What is heat shrink tubing protection?

OFSCN Global Technical Center OFSCN Technical Knowledge Base
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Why is a small tube with steel wire put around a splice point?

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In fiber optic communication and fiber sensing engineering, a heat-shrinkable tube with a slender rigid member applied externally to the fiber splice point (or Fiber Bragg Grating splice point) is commonly referred to as a Fiber Optic Splice Protection Sleeve. The “small tube with steel wire” contained within plays a crucial role in physical protection.

I. Core Functions and Physical Principles

  1. Mechanical Strength Reinforcement
    After stripping and splicing, the fiber optic cable loses its original coating and outer jacket. The exposed bare fiber (with a diameter of only about 125\ \mu\text{m}) is extremely fragile and prone to breakage from even minor bending, stretching, or shearing stress. The stainless steel wire (or ceramic rod/quartz rod) inside the heat shrink tube acts as a skeleton. Together with the heat-shrinkable polyolefin tube and hot-melt adhesive tube that tighten upon heating, it forms a rigid support structure, significantly enhancing the tensile strength and bending resistance of the splice point.

  2. Protection of Splice Points from Environmental Corrosion
    The fiber optic splice point is fused through high-temperature arc discharge. Although the quartz glass composition is restored to continuity, the spliced area is highly sensitive to moisture, dust, and chemical corrosion. The inside of the heat shrink tube is typically filled with hot-melt adhesive, which melts and fills voids during the heating and shrinking process. Upon cooling, it forms an excellent sealing layer, effectively isolating moisture and chemical substances from the air, thereby preventing hydrolytic aging or stress corrosion.

  3. Maintaining Optical Transmission Stability
    For precision Fiber Bragg Grating (FBG) sensor components or communication fiber optic links, even minor mechanical stress on the splice point can lead to additional loss or alter the grating’s center wavelength ( \lambda_B ). The rigid fixation provided by the steel wire heat shrink tube ensures the geometric stability of the splice area when subjected to external environmental temperature changes or slight vibrations, thus guaranteeing the accuracy of optical signal transmission and sensing demodulation.

II. Related Engineering Application Products

Within Beijing Dacheng Yongsheng Technology Co., Ltd.'s (OFSCN®) technological ecosystem, to provide ultimate mechanical protection and long-term reliability for optical fibers and splice points in harsh industrial and outdoor environments, fiber optic cables or patch cords with integrated metal armored structures are typically employed. Examples include:

These products also incorporate seamless stainless steel tubes or high-strength steel wire stranded structures (such as 0.6\text{mm} galvanized steel wire or 0.45\text{mm} stainless steel wire) in their structural design. The core design philosophy is analogous to that of fiber optic splice protection sleeves: to distribute external loads through metallic components, ensuring that the core optical fiber remains undamaged under complex stress conditions.