29th April 2024 - - 0 comments
Splice it Right – Cold Cure vs. Fusion Splicing

Offering virtually unlimited bandwidth and suitable for any environment, fibre optic cabling has become an effective solution for data and network communications. With its ability to stretch beyond the 90-metre maximum cable length of a copper structured cabling system, fibre optic cabling makes point to point connectivity simple when linking server rooms and localised networking equipment to sites with multiple communication cabinets and other remote areas.

Whether it is used as a vertical backbone or to link buildings across a campus, fibre optic cabling is typically installed and presented into a patch panel, where fibres are terminated by either a fusion splicer or mechanical splice using an adhesive, commonly known as cold cure.

Cold Cure (Mechanical Splicing)

The cold cure method, also known as mechanical splicing, involves the combination of anaerobic adhesive and activator. It requires specific connectors to facilitate the curing process, ensuring a secure and durable bond between the fibre optic cables without the need for heat sources or specialised equipment.

Fusion Splicing

Fusion splicing is the most widely used technique of fibre termination. It uses an electric arc to weld two optical fibres together to create one seamless connection. Typically terminated onto splice-on pigtails with factory-installed connectors, fusion splicing has quickly grown to be the most popular and preferred choice for fibre termination.


While the cold cure method if the oldest, is still yet very common with toolkits more affordable compared to fibre fusion splicers. It can be a budget friendly alternative for installers, with minimal equipment required and less upfront cost if working on a small budget.

Because of the upfront investment required to buy a fusion splicing machine, it may seem that fusion splicing is more costly compared to cold cure. However, over the long term, fusion splicing can actually be less expensive and cost significantly less per splice.

When performing multiple cable splices, fusion splicing proves to be much more cost-effective per splice: typically, between £0.25 - £1.20 per splice. This is because connectors are less expensive and require less frequent replacement since optical fibres are fused together using heat rather than being mechanically joined. In contrast, mechanical splicing aligns fibre ends within the splice using gel or epoxy without using heat or electricity, which can lead to eventual breakage of mechanical components inside the connector or splice.

Performance & Reliability

Offering the lowest signal loss and least reflectance, fusion splicing has proven to be the strongest and most secure method of fibre termination compared to other termination techniques. When accurately performed, a fibre splice can yield a loss of less than 0.1 dB. With insertion loss being the main performance parameter needed to certify a fibre link, and high-speed 40 and 100 Gig fibre applications having more rigorous loss allowance, fusion splicing has become the most widely used method of fibre optic termination.

With the optical fibres being permanently fused together as opposed to using epoxy or adhesive, fibre splicing provides long-term reliability and is more robust due to there being no mechanical parts involved. Fusion splices are capable of withstanding various environmental conditions and are less susceptible to temperature changes, moisture, and vibrations, making them ideal for outdoor installations and in areas prone to harsh weather conditions.

Typically, cold cure terminations result in higher insertion loss (IL) – between 0.2 dB and 0.75 dB. This refers to the amount of signal loss that occurs at the connection point as the two fibres are simply aligned and not physically joined.

Another consideration is that cold cure terminations are considered to be a lot less reliable over the long term. The connection can be more susceptible to environmental factors, such as temperature changes or vibrations, leading to potential signal disruptions.

Achieving consistent results with cold cure terminations can be challenging, especially for inexperienced engineers. Since the process in under manual control, this method can be less predictable and variations in curing times, scribing and cleaving techniques may lead to inconsistent quality and performance.

Versatility & Speed

Although fusion splicing devices are proven to provide a higher quality splice, there are instances where you may opt for the cold cure method due to time constraints, especially if it’s in a challenging area where using a fusion splicing device might be cumbersome.

For example, cold cure terminations can be particularly valuable when working in hazardous or controlled environments such as chemical plants or those prone to flammable conditions. Its adaptability not only enhances safety whilst on site but also makes it a desired choice for fibre optic termination in potentially high risk or customer sensitive scenarios.

However, with the use of bucket trucks and splicing tents that offer protection from the elements and an improved workspace, fusion splicing remains the preferred choice for ensuring high-quality splices whenever feasible. 

State of the Art Technology

Modern fusion splicers have become more automated and user-friendly. They often feature intuitive touchscreen interfaces that guide the operator through the splicing process step-by-step. This automation reduces human error and makes splicing accessible to technicians with varying levels of expertise.

Some fusion splicers incorporate visual inspection tools to verify the quality of the splice post-fusion. This can include checking for cleave quality, assessing the integrity of the splice point, and identifying potential issues like airgaps or contaminants.

Fusion splicers generate detailed reports on each splice, including splice loss data, environmental conditions, and splice images. This documentation is valuable for quality assurance, troubleshooting, and maintaining network standards.

What Method Should I Choose?

When comparing the two methods, it is evident that fusion splicing far outweighs cold cure. This is because fusion splicing, as implied by the name, actually permanently fuses the two the two cables together, whereas cold cure does not undergo permanent joining and instead the cables are held together in such a way (epoxy/adhesive) that light can pass from one fibre to the other.

While cold cure doesn’t require a large upfront investment in tools and equipment, it does have a higher variable cost per splice, where instead fusion splicing has a higher initial investment due to having to purchase a fusion splicer device but does offer a lower variable cost per splice.

In summary, fusion splicing is recommended for critical, permanent installations where performance and reliability are key. Cold cure terminations are a practical choice for short-distance or temporary connections that require quick deployment and flexibility.

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