Fusion Splicing Explanation and How it Works

Fusion splicing is a technique used in telecommunications and other fields involving optical fibers, where two fibers are joined together by welding or fusing their ends. This process is generally used in fiber optic cables to ensure a seamless flow of data, and is known for being a very precise and efficient method of splicing. The process is undertaken using a fusion splicer, a specialized instrument designed to splice optical fiber.

The primary goal of fusion splicing is to connect two fibers together in such a way that light passing through is not scattered or reflected, but travels smoothly from one fiber to the other with minimal loss. This makes fusion splicing an optimal method when very low signal loss and high reliability are required.

The process of fusion splicing generally involves several steps:

• Preparation: The optical fibers to be joined are first prepared by removing the protective coating on the ends of the fibers. This process leaves the glass of the fiber exposed.
• Cleaving: Once the protective coating is removed, the ends of the fibers are precisely cut, or ‘cleaved’. The cleave must be precise and clean to ensure a successful fusion splice. The cleaved fiber ends should be mirror-smooth and perpendicular to the fiber axis.
• Alignment: The cleaved fiber ends are then placed into the fusion splicing machine. The machine aligns the fiber ends together. This alignment can be done either manually by the operator or automatically by the machine.
• Fusion: Once the fibers are aligned, the splicer generates an electrical arc that creates enough heat to melt the ends of the two fibers. As the fiber ends begin to melt, they are automatically pushed together by the splicer, causing the fiber ends to fuse together. The result is a single continuous optical fiber.
• Cooling and Protection: After the fiber ends have been fused together, the splice needs to cool before it can be handled. Once cooled, the splice is often protected using a heat-shrinkable tube or protective sleeve to provide mechanical strength at the splice joint and to protect it from the environment.

The fusion splicing process is typically controlled by a computer within the splicer machine, which ensures precision and repeatability. The quality of the splice is critical to the performance of the optical fiber link, and modern fusion splicers are able to achieve very low loss splices, typically less than 0.1 dB.

Types of Fusion Splicing Methods

There are primarily two types of fusion splicing methods: single fiber fusion splicing and ribbon fiber fusion splicing.

• Single Fiber Fusion Splicing: This is the most common type of fusion splicing and as the name implies, it involves splicing single fibers to each other one at a time. This method is typically used in situations where you are dealing with singlemode fibers. Single fiber fusion splicing is ideal for restoration and for constructing the final splice in a network link where there may not be an exact number of fibers to make a ribbon.
• Ribbon Fiber Fusion Splicing: Ribbon splicing is used when mass splicing (i.e., splicing multiple fibers together at the same time) is desired, typically in high fiber count cables and for high volume splicing needs. A ribbon fiber cable can have up to 12 or more fibers grouped together in a ribbon. A ribbon fusion splicer can splice all the fibers in the ribbon simultaneously, making it much faster when dealing with high fiber counts. This is usually more cost-effective and time-efficient for larger installations or data centers.

Both types have their strengths and weaknesses. The method chosen for a particular job will depend on the nature of the job (number of fibers, singlemode vs multimode, etc.), the equipment available, and the skills and training of the technicians doing the work.

What is Fusion Splicing Used for?

Fusion splicing is used in several industries where optical fiber connections are essential. This method is chosen for its high performance and reliability in joining optical fibers. Here are some specific applications and industries:

• Telecommunications: In the telecom industry, fusion splicing is widely used to achieve reliable long-distance signal transmission. The low signal loss of fusion splicing makes it an ideal choice for long-haul networks, fiber-optic backbone networks, and submarine cables.
• Cable Television Networks: Cable TV companies use fiber optics for signal transmission, and fusion splicing is often used to join these fibers due to its low signal loss and high reliability.
• Internet Service Providers: ISPs often use fusion splicing when setting up their fiber-optic networks. Especially in Fiber To The Home (FTTH) installations, fusion splicing is used to ensure a high-quality connection.
• Data Centers: Data centers require high-speed and reliable connections, and thus they often rely on fiber optics. Fusion splicing is used to create these fiber-optic links with minimal signal loss.
• Medical and Biomedical Industry: Fiber optics are used in various medical instruments and biomedical research tools. Fusion splicing is often used to create precise, reliable fiber connections in these devices.
• Research and Development: Fusion splicing is used in research settings, especially those involving fiber optics, communications, and photonics research. This includes academic research institutions, government labs, and private sector R&D departments.
• Aerospace and Defense: In applications where high-speed data transmission is required, like satellite communication and defense communication systems, fusion splicing is used for its reliability and high performance.
• Oil and Gas Industry: Fiber optics are used for sensing and communications in harsh environments such as oil and gas wells. Fusion splicing is used to create robust connections that can withstand these harsh conditions.

In general, any industry or application that requires the high-speed and high-capacity data transmission provided by fiber optics may utilize fusion splicing to achieve reliable and efficient connections.

Comparison Between Fusion Splicing and Mechanical Splicing

There are other methods for joining optical fibers besides fusion splicing. One of the most common alternatives is mechanical splicing.

