First, let us understand the meaning of the term “splice.” According to Cambridge Dictionary, to splice means to “join the ends of something so that they become one piece.” So in essence, fiber optic splicing is a process used to join two separate fiber optic cables together.

There are numerous use cases for fiber optic splicing. Through splicing, fiber optic technicians can extend the length of the fiber to make it long enough for use in a required cable run. As fiber optic cables are generally only produced in lengths up to around 5km, so when lengthier connections are needed, splicing two cables together becomes necessary.

So when the cable runs are too long for a single length of the fiber, or if there’s a need to join two different types of fibers, such as a 48-fiber cable to four 12-fiber cables, splicing is the answer. Splicing is also used to repair severed fiber optic cables that are buried underground or to rejoin fiber optic cables when inadvertently broken.

While there’s another method of joining fibers known as termination or connectorization, splicing is usually the preferred way to join two fiber optic cables as it results in a lower light loss (attenuation) and back reflection than connectorization.

Moreover, splicing renders a permanent or relatively permanent connection between two fiber optic cables. Some companies do offer fiber optic splices that can be disconnected at will, however, they are typically not meant for frequent connection and disconnection.

In an ideal world, a fiber optic installation would consist of long, continuous cable runs from one place to another. However, in reality, fiber optic splices are inherently necessary and always used when designing, installing, and maintaining a reliable communications network.

The Two Main Methods of Fiber Optic Splicing

With fiber-optic connections becoming increasingly mainstream, the ability to accurately perform fiber optic splicing is becoming more and more important. As of now, fiber optic splicing can be carried out using one of two methods: fusion splicing and mechanical splicing.

Before moving forward with a fiber optic installation, it is vital for integrators to have a fairly good understanding of both methods. This would help determine which technique will work best for your company’s long-term goals and fit your performance and budget requirements.

Method #1 – Mechanical Splicing

This fiber optic splicing technique involves the precise alignment of two fiber optic cables, held in place by a self-contained assembly rather than a permanent bond. A mechanical splice is designed to hold two fiber cables in a way that allows light to pass through seamlessly, with a typical loss of around 0.3 dB or 10%.

In this process, the technician must use an alignment device along with an index matching gel. The gel must have a similar refractive index to enhance the light transmission across the joint, with minimal back reflection.

Method #2 – Fusion Splicing

The other method to join two fiber optic cables together — and this time we’re talking a permanent connection — is fusion splicing.

In this technique, a machine or an electric arc is used to produce heat and fuse/weld glass ends that are precisely aligned together for continuous transmission of light. This translates to a much lower attenuation of around 0.02 dB.

Fusion splicing produces a reliable joint with low insertion loss and nearly zero back reflection when done correctly, and thus, is more widely used than mechanical splicing. For example, it’s used in long high data rate connection lines that, once installed, are unlikely to be modified.

Mechanical Splicing vs. Fusion Splicing

One major reason for choosing a particular method over the other is budget.

Mechanical splicing has a low initial investment but costs more per splice. Whereas the cost per splice for fusion splicing is lower but the initial investment is much higher, starting at ten times higher than mechanical splicing, based on performance requirements and features of the fusion splicing machine used.

Talking about performance, the decision comes down to the project you are working on. As outlined earlier, fusion splicing produces much lower loss and back reflection than mechanical splicing, so if you need a permanent joint with minimal attenuation, fusion splicing is the heftier investment you’re looking at.

Also, fusion splices are generally used with single-mode fiber while mechanical splices work with both single and multi-mode fiber.

All things considered, mechanical splicing works well only for quick restoration and temporary connections where a somewhat notable loss is acceptable. Fusion splicing, though costlier, is far more popular as it provides the lowest insertion loss, back reflection, and the strongest joint between the fibers.