When there is a power outage, the PON light of the optical modem keeps flashing? If the registration is not completed, there will be no internet. Three minutes is the dividing line when the watch is pressed.

Last month, the community's power lines were out for maintenance during the day, and the call came in at six o'clock in the evening. My mother called right away: 「There is no signal on the TV, and the WiFi on your dad’s phone is spinning in circles. Has the line been cut again? 」I looked in the background and saw that the router was fine, but the PON light on the optical modem kept flashing. My dad was there to give me advice: 「Try unplugging the cat and reinserting it. 」Plugged in, still flashing. The old lady was anxious to make a repair call, but I held her down - only forty seconds had passed since the call came in.

After waiting for more than two minutes, the PON light froze on its own and the network came back. My parents asked what the flash was doing just now. I said it was "checking passwords" with the computer room, and then they let you go online after checking. Later, there was a power outage at my sister's house and the circuit breaker at my mother-in-law's house tripped. The same scene happened twice more. This fact is too common, but 9 out of 10 people don’t know how long it takes for the light to flash to be considered normal or how long it takes to indicate something is wrong. I’ll write this down once and for all.

Let’s talk about the conclusion first: Flashing for less than three minutes is a normal process

After the optical modem is powered on, it does not have the Internet when it is plugged in. It must first re-establish contact with the OLT in the computer room (that is, the operator's large equipment that manages dozens or hundreds of households), which is called "registration" in jargon. The whole process is: The optical modem first sends a signal and shouts "I'm here", and the computer room hears it and arranges a seat for it (you must first calculate the light distance from your home to the computer room so that you can allocate a time slot for the call. If you don't line up with dozens of households rushing to shout at the same time, it will be chaos). After matching the code, the computer room will push down the configuration one by one - which virtual channel should be used for broadband, which channel should be used for telephones, and which channel should be used for TV? It all depends on the distribution at this time.

The PON light is the progress bar of this process: Flashing = registration in progress, lit = registration successful . Normally, it takes less than a minute to turn on the power until it is always on, and it takes less than two or three minutes. When the computer room is busy at night, it can take more than half a minute. I later checked the watch three times on my own optical modem.: One cold start took 1 minute and 40 seconds, and two power outages and restarts took 55 seconds and 2 minutes and 10 seconds respectively. So my caliber is: If it flashes within three minutes, do something else. Don't pull or press.

Easily distinguish another lamp: LOS flashing red means "no light is received", which means the physical layer is broken (the fiber is bent, cut, or the optical splitter is faulty), which is two different things from registration. If LOS does not light up in red and PON flashes there, it is normal registration and waiting. Why are the two lights facing each other? I'm here The optical modem indicator light article A comparison table has been written here.

Why are calls so slow after a power outage?

Normally, the light will turn on within one minute after restarting, but after a power outage, it will easily turn on for two or three minutes. This is not an illusion. There are dozens of households connected to a PON port (our building has a 1:64 light split, one to sixty-four). When there is a power outage, all sixty-four cats are disconnected at the same time. ； As soon as the call came in, all sixty-four stations were powered on at the same time and started shouting "I'm here" at the same time. The computer rooms have to be dealt with one by one, and where your home is ranked depends on luck. My sister's building received a call at night, and her cat waited almost four minutes for the light to turn on. Her neighbor upstairs was one minute ahead of my sister - they were in the same building, but there was a difference in the queue order.

There is another layer: The "seat" hanging in the computer room before the cat lost power has expired, and you have to take a new seat and get a new configuration. This configuration distribution channel is the system used by the operator to remotely manage the light modem. ITMS usually uses this system to secretly change your home WiFi in the middle of the night - I am using this mechanism. ITMS and TR-069 It has been dismantled. Therefore, in the two minutes after the call comes in, it is not just "connecting to the Internet", but also re-establishing your three business channels of broadband, telephone, and IPTV.

By the way, explain a counter-intuitive phenomenon: After the call came in, WiFi was quickly available on the router, and the phone was also connected, but could not access the Internet. Because the section between the router and the optical modem is connected, the WiFi is naturally full. ； What is broken is the section from the optical modem to the computer room. It’s useless to look at the WiFi grid number. The correct thing is to look at the PON light of the optical modem.

pinch meter dividing line: Three minutes, ten minutes, half an hour

It's okay to just wait, but you have to have something in mind. I summarized the three power outages at home plus the several times I helped my neighbors check into a table.:

Every three to ten minutes, my parents’ house catches up with them: At that time, the light failure was always hovering on the edge of -27, and after a call came in, the cat had to try several times before registering. What is light attenuation and where to check the number in the background? I wrote an article What to do if the light fades greatly , after the number of -28, it’s the end of your own efforts.

