Simply activate the meter, connect the cable, and check the display for a power level between -15 and -25 dB. A reading above -25 dB indicates insufficient power, which could be the problem. Furthermore, a visual fault locator laser is crucial for pinpointing a cable's. LED Indicators on a Fiber Router: What Do They Mean? Understanding LED Indicators on a Fiber Router Let's break down what the common LED lights on a fiber router mean and how they behave: 1. POWER Normal: Solid/stagnant light. If OFF: The router is not powered — check the socket, adapter, or power. When issues like signal loss, slow speeds, or intermittent connectivity arise, systematic troubleshooting is key. This guide will walk you through diagnosing and resolving common fiber network issues efficiently. Why Do Fiber Networks Fail? Despite their robustness, fiber networks can fail due to:. A red LOS (Loss of Signal) light on your router or ONT usually indicates that the device is not receiving an optical signal from the fiber network. Hardware Failures : Faulty transceivers, switches, or routers.