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How to fix a Red LOS Light on your WiFi Router?

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To fix a red LOS light on your router/ONT, start by checking that the fiber patch cord is firmly clicked into the ONT's PON port and undamaged, then power cycle the device for 30 seconds. If the light stays red, check your ISP's app or helpline for an area outage before calling support. In most cases, the fix is either a loose connector, a damaged cable section, or a problem on your ISP's side - not something wrong with your router's settings or your WiFi.

A red LOS (Loss of Signal) light means your router or ONT isn't receiving a signal on its fiber/WAN input.

If you're not sure what LOS means or want to understand how fiber signal loss works, read our explainer on what LOS means in WiFi routers.

Which red light are you seeing?

Routers and ONTs have multiple LEDs. A red light on a different indicator means a different problem.

LOS red - no fiber signal reaching the device. That's what this guide fixes.

Internet/Globe red - fiber signal is fine, but the device can't authenticate. Usually an account or PPPoE issue, not a cable problem.

Power red or off - hardware or adapter fault. Try a different power adapter.

PON red - ONT can't register with your ISP's exchange. Often accompanies red LOS. If PON is red but LOS is green, it's a backend provisioning issue - call your ISP.

If your red light is on the LOS indicator, continue below.

Table of content

Solid red vs blinking red - does it matter?

Solid red usually means zero signal on many ONTs - fiber disconnected, cut, or ISP equipment offline. If you haven't touched any cables, the problem is likely upstream. The exact behaviour varies by manufacturer

Blinking red usually means signal is arriving but too weak or unstable to lock on. Dirty connectors, micro-bends, or a degrading splice are common causes. Worth inspecting your cable and connector before calling support - the issue may be inside your home.

if your LOS light is solid red and you haven't touched any cables recently, the problem is more likely upstream (ISP outage, fiber cut outside your home). If it's blinking, it's worth spending more time inspecting your cable and connector before calling support - the issue may be inside your home.

Step-by-step: fix the red LOS light

Work through these in order. Most LOS issues resolve within the first three steps.

1. Check the fiber patch cord connection

The single most common cause of red LOS is a connector that isn't fully seated. Trace the thin fiber cable (usually yellow or white, with a green SC/APC connector) from the wall junction box to the ONT's PON port. Push the connector in gently until you hear a click.

If you have a separate ONT and WiFi router, the LOS light is on the ONT, not the router. The Ethernet cable between ONT and router is a different connection entirely and won't affect LOS.

2. Inspect the cable for physical damage

Fiber cables are fragile. Look for sharp bends tighter than roughly the diameter of a tennis ball (about 30mm bend radius) - signal degrades rapidly below this. Also check for crushed sections under furniture legs or door hinges, cuts, fraying, or rodent bite marks. In Indian apartment buildings with exposed fiber runs through ceiling ducts, rat damage is more common than most people expect.

If the cable is visibly cut or damaged, stop here and call your ISP. Fiber splicing requires a fusion splicer - you can't fix this at home.

3. Clean the fiber connector

Dust on the fiber tip blocks optical signal. Even an invisible speck can trigger LOS, especially after construction or renovation work nearby.

Pull the green SC/APC connector out of the ONT's PON port gently. If available, use a fiber cleaning pen. Otherwise, a clean lint-free microfiber cloth is safer than ordinary fabric.Avoid household cleaners or water. Unless you have proper fiber-cleaning materials, it's safer to use a dry lint-free wipe. Don't touch the ferrule with your fingers - skin oils degrade signal over time. Reinsert until it clicks.

4. Power cycle the ONT

Unplug the ONT from the wall socket. Wait 30 seconds. Plug it back in and wait 2-3 minutes for it to re-register with your ISP's OLT (the equipment at their exchange).

Watch the lights during restart: Power turns green first, then PON blinks while registering, then PON goes solid green, and LOS should stay off. If LOS turns red again after PON stabilizes, the issue isn't a temporary glitch - move to the next step.

Don't confuse this with a factory reset. A factory reset (pinhole button held 10-30 seconds) erases your WiFi name, password, and ISP configuration. Jio and Airtel gateways re-download settings automatically after reset, but BSNL and local ISP ONTs often need manual PPPoE re-entry - so don't factory reset unless your ISP specifically asks you to, and have your credentials ready before pressing the button.

