Detailed Explanation of Fiber Distribution Box Welding Process

The fiber distribution box welding process involves precise mechanical assembly of the box and high-quality optical fiber splicing to ensure secure, efficient, and protected fiber connections.

Mechanical Welding of the Distribution Box

The first step in the process is the mechanical welding and assembly of the distribution box shell. The welding must be firm, with uniform and smooth seams, free from defects such as welding skin, air holes, or incomplete penetration. Bolt connections should include flat and spring washers, with 2–5 threads exposed to ensure secure fastening. The edges and openings of the box must be flat, smooth, and free of burrs or cracks. For non-floor type boxes, two lugs are welded at the lower left and upper right corners using 40x4 mm flat steel, 10 cm in length, to provide mounting points and structural stability. The steel plate thickness for the box body should be at least 1.5 mm, with doors and back plates thicker for durability, ensuring the box can withstand environmental and mechanical stress .

Optical Fiber Preparation

Before welding fibers inside the box, the optical fibers must be carefully prepared. This includes selecting the correct cable length to avoid tension or excess slack, stripping the protective coating, and cleaning the fiber to remove dust or debris. Proper preparation ensures high-quality splices and prevents signal loss .

Fiber Welding (Fusion Splicing)

The fusion splicing process is the standard method for connecting optical fibers inside the distribution box. Steps include:

1. Aligning the fiber ends precisely using a fusion splicer.
2. Heating the fiber ends with an electric arc to fuse them together.
3. Inspecting the splice for uniformity and minimal signal loss.
4. Protecting the splice with a heat-shrink sleeve or protective element inside the box to prevent mechanical damage and environmental exposure . Mechanical splicing is an alternative but is less durable and has higher signal loss compared to fusion welding.

Cable Management Inside the Box

Once fibers are welded, they are routed and organized within the distribution box. This involves:

• Using fiber discs, trays, or guides to store excess fiber length safely.
• Securing fibers with cable ties or movable clamps to prevent tension or bending.
• Ensuring the fiber path allows the front panel to be pulled out without stressing the cables, typically requiring a minimum slack of around 31 inches for trunk cables .

Sealing and Protection

The distribution box must maintain environmental protection. Reserved inlet and outlet holes should have sealing accessories to meet three-level sealing requirements, preventing dust, moisture, and mechanical damage. Insulation is required between metal components and the box shell to protect fibers and maintain safety .

Summary

The fiber distribution box welding process combines mechanical assembly and optical fiber fusion splicing. Key points include:

• Firm, defect-free welding of the box shell.
• Proper preparation and cleaning of optical fibers.
• Precision fusion splicing with protective sleeves.
• Organized fiber routing and slack management.
• Sealing and insulation to protect fibers and ensure long-term reliability. Following these steps ensures efficient, durable, and safe fiber optic connections suitable for FTTH, FTTx, and other telecommunication applications .