U.S. patent application number 17/185484 was filed with the patent office on 2021-08-26 for optical receiver with separated magnitude modulation and phase modulation and operation method thereof.
This patent application is currently assigned to Electronics and Telecommunications Research Institute. The applicant listed for this patent is Electronics and Telecommunications Research Institute. Invention is credited to Jong-Hoi KIM.
Application Number | 20210266074 17/185484 |
Document ID | / |
Family ID | 1000005764835 |
Filed Date | 2021-08-26 |
United States Patent
Application |
20210266074 |
Kind Code |
A1 |
KIM; Jong-Hoi |
August 26, 2021 |
OPTICAL RECEIVER WITH SEPARATED MAGNITUDE MODULATION AND PHASE
MODULATION AND OPERATION METHOD THEREOF
Abstract
Disclosed is an optical receiver. The optical receiver includes
an optical splitter that splits an external light signal to output
a first light signal and a second light signal, a first amplifier
that amplifies the first light signal in a linear gain section to
output an amplified first light signal, a second amplifier that
amplifies the second light signal in a saturation gain section to
output an amplified second light signal, a polarization division
hybrid that outputs an in-phase hybrid light signal and a
quadrature-phase hybrid light signal, based on a reference light
signal and the amplified second light signal, and an optoelectronic
conversion unit that outputs an electrical signal, based on the
amplified first light signal, the in-phase hybrid light signal, and
the quadrature-phase hybrid light signal.
Inventors: |
KIM; Jong-Hoi; (Daejeon,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Electronics and Telecommunications Research Institute |
Daejeon |
|
KR |
|
|
Assignee: |
Electronics and Telecommunications
Research Institute
Daejeon
KR
|
Family ID: |
1000005764835 |
Appl. No.: |
17/185484 |
Filed: |
February 25, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 10/6931 20130101;
H04B 10/673 20130101; H04B 10/691 20130101 |
International
Class: |
H04B 10/69 20060101
H04B010/69; H04B 10/67 20060101 H04B010/67 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 2020 |
KR |
10-2020-0023568 |
Claims
1. An optical receiver comprising: an optical splitter configured
to split an external light signal to output a first light signal
and a second light signal; a first amplifier configured to amplify
the first light signal in a linear gain section to output an
amplified first light signal; a second amplifier configured to
amplify the second light signal in a saturation gain section to
output an amplified second light signal; a polarization division
hybrid configured to output an in-phase hybrid light signal and a
quadrature-phase hybrid light signal, based on a reference light
signal and the amplified second light signal; and an optoelectronic
conversion unit configured to output an electrical signal, based on
the amplified first light signal, the in-phase hybrid light signal,
and the quadrature-phase hybrid light signal.
2. The optical receiver of claim 1, wherein a luminous intensity of
the second light signal is greater than that of the first light
signal.
3. The optical receiver of claim 1, wherein the optical splitter
includes: an optical attenuator configured to attenuate a luminous
intensity of the external light signal; and an asymmetric optical
splitter configured to receive the attenuated external light signal
from the optical attenuator, to asymmetrically split the attenuated
external light signal into the first light signal and the second
light signal, and to output the first light signal and the second
light signal to the first amplifier and the second amplifier,
respectively.
4. The optical receiver of claim 1, wherein the optical splitter
includes: an optical splitting unit configured to split the
external light signal into a first split light signal and a second
split light signal that have the same luminous intensity; a first
optical attenuator configured to output the first light signal
obtained by attenuating the first split light signal by a first
attenuation coefficient to the first amplifier; and a second
optical attenuator configured to output the second light signal
obtained by attenuating the second split light signal by a second
attenuation coefficient less than the first attenuation coefficient
to the second amplifier.
5. The optical receiver of claim 1, wherein the first amplifier is
further configured to increase a difference in luminous intensity
of the first light signal received from the optical splitter.
6. The optical receiver of claim 1, wherein the second amplifier is
further configured to decrease a difference in luminous intensity
of the second light signal received from the optical splitter.
7. The optical receiver of claim 1, wherein a difference in
luminous intensity of the amplified first light signal is greater
than that of the amplified second light signal.
8. The optical receiver of claim 1, wherein each of the first and
second amplifiers is a gain clamped semiconductor optical
amplifier.
9. The optical receiver of claim 1, wherein the second amplifier
includes an offset circuit that offsets an effect of an external
disturbance on an amplification of the second light signal.
10. The optical receiver of claim 1, wherein the optoelectronic
conversion unit is further configured to convert the amplified
first light signal to output a first electrical signal for
demodulating a magnitude component of the external light signal,
and to convert the in-phase hybrid light signal and the
quadrature-phase hybrid light signal to output at least one of a
second electrical signal for demodulating a phase component of the
external light signal, and wherein the electrical signal includes
the first electrical signal and the at least one of the second
electrical signal.
11. An optical receiver comprising: an optical splitter configured
to split an external light signal to output a first light signal
and a second light signal having a greater luminous intensity than
that of the first light signal; a first amplifier configured to
output an amplified first light signal, based on the first light
signal; a second amplifier configured to output an amplified second
light signal, based on the second light signal; a polarization
division hybrid configured to output an in-phase hybrid light
signal and a quadrature-phase hybrid light signal, based on a
reference light signal and the amplified second light signal; and
an optoelectronic conversion unit configured to output an
electrical signal, based on the amplified first light signal, the
in-phase hybrid light signal, and the quadrature-phase hybrid light
signal.
12. The optical receiver of claim 11, wherein the first amplifier
and the second amplifier have a linear gain section corresponding
to a luminous intensity range of the first light signal and a
saturation gain section corresponding to a luminous intensity range
of the second light signal, respectively.
13. The optical receiver of claim 11, wherein the optical splitter
includes: an optical attenuator configured to attenuate a luminous
intensity of the external light signal; and an asymmetric optical
splitter configured to receive the attenuated external light signal
from the optical attenuator, to asymmetrically split the attenuated
external light signal into the first light signal and the second
light signal, and to output the first light signal and the second
light signal to the first amplifier and the second amplifier,
respectively.
14. The optical receiver of claim 11, wherein the optical splitter
includes: an optical splitting unit configured to split the
external light signal into a first split light signal and a second
split light signal that have the same luminous intensity; a first
optical attenuator configured to output the first light signal
obtained by attenuating the first split light signal by a first
attenuation coefficient to the first amplifier; and a second
optical attenuator configured to output the second light signal
obtained by attenuating the second split light signal by a second
attenuation coefficient less than the first attenuation coefficient
to the second amplifier.
