Speeding fiber connections with automatic polishers
Consistency and optimum system performance are key benefits during high bandwidth installations.
Automatic optical-fiber polishers have made inroads into the manufactured termination process, even though many installers working in the field say they still rely on the old-fashioned hand-polishing method to prepare fiber termination ends.
Still, the growing demand for increased bandwidth may be changing this situation, challenging installers to either rely more heavily on pre-polished connectors or automatic polishers to do the job right.
Manual polishing processes usually involve two polishing steps, with the connector being cleaned between steps, then removed and reinserted into the polishing disc. During this process, the fiber is prepared for polishing by dry-sanding or air sanding the fiber stub and then final polishing on a pad. The fiber endface is then polished using coarse grade 15- through 12-µm, aluminum oxide paper, and then on finer grade 5- through 3- or 1-µm, aluminum oxide film.
Installation student Jason Sloan practices using an automatic optical-fiber polisher during a Light Brigade course at the company's Custom Cable Lab.
Automatic polishers, however, can reduce the time for these steps significantly. Some portable machines can polish two or more connectors at a time, and some manufacturers are building them to reduce steps and polishing time even further.
"A polishing machine will help give you more consistency in results and higher quality," says Barry McLaughlin, RCDD and LAN specialist, a contract instructor for The Light Brigade (www.thelightbrigade.com).
Steve Baldo, general manager for Seiko Instruments USA Inc. (www.seikofiber.com), says Seiko makes automatic polishers that can be programmed to handle up to 15 different processes, reducing the time for polishing optical fiber.
"We are closer to one-step type polishing with some ferrules and are simplifying the steps with plastic or epoxy resin types as well," says Baldo. "We are reducing the processing costs, and developing semi-automation for the processing."
The consistency factor
Unlike hand polishing, automatic polishers offer the advantage of repeatability and consistency when it comes to the quality of the polish. Installers say the monotony of hand polishing can lead to poor termination yields and badly polished fiber by the end of a long day.
"Insertion loss is critical," says Charlie Maynard, fiber product line manager for The Siemon Company (www.siemon.com). "A typical reading would be about .3 (decibel loss) for an automated field polisher, vs. about .5 for a hand-polished optical fiber."
Automatic polishers are used at The Siemon Company, for example, where optical fiber is polished in clean room lab settings. One end of this fiber is pre-terminated and polished by the automatic polishers, and the other end is left open for the installer working in the field. "There is more and more of a demand for pre-terminated fiber," agrees Frank Velleca, business development manager for The Siemon Company.
Frederick Forehand, a technician for Milcom Systems Inc., based in Virginia Beach, VA, used automatic polishers while installing optical fiber at a veterans administration hospital in Washington, D.C. "I've used the automatic ones, and they are handy," says Forehand. "I got good testing results out of it."
Automatic polishers, however, remain expensive, and this is partly the reason they have not been overly popular. Some installers say that if they are handling 500 connections a month, it makes less sense to purchase an automatic polisher. But if they are doing more than 1,000 connections per month, it could be cost-effective to purchase one.
Richard Anderson, a master instructor for BICSI (www.bicsi.org), says if automatic polishers could save a contractor or installer money, they would be worth the investment. Anderson, who has been a contractor since the 1980s, has always conducted optical-fiber polishing by hand. He polishes the fiber on the coarse polishing paper, using a 200-power scope to view it and make sure the fiber has not been overpolished, and that it has no defects. He says it only takes a few minutes to polish optical fiber by hand, and he believes the method works as well as an automatic polisher.
"I think the guy doing it manually can do as good a job," argues Anderson.
He is not alone. Installers contacted by Cabling Installation & Maintenance say they continue to handle connectorizing steps either by using the manual method, or by using pre-polished connectors to get the job done.
In general, automatic polishers are being used by manufacturers or connector assembly houses that make patch cables. In a situation where many cables are being polished at once, automatic polishers offer a definite advantage in terms of volume and cost.
But while they may be popular with optical-fiber manufacturers, automatic polishers are still less popular with the installer who is working in an in-plant cabling project.
