OPTICAL SIGNAL-TO-NOISE RATIO MEASURING METHOD

• US 20160056891A1
• Filed: 09/30/2013
• Published: 02/25/2016
• Est. Priority Date: 03/26/2013
• Status: Abandoned Application

• Current Assignee: Accelink Technologies Company Limited
• Original Assignee: Accelink Technologies Company Limited
• Inventors: Sun, Liping, Hu, Qianggao, Chen, Yan, Xie, Hui, Chen, Shuang, Yue, Qingyan, Liang, Fei, Zhang, Yin, Wu, Hehui
• Application Number:
  US14/780,378
• Publication Number:
  US 20160056891A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04B 10/07953 Monitoring or measuring OSNR, BER or Q
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
• CPC Class Codes: H04J 14/06 Polarisation multiplex systems

Abstract

An OSNR measuring method, comprising: measuring a spectrum to be measured of an optical signal at a point to be measured of an optical transmission line, and acquiring the comparative spectrum of the optical signal within a channel wavelength range and at an SNR different from the SNR of the point to be measured; respectively integrating, within the channel wavelength range of the optical signal, the spectrum to be measured and the comparative spectrum to obtain total power Pspectrum to be measured and Pcomparative spectrum, and acquiring a noise factor F and a signal scale factor A; calculating, according to the total power, the noise factor and the signal scale factor, the noise power Pspectrum to be measured within the channel wavelength range of the optical signal, so as to obtain an OSNR of the point to be measured.

Claims

1. An optical signal-to-noise ration measuring method, comprising the following steps:

measuring spectrum to be measured of measured optical signal at spot to be measured on optical transmission line, wherein the spectrum to be measured includes spectrum power density distribution of the measured optical signal in the channel wavelength range B;

obtaining spectrum to be compared, which includes spectrum power density distribution of the measured optical signal or signal with same spectrum feature as that of the measured optical signal, under SNR different from that of the spot to be measured in the channel wavelength range B;

in the channel wavelength range B, integrating the spectrum to be measured and the spectrum to be compared, respectively, to obtain total powers of the spectrum to be measured and the spectrum to be compared; and

according to integral power relationship and OSNR relationship between optical signal parts of the spectrum to be measured and the spectrum to be compared, using the obtained total powers of the spectrum to be measured and the spectrum to be compared to estimate the OSNR at the spot to be measured.

2. An in-band OSNR measuring method for measuring OSNR at the spot to be measured on the optical transmission line, including following steps:

step 1, measuring spectrum to be measured of measured optical signal at spot to be measured, wherein the spectrum to be measured includes spectrum power density distribution of the measured optical signal in the channel wavelength range B;

step 2, obtaining spectrum to be compared, which includes spectrum power density distribution of the measured optical signal or signal with same spectrum feature as that of the measured optical signal, under SNR different from that of the spot to be measured in the channel wavelength range B;

step 3, in the channel wavelength range B, integrating the spectrum to be measured and the spectrum to be compared respectively, to obtain the total powers of the spectrum to be measured and the spectrum to be compared respectively, wherein the total power P_{spectrum to be measured} of the spectrum to be measured includes integral power S _{spectrum to be measured} of optical signal and the integral power N_{spectrum to be measured} of noise signal, in the spectrum to be measured, and the total power P_{spectrum to be compared} of the spectrum to be compared includes the integral power S_{spectrum to be compared} of optical signal and the integral power N_{spectrum to be compared} of noise signal, in the spectrum to be compared;

Step 4, acquiring noise figure F and signal scale factor A, wherein the noise figure F is defined as;

3. The in-band OSNR measuring method in claim 2, wherein in the step 5, by using noise calculating equation as follows:

4. The in-band OSNR measuring method in claim 3, wherein in the step 5, by using the following equation:

5. The in-band OSNR measuring method in claim 3, wherein,

if the OSNR of the spectrum to be compared in the channel wavelength range B is known, the noise index F is expressed as:

6. The in-band OSNR measuring method in claim 3, wherein,

if the OSNR of the spectrum to be compared in the channel wavelength range B is unknown, and OSNR of the spectrum to be compared is greatly larger than OSNR of the spectrum to be measured, the following equation is used:

7. The in-band OSNR measuring method in claim 3, wherein,

if the OSNR of the spectrum to be compared in the channel wavelength range B is unknown, and OSNR of the spectrum to be compared is greatly smaller than OSNR of the spectrum to be measured, the following steps are used to get the noise index F:

in the channel wavelength range, by getting first integral bandwidth BW1 at the signal peak wavelength, integral powers

