Fusion splicers challenge mechanical splicing

May 1, 1996
Both publicly and behind the scenes, the players in the telecommunications industry, whether telephone companies, cable-TV vendors or media providers, are scrambling. Publicly they are fighting for a stake in the converging multibillion-dollar entertainment-information industry that will be in transition for years to come. Less visible is the race to beef up their networks with the medium of the future: optical fiber.

Lynn Haber

Both publicly and behind the scenes, the players in the telecommunications industry, whether telephone companies, cable-TV vendors or media providers, are scrambling. Publicly they are fighting for a stake in the converging multibillion-dollar entertainment-information industry that will be in transition for years to come. Less visible is the race to beef up their networks with the medium of the future: optical fiber.

As optical fiber moves deeper into the network, cabling installation and contracting companies of all kinds are reevaluating their businesses and the tools they need to get the job done. For those whose business revolves around optical fiber, a must-have tool is a fusion splicer.

As the name implies, fusion splicers are instruments that make a fusion splice; that is, at the junction where two or more optical fibers are brought together, the fibers are melted together to form a single strand. By one means or the other, either mechanical splicing or fusion splicing, fiber-optic cables are joined in this way for any number of reasons: to shorten long cable runs, to economize in crowded conduits and to meet fire-code restrictions, to name just a few.

According to Dean Cline, product manager for splice equipment at Siecor Corp. (Hickory, NC), contractors almost always opt to splice in outside-plant applications. The cable-TV industry, in particular, is more prone to fusion splicing because video applications require a low loss budget compared to telephony applications, where the signal-loss budget is more forgiving. However, in an increasingly competitive industry, where the delivery of several types of information over the same cable is the objective, the appeal of fusion splicing, if not the requirement for it, is likely to grow for many fiber applications.

Mechanical and fusion splicing both accomplish the same thing; they bring two optical fibers together and hold them that way so that an optical signal can pass through the join. However, this is where the similarities end--and, for contractors, where weighing tradeoffs begins.

Overall, the advantages of fusion splicing are primarily lower loss and better reflectance performance; it is in these areas that it surpasses mechanical splicing. Ronald J. Roeder, program manager at Kelso-Burnett Co. (Chicago, IL), says that fusion splicing is far superior to a mechanical splice. "It`s quick, easy and you get low loss," he says. Roeder adds that his business requires a fusion splicer for applications that bring fiber from outside a building to inside one, as well as for long cable runs linked in a manhole.

For most contractors, the decision to purchase a fusion splicer is primarily economic, driven by the need to splice frequently. For contractors who seldom splice, mechanical splicing is the less- expensive option, costing $7 to $20 per splice. But, as the frequency of splicing increases, users of mechanical splices shell out more and more money for which they have nothing to show, since a mechanical splice is a device left with the customer while a fusion splicer is a tool that remains in the contractor`s toolkit.

So, with fusion splicers, a one-time capital expenditure is made, and it admittedly can be a large one--from $5000 to $30,000 or more, on average. However, the device pays for itself quickly for those contractors use it regularly.

Karl Clawson, a partner at Clawson Communications (Greenwood, IN), recently paid more than $30,000 for a new fusion splicer because, as a provider of communications systems and installations, his company has to cover all facets of optical-fiber installations. "Up until recently," he said, "we weren`t doing splicing for singlemode optical fiber for long-haul applications." In fact, Clawson did everything but the splicing: installation, termination and cable preparation. "As the market grows, and as one of the most visible providers in this industry, we had to grow too," he adds.

A closer look at fusion splicers

Manufacturers of fusion splicers have been around for almost two decades, with the use of fusion splicers in the United States going back to the early 1980s. However, recent advances in fiber-optic cable manufacturing, as well as the push for more fiber in the network, both public and private, have resulted in new products that provide higher quality and lower loss, are easier to use, and are smaller and lighter in weight.

Since their introduction into the American marketplace, these devices have evolved rapidly, with some vendors into their third generation of products and with new models on the drawing board. Two trends driving these new products, other than increased sales, are the use of ribbon fiber for long-haul applications and the push for fiber into the neighborhood, where cable installers and maintenance workers are restricted to smaller working areas.

