What does a red light on an optical cable mean?
If a lot of red light is visible, the connector is bad and should be replaced. If you look from the other end and see light coming only out of the fiber, that indicates a good connector.
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After midnight that is likely because Openreach are doing work at your exchange on the kit that generates the optical signal. The tables in this article provide detailed information about the possible appearances of the LED lights on each device, the possible causes of each state, and what you should do. If you find that the Optical/Config/PON Light on your Fibre ONT (Optical Network Terminal) box is flashing, has gone off, or has gone red, this indicates there may be an issue with the fibre connection coming into your property. First noticed the SH2 flashing purple and lastly moved a unit out the way to get a good view of the Openreach modem. This is displaying a solid red LOS light - which I understand to stand for Loss of Service. Firstly call it in on the "faults" line - on 150 (VM Phone - free) or 0345 454 1111 (any other phone - national rate). A visual fault identifier or visual fault locator (VFI / VFL) is a visible red laser designed to inject visible light energy into a fiber.