15. A method of operating an optical receiver, the method
comprising: receiving an external light signal and a reference
light signal; generating a first light signal and a second light
signal, based on the external light signal; amplifying the first
light signal in a linear gain section and amplifying the second
light signal in a saturation gain section; generating an in-phase
hybrid light signal and a quadrature-phase hybrid light signal,
based on the reference light signal and the amplified second light
signal; and processing the amplified first light signal, the
in-phase hybrid light signal, and the quadrature-phase hybrid light
signal.
16. The method of claim 15, the generating of the first light
signal and the second light signal includes: attenuating a luminous
intensity of the external light signal; and asymmetrically
splitting the attenuated external light signal into the first light
signal and the second light signal having a greater luminous
intensity than that of the first light signal.
17. The method of claim 15, wherein the generating of the first
light signal and the second light signal includes: splitting the
external light signal into a first split light signal and a second
split light signal that have the same luminous intensity;
generating the first light signal obtained by attenuating the first
split light signal by a first attenuation coefficient; and
generating the second light signal obtained by attenuating the
second split light signal by a second attenuation coefficient less
than the first attenuation coefficient.
18. The method of claim 15, wherein the amplifying of the first
light signal in the linear gain section and the amplifying of the
second light signal in the saturation gain section includes:
amplifying the first light signal to increase a difference in
luminous intensity of the first light signal; and amplifying the
second light signal to decrease a difference in luminous intensity
of the second light signal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. .sctn. 119
to Korean Patent Application No. 10-2020-0023568 filed on Feb. 26,
2020, in the Korean Intellectual Property Office, the disclosures
of which are incorporated by reference herein in their
entireties.
BACKGROUND
[0002] Embodiments of the present disclosure described herein
relate to an optical receiver and an operation method thereof, and
more particularly, relate to an optical receiver in which a
magnitude modulation and a phase modulation are separated in a
quadrature amplitude modulation (QAM), and an operation method
thereof.
[0003] Optical communication refers to a communication method in
which information is exchanged using total reflection of light
through an optical fiber. To increase the data transmission
capacity in the optical communication, a higher-order modulation
method is used in which two or more bits are transmitted in one
symbol when a light signal is generated. Among the higher-order
modulation methods, there is a quadrature amplitude modulation
(QAM) type modulation in which a capacity of data is increased by
adding a magnitude modulation to a quadrature phase shift keying
(QPSK) type modulation.
[0004] Recently, as mobile communication technologies are developed
and demand for large-capacity services such as high-quality video
streaming is increased, data transmission capacity in optical
communication is increasing. Accordingly, in an optical
communication device, improvement in communication quality and
signal processing speed, and enhancing of power consumption are
required.
SUMMARY
[0005] Embodiments of the present disclosure provide an optical
receiver in which a magnitude modulation and a phase modulation are
separated, and an operation method thereof.
[0006] According to an embodiment of the present disclosure, an
optical receiver includes an optical splitter that splits an
external light signal to output a first light signal and a second
light signal, a first amplifier that amplifies the first light
signal in a linear gain section to output an amplified first light
signal, a second amplifier that amplifies the second light signal
in a saturation gain section to output an amplified second light
signal, a polarization division hybrid that outputs an in-phase
hybrid light signal and a quadrature-phase hybrid light signal,
based on a reference light signal and the amplified second light
signal, and an optoelectronic conversion unit that outputs an
electrical signal, based on the amplified first light signal, the
in-phase hybrid light signal, and the quadrature-phase hybrid light
signal.
[0007] According to an embodiment, a luminous intensity of the
second light signal may be greater than that of the first light
signal.
[0008] According to an embodiment, the optical splitter may include
an optical attenuator that attenuates a luminous intensity of the
external light signal, and an asymmetric optical splitter that
receives the attenuated external light signal from the optical
attenuator, asymmetrically splits the attenuated external light
signal into the first light signal and the second light signal, and
outputs the first light signal and the second light signal to the
first amplifier and the second amplifier, respectively.
[0009] According to an embodiment, the optical splitter may include
an optical splitting unit that splits the external light signal
into a first split light signal and a second split light signal
that have the same luminous intensity, a first optical attenuator
that outputs the first light signal obtained by attenuating the
first split light signal by a first attenuation coefficient to the
first amplifier, and a second optical attenuator that outputs the
second light signal obtained by attenuating the second split light
signal by a second attenuation coefficient less than the first
attenuation coefficient to the second amplifier.
[0010] According to an embodiment, the first amplifier may be
further configured to increase a difference in luminous intensity
of the first light signal received from the optical splitter.
[0011] According to an embodiment, the second amplifier may be
further configured to decrease a difference in luminous intensity
of the second light signal received from the optical splitter.
[0012] According to an embodiment, a difference in luminous
intensity of the amplified first light signal may be greater than
that of the amplified second light signal.
[0013] According to an embodiment, each of the first and second
amplifiers may be a gain clamped semiconductor optical
amplifier.
[0014] According to an embodiment, the second amplifier may include
an offset circuit that offsets an effect of an external disturbance
on an amplification of the second light signal.
[0015] According to an embodiment, the optoelectronic conversion
unit may be further configured to convert the amplified first light
signal to output a first electrical signal for demodulating a
magnitude component of the external light signal, and to convert
the in-phase hybrid light signal and the quadrature-phase hybrid
light signal to output at least one of a second electrical signal
for demodulating a phase component of the external light signal,
and the electrical signal may include the first electrical signal
and the at least one of the second electrical signal.
[0016] According to an embodiment of the present disclosure, an
optical receiver includes an optical splitter that splits an
external light signal to output a first light signal and a second
light signal having a greater luminous intensity than that of the
first light signal, a first amplifier that outputs an amplified
first light signal, based on the first light signal, a second
amplifier that outputs an amplified second light signal, based on
the second light signal, a polarization division hybrid that
outputs an in-phase hybrid light signal and a quadrature-phase
hybrid light signal, based on a reference light signal and the
amplified second light signal, and an optoelectronic conversion
unit that outputs an electrical signal, based on the amplified
first light signal, the in-phase hybrid light signal, and the
quadrature-phase hybrid light signal.
