As Below is the brief introduction the Wire drawing of ADSS fiber optic cable
1. Bare fiber
The smaller the fluctuation of the outer diameter of the ADSS optical fiber, the better. The fluctuation of the optical fiber diameter can cause the backscattering power loss and the fiber splicing loss of the optical fiber. 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 optical fiber scattering loss and splice loss.
It is better to control the fluctuation of the outer diameter of the optical fiber within ±1μm. Increase the wire drawing speed, appropriately reduce the wire 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 generation of E' defects. It is also beneficial to increase the strength of the fiber. However, high-speed wire drawing requires higher furnace heating power, which is more prone to uneven temperature field. It will have a greater impact on the warpage of the fiber (warpage refers to the radius of curvature corresponding to the bending of the bare 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 the optical fiber is one of the indicators that ADSS optical cable users are more concerned about. Especially in the optical fiber, if the warpage of the optical fiber is too small, it will bring adverse consequences to the connection.
Because ADSS optical fiber high-speed drawing furnace has the following basic requirements:
A. Design the ideal temperature distribution and gas path design to produce the ideal preform neck shape.
B. The furnace temperature is stable and adjustable, which is convenient for precise control of drawing tension.
C. The selection of heating furnace components and the design of air flow ensure that the surface of the optical fiber is polluted as little as possible.
Therefore, the structural improvement of the components of the wire drawing furnace and the improvement of the airflow process in the furnace are carried out. Got the following results:
A. The F diameter variation amplitude of the ADSS optical fiber during the drawing process is controlled to be about 0.3 μm.
B. The warpage of ADSS fiber optic cable should be controlled above 10m
C, ADSS optical fiber has good attenuation characteristics of each wavelength
2. Optical fiber coating of ADSS optical cable
Coating is a very important special process in the production of ADSS optical fiber. The quality of the coating has a great influence on the strength and loss of the optical fiber. The bare fiber enters the mold at high speed and is pulled into the coating liquid. Since the fiber itself has heat, the viscosity of the coating on the top of the mold is lower than the viscosity of the coating in the coating tank. This difference in viscosity between paints creates a pressure difference that pushes the paint upwards. A certain coating pressure is used to maintain the stability of the coating liquid level in the mold. If the temperature of the bare fiber is too high (increase the wire drawing speed), the balance of the coating liquid level will be out of control, the coating will be unstable, and the coating will be abnormal. Affects coating quality and fiber performance. A good 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 changes.
Under the condition of high-speed drawing, in order to obtain a good and stable coating state, the fiber must be kept at a constant and sufficiently low temperature (generally considered to be around 50°C) when entering the coating die. With the increase of the drawing speed, the probability of air mixing into the coating when the fiber is coated is greatly improved. At the same time, during high-speed wire drawing, the wire drawing tension is also greatly improved. The interaction between the centripetal force generated by the coating die and the wire drawing tension determines the stability of the coating state. This requires the use of a die that can generate higher centripetal force and a more precise die seat inclination angle adjustment system to ensure coating stability during high-speed wire drawing.
After the high-speed drawing of ADSS optical fiber, the following phenomenon of poor optical fiber coating occurred:
A. The diameter of the coating changes greatly and the eccentricity of the coating is poor during wire drawing.
B, the coating has bubbles
C. Delamination between coating and cladding
Poor coating curing, such as coating optimization through some of the following process improvements and equipment adjustments:
A. In view of the large change of coating diameter, optimize the coating process, and finally make the change amplitude of coating diameter and coating concentricity reach the ideal state
B. For the bubbles in the coating, optimize the cooling device and modify the cooling efficiency, so that the bare fiber can be cooled uniformly and with good effect during the production process.
C. For the poor curing of the coating and the delamination between the coating and the cladding. The UV curing system after coating of the optical fiber is 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 above improvement of relevant process parameters and facilities, excellent coating quality has been obtained to ensure the stability and reliability of ADSS optical fiber performance.
