How can I tell if a customer issue is fiber or WiFi?

Plug a laptop directly into the ONT's Ethernet port. If wired works but WiFi does not, the issue is the customer's wireless. If wired also fails, the issue is upstream of the router. If the ONT shows LOS or no PON light, the fiber path is broken. This single test resolves the fiber-vs-WiFi question in under 60 seconds.

Why does the customer's speed test show less than their plan?

Five common causes: (1) WiFi limitations not the wired link — test wired speed first; (2) older device that cannot saturate the link; (3) speed test server selection — use multiple servers; (4) congestion at the OLT during peak hours; (5) actual provisioning issue on the OLT. Always test wired before assuming a network problem.

What if the customer keeps unplugging the ONT?

Educate them that the ONT must remain powered for service. If pets or children are reaching it, relocate the ONT to a higher or enclosed location. If the customer keeps unplugging it because of noise or appearance, ensure ventilation in the new location and walk them through what each LED means so they understand it is working.

When should I escalate a customer-side issue?

Escalate when ONT optical power is in spec but registration fails (provisioning issue), when service speed is consistently below plan despite a clean optical link (OLT or backbone congestion), or when the issue affects multiple customers on the same splitter (OSP fault). Anything that requires changes on the OLT or NMS goes to NOC.

FTTH Customer-Side Troubleshooting Workflow

The Triage Question

Before any test gear comes out, ask the customer one question: when did this start, and what changed?

Answers to listen for:

"After a power outage": ONT may need a reboot, may have failed, or backup battery may be dead
"After we moved furniture": Patch jumper or fiber damage
"After a storm": Drop cable damage or service-side outage
"It is intermittent": Marginal optical level or dirty connector
"WiFi is slow but plugged in is fast": Not a fiber issue at all
"It just stopped working": Could be anything; start a full diagnostic

The 60-Second Wired vs WiFi Split

Half of all "fiber down" tickets are actually customer-side WiFi problems. Resolve this first.

Plug a laptop or test device directly into the ONT's Ethernet port (or the router's WAN port if there is no separate ONT LAN port).
Run a speed test.
If wired performs at plan rate, the fiber link is fine. The issue is the customer's WiFi or LAN. Document and educate.
If wired performs poorly or fails, escalate to fiber-side troubleshooting.

This 60 seconds saves hours of unnecessary fiber troubleshooting on what is actually a WiFi channel congestion or router placement problem.

ONT Diagnostics

ONT LED Decode

For LED meanings see our no-signal troubleshooting guide. Quick reference:

LOS solid red: No optical signal — fiber issue
PON not registered: Optical OK but no OLT handshake — provisioning or upstream
LAN dark with PON green: Service issue above L2 — escalate to NOC

ONT Reboot

Power-cycle the ONT for 30 seconds before any deeper diagnostic. ONT firmware can hang in rare states; a reboot resolves a surprising fraction of "no service" tickets.

Optical Power Check

Disconnect the patch jumper from the ONT, connect to a PON power meter, and verify downstream power is in spec. See our ONU power level spec guide for class-by-class numbers.

Common Customer-Side Faults

Fault	Symptoms	Fix
Damaged patch jumper	LOS red, customer recently moved furniture	Replace jumper
Dirty connector	Marginal/intermittent service	Inspect and clean
Pet damage to fiber	LOS red, visible bite marks	Replace damaged section
ONT power adapter failure	All LEDs off	Swap adapter
Failed ONT	Optical OK but no LEDs activate	Replace ONT, re-provision
WiFi router issue	Wired OK, WiFi slow/dropping	Customer's responsibility (or service plan)
VoIP voice problem	Internet works, phone does not	Check ATA config, FXS port
Customer-installed splitter	Optical level dropped 3-4 dB	Remove unauthorized splitter

Patch Jumper Inspection

The fiber patch jumper between the wall outlet and ONT is the most-damaged component in a typical home. Furniture moves, vacuum cleaners, kids, pets — they all attack the jumper.