Mechanical Splicing

Unlike fusion splicing, mechanical splicing doesn’t involve the use of heat to melt and join the fiber ends. Instead, it precisely aligns the two fiber ends and holds them together using a special housing. The housing is designed in such a way that light can pass from one fiber to the other with minimal loss.

Mechanical splices are typically quicker to install than fusion splices, as they don’t require time to heat and cool. They also don’t require expensive fusion splicing equipment. However, they tend to have higher loss and higher back reflection than fusion splices, which can impact the performance of the fiber optic link. Mechanical splices are often used for temporary connections or in situations where fusion splicing equipment is not available.

Advantages:

• Speed: Mechanical splices can be installed more quickly than fusion splices, making them a good choice when time is of the essence.
• Lower Initial Investment: Mechanical splicers are typically less expensive than fusion splicers, making them more accessible for smaller operations or for those who do not splice fibers frequently.
• Ease of Use: Mechanical splicing requires less skill than fusion splicing, which can make it a more viable option in some situations.

Disadvantages:

• Higher Loss and Back Reflection: Mechanical splices generally have higher signal loss and back reflection than fusion splices, which can impact the overall performance of the fiber optic link.
• Less Robust: Mechanical splices are generally less robust than fusion splices and can be more susceptible to variations in temperature, humidity, and other environmental conditions.
• Ongoing Costs: Mechanical splices require consumables that contribute to the ongoing cost per splice.

Fusion Splicing

Advantages

• Low Loss and Back Reflection: Fusion splicing provides the best performance in terms of signal transmission. The resulting splice has lower signal loss and less back reflection than a mechanical splice.
• Permanent and Reliable: Fusion splices are permanent and provide a high degree of reliability. They are also highly resistant to changes in temperature, humidity, and other environmental conditions.
• Cost-Effective for High Volume: Although the initial cost of a fusion splicing machine can be high, the cost per splice is lower than mechanical splicing when dealing with high volumes of fiber.

Disadvantages:

• High Initial Cost: Fusion splicers can be quite expensive, which can be a barrier for smaller operations.
• Skill Requirement: Operating a fusion splicer requires skilled technicians, as the process of preparing the fiber for fusion splicing can be delicate and complex.
• Time-Consuming: Fusion splicing generally takes longer than mechanical splicing, particularly when dealing with single fibers.

Another method of joining optical fibers is by using connectors. Connectors allow fibers to be easily connected and disconnected from equipment or other cables. Connectors also align the fiber ends and hold them together, similar to mechanical splices. They’re often used where flexibility is needed, such as in patch panels or equipment interfaces. However, connectors usually have higher loss than either fusion splices or mechanical splices. They also require more maintenance, as the end faces of the connectors need to be regularly cleaned to ensure optimal performance. Despite these disadvantages, the flexibility offered by connectors makes them essential in many fiber optic systems.

Connectors may be more suitable for situations where flexibility and ease of use are priorities, while splicing methods may be more appropriate when you need the lowest possible signal loss and the highest reliability. Each method has its strengths and weaknesses, and the choice between them depends on the specific requirements of the installation, such as the necessary performance level, the available equipment, and the skills of the technicians.

Few Examples of Fusion Splicing’s Equipment

There are several products used in the fusion splicing process. Here are some examples:

Fusion Splicers: These are the primary machines that perform the fusion splicing. Notable examples include:

• Fujikura 90S: This is a core alignment fusion splicer known for its high performance and reliability.INNO View 7: This is another high-quality core alignment splicer that offers high precision and durability.
• Sumitomo TYPE-81C: This is a compact, fast, and robust core alignment splicer.

Cleavers: These tools are used to make precise ends on fibers before they are spliced. Some notable examples include:

• Fujikura CT50: This cleaver provides high-quality cleaves and can be used with a wide range of fibers.
• Sumitomo FC-6S: This is a precision fiber cleaver that’s known for its durability and ease of use.

Splice Protection Sleeves: These are used to protect the splice once it’s made. Examples include:

• Sumitomo B-40: These are heat-shrink splice protector sleeves that provide robust mechanical strength and environmental protection for the splice.
• FITEL S179 Fusion Splicer: This is a high-end, core alignment fusion splicer that is designed for speed and precision. It can handle a variety of fiber types, including singlemode, multimode, and specialty fibers.

Cleaning Supplies: These are used to clean the fiber ends before splicing. Some examples include:

• Sticklers Fiber Optic Cleaning Kit: This kit includes everything you need for cleaning fiber ends, including cleaning fluid, cleaning swabs, and lint-free wipes.
• Viavi FiberChek Sidewinder: This is a handheld inspection and cleaning tool that allows for automated inspection and analysis of fiber end faces, ensuring they are clean and free of defects before splicing.

Please note that the specific choice of equipment and supplies can vary depending on the specific requirements of the job and the type of fiber being spliced. Always refer to the manufacturer’s instructions and specifications when selecting and using fusion splicing equipment and supplies.

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