If it’s still flashing after more than ten minutes, do two things first.: Check if the LOS flashes red at the same time (if it does, it’s a matter of the optical path, first check whether the pigtail is bent by furniture) ； Power off the cat again, wait a minute and power it on again, giving it a chance to queue up again. I tried everything and it still flashed, so I called for repair, but the error message was "PON light is flashing and cannot be registered, restarting is invalid." When the technician heard this, he knew that it was not your problem, so he didn't have to come to your home to blame your router first.

Don’t do the opposite of the two things after you call.

The first thing is, don’t pull out and plug in again and again. Just unplug the power when the light flashes and plug it back in, which is equivalent to canceling the half-way queue and re-queuing. My mother did this the first time. What was supposed to be a two-minute job was forced to take five minutes. Unplugging and replugging is only useful at one time: After flashing for more than ten minutes, it was determined that it was stuck, so I queued it up again.

The second thing is, don’t be in a hurry to restart the router. The first reaction of many people after calling is to restart the router, but the order is reversed - the optical modem is still registered, and the router is still offline after restarting. By the time you configure the router, the optical modem end has already been connected, and you think that restarting the router will help. The correct order is always: The optical modem PON is always on, and then turn on the router. It takes a minute or two for the router to be powered on until the WiFi in the whole house can be used. That is another process. I am How long does it take to get online after restarting the router? I checked the stopwatch, and if I put the three minutes together with optical modem, it would be normal for the entire house to return to the Internet five minutes after the call came in.

Several special situations of "flash" that you should be careful about

There is a flash method that needs to be picked out alone: The PON light flashes, and the LOS flashes red at the same time, or the LOS simply lights up red. This is no longer "slow", but something happened to the optical path itself - the pigtail was caught by the door, the wire in the weak current box was gnawed by mice, and the end of the optical splitter in the corridor was broken. No matter how long you wait, you won't be able to register, because it won't receive light at all, and it has nothing to do with queuing. The key to distinguishing is to look at the two lights facing each other: Only the PON flash is the queue, and the LOS is mixed in and is the light path.

The other is "flash steady for a while, then start flashing again after a few minutes", jumping back and forth. This is probably because the light attenuation is close to the critical value, or the port at the other end of the computer room is being adjusted. Observed for a long time, recorded the duration, and reported "repeated PON registration and light attenuation value" when reporting for repair. The master could handle it much faster.

There is another kind of injustice: PON is always on, but the network is still down. Then the problem is not at the optical modem level, it is either at the broadband account level (arrears, authentication issues), or at the router dial-up level. If your optical modem is in bridge mode and the router is responsible for dialing, the dialing on the other end of the router will have to be done again after a call comes in. I will write down the troubleshooting there. How to divide the blame when dial-up fails after bridging? Inside.

ending: A small thing worth doing before a power outage

After these few times, I set a rule for my parents’ house: Don't wait around when there's a power outage. After a call comes in, take a look at the PON light. If it's flashing, set an alarm for three minutes, and don't move until it rings. If it still flashes after three minutes, follow the watch above again. The old lady is more familiar with it than I am now. She called me again last month. Her original words on the phone were, "The PON is still flashing. I'll wait for you for three minutes before calling you." Three minutes later, she hung up the phone and went to watch TV.

Also, let me mention an easy pitfall: Some people are afraid that their cats will "burn out" and immediately unplug their cats when the power goes out, then plug them back in when the power comes. Occasionally it's fine, but if I do this often, I'll have to wait in line for registration. Normally-on devices such as optical modems are designed to be powered on 24/7. The fear is never "on", but frequent power outages and restarts. If you want to know the impact of long-term intermittent restarts on light decay, you can read what I wrote before. Should optical modem be restarted regularly? , which contains two years of comparative data on my two cats. You really can't control the power outage. What you can control is your hand in the three minutes after the call comes in. Resisting from unplugging the power is the greatest kindness to it.