An Introduction To The Difference Between GPON And EPON

⦁ Background

At present, the PON (Passive Optical Network) has become the mainstream technical solution for access networks.

The service topology of a PON system is shown below:

Figure 1 PON Service Topology Diagram

As shown above:

⦁ OLT (Optical Line Terminal): The terminal equipment connected to the optical fiber trunk line.

⦁ Splitter: A passive optical splitter that supports splitting ratios of 1:16, 1:32, 1:64, or up to 1:128.

⦁ ONU (Optical Network Unit): Customer-premises equipment that passively receives data sent from the OLT and provides user-side services.

Currently, GPON and EPON are the two mainstream PON solutions. This article briefly explains their differences and connections.

⦁ Difference in Supported Protocols

EPON stands for Ethernet Passive Optical Network.

It is standardized by the IEEE (Institute of Electrical and Electronics Engineers) and fully follows Ethernet protocol specifications.

GPON stands for Gigabit Passive Optical Network.

It is defined and led by the ITU (International Telecommunication Union) and FSAN (Full Service Access Network), both of which focus on carrier-grade technical standards.

Due to their standardization bodies, carriers typically prefer GPON as their optical access technology, while EPON is more closely aligned with traditional Ethernet networks.

Table 1 Protocols Supported by EPON and GPON

ONU Type	Protocol Standard	Remarks
EPON	IEEE 8002.3ah	Based on Ethernet protocol
GPON	ITU-T G.984.x series	Including ITU-T G.984.1/2/3/4 Total 4 protocols

⦁ Difference in Operating Rates

EPON uses fixed symmetric upstream and downstream rates, while GPON supports multiple asynchronous transmission rates.

Table 2 Rate Differences Between EPON and GPON

ONU Type	Uplink Rate	Downstream Rate	Remarks
EPON	1.25Gbps	1.25Gbps	Fixed symmetric rate
GPON	0.155Gbps	1.244Gbps	Supports multiple asymmetric rates; The mainstream mode is 1.244 Gbps upstream & 2.488 Gbps downstream
	0.622Gbps	1.244Gbps
	1.244Gbps	1.244Gbps
	0.155Gbps	2.488Gbps
	0.622Gbps	2.488Gbps
	1.244Gbps	2.488Gbps
	2.488Gbps	2.488Gbps

⦁ Difference in Split Ratio

The split ratio refers to the number of ONUs that can be connected to a single OLT port.

Benefiting from its higher downstream bandwidth, GPON supports larger splitting ratios.

⦁ EPON: Typically 1:16 ~ 1:32

⦁ GPON: Typically 1:64 ~ 1:128

In short, GPON can accommodate far more end users than EPON.

⦁ Summary

As important solutions for access networks, GPON and EPON each have their own advantages.

Compared with EPON, GPON provides higher downstream bandwidth, stronger splitting capability, more flexible rate allocation, and can support more users and higher-bandwidth services.

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An Introduction To The Difference Between GPON And EPON