What do the indicator lights for optical modems represent? LOS flashes red, PON doesn't light up, so check the color of the lights yourself

first identify the lights: the row of lights on the optical modem is one

Different brands have slightly different names for light modems, but they always fall into these categories. Take my TEWA-750G as an example: from left to right, it includes the power supply, PON (some machines mark "Registration" or "Authentication"), LOS (some labeled "Optical Signal"), LAN (network port, some have one light per port), WiFi, and telephone. The meaning is as follows:

remember one division: PON tube for 'authentication', LOS tube for 'optical path'. LAN manages the of 'inside your home.' LOS red light means the optical path is cut off; PON flashing means the carrier hasn't let you online; LAN not turning on is your own home line. Check the three areas separately, don't randomly pull out the cable right away.

LOS Red light flashing: The optical path is broken. Try checking the fiber first

LOS A flashing red light is the most common reason for network disconnection, meaning the optical modem "cannot receive the light signal." At this point, no matter how you try to restart the router, it won't work—the problem lies with the fiber. But cutting fibers doesn't necessarily require a technician to come to you. A significant portion of the problem is with the tail fiber section at home. First, do three things:

First, run the fiber along the blue (or green) connector on the back of the optical modem to see if there are any dead bends. Optical fiber is much more delicate than network cables; the bending radius is less than 3 centimeters, the signal drops sharply, and when bent to a right angle, it equals a half-broken . Last time my family lost the internet, I moved the cabinet and pressed the tail fibers into a crease. After straightening them, the light turned green in thirty seconds. If you suddenly lose internet after moving or tidying up, it's probably because of this.

Second, look at cold contacts. When you unplug the fiber plug and look at the light, dust, fingerprints, and oil stains on the end face will all block the light. You can wipe it with anhydrous alcohol mixed with a lint-free cloth, never dry it with a paper towel, and never touch the with your fingers—the oil on your fingers is even harder to get rid of than dust. Remember the direction before pulling, plug it back in, and hear a click.

Third, if the red light flashes after touching, that's the section from the corridor splitter to the computer room. Oxidation of the fusion fiber, splitter failure, or cable being cut off are all possible issues. These can only be repaired. When reporting a repair, just say "Optical modem LOS red light flashing," and the data center can remotely measure light degradation and breakpoints, much faster than saying "The network is dead."

PON light keeps flashing: Authentication is stuck, most likely due to data issues on the carrier's side

LOS the PON keeps flashing. This is the most confusing case—the optical path is open, but the optical modem's authentication on the carrier's side hasn't passed and can't get online. If you encounter this kind of situation, do two steps first: turn off the power to the modem for one minute before powering on (if the modem runs for several months without shutting down, it will freeze; typical signs are certification freezes; I've encountered this twice, just turn off the power and restart); If that doesn't work, check whether the optical modem has been tampered with or replaced. replacing the optical modem, you must contact the carrier to re-register the data. If you buy it yourself or a second-hand device, plugging in the PON will cause persistent flashing. This isn't a malfunction, it's not registered. Call customer service to report the LOID (on the label on the back of the optical modem) and ask them to register it in the backend.

Another situation is when PON is evergreen but the internet speed is extremely slow and frequent disconnections. This is usually due to severe light degradation, which is considered "half-dead." Below is a separate explanation.

lights all green or no network: The problem isn't with the optical path. Check the power supply at

home, PON is all green, LOS off, but the optical modem is actually working fine now. If there's no internet yet, check inside. The key is the LAN light: the network port light on the router connected to

doesn't work, so first replace the network cable and check if it's plugged in the wrong port. Not every optical modem from carrier is gigabit port. For example, the ZTE F7015T only has gigabit port 1 and 100Mbps IPTV—my neighbor connected the router to the IPTV port, the lights were on, the network connected, but the speed just wouldn't go up to 100Mbps. After a long search, it turned out to be the wrong port. There was a print next to the net, so I squatted down to look carefully before inserting it. How do you divide the tasks between the IPTV port and the network port, and how do you reuse a single cable? I previously wrote a detailed article explaining how to connect IPTV and broadband with a single cable .

the network port light is on and off, the optical modem basically rules out suspicion. Next, check the router. I wrote about a six-step troubleshooting process in the of the router's WAN port light, dial-up status, and error codes, which I wrote about in the article about the router's red light coming on. I won't repeat it here. In short: the modem is green, stop bothering with it—check the router and network cable .

the management page to check light depreciation: This is a hard indicator to judge "half-dead

light degradation (received optical power) is the most critical number for judging optical path quality, and it's available on the optical modem's management page. Go to 192.168.1.1 in your browser, and on the back tab you'll find your regular user account password (usually useradmin or similar). After logging in, look for 'Status' or 'PON Info' and 'Optical Module Info', where you'll find 'Receive Optical Power'. Unit: dBm, which is negative. reference range: -8 to -27 dBm is considered healthy; -27 to -30 is the edge of deterioration; above -30, you basically lose .

my home internet speed mysteriously dropped to tens of megabytes and disconnected at night, the light degradation had already reached -29.6dBm. When reporting the repair, I reported this figure to customer service, and the technician came directly with a fusion machine to remelt the hallway joints, returning it to -18dBm, and never lost the line since. You can't tell this number by looking at the lights yourself. A fully green light doesn't mean light degradation is normal. So for the issue of 'slow internet but still working,' the first step is to check the light degradation on the management page. By the way, if you want more information about the optical modem, you need to visit the super administrator account. I wrote about how to get it in the of the optical modem bridge modification.

a single table: the lights are off, so follow this chart

compress all the content into one table, and when the network is disconnected, it's taken as a result:

here's the order: check the outstanding fees→ check LOS→ check PON→ power off and restart the optical modem→ check LAN and network cables→ go to the management page to check light degradation→ bring all the information before requesting repair. When reporting for repair, if you get a 'LOS red light flashing' or 'light decay -29,' the technician basically knows what to bring, so you don't have to go back and forth. Most LOS and LAN issues can be resolved in ten minutes by myself; the real on-site issues are the light decay issues and the corridor splitter section.