Evolution of optical cable manufacturing technology

 

Abstract: This paper introduces the improvement and improvement of the technical process route in the manufacture of optical cable in China for 30 years, and analyzes the existing process design basis, hoping to provide a useful basis for the development direction of optical cable technology.

 

Key words optical cable process design

 

1 Introduction

 

Since the application of the first practical multimode optical cable in China in 1982, China's optical cable manufacturing and industrialization development has gone through 30 thoughts. After three years and three outs of development, it has developed into the world. The largest optical cable industry and related industrial clusters have an annual production capacity of nearly 100 million core kilometers, and the actual annual output reaches 80 million core kilometers. As the world's largest cable manufacturing country, our cable companies look back at the development of the industry. It is inseparable from the technological innovation of the optical cable manufacturing process in the past 30 years. The choice of Chinese enterprises in the three structures of skeleton, center tube and layer stranding It has been at the advanced level in the world in the research of mechanical properties of optical cables, in engineering applications, and in theoretical calculations and summaries. As the earliest base for fiber optic cable research and industrialization, Wuhan Institute of Posts and Telecommunications has experienced all the technological changes in China's fiber optic cable and has its own patents for many important technologies. Therefore, for the past 30 years, the cable technology route The summary is of great significance.

 

2. The exploration stage of China's optical cable manufacturing from 1982 to 1990

 

China's optical cable manufacturing can be said to start at the same time as the international market. However, in the 1990s, when the basic industry and technology were backward, China's optical cable technology was mainly based on imported technology. Among them, the skeleton single-screw cable of Houma Cable Factory was the earliest. After that, there was a central tubular structure. The central beam tube cable (agricultural cable) developed by Wuhan Institute of Posts and Telecommunications is still an important variety of optical cables.

 

2.1 skeleton slot cable

 

The early fiber technology was still not perfect. The coating on the surface of the fiber was still made of heat-cured silicone. The fragility of the fiber made the protection of the cable more important. The control in the cable was also required. Pressure, -OH, and bending are more sensitive. Therefore, a skeleton-type single-helical stranded cable with a complicated process has been developed. The bare fiber is placed in the S-shaped U-shaped skeleton groove, and the single-fiber skeleton is developed to the multi-fiber skeleton. Differentiate the technique to distinguish the fibers in the same skeleton slot.

 

The design of the skeleton groove comes from the cable, which has a good protection against the side pressure of the fiber. The displacement of the fiber in the groove resists the deformation of the cable and the temperature change cable. However, its shortcomings are obvious. Firstly, the manufacturing process of the skeleton groove is high and the efficiency is low. Secondly, the equipment for cable-forming is complicated, the synchronization requirements of the retracting and discharging line are high, the twisting and twisting is complicated, and the speed is very slow, which cannot be realized for the large-core optical cable; Finally, in engineering applications, the quality and filling of the grease has a great influence on the life of the cable. In view of these problems, this structure was gradually eliminated in the early 1990s, but some of its features and ideas will be used now, which will be described later.

 

2.2 Central tubular cable

 

The central tube loose-sleeve structure represented by AT&T Company of the United States, because its optical fiber is located in the center of the optical cable, has good bending characteristics and compact structure. It has become a major variety after its introduction. The Wuhan University of Posts and Telecommunications combines China's vast territory and fiber-optic communication at that time. With the small capacity, the first fiber optic cable patented product with Chinese characteristics and the central beam tube cable were developed.

 

The central tube structure also has several forms. The earliest steel belt armor is not reinforced by parallel galvanized steel wire, and there is a problem that the water seepage and low temperature characteristics are not good enough. Later, the steel belt armor is added, which is the first optical cable steel strip in China. The bag forming process adopts the classification forming, the steel strip flat belt butt joint and the hot melt adhesive bonding process, solves the problems of water seepage and high and low temperature, and determines the technical standard prototype of the steel strip, but the optical cable is very difficult to open and peel; The structure was further rationalized by the use of a water barrier or grease filling process. However, from the structural point of view, when more than 12 cores appear, it is necessary to use a complex beam-bonding technique to distinguish the fibers, and then developed a nozzle ring process for the OPGW. When multiple sets of optical fibers are placed in one casing, multiple refrigerating frames are required, and the utilization rate of the equipment is limited, which is not conducive to large-scale production, and is also inconvenient in engineering.

