Have You Ever Meet Of The OCTL Port Application in the OptiX OSN 1800

Summary
An OCTL port on a TNF1SCC boards can only be connected to an OCTL port on a CTL board of an OADM frame through a straight-through network cable. Due to the fact that the OCTL port appears similar to a common network port, the OCTL port is likely to be misconnected and short-circuited, causing a blown fuse on the TNF1SCC board and a power failure on the OADM frame.

[Problem Description]
Trigger conditions:
The normal application scenario is: An OCTL port on a TNF1SCC board is connected to an OCTL port on a CTL board of an OADM frame through a straight-through network cable.
Any other application scenario is possible to trigger this problem. For example:
A. An OCTL port on a TNF1SCC board is connected to an OCTL port on a CTL board through a non-straight-through network cable.
B. An OCTL port on a TNF1SCC board is connected to a non-OCTL port (for example, an SW port).
Symptom:
1. When a TNF1SCC board is connected to an OADM frame, the OADM frame is not powered on and its RUN indicator is off.
2. The OADM frame cannot be managed.
The following is a schematic connection diagram of  Huawei OSN product like OptiX OSN 1800 OADM frame and an OptiX OSN 1800 I chassis.

Identification method:
1. The TNF1SCC board is running normally but the OADM frame is not powered on, its RUN indicator is off, and it cannot be managed.

2. When the OADM frame is connected to an OCTL port of another TNF1SCC board, the OADM frame is powered on normally with an RUN indicator turned on and can be managed. It can be determined that the OCTL port on the previous TNF1SCC board is faulty with a blown fuse.

[Root Cause]
An OCTL port on a TNF1SCC board, which supplies power to the OADM frame, appears similar to a common network port. If the OCTL port is connected to a network port, the OCTL port will be short-circuited, leading to a blown fuse in the protection circuit of the OCTL port on the TNF1SCC board. This fault, however, does not affect the operation of the TNF1SCC board.
The following is a schematic power supply diagram of the OCTL port on the TNF1SCC board.

Functions of the fuse:
The fuse on the TNF1SCC board is used for protecting power outputs to the OADM frame and implements hot swap protection together with the transient voltage suppressor (TVS), ferrite bead and capacitor included in the protection circuit shown in the blue box. The operating principle of the fuse is as follows:
A. When the connected OADM frame is working normally, the fuse current is about 0.2 A, far lower than its rated current 2 A. The fuse is working normally and serves as a power line.
B. When the connected OADM frame is faulty, for example, is short-circuited, the fuse has a transient current far higher than the rated current 2 A. As a result, the fuse blows and the protection circuit is opened to isolate the power supplies and components inside the TNF1SCC board. The opened protection circuit can be restored only by replacing the TNF1SCC board.