Fibre optic design tools
From the physical cable to the loss budget, the full optical network and, for passive optical networks, the split ratio and the optics that have to close.
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How the design is done
A fibre link either has the loss budget to close or it does not, and the difference is usually a few tenths of a dB spread across every connector pair, every splice and every kilometre of cable. The budget itself is a single sum: the power the transmitter launches, minus every loss between the two ends, checked against what the receiver needs, with margin left for ageing and repair.
Choosing the cable is a different question. The glass inside a loose tube cable and an ADSS cable of the same count is usually the same G.652.D single mode fibre. What separates them is whether the cable can hold its own weight across a pole span, survive the trench, fit the duct already in the ground and meet the fire rating the building needs.
Passive optical networks add a splitter that can take 17 to 23 dB on its own at high split ratios, and a sizing problem on top. Subscribers per port is a cascade from splitter to ONT to access point, and bandwidth, the ONT port limit or the split ratio can each be the cap. Both the optics and the sizing have to close.
The tools below go from the physical cable to the loss budget and the full network design, then, for PON, the sizing and the optical check.
The workflow, one tool per step
Choose the cable
Filter a real manufacturer catalogue on fibre count, installation method, armour, sheath, temperature and duct clearance. Aerial ADSS spans are checked against the datasheet sag and tension table, and every cable that fails shows the reason it failed.
Fibre Optic Cable Selector FreeBuild the loss budget from the plant
Enter the fibre segments, an IEC 61753-1 connector inventory, fusion and mechanical splices and an optional ITU-T G.671 splitter, and read the total link loss against the design margin, the link ORL and a multimode reach check in one view.
Fibre Optic Connector and Splice Loss Calculator FreeDesign the optical network
Drag transmitters, spans, splitters, WDM mux, ROADMs and amplifiers onto a node graph. Every change reruns a bidirectional link budget per path with OSNR, chromatic dispersion and the ITU-T PON budget class each design satisfies, plus an OTDR trace view per node.
Fibre Optic System Designer ProSize the PON
Walk the cascade from subscriber target to ONTs, PON ports, line cards and OLT shelves for GPON, XG-PON, XGS-PON or NG-PON2, with the binding constraint named and distribution points sized separately because partly filled splitters cannot be shared between them.
PON Split Ratio Planner FreeCheck the PON optics
Run the downstream and upstream loss waterfalls against the ITU-T class budget, with G.671 splitter loss, FEC gain and the ONT receive window, and rank every standard split ratio for feasibility on the plant you have.
PON Optical Budget Calculator Free
Loss figures default to typical datasheet values. Replace them with the figures for the parts you install and confirm the link with an OTDR and a light source and power meter test.
Often used alongside
Further reading
- How to Choose a Fibre Optic Cable: ADSS, Loose Tube, and Ribbon Explained ADSS, loose tube or ribbon? How the cable types differ, when to choose single or multimode, and which one to buy for a duct pull versus an aerial span.
- What Is a Fibre Optic Loss Budget? How to Calculate Optical Power and Margin Compare the light a transmitter launches against what the receiver needs. Optical power in dBm, attenuation by wavelength, connector and splice loss budgets.
- Why Is Ethernet Limited to 100 Metres? Channel, Permanent Link and the 90 Plus 10 Rule The 100 metre limit belongs to the cabling standard, not Ethernet, and it is a loss budget. The 90 metre permanent link, the 10 metres of cords, and 10GBASE-T.