It is a passive network, from the central office to the user, it can basically be passive in the middle;
Its bandwidth is relatively wide, and the long-distance is just in line with the large-scale use of operators;
Because it is a service carried on optical fibre, there is no problem;
Because of its relatively wide bandwidth, the supported protocols are relatively flexible;
With the development of technology, more complete functions have been developed including point-to-point, 1.25G and FTTH methods.
In the optical access family, there is FTTB (Fiber To The Building) fiber to the building, FTTC (Fiber To The Curb) fiber to the roadside, FTTSA (Fiber To The Service Area) fiber to the service area and so on.
The optical fiber is directly connected to the user's home, and its bandwidth, wavelength, and transmission technology are not restricted, and it is suitable for introducing various new services. It is the most ideal service transparent network and the ultimate way of access network development. Although mobile communications are developing at an amazing speed, people still seek fixed terminals with relatively superior performance due to their limited bandwidth, the size of the terminal may not be too large, and the limited display screen, which means that people still want to achieve fibre-to-the-home. The charm of fiber-to-the-home is that it has a huge bandwidth, and it is the best solution to the bottleneck phenomenon of the "last mile" from the Internet backbone to the user's desktop.
With the upgrading of technology, the cost of fiber-to-the-home is greatly reduced, and it will soon be reduced to the equivalent of DSL and HFC networks, which makes FTTH practical. According to reports, Japan's NTT company began to develop FTTH as early as 1997. After 2000, the number of users increased greatly due to cost reduction; the number of FTTH installations in the United States increased by more than 200% in December around 2002.
But for the fiber-to-the-home market, companies have their own opinions: AT&T in the United States is not optimistic about FTTH. In OFC2004, the company believes that bandwidth is not a panacea, but the development of applications and content is the key. Therefore, in a considerable amount of time , The market for FTTH may be small; while US operators Verizon and Sprint are more active and introduced their plans and technical solutions for developing FTTH at OFC2004. In my country, fiber-to-the-home is also imperative, and fiber-to-the-home experimental networks have also been launched in cities such as Wuhan and Chengdu. It is expected that fiber-to-the-home will rise from the coast to the inland and from east to west in my country around 2012. The climax of construction. It can be said that fiber-to-the-home is a bright spot of fiber-optic communication. With the maturity and practicality of corresponding technologies, the cost is further reduced to a level that families can afford. The general trend of FTTH is unstoppable.
In addition, FTTH technology is still used to solve the "last mile" problem in the information superhighway. FTTH+Ethernet is better than ADSL (ADSL will establish a maximum theoretical download bandwidth of 8Mbps when dialling again. This bandwidth will never change. But in fact, due to the noise detection mechanism of ADSL, if the line condition is not good, the connection established at the beginning is obviously It is impossible to reach the theoretical value. It may be 5Mbps in the end. This bandwidth will not change.) And ISDN (the popular European telephone network form) transmission speed is much faster.
With the continuous improvement of high-speed network construction and the need to build a digital and smart life based on the "three-gigabit" network capabilities, operators need longer transmission distances, higher bandwidths, stronger reliability and lower business operations Expenses (OPEX), and GPON supports multiple functions to meet customer needs.
What is GPON?
GPON is the abbreviation of Gigabit Passive Optical Network, which is defined by the ITU-T recommendation series G.984.1 to G.984.6. GPON can transmit not only Ethernet but also ATM and TDM (PSTN, ISDN, E1 and E3) traffic. Its main feature is the use of passive splitters in the optical fiber distribution network. With a point-to-multipoint access mechanism, one incoming optical fiber can be used from the central location of the network provider to serve multiple households and small business users.
GPON, EPON and BPON
EPON (Ethernet Passive Optical Network) and GPON have very similar meanings. They are both PON networks, and both use optical cables and the same optical frequency. The rate of these two networks in the upstream direction is approximately 1.25 Gbits/s. And BPON (Broadband Passive Optical Network) and GPON are also very similar. They both use optical fibers and can provide services for 16 to 32 users. The BPON specification follows ITU-T G983.1, and GPON follows ITU-T G984.1. When PON applications began to be introduced, BPON was the most popular.
