Application of EPON Technology in FTTx Access Network

The EPON-based FTTx technology has the advantages of high bandwidth, high reliability, low maintenance cost, and mature technology. Secondly, it introduces the typical application model of EPON in FTTx, and then analyzes the key aspects of EPON technology in the application and analyzes EPON. The advantages are analyzed. The three key issues of OLT equipment network positioning, voice service networking mode, and integrated network management architecture in the EPON-based FTTx access network are analyzed.

1、EPON application scenario analysis

EPON technology is currently the main implementation of broadband optical access and FTTx. Considering the characteristics of EPON technology, maturity, investment cost, business requirements, market competition and other factors, the main applications of EPON technology can be divided into the following types:

FTTH (Fiber to the Home), FTTD (Fiber to the Desktop), FTTB (Fiber to the Building), FTTN/V, etc. The four modes are mainly manifested in the difference in the position of the end of the optical cable, the length of the access copper cable, and the range of users covered by a single node, Determine the position of the fiber access point and ONU in the X in FTTx. Through the deployment of various FTTx to achieve optical fiber, the ultimate goal of FTTH to promote optical fiber to the home, FTTB/FTTN is the more economical deployment mode at this stage.

EPON takes Ethernet as the carrier, adopts point to multipoint structure and passive optical fiber transmission mode. The downlink rate can reach 10Gbit / s at present, and the uplink sends data stream in the form of burst Ethernet packets. At present, EPON Technology has been widely used in all kinds of “optical in copper out” construction mode of operators. From the perspective of long-term FTTx network evolution, the appearance of 10G EPON Technology also provides a better solution for operators’ FTTx network smooth upgrading.

FTTx uses optical fiber as the transmission medium, which has the advantages of large transmission capacity, high quality, high reliability, long transmission distance, and anti-electromagnetic interference. It is the development direction of broadband access.

(1) FTTH method

FTTH, or fiber-to-the-home method, is suitable for areas where users live relatively scattered, such as villas, where users have higher requirements for bandwidth, and developers are actively involved in network construction.FTTH realizes “all optical access, no copper in the whole process”. One node corresponds to one user. The user obtains the strongest bandwidth and business capabilities, but the construction cost is also high.

(2) FTTD method

The FTTD method is suitable for scenarios where high-end office buildings and other users are concentrated and require high bandwidth, and it is also suitable for scenarios where high-bandwidth services such as IPTV are developed in dense residential areas. The general networking method is to pull out the optical cable from the OLT at the central office to the building, place an optical splitter in the handover room or corridor of the building, and connect it to the user’s desktop through the building’s optical cable or drop cable.In this case, it is necessary to choose whether to place the optical splitter in the corridor or in the handover room of the building according to the intensity of users. At the same time, considering the convenience of installation, cold connection technology should be used as much as possible when installing ONU on the user side.

(3) FTTB method

The FTTB method is suitable for scenarios where the relative number of users in a single business building is small and the bandwidth requirements are not high. FTTB realizes “fiber to the building, copper does not leave the building”.The operator’s optical cable extends to the building, and the access node is deployed in the corridor. Through this node, the business needs of all users in the building are covered, and the user access bandwidth and business capabilities remain Very high, it is the mainstream solution for newly built communities;

(4) FTTN/V method

FTTN/V is basically “fiber to the community (village), copper can not leave the community (village)”, the operator deploys the fiber optic cable in the community (village), and installs a small number or even only nodes in the computer room or outdoor cabinet of the community (village) ,To achieve business coverage for users in the entire community (village), and its access bandwidth and business capabilities are relatively weak. It is the mainstream solution for urban reconstruction and rural “optical copper retreat”.

Different networking modes directly affect the construction of ODN and the settings of PON system network elements. The appropriate networking mode should be selected according to actual needs. The FTTx network platform shared by various customers and various FTTx networking application modes can be set up in different regions.

2、Problem analysis of EPON in application

2.1 The main points of EPON in project planning

   EPON mainly considers 4 elements in project planning: optical cable network planning, OLT installation location, optical splitter installation location, and ONU type.

The layout plan of the optical cable, the way of entering the home, and the choice of optical cable/fiber are the most critical issues in the EPON networking process, which will directly affect the overall investment, optical cable utilization,equipment utilization and pipeline utilization. The use of PON technology puts high demands on the current user optical cable network networking mode, especially in the layout of user optical cables within the cell. If a fiber optic cable is separately deployed for each user, a large number of fiber optic cables are required in the cell, which will consume a large amount of pipeline resources in the cell, resulting in an increase in the cost per user. Therefore, it is necessary to do a good job in the planning of the user optical cable network in the early stage of construction, including the backbone optical cable routing, core number, etc., to avoid waste of resources as much as possible.

The placement of the OLT and splitter will greatly affect the layout and investment cost of the optical cable network. For example, OLT deployment at the central office will occupy part of the backbone optical cable, and deployment in the community is restricted by office room resources and supporting costs.In the early stage of development, it is recommended to deploy the OLT at the central office. When selecting the location of each device, the distribution of users in the cell and the bandwidth requirements of different users should be considered at the same time, and the dense user group and the dispersed user group should be treated separately.

The type of ONU should be selected in conjunction with the cable layout in the access area. ONUs mainly include POS+DSL and POS+LAN. For example, when the building wiring in the community only has twisted pair, the ONU will use POS+DSL, voice Access through softswitch, broadband access by ADSL/VDSL; when building wiring in the community adopts Category 5 wiring, ONU will use POS+LAN equipment, and for office buildings, units, and parks with integrated wiring, ONUs will use Equipment with LAN interface.

In engineering design, the maximum attenuation value in ODN must be controlled, and it is recommended to control it within 26dB.

2.2 Features of EPON in FTTX networking

Compared with traditional access technologies, the increasingly mature FTTx technology based on EPON has the following advantages:

(1) The technology is simple, the cost is low, and IP services can be transmitted efficiently, which is conducive to the flexible and rapid deployment of services. EPON is simple to construct. ODN is deployed in the building, and ONUs are deployed on the user side to provide various services. The construction period is short and service deployment is convenient and flexible.

(2) In the system, there is no need to set up traditional active devices between the central office and the user premises, saving the construction of the computer room. ODN is a passive device. It is easier to find the construction location of the ODN in the building, which reduces the cost of construction, lease and maintenance of the computer room.

(3) The network is economical and saves network construction costs. The FTTx network adopts a point-to-multipoint structure, which saves a lot of user backbone fiber resources. A high-speed fiber can serve multiple users at the same time, which significantly improves the return on investment in network construction.

(4) Easy to maintain and manage. There is an EPON unified network management at the central office, which can manage the user-side ONU, which is easier to manage and maintain than HDSL modem or optical modem.

3、Conclusion

In short, operators are facing increasingly severe forms of competition. In the field of access networks, only when operators choose the correct access method can they fully guarantee the interests of the operators and meet the ever-changing business needs.The EPON system is a new access technology facing the future. The EPON system is a multi-service platform and is a good choice for the transition to an all-IP network. EPON can provide high-speed, reliable, multi-service and manageable access services at a relatively low cost, which is a full manifestation and guarantee of value for access users and operators.