How to construct the access Layer optical cable network

With the rapid development of broadband multimedia service and optical fiber communication technology, optical fiber communication technology has been used more and more widely in the access network. In the past, optical fiber network is mainly to meet the needs of transmission network construction, access to the layer of fiber optic cable needs less, a small number of access layer cable is generally directly from the convergence node pull out. With the rapid increase of data optical fiber and user optical fiber demand in recent years, telecom operators have also increased rapidly in the access layer cable construction. How to construct the Access Layer cable network has become a widely discussed topic in the industry.

First, Access Layer cable construction principles

According to the network layering principle, we divide the local network cable into the relay layer and the access layer, the Access layer cable refers to the cable from the local bureau station to the terminal of the user equipment, and the connecting layer cable is divided into the backbone layer cable and the wiring layer cable.

The access layer cable is the basic resource of the telecom operators, and it should be organized from the aspects of network investment control, security, expansibility and structure clearly.

1. Moderately advanced, step-by-step implementation

In order to avoid duplication of construction, repeat investment, and quickly meet the needs of business development, in the construction process should adhere to the principle of moderately advanced construction. At the same time, because of the complex and changeable access layer network environment, the access technology is changing rapidly, in the case of fully considering the cost of investment, we should strengthen the network planning according to the market demand, and follow the plan. ---http://bianceng.cn (computer science)

2. Layered Construction

According to the clear requirements of the network structure, the access layer cable should be divided into main layer cable and wiring layer cable for construction. The main layer includes the main layer fiber optic cable and the optical handover node equipment, the wiring layer includes the wiring layer cable, the optical distribution node and the user terminal facilities. The construction of the main fiber optic cable should be kept relatively stable according to the plan, and the construction of the cable layer should adapt to the characteristics of market and technology change quickly, so it needs to be layered to meet these requirements and characteristics.

3. Topology Selection

The optical fiber access layer has three basic structures, star type, linear line and ring type. In principle, the main layer fiber optic cable adopts ring topology, mainly because the service of the collection layer of User service access needs to provide ring protection or dual-route protection. For the rural areas, such as the non-dense area, optical cable routing does not have the ring conditions, the backbone of the cable topology can be considered temporary fragmentation.

The wiring layer cable is limited by cost and route, it is difficult to ring network, and it often adopts tree or star type structure. For businesses that require a higher level of security, they can be protected by either a ring or a dual route. According to the distribution of users and business in the wiring area, security requirements, objective geographical conditions and other factors, flexible use of multiple optical distribution points and single optical channel junction network, or multiple optical distribution points through the dual-optical junction network topology.

4. Light Handover Equipment Setup

The optical handover equipment refers to the optical handover node and the distribution node for flexible dispatch and distribution of the access layer cable, and the principle of its setting is mainly considered from the pipe hole resource, the business demand, the user nature, the network security and so on.

Considering the pipe hole resource, user's attribute and potential business demand, the light transfer area is determined. If the choice in the user density is larger, the pipe hole resources Richer place sets up the light handover node, facilitates the optical cable access, facilitates each wiring cable construction.

The setting of light junction point and light distribution point should be based on local city planning and telecommunication network planning, and should be set up in party and government departments, institutions of higher learning, enterprises, offices and residential districts so as to quickly realize user access.

From the network security considerations, should be set up as far as possible in the room with property rights or long-term right to use the indoor room; the outdoor light handover node should be set in a more stable geographical area, which will not be affected by the municipal construction, and avoid the external high voltage interference, high temperature, corrosion and inflammable and explosive

From the business coverage considerations, a main light handover node coverage of the 500m-800m as a radius of the community or 5-15 multi-storey residential buildings, accommodating the number of users of 300-800 households, should be based on the light transfer area within the distribution of user density reasonable layout, Suburban or rural areas can be further expanded to cover the actual needs of the business.

5. Selection of fiber core quantity of optical cable

The number of optical fiber cores should be determined on the basis of the full forecast of the user's distribution and business demand in the service area. Reasonable development of the business life of optical cable, according to the fiber optic cable service range of core demand, cable routing conditions, pipeline resources, optical fiber core kilometer cost factors, reasonable planning of the number of light handover node. Cable fiber core business to meet the proposal to consider in 5 years, the backbone of each light junction point of the number of the core of the proposed 36-96 cores, wiring layer of each point of light distribution points of the number of core recommended 24-48 core.

Backbone fiber optic cables generally adopt a ring-free fiber mode, the core number: 72-288 core. In the core configuration, the backbone of the core fiber optic cable distribution should be 6 or 12 cores for the unit, at the same time, according to the actual needs of the allocation of shared fiber core, exclusive fiber core and straight-through fiber core.

