Inverse channel apparatus and transmitter, receiver and system containing the apparatus
View Patent ↗The embodiments provide an inverse channel apparatus and transmitter, receiver and system containing the apparatus; wherein the inverse channel apparatus comprises: an inverse nonlinear calculating unit configured to perform nonlinear additive calculation and nonlinear multiplicative calculation on input signals, so as to obtain signals containing nonlinear damage of the input signals on at least one polarization state; and an inverse linear calculating unit configured to calculate signals containing nonlinear damage and linear damage of the input signals on at least one polarization state according to the signals containing nonlinear damage of the input signals on at least one polarization state and a linear function of a channel. The advantages of the embodiments exist in that a transmitted signal is recovered by being passed through an inverse channel after or before being transmitted in a practical channel, thereby effectively compensating for intra-channel nonlinear damage of an optical fiber communication system.
1. An inverse channel apparatus, comprising an inverse nonlinear calculating unit and an inverse linear calculating unit, wherein,
the inverse nonlinear calculating unit is configured to perform nonlinear additive calculation and nonlinear multiplicative calculation on input signals, so as to obtain signals containing nonlinear damage of the input signals on at least one polarization state;
the inverse nonlinear calculating unit comprising:
an inverse nonlinear coefficient calculating module configured to calculate nonlinear coefficients of the inverse channel according to channel configuration parameters;
an inverse nonlinear perturbation calculating module configured to calculate nonlinear perturbation within the inverse channel according to the nonlinear coefficients of the inverse channel and the input signals; and
an inverse nonlinear adding and multiplying module configured to calculate signals containing nonlinear damage of the input signals on at least one polarization state according to the nonlinear perturbation within the inverse channel and the input signals;
and the inverse linear calculating unit is configured to calculate signals containing nonlinear damage and linear damage of the input signals on at least one polarization state according to the signals containing nonlinear damage of the input signals on at least one polarization state and a linear function of a channel.
2. The apparatus according to claim 1 , wherein the channel configuration parameters comprise optical fiber parameters, the optical fiber parameters comprising an attenuation factor α and/or a dispersion factor β and/or a nonlinear factor γ;
and wherein the inverse nonlinear coefficient calculating module calculates the nonlinear coefficients of the inverse channel according to inverted values of the optical fiber parameters.
3. The apparatus according to claim 1 , wherein the inverse nonlinear perturbation calculating module is configured to calculate nonlinear perturbation within the inverse channel caused by intra-channel four-wave mixing (IFWM), intra-channel cross phase modulation (IXPM) and self-phase modulation (SPM);
and wherein,
the nonlinear perturbation caused by IFWM is:
Δ
h
,
IFWM
,
l
=
j
∑
m
≠
0
∑
n
≠
0
c
(
m
,
n
)
(
H
l
+
m
H
l
+
n
H
l
+
m
+
n
*
+
H
l
+
m
V
l
+
n
V
l
+
m
+
n
*
)
,
Δ
h
,
IFWM
,
l
=
j
∑
m
≠
0
∑
n
≠
0
c
(
m
,
n
)
(
H
l
+
m
H
l
+
n
H
l
+
m
+
n
*
+
H
l
+
m
V
l
+
n
V
l
+
m
+
n
*
)
;
the nonlinear perturbation caused by IXPM is:
ϕ
h
,
IXPM
,
l
=
∑
m
≠
0
c
(
m
,
0
)
(
2
H
l
+
m
2
+
V
l
+
m
2
)
,
ϕ
v
,
IXPM
,
l
=
∑
m
≠
0
c
(
m
,
0
)
(
2
V
l
+
m
2
+
H
l
+
m
2
)
,
w
hv
,
IXPM
,
l
=
j
∑
m
≠
0
c
(
m
,
0
)
H
l
+
m
V
l
+
m
*
,
w
vh
,
IXPM
,
l
=
j
∑
m
≠
0
c
(
m
,
0
)
V
l
+
m
H
l
+
m
*
;
and the nonlinear perturbation caused by SPM is:
φ h,SPM,l =φ v,SPM,l =c (0,0)(| H l | 2 +|V l | 2 );
where, c is a nonlinear coefficient of the inverse channel, m and n are relative moments, l is an absolute moment, H is an input signal on the horizontal polarization state, and V is an input signal on the vertical polarization state.
