Hello, I'm glad to introduce you the optical power flatness of the WDM system.
What Is Optical Power Flatness?
Optical power flatness is the difference between the optical power of each wavelength and the average optical power of all wavelengths on an OA.Use the multi-channel spectrum analyzer unit (MCA) to scan the optical power of all single wavelengths on an optical multiplex section (OMS), calculate the average optical power of all wavelengths that pass through the OA, and then calculate the difference between the single-wavelength optical power and the average optical power. Take an absolute value for each difference, among which the maximum value is the optical power flatness.
Optical power flatness = Max. (|Normalized actual single-wavelength optical power of each channel — Average optical power|)
The normalized actual single-wavelength optical power of each channel
Normalization: The optical power of all channels must be converted to the optical power of the same spectral width.
If the spectral widths are inconsistent, assuming that the spectral widths before and after conversion are A and B respectively, and the optical power before and after conversion are Pa and Pb respectively, then: Pb = 10log10 (10^(Pa/10)/AB).
Corrected single-wavelength optical power (Pi) of MCA = Normalized Pi + (Total output optical power of OA – Sum of the optical power of all wavelengths scanned by MCA)
Average optical power
Average optical power = (P1/W1 + P2/W2 + ... + Pn/Wn) x 50
Pn: single-channel nominal power (unit: mW)
Wn: spectral width (unit: GHz)
N: number of supervisory signal wavelengths, excluding supervisory noise channels and non-supervisory channels
Why Is the Optical Power Flatness Indicator Required?
During long-haul optical transmission of a WDM system, the optical power of each wavelength differs greatly, which causes non-linear effects and severely compromises system performance. To prevent OSNR deterioration of optical transmission links caused by the optical power imbalance of each channel, and even communication quality deterioration or communication interruption, the optical power flatness of the system needs to be adjusted.
Optical Power Equalization
According to the power spectrum reported by power monitoring points, commission the optical power flatness based on the following rules:
1. If the optical power of a single wavelength is higher than the average optical power range, the optical attenuator value on the channel should be increased to decrease the optical power.2. If the optical power of a single wavelength is lower than the average optical power range, the optical attenuator value on the channel should be decreased to increase the optical power.
According to the locations of power monitoring points, optical power equalization can be classified into transmit-end, intermediate-level, and receive-end power equalization.
Thank you！
