Worldwide cable forum focuses on fiber

Worldwide cable forum focuses on fiber

GEORGE KOTELLY

Of the more than 60 research papers presented last November at the 44th International Wire and Cable Symposium in Philadelphia, there were approximately three times as many studies involving fiber-optic cables, components and materials as there were for copper cables. In addition, all of the 29 poster papers displayed at the end of the symposium dealt exclusively with fiber-optic studies.

Furthermore, the plenary session titled "2020--Visions of Our Communications Future" solidified expectations that optical fiber will dominate the international communications wired infrastructure within 25 years.

The first plenary speaker, Donald Keck, director of optics and photonics research at Corning Inc. in Corning, NY, and one of the three Corning scientists credited with developing the first low-loss optical fiber, predicted a future in which two-thirds of the workforce will be involved in information services. Building on the more than 80 million kilometers of fiber installed worldwide today, Keck expects primary sales growth to be in opto-electronics, with the overall fiber optics market surging from $50 billion in 1995 to $450 billion in 2013.

He also projected that the available telecommunications transport rate will double every two years, starting at 100 megabits per second and skyrocketing to 3 terabits per second by 2020. His other predictions called for worldwide connections to the Internet by 2001 and fiber to the home by the year 2004.

Breakthroughs

Keck foresaw a long list of optical-fiber voice-video-data communications accomplishments to homes, businesses and institutions, with the help of new technology advancements. These breakthroughs involve dispersion-controlled fibers, 1000-fiber ribbon cables, stacked multifiber connectors, hybrid optical chips, vertical cavity surface-emitting lasers and all-optical multiwavelength networking. According to Keck, technology continues to reduce communications costs and spur the optical industry.

Another plenary speaker, John Hood, vice president of engineering at Comlink Inc. in Ontario, Canada, offered visions of future fiber-optic network upgrades and builds in Canadian cable-TV installations. To date, Canada has 95% of homes passed by cable-TV networks, with 7.5 million subscribers. Future broadband networks are expected to incorporate more fiber to the serving area, with secondary hubs serving 500 homes rather than the present 2000 homes, said Hood.

Canadian cable-TV bandwidth is anticipated to be extended from 450 megahert¥to 750 MHz. Channel allocation stipulates the 5- to 40-MH¥band for interactive traffic, the 54- to 450-MH¥band for analog video and the 450- to 750-MH¥band for digital data.

Because of Canada`s sparse population and large rural areas, fiber-optic cables are not expected to be pushed to every home. To reach dispersed homes, hybrid fiber/coaxial cable and wireless networks are planned to serve 40 to 50 residences per square mile.

The role of copper

Presenting the future role of copper twisted-pair cable, plenary speaker Gilles Dupuy d`Angeac, senior executive vice president at Alcatel Cable Group in Clichy Cedex, France, commented that "the change from copper to fiber continues, but fiber is not in a hurry to complete its trip to the home." He added that "field trials in the last decade on twisted-pair [cable] transmission and coding techniques appear to make [copper] a good candidate for information transfer."

Therefore, telephone companies are reconsidering copper for delivering broadband services because they prefer to utilize their huge existing copper plant, he advised. According to d`Angeac, Category 5 and Category 6 copper have slowed the progress of fiber into access networks as distribution and drop cables in local area networks.

Contrary to many industry analysts, d`Angeac predicted a huge growth in copper wire usage over the next 25 years, mainly because of the needs of emerging nations. He claimed that in 1995, more than 2 billion kilometers of twisted-pair copper have been installed worldwide, mostly in the United States, Europe, Russia, China, Japan and South America.

Based on the projected upgrades in communications infrastructure by undeveloped countries, d`Angeac claimed that by 2020, approximately 7 billion km of twisted-pair copper are expected to be installed, predominately in China, South America, Africa and Australia. He said that a new generation of copper wire and improvements in asymmetric digital subscriber line technology will be able to carry increased bandwidth.

However, d`Angeac predicted that worldwide fiber deployment will eventually migrate from the central office to subscribers` homes, depending on each country`s political, social, economic, bandwidth and service needs. In nearly all emerging countries, though, he expected twisted-pair copper to serve as the drop cable to homes and businesses for almost 30 more years.

Fiber papers abound

Of the 64 papers presented at the symposium, 49 focused on fiber-related subjects and only 15 dealt with copper activities. Here are summaries of fiber optics-related papers deemed important to Lightwave`s readers:

Engineers at Siecor Corp. in Hickory, NC, discussed a five-slotted-core fiber-optic armored cable using 250-micron, singlemode, 12-fiber ribbons in a 22-millimeter outer-diameter cable. Each 12-fiber ribbon, the presently accepted fiber-count standard in North American markets, is 3.2ٲ.3 mm.

Super-absorbent polymers are used to water-block the core and ease field splicing. A 360-fiber-optic cable has been deployed with standard installation equipment within a 32-mm (1.25-inch) inner duct. The primary strength member is a flooded stranded steel or solid glass-reinforced plastic central member. Other cable materials include a polyethylene inner jacket, corrugated steel armor and a black polyethylene jacket.

The slotted-core design increases fiber density more than 40% over a stranded loose-tube method. In addition, from a craft-handling viewpoint, ribbon stacks are easier to access and simplify balloon splicing and midspan access. A dry core approach also helps increase productivity for performing cable splicing. Temperature cycling and mechanical stress tests yielded satisfactory cable performance.

Norwegian researchers at Alcatel Kabel Norge AS in Oslo have produced and tested a lightweight fiber-optic ribbon cable consisting of 24 fibers (6 times 4-fiber ribbons), a 6-mm diameter and a 30-kilogram/kilometer weight. They claim that their cable design, slated for use in access networks, is one-half the weight and one-third the diameter of conventional cables with the same ribbon count, resulting in lower transportation and installation costs.

Moreover, because of the reduced weight, the cable design allows a 300% increase in pulling length and a 40% increase in blowing length. In addition, the splicing, jointing and branching processes involve less time and effort.

Papers on the developments of 1000-fiber cables were presented by two Japanese companies--Fujikura Ltd. in Sakura, Chiba, and Furukawa Electric Co. Ltd. in Ichihara, Chiba--and by Siecor Corp.

The Fujikura engineers constructed a single-slotted-rod type of 1000-fiber optical fiber cable. They inserted 10 thin-coated, 8-fiber ribbons that were 2.1-mm wide and 0.3-mm thick into each of 13 slots. The 30-mm-diameter, two-layer, U-grooved stranded cable achieves water-blocking by water-absorbent tape and flame retardation by a non-halogen polyethylene sheath. Temperature, mechanical stress and operating tests showed low transmission losses (0.18 to 0.24 decibel/kilometer) at 1.55 microns.

At Furukawa Electric, investigators concentrated on the relation between the radius of curvature of the ribbons and the slot twisting pitch for a 1000-fiber cable with a mechanical structure nearly identical to the Fujikura design. Transmission-loss tests performed at 1.55 microns for both ends of the lowest layer ribbons and at slot pitches of 500 to 1000 mm showed that acceptable performance (approximately 0.2 dB/km) were obtained at pitches of 500 to 700 mm.

For their 1000-fiber cable design, Siecor researchers developed a thin, dual-layer-coated, 8-fiber ribbon, separable into two 4-fiber ribbons; a single-slotted-rod, U-groove structure with a 375-mm slot pitch and able to hold 10 8-fiber ribbons in each of 13 slots; and a water-blocking tape and a polyethylene jacket that minimize water penetration. Transmission-loss tests performed at 1.55 microns produced acceptable levels of 0.2 dB/km. q

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