Step-Index, Graded-Index become focus for plastic optical-fiber applications

In 1966, the first Plastic Optical-Fiber (POF) product with a polymethyl methacrylate or acrylic core was introduced by Dupont under the brand name Crofon.

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In 1966, the first Plastic Optical-Fiber (POF) product with a polymethyl methacrylate or acrylic core was introduced by Dupont under the brand name Crofon. At the time, while market development was significant, tremendous advances in POF technology had led to an even wider range of applications.

Today, POF cabling can support high-bandwidth communications in the automotive, home networking and telecommunications markets. These applications continue to emerge, as well-known manufacturers, such as Mitsubishi Rayon, Lucent Technologies, Samyang, Fuji and others, as well as a host of new entrants, including Digital Optronics, further develop the technology.

The market for POF in communications systems is now primarily focused on two products: a lower-speed Step-Index Plastic Optical Fiber (SI POF) and a newly emerging Graded-Index Plastic Optical Fiber (GRIN POF) that is 100 times as fast as SI POF.

While applications for SI POF in the automotive and home networking environments are interesting, it is the new advances in higher bandwidth GRIN POF that offer the most promise—particularly in reducing the overall cost of optical networking in today's telecommunications industry.

While copper is a proven, low-cost material for lower-speed networks, some constructions of copper cable are bulky. On the other hand, Glass Optical Fiber (GOF) meets the requirements of higher-speed networking, but is extremely expensive to install and maintain.

Glass fiber is highly effective for underground and vertical backbone implementations, but it is too fragile for horizontal subsystems that are found in automobiles, network operation centers, wiring closets and other confined spaces that cannot accommodate the mess of bulky wiring made of copper. These shortcomings in both glass and copper are introducing a myriad of new opportunities for lower-cost, higher-speed plastic fiber.

SI POF's place at home

Home networks are proving to be a tremendous opportunity for the POF market. With a general shift in the market toward new digital devices and strong demand for high-speed Internet access, there is significant growth in home networking systems that can interconnect computers, printers, MP3s, and digital cameras. In addition, the ratification of the IEEE 1394b standard for FireWire interconnect cables is speeding the growth in the market.

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Graded-Index plastic optical fiber matches the speed of today's multimode glass optical fiber at distances of up to 30 meters.
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Eventually, lower-cost, high-speed cabling will be pre-installed in most homes, making it easier for users to network virtually any electronic device in their home. Parks Associates (Dallas, TX; www.parksassociates.com) estimates that during 2004, a total of 540,000 (or 42%) of 1.29 million newly constructed U.S. homes will be outfitted with structured wiring. As a component of structured wiring, POF is expected to grab a considerable share of the market due to its superior bandwidth capabilities, low cost and ease of installation.

In the past decade, POF has made tremendous strides in the telecommunications market. A major step toward using low-cost POF interconnects while preserving the highest network reliability standards was taken in 1998 when a Lucent Technologies (www.lucent.com) team introduced the first commercial telecom intra-system interconnection system using POF. This was the first large-scale, commercially produced, all-optical backplane, and is the centerpiece of the successful Lucent WaveStar DACS 4:4:1. This success was followed by a number of products based on SI POF that provided customers with reliable, lower cost networking.

The future of GRIN POF

Today, dramatic changes in the nation's telecommunications environment have forced carriers to look for alternatives in their network infrastructure. While POF has already begun to play a role in the telecommunications sector, recent innovations are taking the impact and use of POF to a new level, offering carriers the same high-speed 10 Gbits/sec capabilities as glass fiber while significantly reducing the cost of the component infrastructure.

Four major factors will continue to drive POF interconnect solutions in the telecommunications market:

  • Bottlenecks still remain at network switching facilities where bandwidth is still in high demand;
  • The transition from circuit-switched voice traffic to high-speed packet-switched data;
  • Quadrupling of channel speeds every two years—presently
  • at 10 Gbits/sec;
  • A shift in the carriers' profitability model from growth to lower costs.

Optical interconnect systems required to link network hardware consist of optical-fiber cable, terminal connectors, and transceivers. Cable assemblies that now use multimode GOF are expensive in optical interconnects due to diameter-related alignment difficulties and fragility. Specifically, GOF's strict alignment tolerances require expensive, high-precision components in connectors and transceivers.

Using GRIN POF, carriers benefit from more forgiving tolerances, lower cost, and simpler field installation. The 180-µm diameter of POF—three times the diameter of multimode GOF—allows the use of less expensive designs for transceivers and connectors. As a result, new GRIN POF technology will enable overall reductions in the cost of interconnection equipment in data/telecom networks by as much as 75%.

The telecommunications market could truly serve as the springboard to widespread POF adoption. According to a May 2002 report by ElectroniCast (www.electronicast.com), "Multifiber Transmit Link and Components Forecast," the market for interconnects is expected to reach $1.6 billion by 2006. Furthermore, the same report indicates that 70% of the interconnect market is for lengths up to 30 meters, representing a significant opportunity for low-cost, high-bandwidth GRIN POF solutions to compete head-to-head with more expensive GOF interconnect solutions.

With the new demands placed on today's telecommunications carriers, POF has perhaps found the "sweet spot" in the telecommunications market.

Dr. James Walker, an expert in plastic optical fiber, is the chief technology officer of Digital Optronics Corp. (www.digitaloptronics.com). Gary Myers is vice president of marketing for Digital Optronics Corp. He can be reached at gary@digitaloptronics.com

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