How many years can the optical modem be used? A slight increase in light deterioration each year means it's aging, and replacing it with a new one doesn't cost a cent
this spring, I wrote about my mom cutting off the modem from a smart socket every night to save power. In the end, I found that the light degradation rose from -21.2 to -26.4, mainly because the weak current box cover was overwritten. At that time, the technician straightened the threads and placed the lid properly, thinking the matter was settled. Then in autumn, my mom called again, saying she would watch TV dramas at night and go around every few days. I then let her enter 192.168.2.1 to read light decay—-24.1. The external cause of the line pressing has been eliminated, so why does it only drop back by more than two dB compared to before the line adjustment? This time, the technician came for a re-inspection, checked the reassembly order (from March 2020), and said something I've remembered ever since: "This cat is now in its sixth year, the optical module is getting old, let's get a new one." I asked how much it was, and he said it wasn't cost.
the lifespan of a modem is completely different from a router
provide the caliber first. The civilian lifespan of devices like optical modems generally lasts five to eight years in dry, well-ventilated, and light-load environments, lasting up to ten years is not uncommon; Packed into a stuffy low-voltage box running at full load for seven by twenty-four hours, it starts to decline after four or five years. The core weakness is the optical module—the laser responsible for converting electrical signals into light. After three years, the transmission power starts to gradually decline. This is a physical trait, comparable to the aging of router capacitors—a 'terminal disease' that can't be cured and can only be replaced.
the difference in lifespan between the optical modem and router lies in the "who pays for the replacement." The router is your own asset; if it gets old or broken, you spend 200 yuan to buy a new one; Most optical modems are of rental equipment assigned by operators, with property rights listed in their rosters, and you only have usage rights. So when it ages or breaks down, the fault reporting process is free—not many people know this rule. Many people buy a new one online when the modem breaks, spending hundreds of yuan for nothing, and even bypassing the ITMS registration and binding system. If something really goes wrong, both sides will be blaming each other. Previously, I wrote about the process of replacing the cat for free during thunder strikes, and this time it's a sister piece: lightning strikes are accidents, aging is a natural law, and the latter is something every family will eventually encounter. I've also done some calculations on the router's lifespan. Retired machines can be replaced with APs for reuse. If you're interested, check how many years the router will last.
signs of aging appear in this order, with light decay always ranking first
the optical modem aging doesn't just suddenly break down one day, but rather a string of signals appearing in sequence. I ranked them in order based on the cases I handled:
first is always light decay. it is the only numerical, comparable evidence. A cat with a base rating of -20 will experience wear and tear that increases by about one dB per year; After three years, it rises by five to six dB, and after excluding external factors (line overshoot, dead bends, moisture), the price is still climbing, meaning the laser is losing power. Network speed is affected last—at -26MB, you might still be able to reach 500MB. If your speed really drops, it means the bits are already severe, so don't wait for a speed alert to check the numbers.
second is the tightening of network disconnection patterns. previously only once a month to two or three times a week, increasingly concentrated at night (higher laser temperature, further reduced power). I've written about how to match the four types of disconnected internet patterns, and see why optical modem always disconnects .
third is the gradual failure of reboots. early days when the network was disconnected and the modem could be restarted, it could be saved, but after rebooting, it only lasted ten minutes, and after that, even the PON light would flash for half a day before registering—this is the same logic as the router restart method failing; the hardware margin has run out.
The fourth is the built-in WiFi that crashes first. optical modem WiFi originally came with about ten devices, but after aging, it shrank to five or six. My mom's home has four cameras, a phone, and tablets, and every night they start crowding against each other. This signal can easily be stuck to the router's head. Note that the optical modem's WiFi and the router are separate transmission sources, so don't mistreat the target.
fifth and most hidden issue: firmware updates stoppage. old cat has been in service for five or six years, ITMS basically stops pushing it with firmware; the version you have is the end. How to check the version, why the official website can't download the package, and how to upgrade the firmware of the optical modem . The pause itself isn't fatal, but it means known issues won't be fixed, and when combined with other signals, the weight is significant.
judge that you haven't reached the age yet, check whether light decay "listens" and don't be fooled by absolute values
this is the experience I most want to share this time. Is it time to replace the Light Decay -24? Not necessarily—my F7015T had -21.8 after cable adjustment, -23.4 after being rescued from moisture, not much better than my mom's, but it obedient : once the external factors are resolved, the numbers drop; If something goes wrong, once it's resolved, it's stable.
My mom's car is different." After the lid was repaired by threading, the light decay dropped from -26.4 to -24.1 and then stuck at the same level, remaining in place for nearly half a year, even slowly moving back to -24.6. This is the boundary between aging and environmental problems: after eliminating external factors, the ones that can return are environmental diseases; The parts that can't go back and are still quietly crawling are the old parts. so the light deterioration ledger should be recorded once a year (my current habit is to copy the record during the annual checkup; the process is in the Family Online Health Check article). After comparing two or three years, the trend becomes clear. Looking at just one number, -24 is at the edge of the health range (-8 to -27, depending on the tier details Light Decay Special ), no one dares to draw conclusions.
