Comprehensive comparison between ATM passive optical network and Passive Optical Network

Passive Optical Networks are still commonly used. So I studied the comprehensive comparison between ATM Passive Optical Networks and passive optical networks. I would like to share with you here, hoping to help you. Passive Optical Network (PON) is an attractive pure media network. Its main feature is to avoid the electromagnetic interference and lightning impact of the active devices, and reduce the failure rate of the lines and external devices, this improves system reliability, reduces maintenance costs, and economically supports analog broadcast and television services, namely, triple-play, which has three functions ).

According to Bell, the US operating company, the adoption of PON technology reduces maintenance costs by $50 per line each year, which is a long-awaited technology by the Telecommunications maintenance department. Secondly, the PON business is more transparent, in principle, it can be applied to signals of any standard and speed. Finally, because the optical transmitter and optical fiber are shared by users, the line cost is lower than that of other point-to-point communication modes. In particular, with the increasingly advanced development of optical fiber to users, its comprehensive advantages become more and more obvious. The flexible networking and economic application capabilities of PON make it the most suitable for scattered small enterprises and residential users, especially those areas where users are scattered, users in each region are concentrated in a small area and intensive user areas.

The main disadvantage of PON is the high one-time investment cost, because the local optical line terminal OLT is very expensive, and passive infrastructure such as optical fiber and shard must be in place once again, in this way, when the number of users is small or the user distribution exceeds a certain distance, the cost of a single user is very high. In addition, the tree branch topology does not enable users with protection functions or the cost of protection functions is high, which affects large-scale development. Early narrowband PON was based on TDM, and its performance was lower than the price. ATM-based Passive Optical Network/Broadband Passive Optical Network APON/BPON can use the centralized and Statistical Multiplexing functions of ATM, and then share the functions of passive splitter on optical fiber and optical line terminals, the cost-performance ratio has been greatly improved. At present, it has been commercially available in the United States and Japan, and approximately 0.5 million lines have been laid in Japan.

However, the current business adaptation of APON/BPON is very complex, with limited service provision capabilities, low data transmission rate and efficiency, and high costs, its market prospects become uncertain due to the decline of ATM. According to the long-term business development trend, the available bandwidth of APON is still insufficient. Taking FTTC as an example, although the downstream speed of a typical trunk can reach 622 Mbit/s, the bandwidth actually allocated to each user will be greatly reduced after the routing. Based on 32-channel computing, the available bandwidth of each branch is only 19.5 Mbit/s, and then 10 users share the bandwidth, each user can only be divided into about 2 Mbit/s. Obviously, such performance prices cannot meet the long-term development needs of networks and businesses.

Ethernet Passive Optical Network/Gigabit Ethernet Passive Optical Network

In recent years, with the rise and development of IP addresses, some people have proposed the concept of Ethernet Passive Optical Network (EPON), that is, based on the structure similar to APON and BPON and G.983, try to retain the essence of the physical layer PON, and use Ethernet instead of ATM as the link layer protocol to form a new combination that provides greater bandwidth, lower cost, and wider business capabilities-EPON. This idea has received a positive response in the Ethernet industry. Under the IEEE 802.3 banner, the initial standard Gigabit Ethernet Passive Optical Network (GEPON) has been formed ). In practice, the basic difference between EPON and GEPON is standardization. The former usually refers to non-standard devices, and the latter refers to devices that comply with IEEE 802.3ah specifications. In addition, the transmission distance and path ratio of GEPON are reduced compared with that of EPON. According to the structure of EPON/GEPON, its key advantage is that it greatly simplifies the traditional multi-layer overlapping network structure and has the following main features:

◆ The ATM and SDH layers are eliminated to reduce the initial and operation costs;
◆ The downstream service speed is as high as 1 Gbit/s, and more users are allowed. The bandwidth per user can be higher, and video service capabilities and better QoS can be provided;
◆ Simple hardware, no need for external electronic equipment, simplifies installation and deployment;
◆ Improved the flexible configuration of the circuit and the ability to provide and reconfigure services.

The GEPON Technology of IEEE 802.3ah specification is well-regulated. The uplink and downlink wavelengths are 1 310 nm and 1 490 nm, the uplink and downlink speeds are 1.25 Gbit/s, and the transmission distance is 10/20 km, the division ratio is 16, and the main business is data and voice. After adding a 1 550 nm television broadcasting wavelength, it provides the so-called "triple-play" broadband service bundle service that combines voice, data, and television. This will be the "killer application" of future household businesses ".

The main disadvantage of EPON/GEPON is its low efficiency and difficulty in supporting services other than Ethernet. The former adopts 8B/10B line encoding, resulting in 20% bandwidth loss, while APON and GPON both adopt non-return NRZ) scrambling codes as line codes, so there is no bandwidth loss. In addition, the bearer layer, transfer aggregation layer, and service adaptation efficiency make the overall transmission efficiency of EPON very low, which is about half of the GPON of gigabit passive optical networks.