Optical receivers often drive a “LOS” (Loss Of Signal) indicator, where lit or blinking LOS lights flag a missing or weak optical input. Meanwhile, a separate link LED shows whether the module has locked to the light level and negotiated. Those tiny lights next to an Ethernet jack might look like a subtle decoration, but they're actually a real-time health meter for your wired network. When you know how to read status LEDs, you can confirm connections at a glance, spot speed mismatches before they slow you down, and zero in on a bad. Every ONT is a little different, but the lights are almost always in the same spot. On most models — including the Langzhi L801, L880G, and L881G — you'll find the indicator lights on the front panel, usually with small icons or text labels underneath. All these. The following table lists the Ethernet LED indicators. Power supply is operating normally. Both PSUs are in the bay with active power.
