In-band noise determination on optical communication signals
View Patent ↗There are provided methods and devices for determining a quality parameter characterizing an optical communication signal, the methods being performed by signal detection devices. At the transmitting end, there are obtained a signal power P 1 of a first optical signal, a signal power P 2 of a second optical signal, a signal power P 3 of a third optical signal, optionally a signal power P 4 of a fourth optical signal, and a total signal power Ps of a channel where the first, second, third and optional fourth optical signals are located. At a detection point, there are further obtained a signal power P 1 ′ of the first optical signal, a signal power P 2 ′ of the second optical signal, a signal power P 3 ′ of the third optical signal and optionally a signal power P 4 ′ of the fourth optical signal. There are then determined a signal deformation factor SDF and/or an optical signal to ASE noise ratio OSNR from the obtained signal powers.
1. A method for determining a quality parameter characterizing an optical communication signal, the method performed by a signal detection device and comprising:
obtaining a signal power P 1 of a first optical signal at a transmitter end, a signal power P 2 of a second optical signal at a transmitter end, a signal power P 3 of a third optical signal at a transmitter end, and a total signal power Ps of a channel where the first optical signal, the second optical signal and the third optical signal are located, wherein the first optical signal is at a central wavelength of an optical channel bandwidth of said optical communication signal, and the second optical signal and the third optical signal are located on the same side relative to the center of the optical channel bandwidth;
obtaining a ratio K 1 of the signal power P 1 to the total signal power Ps and a ratio K 2 of the signal power P 2 to the signal power P 1 and a ratio K 3 of the signal power P 3 to the signal power P 1 according to P 1 , P 2 , P 3 and Ps;
obtaining a signal power P 1 ′ of the first optical signal at a detection point, a signal power P 2 ′ of the second optical signal at the detection point and a signal power P 3 ′ of the third optical signal at the detection point;
obtaining a ratio K 2 ′ of the signal power P 2 ′ to the signal power P 1 ′ and a ratio K 3 ′ of the signal power P 3 ′ to the signal power P 1 ′ according to P 1 ′, P 2 ′ and P 3 ′;
determining an extended signal to noise ratio eOSNR 2 according to the recorded ratios K 1 , K 2 and K 2 ′ and an extended signal to noise ratio eOSNR 3 according to the recorded ratios K 1 , K 3 and K 3 ′; and
determining a signal deformation factor SDF from the extended signal to noise ratios eOSNR 2 and eOSNR 3 .
2. The method as claimed in claim 1 , further comprising:
determining an Optical Signal to ASE Noise Ratio OSNR from the determined extended signal to noise Ratios eOSNR 2 and eOSNR 3 and a predetermined relationship between the signal deformation factor SDF and the signal deformation SD.
3. The method as claimed in claim 1 , wherein the first optical signal, the second optical signal and the third optical signal are different in central wavelength and are same in bandwidth.
4. The method as claimed in claim 1 , wherein the step of obtaining a ratio K 1 of the signal power P 1 to the total signal power Ps, a ratio K 2 of the signal power P 2 to the signal power P 1 and a ratio K 3 of the signal power P 3 to the signal power P 1 according to P 1 , P 2 , P 3 and Ps further comprises:
recording the ratio K 1 , the ratio K 2 and the ratio K 3 on site or on a Network Management Information.
5. A method for determining a quality parameter characterizing an optical communication signal, the method performed by a signal detection device and comprising:
obtaining a signal power P 1 of a first optical signal at a transmitter end, a signal power P 2 of a second optical signal at the transmitter end, a signal power P 3 of a third optical signal at the transmitter end, a signal power P 4 of a fourth optical signal at the transmitter end and a total signal power Ps of a channel where the first optical signal, the second optical signal, the third optical signal and the fourth optical signal are located, wherein the first optical signal is at a central wavelength of an optical channel bandwidth of said optical communication signal, and the second optical signal and the third optical signal are located on the same side relative to the center of the optical channel bandwidth;
obtaining a signal power P 1 ′ of the first optical signal at a detection point, a signal power P 2 ′ of the second optical signal at the detection point, a signal power P 3 ′ of the third optical signal at the detection point and a signal power P 4 ′ of the fourth optical signal at the detection point;
obtaining and recording a ratio K 1 of the signal power P 1 to the total signal power Ps, a ratio K 2 of the signal power P 2 to the signal power P 1 , a ratio K 3 of the signal power P 3 to the signal power P 1 and a ratio K 4 of the signal power P 4 to the signal power P 1 according to P 1 , P 2 , P 3 and P 4 ;
obtaining and recording a ratio K 2 ′ of the signal power P 2 ′ to the signal power P 1 ′, a ratio K 3 ′ of the signal power P 3 ′ to the signal power P 1 ′ and a ratio K 4 ′ of the signal power P 4 ′ to the signal power P 1 ′ according to P 1 ′, P 2 ′, P 3 ′ and P 4 ′; and
determining an Optical Signal to ASE Noise Ratio (OSNR),
the OSNR being given by a formula equivalent to the following formula:
OSNR
=
C
·
1
K
4
-
2
K
3
+
K
2
K
4
′
-
2
K
3
′
+
K
2
′
-
1
.
6. The method as claimed in claim 5 ,
wherein the second optical signal, the third optical signal and the fourth optical signal are obtained using respective optical filters having equidistant central wavelengths and having substantially equal optical bandwidth; and
wherein the step of determining an Optical Signal to ASE Noise Ratio employs a formula at least equivalent to the following formula:
OSNR
=
B
CW
1
K
1
·
B
r
·
K
4
′
-
2
K
3
′
+
K
2
′
K
4
-
2
K
3
+
K
2
-
(
K
4
′
-
2
K
3
′
+
K
2
′
)
,
wherein BCW 1 is an optical bandwidth of an optical filter CW 1 from which the first optical signal is outputted, and where the Br is a reference bandwidth of noise power.
7. The method as claimed in claim 5 , further comprising:
determining an extended signal to noise ratio eOSNR 2 according to the ratios K 1 , K 2 and K 2 ′, an extended signal to noise ratio eOSNR 3 according to the ratios K 1 , K 3 and K 3 ′ and an extended signal to noise ratio eOSNR 4 according to the ratios K 1 , K 4 and K 4 ′;
determining a signal deformation from the extended signal to noise ratios eOSNR 2 , eOSNR 3 and eOSNR 4 , wherein the signal deformation is obtained using a formula at least equivalent to the following formula:
SD
=
e
OSNR
2
-
1
+
eOSNR
3
-
1
+
eOSNR
4
-
1
3
-
OSNR
-
1
.