Proponents of plastic optical fiber (POF) have long touted the technology as a viable alternative to copper and glass fiber in enterprise networks-with little success. Now that broadband services have put new demands on networks within the home, the POF community sees another chance to grab the attention of communications network architects. Recent advances in the technology have improved the ability of POF to carry high-speed traffic over the distances that home networks would require. Yet representatives from companies working on POF admit that several obstacles remain before them in their attempts to break into home applications-particularly in the United States.
As its name implies, POF uses polymers instead of silica to create a fiber capable of carrying communications signals. Step-index fiber made from polymethylmethacrylate (PMMA) has received the most attention in communications circles; it’s the fiber car makers have begun to use to support infotainment and other systems in their vehicles.
POF offers several of the advantages over copper that glass fibers do: greater bandwidth capacity, resistance to EMI, better security, etc. However, it’s also easier to install than glass fiber, its proponents maintain. Step-index PMMA fibers have a larger core area than typical glass counterparts, which eases coupling. POF is less sensitive to bending, and connectors can be attached without epoxy or other adhesives. Step-index PMMA fiber also is frequently used with LEDs operating at 650 nm, which is in the visible spectrum and therefore makes POF even easier and safer for installers to use. LED-based transceivers also are cheaper than their Fabry-Perot or DFB-based counterparts.
Despite these apparent advantages, the POF community has had little luck establishing a beach head in communications networks, outside of niche industrial applications and the aforementioned automotive successes. The major hindrance has been bandwidth capacity over distance; step-index PMMA POF can carry more data than copper, but falls short of the performance glass fibers provide. Particularly in the United States, the technology therefore has had difficulty being taken seriously among cabling standards groups.For example, the Telecommunications Industry Association’s Fiber Optic LAN Section (TIA FOLS) “does not include plastic optical fiber (POF) as part of its initiative to educate users about the benefits of fiber in structured cabling,” according to a written statement the organization supplied for this article. Using FOLS member Steve Swanson, manager, standards engineering at Corning Inc. (www.corning.com), as a source, the statement continues, “[I]n the past, POF was not an alternative to glass optical fiber in structured cabling because manufacturers were not able to meet the minimum distance requirement established by TIA 568.B of 100 meters. This was due, in part, to the fact that plastic optical fibers were made with a very large core diameter and were designed to be used with 650-nm LED optics. This large core diameter enabled plastic optical fibers to be easily connected and enabled the use of low-cost electronics, but the tradeoff was low bandwidth, making it only useful for very short distances and low-data-rate applications.”
Recognizing these limitations, the POF community has advanced the technology via graded-index POF and new polymers that promise support for gigabit speeds (see “It’s Like Glass, But It’s Plastic, page 35), as well as new transceivers for 100-Mbit/sec use (see “Plastic Optical Fiber Transceivers Target Fast Ethernet Applications” Lightwave, June 2006, page 22). In particular, the advent of the new transceivers has POF proponents thinking big-particularly when it comes to applications where the technology’s strengths might play more strongly than its perceived limitations.
One such application is IPTV-driven home networking, and the time to strike is now, say POF boosters. “First off, all the pieces are here. We have the fiber with the larger bandwidth; we can go to gigabits in the home now. And we’ve got the components-we’ve got the transceivers,” enumerates Paul Polishuk, president of the market research and analysis firm Information Gatekeepers Inc. (www.igigroup.com) and a member of the POF Trade Organization’s (www.pofto.org) board of directors. “So we think we have all the pieces that make sense. And…there isn’t one standard yet that’s been adopted by anybody yet for the home-so it seems to be up for grabs.”
The most obvious hurdle to the use of POF that few if any homes already have it in place. In the cable-ready United States, alternatives to POF frequently are either already present (in the case of coax) or are easily installed (such as wireless hubs or, perhaps, powerline options).
