Mechanical Splicing vs. Fusion Splicing: Which Is Right for Your Fiber Optic Needs?

Written by Dave Harris, trueCABLE Technical Specialist, BICSI INST1 Certified and Ben Hamlitsch, trueCABLE Technical and Product Innovation Manager RCDD, FOI

Fiber optic cabling is a critical component of modern telecommunications infrastructure, owing to its high bandwidth, reliability, durability, and cost-effectiveness. During the installation of this infrastructure there arise many situations that require the joining of one optical fiber to another in a procedure called “splicing.” There are two main methods of splicing: mechanical splicing and fusion splicing. This blog will delve into the nuances of each method, comparing their costs, labor efficiency, network performance, and more, to help you decide which splicing technique is best suited for your needs.

Why splice?

Fiber optic splicing is used to join two optical fibers together so the light energy from one optical fiber can be transferred to another optical fiber. A fiber splice is the permanent connection of two optical fibers. Once the two optical fibers are joined with a splice, they cannot be taken apart and put back together, as they can if you join them using connectors. Fiber splices are typically employed for one of four reasons: to repair a damaged cable, extend the length of a cable, join two different cable types, or attach a pigtail. We'll talk about fiber pigtails later on in the article.

What is a mechanical splice?

Many manufacturers offer mechanical splices. Mechanical spices like the ones shown in the image above are typically permanent; they align the two cleaved optical fibers and hold them in place. Index-matching gel inside the mechanical splice reduces or eliminates any fresnel reflections or losses at the splice connection.

Mechanical splices can be used for both singlemode and multimode fiber cables. Mechanical splices do not outperform fusion splices. However, they can outperform mated connector pairs.  The key advantage of a mechanical splice over a fusion splice is the low cost of the equipment required to perform the mechanical splice.

The assembly tool that holds the optical fibers and the mechanical splice is relatively inexpensive when compared to the price of a fusion splicer. However, the actual mechanical splice costs considerably more than the protective sleeve required for a fusion splice.

Steps to Perform Mechanical Splicing

Step 1: Fiber Preparation: Protective coatings, jackets, tubes, strength members, and other materials should all be removed, leaving only the naked fiber visible. The most important consideration is hygiene.

Step 2: Fiber Cleaning: It’s time to clean the raw fiber after it’s removed from its shell. The glass can be kept clean by wiping it with fiber optic cleaner and lint-free wipes. 

Step 3: Cleaving the fiber: The process is comparable to fusion splicing cleaving; however, the accuracy of the cleave is less crucial.

Step 4: Joining fibers mechanically: This approach does not use heat. Simply place the fiber ends in the mechanical splice device and splice them together. Light coupling from one fiber end to the other will be aided by the index matching gel in the mechanical splice equipment.

Step 5: Fiber Protection: The final mechanical splice acts as its own splice protector.

Advantages of Mechanical Splicing

• Mechanical splices do not require electricity.
• Other than a fiber stripper and a fiber splitter, many mechanical fiber splice designs require no additional equipment.
• Mechanical splicing is useful in cases where fusion splicing is not conceivable or practical. This makes them perfect for short-term connections.

Disadvantages of Mechanical Splicing

• Mechanical splices create more signal loss. The insertion loss is much higher. The normal insertion loss of a mechanical splice is about 0.2 dB, which is much greater than the 0.02 dB loss of a standard fusion splice. Multimode fibers are usually spliced ​​mechanically.
• Mechanical splices struggle to meet the alignment tolerances of single mode fibers.
• Mechanical splices are only used under relatively safe conditions, such as in an office building.

What is Fusion Splicing?

Fusion splicing uses a high-voltage electric arc between two electrodes to heat and melt the fiber ends together. This creates a permanent splice that is very fragile and must be protected from the outside environment and bending. This is typically accomplished using heat-shrink tubing and a small metal rod commonly referred to as a protective sleeve. Prior to performing the splice, the optical fiber is passed through the center of the protective sleeve, and the sleeve is positioned so it will not interfere with the fusion splicing process. After the fusion splices are successfully completed, the optical fiber is removed from the fusion splicer, and the protective sleeve is positioned directly over the splice area. The protective sleeve is then placed in an electric oven that is typically built into the fusion splicer. The oven heats the tubing, shrinking it around the fusion splice.

Fusion splicers are more expensive than the assembly tools required for mechanical splicing. However, they provide the lowest-loss fiber splice possible. In addition, fusion splices do not produce Fresnel reflections. Fusion splicing is the most accurate and durable method for joining two optical fibers. After the optical fibers are stripped and cleaved, they are placed into the fusion splicer, where the two optical fibers are aligned between two electrodes. Depending on the fusion splicer used, several alignment techniques are used to align the fiber optic cable. 

Fusion splicers on the market today typically feature a display that allows you to see the optical fibers on two different axes. The cameras in the fusion splicer magnify the optical fibers so that the end faces can be elevated. Most fusion splicers available today also have the ability to approximate the loss of the splice after it is completed.