8. The in-band OSNR measuring method in claim 7, wherein steps for getting the estimated value N_BW1^{spectrum to be compared} of integral power of noise signal of the spectrum to be compared in the first integral bandwidth BW1 comprises:

by getting third integral bandwidth BW3 in the area where signal takes relatively larger proportion of the spectrum to be compared relative to noise, and initially assuming the noise powers of the spectrum to be measured and the spectrum to be compared within the third integral bandwidth BW3 to be both 0, the equation to calculate scale factor A being simplified as follows;

9. The in-band OSNR measuring method in claim 8, wherein,

the first integral bandwidth BW1 is selected as range of 20 pm of signal peak wavelength,

the second integral bandwidth BW2 is selected as range of 20 pm of signal peak wavelength shifting 60 pm to shortwave,

the third integral bandwidth BW3 is selected as range of 20 pm of signal peak wavelength,

the fourth integral bandwidth BW4 is selected as range of 20 pm of signal peak wavelength shifting 60 pm to longwave or shortwave.

10. The in-band OSNR measuring method of claim 2, wherein before getting the spectrum to be measured and the spectrum to be compared, no signal modulation including polarization modulation is conducted on the measured optical signal.

13. The in-band OSNR measuring method in claim 4, wherein,

if the OSNR of the spectrum to be compared in the channel wavelength range B is known, the noise index F is expressed as:

14. The in-band OSNR measuring method in claim 4, wherein,

if the OSNR of the spectrum to be compared in the channel wavelength range B is unknown, and OSNR of the spectrum to be compared is greatly larger than OSNR of the spectrum to be measured, the following equation is used:

15. The in-band OSNR measuring method in claim 4, wherein,

if the OSNR of the spectrum to be compared in the channel wavelength range B is unknown, and OSNR of the spectrum to be compared is greatly smaller than OSNR of the spectrum to be measured, the following steps are used to get the noise index F:

in the channel wavelength range, by getting first integral bandwidth BW1 at the signal peak wavelength, integral powers P_BW1^{spectrum to be measured} and P_BW1^{specrum to be compared} of the spectrum to be measured and the spectrum to be compared at the first integral bandwidth BW1 are calculated respectively, by getting second integral bandwidth BW2 at spot shifting a certain distance towards shortwave from signal peak value, integral powers

16. The in-band OSNR measuring method in claim 15, wherein steps for getting the estimated value N_BW1^{spectrum to be compared} of integral power of noise signal of the spectrum to be compared in the first integral bandwidth BW1 comprises:

by getting third integral bandwidth BW3 in the area where signal takes relatively larger proportion of the spectrum to be compared relative to noise, and initially assuming the noise powers of the spectrum to be measured and the spectrum to be compared within the third integral bandwidth BW3 to be both 0, the equation to calculate scale factor A being simplified as follows;

17. The in-band OSNR measuring method in claim 16, wherein,

the first integral bandwidth BW1 is selected as range of 20 pm of signal peak wavelength,

the second integral bandwidth BW2 is selected as range of 20 pm of signal peak wavelength shifting 60 pm to shortwave,

the third integral bandwidth BW3 is selected as range of 20 pm of signal peak wavelength,

the fourth integral bandwidth BW4 is selected as range of 20 pm of signal peak wavelength shifting 60 pm to longwave or shortwave.

11. An in-band OSNR measuring device, comprising an input end, an optical amplifying module, a spectrum measuring module, and a control and computing module, wherein,

the optical amplifying module comprises an optical splitter and an optical amplifier;

the spectrum measuring module comprises a optical switch, and a spectrum scanner;

the input end input measured optical signal into the optical splitter, which splits the inputted measured optical signal into two branches, one of which is directly outputted to the optical switch in the spectrum measuring module, and the other is outputted into the optical switch in the spectrum measuring module via the optical amplifier,

under control of the control and computing module, the optical switch selects one branch of optical signal from the inputted two branches of optical signal, and output it to the spectrum scanner,

under control of the control and computing modules, the spectrum scanner scans and measures the inputted optical signal.

12. The in-band OSNR measuring device in claim 11, wherein, the control and computing module control the spectrum measuring module to scan and measure the inputted optical signal, implement the in-band OSNR measuring method of claim 2 on inputted optical signal, in order to get the OSNR of the measured optical signal.