[0017] According to an embodiment, the first amplifier and the
second amplifier may have a linear gain section corresponding to a
luminous intensity range of the first light signal and a saturation
gain section corresponding to a luminous intensity range of the
second light signal, respectively.
[0018] According to an embodiment, the optical splitter may include
an optical attenuator that attenuates a luminous intensity of the
external light signal, and an asymmetric optical splitter that
receives the attenuated external light signal from the optical
attenuator, asymmetrically splits the attenuated external light
signal into the first light signal and the second light signal, and
outputs the first light signal and the second light signal to the
first amplifier and the second amplifier, respectively.
[0019] According to an embodiment, the optical splitter may include
an optical splitting unit that splits the external light signal
into a first split light signal and a second split light signal
that have the same luminous intensity, a first optical attenuator
that outputs the first light signal obtained by attenuating the
first split light signal by a first attenuation coefficient to the
first amplifier, and a second optical attenuator that outputs the
second light signal obtained by attenuating the second split light
signal by a second attenuation coefficient less than the first
attenuation coefficient to the second amplifier.
[0020] According to an embodiment of the present disclosure, a
method of operating an optical receiver includes receiving an
external light signal and a reference light signal, generating a
first light signal and a second light signal, based on the external
light signal, amplifying the first light signal in a linear gain
section and amplifying the second light signal in a saturation gain
section, generating an in-phase hybrid light signal and a
quadrature-phase hybrid light signal, based on the reference light
signal and the amplified second light signal, and processing the
amplified first light signal, the in-phase hybrid light signal, and
the quadrature-phase hybrid light signal.
[0021] According to an embodiment, the generating of the first
light signal and the second light signal may include attenuating a
luminous intensity of the external light signal, and asymmetrically
splitting the attenuated external light signal into the first light
signal and the second light signal having a greater luminous
intensity than that of the first light signal.
[0022] According to an embodiment, the generating of the first
light signal and the second light signal may include splitting the
external light signal into a first split light signal and a second
split light signal that have the same luminous intensity,
generating the first light signal obtained by attenuating the first
split light signal by a first attenuation coefficient, and
generating the second light signal obtained by attenuating the
second split light signal by a second attenuation coefficient less
than the first attenuation coefficient.
[0023] According to an embodiment, the amplifying of the first
light signal in the linear gain section and the amplifying of the
second light signal in the saturation gain section may include
amplifying the first light signal to increase a difference in
luminous intensity of the first light signal, and amplifying the
second light signal to decrease a difference in luminous intensity
of the second light signal.
BRIEF DESCRIPTION OF THE FIGURES
[0024] The above and other objects and features of the present
disclosure will become apparent by describing in detail embodiments
thereof with reference to the accompanying drawings.
[0025] FIG. 1 is a diagram illustrating an optical receiving device
according to an embodiment of the present disclosure.
[0026] FIG. 2 is a detailed diagram illustrating an optical
receiver of FIG. 1.
[0027] FIG. 3 is a graph illustrating an operation region of a
first amplifier of FIG. 2.
[0028] FIG. 4 is a graph illustrating an operation region of a
second amplifier of FIG. 2.
[0029] FIG. 5 is a detailed diagram illustrating an optical
splitter of FIG. 2.
[0030] FIG. 6 is a detailed diagram illustrating an optical
splitter of FIG. 2.
[0031] FIG. 7 is a detailed diagram illustrating a polarization
division hybrid of FIG. 2.
[0032] FIG. 8 is a detailed diagram illustrating an optoelectronic
conversion unit of FIG. 2.
[0033] FIG. 9 is a flowchart describing an operation method of an
optical receiver according to an embodiment of the present
disclosure.
DETAILED DESCRIPTION
[0034] Hereinafter, embodiments of the present disclosure will be
described clearly and in detail such that those skilled in the art
may easily carry out the present disclosure.
[0035] Terms such as "unit" and "module" used below, or functional
blocks illustrated in the drawings may be implemented in the form
of a software configuration, a hardware configuration, or a
combination thereof. Hereinafter, to clearly describe the technical
idea of the present disclosure, detailed descriptions of redundant
components will be omitted.
[0036] FIG. 1 is a diagram illustrating an optical receiving device
according to an embodiment of the present disclosure. Referring to
FIG. 1, an optical receiving device 100 is illustrated as an
example. The optical receiving device 100 may be a device that
processes a light signal LS used in optical communication. The
light signal LS may be a modulated signal including a series of
data. The optical receiving device 100 may include a reference
light signal generator 110, an optical receiver 120, and a signal
processor 130. The reference light signal generator 110 may
generate a reference light signal RLS used for a phase
modulation.
[0037] The optical receiver 120 may receive the light signal LS
from the outside. For example, the optical receiver 120 may receive
the light signal LS from a separate optical transmission module
(not illustrated). The optical receiver 120 may receive the
reference light signal RLS from the reference light signal
generator 110. The optical receiver 120 may generate an electrical
signal ES, based on the light signal LS and the reference light
signal RLS. The electrical signal ES may include data of the light
signal LS. The specific operation of the optical receiver 120 will
be described later with reference to FIG. 2.
[0038] The signal processor 130 may receive the electrical signal
ES from the optical receiver 120. The signal processor 130 may
process the electrical signal ES. For example, the signal processor
130 may restore data included in the light signal LS by
demodulating the electrical signal ES.
[0039] In an embodiment, the light signal LS may be a modulated
signal, based on a quadrature amplitude modulation (QAM). The
quadrature amplitude modulation method is one of higher-order
modulation methods, and may be a method in which a magnitude
modulation is added to a quadrature phase shift keying (QPSK)
method that a phase modulation uses an in-phase and a
quadrature-phase.
[0040] In this case, the electrical signal ES may include a signal
corresponding to a magnitude component of the light signal LS and a
signal corresponding to a phase component of the light signal LS.
The signal processor 130 may demodulate the magnitude component of
the light signal LS. The signal processor 130 may demodulate the
phase component of the light signal LS. The signal processor 130
may restore data included in the light signal LS, based on the
demodulated magnitude component and the demodulated phase
component.