However, not all markets have homes already configured for broadband to the set-top box. Europe in particular represents a tempting target for POF, and much of the home networking thrust is being directed toward that part of the globe. European home construction offers one attractive factor. While the wiring in most U.S. homes runs behind drywall, European homes often use a readily accessible conduit on the outside of brick or cement walls. Josef Faller, cofounder and managing director of Homefibre Digital Network GmbH (www.homefibre.at), estimates that 80% of European homes have such conduits, which would make retrofit on the Continent significantly easier than it would be in the United States. The use of brick and concrete for walls tends to dampen the effectiveness of wireless options, Faller adds, which opens the door further for POF.
Additionally, European building codes are not a problem for POF, Faller says. While the technology has made little headway in U.S. standards bodies, it is making progress in organizations with stature in Europe, such as the International Electrotechnical Commission and the International Standards Organization (see “POF in International Cabling Standards,” Lightwave, June 2006, page 20).
The other hurdle to implementation is easy interface to home networking equipment, such as routers and set-top boxes. To date, few if any such devices carry POF-compatible interfaces; the MiAVo VDSL2 Wi-Fi Gateway from Netopia Inc. (www.netopia.com) is the only POF-ready home networking device that sources contacted for this story could name.
Thus, some sort of adapter or media converter would be required. Homefibre has adopted the latter route. The company has developed a copper-to-POF media converter that can be installed in an electrical outlet. The media converter can be supplied with a variety of interfaces to support multiple protocols, including Fast Ethernet and IEEE 1394. The POF itself rides alongside the home’s electrical wiring to provide an optical backbone for home networks. The systems should support Fast Ethernet links of 100 m, Faller says, while certain types of 1394 links could accommodate 200 Mbits/sec over 50 m.
Faller estimates that media converters in their currently small quantities cost approximately $100 apiece, with the target price for volume production significantly lower. Faller says his company’s technology is currently the subject of a pilot project somewhere in Europe, although he declined to provide details.
The arrival of 650-nm LEDs with sufficient power to drive 100 Mbits/sec through the home provides a catalyst for companies such as Homefibre. Faller says he uses devices from Toshiba (www.toshiba.com), but acknowledges that additional LED sources, including Firecomms (www.firecomms.com) and Infineon (www.infineon.com), are available. The latter recently announced a 650-nm LED-based Ethernet transceiver for home networking based on technology Infineon has already supplied to the automotive industry.
Infineon’s Imran Hajimusa, director of marketing for communication access ICs, and Jim Tan, product marketing director, voice access products, believe that other providers of home networking gear will follow Netopia’s lead and incorporate POF optoelectronics into their products. “We were very cautious in the beginning because we did not know [how POF would be received]. I mean, it was just throwing another technology into the mix of other technologies that were already available,” says Hajimusa of the decision to attack the home networking market. “But it’s been surprisingly positive. We’re seeing a lot of pickup. Some of the telcos have made very concrete plans to use POF technology to deploy IPTV.”
The Infineon sources expect to see POF take off in the United States as well as Europe; now that it can support Ethernet, standards concerns should be muted. “POF to us is a PHY technology, no different than, say, 100Base-FX PHY technology,” explains Tan. “You can run different protocols on top of it-1394 is one of them. In our case, we actually run Ethernet over POF. So it’s already defined as part of that Ethernet standard.”
“We also thought, to be very honest, at the beginning phase of this whole thing, ‘Oh, gee, we have to change the standards,’” Hajimusa added. “And then we talked to the telcos and the service providers and came to the conclusion that we don’t need to change anything. This is already covered and it’s all Ethernet.”
If service providers buy into the technology, Hajimusa and Tan envision that POF’s ease of installation will make do-it-yourself home networking a reality. The fiber can be cut to the desired length by a pair of scissors, while connectors similar to those used on home stereo equipment-which reside in the equipment itself, meaning all users have to do is open a clamp and push the fiber between the clamp’s jaws-will make connectorization a snap.
