GPON is not simply fibre from a switch to a client. A GPON deployment uses an OLT, optical distribution network, splitters and ONUs, with the optical budget and client capacity planned together.
Practical example: linking two buildings
Fibre, connector, wavelength, speed and distance must be compatible end to end.
Scenario: Two buildings need a high-speed network link and the route is longer than an ordinary copper Ethernet channel should be used for.
The installer selects the fibre type first from distance, environment and future bandwidth requirements. Compatible optical modules are then selected for the switch ports at both ends. Fibre type, wavelength, connector, transceiver speed and supported distance must all agree.
Decision: Do not buy transceivers only because they fit the SFP or SFP+ socket. The complete optical link must be compatible.
Common mistakes and selection checklist
Common mistakes
- Buying SFP or SFP+ modules simply because they physically fit the switch.
- Mixing incompatible fibre type, wavelength, connector or optical reach.
- Ignoring route conditions, bend radius, patching and future bandwidth.
What happens if you get it wrong?
The link may never establish, may be unstable, or may require replacement optics and cabling after installation. Poor route planning can also damage fibre or make maintenance difficult.
Selection checklist
- Define link speed and required distance.
- Choose single-mode or multimode fibre for the application.
- Match transceiver speed, wavelength, connector and supported reach at both ends.
- Check switch compatibility and the required patch leads or adapters.
- Plan route protection, bend radius, labelling and spare capacity.
Basic topology
A typical design is:
Router or core network → Ethernet or SFP+ uplink → OLT → feeder fibre → PLC splitter → drop fibre → ONU → customer network
OLT
The Optical Line Terminal sits at the network side of the GPON system. Your supplied Ubiquiti range includes UF-OLT and UF-OLT-4 models.
ONU
The Optical Network Unit is installed at the customer or remote endpoint. Your product range includes UF-WIFI and other Ubiquiti fibre endpoint equipment.
PLC splitters
A passive splitter divides one optical input among multiple outputs. Ubiquiti's GPON documentation gives examples of 1:4, 1:8, 1:16 and 1:32 splitters and associated insertion losses. The split ratio is not just a capacity decision. Every splitter adds optical loss, which reduces the available margin for the link.
Capacity and distance
Ubiquiti's documentation states that a UFiber OLT PON port can support up to 128 UFiber ONUs when using PLC splitters. It also documents a maximum OLT-to-ONU distance of 20 km in its example architecture, while warning that splitters, connectors, splices and other equipment reduce the practical distance because they add attenuation.
Uplink design
The OLT must also connect back into the routing and switching network. Ubiquiti's documentation shows SFP+ fibre modules or DAC cables being used for high-capacity uplinks. This means the GPON design should not be isolated from the core network design.
Optical budget must be calculated
A proper design accounts for fibre length, splitter insertion loss, connectors, splices and other losses. The objective is to keep the received optical signal within the operating range of the equipment with adequate margin.
Technical information in this article is based on current manufacturer documentation available at the time of writing. Product availability and specifications can change.
Confirm the exact product specification, supported configuration and compatibility before ordering. Platform generation, firmware, licences and optional components can change what a product supports.