Introduction to EPON and GPON

What is EPON

EPON is an IEEE standard. EPON adopts a point-to-multipoint structure and passive optical fiber transmission mode to provide a variety of services on Ethernet. At present, IP/Ethernet applications account for more than 95% of the entire local area network communication. EPON has become the most effective communication method for connecting end users of the access network due to the use of the above-mentioned economical and efficient structure. The emergence of a 10Gbps Ethernet backbone and metropolitan area ring will also make EPON the best last-mile solution in the future all-optical network.

In an EPON, the optical signal can be accurately transmitted to the end user without any complicated protocol, and the data from the end user can also be transmitted to the central network centrally. At the physical layer, EPON uses 1000BASE Ethernet PHY, and on the PON transmission mechanism, the newly added MAC control commands are used to control and optimize the burst data between each optical network unit (ONU) and the optical line terminal (OLT). Communication and real-time TDM communication, in the second layer of the protocol, EPON adopts mature full-duplex Ethernet technology and uses TDM. Since the ONU sends datagrams in its own time slot, there is no collision, and CDMA/CD is not required. Make the most of your bandwidth. In addition, EPON provides QoS similar to APON/GPON by implementing 802.1p in the MAC layer.

What is GPON

It is standardized by GPON, FSAN, and ITU. Its technical feature is that GFP (General Framing Procedure) defined by ITU-T is used at the second layer to encapsulate and map various services such as Ethernet, TDM, ATM, etc., which can provide 1.25Gbps and 2.5Gbps downlink rates, and 155M, 622M, 1.25Gbps, 2.5Gbps uplink rate, and has strong OAM function. If EPON is not considered, it can be seen that the rate will soon be increased to 10Gbps (10G Ethernet has matured). Currently, GPON has advantages in terms of high rate and multi-service support, but the technical complexity and cost are currently higher than EPON.

The PON system is undoubtedly the best among them. EPON and GPON have their own advantages and disadvantages. Whether it is EPON technology or GPON technology, its application is largely determined by the rapid reduction of fiber access costs and business needs, while the price is the most. core factor.

Comparison of EPON and GPON

EPON aims to be compatible with the current Ethernet technology. It is the continuation of the 802.3 protocol in the optical access network. It fully inherits the advantages of Ethernet in low price, flexible protocol, and mature technology. It has a wide market and good compatibility. GPON, on the other hand, is positioned in the telecom industry for multi-service, QoS-guaranteed, full-service access, and strives to find the best, full-service, and most efficient solution. reconsider.”

The technical characteristics of EPON are as follows:

1) Ethernet is the best carrier for carrying IP services;

2) Simple maintenance, easy to expand, easy to upgrade;

3) EPON equipment is mature and available, millions of EPON lines have been laid in Asia, and the third-generation commercial chips have been launched. The prices of related optical modules and chips have dropped significantly, reaching the level of large-scale commercial use, which can meet the requirements of recent broadband services. ;

4) The EPON protocol is simple and the implementation cost is low, the equipment cost is low, and the most suitable technology is needed in the metro access network, not the best technology;

5) It is more suitable for domestic, the metropolitan area network does not have the equipment burden of ATM or BPON;

6) More suitable for the future, IP bears all services, and Ethernet bears IP services.

The technical characteristics of GPON are as follows:

1) Access network for telecom operation;

2) High bandwidth: line rate, downlink 2.488Gb/s, uplink 1.244Gb/s; 3) High transmission efficiency: downlink 94% (actual bandwidth up to 2.4G) uplink 93% (actual bandwidth up to 1.1G);

4) Full-service support: The G.984.X standard strictly defines the support of carrier-class full services (voice, data, and video);

5) Strong management ability: with rich functions, sufficient OAM domain is reserved in the frame structure, and the OMCI standard has been formulated;

6) High service quality: a variety of QoS levels, which can strictly guarantee the bandwidth and delay requirements of the business;

7) Low overall cost: long transmission distance and high splitting ratio, effectively allocating OLT costs and reducing user access costs.

