How to Choose Your Fiber Termination Method

When it comes to fiber terminations, there are essentially 5 choices and knowing the pros and cons of each can help you decide what’s right for your scenario and your bottom line...

May 1st, 2019
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When it comes to fiber terminations in the data center and telecommunications rooms, there are essentially 5 choices – 4 of which are considered field term since preterminated assemblies are factory pre-terminated on both ends, so there is no field termination taking place. The field-termination options include:

  • Fusion splicing via splice-on pigtails that feature a factory-terminated connector on one end with unterminated fiber on the other that is spliced to incoming fiber
  • Fusion splice-on connectors that use fusion splicing to connect fiber to a fiber stub protruding from a pre-polished connector
  • Epoxy-polish connectors that use adhesive and polishing processes to terminate the fiber to the connector
  • Mechanical splice connectors that use a mechanical crimp and index-matching gel to connect fiber to a pre-polished connector within a ferrule

There are several factors that can influence which fiber termination method will work best for your specific scenario. The applications and equipment interface that you need to support today and tomorrow are probably the number one factor. For example, 40 or 100 Gig require multi-fiber MPO/MTP connectors, which are not available in all termination methods. The number of fiber connections required for the installation will also have a major impact on which termination method you choose – there’s a big difference between 20 fiber connections and 2000 fiber connections.

The level of expertise of your technicians doing the installation is also a factor. Whether they know how to properly strip, cleave, connectorize and polish fiber can play a huge role in which method you choose. It’s important to also consider the tools and consumables required. For example, a fusion splicing machine is required for fusion splicing, and while they have come down in price, this is still an expensive piece of equipment.

How much time you have to plan and deploy before you go live is another consideration. If you’re dealing with a disaster recover situation or the need to go live ASAP, you may not want to choose a method that requires more upfront planning and longer lead times. Following is additional information on the various termination methods to help you choose the right solution for your scenario.

Preterminated Fiber Solutions

Available in multiple fiber types, counts and connector interfaces including multimode and singlemode fiber types and multi-fiber MPO/MTP, LC, SC, ST connector interfaces, preterminated fiber solutions are factory-terminated and tested. Preterminated MPO/MTP solutions also readily support multi-fiber applications like high-speed 40 and 100 Gig that require 8 fibers with 4 transmitting and 4 receiving at either 10 or 25 Gb/s. Pre-terminated multi-fiber MPO/MTP-based solutions are also ideal for high-density, large installations as they save pathway space and allow for quickly termination of large fiber counts.

The main benefit of preterminated solutions is reduced labor and deployment time. Studies have shown that plug-and-play preterminated solutions can be deployed up to 90% faster. They also tend to exhibit the best performance and less variability due to factory termination. And because they are simply plugged in, they require no fiber termination expertise. With less packaging, consumables and onsite waste, preterminated solutions are also considered a greener option.

The main disadvantage with preterminated solutions is the longer lead times since they are made to order. The lengths also must be carefully predetermined – if the assemblies end up too short, this can cause significant delays as you may need to reorder, and assemblies that are too long require slack cable management. Preterminated solutions also carry the highest material cost of all termination methods.

While these solutions do cost more in material, if you can carefully plan your lengths and can handle the longer lead times, the labor savings and faster deployment time can outweigh any material premium. However, they may not be the most cost effective in low fiber count duplex applications, and they are not well suited for disaster recovery or other quick turn-around deployments due to planning and longer lead times. If you do select preterminated solutions, it’s wise to choose from a manufacturer who offers serial numbers on each assembly that are traceable to factory test results. This will help ensure that you’re getting the performance you expect.

Splice-On Pigtails

Splice-on pigtails feature a short fiber stub that protrudes from a pre-polished connector and is fusion spliced to the incoming fiber using an electric arc. Once spliced, the splices are stored in a splice tray and protected via splice sleeves. The process of fusion splicing requires a fusion splicing machine that aligns two cleaved fibers and fuses them together or a mass fusion splicer that simultaneously aligns and fuses 12-fibers in a ribbon cable.

Splice-on pigtails are commonly available in multimode and singlemode and various connector types, including duplex LC, SC and ST, and multifiber MPO/MTP. They may be available in bulk packs that can help reduce waste, and in color coded pigtails per TIA-598C standards to help ensure end-to-end continuity.

Splice-on pigtails offer a low-loss connection, typically around 0.1dB, with the least amount of reflectance. The fused joint is a strong connection, they don’t result in a lot of onsite waste, and there is a low risk of contamination. On average, splice-on pigtails cost less than preterminated solutions but more than other field termination methods, and they have the benefit of not needing to preplan lengths or wait for longer lead times.