Steps to perform Fusion splicing

Step 1: Fiber stripping: You must first remove or peel off the protective polymer coating around the fiber optic cable before you can begin fusing it. A mechanical stripping device, similar to stripping pliers, is usually used for this purpose. Remember to clean the stripping equipment before starting the fusing process.

Step 2: Fiber Cleaning: It’s time to clean the raw fiber after it’s removed from its shell. The glass can be kept clean by wiping it with fiber optic cleaner and lint-free wipes.

Step 3: Fiber Cleaving: To make an effective fusion splice, you need a decent cleaver. Instead of cutting the fiber, the chopper knife cuts, pulls, or bends it to cause a neat break, with the end face remaining flat and perpendicular to the fiber axis.

Step 4: Fiber Fusion: After the fibers have been stripped and cleaved, use a fusion splicer to join them together. The ends of the fiber must first be aligned within the splicer. Melt the fibers with an electric arc after they’re correctly aligned, permanently fusing the ends together.

Step 5: Fiber Protection: The splice will not break during typical handling if the fiber is protected from bending and tensile loads. The splice is protected from the weather and breakage by a protective sleeve placed in an electric oven that is typically built into the fusion splicer. The oven heats the tubing, shrinking it around the fusion splice.

Advantages of Fusion Splicing

• Fusion splicing is a compact process and has the lowest insertion loss and back reflection.
• Lower signal loss means higher fiber optic performance.
• Fusion splicing is permanent and has the highest mechanical strength.
• Fusion splicing can withstand a wide range of temperatures.
• Fusion splicing prevents dust and other pollutants from entering the optical path.

Disadvantages of Fusion Splicing

• If too much heat is applied to melt the fiber optic cable for termination, the connection will become brittle and cannot be used for a very long time.
• Fusion splicing causes significant up-front costs for the splicer and additional instruments.
• Fusion splicing cannot be used for temporary connections as it is a permanent connection.

Cost Comparison

One of the most significant differences between mechanical and fusion splicing is the costs of the tools and termination parts required. In general, the tools and equipment required is much higher for fusion splicing than for mechanical connector termination. However, the prices for consumables used in mechanical splicing are usually higher than those used for fusion splicing. Splicing costs per splice are lower for fusion splicing, but the up-front cost is much greater.

Mechanical Splicing Tools

Mechanical splicing systems are relatively affordable, with costs around a few hundred dollars as of this writing. Most of the initial cost is to invest in a quality cleaver, although the quality of fiber cleaving is more crucial in fusion splicing. Other than the cleaver tool, mechanical splicing tools mainly consist of wear components like cable strippers and kevlar shears, which can be replaced as needed.

Fusion Splicing Tools

Fusion splicing systems are considerably more expensive, usually in the neighborhood of a few thousand dollars as of this writing. The high cost is primarily due to the fusion splicer itself, which needs to heat or weld the fiber strands. Additionally, fusion splicers require power, setup time, and periodic maintenance. A high-quality cleaver is also required.

Mechanical Splicing Connectors

Mechanical systems use field-installable connectors and splices to join cables. Many of these connectors utilize a cam-locking system to secure the fiber without damage. These connectors are significantly more expensive than pigtails and cannot be re-terminated.

Fusion Splicing Connectors

In order to splice two segments of fiber together using fusion splicing, all that is needed is a protective sleeve, in addition to the fusion splicer itself. If a connector needs to be installed on the end of a fiber strand, fusion splicing systems usually make use of "pigtails." Pigtails typically cost significantly less than mechanical connectors.

Now, About Pigtails…

What is it that gets spliced onto a fiber optic cable strand or strands? We call it a fiber-optic pigtail. A fiber optic pigtail is a segment of optical fiber with one end terminated with a factory-installed connector and the other end unterminated. As a result, the connector side can be connected to equipment, while the other side is fused in the case of fusion splicing and clamped in the case of mechanical splicing to a network optical fiber cable. Fiber optic pigtails are used to connect fiber optic cables using either fusion or mechanical splicing. We’ve got more about pigtails in our blog post, “What is a Fiber Optic Pigtail, and What Is It Used For?”

trueCABLE Pigtail Solutions

Fiber optic pigtails are a versatile and cost-effective way to terminate your bare fiber cable as well as connect devices and extend the reach of your network. They are easy to install, available in a variety of connector types and lengths, and made from high-quality materials. Pigtails are used in a wide range of applications, including building fiber optic networks, testing and maintenance, data centers, telecom networks, and security systems. We offer a variety of single mode pigtails for your application needs.

Conclusion

Both mechanical and fusion splicing have their advantages and disadvantages. Which of the two splicing methods you choose should depend on your budget, the frequency of installations you will perform, and the specific requirements of your projects. For occasional, small-scale installations, mechanical splicing may be more cost-effective and convenient. However, for high-performance needs and large-scale projects, the superior quality and efficiency of fusion splicing might justify the higher initial investment.

Fusion splicing does remain the better-performing option, and trueCABLE offers numerous fusion splicing pigtail options when fusion splicing is called for in your fiber optic installation.

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