However, not everyone with POF experience is ready to jump on the bandwagon. Bruce Robertson, technical director of test equipment manufacturer Kingfisher International (www.kingfisher.com.au), says that the technology must overcome a legacy of difficulties that have dogged it in the past. This effort starts with the fiber itself. “There’s been endless examples over the years of R&D guys coming with a reel of fiber and then spending the next half of their lives trying to replicate it,” he observes. Kingfisher itself, which makes POF-friendly power meters, has had trouble getting fiber, Robertson says. As in the glass space, POF manufacture is governed-some would say hamstrung-by patents and occasionally a lack of licensing, which makes it difficult for carriers and installers to develop multiple supply sources, Robertson points out.
The technology also faces the competition from the other home networking alternatives mentioned previously. Robertson likes the wireless approaches, either Wi-Fi or ZigBee in particular. “I think POF is probably a solution looking for a problem, in this case,” he concludes.
While admitting that fiber supply has been a problem in the past, Polishuk asserts that the number of suppliers producing POF and the number of distributors carrying the product have both grown. Japanese companies have made the most noise in the POF space, with Asahi Glass, Asahi Chemical, Mitsubishi Rayon, Toray, and Fuji Film offering various POF variants. Suppliers outside Japan include Chromis Fiber in the United States, Optimedia in Korea, Nexans in France, and Luceat in Italy, among others.
As for competition from other technologies, most in the POF community remain undaunted. “I think the ramp-up is happening this year, very quickly,” asserts Hajimusa. “Because VDSL is getting deployed right now, and people don’t have one key technology that they can rely upon for home distribution. And as we look at our customer base and the telcos with such a high interest, some of the telcos actually getting into the deployment as we speak, I think that you will see by the end of the year people coming out with actual deployments and users.” As mentioned in the accompanying article, POF has labored under a reputation for not being able to handle enterprise requirements. In addition to beefing up transceivers, the POF community has worked on improving the fiber itself. Of particular interest is the new generation of graded-index amorphous perfluorinated (PF) polymer fibers that operate much more like glass fibers. Chromis Fiberoptics LLC (www.chromisfiber.com) in the United States is one company working on this technology. According to Whitney White, the company cofounder and chief executive officer, the PF fiber features apertures similar to multimode glass fiber and can accommodate the same 850-nm VCSEL-based transceivers.
The PF fiber offers the foundation for the POF@10G Group, an industry consortium that is marshaling its forces for another attack on the enterprise and data center market. The group, which includes Archcom Technologies (www.archcomtech.com), Asahi Glass Co. Ltd. (www.agc.co.jp), Chromis, Nexans (www.nexans.com), Phyworks Ltd. (www.phyworks-ic.com), and Picolight Corp. (www.picolight.com), combined PF fiber with VCSEL-based transceivers and electronic dispersion compensation to demonstrate 10-Gbit/sec transmission over 100 m of POF during this year’s OFC/NFOEC.
Unlike the companies highlighted in the article, Chromis isn’t looking very hard at home networking. Instead, White sees more opportunity in the emerging data center market. “In data centers and in some niche applications, I really feel like there is an unmet need,” he offers. “In those kinds of applications it really comes down to a question of how do we compete against glass. So our sort of competitive offering is a little higher-priced cable, but something that is much easier to put connectors on, doesn’t need a lot of the cable management, and will take all kinds of abuse.”
However, U.S. data center and enterprise applications are standards driven, and POF hasn’t had much success in gaining acceptance in the structured cabling standards. “Certainly there will need to be one fairly soon in order for us to have a plausible offering in that area,” says White of the development of a POF-friendly standard. “We’re doing a lot of the background work right now to show exactly what ranges of distances, for example, and what sort of hardware packages will give you those distances.”
White and other POF proponents will have their work cut out for them when it comes to getting the TIA FOLS on their side. “From a standards perspective, we still don’t see much activity around POF in the U.S.; there is no current activity with TIA, although POF will likely be included in the new industrial standard,” the FOLS stated in the written response to Lightwave queries mentioned in the accompanying article. “In Europe, there is more activity, primarily in IEC 86A and IEC 60793-2-10 where POF is included in the discussion of multimode fibers.
“In conclusion, we don’t see POF taking market share from glass optical fiber for structured cabling systems in the near future,” the FOLS states.