Hi there!
This time, I will share with you that design principle of the coherent transmission system
Dispersion compensation
Dispersion compensation is not required in new 100G networks or 40G/100G hybrid coherent networks.
When expanding 10G/40G networks to coherent networks, existing DCM configurations can be retained and only the transmission distance needs to be assessed based on network specifications.
Wavelength planning
Please refer to Commissioning rules for coherent transmission system/Selection of channels for mixed transmission of 100G, 40G, and 10G signals.FEC coding
Soft-decision FEC (SDFEC) is recommended for coherent signals during the hybrid transmission of 10G signals and coherent signals.
Client-side ports of 100G coherent boards
Before configuring services, you need to confirm whether the logical optical module type of the client-side ports is the same as the actual module type. If not, please modify the port type to the actual type.
ASON
Supports optical-layer ASON and electrical-layer ASON.
NOTE:
When a hybrid network supports optical-layer ASON, ASON network planning requirements, and guard band configuration rules must be satisfied.
TD20
The TD20 and other ROADM boards are used together to offer colorless applications in a coherent system.
The TD20 board applies only to coherent systems and its DMx ports can be connected only to coherent boards.
The TD20 board can receive and transmit a maximum of 20 signals. If there are more than 20 signals, the per-wavelength power of each DMx port will be excessively low, which may cause service interruption.
ITL
In a pure coherent system with channel spacing of 50 GHz:
No ITL board is required when the TN13WSM9/TN13WSD9, TN11WSMD9, or TM20/TD20 boards are used to add/drop wavelengths.
In the 100G coherent system that only uses SDFEC, you are advised to configure TN11ITL06 at the transmit and receive ends.
The TN11ITL04 board must be configured at the transmit and receive ends in any other scenarios.
VA4
It is not allowed to configure VOAs on the same VA4 board for an optical path in different directions.
EVOA
The VOA inside the OA board on the main optical path must be attached to the OUT port of the board.
SOP Tolerance
To deploy a 100G or beyond 100G coherent transmission system, pay attention to the following:
a. Underground optical cables are recommended.
b. If aerial optical cables must be used, you must set the hold-off time of routers to a large value to prevent the frequent switchovers of routers. The recommended value is greater than or equal to 200 ms. In addition, you are advised to configure SNCP to prevent service loss caused by SOP threshold crossing.