GPON is very popular in the optical fiber market. In addition to its advanced technology, it also has the following advantages:
Range: Single-mode fiber can transmit data from 10 to 20 kilometres, while conventional copper cables are usually limited to a range of 100 meters.
Speed: The downstream transmission rate of EPON is the same as its upstream rate, which is 1.25 Gbit/s, while the downstream transmission rate of GPON is 2.48 Gbit/s.
Security: Due to the isolation of signals in the optical fiber, GPON is essentially a safe system. Because they are transmitted in a closed circuit and contain encryption, GPON cannot be hacked or eavesdropped on.
Affordability: GPON optical fiber cables are cheaper than copper LAN cables, and can also avoid investment in wiring and related electronic equipment, thereby saving costs.
Energy-saving: Contrary to the standard copper wire in most networks, the energy efficiency of GPON has increased by 95%. In addition to efficiency, Gigabit passive optical networks also provide a low-cost solution that can increase users through splitters, which is very popular in densely populated areas.
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 low price, flexible protocol, and mature technology of Ethernet, and has a wide market and good compatibility. GPON is positioned in the telecommunications industry for multi-service, QoS-guaranteed full-service access, and strives to find the best, full-service, and most efficient solution. It proposes to "open and complete all protocols." To reconsider".
The technical characteristics of EPON are as follows:
Ethernet is the best carrier for carrying IP services.
Simple maintenance, easy expansion, and easy upgrade.
EPON equipment is mature and available. EPON has already laid out millions of lines in Asia. The third generation of commercial chips has 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.
The EPON protocol is simple and the implementation cost is low, and the equipment cost is low. The most suitable technology is needed in the metro access network, not the best technology.
More suitable for domestic, metropolitan area network does not have the equipment baggage of ATM or BPON.
More suitable for the future, IP bears all services, and Ethernet bears IP services.
The technical characteristics of GPON are as follows:
Access network for telecom operations;
High bandwidth: line rate, downlink 2.488Gb/s, uplink 1.244Gb/s; 3) High transmission efficiency: 94% downstream (actual bandwidth up to 2.4G) upstream 93% (actual bandwidth up to 1.1G).
Full-service support: The G.984.X standard strictly defines the support for all telecom-level services (voice, data and video);
Strong management ability: rich functions, sufficient OAM domains are reserved in the frame structure, and OMCI standards have been formulated;
High service quality: multiple QoS levels, which can strictly guarantee the bandwidth and delay requirements of the business;
Low overall cost: Long transmission distance, high splitting ratio, effective allocation of OLT costs, and lower user access costs.
What is the difference between gpon and epon？
EPON and GPON adopt different standards. It can be said that GPON is a more advanced point, which can transmit larger bandwidth and can bring 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 to transmit the code stream. The E of EPON refers to the interconnected Ethernet, so when EPON was born, it was required to be able to directly and seamlessly connect with the Internet, so the code stream of EPON follows the frame format of Ethernet. Of course, in order to adapt to the transmission on the optical fiber, a layer of frame format defined by EPON is wrapped outside the frame of the Ethernet frame format.
The EPON standard is IEEE's 802.3ah. The basic principle of the IEEE making the EPON standard is to carry out EPON standardization work within the 802.3 architecture as much as possible and to minimize the expansion of the standard Ethernet MAC protocol.
The GPON standard is the ITU-TG.984 series of standards. The formulation of the GPON standard considers the support for traditional TDM services and continues to adopt a 125ms fixed frame structure to maintain 8K timing continuity. In order to support multiple protocols such as ATM, GPON has defined a new encapsulation structure GEM: GPONEncapsulationMethod. The ATM and other protocol data can be mixed and encapsulated into frames.
