The two primary methods for splicing small optical cables are fusion splicing and mechanical splicing, each offering distinct advantages in performance, cost, and application.

Fusion Splicing

Fusion splicing is the most reliable method for joining optical fibers, including small-diameter cables (as small as 250 microns). It involves:

• Stripping and cleaning the fiber to remove protective coatings and contaminants.
• Cleave the fibers perpendicularly using a precision fiber cleaver to create smooth, flat ends.
• Aligning the fibers in a fusion splicer, which uses cameras and precision optics to ensure core-to-core alignment.
• Fusing the fibers with an electric arc, creating a continuous, permanent optical path.
• Protecting the splice with a heat-shrink sleeve to maintain mechanical strength and prevent contamination. Fusion splicing produces ultra-low insertion loss (around 0.02 dB) and minimal back reflection, making it ideal for long-haul networks, data centers, and high-performance applications. Modern fusion splicers can handle single fibers or multiple fibers simultaneously (mass fusion), improving efficiency for larger projects .

Mechanical Splicing

Mechanical splicing is a faster, lower-cost alternative, particularly useful for field repairs or temporary connections. Key steps include:

• Stripping and cleaning the fiber ends.
• Aligning the fibers inside a small mechanical housing or sleeve.
• Using an index-matching gel to bridge the microscopic gap between fiber ends, allowing light to pass with minimal reflection.
• Securing the assembly to maintain alignment and protect the splice. Mechanical splices typically have higher insertion loss (0.2–0.75 dB) and are less durable than fusion splices, but they require no electricity or complex equipment, making them suitable for emergency repairs or short-distance applications .

Considerations for Small Optical Cables

• Precision is critical: Small fibers are more sensitive to misalignment, so careful cleaving and alignment are essential.
• Equipment choice: For permanent, high-performance splices, a fusion splicer designed for small fibers is recommended (e.g., Fujikura FSM-70S or Sumitomo Quantum Q101-M12) to ensure low-loss connections.
• Environmental protection: Use heat-shrink sleeves or protective enclosures to prevent mechanical stress and contamination.
• Testing: After splicing, verify the connection using an optical time-domain reflectometer (OTDR) or power meter to ensure minimal signal loss.

Summary

• Fusion splicing: Permanent, low-loss, high reliability, requires specialized equipment, ideal for long-term installations.
• Mechanical splicing: Quick, cost-effective, suitable for temporary or emergency repairs, slightly higher signal loss, minimal equipment needed. For small optical cables, fusion splicing is generally preferred for permanent installations, while mechanical splicing provides a practical solution for field repairs or situations where fusion equipment is unavailable .