Evolution of optical fiber manufacturing technology

Exploration phase of China's optical cable manufacturing in

Since the application of the first practical multi-mode optical fiber cable in China in 1982, China's optical fiber manufacturing and industrialization have gone through 30 thoughts and experienced three ups and downs once a year, today, the world's largest optical fiber industry and related industrial clusters have been formed, with an annual production capacity of nearly 0.1 billion cores and an annual production capacity of cores. As the world's largest optical fiber manufacturing country, our optical fiber enterprises are looking back at the development of the industry, which is inseparable from the technological innovation of the optical fiber manufacturing process over the past thirty years, chinese enterprises are already at the world's advanced level in the selection of three structures: skeleton, central pipe, and layer twisting, Research on Mechanical Properties of optical cables, engineering applications, and theoretical calculations and summaries.

China's optical cable manufacturing can be said to start with international synchronization, but in the 1990s s when the basic industry and technology were lagging behind, China's optical cable manufacturing technology was dominated by the introduction of technology, among them, the skeleton single-screw twisted cable mainly used by Houma cable factory first appeared, and then a central pipe structure emerged. The agricultural cable of the central bundle cable developed by Wuhan Institute of Posts and Telecommunications) it is still an important optical fiber cable.

Skeleton Cable

EarlyOptical FiberThe technology is not complete yet. The coating on the optical fiber surface is still using heat-Cured Silicone. The weakness of the optical fiber cables makes the protection of optical fiber cables more important, and the control of cables is also demanding, at that time, the optical fiber was more sensitive to side pressure,-OH, and bending. Therefore, a bone-frame single-screw twisted cable with complicated technology was developed, and the bare fiber was placed in the U-shaped frame trough of S-twisted, from Single-fiber Skeleton Development to multi-fiber skeleton, optical fibers in the same skeleton cell are distinguished by chromatography. Shows the optical cable structure:

Skeleton Cable

The design idea of the skeleton trough comes from the cable, which has a good protective effect on the side pressure of the optical fiber. The displacement of the optical fiber in the trough is used to resist the deformation of the optical fiber cable due to the tension and temperature change. However, its disadvantage is obvious: first, the production process of the skeleton trough is high and the efficiency is low. Second, the cable-forming equipment is complex, the synchronization of the receiving and releasing lines is high, the torsion is complex, and the speed is slow, it cannot be achieved for the large-core cable. Finally, it is found that the quality and filling of oil paste have a great impact on the cable life in engineering applications. In view of these problems, such structures were gradually eliminated in the early 1990s S, but some of their features and ideas will be used now, which will be introduced later.

Central tubular Optical Cable

With the center tube loose structure represented by AT&T, the optical fiber is located in the center of the optical fiber cable, which has good bending characteristics and compact structure. After its introduction, it has become a major breed, wuhan Institute of Posts and Telecommunications, in light of the vast territory of China and the small capacity of fiber-optic communication at that time, developed the first patent product with Chinese characteristics, the central bundle tube optical cable. For the structure, see:

Typical central pipe structure

The central pipe structure also has several forms. The earliest structure was not steel armor, and the parallel galvanized steel wire was used for strengthening. The water seepage and low temperature characteristics were not good enough. Later, the steel armor was added, it is China's first cable and steel strip forming technology, using hierarchical molding, steel strip interconnection, Hot Melt Adhesive Bonding Technology, solved the problems of water seepage and high and low temperature, the technical standard prototype of steel strip is determined, but the optical cable is very difficult to be peeled off. At last, the technology of filling with water blocks or oil paste is developed to further rationalize the structure. However, in terms of structural characteristics, when there is more than 12 cores, it is necessary to use a complex bundle technology to distinguish the optical fiber. Later, a spray ring technology was developed for OPGW. When multiple sets of optical fiber are placed in one casing, multiple fiber frames are needed. The utilization rate of the equipment is limited, which is not conducive to large-scale production and is not easy to differentiate in Engineering.

The key technology in the manufacture of central optical fiber cables is the Residual Length Control Technology of optical fiber cables in the casing. In this period, the Residual Length Control Technology of the speed difference method was first introduced, this method is controlled by the 1-8‰ speed difference between the tractor and the track traction. This method has the advantages of intuitive controllability, but it also has the problem that the equipment is not accurate after being complex and easily worn; the method for controlling the remaining length of water temperature appears later. This is a major improvement. The remaining length is controlled through two-level tanks and intermediate tractor, the disadvantage is that process parameters need to be stabilized through process exploration between different specifications. At present, the water temperature control method is widely used in the production of layer twisted casing, but this method is still difficult for the stable production of a large amount of time.

Although the central pipe optical cable has been around for a long time, it is not easy to make the product well. Its vertical packing molding process will reduce the remaining length, and the coating will be too loose, which will lead to casing shrinkage or elongation at high and low temperatures, in the project, fiber breakage or loss increases at the head box. For this reason, IEC adds a test, but it is not used in China. The coating is tight and the excess length is eaten, this reduces the tensile strength. Therefore, there has been a lot of debate on this structure for a period of time. In fact, the product quality and the manufacturing stability and controllability of production enterprises are clearly reflected in this product.

Other structures and conditions of Optical Cables

During this period, there were some structural explorations, such as the closed outdoor optical cable. The closed structure has better protection than the bare fiber, but the loss is high, the cable with the same structure has poor mechanical performance and low production efficiency. It is not selected as a long-distance cable.

A deformation of the center pipe structure is the steel wire armor structure, which is still used so far. A single fine low carbon steel wire of 0.6-1mm is twisted outside the casing, and the steel strip jacket is added, this product has more applications in the radio/TV system.

In the past ten years, the development of China's optical fiber industry has been inseparable from the start of a business by manufacturers of raw materials. The raw materials at the beginning were imported products, such as fiber paste and cable paste imported UNIGEL and ASTOR, the water resistance belt is gaike, And the PBT is German hertz. Only the aluminum belt is replaced by the cable aluminum belt. By the end of 1980s, some research institutes and enterprises were successively involved in the raw materials, and they started research and testing in the fields of fiber paste, cable paste, water resistance belt, and composite metal tape.

The introduction of optical fiber cables is more than the above. For more information, see: Introduction to the evolution of optical fiber manufacturing technology.

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