 

The key technology in the manufacture of central tube cable is the length control technology of the fiber in the casing. In this period, the speed difference method is used first, and the speed difference between the traction wheel and the crawler is 1-8‰. To control, the method has the advantages of strong intuitive controllability, but also has the problem that the equipment is complicated and easy to wear after inaccuracy; the latter is the method of controlling the water temperature, which is a major advancement through the two-stage sink and The intermediate traction wheel is used to control the excess length. The disadvantage is that the process parameters need to be stabilized between different specifications to stabilize the process parameters. At present, the water temperature control method is widely used for the production of layered casing, but this method is still difficult for the stable production of large excess length.

 

Although the central tube cable has been around for a long time, it is not easy to really make this product. The longitudinal molding process will reduce the excess length, and the coating will be too loose, which will lead to shrinkage or elongation of the casing at high and low temperatures. There will be fiber breakage or loss increase at the joint box. For this reason, the IEC has added a test, but it has not been used domestically; the tightness of the coating has eaten excess length, resulting in a decrease in tensile strength. Therefore, there has been a lot of debate about this structure for a while. In fact, the quality of the products and the stability and controllability of the manufacturing companies are reflected in this product.

 

2.3 Other structures and conditions

 

During this period, some structural explorations have emerged, such as tight-structure outdoor optical cables. The tight-fitting structure has better protection than bare fibers, but the loss is large. Compared with the same structure, the loose-sleeve optical cable has poorer mechanical properties and production efficiency. Low, not selected as a long-distance cable.

 

One of the deformations of the central tube structure is the steel wire armored structure, which is still used today. It is wound around the casing with a single fine low carbon steel wire of 0.6-1 mm, plus a longitudinally sheathed steel strip. This product is used in radio and television systems. some more.

 

In this decade, the development of China's optical cable industry is inseparable from the start-up of raw material manufacturers. The first raw materials are imported products, such as fiber cream and cable paste are imported from UNIGEL, ASTOR, etc. Ke, PBT is German Hertz, etc., only the aluminum strip is replaced by cable aluminum. By the end of the 1980s, there have been some research institutes and enterprises that researched raw materials, and began research and experiments on fiber paste, cable paste, water blocking tape, and composite metal tape.

 

3. Development stage of China's optical cable manufacturing from 1991 to 2000

 

In the 1990s, due to the continuous increase in China's communications construction, especially the construction of optical fiber communications, China's optical cable industry has made considerable progress during this period, in terms of varieties, process equipment, raw materials, theoretical basis, and detection technology. Significantly enhanced, when the country's fiber optic cable demand is mainly trunk, so the structure is a process of convergence, there are several major types in the cable structure and manufacturing process.

 

3.1 layer twisted cable

 

In 1991, Wuhan Institute of Posts and Technology introduced the NOKIA loose-sleeved production line, and introduced S twisted cable from France. The layered-type optical cable began to be widely used. For the S-twisted structure, the retractable twisting technology of the retractable line was adopted. The distance is stable, and the ointment is filled with the polyester tape. The advantage is that the performance of the optical cable is stable, and the theoretical basis of the fiber optic cable length design is laid. The disadvantages are complicated equipment, low efficiency and high energy consumption. In 1995, SZ twisted cable equipment was developed, which greatly simplified the cable-forming equipment and improved the production efficiency. It adopts double-biased yarn, SZ reciprocating stranding process, grease filling, vertical packing or wrapping belt, the largest The 12-unit tube was produced, and the filling rope was developed as a filling unit. Two methods of distinguishing between the color of the lead and the whole of the chromatogram were designed.

 

The layered optical cable can be divided into direct buried type according to use, such as GYTA53, GYTY53, GYTA53+33, etc. The main pipelines and overhead are GYTA and GYTS. The difference in the structure of the protective layer leads to the difference in the process, the vertical wrapping process and the flat strip process of the aluminum strip appear, and the hot melt adhesive bonding process appears.

SZ twisting process plays an important role in the development of China's optical cable industry. All optical cable factories have SZ cable, and on the basis of S twisting design principle, the theory of complete tensile and temperature deformation is formed for SZ twisting. Guide the practice of production.

 

3.2 Ribbon fiber optic cable

 

Different from the casing technology, a plurality of optical fibers are arranged side by side into a belt technology. This technology was first used in Japan for the skeleton type cable, and the earliest introduced in China was the center tube type cable. The key technology of the optical fiber ribbon is the parallel belt. The main indicator is the control of the flatness. The colored optical fiber used is also different from the coloring process control of the ordinary colored fiber. The other key is the uniformity and tension of the receiving and discharging line. The casing process is matched.

