APON

Hello, everyone!

Today, I will explain the oldest PON technology – APON or ATM PON. This is the first PON technology, the next technology was BPON. APON and BPON are similar technology. This is the second article about a brief history of PON.

APON or ATM-PON is an abbreviation from Asynchronous Transfer Mode-based Passive Optical Network. It was the first PON standard. This technology uses multimedia multiple speed multiplexing technologies and ATM technology. APON is based on the ITU-T G.983.1 standard.

ITU-T G.983 standard defines:

• speed in downstream and upstream,

• data, voice and video control functions,

• security features,

• DBA (Dynamic Bandwidth Allocation), etc.

In the next figure, we can see the architecture of the ATM PON.

APON is composed of OLT (Optical Line Terminal), ODN (Optical Distribution Network) and ONUs (Optical Network Unit). The maximum distance between OLT and ONU is 20km and the maximum PON splits is 32.

APON supported triple services (data, voice, and video). ATM cells were used for all services. For a downstream, system with one fiber used 1550 nm for all services, and for upstream 1310nm for data and voice. If the system used two fibers, one fiber was for downstream and another fiber was for upstream. In this situation, the wavelength was 1310 nm for all services.

The maximum downstream speed was 155 Mbps or 622 Mbps, and for maximum upstream speed was 155 Mbps. Data packet cell size is 53 bytes.

The next table shows us the main features of ATM PON technology:

ATM PON offered triple services, low cost of devices, and low cost of maintaining the network. But APON was not widespread. The main disadvantage of this technology was the low bandwidth for users.

Thank you!