Fault recovery in branched optical networks
View Patent ↗A system and method for fault recovery in a branched optical network. In response to a fault, power distribution in channels on recovering digital line segments is adjusted to minimize a merit function based on one or more system parameters.
1. A wavelength division multiplexed optical system comprising:
a first trunk terminal configured to provide a trunk input signal on a trunk path, said trunk input signal occupying a plurality of express channels and a plurality of drop channels;
a branch terminal configured to provide a branch input signal on a branch path, said branch input signal occupying a plurality of add channel channels;
an optical add-drop multiplexer (OADM) coupled to said trunk path and said branch path for receiving said trunk input signal and said branch input signal and providing a trunk output signal on said trunk path and a branch output signal on said branch path, said trunk output signal comprising said express channels and said add channels, said branch input signal comprising said drop channels; and
a second trunk terminal coupled to said OADM and configured to receive said trunk output signal;
at least one of said first trunk terminal and said branch terminal being configured to adjust an output power of said trunk input signal or said branch input signal, respectively, to minimize a merit function to recover from a fault on said trunk path or said branch path,
wherein said at least one of said first trunk terminal and said branch terminal is configured to adjust first and second power ratios in said trunk input signal or said branch input signal, respectively, to minimize said merit function,
wherein said first power ratio is expressed as:
r
1
=
∑
P
sig
P
launch
=
∑
P
sig
∑
P
sig
+
∑
P
IB
+
∑
P
OB
and wherein said second power ratio is expressed as:
r
2
=
∑
P
IB
∑
P
IB
+
∑
P
OB
where P sig , P IB , P OB and P launch are utilized channel power, in-band loading signal power, out-of-band loading signal power, and total launched power, respectively, of the trunk input signal or said branch input signal.
2. A system according to claim 1 , wherein said merit function is expressed as:
ɛ
=
∑
sig
(
OSNR
-
OSNR
0
OSNR
0
)
2
+
w
∑
sig
(
NL
-
NL
0
NL
0
)
2
1
+
w
where OSNR is a received optical signal-to-noise ratio, OSNR 0 is a nominal received optical signal-to-noise ratio, NL is a total accumulated non-linear phase shift, NL 0 is a nominal total accumulated non-linear phase shift, and w is a weighting factor.
3. A system according to claim 1 , wherein said first trunk terminal or said branch terminal is configured to change utilized channels of said trunk input signal or said branch input signal, respectively, to unutilized channels with in-band loading signals thereon.
4. A system according to claim 1 , wherein said first trunk terminal or said branch terminal is further configured to separately adjust individual channel powers in said trunk input signal or said branch input signal, respectively.
5. A system according to claim 1 , wherein said merit function is based on optical signal-to-noise ratio and non-linear phase shift.
6. A system according to claim 1 , wherein said merit function is expressed as:
ɛ
=
∑
sig
(
OSNR
-
OSNR
0
OSNR
0
)
2
+
w
∑
sig
(
NL
-
NL
0
NL
0
)
2
1
+
w
where OSNR is a received optical signal-to-noise ratio, OSNR 0 is a nominal received optical signal-to-noise ratio, NL is a total accumulated non-linear phase shift, NL 0 is a nominal total accumulated non-linear phase shift, and w is a weighting factor.
7. A method for fault recovery in a branched WDM optical network comprising: adjusting power distribution of transmitted channels to minimize a merit function in response to a fault; separately adjusting power in individual transmitted channels to minimize the merit function, said adjusting comprising adjusting first and second power ratios in said transmitted channels,
wherein said first power ratio is expressed as:
r
1
=
Σ
P
sig
Plaunch
=
Σ
Psig
Σ
Psig
+
Σ
IB
+
Σ
POB
and wherein said second power ratio is expressed as:
r
2
=
Σ
PIB
Σ
IB
+
Σ
POB
where P sig , P IB , P OB and P launch are utilized channel power, in-band loading signal power, out-of-band loading signal power, and total launched power, respectively, of said transmitted channels.
8. A method according to claim 7 , wherein said merit function is expressed as:
ɛ
=
∑
sig
(
OSNR
-
OSNR
0
OSNR
0
)
2
+
w
∑
sig
(
NL
-
NL
0
NL
0
)
2
1
+
w
where OSNR is a received optical signal-to-noise ratio, OSNR 0 is a nominal received optical signal-to-noise ratio, NL is a total accumulated non-linear phase shift, NL 0 is a nominal total accumulated non-linear phase shift, and w is a weighting factor.
9. A method according to claim 7 , said method further comprising changing utilized ones of said transmitted channels to unutilized channels with in-band loading signals thereon.
10. A method according to claim 7 , wherein said merit function is based on optical signal-to-noise ratio and non-linear phase shift.
11. A method according to claim 7 , wherein said merit function is expressed as:
ɛ
=
∑
sig
(
OSNR
-
OSNR
0
OSNR
0
)
2
+
w
∑
sig
(
NL
-
NL
0
NL
0
)
2
1
+
w
where OSNR is a received optical signal-to-noise ratio, OSNR 0 is a nominal received optical signal-to-noise ratio, NL is a total accumulated non-linear phase shift, NL 0 is a nominal total accumulated non-linear phase shift, and w is a weighting factor.
12. A wavelength division multiplexed optical system comprising:
a first trunk terminal configured to provide a trunk input signal on a trunk path, said trunk input signal occupying a plurality of express channels and a plurality of drop channels;
a branch terminal configured to provide a branch input signal on a branch path, said branch input signal occupying a plurality of add channel channels;
an optical add-drop multiplexer (OADM) coupled to said trunk path and said branch path for receiving said trunk input signal and said branch input signal and providing a trunk output signal on said trunk path and a branch output signal on said branch path, said trunk output signal comprising said express channels and said add channels, said branch input signal comprising said drop channels; and
a second trunk terminal coupled to said OADM and configured to receive said trunk output signal;
at least one of said first trunk terminal and said branch terminal being configured to adjust an output power of said trunk input signal or said branch input signal, respectively, to minimize a merit function to recover from a fault on said trunk path or said branch path,
wherein said merit function is expressed as:
ɛ
=
∑
sig
(
OSNR
-
OSNR
0
OSNR
0
)
2
+
w
∑
sig
(
NL
-
NL
0
NL
0
)
2
1
+
w
where OSNR is a received optical signal-to-noise ratio, OSNR 0 is a nominal received optical signal-to-noise ratio, NL is a total accumulated non-linear phase shift, NL 0 is a nominal total accumulated non-linear phase shift, and w is a weighting factor.
13. A method for fault recovery in a branched WDM optical network comprising: adjusting power distribution of transmitted channels to minimize a merit function in response to a fault; separately adjusting power in individual transmitted channels to minimize the merit function, wherein said merit function is expressed as:
ɛ
=
∑
sig
(
OSNR
-
OSNRo
OSNRo
)
2
+
w
∑
sig
(
NL
-
NLo
NLo
)
2
1
+
w
where OSNR is a received optical signal-to-noise ratio, OSNRo is a nominal received optical signal-to-noise ratio, NL is a total accumulated non-linear phase shift, NLo is a nominal total accumulated non-linear phase shift, and w is a weighting factor.