Wiring cable in general according to the actual situation of the flexible use of star-tree without diminishing wiring or star-tree type of decreasing wiring, the use of Star-tree type without diminishing the advantages of fiber optic cable is higher flexibility, optical fiber core easy to adjust, sharing, for the sudden new user needs easier to meet. The disadvantage is that the cost is relatively high, the security reliability is lower than the ring network topology. The use of the star-tree descending mode is the wiring cable is star-shaped, tree-type connection topology, fiber core from the initiator end to the distal node to reduce the level, the advantage is that the flexibility of the cable is high, easy to control the cost. The disadvantage is that the fiber resources are not shared, if the node's user forecasts a slight deviation, will cause the new node without fiber core and the original node core excess, the other security reliability is insufficient. Wiring cable Core number should not be too large, it is recommended to 6 core Unit organization, high-density zone to 12 core units to determine wiring cable core number, the general selection of core: 36-48 core/12-24 core. Optical junction points in the wiring cable cores can be appropriate more than the backbone of the fiber number, for the user cable recommended 4-12-core cable, and a cloth put in place.

The minimum ratio of the main cable and wiring cable is 1:1.2, the maximum is 1:4.

In order to build the main ring of the connecting layer cable, the light junction point is set up in the dense area of the large commercial and passenger group, and the light distribution point is followed up according to the business requirement.

6. Cable model Options

Access layer transmission distance near, the recent bandwidth requirements are not high, construction costs should be the main factor to consider, it is recommended to use the best 1310nm wavelength performance of the single mode fiber, namely g.652 fiber.

Because of the good mechanical properties of the laminated cable, the cost of the central beam tubular cable is relatively low. More than 72 cores of cable recommended the use of central beam tube ribbon cable, small core number of optical cables recommend the use of laminated cable.

Second, the development strategy of Access layer cable

The construction of Access layer optical cable also needs to consider the future development strategy, in order to better adapt to the new requirements of the business network.

1. Construction of optical cable access layer on demand

The main purpose of the Access Layer optical cable is to satisfy the users ' access to the Broadband multimedia service, in the course of construction, we should take market demand as the guide, strengthen the planning of the cable access layer network according to the different users ' distribution and business requirements, and implement the principle of meeting the demand and controlling cost. In the planning process to focus on the following aspects of the needs.

Access layer network equipment needs to be networked, including narrowband devices, broadband equipment, metropolitan area Network and Community network equipment for optical fiber cable needs. Mainly consider the construction of the backbone layer cable, as far as possible to achieve the cable into the ring, improve network security.

Large customer cable network requirements. Mainly consider the construction of cable-fiber cables, according to the user's nature and business requirement in the light handover node coverage area.

The demand of the cable network element rental business is relatively few.

3G and other new business development needs. With the future construction of 3G networks, the base station (NODEB) and the Remote Access Unit (RRU) will need to be transmitted through optical cables, which should be focused on when planning.

2. Make full use of the existing copper cable resources

Using twisted pair of ADSL technology to transmit 8M bandwidth data can reach 1 km-2 km, 4M can reach 2-3 kilometers, with the development of XDSL technology, transmission bandwidth will be higher. In the recent broadband demand for users generally low, China Telecom to make full use of the existing large number of copper resources, through the construction of integrated access network, shorten the user cable access distance, improve access to bandwidth, to achieve universal user width with business access. For a small number of large customers high bandwidth access requirements (such as 10M, 20M or more bandwidth), the use of optical cable access transmission. Therefore, in the implementation of "light into the copper back", combined with integrated access to the network planning to make access to the layer of optical cable planning and construction, the optical junction point and access to the network synchronization planning, priority to build the backbone of cable networks, wiring layer in accordance with the needs of users to advance gradually. This can not only make full use of the existing copper resources, but also can quickly meet the needs of business development, so that the network structure has a strong flexibility and scalability.

3. Strengthen the tracking of new technologies

The development of PON (passive optical network) and CWDM (Wavelength division multiplexing) will have a far-reaching impact on the construction of Access layer optical cable.

The convergence of PON or other equipment can save the number of cores in the fiber optic cable, and improve the utilization ratio of fiber core single core bandwidth. After the introduction of PON technology, the Pon Optical Splitter (Splitter) is generally placed in the optical junction node or light distribution point of the access Layer optical cable network, which requires a new requirement for the space allocation of the specific handover equipment of the optical junction or distribution point, and the corresponding space and port should be reserved in the construction.

But because the current PON, CWDM equipment cost is also more expensive, mainly consider the construction of direct-connected optical cable, at the same time tracking the technical progress, carry out the corresponding equipment testing and testing. With the development of PON technology and the decrease of the cost of optical communication equipment, the equipment is gradually increased to reduce the pressure of the access layer optical cable resources.

With the development of apon (Intelligent Optical Network), the rapid increase of users ' demand for broadband, FTTH evolution will be further accelerated, the construction of optical cable access layer will be more and more. The construction of cable access layer network needs to meet the needs of users ' high bandwidth multimedia service According to the change of user's requirement, the use of optical communication technology, the network security, scalability and investment economy.