FTTH optical network technology and application
1. Overview of FTTH optical network
An optical access network (OAN) refers to a network form in which an optical fiber is used as a primary transmission medium in an access network to implement information transmission. OAN can be divided into passive optical network (PON) and active optical network (AON).
FTTH refers to the extension of ONUs (Optical Network Units) to ordinary residential users. With the continuous development of FTTH, FTTH can not only provide huge access bandwidth, but also integrate data, voice and video into three networks. From the perspective of network operators, FTTH also enhances the physical network to data format and rate. The transparency of wavelengths and protocols eases the requirements for environmental conditions and power supply conditions, which simplifies maintenance and installation while reducing the cost of network operation.
Optical access networks can be divided into four basic application types: fiber-to-the-road (FTTC), fiber-to-the-building (FTTB), fiber-to-the-home (FTTH), and fiber-to-the-office (FTTO), depending on the location of the optical network unit. . The FTTH access network is a fully transparent optical network. It has no restrictions on the transmission standard, bandwidth, wavelength and transmission technology. It is suitable for introducing new services. It is an ideal network and a long-term goal for the development of optical access networks.
2. Typical networking structure of FTTH
FTTH is a broadband access method currently promoted by China Telecom. It can provide broadband services such as voice, data, CATV and IPTV for home and enterprise customers. FTTH is usually implemented in PON systems through the dynamic bandwidth allocation (DBA) function of PON systems. FTTH provides users with a better broadband experience and service.
The FTTH network consists of three parts: the central office equipment (OLT), the user terminal equipment (ONT), and the optical distribution network (ODN). As an important part of the FTTH network, ODN is the optical transmission physical channel between the OLT and the ONU. It is usually composed of fiber optic cable, optical connector, optical splitter and supporting equipment for connecting these devices. The ODN consists of five parts: the feeder segment, the cable distribution point, the wiring segment, the fiber optic cable access point, and the home segment. As the focus and difficulty of FTTH scale deployment, ODN directly affects the overall cost, system performance and reliability.
According to different service needs of users and home wiring, the home network can adopt different home networking modes. It can be wired or wired + wireless AP. It can easily and flexibly access voice, broadband Internet access and IPTV. , WLAN and other services.
3, optical network solutions
3.1 apartment solution
For apartments on different floors, the following two solutions are mainly used:
(1) Direct entry plan. In view of the infrastructure considerations in multi-storey apartments, multi-storey apartments should be equipped with a unit optical splitter box in each residential unit. It can also be placed in the side wall of a floor of a building, and wall-mounted concealed installation is often used. A small indoor or outdoor universal optical junction box is installed in each building unit, which is terminated on a two-core feeder cable, and then the optical signal is directly sent to each household through an optical splitter and a sheath optical cable. . Among them, the optical splitter can be determined by the difference of the unit households, so that the optical splitter modules of different ways can be flexibly selected in the small optical junction box, and the household optical cable terminated to each household is welded. the way. Set a standard 86-type distribution box in the household, or connect the user ONT unit directly to the household optical cable, that is, the direct entry plan.
(2) The optical splitter centralized setting scheme. In view of the infrastructure considerations in the high-rise, the optical splitter should be placed in a weak or weak electric well that can accommodate the user's middle floor, and then consider how to configure the quantity and how to set the layer according to the total amount of users. An indoor light junction box is centrally placed in the high-rise apartment, and the modular optical splitter is centrally installed in the indoor light junction box.
3.2 Villa Solution
In the villa area, the plug-and-play pre-connected cable system solution takes into account the infrastructure considerations in the villa area. When designing the outdoor pipeline as a whole, you should first understand the layout of the indoor communication concealed pipe and select the correct optical cable. The deployment plan, and the correct choice of the optical intersection setting point and the preset position of the cable joint box, in order to effectively control the size of the pipeline construction and reduce the investment in the cost of the household optical cable. In the villa area, we have set up a number of local aggregation point transfer boxes, so that we can manage the fiber network of users in each area separately.
3.3 Reconstruction area
Considering factors such as bandwidth demand, input and output, and copper exit, the recent transformation of optical copper into the film in the existing region is still based on FTTB/FTTN, and strives to make the entire network generally have access bandwidth of more than 12M. Ability to support HD video services widely. For existing copper cabling areas that already have the ability to provide certain access bandwidth, such as the potential high bandwidth demand of users and fierce market competition, the FTTH retrofit mode can be appropriately advanced, and optical fibers, optical splitters, optical splitter boxes, etc. The layout is placed in the user's building and on each floor, so that the FTTH installation can be completed quickly according to the user's needs.
4. Problems to be solved in the development of FTTH
4.1 Technology and cost bottlenecks
From a technical point of view, the widely used ADSL technology has certain advantages in providing broadband services. Compared with FTTH, the price is cheap. The original copper wire network is used to make the project construction simple. For the current 500kbit/s to lmbit/s film and television programs. Still meeting the demand, it is the main competitor of FTTH. From a global perspective, 66% of broadband users use xD-SL, which is as high as 90% in China. As the ideal way of broadband access, the main reason why FTTH has not been developed on a large scale is that the cost of fiber access is still relatively high. Due to the high price of optoelectronic devices and other factors, FTTH is difficult to popularize. We are currently using optical fiber transmission in the backbone network, and adopting multiple access methods such as Ethernet in the access level of the last mile.
At present, the labor cost of deploying FTTH in China will be much less. The FTTB+LAN solution with cost and bandwidth compromise, although the access cost per household has been reduced, is still much higher than the current ADSL access. At present, the most bandwidth-consuming P2P applications cannot bring high benefits to network operators, which has somewhat hampered their enthusiasm for promoting FTTH.
4.2 Policies and regulations are in urgent need of improvement
At present, the development of China's promotion of fiber-to-the-home is basically in a state of war. The policies of various local governments are different, sporadic and fragmented, and some places have not yet encouraged preferential policies. In short, the government lacks a macro guidance and a sound industrial policy. In addition, there is a lot of work to do with Internet-related copyright laws. The biggest driver of FTTH development is bandwidth demand and the killer application is IPTV. Due to the state's policy constraints on network video, this has inhibited the growth of bandwidth demand to some extent.
Conclusion
The FTTH is characterized by its enormous bandwidth, which is the best solution to the “last mile†bottleneck from the Internet backbone to the user's desktop. From the current status of broadband networks and the competitive situation, FTTH's high-bandwidth, potential market for additional value-added services, low maintenance costs, high-speed and rapid installation, and its network are not easily occupied by other operators. It has strong competitiveness and has a very large market potential.
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