If you haven't recorded the base number of
installations, don't panic. There are two remedies: first, ask for the installation work order for unit 10,000; second, start recording the current readings today. When my mom built up her PC in 2020, I wasn't used to it yet. This time, I started comparing from -21.2 (last winter), and it was enough.
replacement is free, but the sales pitch is skillful—don't say, "I want to get a new cat"
confirmed to be older, the three routes are arranged according to convenience:
| path | which path to take | who is suitable |
| 10000 report faults | report symptoms and light decay readings. After on-site inspection, replace | |
| upgrade packages with network disconnection or speed drops | For new cats applying for gigabit or above and needing to upgrade to 2.5G ports | those who already want to speed up |
| unified replacement in areas when operators roll out FTTR upgrades in batches | , the symptoms are not obvious yet |
focus on the first point: the wording. When calling 10000, don't say, "My optical modem is old and want to replace it"—this kind of statement can easily lead to buying it out of pocket or being told "the device is normal and not eligible for replacement." reporting symptoms and numbers: "Frequent network outages, solar degradation has risen from -21 to -24 during installation, and it's still rising. Restoring the factory won't help." There are readings and comparisons, and the work order is sent directly to the installation and maintenance team. The technician comes to the site to get a light power meter and measure. If it's really old, they replace it on the spot and take back the old machine. Technicians assess fault resolution rates and are more willing than you to replace everything in one go to avoid having to repair it three times every two days.
That's how my mom's family left. The technician came to measure the light degradation, checked the six years of the device's age, and took a new one from the car (with a 2.5G port), replacing it in ten minutes. By the way, I have calculated the threshold and benefits of upgrading to Gigabit for a new cat, and the differences between Tianyi Gateway 3.0 and 4.0 in this article: the differences between Tianyi Gateway 3.0 and 4.0.
three things to watch on the day of the upgrade: handling the aftermath is more important than the phone itself
change phone in ten minutes, take half an hour afterward—don't let the technician leave right after the change:
First, keep an eye on the PON light from slow flashing to steady on. registering a new cat takes one or two minutes. In some cases, data on the data center side may keep flashing. Have the technician contact the backend on the spot to handle it. Don't schedule a second time. Looking at the four checkpoints in the registration mechanismPON the lights kept flashing and the registration wouldn't go .
Second, read the new light on the spot and record the new baseline. my mom's new cat is equipped with a reading -19.8, which is more than four dB better than the old cat. This is the new "factory base value," which is for photo and archive. I did five tasks for my cousin's home during installation and acceptance, and they also apply to the replacement scenario: what to inspect on the day of broadband installation.
Third, handle the aftermath according to your home's configuration. is the simplest for ordinary families; WiFi name and password let the technician set it as before, making all family devices feel untouched; If you have changed the bridge, remember to copy back the VLAN connected to the OTHER in the WAN table, otherwise the IPTV will go black. The process depends on whether the optical modem should be changed to bridge; After changing a bunch of settings, export a copy of the conf before switching devices. The old cat's configuration files can't be directly imported across machines, but copying parameters is useful: How to export and back up configuration files.
the last step at my mom's house was something I did casually: unplug the smart outlet that cuts power off every night from the optical modem and move it to manage the TV's standby power consumption. The first few years of a new cat are at a good time, so stop messing with it with the power cutoff—I calculated that energy-saving bill in the whether the cat should be restarted regularly, and it costs less than one yuan a day, not worth it.
three situations, don't rush to change
don't just change because the light deterioration is high. First: Light decay stabilizes below -25, fluctuates within one dB per year, and the internet speed is normal—this is a healthy cat, don't mess with it. Second: High light degradation but no external cause investigated—first tidy the cable, wipe the fiber end, move the cat out of a dark corner. Replacing the cat after removing the external cause and the cat can return is a waste. The third type: Encouraged by the "New Cat Faster" model but only has 2-300 Mbps broadband—the optical modem upgrade brings 2.5G ports and WiFi 6, but below gigabit broadband can't satisfy these needs. Upgrading just for the sake of switching brings no benefit; upgrade broadband first, then talk about modems.
conversely, don't drag down the following groups: those whose light deterioration has increased by more than five dB over three years, those whose network disconnection frequency has changed from monthly to weekly, those whose built-in WiFi devices have noticeably declined, or those whose firmware updates are interrupted and other symptoms combined. If you have two or more bars, you get 10,000 and read the light decline number.
| your family's situation | actions |
| light degradation is stable within -25, internet speed is normal, | is stable. Record the data once a year |
| . If light degradation is high but no external cause has been checked | first trim the cable, wipe the head, move the position, and retest |
| after removing external causes, it still crawls, or it may have two aging signal | 10000 faults. Symptom + reading |
| should have been upgraded to gigabit | and requested to replace 2. 5G Kouxin Cat |
to wrap up, here's the order: check for light degradation→ exclude the exclusion cause→ retest and record the ledger→ accounting for two aging signals→ number 10,000 to report the numbers→ technicians to replace the → on the spot, monitor PON registration→ record new bases→ and handle the setup as before. I've been using the modem for six or seven years. If it breaks, it doesn't cost you money, but the delayed network disconnections and speed drops require your patience every night.