What is the difference between fiber modem GPON and EPON

1. The standards adopted by EPON and GPON are different. It can be said that GPON is more advanced, can transmit larger bandwidth, and can carry more users than EPON. GPON originated from the early APON\BPON technology of optical fiber communication and developed from this, the ATM frame format is used for the transmission code stream. E of EPON refers to interconnected Ethernet, so at the beginning of EPON’s birth, it was required to be able to directly and seamlessly connect with the Internet, so the code stream of EPON is in the frame format of Ethernet. Of course, in order to adapt to the transmission on the optical fiber, the frame format defined by a layer of EPON is wrapped outside the frame of the Ethernet frame format.

2. The standard of EPON is IEEE’s 802.3ah. The basic principle of IEEE to formulate the EPON standard is to carry out the standardization of EPON within the 802.3 architecture as much as possible and to expand the MAC protocol of the standard Ethernet to the minimum extent.

3. The standard of GPON is the ITU-TG.984 series of standards. The formulation of the GPON standard takes into account the support for traditional TDM services and continues to use a 125ms fixed frame structure to maintain 8K timing continuation. In order to support ATM and other multi-protocols, GPON defines a new encapsulation structure GEM: GPON Encapsulation Method. The data of ATM and other protocols can be mixed and encapsulated into frames.

4. In terms of application, GPON has a larger bandwidth than EPON, its service bearing is more efficient, its optical splitting ability is stronger, it can transmit larger bandwidth services, realize more user access, pay more attention to multi-service and QoS guarantee, but realize more Complex, which leads to its higher cost than EPON, but with the large-scale deployment of GPON technology, the cost difference between GPON and EPON is gradually narrowing.

5. Comparison of GPON and EPON protocol stacks

1) The standards adopted by EPON and GPON are different. It can be said that GPON is more advanced, can transmit larger bandwidth, and can carry more users than EPON. GPON originated from the early APON\BPON technology of optical fiber communication and developed from this, the ATM frame format is used for the transmission code stream. E of EPON refers to interconnected Ethernet, so at the beginning of EPON’s birth, it was required to be able to directly and seamlessly connect with the Internet, so the code stream of EPON is in the frame format of Ethernet. Of course, in order to adapt to the transmission on the optical fiber, the frame format defined by a layer of EPON is wrapped outside the frame of the Ethernet frame format.
2) The standard of EPON is IEEE’s 802.3ah. The basic principle of IEEE to formulate the EPON standard is to carry out the standardization of EPON within the 802.3 architecture as much as possible and to expand the MAC protocol of the standard Ethernet to the minimum extent.
3) The standard of GPON is the ITU-TG.984 series of standards. The formulation of the GPON standard takes into account the support for traditional TDM services and continues to use a 125ms fixed frame structure to maintain 8K timing continuation. In order to support ATM and other multi-protocols, GPON defines a new encapsulation structure GEM: GPON Encapsulation Method. The data of ATM and other protocols can be mixed and encapsulated into frames.
4) In terms of application, GPON has a larger bandwidth than EPON, its service bearing is more efficient, its optical splitting ability is stronger, it can transmit larger bandwidth services, realize more user access, pay more attention to multi-service and QoS guarantee, but realize more Complex, which leads to its higher cost than EPON, but with the large-scale deployment of GPON technology, the cost difference between GPON and EPON is gradually narrowing.
5) Comparison of GPON and EPON protocol stacks

EPON and GPON have their own strengths and weaknesses. GPON is better than EPON in terms of performance indicators, but EPON has advantages in terms of time and cost, and GPON is catching up. Looking forward to the future broadband access market, it may not be one that replaces the other but should coexist and complement each other. For bandwidth, multi-service, high QoS and security requirements, and ATM technology as the backbone network customers, GPON will be more suitable. For the customer group that is cost-sensitive, QoS, and security requirements are not high, EPON has become dominant.