Euro-connectors ease field use
As the number of fiber-optic network trials rapidly increases across Europe, manufacturers on the continent have produced connector parts to support fiber-to-the-curb and fiber-to-the-home networks as viable architectures.
European Commission and partner companies, as well as some independent vendors, claim to have overcome the technological barriers to producing low-cost and highly reliable connectors.
Two European leaders in the connector field are Radiall in Rosny-sous-Bois, France, and Stratford, CT; and Diamond SA in Losone, Switzerland and Littleton, MA. The coupling mechanisms used by these companies differ in concept but not in objective--easy to use by field personnel and able to survive thousands of matings and dematings.
The cone-sphere approach
Radiall is a partner in European Commission research on advanced communications projects, or Race. The company`s first project has produced an internationally supported EC connector for fiber-to-the-home network applications. According to Radiall spokesman James Buffinton, "The EC connector offers a European solution that challenges Japanese ceramic technology for fiber-optic connectors." This connector accommodates many applications, including coupling active devices, attenuators, multichannel modules and backpanel terminals.
The push-pull latching connector is based on a cone-sphere mating concept, which achieves a typical insertion loss of 0.25 decibel at 1300 and 1500 manometers for singlemode fiber, and 0.15 dB at 850 nm for multimode fiber. Reflection losses exceed 60 and 50 dB for singlemode and multimode fiber, respectively. A variety of connector plugs, mating adapters and optical ferrules are available to match user requirements.
In the cone/sphere mating method, only two elements--cone and sphere--require strict manufacturing tolerances. Therefore, the cost becomes less expensive than traditional fiber coupling units. "And," contends Buffinton, "the connector is transparent in terms of bandwidth."
Although this EC connector was developed for fiber-to-fiber connections, the company is applying the concept to fiber-to-device assemblies and active backpanel configurations. Radiall holds an EC patent, but is willing to grant licenses to other manufacturing companies.
The EC connector is being evaluated by European telecommunications operators. Belgacom, Belgium`s national telephone company, has selected the EC connector for its fiber installations. In addition, France Telecom has qualified the device for its fiber-optic trunk networks.
An advanced fiber-to-device version has been developed for use in fiber networks being deployed in Germany`s Opal optical access line project. Additional uses include cable-TV and high-definition television networks in The Netherlands, France, Great Britain and the United States. Other European research programs are using the EC connector in pilot and demonstration projects.
Last year, the Swiss company Diamond put its E-2000 fiber-optic connector on the market for fiber-in-the-loop, fiber-to-the-node and fiber-to-the-desk applications.
According to Diamond Product Manager Marco Luisoni, making this connector user-friendly was a primary concern. As fiber cabling moves closer to the home, users and technicians who are not installation specialists are expected to handle high-performance optical devices and connectors. Therefore, the company devised an interchangeable color-coding and mechanical keying scheme to prevent cable-connection mismatches.
"Customers appreciate the different codings," says Luisoni. They can readily identify transmission lines carrying different services, such as cable TV, and the designated customers.
The connector`s two-piece, injection-molded-polymer housings rely on guiding tracks that direct the ferrule into the alignment sleeve. This prealignment strategy yields a 0.15-dB typical insertion loss. Integrated protective caps and spring-loaded shutters automatically engage to shield the ferrule against dust and scratches, as well as to shield personnel from laser radiation.
To eliminate the need to grasp the connector body when demating, a positive-latching mechanism with an interchangeable, color-coded and mechanically keyed thumb-latch promotes quick press and pull demating, prevents improper matings, and presents visual cable identification. In addition, the connector`s small footprint and press-pull operation allow high-packing densities.
Comments Bart Graf, general manager at Diamond USA Inc. in Littleton, MA, "After 2000 mate/demate cycles, which are done manually to simulate real-world usage and without intermediate cleaning of the ferrule endfaces, the variation in insertion loss was less than 0.05 dB." The connector has a U.S. patent, and 50,000 pieces have been shipped worldwide, he adds.
The connector is being used for cable-TV and telephony services by Energis, a power company in the United Kingdom, and by Casema, a Dutch cable-TV operator, as well as others. It has also been qualified for use in Finland and Poland, and is being employed for various network applications in Switzerland, Germany and Italy.
Keep costs down
In European lightwave networks, user demand for increased interactivity and bandwidth are pulling fiber closer to the home, but only when the installation can be done via cost-effective connections. The network cost problem involves the alignment of mating parts to the tolerances needed for efficient lightwave signal throughput. Connector alignment must be accomplished automatically by the mating parts rather than by installer skills.
In addition to connector-to-connector matings, connector-to-device coupling is equally important because fiber-optic cables are expected to be used in the return path for interactive services. Traditional pigtail fiber-to-device connections are unacceptable because of maintenance inflexibility.
The proliferation of fiber translates into more maintenance, testing, installation and replacement of connectors, devices and cables. It requires repeated plugging and unplugging of fiber-to-active-device and fiber-to-fiber connections. A critical connector requirement--repeatability--means the two joining connectors remain aligned despite numerous plugging and unplugging engagements. q
Adele Hars writes from Paris.