[0041] FIG. 2 is a detailed diagram illustrating an optical
receiver of FIG. 1. Referring to FIG. 2, the optical receiver 120
is illustrated as an example. The optical receiver 120 may include
an optical splitter 121, a first amplifier 122, a second amplifier
123, a polarization division hybrid 124, and an optoelectronic
conversion unit 125.
[0042] The optical splitter 121 may receive the light signal LS.
The optical splitter 121 may generate a first light signal LS1 and
a second light signal LS2, based on the light signal LS. The
optical splitter 121 may output the first light signal LS1 and the
second light signal LS2 to the first amplifier 122 and the second
amplifier 123, respectively. In this case, a sum of a luminous
intensity of the first and second light signals LS1 and LS2 may be
less than that of the light signal LS. The luminous intensity of
the first light signal LS1 may be different from the luminous
intensity of the second light signal LS2. In detail, the optical
splitter 121 may be a module that attenuates and asymmetrically
splits the light signal LS.
[0043] In an embodiment, the luminous intensity of the second light
signal LS2 may be greater than the luminous intensity of the first
light signal LS1.
[0044] The first amplifier 122 may receive the first light signal
LS1 from the optical splitter 121. The first amplifier 122 may
output an amplified first light signal ALS1 to the optoelectronic
conversion unit 125. The amplified first light signal ALS1 may be a
signal obtained by amplifying the first light signal LS1. In
detail, the first amplifier 122 may be a module that amplifies
light.
[0045] In an embodiment, the first amplifier 122 may increase a
difference in luminous intensity of the first light signal LS1
received from the optical splitter 121. For example, a difference
in luminous intensity of the amplified first light signal ALS1 may
be greater than a difference in luminous intensity of the first
light signal LS1. As the difference in luminous intensity between a
low luminous intensity and a high luminous intensity increases in
the amplified first light signal ALS1, it is possible to easily
determine the luminous intensity corresponding to the magnitude
component of the quadrature amplitude modulation. In detail, the
amplified first light signal ALS1 may be a preprocessed light
signal suitable for demodulation of the magnitude component. A
detailed description related to these will be described later with
reference to FIG. 3.
[0046] The second amplifier 123 may receive the second light signal
LS2 from the optical splitter 121. The second amplifier 123 may
output an amplified second light signal ALS2 to the polarization
division hybrid 124. The amplified second light signal ALS2 may be
a signal obtained by amplifying the second light signal LS2. In
detail, the second amplifier 123 may be a module that amplifies
light.
[0047] In an embodiment, the second amplifier 123 may decrease a
difference in luminous intensity of the second light signal LS2
received from the optical splitter 121. For example, the difference
in luminous intensity of the amplified second light signal ALS2 may
be less than the difference in luminous intensity of the second
light signal LS2. As the difference in luminous intensity between a
low luminous intensity and a high luminous intensity decreases
(i.e., as the luminous intensity is flattened) in the amplified
second light signal ALS2, a change in magnitude component that
interferes with the demodulation of the phase component of the
quadrature amplitude modulation may be controlled. In detail, the
amplified second light signal ALS2 may be a preprocessed light
signal suitable for demodulation of the phase component. A detailed
description related to these will be described later with reference
to FIG. 4.
[0048] In an embodiment, the difference in luminous intensity of
the amplified first light signal ALS1 may be greater than the
difference in luminous intensity of the amplified second light
signal ALS2. In detail, the amplified first light signal ALS1 may
be a light signal suitable for demodulation of the magnitude
component than the amplified second light signal ALS2. The
amplified second light signal ALS2 may be a light signal suitable
for demodulation of the phase component than the amplified first
light signal ALS1.
[0049] In an embodiment, the second amplifier 123 may include an
offset circuit that offsets an effect of an external disturbance on
the amplification of the second light signal LS2. For example, the
offset circuit may operate to offset the effect of external
disturbances such as a change in driving voltage supplied to the
second amplifier 123, a current leaking from another adjacent
circuit, an internal heat generation of the optical receiver 120,
and a change in an external temperature, on the phase of the second
light signal LS2.
[0050] In an embodiment, each of the first and second amplifiers
122 and 123 may be a gain clamped semiconductor optical amplifier.
For example, each of the first and second amplifiers 122 and 123
may have a saturation gain section in which an amplification gain
is uniform (or a change in amplification gain is small), despite a
change in luminous intensity of an input light signal. A detailed
description related to the saturation gain section will be
described later with reference to FIG. 4.
[0051] In an embodiment, the first amplifier 122 and the second
amplifier 123 may be the same amplifier. For example, a difference
in characteristics between the amplified first and second light
signals ALS1 and ALS2 may be based on a difference in luminous
intensity between the first and second light signals LS1 and LS2,
not a difference in operating characteristics between the first and
second amplifiers 122 and 123.
[0052] The polarization division hybrid 124 may receive the
amplified second light signal ALS2 from the second amplifier 123.
The polarization division hybrid 124 may receive the reference
light signal RLS from the reference light signal generator 110. The
polarization division hybrid 124 may polarize and separate the
amplified second light signal ALS2 and the reference light signal
RLS into an in-phase component and a quadrature-phase component,
and may generate in-phase and quadrature-phase hybrid light signals
HSI and HSQ, based on the polarized and separated light
signals,
[0053] In this case, the in-phase hybrid light signal HSI may be a
signal obtained by combining signals of the in-phase component
among the polarized and separated light signals. The
quadrature-phase hybrid light signal HSQ may be a signal obtained
by combining signals of the quadrature-phase component among the
polarized and separated light signals. The in-phase and
quadrature-phase hybrid light signals HSI and HSQ may be signals
used for demodulating the phase component of the light signal
LS.
[0054] The polarization division hybrid 124 may output the in-phase
and quadrature-phase hybrid light signals HSI and HSQ to the
optoelectronic conversion unit 125. In detail, the polarization
division hybrid 124 may be a module that polarizes, separates, and
combines light signals. A detailed description related to these
will be described later with reference to FIG. 7.
[0055] The optoelectronic conversion unit 125 may receive the
amplified first light signal ALS1 from the first amplifier 122. The
optoelectronic conversion unit 125 may receive the in-phase and
quadrature-phase hybrid light signals HSI and HSQ from the
polarization division hybrid 124. The optoelectronic conversion
unit 125 may output the electrical signal ES to the signal
processor 130. The electrical signal ES may include electrical
signals that are obtained by converting the amplified first light
signal ALS1, the in-phase hybrid light signal HSI, and the
quadrature-phase hybrid light signal HSQ, respectively. The
optoelectronic conversion may mean converting light energy of the
light signal into electrical energy. In detail, the optoelectronic
conversion unit 125 may be a module that converts the light
signal.
