This article explores the various types of PON (Passive Optical Networks), how they differ and what they are used for.
This was the very first of the PON standards and was based on ATM (Asynchronous Transfer Mode). ATM is a switching technique used by telecommunication networks that uses asynchronous time-division multiplexing to encode data into small, fixed-sized cells. This is different from Ethernet or internet, which use variable packet sizes for data or frames.
It was used for business applications.
BPON is a standard based on APON. It adds support for WDM (Wavelength Division Multiplexing), dynamic and higher upstream bandwidth allocation, and survivability. It also created a standard management interface, called OMCI, between the OLT and ONU/ONT, enabling mixed-vendor networks.
BPON is generally offered at 622 Mbps downstream and 155 Mbps upstream. However, its ATM structure and bandwidth limits make it less than ideal for video which has led to development being stopped. Instead, BPON networks will be converted to EPON or GPON over time.
EPON is a rival activity to GPON, which uses Ethernet packets instead of ATM cells.
Ethernet PON employs a single Layer 2 network that uses Internet Protocol (IP) to carry data, voice, and video. It generally delivers 1 Gbit/s symmetrical bandwidth, making it very popular in modern networks.
GEPON is still evolving; but, it requires the multiple protocols through translation to support the native Generic Encapsulation Method (GEM) transport layer. This emulation supports ATM, Ethernet and WDM protocols. It is widely deployed in Asia and uses Ethernet as its native protocol and simplifies timing and lowers the costs by using symmetrical 2.5 Gbps data streams. The complexity is lower and cost is less than GPON.
GPON provides three Layer 2 networks: ATM for voice, Ethernet for data and proprietary encapsulation for voice. It offers 1.25 Gbit/s or 2.5 Gbit/s downstream and upstream bandwidths scalable from 155 Mbit/s to 2.5 Gbit/s.
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