A Comparison between GPON and EPON

A Comparison between GPON and EPON

The access layer network is a fundamental platform for the delivery and termination of various services. As subscribers to broadband access services continue to grow rapidly, there is an ever-increasing demand for broadband access bandwidth. As an ideal medium, optical fiber provides high-speed and high-bandwidth multi-service transmission. Fiber access, which offers many advantages in delivering next generation services, has become one of the key technologies of Next Generation Network (NGN). 

Fiber to the home (FTTH) is the ultimate target in the access networks. It is based on two passive optical network (PON) technologies: Ethernet PON (EPON) and gigabit PON (GPON). Fiber-based approaches promise an attractive way to deliver high bandwidth. In fact, FTTH solutions based on EPON/GPON technology are becoming more and more popular all over the world, improving end users' experience by delivering high-speed triple play services.

FTTx Deployments

Many carriers are already deploying PON FTTx network architectures to eliminate the last mile bottleneck when providing high bandwidth services to end users.

Asia is the major action point for EPON, accounting for 80% of worldwide PON subscribers. In Japan, there are more than 7 million FTTx subscribers at the end of 2006, and is projected to grow to more than 17 million by the end of 2010. By the end of 2006, EPON deployments represent about 80 percent of the worldwide FTTH market. The remaining 20 percent of the FTTH market is based on GPON, BPON, which are opted by North American carriers such as Verizon and SBC, and point to point (P2P), which is favored by France.

EPON has massive deployment while GPON, as the next leading technology, is still in its early stage of development. As fiber access is poised for strong growth, carriers can choose between the two main PON standards: EPON and GPON.

EPON vs. GPON

Technology comparison

Both are accepted as international standards. They cover the same network topology methods and FTTx applications such as FTTH/FTTB/FTTO/FTTB; incorporate the same WDM technology, delivering the same wavelength both upstream and downstream together with a third party wavelength; and provide triple-play, Internet Protocol TV (IPTV) and cable TV (CATV) video services.

There are also many differences between EPON and GPON. EPON, based on Ethernet technology, is compliant with the IEEE 802.3ah Ethernet in the First Mile standard that is now merged into the IEEE Standard 802.3-2005. It is a solution for the "first mile" optical access network. GPON, on the other hand, is an important approach to enable full service access network. Its requirements were set force by the Full Service Access Network (FASN) group, which was later adopted by ITU-T as the G.984.x standards-an addition to ITU-T recommendation, G.983, which details broadband PON (BPON).

Costs comparison

xPON, as a FTTH technology, is an ideal solution to deliver last-mile broadband access. The optical line terminal (OLT), optical network unit (ONU) and optical distribution network (ODN), which comprise a PON system, decide the costs of GPON and EPON deployments.

An ODN consists of fiber cable, cabinet, optical splitter, connector, and etc. For the same number of users, the cost for the fiber and cabinet with EPON is similar to that with GPON. The cost of OLT and ONT is decided by the ASIC and optic module. The GPON chipsets available in the market are mostly based on FPGA, which is more expensive than the EPON MAC layer ASIC. There are noly several chipset vendors who can provide GPON chipsets, and it is not likely that the price of GPON equipment can decline rapidly. The optical module of GPON is also more expensive than EPON. When GPON reaches deployment stage, the estimated cost of a GPON OLT is 1.5 to 2 times higher than an EPON OLT, and the estimated cost of a GPON ONT will be 1.2 to 1.5 times higher than an EPON ONT.

ZTE's View on GPON and EPON 

EPON is the dominant FTTH solution in Japan, Korea, China and other Asia-Pacific countries, meeting the demand for services such as high-speed Internet access, VoD, IPTV, and etc. In other countries, especially in America, GPON is the preferred choice, as BPON and ATM infrastructure is more prevalent in this area, and GPON can coexist with the legacy PON systems. That explains why EPON appears to gain an upper hand in the Asian market where BPON is not widely used.

As such, ZTE thinks that EPON and GPON will take their own shares in the growing market in the next few years, and it is hard to say which technology will replace the other in the near future.

ZTE, with its deep insight into network evolution, has launched both EPON and GPON systems. The ZTE EPON and GPON systems support high quality multicast and dynamic bandwidth allocation (DBA), and provide VoIP, IPTV, CATV SDTV, L2 VPN and TDM leased line services.

EPON and GPON may be applied in different situations, and each offers its own advantages in subscriber access networks. EPON focuses on FTTH applications while GPON focuses on full service support, including both new services and existing traditional services such as ATM and TDM. 

The ZTE xPON solution provides a uniform platform for both EPON and GPON standards, supporting EPON and GPON mixed inserts in one frame and enabling flexible networking applications.

The ZTE EPON/GPON system includes the ZXA10 C200/C220 OLT and D/F series terminals. The ZXA10 C200 features small-to-medium capacity, compact structure, high-density, high bandwidth and scalability; the ZXA10 C220 delivers medium-to-large capacity. With various kinds of ONTs, ZTE can meet the access demands of different users.

PON technologies provide the basis for advanced service delivery. With complete solutions, ZTE is well positioned to meet the high-capacity demands in different fiber broadband access markets.