 

The fiber in the fiber casing process is made of S or Z twisted pipe, so the other long concept is different from the ordinary casing. Because the casing is thick, the wheel traction is generally not used, and the track is mostly used. The key parameters of traction and control of excess length are: tape tension, pipe pitch, mold (multiple), water temperature and take-up tension. The theoretical calculation requires special calculation of the strain of each sideband fiber, and the actual test results. In combination with the certificate, the duty cycle and pitch of each plant design are relatively large at the beginning stage. With the increase of cost pressure, the process technology begins to work toward the small structure, and the process control capability of each plant can best be reflected in the cable structure. .

 

The skeleton cable has its own characteristics because of its no grease. During this period, only Changfei Company introduced this technology, but its application is not wide. The main problems are: Can not do 12 core belt, reduce the core of one welding The number is S twisted, which is inconvenient for any branch, complicated equipment, high cost and low efficiency.

 

3.3 OPGW cable

 

During this period, China's power grid construction was rapid, and the demand for power system communication was promoted. ADSS and OPGW were successively produced. For the ADSS, the aramid twisting process was mainly added in the process. In terms of control, the design was mainly large. Optical cable, and OPGW should be said to be a brand new variety of applications.

 

OPGW (composite fiber optic overhead ground wire) uses stainless steel welding technology, including stainless steel belt surface treatment, trimming, forming, seamless argon arc welding, oil filling, drawing, flaw detection and other complex technologies, placing multiple fibers In the stainless steel protection tube, the outer one-way stranded aluminum-clad steel strands will not damage the fiber even when a large current such as lightning strikes through the cable. Due to its excellent application characteristics, it has been widely used in new power systems, forming an industry of nearly 3 billion scale, and its stainless steel tube casing technology has laid the foundation for the realization of submarine cables.

 

3.3 Other process technologies

 

Ultraviolet light curing coloring technology, from thermal curing of 600 m / min, to 1500 m / min, the amount of materials is reduced, the effect and efficiency are greatly improved;

 

Coloring ring technology, adding a ring device on the coloring line, can achieve the effect of spraying multiple rings or different color rings on the fiber to distinguish the same color fiber;

 

High-speed fiber-set technology, in order to improve production efficiency, and the technical gap between domestic and domestic equipment manufacturers, foreign fiber-optic equipment manufacturers have developed a series of high-speed fiber-optic technology, including oil-filled control system, the dance wheel changed to line gauge Control, large length, automatic disk change, making the production speed reach 250 m / min;

 

Developed the winch process, reduced friction, improved the winch process, and proposed the torque bar process to improve efficiency and reduce the distance of the commutation point;

 

Closed mold steel strip forming technology, on the basis of absorbing foreign mold design principles, Chinese equipment development companies have also developed their own molding dies, so that each operator can replace the mold;

 

The tape wrapping process was abolished, first to prevent the heat of the sheathing process from being transferred to the polyester tape wrapping process developed on the casing, which was cancelled by most factories because there was no clear application evidence;

 

In the testing technology, Beiyou developed its own mechanical performance tester, and extensively equipped various optical cable factories, proposed B-OTDR, and used for the production of submarine cables;

 

During this period, domestic material factories have been established and expanded. The industrialization of the optical cable paste represented by the Wuhan Institute of Chemical Industry, the private steel aluminum belt enterprise represented by Qinbang, and the steel wire changed from galvanizing to phosphating. A distinctive road, the development of these industries has strongly supported the progress of our national optical cable industry.

4. Expansion stage of China's optical cable manufacturing from 2001 to 2010

 

In the 21st century, after the development of the optical cable industry has gone through two rounds of low valleys, many mergers have formed an industrial structure dominated by five major groups. At this stage, enterprises not only compete in production capacity, but also strengthen differentiation in new technologies. Zhongtian and Tongguang have obvious advantages in submarine cables and power cables. Changfei and Xite have skeleton cables, and Fiberhome Communications leads the FTTX. Therefore, new technology is constantly being used, and traditional layered optical cables have appeared. The concentric yarn is used to increase the production speed to 70 m/min, which is now the most mainstream cable-forming technology. The sheathed cable has appeared in the sheath, which provides a permanent distinction for the long-term use of the cable. The main features of this period are as follows.

