Technicians embrace splice-on connector for FTTH, CO applications

By Meghan Fuller Hanna

Overview

The splice-on connector combines the quality of fusion splicing with the ease of a field-installable connector. The resultant product enables today’s technicians to realize greater efficiencies and improved fiber management for FTTH and central office applications, among others.

Fusion splicing—the melting of two optical fibers end-to-end to create one continuous piece of glass—is certainly not new, nor is the concept of a field-installable connector. But put the two technologies together and the resultant splice-on connector affords technicians greater flexibility than they had before. The splice-on connector enables installers to attach a connector to a cable—via fusion—in the field, creating a competitive alternative to standard mechanical splicing. Key applications for the splice-on connector include FTTH networks, including multidwelling unit (MDU)-based networks, outside plant environments, and cable TV networks, as well as data center installation and central office (CO) connector replacement.

The technology itself has been commercially available since the beginning of last year, but its popularity continues to grow. As Josh Seawell, product manager at Sumitomo Electric Lightwave (www.sumi
tomoelectric.com), notes, “When we go out and talk to customers or [go] to trade shows, this is the topic that keeps coming up.”

Most snap-on connectors feature just a handful of components, including a prepolished or factory-polished ferrule typically with a precleaved fiber stub and a snap-on connector assembly. The process—whereby the factory-polished ferrule is spliced on to the field fiber via a fusion splicer—results in a high-quality splice that can be completed by seasoned and novice fiber technicians alike.

“My analogy would be similar to the FC connector for coax,” explains Greg Pickeral, product manager at AFL Telecommunications (www.afltele.com). “It allows you to custom install a connector at the end of a drop cable, and you don’t have to deal with the slack storage of cable; you can just splice on a connector and build your drop cable to length.”

A splice-on connector typically comprises only a handful of components. In the case of AFL Telecommunications’ FuseConnect, shown here, components include the connector plug, housing, protection sleeve, and boot unit.

Splicing strengths

There are several key advantages to the splice-on connector versus other termination methods, including the mechanical and hand-polished methods and preterminated jumpers. Mechanical splicing, for example, requires the use of index matching gel to reduce the reflectance and attenuation caused by the splicing process itself; with fusion splicing, there is no need for matching gels or even curing epoxies.

Moreover, mechanical splicing results in a so-called blind splice. Unless technicians use additional test equipment to measure the integrity or optical performance of the splice, they cannot be certain of its quality. By contrast, most of today’s fusion splicers provide an instantaneous, calibrated loss estimation of the splice so technicians know immediately whether or not the insertion loss is acceptable within their given tolerance.

“The industry really has come to the point where they accept the estimations [from the fusion splicer] as a good reference point or indication of what the actual optical performance is going to be at that splice,” says Seawell.

While many technicians have abandoned the hand-polished technique, it is still practiced by some and requires the technician to hand-polish the endface of the ferrule to the correct angle. It also involves the use of epoxies, which must be cured in a time-consuming process. And, like the mechanical splice method, it results in a blind splice. Additional test equipment is needed to inspect the endface of the ferrule and measure the overall optical performance.

PHOTOS 1 and 2. Today’s fusion splicers typically feature a removable sheath clamp (top), which holds the fiber in place during traditional fusion splicing. Fiber holders (bottom) can be inserted in place of the sheath clamp for splice-on connector applications.

Often, installers will purchase preterminated fiber, essentially pigtails and jumpers that already terminate in a connector. While this method has its advantages, it also requires a great deal of pre-engineering. Say, for example, an installer is using preterminated fiber for an FTTH network, muses Seawell. “The cable runs are going to be different for a house, apartment complex, or business complex, so there’s a lot of pre-engineering that has to come into play to determine, ‘Okay, I’m going to need this length for apartment A and this length for apartment B,’ and so forth. And if you go out there and you miss any of those, you are either going to have runs that are too short or you’re going to have more than you need, and all of a sudden now you have all this excess cable. You can’t just cut that connector off,” he warns. “If you’re doing that, then you’re defeating the whole purpose of the preterminated.”