4. The apparatus according to claim 1 , wherein the inverse nonlinear adding and multiplying module calculates the signals containing nonlinear damage of the input signals on at least one polarization state according to the following formula:
[
H
NL
V
NL
]
=
[
ⅇ
j
(
ϕ
h
,
IXPM
+
ϕ
h
,
SPM
)
w
hv
,
IXPM
w
vh
,
IXPM
ⅇ
j
(
ϕ
v
,
IXPM
+
ϕ
v
,
SPM
)
]
[
H
+
Δ
h
,
IFWM
V
+
Δ
v
,
IFWM
]
,
or
[
H
NL
V
NL
]
=
[
1
-
w
vh
,
IXPM
2
ⅇ
j
(
ϕ
h
,
IXPM
+
ϕ
h
,
SPM
)
w
hv
,
IXPM
w
vh
,
IXPM
1
-
w
hv
,
IXPM
2
ⅇ
j
(
ϕ
v
,
IXPM
+
ϕ
v
,
SPM
)
]
[
H
+
Δ
h
,
IFWM
V
+
Δ
v
,
IFWM
]
,
or
[
H
NL
V
NL
]
=
ⅇ
jϕ
c
[
1
-
w
vh
,
IXPM
2
ⅇ
jϕ
Δ
w
hv
,
IXPM
w
vh
,
IXPM
1
-
w
hv
,
IXPM
2
ⅇ
-
jϕ
Δ
]
[
H
+
Δ
h
,
IFWM
V
+
Δ
v
,
IFWM
]
;
where, Δ h,IFWM and Δ v,IFWM are the nonlinear perturbation caused by IFWM, φ h,IXPM , φ v,IXPM , w hv,IXPM and w vh,IXPM are the nonlinear perturbation caused by IXPM, φ h,SPM and φ v,SPM are the nonlinear perturbation caused by SPM,
ϕ
c
=
ϕ
h
,
IXPM
+
ϕ
v
,
IXPM
2
+
ϕ
h
,
SPM
,
ϕ
Δ
=
ϕ
h
,
IXPM
-
ϕ
v
,
IXPM
2
,
H is an input signal on the horizontal polarization state, and V is an input signal on the vertical polarization state.
5. The apparatus according to claim 1 , wherein
the inverse linear calculating unit is an inverse dispersion unit which calculates signals containing nonlinear damage and linear damage of the input signals on at least one polarization state according to the signals containing nonlinear damage of the input signals on at least one polarization state and a dispersion transfer function of the channel;
and wherein the inverse dispersion unit calculates signals containing nonlinear damage and linear damage of the input signals on at least one polarization state according to the following formula:
H IC =H NL h CD −1 ;
V IC =V NL h CD −1 .
6. A receiver, comprising one or a plurality of inverse channel apparatuses as claimed in claim 1 , wherein
when the receiver comprises one inverse channel apparatuses, the inverse channel apparatus is provided between an analog-to-digital converter and an adaptive equalization and polarization demultiplexer of the receiver, the inverse channel apparatus being configured to build an inverse channel of an original channel;
and when the receiver comprises a plurality of inverse channel apparatuses, the inverse channel apparatuses are provided between the analog-to-digital converter and the adaptive equalization and polarization multiplexer of the receiver, each of the inverse channel apparatuses being configured to build inverse channels of a part of original channels.
7. A transmitter, comprising one or a plurality of inverse channel apparatuses as claimed in claim 1 , wherein
when the transmitter comprises one inverse channel apparatus, the inverse channel apparatus is provided before an digital-to-analog converter of the transmitter, the inverse channel apparatus being configured to build an inverse channel of an original channel;
and when the transmitter comprises a plurality of inverse channel apparatuses, the inverse channel apparatuses are provided before the digital-to-analog converter of the transmitter, each of the inverse channel apparatuses being configured to build inverse channels of a part of original channels.
8. A transmission system, comprising a transmitter and a receiver, the transmitter or receiver comprising one or a plurality of the inverse channel apparatuses as claimed in claim 1 .
9. A nonlinear compensation method, comprising performing inverse nonlinear calculation and performing inverse linear calculation, wherein,
the performing inverse nonlinear calculation is to performing nonlinear additive damage calculation and nonlinear multiplicative damage calculation on input signals, so as to obtain signals containing nonlinear damage of the input signals on at least one polarization state;
the performing inverse nonlinear calculation comprising:
calculating nonlinear coefficients of the inverse channel according to channel configuration parameters;
calculating nonlinear perturbation within the inverse channel according to the nonlinear coefficients of the inverse channel and the input signals; and
calculating signals containing nonlinear damage of the input signals on at least one polarization state according to the nonlinear perturbation within the inverse channel and the input signals;
and the performing inverse linear calculation is to calculate signals containing nonlinear damage and linear damage of the input signals on at least one polarization state according to the signals containing nonlinear damage of the input signals on at least one polarization state and a linear function of a channel.