In this article, HUNAN GL will explain to you the drawing process of ADSS optical fiber cable:
1. Bare fiber
The smaller the fluctuation of the outer diameter of the ADSS optical fiber fiber, the better. The fluctuation of the fiber diameter can cause the back-scattering power loss of the fiber and the loss of the fiber connection. The fluctuation of the outer diameter of ADSS optical fiber causes the fluctuation of core diameter and mode field diameter, which leads to the increase of fiber scattering loss and splicing loss.
It is better to control the fluctuation of the outer diameter of the fiber within ±1μm. Increase the drawing speed, properly reduce the drawing temperature, and reduce the residence time of the preform in the high-temperature furnace. Reducing the diffusion of moisture in the cladding to the new area is beneficial to reducing the additional attenuation of fiber drawing. Increasing the drawing speed and increasing the drawing tension can reduce the fluctuation of the outer diameter, and also help to reduce the occurrence of E' defects. It is also beneficial to increase the strength of the optical fiber. However, high-speed wire drawing requires higher furnace temperature heating power, and it is easier to produce uneven temperature field. It will have a greater impact on the warpage of the optical fiber (the warpage refers to the radius of curvature corresponding to the bending of the bare optical fiber without any external stress). The main reason for affecting the warpage is that the fiber is heated unevenly in the temperature field, resulting in different shrinkage of the fiber in the neck direction, resulting in a decrease in the warpage of the fiber. The warpage of optical fiber is one of the indicators that ADSS cable users are more concerned about, especially in ribbon fiber, if the warpage of optical fiber is too small, it will bring bad consequences to the connection.
Because the high-speed drawing furnace for ADSS optical cable and optical fiber has the following basic requirements:
A. Design ideal temperature zone distribution and gas path design to produce ideal preform neck shape.
B. The furnace temperature is stable and adjustable, which is convenient for precise control of wire drawing tension.
C. Furnace component selection and air flow design to ensure that the surface of the optical fiber is as little as possible contaminated.
Therefore, by improving the structure of the wire drawing furnace components, and improving the air flow process in the furnace. and get the following result:
A. Control the change amplitude of the F diameter of the ADSS optical cable fiber in the drawing process to about 0.3 μm.
B. The warping degree of ADSS fiber optic cable is controlled above 10m
C. The attenuation characteristics of each wavelength of ADSS fiber optic cable are good
2. ADSS fiber optic cable coating
Coating is a very important special process in the production of ADSS optical fiber, and the quality of the coating has a great influence on the strength and loss of the optical fiber. The bare optical fiber enters the mold at high speed and is pulled into the coating liquid. Since the optical fiber itself has heat, the viscosity of the coating on the top of the mold is lower than that in the coating tank. This difference in viscosity between the paints creates a pressure differential that pushes the paint upwards. A certain coating pressure is used to keep the coating liquid level in the mold stable. If the temperature of the bare optical fiber is too high (increase the drawing speed), the balance of the coating liquid level will be out of control, making the coating unstable and the coating abnormal. Compromises coating quality and fiber performance. A good and stable coating state should include the following aspects:
A. There are no bubbles or impurities in the coating layer;
B. Good coating concentricity;
C. Small coating diameter variation.
In the condition of high-speed wire drawing, in order to obtain a good and stable coating state, it is necessary to keep the temperature of the optical fiber at a constant and low enough level (generally considered to be around 50°C) when it enters the coating die. As the drawing speed increases, the probability of air mixing into the coating during fiber coating increases greatly. At the same time, when drawing at high speed, the drawing tension is also greatly improved. The result of the interaction between the centripetal force generated by the coating die and the drawing tension determines the stability of the coating state. This requires the use of dies that can generate higher centripetal force and a more precise die base inclination adjustment system to ensure coating stability during high-speed wire drawing.
After high-speed drawing of ADSS fiber optic cable, the following phenomenon of poor fiber coating occurred:
A. The diameter of the coating changes greatly during wire drawing and the coating is poorly eccentric
B. There are bubbles in the coating
C. Delamination between coating and cladding
If the coating is not well cured, the coating can be optimized through the following process improvements and equipment adjustments:
A. In view of the large change in coating diameter, optimize the coating process, and finally make the coating diameter change amplitude and coating concentricity reach the ideal state
B. In view of the bubbles in the coating, optimize the cooling device and improve the cooling efficiency, so that the bare optical fiber can achieve uniform and effective cooling during the production process.
C. For poor curing of the coating and delamination between the coating and the cladding. The UV curing system after optical fiber coating has been improved to achieve excellent air tightness; the positioning of the modified system ensures the position of the optical fiber when it is cured in the UV curing quartz tube.
After the improvement of relevant process parameters and facilities above, excellent coating quality has been obtained to ensure the stable and reliable performance of fiber.