[0056] As described above, according to an embodiment of the
present disclosure, an optical receiver that separates and
processes a light signal used for demodulation of the magnitude
component and a light signal used for demodulation of the phase
component may be provided.
[0057] FIG. 3 is a graph illustrating an operation region of a
first amplifier of FIG. 2. Referring to FIG. 3, a gain curve of the
first amplifier 122 of FIG. 2 is illustrated by way of example. A
horizontal axis represents the luminous intensity of the light
signal input to the first amplifier 122. A vertical axis represents
the luminous intensity of the light signal output from the first
amplifier 122. For convenience of description, it will be described
with reference to FIGS. 2 and 3 together.
[0058] In an embodiment, the first amplifier 122 may amplify the
light signal in a linear gain section. The linear gain section may
be a section in which the first amplifier 122 linearly (or almost
linearly) amplifies the received light signal. In more detail, the
first amplifier 122 may linearly amplify the first light signal LS1
having the luminous intensity between a first input luminous
intensity I1 and a second input luminous intensity 12, and may
generate the amplified first light signal ALS1 having the luminous
intensity between a first output luminous intensity O1 and a second
output luminous intensity O2. In this case, as the luminous
intensity of the first light signal LS1 is linearly amplified, a
variation in luminous intensity corresponding to the magnitude
component of the first light signal LS1 may not be distorted.
[0059] In an embodiment, the first amplifier 122 may increase a
difference in luminous intensity of the light signal. For example,
the difference between the first output luminous intensity O1 and
the second output luminous intensity O2 may be greater than the
difference between the first input luminous intensity I1 and the
second input luminous intensity I2.
[0060] As described above, according to an embodiment of the
present disclosure, the first amplifier 122 may include the linear
gain section in which the luminous intensity of an input light
signal is linearly amplified.
[0061] FIG. 4 is a graph illustrating an operation region of a
second amplifier of FIG. 2. Referring to FIG. 4, a gain curve of
the second amplifier 123 of FIG. 2 is illustrated by way of
example. A horizontal axis represents the luminous intensity of the
light signal input to the second amplifier 123. A vertical axis
represents the luminous intensity of the light signal output from
the second amplifier 123. For convenience of description, it will
be described with reference to FIGS. 2 and 4 together.
[0062] In an embodiment, the second amplifier 123 may amplify the
light signal in the saturation gain section. The saturation gain
section may be a section in which the amplifier amplifies the light
signal such that the luminous intensity of the received light
signal is flattened. In more detail, the second amplifier 123 may
amplify the second light signal LS2 having the luminous intensity
between a third input luminous intensity 13 and a fourth input
luminous intensity 14 such that the luminous intensity is
flattened, and may generate the amplified second light signal ALS2
having the luminous intensity between a third output luminous
intensity O3 and a fourth output luminous intensity O4. In this
case, as the second light signal LS2 is amplified such that the
luminous intensity of the second light signal LS2 is flattened, a
change in the magnitude component that interferes with the
demodulation of the phase component may be controlled.
[0063] In an embodiment, the second amplifier 123 may reduce a
difference in luminous intensity of the light signal. For example,
the difference in luminous intensity between the third output
luminous intensity O3 and the fourth output luminous intensity O4
may be less than the difference in luminous intensity between the
third input luminous intensity 13 and the fourth input luminous
intensity 14.
[0064] As described above, according to an embodiment of the
present disclosure, the second amplifier 123 may include the
saturation gain section in which the amplifier amplifies the light
signal such that the luminous intensity of the input light signal
is flattened.
[0065] FIG. 5 is a detailed diagram illustrating an optical
splitter of FIG. 2. Referring to FIG. 5, an optical splitter 121a
according to a first embodiment is illustrated. The optical
splitter 121a may receive the light signal LS. The optical splitter
121a may attenuate the light signal LS and may output the first and
second light signals LS1 and LS2 that are asymmetrically split to
the first and second amplifiers 122 and 123, respectively.
[0066] The optical splitter 121a may include a variable optical
attenuator 121a-1 and an asymmetric optical splitter 121a-2. The
variable optical attenuator 121a-1 may receive the light signal LS.
The variable optical attenuator 121a-1 may output an attenuated
light signal LSx to the asymmetric optical splitter 121a-2. The
luminous intensity of the attenuated light signal LSx may be less
than the luminous intensity of the light signal LS. In detail, the
variable optical attenuator 121a-1 may be a module that attenuates
the luminous intensity of the light signal LS.
[0067] The asymmetric optical splitter 121a-2 may receive the
attenuated light signal LSx from the variable optical attenuator
121a-1. The asymmetric optical splitter 121a-2 may output the first
and second light signals LS1 and LS2 obtained by asymmetrically
splitting the attenuated light signal LSx to the first and second
amplifiers 122 and 123, respectively.
[0068] In an embodiment, the asymmetric optical splitter 121a-2 may
asymmetrically split the attenuated light signal LSx such that the
luminous intensity of the second light signal LS2 is greater than
the luminous intensity of the first light signal LS1. The luminous
intensity of the first light signal LS1 may be included in a
luminous intensity range corresponding to the linear gain section
of the first amplifier 122. The luminous intensity of the second
light signal LS2 may be included in a luminous intensity range
corresponding to the saturation gain section of the second
amplifier 123.
[0069] As described above, according to the first embodiment of the
present disclosure, the optical splitter 121a that attenuates the
light signal LS and outputs the first and second light signals LS1
and LS2 obtained by asymmetrically splitting the attenuated light
signal LSx may be provided.
[0070] FIG. 6 is a detailed diagram illustrating an optical
splitter of FIG. 2. Referring to FIG. 6, an optical splitter 121b
according to a second embodiment is illustrated. The optical
splitter 121b may receive the light signal LS. The optical splitter
121b may split the light signal LS and may output the first and
second light signals LS1 and LS2 obtained by attenuating the split
light signals by different attenuation coefficients to the first
and second amplifiers 122 and 123, respectively.
