Check a GPON, XG-PON, XGS-PON or NG-PON2 link in both directions against the ITU-T class tables, with overload checks at both ends, optical reach and splitter ratio feasibility.
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Walkthrough
Downstream and upstream loss breakdowns.
Overview
A passive optical network only works if every ONT on a PON port receives enough power after the splitter, fibre, connectors and splices have taken their share, and not so much that a receiver close to the OLT overloads. Each ITU-T class sets a maximum and a minimum loss, and the margin you actually have is smaller once the optical path penalty, and any reserve you keep for ageing, repair and temperature, are set aside. A large splitter alone can use most of what is left.
The calculator works out the downstream (OLT to ONT) and upstream (ONT to OLT) loss for GPON, XG-PON, XGS-PON and NG-PON2, using the wavelengths of the selected standard. Each direction is shown as a step by step breakdown from transmit power to received power, with the margin after the optical path penalty and any reserve, and overload checks at both ends. Splitter loss is the ITU-T G.671 maximum insertion loss, and an FEC gain is applied only when you type one for a class whose sensitivity does not already assume FEC.
The maximum reach is the tighter of the power budget and the class maximum loss in the worse direction, and never more than the maximum fibre distance of the class. A feasibility table runs every splitter ratio against the current fibre plant, so you can see which ratios it supports. The PON standard and splitter ratio are shared with the PON Split Ratio Planner, so the optical and capacity views of a design stay in step.
Both directions are broken down from transmit power through splitter, fibre, connector and splice loss to the received power. Each receiver is checked against its sensitivity, after the optical path penalty and any reserve, and against its overload limit, and the worse of the two margins is shown up front.
Choose the budget class for the selected standard, from the GPON classes of ITU-T G.984.2 to the N and E classes of G.987.2, G.9807.1 and G.989.2 and the XGS-PON B+ and C+ classes. Each class fills in its minimum and maximum loss, transceiver limits and optical path penalty from the ITU-T tables.
Splitter loss is the ITU-T G.671 maximum insertion loss, and a manufacturer value is typed for 1:128, which G.671 does not cover. Fibre attenuation defaults to the ITU-T G.652.D cable maximum for each band, and connectors and splices to the TIA-568.3-E maxima, all editable with measured or manufacturer values.
ITU-T G Suppl. 39 asks for a margin for ageing, repairs and temperature but gives no value, so the reserve and the marginal threshold are optional and blank by default. ITU-T G.984.2 gives no FEC gain value, so the gain is typed, blank by default, and never added to classes whose sensitivities already assume FEC.
The ONT received power is shown between its sensitivity and overload limits. This helps with long drops at the edge of the budget and with short drops near the OLT that risk overloading the ONT. The OLT receiver is checked for overload too.
Maximum reach is the tighter of the power budget and the class maximum loss after splitter and passive losses, in the worse direction, and stops at the maximum fibre distance of the class. A span beyond that distance fails, because the standard gives no path penalty past it.
A table runs every splitter ratio through the same checks and shows the worst margin and result for each. The PON standard and splitter ratio are shared with the PON Split Ratio Planner, and the results copy to the clipboard as a text summary.
Inputs and outputs
Inputs 10
Outputs 10
Use cases
GPON to ITU-T G.984.2 with Classes A, B, B+, C and C+; XG-PON to G.987.2 with N1, N2a, N2b, E1, E2a and E2b; XGS-PON to G.9807.1 with N1 to E2 and the optional wavelength set B+ and C+; and NG-PON2 to G.989.2 with N1 to E2. Choosing a standard sets its wavelength bands and the ITU-T G.652.D cable maximum attenuation, and the class list follows the standard.
Each direction starts from the minimum transmit power and subtracts splitter, fibre, connector and splice loss to give the received power. The margin is the received power less the receiver sensitivity, the class optical path penalty and any reserve you enter. Each receiver is also checked for overload in the worst case: maximum transmit power, the splitter at its G.671 minimum loss, and fibre, connectors and splices at 0 dB because no standard gives them a minimum. A result that only the worst case fails is flagged for measurement or an attenuator.
The class maximum loss comes from the ITU-T table for the selected class. The effective budget is that maximum less any ageing, repair and temperature reserve you enter (none by default, as no standard gives a value). The path must also stay above the class minimum loss, or attenuation is needed.
Splitter loss is the ITU-T G.671 maximum insertion loss for each ratio up to 1:64, and the minimum loss and overload checks use the G.671 minimum in the worst case. G.671 has no 1:128 value, so that ratio is not assessed until you type the manufacturer's figure.
ITU-T G.984.2 defines the FEC gain but gives no value, so the gain is typed and blank by default. It relaxes the receiver sensitivity in the direction you set and never changes the overload limit. Class C+ and the XG-PON, XGS-PON and NG-PON2 classes already assume FEC, so no extra gain is added to them.
Each class has a maximum fibre distance (20 km for GPON A, B, B+ and C, 60 km for C+, 40 km for the XG-PON, XGS-PON and NG-PON2 classes). A span beyond it fails, because the standard gives no optical path penalty past that distance, and the reported reach stops there. Beyond 20 km the larger DD40 path penalty is applied where the standard gives one.
The PON standard and splitter ratio are shared between the two tools in your browser, so a change in one is picked up by the other. If the planner changes them in another tab, the calculator offers to adopt the new values, and it shows the planner's subscriber and ONT counts for context.
No. The calculations run in your browser, and your settings are kept in your browser's local storage between visits. Nothing you enter is sent to a server.
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