A tapered optical splitter (FBT splitter) works by fusing and stretching two or more optical fibers to form a tapered waveguide, allowing controlled distribution of light between output fibers.

Working Principle

A tapered optical splitter, also known as a Fused Biconical Taper (FBT) splitter, operates on the principle of optical coupling between closely fused fibers. The process begins by removing the coating from two or more fibers and placing them in contact. The fibers are then heated and stretched simultaneously, forming a double-cone or tapered region. In this tapered section, the optical modes of the fibers overlap, allowing a portion of the light from the input fiber to couple into the adjacent fiber. By adjusting the length of the taper, the stretching, and the torsion angle, manufacturers can control the splitting ratio, determining how much light is directed to each output fiber .

Structure and Design

The FBT splitter consists of:

• Input fibers: Carry the original optical signal.
• Tapered coupling region: The fused and stretched section where light is distributed.
• Output fibers: Receive the split optical signals in the desired ratio. The tapered structure ensures that light gradually transfers between fibers, minimizing abrupt losses. The splitting ratio can be equal (50:50) or unequal (e.g., 70:30) depending on the application .

Applications

FBT splitters are widely used in passive optical networks (PONs), including EPON, GPON, BPON, FTTX, and FTTH, where a single optical signal must be distributed to multiple endpoints. They are particularly suitable for small-scale splits such as 1×2, 1×4, or 2×2 configurations due to their cost-effectiveness and simplicity .

Advantages and Limitations

Advantages:

• Low cost for small split ratios.
• Simple manufacturing process.
• Adjustable splitting ratios through taper control. Limitations:
• Less uniform light distribution compared to PLC splitters.
• Sensitive to environmental changes, such as temperature variations, which can affect performance.
• Not ideal for large-scale splits (e.g., 1×32 or 1×64) due to higher insertion loss and uneven power distribution . In summary, the tapered optical splitter uses a fused and stretched fiber region to couple light between fibers, enabling controlled splitting of optical signals for small-scale network applications. Its principle relies on mode coupling in the tapered region, which allows precise adjustment of the output power distribution.