Ethernet technology for LAN is the core of the EPON. EPON is a common solution in Asia, due to its low-cost equipment and compatibility with existing installations. Simple installation makes it first option for densely populated areas. EPON has flexible framing starting with 125 ns and large address space, which is advantageous compared with GPON.
GPON technology inherits broadband access feature from BPON. Usage of GEM allows GPON improve efficiency with the use of flexible services. GPON technology provides compatibility with ATM technology and transmission rate enhancement.
Main features of EPON and GPON are shown in Table 1.
Table 1. EPON and GPON feature comparison.
|Features||EPON technology||GPON technology|
|Standard||IEEE 802.3ah-2004||ITU-T G.984.x|
|Line rate||1.25 Gbps symmetric||Max 2.448 Gbps symmetric|
|Revenue BW*||900 Mbps||2300 Mbps|
|Upstream wavelength||1210 nm||1310 nm|
|Downstream wavelength||1490 nm||1490 and 1550 nm （optional)|
|Data unit||Ethernet frame||GEM frame, ATM cell|
|Split ratio||1:16, 1:32, 1:64 (with FEC)||1:64 (or possibly 1:132)|
|Max distance||20 Km||20 km|
|TDM support||Ethernet frame encapsulation||Directly|
|QoS support||802.1Q priority levels||Fixed, assured, nonassured, best effort|
|Address space||48 bits||8 bits|
|Class of service||8 queues||5 T-COMT types|
|Security||Not specified||AES encryption|
|Protection||Not specified||Four specified architectures|
EPON can provide weak error correction compared to the GPON. Meanwhile GPON use CRC codes for error correction, and implement protection switching, and encryption. Both systems are flexible depending on QoS, data rate, and price requirements. For the greater size networks GPON has advantage of higher split ratio and bandwidth efficiency, but from a price view – EPON is definitely better, and outweights these differences in technique and is preferable choice at the time of writing.
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