A red LOS (Loss of Signal) light on a fiber modem indicates no optical signal reception, often due to fiber cable damage or loose connections. Verify that the optical transceiver is clean and properly. When your router displays a red light, it can be due to several reasons. Sometimes it may be due to a problem with your internet service provider, although you could also be experiencing this issue due to improper configuration of your router, a poorly connected cable, etc. Addressing this can seem daunting, but with a systematic approach, you can troubleshoot and resolve the issue effectively. In this comprehensive guide, we will walk you. If you've got a blinking red light on your router, there's something wrong with your connection. Home routers use colored LEDs to convey different.