Hello,
Today I'm going to share with you when the dispersion configuration affects system performance.
Problem Description:
An 80-wavelength system for a network wavelength division 1600G device, designed to meet the 10G transmission requirements with OSNR, some wavelengths in the current network operation have excessive error codes before error correction alarm BEFFEC_EXC, and from the MCA scan results of the spectrum analysis unit, some wavelengths have low signal to noise ratio Case.
Network Diagram
Analyze the reasons:
G.655 optical fiber transmission, because the inherent dispersion of optical fiber is near 0ps, it is more susceptible to nonlinearity during long-distance transmission. An obvious manifestation of the nonlinear effect is that the spectrum is broadened, causing the noise floor to be higher than the true value, and the OSNR obtained by scanning is lower.
Dispersion and non-linearity influence each other. The dispersion topology from station A to station B is relatively better, which is more conducive to reducing the spectral broadening caused by non-linearity, and the tested OSNR is closer to the true value. However, the dispersion topology from station B to station A is relatively poor, and the ability to suppress nonlinearity is slightly weaker, resulting in a broadening of the spectrum, and the tested OSNR is slightly lower than the true value.
By optimizing the dispersion topology from station B to station A in the network, the impact of nonlinear effects on the system can be reduced more effectively, and the tested OSNR is significantly improved (closer to the true value) than the original situation.
Fault location and handling process:
1- Determine from the data collected on the live network that the line power commissioning meets the requirements.
2- MCA shows that the flatness of each wave is within a reasonable range.
3- Calculate the residual dispersion of the network through the design document and confirm that the value is within the range of the 10G OTU single board specifications.
4- Optimize the dispersion topology of the line from station B to station A to effectively reduce the impact of nonlinear effects on the system. The tested OSNR has been significantly improved compared to the original situation, and the problem has been solved.
Summary and recommendations:
Fibers with low dispersion coefficients (LEAF or G.653) are more likely to cause strong nonlinear effects in the line than high dispersion coefficients (SMF). In order to improve the system receiving end performance, it can be considered from the aspect of dispersion topology optimization.
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