In terms of application, GPON has a larger bandwidth than EPON. Its service carrying capacity is more efficient, and its optical splitting ability is stronger. It can transmit larger bandwidth services and achieve more user access. It pays more attention to multi-service and QoS guarantee, but it is more effective. Complicated, this causes its cost to be relatively high compared to EPON, but with the large-scale deployment of GPON technology, the cost difference between GPON and EPON is gradually shrinking.
EPON and GPON have their own advantages and disadvantages. GPON is superior to EPON in terms of performance indicators. However, EPON has advantages in time and cost. GPON is catching up. Looking forward to the future broadband access market, it may not be a substitute for others, but coexistence and complementarity. For customers with high bandwidth, multi-service, QoS and security requirements and ATM technology as the backbone network, GPON will be more suitable. For cost-sensitive, QoS, and low-security customer groups, EPON has become the dominant one.
Speaking of FTTH, we must first talk about fiber access. FTTH belongs to the access network part. The access network is the part from the local office or remote module to the user, which mainly completes the multiplexing and transmission functions, and generally does not include the switching function. Historically, this part was also called the local loop or subscriber loop. According to the definition of ITU-T, FTTH is the entrance of the fiber to the household. There is no copper wire between the end office and the household. The FCC in the United States defines a new meaning for the "H" in FTTH. Family, including small business establishments.
Combining the above two definitions, the FTTH definition: FTTH uses optical fiber as the transmission medium to provide end-users such as homes and small business organizations with access to the telecommunication end office, and has the function of information multiplexing/demultiplexing. There have been many FTTx in history, including FTTP (fiber to the premises), FTTB (fiber to the building), FTTC (fiber to the roadside), FTTN (fiber to the neighbourhood), FTTF (fiber to the floor), FTTZ (fiber to the cell) ), FTTO (Fiber to the Office), etc. The defined FTTH includes FTTP, FTTF, FTTO, FTTN, and other FTTx are not included.
FTTH (Fiber To The Home), as the name implies, is an optical fiber directly to the home. Specifically, FTTH refers to the installation of an optical network unit (ONU) at home users or corporate users and is the type of optical access network application closest to the user in the optical access series except for FTTD (Fiber to the Desktop). The notable technical feature of FTTH is that it not only provides greater bandwidth, but also enhances the transparency of the network to data formats, rates, wavelengths, and protocols, relaxes requirements on environmental conditions and power supply, and simplifies maintenance and installation.
EPON is an IEEE standard. EPON adopts a point-to-multipoint structure, passive optical fiber transmission mode, and provides multiple services on Ethernet. At present, IP/Ethernet applications account for more than 95% of the entire LAN communication. EPON uses the above-mentioned economical and efficient structure to become the most effective communication method for connecting the end-users of the access network. The emergence of the 10Gbps Ethernet backbone and the metro ring will also make EPON the best last-mile solution in the future all-optical network.
In an EPON, without any complicated protocol, the optical signal can be accurately transmitted to the end-user, and the data from the end-user can also be centrally transmitted to the central network. At the physical layer, EPON uses 1000BASE Ethernet PHY. At the same time, in 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 optical line terminal (OLT) Communication and real-time TDM communication. At 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 no CDMA/CD is required. Make full use of bandwidth. In addition, EPON provides QoS similar to APON/GPON by implementing 802.1p in the MAC layer.
GPON, FSAN and ITU have standardized them. Its technical feature is that it uses GFP (General Framing Procedure) defined by ITU-T to encapsulate and map multiple services such as Ethernet, TDM, and ATM at the second layer. It can provide 1.25Gbps and 2.5Gbps downstream rate, and 155M, 622M, 1.25Gbps, 2.5Gbps upstream rate, and has a strong OAM function. If you don't consider EPON, you can see that it will soon be upgraded to 10Gbps (10G Ethernet has matured). At present, GPON has advantages in terms of high speed and support for multiple services, but the complexity and cost of the technology are currently higher than EPON.
The PON system is undoubtedly one of the best. EPON and GPON, both technologies have their own merits. Whether it is EPON technology or GPON technology, its application is largely determined by the rapid reduction of optical fiber access costs and business needs, while the price is the best. The core factor.