5. Check for an ISP outage

If LOS is still red, check whether the problem is on your ISP's side before spending more time at home. A fiber cut on the street, a faulty splitter in the building, or maintenance at the exchange will all show as red LOS - and none of those are fixable from your end.

How to check, by ISP:

      • Jio Fiber: MyJio app (JioCare section), call 198 from a Jio number, or 1800-896-9999 toll-free. WhatsApp: 70005-70005.
      • Airtel Xstream Fiber: Airtel Thanks app (outage alerts on home screen), call 121 from an Airtel number, or 9810012345 from any phone.
      • BSNL Bharat Fiber: Call 1800-345-1500 toll-free, or dial 198 from a BSNL number for fault booking. Portal: selfcare.bsnl.co.in.
      • ACT Fibernet: ACT app or selfcare.actcorp.in. Toll-free: 1800-1022-836.
      • Hathway / local LCO: Most don't have outage dashboards. Call them directly or ask neighbors on the same connection.

Quick shortcut: ask a neighbor on the same ISP whether their internet is working. In apartment buildings, multiple flats often share a fiber riser, so an area outage typically affects the whole building or floor, not just you.

6. Check for account suspension

A few ISPs may deactivate service in ways that resemble a connectivity problem, but unpaid bills more commonly affect authentication rather than causing a LOS indication.

Check your account status in your ISP's app or portal. Renewing or recharging usually restores signal within 5-15 minutes without needing a technician.

7. Call your ISP with the right details

If none of the above fixed it, the problem is upstream - a fiber cut, a faulty splitter, or equipment failure at the exchange. You need a technician.

Have this ready before you call (saves time and avoids repeat callbacks):

      • Registered mobile number and customer/account ID
      • ONT model (printed on the label on the bottom or back)
      • Which lights are on, off, or blinking, and what color
      • When the problem started
      • Whether neighbors on the same ISP are also affected

Take a photo of the ONT's front panel showing all the lights. Jio and Airtel support teams accept photos on WhatsApp and diagnose faster from a photo than a verbal description. Always ask for a ticket number and ETA - it lets you escalate without re-explaining if the issue isn't resolved on time.

How to prevent red LOS from recurring and common causes in Indian Homes

Don't bend or tug the fiber patch cord. Route it along walls or inside cable channels. Keep it away from door hinges and furniture legs - a door slowly crushing the cable over months is one of the most common causes of intermittent LOS in Indian homes.

Get a mini UPS for the ONT. Fiber ONTs lose sync completely on power loss and must re-register on every restart. In areas with frequent power cuts, repeated restarts can leave the ONT stuck in a failed state showing red LOS even when the fiber signal is fine. A mini UPS helps prevent LOS events caused by repeated power interruptions

Building construction. Contractors drilling walls or replacing lift shafts regularly cut fiber risers without realizing it. If LOS starts during renovation work, tell your ISP so they send a splicer-equipped technician.

Monsoon and water ingress. Outdoor fiber splice boxes on building exteriors aren't always sealed properly. Heavy rain causes signal loss - more common with local LCO installations than Jio or Airtel infrastructure.

Door hinge crushing the patch cord. The cable runs along the floor through a doorway, and the hinge slowly crushes it over months. Signal degrades gradually - intermittent blinking LOS first, then solid red.

Frequent power cuts without a UPS. Fiber ONTs lose sync completely on power loss and must re-register on every restart. Repeated cuts can leave the ONT stuck showing red LOS even when fiber signal is fine. A mini UPS helps prevent LOS events caused by repeated power interruptions.

Frequently asked questions

Can a factory reset fix a red LOS light?
 Almost never. LOS is a physical signal issue, not a software problem. A simple power cycle (unplug and replug) achieves the same reset without wiping your WiFi name, password, and ISP configuration.

How long does it usually take for the ISP to fix it?
 For area outages from a main fiber cut, most major ISPs (Jio, Airtel) resolve within 4-12 hours. For last-mile issues specific to your flat or building, expect a technician visit within 24-48 hours. BSNL and smaller LCOs can sometimes take longer. The ticket number is your leverage for escalation.

Is it safe to look into the fiber connector to check if light is coming through?
 No. Never look directly into the fiber connector. Although the infrared light is invisible, it can still be hazardous to your eyes. The LOS indicator on the front panel tells you everything you need to know.

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