 

4.1 Micro tube type optical cable

 

DRAKA proposed that the air-blowing microcable was originally a concept, but with the development of the access network, the era of micro-cables began. This kind of system engineering using pre-laying pipelines with air-blowing construction technology is obvious in urban network construction. Advantage

 

The key technology of this structure for the cable technology is the reduction of the casing size. The size of the 12-core fiber casing is 1.6 mm, which has high requirements for equipment control accuracy. Therefore, the process technology for producing UV fiber bundles on the strip line was developed. The UV-curable material was used to protect the fiber of up to 12 cores by half-sacking, and the outer diameter of the 12-core bundle was 1.3 mm. Technology can be used not only for air blowing micro-cables, but also for FTTH access.

 

FiberHome Communications currently produces 4, 6, 8, and 12 core UV units and passes high and low temperature cycle tests. Based on this structural unit, various forms of new structural cables can be developed, which can be central tubular multi-beam structures. It can also be a butterfly multi-core cable, which is widely used.

 

4.2 FTTX butterfly cable

 

The driving force of optical communication in the 21st century comes from FTTX, 3G, and multi-network convergence. In fact, it is the last 100 meters of fusion application. Under this driving force, with reference to Japanese construction experience, Chinese companies have developed access networks. Butterfly cable.

 

The appearance of the butterfly fiber optic cable is different from the previous design idea. It is the technical route of the bare fiber direct sheath. It is designed based on the requirements of the last 100 meters of the access network. It has the form of pipeline, overhead, pipeline introduction, etc. It is colored, sheathed or some need to be protected by aluminum tape. The tensile and temperature tests for the cable are different from ordinary cable, and the combustion characteristics and environmental safety factors are considered.

 

The difficulty of this structure lies in the control of fiber loss, the control of the size of the cable structure (cooperating with the quick connector), and the latest requirement is that the surface friction coefficient is small, which facilitates the construction of multiple cables in one pipeline.

 

4.3 Indoor soft cable

 

The traditional indoor optical cable is mainly fiber optic cable for jumper and optical cable for short-distance building connection. However, after the start of FTTX, the type of optical cable in the building began to increase, and there are branch optical cables and wiring optical cables.

 

These optical cable processes are based on tight-fitting technology. The materials are PVC, HYTREL, PA, LSZH, etc., which are quite different from the previous loose-sleeve process, and have various requirements for peeling.

 

 

 

4.4 Fiber optic cable with independent intellectual property rights

 

In the 21st century, there are many new applications and new products for various optical cable factories. Here are a few varieties that have independent intellectual property rights and represent the latest technology of Chinese products:

 

4.4.1 Photoelectric hybrid optical cable, designed to solve the communication point where the power is difficult to connect, the wire and the optical fiber are combined in one cable, and the structure adopts the layer twist design, but due to the power cord in it, the structural size changes. Large, the feature also adds part of the power cord.

 

4.4.2 Rain (sewage) water pipeline cable is designed to use pipeline resources to develop new routes. It combines the characteristics of ADSS and GYTA in structure, and adopts self-supporting frame on the upper wall of the pipeline for use in moisture protection. Aluminum belt protection.

 

4.4.3 Optical cable for 3G outdoor equipment connection is designed to solve the problem of direct connection between BBU and RU. It solves the one-time connection between indoor equipment and outdoor equipment. It can be directly applied after the joint is made in the factory. The structure adopts a tight sleeve structure, and the outer sheath is made of TPU material.

 

4.4.4 Small-structure discrete fiber-optic skeleton cable, designed to solve the application of multi-core number of small pipes in the access network.

 

4.4.5 Pavement-slotted fiber optic cable is designed to lay the fiber optic cable under the slotted construction method to solve the problem of cement pavement access in some communities. Interestingly, in some countries, the cable is laid along the road and is clearly defined. Construction plan.

 

5, summary

 

The change of cable structure is driven by the application. In the first decade, the long-distance trunk line construction, the number of optical fiber cores is small, the structure is relatively simple, and the layered cable has appeared, which has driven the beginning of equipment manufacturing and material manufacturing industries. In the second decade, the construction of metropolitan area networks and mobiles has brought about a qualitative change in China's optical cable industry. Equipment manufacturing and materials have grown and developed. In the third decade, access networks and 3G construction have flourished. The network integration is in the ascendant, the upstream and downstream basic industrial chain has been completed, and the optical cable structure has changed a variety. As a technical management personnel who have been engaged in the manufacture of optical cable for a long time, reviewing the development route of optical cable technology in the past, just like the spiral ladder, every new technology is It is a new radiance that is renewed in old technology. Every leap-forward breakthrough is a qualitative change in the amount of accumulation in the past.