Application of Optical Fiber Thermal Shrinkage Tube in Optical Fiber Protection

- Oct 12, 2019-

Fiber optic heat shrinkable tube: It consists of transparent heat shrinkable tube, hot melt tube and stainless steel needle (or ceramic rod/quartz rod). The transparent outer layer is convenient to detect whether the connection of the optical fiber joint is correct, so that the optical fiber can be simply and safely assembled, and the optical transmission characteristics of the optical fiber can be maintained after shrinkage, providing strength and protection for the optical fiber joint. It is easy to operate, reliable in performance, and can avoid the damage of optical fibers during installation.

Optical fiber is an important part of optical communication system, which provides the channel of optical signal transmission. Optical fibers are usually composed of core, cladding and coating. The core and cladding are high purity silicon dioxide. Because of the different doping ratio of dopants, the refractive index of the core is higher than that of the cladding, and the loss is lower than that of the cladding. Therefore, the optical energy mainly transmits in the core. The cladding provides reflection surface and optical isolation for the transmission of light, and plays a certain mechanical protection role.

The outermost layer of the optical fiber is a coating layer, which includes a primary coating layer, a buffer layer and a secondary coating layer. Acrylic resin, silicone or silicone rubber are commonly used as primary coatings; buffer layer is usually a filling ointment with good performance; secondary coatings are usually made of polypropylene or nylon and other polymers. The function of the coating is to protect the optical fiber from water and gas erosion and mechanical abrasion, at the same time, it increases the mechanical strength and flexibility of the optical fiber, and plays a role in prolonging the life of the optical fiber.

For permanent optical fiber joints, the usual operation steps are: adjusting the welder sheathing one thermal shrinkable tube per fiber to be connected stripping the coating layer of the optical fiber fabrication of the optical fiber end face thermal fusion of the optical fiber monitoring and evaluation of the connection loss strengthening of the thermal shrinkable protective tube at the joint shrinkage of the remaining optical fiber final measurement.

The stripping operation of the coating before the hot melting of the optical fibers reduces the strength of the optical fibers. Because when the coating is stripped, the surface of the optical fiber glass will be scratched by hard objects. In addition, after the bare optical fiber stays in the air for a period of time, micro-cracks will appear on the surface of the bare optical fiber.

Hot melting of optical fibers also decreases the strength of optical fibers, because there is a high temperature gradient near the joints during hot melting, which causes stress near the joints. In addition, after the joints are jointed, there is no protective coating on the joints, which is very fragile.

In order to restore and increase the mechanical strength of the optical fiber, prevent moisture intrusion and maintain the long-term stability of the optical fiber transmission performance, strengthen the protection immediately after the completion of the optical fiber fusion and passing the test, and seal and strengthen the optical fiber of the joint part with the heat shrinkable protection tube.

When thermal shrinkage occurs, the fibre-optic heat-shrinkable tube, which is pre-sheathed on the fibre, is gently moved to the place where the joint is located, so that the fusion position is located in the center of the heat-shrinkable protection tube. The optical fiber heat shrinkable tube is placed lightly in the heater of the fusion machine, and heated under the condition that the optical fiber is straight. When heated, the heat sink tube is heated and softened, and the heat sink tube is heated and contracted. The optical fiber joint and the reinforcement are wrapped tightly together, so as to achieve the purpose of sealing, fixing and increasing the mechanical strength.