[0071] The optical splitter 121b may include an optical splitting
unit 121b-2, a first variable optical attenuator 121b-3, and a
second variable optical attenuator 121b-4. The optical splitting
unit 121b-2 may receive the light signal LS. The optical splitting
unit 121b-2 may split the light signal LS into first and second
split light signals LSy1 and LSy2. The optical splitting unit
121b-2 may output the first and second split light signals LSy1 and
LSy2 to the first and second variable optical attenuators 121b-3
and 121b-4, respectively.
[0072] In an embodiment, the optical splitting unit 121b-2 may
symmetrically split the light signal LS. For example, the optical
splitting unit 121b-2 may symmetrically split the light signal LS
to the first and second split light signals LSy1 and LSy2. In this
case, the luminous intensity of the first split light signal LSy1
may be the same as that of the second split light signal LSy2.
[0073] The first variable optical attenuator 121b-3 may receive the
first split light signal LSy1 from the optical splitting unit
121b-2. The first variable optical attenuator 121b-3 may output the
first light signal LS1 obtained by attenuating the first split
light signal LSy1 by the first attenuation coefficient to the first
amplifier 122. In this case, the attenuation coefficient of the
optical attenuator may represent a degree of attenuating the
luminous intensity of the light signal. For example, as the
attenuation coefficient of the optical attenuator increases, the
luminous intensity of the light signal output from the optical
attenuator may be decreased.
[0074] The second variable optical attenuator 121b-4 may receive
the second split light signal LSy2 from the optical splitting unit
121b-2. The second variable optical attenuator 121b-4 may output
the second light signal LS2 obtained by attenuating the second
split light signal LSy2 by a second attenuation coefficient to the
second amplifier 123.
[0075] In an embodiment, the second attenuation coefficient of the
second variable optical attenuator 121b-4 may be less than the
first attenuation coefficient of the first variable optical
attenuator 121b-3. For example, when the first and second split
light signals LSy1 and LSy2 have the same luminous intensity, the
first variable optical attenuator 121b-3 may output first light
signal LS1 obtained by attenuating the first split light signal
LSy1 by the first attenuation coefficient. The second variable
optical attenuator 121b-4 may output the second light signal LS2
obtained by attenuating the second split light signal LSy2 by the
second attenuation coefficient.
[0076] In this case, the luminous intensity of the first light
signal LS1 may be less than the luminous intensity of the second
light signal LS2. In addition, the luminous intensity of the first
light signal LS1 may be included in a luminous intensity range
corresponding to the linear gain section of the first amplifier
122. The luminous intensity of the second light signal LS2 may be
included in a luminous intensity range corresponding to the
saturation gain section of the second amplifier 123.
[0077] As described above, according to the second embodiment of
the present disclosure, the optical splitter 121b that splits the
light signal LS and outputs the first and second light signals LS1
and LS2 obtained by attenuating the first and second split light
signals LSy1 and LSy2 by the first and second attenuation
coefficients, respectively may be provided.
[0078] FIG. 7 is a detailed diagram illustrating a polarization
division hybrid of FIG. 2. Referring to FIG. 7, the polarization
division hybrid 124 is illustrated as an example. The polarization
division hybrid 124 may polarize and separate the amplified second
light signal ALS2 and the reference light signal RLS into the
in-phase component and the quadrature-phase component,
respectively, and may generate the in-phase and quadrature-phase
hybrid light signals HSI and HSQ, based on the polarized and
separated light signals,
[0079] The polarization division hybrid 124 may include a first
polarization separator 124-1, a second polarization separator
124-2, a first optical hybrid 124-3, and a second optical hybrid
124-4.
[0080] The first polarization separator 124-1 may receive the
amplified second light signal ALS2 from the second amplifier 123.
The first polarization separator 124-1 may polarize and separate
the amplified second light signal ALS2 into the in-phase component
and the quadrature-phase component, and may output an in-phase
signal ALS2-I including the polarized and separated in-phase
component and a quadrature-phase signal ALS2-Q including the
polarized and separated quadrature-phase component to the first and
second optical hybrids 124-3 and 124-4, respectively. In detail,
the first polarization separator 124-1 may be a module that
polarizes and separates the light signal.
[0081] The second polarization separator 124-2 may receive the
reference light signal RLS from the reference light signal
generator 110. The second polarization separator 124-2 may polarize
and separate the reference light signal RLS into the in-phase
component and the quadrature-phase component, and may output an
in-phase signal RLS-I including the polarized and separated
in-phase component and a quadrature-phase signal RLS-Q including
the polarized and separated quadrature-phase component to the first
and second optical hybrids 124-3 and 124-4, respectively. The
second polarization separator 124-2 may have a similar structure to
the first polarization separator 124-1.
[0082] The first optical hybrid 124-3 may receive the in-phase
signal ALS2-I from the first polarization separator 124-1. The
first optical hybrid 124-3 may receive the in-phase signal RLS-I
from the second polarization separator 124-2. The first optical
hybrid 124-3 may output the in-phase hybrid light signal HSI to the
optoelectronic conversion unit 125, based on the in-phase signals
ALS2-I and RLS-I. In detail, the first optical hybrid 124-3 may be
a module that combines light signals.
[0083] In an embodiment, the first optical hybrid 124-3 may combine
the in-phase signals ALS2-I and RLS-I under different phase
conditions to generate first to fourth in-phase hybrid light
signals HSI1 to HSI4.
[0084] In more detail, the first optical hybrid 124-3 may split the
in-phase signal ALS2-I into four signals, and may shift phases of
the four split in-phase signals ALS2-I to 0 degrees, 90 degrees,
180 degrees, and 270 degrees, respectively. The first optical
hybrid 124-3 may split the in-phase signal RLS-I into four signals.
The first optical hybrid 124-3 may combine the four in-phase
signals ALS2-I that are shifted by 0 degrees, 90 degrees, 180
degrees, and 270 degrees, respectively with the four split in-phase
signals RLS-I to generate the first to fourth in-phase hybrid light
signals HSI1 to HSI4.
