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This post contains the rules for band-splitting dispersion compensation. Please find them as you read further down.
RULES FOR BAND-SPLITTING DISPERSION COMPENSATION
The DCM compensation for different wavelength signals slightly deviates. After the signals are transmitted over a certain distance, the compensation deviation cumulates to a notable amount. Hence, band-splitting dispersion compensation is required.
In the case of the NRZ OTU, no band-splitting dispersion compensation is required.
In the case of the DRZ OTU, when the SMF-28 fiber where the regenerator section is longer than 1500 km is used in networking, DSE01 band-splitting compensation is required. In band 2 of the DSE01, use DCM(10)-for G.653 for compensation. In the other two bands, use mechanical variable attenuator for connection.
In the case of the DRZ OTU, when the SMF-28 fiber where the regenerator section is longer than 2000 km is used in networking, DSE01 band-splitting compensation is required. In band 1 of the DSE01, use DCM(10)-for G.653 for compensation. In the other two bands, use mechanical variable attenuator for connection.
In the case of the original network where the CRZ boards are used and DSE01 boards are configured, DRZ boards can be used.
TRANSMISSION IN MIXING FIBERS
In the case of mixing fibers, the compensation is performed by following the proper rules for each fiber type in the line. Perform compensation based on the residual dispersion that ranges from –10 km to +10 km for SMF-28. When calculating the residual dispersion of LEAF, convert the length of SMF-28 into that of LEAF based on a ratio of 1:4 of SMF-28 to LEAF. Plus the residual dispersion of LEAF, the total residual dispersion range meets the requirement mentioned in section 2.6.
SPECIAL APLICATION - USING G.652 DCM to COMPENSATE LEAF
When using G.652 DCM to compensate LEAF, the replacement calculation is used according to the ratio 1:4. The dispersion slopes of G.652 fiber and LEAF are different. When used to compensate LEAF, the G.652 DCM does not comply with the dispersion curve of LEAF completely. For the OSNR tolerance, the optimization specification of the "OSNR Optimization Specifications" cannot be used. The specifications of the earlier stage are required. Please see the table below:
OSNR of the LBE (AFEC) board > 20 dB |
OSNR of the LWF (FEC) board > 19 dB |
OSNR of the TMX (AFEC) board > 17.5 dB |
OSNR of the LWF (AFEC) and the LOG (AFEC) boards > 17 dB |
When G.652 DCM is used to compensate LEAF, the dispersion matching degree is low. Hence, this replacement mode is limited by distances.
1. Distance within 400 km: Completely use G.652 DCM to compensate the LEAF fiber. Pay attention to the evenness of the dispersion compensation. It is subject to 1:4 replacement compensation. Use G.652 DCM-A and DCM-B as much as possible. Do not use other DCMs with higher specifications. The dispersion compensation at the receive end should be in 10 km to 60 km of the under-compensation LEAF.
2. Distance ranging from 400 km to 550 km: When the distance is within 400 km, it is subject to the above rule. For the distance exceeding 400 km, use the LEAF DCM for the compensation. Besides the requirements listed in the above table, extra 1 dB OSNR should be considered, with the consideration of unmatched dispersion. The dispersion compensation at the receive end should be in 10 km to 60 km of the under-compensation LEAF.
For example: The length of the multiplexing section is 530 km. After G.652 DCM is used to compensate for dispersion in 400 km, the followed 100 km should be configured with the LEAF DCM for compensation. Finally, the under-compensated length is 30 km (LEAF).
3. Distance longer than 550 km: Use LEAF DCMs, and keep the system in the under-compensated state. The LEAF DCM is used for the complete compensation (100% dispersion compensation). G.652 DCM should not be used for the compensation of LEAF.The residual dispersion at the receive end should be in 10 km to 60 km of the under-compensated LEAF.
REMARKS
1. When the network is required to support the single wavelength 40 Gbit/s service, the 40Gbit/s service has strict dispersion requirement. If G.652 DCM is used to compensate the LEAF fiber, the dispersion cannot meet the 40 Gbit/s service requirement owing to the serious dispersion slope. If necessary, contact the technical manager of the Marketing Dept. of Huawei.
2. Note:
This compensation mode sacrifices the capability of future expansion (40G, DRZ long-haul transmission) to slightly lower the DCM cost. Hence, this mode is not preferred.
