Optical Fiber Fusion Splicing

What is optical fiber fusion splicing?

Optical fiber fusion splicing is a welded joint formed between two optical fibers. Fusion splicing is a permanent, low-loss, high-strength joint in contrast to other temporary joint such as a mechanical splice. Optical fiber fusion splices play a vital role within the fiber optic network.

Benefits of Optical Fiber Fusion Splicing
There are more processes for interconnecting fibers for example fiber optic connectors and mechanical splicings. Compared to both of these, fusion splicing has many advantages as explained below.

  • Very compact
  • Lowest insertion loss
  • Lowest back reflection
  • Highest mechanical strength
  • Permanent
  • Fusion splicing can withstand extreme high temperature changes.
  • Fusion splicing prevents dust along with other contaminants from entering the optical path.

Kinds of Fusion Splicing
Fusion splicing environment and applications can be roughly divided into three types:

  • Field splicing – For example, the assembly of undersea fiber cables aboard fiber deployment ships.
  • Factory splicing – For example, the assembly of fiber optic passive devices like a WDM.
  • Laboratory splicing – A good example of laboratory splicing is performed by researchers fusion splicing the most recent developed fibers to test their compatibility with existing industry standard fibers.

Fusion Splicing Process
Fiber fusion splicing involves concepts from many subjects including optical waveguide theory, heat transfer, material science, mechanical engineering, fluid mechanics and much more. The aim of fiber fusion splicing would be to produce a joint with minimum insertion loss yet with mechanical strength and long-term reliability that matches the fiber itself. The perfect procedure for fusion splicing ought to be fast, inexpensive and should not require expensive equipment. But actually the fusion splicing process needs trade-offs among different applications and requirements. For instance, for undersea telecommunications, long-term reliability is the most important goal for any fusion splicing.

The main steps involved in optical fiber fusion splicing could be summarized because the following.

  • Optical fiber stripping

The fiber cable jacket is taken away and so the fiber polymer coating is stripped with fiber optic strippers.

  • Fiber cleaving

The fiber is cleaved with a specialized tool called fiber optic cleaver. Two types of fiber optic cleaver exist: high precision fiber optic cleaver for single mode applications and field cleaver for multimode applications. One like almost perfect end face is achieved with this cleaving process.

  • Fiber alignment

The fibers are laterally aligned to each other by stepping motor in a fusion splicer. This might involve rotating the fibers in polarization maintaining fiber splicings.

  • Fiber welding

The fibers will be heated with electric arc or any other techniques to the fiber glass’s softening point and then both fibers are pressed together to create a solid joint.

  • Insertion loss estimation

The insertion loss is estimated in line with the fusion quality and dimensions.

  • Pull tension strength testing

The fusion is pull proof tested when opening the fusion splicer cover.

  • Splice protection with fusion splice sleeve

The fusion splice joint is then protected with a heat shrink tube having a steel strength member inside to form a solid and reliable fiber joint.