[0085] In detail, when a change in luminous intensity due to split
is ignored, the first in-phase hybrid light signal HSI1 may be a
combination of the in-phase signal ALS2-I and the in-phase signal
RLS-I. The second in-phase hybrid light signal HSI2 may be a
combination of the in-phase signal ALS2-I that is phase-shifted by
90 degrees and the in-phase signal RLS-I. The third in-phase hybrid
light signal HSI3 may be a combination of the in-phase signal
ALS2-I that is phase-shifted by 180 degrees and the in-phase signal
RLS-I. The fourth in-phase hybrid light signal HSI4 may be a
combination of the in-phase signal ALS2-I that is phase-shifted by
270 degrees and the in-phase signal RLS-I. In this case, the first
to fourth in-phase hybrid light signals HSI1 to HSI4 may be
included in the in-phase hybrid light signal HSI.
[0086] The second optical hybrid 124-4 may receive the
quadrature-phase signal ALS2-Q from the first polarization
separator 124-1. The second optical hybrid 124-4 may receive the
quadrature-phase signal RLS-Q from the second polarization
separator 124-2. The second optical hybrid 124-4 may output the
quadrature-phase hybrid light signal HSQ to the optoelectronic
conversion unit 125, based on the quadrature-phase signals ALS2-Q
and RLS-Q. The second optical hybrid 124-4 may have a structure
similar to that of the first optical hybrid 124-3.
[0087] In an embodiment, the second optical hybrid 124-4 may
combine the quadrature-phase signals ALS2-Q and RLS-Q under
different phase conditions to generate first to fourth
quadrature-phase hybrid light signals HSQ1 to HSQ4. The first to
fourth quadrature-phase hybrid light signals HSQ1 to HSQ4 may be
included in the quadrature-phase hybrid light signal HSQ. Since the
process of generating the first to fourth quadrature-phase hybrid
light signals HSQ1 to HSQ4 is similar to the process of generating
the first to fourth in-phase hybrid light signals HSI1 to HSI4
described above, a detailed description thereof will be omitted to
avoid redundancy.
[0088] FIG. 8 is a detailed diagram illustrating an optoelectronic
conversion unit of FIG. 2. Referring to FIG. 8, the optoelectronic
conversion unit 125 is illustrated as an example. The
optoelectronic conversion unit 125 may receive the amplified first
light signal ALS1 from the first amplifier 122. The optoelectronic
conversion unit 125 may receive the in-phase hybrid light signals
HSI1 to HSI4 from the first optical hybrid 124-3 and the
quadrature-phase hybrid light signals HSQ1 to HSQ4 from the second
optical hybrid 124-4. The optoelectronic conversion unit 125 may
output the electrical signal ES obtained by converting the received
signals ALS1, HSI1 to HSI4, and HSQ1 to HSQ4 to the signal
processor 130. The electrical signal ES may include electrical
signals ALS1e, I13e, I24e, Q13e, and Q24e.
[0089] The optoelectronic conversion unit 125 may include a
magnitude optoelectronic converter 125a and first to fourth phase
optoelectronic converters 125b-1 to 125b-4. To more clearly
describe the characteristics of the optoelectronic conversion unit
125, the signal processor 130 is also described together. The
signal processor 130 may include a magnitude demodulator 131, a
phase demodulator 132, and a processor 133.
[0090] The magnitude optoelectronic converter 125a may receive the
amplified first light signal ALS1 from the first amplifier 122. The
magnitude optoelectronic converter 125a may generate the electrical
signal ALS1e obtained by converting the amplified first light
signal ALS1. The magnitude optoelectronic converter 125a may output
the electrical signal ALS1e to the magnitude demodulator 131.
[0091] The first phase optoelectronic converter 125b-1 may receive
the first and third in-phase hybrid light signals HSI1 and HSI3
from the first optical hybrid 124-3. In this case, a phase
difference between the first and third in-phase hybrid light
signals HSI1 and HSI3 may be 180 degrees. The first phase
optoelectronic converter 125b-1 may generate the electrical signal
I13e, based on the difference between the first and third in-phase
hybrid light signals HSI1 and HSI3. The first phase optoelectronic
converter 125b-1 may output the electrical signal I13e to the phase
demodulator 132.
[0092] The second phase optoelectronic converter 125b-2 may receive
the second and fourth in-phase hybrid light signals HSI2 and HSI4
from the first optical hybrid 124-3. In this case, a phase
difference between the second and fourth in-phase hybrid light
signals HSI2 and HSI4 may be 180 degrees. The second phase
optoelectronic converter 125b-2 may generate the electrical signal
I24e, based on the difference between the second and fourth
in-phase hybrid light signals HSI2 and HSI4. The second phase
optoelectronic converter 125b-2 may output the electrical signal
I24e to the phase demodulator 132.
[0093] The third phase optoelectronic converter 125b-3 may receive
the first and third quadrature-phase hybrid light signals HSQ1 and
HSQ3 from the second optical hybrid 124-4. In this case, a phase
difference between the first and third quadrature-phase hybrid
light signals HSQ1 and HSQ3 may be 180 degrees. The third phase
optoelectronic converter 125b-3 may generate the electrical signal
Q13e, based on the difference between the first and third
quadrature-phase hybrid light signals HSQ1 and HSQ3. The third
phase optoelectronic converter 125b-3 may output the electrical
signal Q13e to the phase demodulator 132.
[0094] The fourth phase optoelectronic converter 125b-4 may receive
the second and fourth quadrature-phase hybrid light signals HSQ2
and HSQ4 from the second optical hybrid 124-4. In this case, a
phase difference between the second and fourth quadrature-phase
hybrid light signals HSQ2 and HSQ4 may be 180 degrees. The fourth
phase optoelectronic converter 125b-4 may generate the electrical
signal Q24e, based on the difference between the second and fourth
quadrature-phase hybrid light signals HSQ2 and HSQ4. The fourth
phase optoelectronic converter 125b-4 may output the electrical
signal Q24e to the phase demodulator 132.
[0095] The magnitude demodulator 131 may receive the electrical
signal ALS1e from the magnitude optoelectronic converter 125a. In
this case, the electrical signal ALS1e may be a signal obtained by
converting the amplified first light signal ALS1. The magnitude
demodulator 131 may demodulate the magnitude component, based on
the electrical signal ALS1e. The magnitude demodulator 131 may
output a magnitude demodulation signal MDS including information
corresponding to the demodulated magnitude component to the
processor 133.
[0096] The phase demodulator 132 may receive the electrical signals
I13e, I24e, Q13e, and Q24e from the first to fourth phase
optoelectronic converters 125b-1 to 125b-4. In this case, the
electrical signals I13e and I24e may be signals obtained by
converting the in-phase hybrid light signals HSI1 to HSI4. The
electrical signals Q13e and Q24e may be signals obtained by
converting the quadrature-phase hybrid light signals HSQ1 to HSQ4.
