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PON MAINTENANCE TOOL

ONU RX Power Diagnosis Tool

Use measured ONU receive power, receiver sensitivity and overload limits to diagnose normal, weak-light, critical low-power, overload or possible no-signal conditions. Link-model mode also compares expected and measured power to estimate excess loss.

Weak-light diagnosisOverload detectionExcess lossMaintenance guidance
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Measured and equipment parameters

Build a link model and compare expected versus measured receive power.

Measured power and receiver window
dBm
dBm
dBm
dB
dBm

The following parameters build the theoretical link model. Presets are editable references; final analysis should use actual equipment and field data.

dBm
km
dB/km
pcs
dB
pcs
dB
dB
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Diagnosis result

Checks sensitivity limit, overload limit and measured deviation.

Measured receive power

0.00dBm
✓ Normal
↓
Sensitivity margin0.00 dB
↑
Overload safety margin0.00 dB
↕
Receiver window0.00 dB
PON
Total split ratio1:16
Receive power position-18.00 dBm
Possible no signalCritical weak lightNormal rangeOverload
Expected receive power0.00 dBm
Measured versus expected deviation0.00 dB
Inferred excess loss0.00 dB
Modeled physical loss0.00 dB

Modeled loss breakdown

Fiber loss0.00 dB
Splice loss0.00 dB
Connector loss0.00 dB
Splitter loss0.00 dB
Engineering conclusion

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    METHODOLOGY

    Methodology and engineering notes

    Sensitivity margin

    Measured receive power minus receiver sensitivity. Smaller margin makes the link more vulnerable to contamination, bending, ageing and temperature variation.

    Overload safety margin

    Receiver overload threshold minus measured receive power. A negative result indicates excessive receive power.

    Expected receive power

    Minimum OLT transmit power minus modeled physical loss. It is compared with the measured value and does not deduct a design reserve as physical loss.

    Inferred excess loss

    When measured power is below the modeled value, the difference estimates unaccounted or abnormal loss.

    Important: Receiver sensitivity, overload threshold and transmit power must come from the actual equipment specification. This tool supports planning, verification and troubleshooting; it does not replace power-meter or OTDR testing and formal acceptance.

    FAQ

    Frequently asked questions

    What ONU receive power is considered normal?

    There is no universal fixed value. Use the sensitivity and overload limits of the specific ONU or optical module and retain suitable engineering margin.

    Should a link close to sensitivity be maintained even when service works?

    Yes. Treat it as a weak-light risk because minor contamination, bending or temperature variation may push the link below the receiver threshold.

    What does a large difference between measured and expected power indicate?

    Possible causes include unmodeled connector loss, dirty interfaces, patch-cord bending, poor splices, splitter faults or increased route attenuation.

    What problems can excessive receive power cause?

    It may saturate the receiver and cause errors, registration problems or unstable service. Verify optical class compatibility and whether attenuation is required.

    Does possible no signal always mean a fiber break?

    No. It may also result from a disconnected patch cord, incorrect port mapping, an inactive OLT laser, splitter failure or severe bending.

    Why are all preset values editable?

    Vendors, optical classes and network designs differ. Presets are demonstrations only; production diagnosis must use real equipment and field data.

    SOURCES & REVIEW

    Engineering references and scope

    Reviewed: 2026-08-31. Receiver sensitivity, overload and transmit-power limits depend on the exact optical class and equipment implementation. The default 3 dB caution margin is a NetEngineerLab planning threshold, not a universal standards mandate. Splitter insertion values are planning inputs; verify the installed component specification and field measurements.

    PROJECT RECORDS

    Recent diagnosis records

    ENGINEERING WORKFLOW

    Continue the engineering workflow

    Current workflowOptical Fault Isolation Workflow

    Start from measured ONU receive power, locate abnormal events, then compare field loss with the design budget.

    Step 1 of 4
    PreviousWorkflow start
    NextOTDR Event AnalyzerAnalyze multiple events and dual wavelengths to identify splices, connectors, bends, breaks, ghosts and dead-zone effects.

    Related tools

    Optical Power Budget CalculatorVerify an optical link using transmit power, receiver sensitivity, optical penalty and ODN loss.OTDR Event AnalyzerAnalyze multiple events and dual wavelengths to identify splices, connectors, bends, breaks, ghosts and dead-zone effects.Fiber Loss CalculatorCalculate fiber, splice, connector, splitter and engineering losses for an optical link.