"You are not seeing them out in the field that much, unless you (the installer) have mass terminations in one spot," says Ron Shaver, a master instructor for BICSI. Installers say one of the obvious drawbacks to an automatic polisher is that they cannot easily go everywhere that the installer goes. Most models are not designed for portability. But this is changing as manufacturers improve on smaller, battery-operated, light-weight portable models. Krell Technologies Inc. (www.krell tech.com), for example, makes the SpecPro 3K—a portable field polisher that can handle up to four connectors at once.
"This is a portable polisher with the capability of singlemode performance in the field," says Al Cheswick, vice president of sales and marketing. "There seems to be a lot of higher speed networks on campus environments, and they have more demanding specifications on optical performance for networks," Cheswick continues. "Many end users require field connectorization of cable, as opposed to pre-terminated fiber. It requires polishing in the field."
Some installers remain skeptical that automatic polishers can do the job quickly, or at least, quickly enough to justify their purchase. Forehand argues that the amount of time it takes to use an automatic polisher does not make the investment worthwhile.
"With a (Siecor) UniCam, it takes two and a half minutes," says Forehand. "For a hot-melt polish, it can take 5 to 10 minutes. An automatic polisher will do it in seven minutes. That doesn't make it enticing to get one."
Shaver says part of the reason for this attitude is that many installers simply prefer to polish optical fiber by hand. And institutions that teach cable installation also continue to teach the manual method. Anderson explains that BICSI teaches manual polishing methods in its classrooms, partly due to its philosophy of teaching the fundamentals, and partly because most installers will go the manual route when they are working in the field.
Handing it over
Even so, those who teach installation methods say the ever increasing need for more bandwidth is raising the possibility that a piece of hand-polished optical fiber will not be sufficient, and terminations will have to be polished by machines or in factory settings.
"Up until now, a lot of people interpret them (automatic polishers) as a lazy man's tool," says McLaughlin. "They say, 'I could do the same job by hand. Why get a machine to do it?'"
But McLaughlin raises the issue of higher performance both in insertion loss and in optical return loss. The growing demand for higher speed transmission systems, such as Gigabit Ethernet and now 10-Gigabit Ethernet, will cause system designers to enforce more stringent testing to satisfy these new demands. "Singlemode terminations have always had both insertion loss and return loss issues, and these types of issues could transition to the multimode world," says McLaughlin.
Multimode fiber systems have traditionally been used for low-speed applications and were terminated or polished by hand. Singlemode systems are traditionally higher speed, and the telco and CATV markets use laser-based light sources that are highly sensitive to reflections. On a poorly polished singlemode connector, there could be incorrectly polished endfaces that could lead to increased Fresnel reflection, which is caused by the difference in the index of refraction between two media. These Fresnel reflections cause jitter in conventional laser light sources and result in increased system bit error rates that could lead to system failure or reduced performance—due to a fault in the optical fiber or a bad polish.
"It's difficult to do consistently high performance singlemode termination in the field by hand, if next to impossible," says McLaughlin. "That is where you need the benefits of machine polishing techniques."
The pre-polished look
But even as bandwidth changes place more of an onus on finely polished optical fiber, both installers and cable installation instructors say the advent of pre-polished connectors represents the real competition for automatic polishers.
The connectors have been on the market for about 10 years. They have pre-polished fiber stubs within the ferrule that mate to a mechanical splice on the field termination side, and provide consistent performance when it comes to multimode return loss.
For comparison, installers say a hand-polished optical fiber will provide about a .5 decibel loss. But a pre-polished connector can provide about a .2 or .3 decibel loss. "Pre-polished is more what I see," says Mike Ping, project manager for SPS Technologies, based in Jenkintown, PA.
Krell Technologies Inc. makes the SpecPro 3K, a portable field polisher that can handle up to four connectors at once.
Doug Coleman, manager of technology and standards strategy for private networks for Corning Cable Systems (www.corning.com), says Corning is betting on the fact that most installers will be turning to pre-polished connectors. "Everybody is looking at costs, and at the return on the dollar," says Coleman.
Whether choosing an automatic polisher or pre-polished connectors for today's higher performance installations, the trend remains the same: "Hand polishing was OK in the old days. But today, you have to do it right," says Hugo Draye, market segment manager for Fluke Networks (www.flukenetworks.com).
Brian Milligan is senior associate editor for Cabling Installation & Maintenance.