An FTTH cable is a single fiber directly to the home. Specifically, FTTH optical cable refers to the installation of optical network units (ONUs) at home users or enterprise users. It is the optical access network application type closest to the user in the optical access series except FTTD (fiber to the desktop).
With the development of science and technology, FTTX technology makes the optical fiber closer and closer to the end user, and this form will definitely bring greater performance convenience to the user. All aspects of optical fiber superior to copper wire, including bandwidth, speed, data format, and transparency of wavelengths and protocols, etc., will directly face homes and businesses, and some limitations of copper wire in the past will also follow the "retirement". The process of copper" gradually fades out of people's sight.
ZR Cable system
1. Analysis of the basic structure and advantages of FTTH network
- A typical EPON system consists of OLT, ONU, ODN:
The OLT is placed in the central computer room, and it can be regarded as an L2 switch or an L3 routing switch. In the downstream direction, the OLT provides optical fiber interfaces for Yuanyuan Optical Network (ODN); in the upstream direction, the OLT will provide GE light and electrical interfaces. After the 10Gbit/s Ethernet technology standard is finalized in the future, the OLT will also support similar high-speed interface. In order to provide multi-service access, the OLT can also support interfaces such as E1 and OC3 to implement traditional voice access or circuit relay services.
ODN is an optical distribution network, which consists of passive optical fiber splitters and optical fibers. Passive optical fiber splitter is a passive device connecting OLT and ONU. Its function is to distribute downlink data and concentrate uplink data. The deployment of passive optical splitters is quite flexible. Since it is a passive device, it can be adapted to almost all environments. Generally, the splitting ratio of passive optical fiber splitter is 1:2, 1:4, 1:8, 1:16, 1:32, 1:64, etc. Generally, it is recommended to use first-order spectroscopy, and at most the second-order spectroscopy cannot be exceeded.
The ONU is a terminal device placed on the customer premises side. The ONU in the EPON adopts the Ethernet protocol, which realizes the low-cost Ethernet Layer 2 switching function. Due to the use of the Ethernet protocol, protocol conversion is no longer required in the communication process, and the ONU can transparently transmit user data. An encryption protocol is used between the OLT and the ONU to ensure the security of user data.
2. Analysis of FTTH optical cable system
According to the whole network system of FTTH, the optical cable network is divided into 3 parts, namely the feeder segment, the distribution segment and the household segment.
(1) The feeder optical cable is the optical cable from the OLT equipment room to the optical distribution point. In some cases, this optical cable is the existing MAN optical cable that has been laid, or a small amount needs to be cut and connected from the existing MAN optical cable nearby. number of fiber cores. When this section of optical cable needs to be re-laid, the expected growth of users and the development of potential business needs should be fully considered to avoid repeated investment in the future. The selection of feeder optical cables is basically the same as the selection of conventional metropolitan area network optical cables.
(2) FTTH distribution cables usually require frequent disconnection and branch connection. According to the cable core structure, the distribution cables usually have several types of stranded loose tube cables, loose tube ribbon cables and skeleton ribbon cables. According to the application Different distribution cables in the environment can be divided into indoor optical cables, outdoor optical cables and indoor and outdoor optical cables. Among them, the commonly used distribution cables in pipelines are layered loose-tube cable and loose-tube ribbon cable. Distribution cables commonly used in shafts are branch-type vertical wiring cables, bundled vertical wiring cables and micro-tube indoor and outdoor optical cables. .
Diverging and splicing technology can be used in the branching and splicing of optical cables to avoid unnecessary cutting of a large number of optical fibers, but the use of the supporting optical cable splice box and the fiber distribution box in the building must have the function of digging and splicing. Fiber optic cable splicing is a very common construction technology. Ordinary loose-tube optic cables and ribbon optic cables can be spliced and spliced. When the number of cores of the optic cable is not large, the use of loose-tube optic cables will have more cost advantages. When the loose tube optical cable is constructed, only one or more loose tubes need to be cut each time. The number of loose tubes and the number of each core are designed according to different needs.
The single-layer stranded optical cable can contain up to 12 loose tubes, and the double-layer stranded optical cable can contain up to 18 loose tubes for different use. The following is a brief introduction of several commonly used wiring optical cables:
1. Branch-type vertical shaft optical cable: single-core sub-unit optical cable structure, convenient for branch operation, good fiber protection, easy for long-distance laying in the building, the maximum number of single-strand optical cable cores can reach 24 cores, and the tensile strength of the optical cable meets the indoor vertical / The level requirements of the horizontal wiring optical cable, the flame retardant performance of the optical cable meets the requirements of the NEC770 OFNR flame retardant standard.
2. Bunched building shaft optical cable: all-dielectric structure, excellent flame retardant performance, 0.9mm tight-fitting optical fiber, safe construction and operation in the building, the maximum number of single-strand optical cable cores can reach 24 cores, and the tensile strength of the optical cable meets the indoor vertical chanting The level requirements of the flat wiring optical cable, the flame retardant performance of the optical cable meets the requirements of the NEC770 OFNR flame retardant standard.
3. Micro-bundle tube indoor and outdoor optical cable: The flame retardant performance of the optical cable meets the requirements of the NEC770 OFNR flame retardant standard, excellent water and moisture resistance, can be laid across the building pipeline, can be used for vertical wiring in the building shaft, soft and easy to wear For laying, the cable core structure can be flexibly designed according to different needs, and the number of cores is 12-144 cores.
(3) According to the environment of the household, the optical cable can be outdoor optical cable, indoor optical cable or indoor optical cable.
Outdoor fiber optic cable. Optical cables for households should use optical cables with simple structure, easy operation, and strong tensile and lateral pressure resistance, so as to facilitate the placement of overhead, outdoor pipes and pipes in buildings, and to ensure the reliability of optical cables. According to the route of the optical cable to the household, the household optical cable for pipeline access can choose the Untibe type indoor and outdoor optical cable, the pipeline "8" optical cable; the household optical cable in the building can choose the "8" wiring optical cable for indoor household use;
For overhead household optical cables, you can choose self-supporting "8" figure wiring optical cables for overhead households. The following is a brief introduction of several common wiring optical cables as follows: 1. "8" indoor wiring optical cable (DC-2S-2BIF15): suitable for entering the house in the way of pipeline or open line in the building, small bending radius optical fiber, and many Field connector mating. 2. "8" overhead fiber optic cable: for indoor and outdoor applications, easy to operate, self-supporting overhead, span up to 50 meters, bend-insensitive fiber, suitable for a variety of field connectors. 3. Unitube type indoor and outdoor optical cable (IOUC-2B1.1): all non-metallic structure, outer diameter 5.2mm, weight 25kg, tensile strength 600N. 4. Pipe "8" wiring optical cable (DDC-2F-2BIF15): bend-insensitive optical fiber, suitable for various field connectors with an outer diameter of 6.8mm, a weight of 48kg, and a tensile strength of 600N.
3. Conclusion
The terminals of FTTH are thousands of households. No matter in rural areas or urban communities, complex wiring systems and super-large branch systems require convenient construction conditions. Micro-cables with large core count, convenient construction, strong branching capabilities, and relative cost advantages will lead the way of fiber-to-the-home access. It can be shown from the usage at home and abroad: the optical cable structure of FTTH access system will develop along the trend of micro-cable; the maintenance of optical cable line will develop in the direction of non-interrupted field test and maintenance; the development of FTTH access optical communication network in China is also necessary for reference.
