If the Alarm light is red, it's likely that the ONT has detected an error or fault. Restart the ONT to see if the issue resolves itself. If a fibre optic cable gets kinked it usually stops working. What is the red light on my optical cable? The red light of a laser is coupled into the core of an optical fiber in a targeted manner (an LED is usually too. The Optical Network Terminal (ONT) is a crucial device in modern telecommunications, serving as the interface between your home network and the fiber-optic internet connection provided by your Internet Service Provider (ISP). One of the key aspects of the ONT is the array of lights on its front. It's the ONT if it's the LOS (loss of signal) light that is lit Hub is orange light TBH, the LOS light being lit means the router lights are irrelevant, they must be in a fault status because the underlying network is in a fault condition. Left to right: Power, Fiber (Optical Interface), Lan, Alarm 20K subscribers. A router showing a red light can mean different things, like a service outage, misconfiguration, or loose connection, all of which can lead to a broken internet connection. Fortunately, there are heaps of ways to fix a red blinking light on your router. One of the first things you should try is to. The signal is optical, so if you don't see the red on both ends, it's damaged. Don't buy anything silly expensive, anything at Monoprice is fine. What is an optical connection? Digital optical is a physical connection that uses fiber.