Industry observers generally agree that fusion splicing is overshadowing mechanical splicing because of the advantages it offers. While contractors looking for fusion splicers will find a number of products available from about a dozen manufacturers, three of the largest companies producing them are Alcoa Fujikura Ltd. (Spartanburg, SC), Siecor Corp. and Sumitomo Electric Lightwave Corp. (Research Triangle Park, NC). These major manufacturers typically offer three or four product types, from smaller and less-expensive manual models using V-groove technology to more-expensive and fully automated mass fusion splicers.

In addition to cost as a differentiator among products, there are two schools of thought steering product design, and specifically the method of achieving alignment of fiber cores: light injection detection (LID) systems and profile alignment systems (PAS). LID systems maximize alignment by injecting light into the fiber at one end and detecting it at the other end. Siecor is one company that offers LID systems. PAS splicers, on the other hand, like those sold by Alcoa, use video image analysis to determine the position of the core. To accomplish this, they measure the bending of light, when the fiber is backlit, at two perpendicular axes.

Regardless of whose splicer you purchase and the sophistication of the device, there are four basic steps involved in fusion splicing: preparing the fibers, cleaving them, fusing the two fibers together and protecting the splice.

Fiber preparation. Fibers are prepared by stripping away all the protective coatings, such as cladding, jacket and sheath. Once only bare glass remains, the fibers are carefully cleaned--and here, cleanliness is next to godliness.

Cleaving. The next step is cleaving the fiber. Cleaving isn`t cutting, as the word implies; instead, it`s scoring the fiber using a cleaver and pulling or flexing it until it breaks. A proper cleave will result in a good splice, whereas a faulty cleave will ruin an otherwise good splice.

Fusing the fibers. The third step involves fusing the fibers together. Fusion, in turn, consists of two steps: aligning and heating. Alignment can be fixed or three-dimensional, manual or automatic, and is normally accomplished with the aid of a viewer that magnifies or enhances the images of the fiber ends, so that they can be properly positioned. Common magnifying devices are video cameras, viewing scopes and optical power meters. Aligning the fibers means perfectly matching up their two ends, so that light can pass from one fiber to the other with a minimum of loss, reflection or distortion. Once the fibers are aligned, they are fused or burned together by generating a high-voltage electric arc that melts the fiber tips, which are then pushed or fed together.

Protecting the splice. To complete the splice, a number of splice protection methods can be used, among them heat-shrink coverings, mechanical protectors and self-hardening silica.

Product offerings

There are fusion splicers for either singlemode or multimode fiber. There are also mass fusion splicers that are used in high-fiber-count applications. These latter splicers tend to be high-end, high-cost products, where precision and repeatability are critical. Mass fusion splicers are growing in popularity as the demand for high-fiber-count cables, or ribbon cable, increases.

Doug Duke, splicing applications engineer at Alcoa, says that until a few years ago, core-alignment splicers dominated the market. Then, two things happened: optical fiber manufacturers began producing better ribbon fiber, which in turn made it more acceptable to competitors in the telephony marketplace to use ribbon cable, and so mass fusion splicers came to market. "The [telephone companies] in particular wanted to see the cost/performance benefits of the mass fusion splicer," Duke says.

Siecor`s Cline says the demand for mass fusion splicers is the fastest growing of all product categories and will continue to increase over the next few years. "Ten years ago, there wasn`t much application for high-count fiber. Today, 288-count fiber is commonly used by the cable-TV companies, [telephone companies] and other communications service providers," he says.

Siecor offers two mass fusion splicers: the M12, which splices up to 12 fibers at once, and the X75, which splices one to four fibers. These mass fusion splicers aren`t small. The M12 weighs 37 pounds and measures 16 x 12 x 9 inches. "Mass fusion splicers are more complicated products, and enhancements target ease of use," adds Cline.

Sumitomo is on its third-generation mass fusion splicer, the Model 62, introduced this past December. Russ Turner, manager of fusion splicing products at Sumitomo, says the most obvious improvements in this product are software enhancements. For example, there are programmable menus for different types of optical fiber. An arc test automatically sets the splicing conditions in the machine, taking environmental factors such as humidity into consideration so as to optimize the splice. Also, the device has a splice memory that stores all splice results for recordkeeping purposes.

Fixed V-groove splicer

Alcoa also offers a product in this category: a fixed V-groove splicer that can handle up to 12-fiber ribbon. It sells for $35,000 to $45,000.