What to check:

Visible kinks or sharp bends (especially behind furniture)
Pinched at door frames, baseboards, or under heavy items
Dirty connectors at both ends
Connector boot damaged or missing strain relief

Carry replacement jumpers in common lengths and types:

Voice (ATA) Troubleshooting

Most ONTs include analog telephone (POTS) ports for VoIP voice service via an embedded ATA. When the customer reports phone but not internet trouble:

Verify ONT POTS LED is on (indicates SIP registration with the carrier).
Check that the customer's phone is plugged into the correct port (FXS 1, sometimes labeled Tel 1).
Plug a known-good corded phone (not cordless) into the ONT directly. If it works, the issue is the customer's home wiring or cordless base.
Listen for dial tone. No dial tone with POTS LED on means the SIP session is registered but the line card has a problem.

Optical Saturation (Power Too High)

On very short FTTH drops with low-loss splitters, the ONT can receive more power than its receiver can handle (above -8 dBm typically). Symptoms include intermittent service, rising FEC errors, and LOS LED behavior that does not match the troubleshoot.

Fix: insert a fixed attenuator in line at the ONT side.

Re-measure with the PON meter after adding to verify power lands in the middle of the operating range.

WiFi Issues That Look Like Fiber Issues

The most common false-positive fiber ticket is a WiFi problem. Recognize the symptoms:

Slow WiFi but fast wired: Always WiFi. Could be channel congestion, distance from AP, interference, or older client device.
Devices in some rooms but not others: WiFi coverage. Move the AP, add a mesh node, or change band.
Connection drops at random: Could be WiFi if it only happens on wireless. Test wired before assuming fiber.
Streaming buffers but speed test passes: Network capacity OK. Could be the streaming service or DNS resolution.

Most carriers do not warranty customer WiFi unless it is a managed-WiFi service plan. Document the wired-vs-wireless test result and educate the customer.

When to Escalate Beyond the Home

Escalate to OSP/OLT troubleshooting when:

Optical receive power is significantly below spec and inspection/cleaning does not resolve it
Multiple customers on the same splitter are reporting issues simultaneously
ONT registration fails despite in-spec optical power
Service speed is consistently below plan with a clean fiber link
OLT-side metrics (BER, FEC) show degradation

For OSP-side troubleshooting see our no-signal troubleshooting workflow.

Tools You Need In-Home

XGS/GPON Power Meter

$484.99 — Wavelength-selective downstream and upstream power readings.

WiFi Fiber Microscope

$1,249.99 — Inspects ONT pigtail and patch jumper connectors.

CLEP 2.5mm Cleaner

$37.99 — Cleans SC connectors at the wall outlet and ONT.

VFL Pen 5km

$104.99 — Verifies continuity from ONT back to wall outlet.

Frequently Asked Questions

How long should a customer-side troubleshooting visit take?

Most resolve in 30-60 minutes. If you are still working after 90 minutes without a clear cause, the issue is likely outside the home and needs OSP-side investigation.

What if the customer wants me to fix their WiFi?

Depends on the service plan. Managed-WiFi customers get WiFi support; basic-service customers do not. Set expectations early so the customer is not surprised by a fee or escalation.

Should I always swap the ONT?

No. Most ONT issues resolve with a power cycle or a connector cleaning. Only swap the ONT when LEDs indicate hardware failure (no power LED, no PON LED activity despite in-spec optical, or persistent FEC errors).

Customer says their speeds dropped after I left. What now?

Either an intermittent fault that did not show during your visit, or a customer-side issue that worsened (router, ISP DNS, peering). Schedule a follow-up with explicit testing of wired speed at the ONT and at the router; isolate where the slowdown occurs.

The Bottom Line

Customer-side FTTH troubleshooting is mostly diagnostic discipline: split wired from wireless, check the optical first, inspect every connector, replace damaged jumpers. The fiber link itself rarely fails inside the home — what fails is the cabling around it and the equipment plugged into it.

For the upstream side of the diagnostic see no-signal troubleshooting. For drop cable testing see how to test an FTTH drop cable.

Equip every truck with the customer-side essentials. Browse our test equipment and cables and patch cords, or get the New Hire Fiber Tech Bundle.