The phase demodulator 132 may demodulate the phase component, based
on the electrical signals I13e, I24e, Q13e, and Q24e. The phase
demodulator 132 may output a phase demodulation signal PDS
including information corresponding to the demodulated phase
component to the processor 133.
[0097] The processor 133 may receive the magnitude demodulation
signal MDS from the magnitude demodulator 131. The processor 133
may receive the phase demodulation signal PDS from the phase
demodulator 132. The processor 133 may demodulate the quadrature
amplitude modulation, based on the magnitude demodulation signal
MDS and the phase demodulation signal PDS. In detail, the processor
133 may restore data included in the modulated light signal based
on quadrature amplitude modulation.
[0098] FIG. 9 is a flowchart describing an operation method of an
optical receiver according to an embodiment of the present
disclosure. Referring to FIG. 9, a method of operating an optical
receiver is described by way of example. In operation S110, the
optical receiver may receive the light signal and the reference
light signal. The light signal may be a modulated signal based on
the quadrature amplitude modulation. The light signal may be a
signal received from the outside (e.g., an optical transmitter).
The reference light signal may be a signal of providing a reference
phase in demodulation of the phase component. The reference light
signal may be a signal received from a separate module (e.g., a
reference light signal generator).
[0099] In operation S120, the optical receiver may generate the
first and second light signals, based on the light signal received
in operation S110. The first light signal may be a signal used for
demodulation of the magnitude component. The second light signal
may be a signal used for demodulation of the phase component.
[0100] In an embodiment, the optical receiver may generate the
first and second light signals by attenuating the light signal
received in operation S110. For example, the luminous intensity of
the first light signal and the luminous intensity of the second
light signal may be less than that of the light signal received in
operation S110.
[0101] In an embodiment, the optical receiver may asymmetrically
generate the first and second light signals. For example, the
optical receiver may generate the second light signal having a
greater luminous intensity than the first light signal. The first
light signal is a signal included in the linear gain section of the
amplifier and may be a signal suitable for demodulation of the
magnitude component. The second light signal is a signal included
in the saturation gain section of the amplifier, and may be a
signal suitable for demodulation of the phase component.
[0102] In an embodiment, the optical receiver may attenuate the
light signal, and then may split the attenuated light signals into
the first and second light signals. For example, the optical
receiver may attenuate the light signal received in operation S110.
Thereafter, the optical receiver may asymmetrically split the
attenuated light signal into the first and second light signals. In
this case, the luminous intensity of the second light signal may be
greater than that of the first light signal.
[0103] In an embodiment, the optical receiver may split the light
signal, and then may generate the first and second light signals by
attenuating the split light signals. For example, the optical
receiver may split the light signal received in operation S110 into
the first and second split light signals. In this case, the
luminous intensity of the first split light signal may be the same
as that of the second split light signal.
[0104] Thereafter, the optical receiver may generate the first
light signal obtained by attenuating the first split light signal
by the first attenuation coefficient. The optical receiver may
generate the second light signal obtained by attenuating the second
split light signal by the second attenuation coefficient less than
the first attenuation coefficient. In this case, the process of
attenuating the first split light signal and the process of
attenuating the second split light signal may be performed in
parallel, or the process of attenuating the first split light
signal may be performed earlier than the process of attenuating the
second split light signal. Alternatively, the process of
attenuating the first split light signal may be performed later
than the process of attenuating the second split light signal.
[0105] In operation S130, the optical receiver may amplify the
first and second light signals generated in operation S120. In an
embodiment, the optical receiver may amplify the first light signal
in the linear gain section and may amplify the second light signal
in the saturation gain section.
[0106] In an embodiment, in operation S130, the optical receiver
may amplify the first light signal such that a difference in
luminous intensity of the first light signal increases. Also, the
optical receiver may amplify the second light signal such that a
difference in luminous intensity of the second light signal
decreases. In detail, the optical receiver may preprocess the first
light signal suitable for demodulation of the magnitude component,
and may preprocess the second light signal suitable for
demodulation of the phase component.
[0107] In operation S140, the optical receiver may polarize and
separate the reference light signal in operation S110 and the
amplified second light signal in operation S130, and may generate
the in-phase hybrid light signal and the quadrature-phase hybrid
light signal, based on the polarized and separated light signals.
The in-phase hybrid light signal may include a signal in which
signals of in-phase component are combined among the polarized and
separated light signals. The quadrature-phase hybrid light signal
may include a signal in which signals of quadrature-phase component
are combined among the polarized and separated light signals.
[0108] In operation S150, the optical receiver may process the
amplified first light signal in operation S130, the in-phase hybrid
light signal in operation S140, and the quadrature-phase hybrid
light signal in operation S140.
[0109] In an embodiment, the optical receiver may convert the
amplified first light signal into the electrical signal, and then
may output the converted signal to the magnitude demodulator. In
this case, the magnitude demodulator may be a module that
demodulates the magnitude component in the quadrature amplitude
modulation.
[0110] In an embodiment, the optical receiver may convert the
in-phase and quadrature-phase hybrid light signals, respectively,
and then may output the converted signals to the phase demodulator.
In this case, the phase demodulator may be a module that
demodulates the phase component in the quadrature amplitude
modulation.
[0111] As described above, according to an embodiment of the
present disclosure, an operation method of the optical receiver may
be provided that separates and processes the first light signal
used for demodulation of the magnitude component and the second
light signal used for demodulation of the phase component in the
quadrature amplitude modulation.
[0112] According to an embodiment of the present disclosure, an
optical receiver in which a magnitude modulation and a phase
modulation are separated in the quadrature amplitude modulation,
and an operation method thereof are provided.
[0113] In addition, through preprocessing of optically separating a
magnitude modulation and a phase modulation, an optical receiver in
which a reception sensitivity of the magnitude modulation is
improved and a change in luminous intensity in the phase modulation
is suppressed, and an operation method thereof are provided.
[0114] While the present disclosure has been described with
reference to embodiments thereof, it will be apparent to those of
ordinary skill in the art that various changes and modifications
may be made thereto without departing from the spirit and scope of
the present disclosure as set forth in the following claims.
* * * * *