Fixed V-groove splicers depend upon good-quality fiber for high-quality results. When a fixed V-groove splicer is used to estimate splice loss, it operates by ascertaining that the cladding of the fibers is aligned, not the core. Optical-fiber manufacturers have improved fiber quality in recent years, making more uniform the size and shape of the fiber as well as its position within the cladding. Thus, properly aligning the cladding of two fibers can now result in low-loss splices.

Core-alignment splicers are high-end products designed to optimize the alignment of the fiber before splicing to get the lowest possible loss. Core-alignment splicers remain the preferred product of contractors who must meet stringent contract specifications for splice loss. Cable-TV applications, for example, tend to specify low loss--0.05 decibel or less--which is why core-alignment splicers are popular in the cable-TV industry.

LID systems and PAS products differ in their approaches to core alignment, but a high-quality product of either type will give equally good performance, says Alcoa`s Duke.

Siecor is introducing a second core-alignment splicer in the second quarter of 1996. (The vendor`s M90 model has been available since 1990.) The new model, the X77, is a next-generation device, not a replacement for the M90. It is smaller and more cost-effective to operate, according to Cline. "It`s for users who want the lowest splice loss possible," he says. The device weighs 6.6 pounds and is priced at about $23,000, compared to the older M90 model, which weighs 30 pounds and sells for $33,000. The smaller product is more portable and can be effectively used in constricted work areas.

While neither smaller nor less expensive, the M90 is Siecor`s best-selling product in this area, and Cline expects sales to continue to increase.

Manufacturers continue to introduce new products at the low end of their product lines as well as the high end. For example, full production of Siecor`s Fuselite Termination System will begin in the second quarter of 1996. Introduced last year, Fuselite terminates optical fibers using either fiber-to-fiber splicing or direct fusion splicing of a factory-polished connector. The product costs less than $8000. "For one price you get the added benefit of installing a factory-polished connector," adds Cline.

Moving up a level, Siecor is also introducing a second-generation automatic V-groove splicer. The new product is fully automatic and offers one-step operation once the fiber is prepared for splicing and inserted in the machine. "The product sets the presplicing conditions, such as cleanliness and cleave angle, and estimates splice loss," says Cline.

Priced at $12,000 to $13,000 for a basic model, this device tends to be used by the regional Bell operating companies for broadband applications, while contractors and others use it for emergency-restoration applications. "The advantage of this product is that it takes the onus off the operator for presplice conditions, and it also gives the user more feedback," Cline adds.

Bob Powers, fiber-optic group manager at Frontline Network Systems (Northborough, MA), would love to have a new automatic V-groove splicer for emergency restorations, as well as for some design work. "For the most part, we can`t cost-justify purchasing one at this time, because most of our designs don`t require splicing," he says. The company does have a 10-year-old fusion splicer that is used when such a device is needed.

When thinking about purchasing a fusion splicer, it is important to understand your application--local area networking, cable TV or broadband networks. The application will determine the characteristics required of the splice.

Getting a handle on your budget is of equal importance. Products can range from as low as $5000 or $6000 to as high as $40,000.

Finally, know where you`ll be splicing--in a vault, on a pole or in a bucket truck, for example. And, if possible, know the type of cable you`ll be working with.

Then look for a device that promises accuracy, minimum time to splice and good ergonomics for ease of use and convenience. If you want to go one step further, investigate product support and service options, as well as product training available.

How Fusion Splicers Operate

Manufacturers of fusion splicers can be assumed to offer technically sophisticated and well-made products. While the look and feel of these products differ from vendor to vendor, all devices to some degree offer the same basic functions and operations. For example, they:

- Provide the ability to burn adhering dust particles off the fibers

- Prepare the fiber endfaces for fusing

- Set proper fusing time

- Establish proper fusing current

- Determine the amount of fiber to be pushed together while being melted (known as the autofeed or Z-feed function)

- Supply an alignment mechanism: either fixed V-groove for fixed fiber alignment or 3-axis alignment for three-dimensional adjustment (which improves fiber alignment). This function can be manual or automatic.

- Provide a method of splice-loss measurement

- Utilize a LID system or PAS

- Supply a viewing scope.

Click here to enlarge image

The Fuselite fusion splicer from Siecor Corp. (Hickory, NC) terminates optical fibers using either fiber-to-fiber splicing or direct fusion splicing of a factory-polished connector. It costs less than $8000.

Lynn Haber is a freelance writer in Norwell, MA, who focuses on technology issues.

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