Fiber optic cable is a communications cable consisting of two or more glass or plastic optical fiber cores located within a protective cladding and covered by a plastic PVC outer sleeve.
Signal transmission along internal optical fibers generally uses infrared light.
1. Selection of the number of cores of optical cables: Under the conditions of convenient construction, try to choose optical cables with larger coil lengths.
When selecting the number of fiber optic cable cores, it is necessary to combine benefits with long-term planning and fully consider the possibility of capacity expansion; according to the guiding ideology of "building one line to serve a large area", fully consider the communications of major units along the way. need.
2. Selection of optical cable structure program. The long-distance trunk optical cable should use single-mode optical fiber with a wavelength window of 1310nm and can be used in the 1550nm window; the fiber screening tension should not be less than 5N (Newton); use metal-free wire pairs For optical cables, in areas affected by severe lightning strikes or strong electricity, non-metallic components can be used to strengthen the core optical cable, and the optical cable core adopts a grease-filled structure.
Regulations on the selection of optical cable sheath structures: overhead and pipeline optical cables (simple plastic pipes) are moisture-proof layer + PE outer sheath; direct buried optical cables are moisture-proof layer + PE inner sheath + steel tape armor layer + PE outer sheath; underwater optical cable is moisture-proof layer + PE inner sheath + thick steel wire armor layer + PE outer sheath.
The mechanical properties of optical cables should comply with the requirements in Table 1.1.
When the optical cable is subjected to short-term allowable tension or lateral pressure, the fiber attenuation does not change after the tension or lateral pressure is relieved, and the fiber elongation is not greater than 0.15%; when the optical cable is subjected to long-term allowable tension or lateral pressure, the fiber attenuation is not changed. Change, the elongation rate of the optical cable is not greater than 0.2%, and there is no strain in front of the light.
3. Underwater optical cables should be selected for major navigation rivers where there are many navigable motor ships, sailboats and rafts. Steel wire armored optical cables should be used; when the river flow is particularly fast and the river course changes greatly, double-layer steel wires should be used. Armored optical cable; plain rivers with a river width (between two embankments or natural banks) greater than 150m should use steel wire armored optical cables; although some rivers are less than 150m wide, their flow speeds are high (above 3m/s), and the river bed soil is loose, If both sides of the bank are prone to erosion and landslides, the river bottom is rugged, or it is a stony river bed or a large pebble river bed, rigid wire-armored underwater optical cables should be used. Although some rivers are no more than 150m wide, the soil quality of the river bed is stable and the flow rate is very small. If it is straight and free of erosion, rigid-wire armored underwater optical cables may not be used; mountainous rivers should be determined based on river bed soil quality, flow velocity, flow size, degree of erosion, and upstream hydrology.
When setting up spare underwater optical cables, comprehensive considerations include: extremely large rivers; larger rivers with poor river bed stability; other special requirements; limited to natural terrain and construction conditions, the safety of optical cables is relatively low Poor or emergency repair is difficult.