However, splice-on pigtails do require an expensive splice machine that requires power and/or battery and maintenance. The performance of these solutions is also highly dependent on the quality of the cleave so a high-quality cleaver recommended. The fusion process also adds time and labor compared to plug-and-play preterminated solutions, and you need to have a decent work space to accommodate the process. There is also the added cost and space required for the splice trays and sleeves.

In general, splice on pigtails are the best option for transitioning from 250µm outside plant to 900µm indoor fiber cable. That’s why you see them used in entrance facilities for incoming fiber – especially in cloud and colocation data centers where there is fiber coming in from various service providers. Splice-on pigtails are also ideal for singlemode fiber applications as multimode can be more difficult to align due to the fiber’s graded index profile and larger core size, especially when using different vendors’ glass.

One of the biggest reasons for choosing splice-on pigtails is that it one of just two viable field-termination options for MPO/MTPs required in multi-fiber applications like 40 and 100 Gig. So, if you don’t know your lengths, or don’t have time to deal with longer lead times but you need MPO/MTP-based connectivity, the splice-on pigtail is a good option.

Fusion Splice-On Connectors

Instead of splicing to a pigtail stub, with splice-on connectors, the stub resides inside the connector. The stub is fusion spliced, and the connector parts are assembled around the ferrule. Splice-on connectors are typically available in multimode and singlemode and various duplex connector types including LC, SC and ST. There are a couple of splice-on MPO/MTP connectors available on the market, but it is not a typical product offering from most vendors.

Like pigtails, splice-on connectors also require a fusion splicing machine to fuse the cleaved fiber to the stub and they offer a low-loss connection with reduced onsite waste. But unlike splice on pigtails, there is no need to for splice trays and protective splice sleeves since the splice is protected within the connector housing itself. It’s important to note that while splice-on connectors can terminate 900µm and 250µm fiber, unlike splice-on pigtails, they cannot be used for splicing the two different fiber types together. And unlike splice-on pigtails, splice-on connectors typically cannot be reterminated.

Epoxy-Polish Connectors

A traditional field termination method that is starting to go by the wayside is epoxy-polish connectors that use a type of epoxy to join the fiber and the connector ferrule. The epoxy is then cured using a variety of curing methods such as heat cured epoxy, UV adhesive, anaerobic or acrylic. Epoxy-polish connectors are available in various duplex connector types, but not available for MPO/MTP-based connectors. The protruding fiber must also be cleaved and polished to ensure smooth flush finish before connecting.

There aren’t a lot of benefits to epoxy-polish connectors other than low material cost. Epoxy-polish connectors are the termination method that require the highest skill set, and experience and expertise in the polishing process can impact performance. Performance is also dependent on quality of the cleave. As such, epoxy-polish connectors are not the best option if you need extremely low loss performance. Average insertion loss is about 0.2 – 0.3dB for those who are experienced, but it could be much higher for those who are not.

Epoxy polish connectors cannot be reterminated, and it is the most time-consuming option with the most amount of scrap. The termination time may only take 15 minutes, but the epoxy also needs time to cure, and that time can range from 30 minutes to several hours depending on the type of curing, such as heat cured, room temp or anaerobic. There is also a higher risk of contamination because the endface is exposed and polished in the field, and more tools and consumables required, depending on the type of curing used. For example, a curing oven is required for heat cured epoxy while a UV curing light required for UV adhesives.

Mechanical Splice Connectors

One of the most popular field termination methods is the use of mechanical splice connectors where two fibers are joined in an alignment fixture using index matching gel. With mechanical splice connectors, the depth of the fiber insertion is determined by stripping off a specific amount of the buffer coating. These connectors are often used in conjunction with a visual fault locator to ensure quality of the termination.

Typically, available in various simplex and duplex connector types in both multimode and singlemode, mechanical splice connectors are usually sold as a manufacturer-specific solution with a manufacturer-specific tool and connectors. They are however not an option if MPO/MTP-based connectivity is a requirement.

Mechanical splice connectors offer a fast field termination, along with the benefit of a factory polished connector and limited waste. Because of their speedy field termination, mechanical splice connectors are ideal for fast deployment, repairs and reconfiguration scenarios. Some manufacturer may also offer a lower-cost termination tool for their connectors with no power or batteries required. Mechanical splice connectors are not very difficult to terminate and can be quickly learned by technicians. There is also a lower risk of contamination for solutions where the dust cap can be left on.

Mechanical splice connectors have a higher loss and reflectance than fusion splice options and preterminated solutions, offering a similar performance to a quality epoxy-polish termination. But they are not as difficult as epoxy polish connectors to achieve this performance. Like all field terminations, the performance is dependent on quality of the cleave so a high-quality cleaver is recommended.

With several mechanical splice termination systems available, there are some key factors to consider, and you need to ensure you’re selecting the right system for bottom line profitability. To help you select the right mechanical splice system, download the white paper, “Selecting the Best Fiber Termination for Bottom Line Profitability.”