Splice-on connectors, by contrast, allow technicians to run drop cables to an end user, cut off exactly the length they need, attach the splice-on connector, and plug it in. The splice-on connector enables technicians to manage exactly the cable weight they require without any shorts or excesses.

The same principal applies in CO connector replacement. Steve Harris, director of sales at OFS (www.ofsoptics.com), explains, “Say you pull out a Cisco box and want to put a Nortel box in. You go from, let’s say, a D4 connector to an FC, SC, or LC connector. You have fiber that is already inside that central office or headend,” he says, “and you may not have the room to put new fiber in. What a splice-on connector part does is allow you to just cut off that connector that you don’t want to use and attach the connector you do want to use. You don’t need to rerun cables.”

The use of splice-on connector technology also results in easier fiber management, particularly in MDU-type FTTH applications, says Jason Greene, product line manager for splice and test equipment at Corning Cable Systems (www.corning.com/cablesystems). “As we start bringing more and more fiber closer to the customer unit or, in the case of fiber to the home, even inside the unit, the housings are getting smaller and smaller. Typically, if we were using a fusion splicer, we would splice on a pigtail, requiring a splice tray to hold the protection sleeve. But now with the splice-on connector, we eliminate that pigtail altogether by splicing a precleaved fiber stub protruding out of a factory-polished connector. This eliminates the need for a splice tray and allows for smaller housings in the customer unit.”

Another benefit is that the splice-on connector is designed to work with the removable fiber holders common to many of today’s fusion splicers, enabling technicians to use their existing equipment. All sources interviewed for this story say their customers demanded the snap-on connector technology be compatible with their embedded base of equipment. All that is required is a low-cost accessory kit, which includes the plastic fiber holders that house the fiber throughout the stripping, cleaving, and splicing process.

PHOTO 3. Many existing fusion splicers are compatible with splice-on connectors, including Sumitomo Electric Lightwave’s Lynx CustomFit, shown here, with the addition of fiber holders, which house the fiber through the stripping, cleaving, and splicing process.

These fiber holders, common to fixed V-groove fusion splicers typically used in FTTH applications, offer their own advantages. “What the fiber holders bring is a very rigid process,” explains AFL Telecom’s Pickeral. “You put the fiber in the holder, and it remains in the holder. The biggest enemy to fusion splicing today is actually properly cleaving the fiber and transferring it from the cleaver to the splicer without contaminating the endface of the fiber. The fiber holder is designed with locating pins and so forth, so the fiber is very easily transferred from the cleaving device into the splicer without contaminating the fiber. It is a little more time consuming,” he admits, “but it’s extremely repeatable.”

“It’s kind of an additional benefit now to your standard fusion splicer,” adds Corning Cable Systems’ Greene. “Fusion splicers used to be used strictly for inline splicing. Nowadays, you can use it for inline splicing, but you can also use it to splice on a connector.”

Many options

All of the vendors interviewed for this story have a splice-on connector offering, available under a variety of brand names, including FuseConnect Fusion Splice Field-Terminated Connector (AFL Telecommunications), FuseFlex Termination System (Corning Cable Systems), and Lynx CustomFit Splice-on Connector (Sumitomo Electric Lightwave). OFS simply calls its devices Splice-on-Connectors.

Regardless of the names they use, splice equipment manufacturers agree that the splice-on connector is the biggest trend in fusion splicing today and will likely continue to be as installers discover its benefits versus the use of mechanical splicing or preterminated jumpers.

“It is custom termination,” asserts Seawell. “And it’s also quality termination. You could have said ‘custom termination’ with mechanical [splicing], but now we’re taking out the blind part and adding a little bit more quality because we’re getting rid of index matching gels and things like that.”

Meghan Fuller Hanna is senior editor at Lightwave.