In OSN 7500 we use the SLT1 board in a customer network.
After adding two cascaded attenuators it was observed that after some time there is IN_PWR_ABN alarm appear on the board and after some time if not rectify the STM1 can be down.
Check the patch cord condition
If found twisted near door surface or any other location lightly massage the fiber only on twisted area if the normal power recover then patch cord is ok
If twisted at the angle of 90 degree then patch cord should be replaced.
Keep the door of NE slightly open.
After analysis it was found that after adding the cascaded attenuators the door surface touches the patch cord and push it in OSN 7500 so after changing one patch cord problem resolved.
But after some time the problem appear again so we find that if we keep the door slightly open then the alarm is not appearing.
I have already given a product suggestion in this regard.
To avoid such situation keep the door slightly opens and make cleaning plan on weekly basis.
Try to replace the cascaded attenuator with one if possible.