Tutorials · Fibre & GPON
How to Measure Optical Power and Check a Fibre Link Budget
Use an optical power meter and the device's DDM readings to confirm fibre links are healthy and within budget.
Before you start
- An optical power meter and light source (or DDM-capable SFPs)
- A fibre cleaning kit
Step by step
Clean every connector
Dirty connectors cause most fibre problems. Inspect and clean before measuring.
Calculate the expected loss
Fibre (≈0.35 dB/km at 1310 nm) + splitters + connectors and splices + a 3 dB margin.
Measure
Measure transmit power at the source and receive power at the far end, at the correct wavelength.
Read DDM values
On switches and OLTs with digital diagnostics, check Tx/Rx power, temperature and voltage of each optic.
show interfaces transceiverCompare to the optic's range
Receive power must sit between the optic's sensitivity and overload limits, with margin.
Commands are generic, industry-standard examples. Exact syntax and menu names vary by model and firmware; check your device's manual on the Documentation page.
Pro tips
- Record baseline readings at installation for future comparison.
- Too much power can damage receivers on short links; use attenuators if needed.
FAQ
Frequently asked questions
Why does my fibre link flap?
Usually marginal receive power from dirty or damaged connectors, tight bends or a long link beyond the optic's budget.
Stuck on a step?
Ask Navijin technical support or an authorised partner for help with your configuration.