-ring in the micro-ring resonant modulator, n is an effective refractive index of a waveguide in the micro-ring resonant modulator, n>1, ΔΦ is a variation between phases in the micro-ring existing when a modulated electrical input signal applied in the micro-ring resonant modulator is at a high level and a low level, k is an integer, and k≧1.

### Claim 4 (depends on 1)

The transmission system according to claim 1, wherein the optical source comprises:
a multi-wavelength laser, configured to obtain two channels of optical signals using a beam-splitter, and obtain the two channels of optical signals whose wavelengths are λ1 and λ2 using two filter lenses for processing, wherein output wavelengths of the two filter lenses are respectively λ1 and λ2.

### Claim 5 (depends on 1)

The transmission system according to claim 1, wherein:
the transmit end further comprises an optical demultiplexer, connected to the unique optical modulator and configured to perform de-multiplex processing on the two channels of modulated optical differential signals that are obtained by the unique optical modulator, to obtain two channels of separated optical differential signals;
the optical transmitter is configured to send the two channels of separated optical differential signals to the optical transmission media; and
the optical transmission media comprises two transmission media, respectively configured to transmit the two channels of separated optical differential signals.

### Claim 6 (depends on 4)

The transmission system according to claim 4, wherein the transmit end further comprises:
an optical multiplexer, connected to the optical source and configured to obtain a channel of optical signal by performing multiplex processing on the two channels of optical signals that are generated by the optical source and whose wavelengths are respectively λ1 and λ2, and send the obtained channel of optical signal to the unique optical modulator.

### Claim 7 (depends on 5)

The transmission system according to claim 5, further comprising:
an optical buffer, connected to the optical detector and configured to perform optical buffering on an optical differential signal, whose transmission speed is faster in the optical transmission media, of the two channels of separated optical differential signals, and send the optical differential signal on which optical buffering processing has been performed and an other optical differential signal of the two channels of separated optical differential signals to the optical detector.

### Claim 8

An apparatus, comprising:
an optical source, configured to generate two channels of optical signals having different wavelengths, wherein the wavelengths are respectively λ1 and λ2, and λ1≠λ2;
an input end for a to-be-modulated electrical signal, configured to input a to-be-modulated electrical signal;
a unique optical modulator, configured to perform optical modulation separately on the two channels of optical signals having different wavelengths using the to-be-modulated electrical signal, to obtain two channels of modulated optical differential signals; and
an optical transmitter, configured to send the two channels of modulated optical differential signals.

### Claim 9 (depends on 8)

The apparatus according to claim 8, wherein the unique optical modulator is an MZI modulator, λ1 and λ2 and meet the following conditions:
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

(
2
⁢
⁢
k
+
1
)
⁢
π
-
ΔΦ
2
<
λ
1
<
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
,
and
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
<
λ
2
<
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

(
2
⁢
⁢
k
-
1
)
⁢
π
-
ΔΦ
2
,
wherein L1 and L2 are respectively lengths of two arms of the MZI modulator, ΔΦ is a variation between phase differences between the two arms existing when a modulated electrical input signal applied in the MZI modulator is at a high level and a low level, n is an effective refractive index of a waveguide in the MZI modulator, n≧1, k is an integer, and k≧1.

### Claim 10 (depends on 8)

The apparatus according to claim 8, wherein the unique optical modulator is a micro-ring resonant modulator, λ1 and λ2 and meet the following conditions:
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
(
2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
)
<
λ
1
<
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
(
2
⁢
⁢
k
-
1
)
⁢
π
-
ΔΦ
2
,
and
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
(
2
⁢
⁢
k
+
1
)
⁢
π
-
ΔΦ
2
<
λ
2
<
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
,
wherein R is a radius of a micro-ring in the micro-ring resonant modulator, n is an effective refractive index of a waveguide in the micro-ring resonant modulator, n≧1, ΔΦ is a variation between phases in the micro-ring existing when a modulated electrical input signal applied in the micro-ring resonant modulator is at a high level and a low level, k is an integer, and k≧1.

### Claim 11 (depends on 8)

The apparatus according to claim 8, wherein the optical source comprises:
a multi-wavelength laser, configured to obtain two channels of optical signals using a beam-splitter, and to obtain the two channels of optical signals whose wavelengths are λ1 and λ2 using two filter lenses for processing, wherein output wavelengths of the two filter lenses are respectively λ1 and λ2.

### Claim 12 (depends on 8)

The apparatus according to claim 8, further comprising an optical demultiplexer, connected to the unique optical modulator, and configured to perform de-multiplex processing on the two channels of modulated optical differential signals that are obtained by the unique optical modulator, and to obtain two channels of separated optical differential signals;
wherein the optical transmitter is configured to send the two channels of separated optical differential signals.

### Claim 13 (depends on 11)

The apparatus according to claim 11, further comprising:
an optical multiplexer, connected to the optical source and configured to perform multiplex processing on the two channels of optical signals that are generated by the optical source and whose wavelengths are respectively λ1 and λ2, and to send one obtained channel of optical signal to the unique optical modulator.

### Claim 14

A method, comprising:
generating two channels of optical signals having different wavelengths using an optical source, wherein the wavelengths are respectively λ1 and λ2, and λ1≠λ2;
performing optical modulation with a unique optical modulator on the two channels of optical signals using a to-be-modulated electrical signal, to obtain two channels of modulated optical differential signals; and
sending the two channels of optical differential signals to a receive end.

### Claim 15 (depends on 14)

The method according to claim 14, wherein optical modulation is performed on the to-be-modulated electrical signal using an MZI modulator, λ1 and λ2 and meet the following conditions:
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

(
2
⁢
⁢
k
+
1
)
⁢
π
-
ΔΦ
2
<
λ
1
<
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
,
and
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
<
λ
2
<
2
⁢
π
⁢
⁢
n
*

L
1
-
L
2

(
2
⁢
⁢
k
-
1
)
⁢
π
-
ΔΦ
2
,
wherein L1 and L2 are respectively lengths of two arms of the MZI modulator, ΔΦ is a variation between phase differences between the two arms existing when a modulated electrical input signal applied in the MZI modulator is at a high level and a low level, n is an effective refractive index of a waveguide in the MZI modulator, n>1, k is an integer, and k≧1.

### Claim 16 (depends on 14)

The method according to claim 14, wherein optical modulation is performed on the to-be-modulated electrical signal using a micro-ring resonant modulator, and λ1 and λ2 meet the following conditions:
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
(
2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
)
<
λ
1
<
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
(
2
⁢
⁢
k
-
1
)
⁢
π
-
ΔΦ
2
,
and
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
(
2
⁢
⁢
k
+
1
)
⁢
π
-
ΔΦ
2
<
λ
2
<
2
⁢
π
⁢
⁢
n
*
2
⁢
π
⁢
⁢
R
2
⁢
⁢
k
⁢
⁢
π
-
ΔΦ
2
,
wherein R is a radius of a micro-ring in the micro-ring resonant modulator, n is an effective refractive index of a waveguide in the micro-ring resonant modulator, n>1, ΔΦ is a variation between phases in the micro-ring existing when a modulated electrical input signal applied in the micro-ring resonant modulator is at a high level and a low level, k is an integer, and k≧1.

### Claim 17 (depends on 14)

The method according to claim 14, further comprising:
performing de-multiplex processing on the two channels of modulated optical differential signals, to obtain two channels of separated optical differential signals, and sending the two channels of separated optical differential signals.