Manufacture and selection method of optical cable
1. Manufacture of optical cable:
The manufacturing process of optical cable is generally divided into the following processes:
1) Screening of optical fibers: select optical fibers with excellent transmission characteristics and qualified tension.
2) Dyeing of optical fibers: use standard full chromatogram to identify, requiring high temperature not fading and not migrating.
3) Secondary extrusion: Use plastic with high elastic modulus and low linear expansion coefficient to extrude into a certain size tube, incorporate the optical fiber and fill it with moisture-proof and waterproof gel, and store it for a few days (not less than two days) .
4) Optical fiber cable twisting: twist several extruded optical fibers and strengthening units together.
5) Squeeze the outer sheath of the optical cable: add a layer of sheath to the twisted optical cable.
2. Types of optical cables:
1) According to the laying method, there are: self-supporting overhead optical cable, pipeline optical cable, armored buried optical cable and submarine optical cable.
2) According to the optical cable structure, it is divided into: bundled optical cable, layered optical cable, tightly hugged optical cable, ribbon optical cable, non-metallic optical cable and branchable optical cable.
3) According to the use, it is divided into: optical cable for long-distance communication, short-distance outdoor optical cable, hybrid optical cable and optical cable for building.
3. Construction of optical cable:
Over the years, the construction of optical cables has enabled us to have a set of mature methods and experience.
Outdoor construction of optical cable:
The most important thing for long-distance cable laying is to choose a suitable path. The shortest path is not necessarily the best, but also pay attention to the right to use the land, the possibility of erection or burial, etc.
There must be very complete design and construction drawings for convenient and reliable construction and future inspections. During construction, be careful not to put the optical cable under heavy pressure or be punctured by hard objects.
When the optical cable turns, its turning radius is 20 times larger than the diameter of the optical cable itself.
1) Construction of outdoor aerial optical cable:
A. The overhead method of hanging wire brackets is simple and cheap, and is the most widely used in my country, but it is time-consuming to add hooks and arrange them.
B. Hanging wire winding overhead method, this method is more stable and less maintenance work. But a special wrapping machine is required.
C. The self-supporting overhead method has high requirements on the trunk line, difficult construction and maintenance, and high cost. It is rarely used in China at present.
D. When overhead, a guiding device must be installed at the place where the optical cable leads to the trunk, and the optical cable should not be dragged to the ground. Pay attention to reducing friction when pulling the optical cable. A length of fiber optic cable should be left on each trunk for expansion and contraction.
E. Pay attention to the reliable grounding of metal objects in the optical cable. Especially in mountainous areas, high-voltage power grid areas and many areas, there are generally 3 grounding points per kilometer, and even non-metallic optical cables are used.
2) Construction of outdoor pipeline optical cable:
A. Before construction, the occupancy of the pipeline should be checked, the plastic sub-pipes should be cleaned and placed, and the traction line should be placed at the same time.
B. Calculate the deployment length, and there must be enough reserved length.
C. The length of one laying should not be too long (generally 2KM). When wiring, it should be pulled from the middle to both sides.
D. The traction force of the cable is generally not more than 120kg, and the reinforcing core part of the optical cable should be pulled, and the waterproof and strengthening treatment of the head of the optical cable should be done.
E. The lead-in and lead-out of the optical cable must be equipped with a follow-up device, and the floor cannot be directly mopped.
F. The pipeline optical cable should also pay attention to reliable grounding.
3) The laying of directly buried optical cables:
A. The depth of direct buried optical cable trench should be excavated according to the standard. The standard is shown in the following table:
B. Where trenches cannot be dug, the pipelines can be laid overhead or drilled.
C. The bottom of the ditch should be flat and firm, and a part of sand, cement or support can be pre-filled if necessary
D. Manual or mechanical traction can be used when laying, but attention should be paid to guidance and lubrication.
E. After the laying is completed, the soil should be covered and compacted as soon as possible.
4) Laying of optical cables in buildings:
A. When laying vertically, special attention should be paid to the load-bearing problem of the optical cable. Generally, the optical cable should be fixed once every two layers.
B. When the optical cable passes through the wall or floor, a protective plastic pipe with a mouth guard should be added, and the pipe should be filled with flame retardant filler.
C. A certain amount of plastic pipes can also be laid in advance in the building, and when the optical cable is to be laid in the future, the optical cable can be laid by traction or vacuum method.
4. Selection of optical cable:
The selection of optical cables is not only based on the number of optical fibers and the type of optical fibers, but also the outer sheath of the optical cable according to the use environment of the optical cable.
1) When the outdoor optical cable is directly buried, the armored optical cable should be selected. When overhead, an optical cable with a black plastic outer sheath with two or more reinforcing ribs can be used.
2) When selecting optical cables used in buildings, attention should be paid to their flame retardant, poisonous and smoke characteristics. Generally, the flame-retardant but smoke-bearing type (Plenum) can be used in the pipeline or forced ventilation, and the flame-retardant, non-toxic and smoke-free type (Riser) should be used in the exposed environment.
3) When cabling vertically in the building, you can choose Distribution Cables; when laying horizontally, you can choose Breakout Cables.
4)If the transmission distance is less than 2km, you can choose multi-mode optical cable. If it exceeds 2km, you can use repeater or choose single-mode optical cable.