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In DWDM systems, management signals can be transmitted using ESC (Electrical Supervisory Channel) or OSC (Optical Supervisory Channel).
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These management signals originate from the control board of the equipment shelf.
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They are sent through the backplane to the respective card and then transmitted as a signal.
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When carried within the OTN overheads, the channel is referred to as ESC.
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When transmitted as a dedicated optical signal (Layer 0) over wavelengths such as 1510 nm or 1490 nm, it is called OSC.
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Since OSC/ESC share the same line fiber with C-band traffic, they must operate on separate wavelengths outside the C-band (commonly asked in interviews).
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The OSC board has multiple roles:
- Transmits management signals.
- Processes IEEE 1588v2 clock signals for network synchronization.
- Supports line fiber monitoring by sending test signals and analyzing reflections to assess fiber performance and quality.
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A practical example is the AST2 board in the Huawei OSN 9800, which integrates OSC, synchronization, and fiber quality monitoring functions.
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