Fusion Splicing Basics

Although most people in the Fiber Optic Community know what Fusion Splicing is and its applications. Let us take a step back and understand that we may have a few novices out there or just individuals interested in knowing how it works. First things first lets outline some of the other terms for fusion splicing.

1. Fibre Splicing
2. Fiber Optic Fusion Splicing
3. Fiber Splicing
4. Optical Fiber Fusion Splicing
5. Fusion Splicing and the list can go on for days. Bottom Line they mainly mean the same thing

Definition: Fusion Splicing is a welded joint formed between two optical fibers. Fusion splicing is a permanent, low-loss, high-strength joint compared with other temporary joint such as a mechanical splice. Optical fiber fusion splices play a crucial role in the optical network.

Goals of Fusion Splicing:

1. Create a joint with little dB loss
2. Form great mechanical strength
3. create bond between new fiber and existing fiber

Why is  fusion splicing is more efficient than fiber optic connectors and mechanical splicing?

Mechanical Splicing is a semi-permanent way of joining two fibers together. Usually with a metal or plastic crimp. This is not a permanent bond since you are using a connector to connect the two ends. Mechanical splicing doesn’t need costly capital equipment to work, but it does require higher consumable costs. So for organizations that don’t make a lot of splicing, mechanical splicing is the best choice. It is also best suited for emergency repairs.

Fusion Splicing we already spoke about the definition of this so lets jump into some major advantages!

1. Fusion splicing is very compact
2. Fusion splicing has the lowest insertion loss
3. Fusion splicing has the lowest back reflection (optical return loss ORL)
4. Fusion splicing has the highest mechanical strength
5. Fusion splicing is permanent
6. Fusion splicing can withstand extreme high temperature changes
7. Fusion splicing prevents dust and other contaminants from entering the optical path

Types of Fusion Splicing

Fusion splicing environment and applications can be roughly divided into three types: 1. Field splicing 2. Factory splicing and 3. Laboratory splicing.

An important example of field splicing is the assembly of undersea fiber cables aboard fiber deployment ships. The example of factory splicing could be the assembly of fiber optic passive devices such as a WDM. An example of laboratory splicing is done by researchers fusion splicing the newest developed fibers to test their compatibility with existing industry standard fibers.

Fiber fusion splicing involves concepts from many subjects including optical waveguide theory, heat transfer, material science, mechanical engineering, fluid mechanics and more.

Introduction to the Fusion Splicing Process

The major steps involved in optical fiber fusion splicing can be summarized as the following.

1. Optical fiber stripping

The fiber cable jacket is removed and then the fiber polymer coating is stripped with fiber optic strippers.

2. Fiber cleaving

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

3. Fiber alignment

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

4. Fiber welding

The fibers are then heated with electric arc or other methods to the fiber glass’s softening point and then both fibers are pressed together to form a solid joint.

5. Insertion loss estimation

The insertion loss is estimated based on the fusion quality and dimensions.

6. Pull tension strength testing

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

7. Splice protection with fusion splice sleeve

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

Once again with our Blog if you have anything to add or contribute feel free.  We hope that this will help clear up or refresh your memory on the importance of fusion splicing. We are jumping into 2009 with alot of high hopes for the fiber optic community.

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Special thanks and a Happy New Year to Colin Yao for contributing to this Post!!  Since 1997  Colin Yao has accumulated extensive experience in the fiber optic industry and published over 200 excellent articles for the newcomers to the industry.