PON overview

A Passive Optical Network (PON) delivers fibre from a provider to many subscribers using only passive splitters in between — no powered equipment in the field.

The parts

• OLT (Optical Line Terminal) — the provider-side device at the central office.
• ONU/ONT (Optical Network Unit/Terminal) — the device at the subscriber.
• Splitter — a passive optical splitter fans one fibre out to many subscribers

(for example 1:32 or 1:64).

One fibre, both directions

A single fibre carries traffic both ways using different wavelengths, so downstream and upstream do not collide. Downstream is broadcast to all ONUs and encrypted per subscriber; upstream is time-shared (TDMA), with the OLT granting each ONU its slot.

Transceivers

PON optics are specialised: the OLT and ONU modules use a diplexer to separate the two wavelengths on one fibre. They appear as PON SFP "sticks". The exact wavelength plan depends on the PON standard.

CodingBox reads the identity and wavelength fields of a PON module just as it does for other transceivers.