Plastic optical fiber scores in short-distance networks

Plastic optical fiber scores in short-distance networks

With improvements in composition, capability, and cost, plastic optical fiber has been rejuvenated as a viable communications medium that can accommodate 3-Gbit/sec data rates to 100 meters

paul v. salvo

boston optical fiber inc.

For more than 30 years, plastic optical fiber (pof) has proven successful and reliable in wired field applications such as illumination and on/off signal indication. Recent technical innovations, however, have made pof available for advanced applications such as high-speed data communications, desktop computing, local access, telecommunications, small office/home office (soho) networks, and automotive, aerospace, and military networks.

For data-communications applications, pof supports a range of transmission speeds--from slow industrial on/off speeds at 9800 baud to high-speed 622-Mbit/sec desktop computer applications. The present high-end bandwidth availability of pof runs to 3 Gbits/sec, and these data speeds are supported to a distance of 100 meters. Some applications can support longer distances in lieu of bandwidth.

Moreover, bandwidth requirements continue to expand to handle the growing needs of data-driven applications such as video-on-demand, high-speed file exchange, local area network (lan) interconnection, videoconferencing, and computer-based training. These applications are spurring the commercialization of graded-index pof to meet the short-to-medium distance requirements of Fiber Distributed Data Interface and Asynchronous Transfer Mode (atm) applications.

In addition, graded-index pof supports the transmission of bidirectional, full-motion, full-screen video and can be integrated into existing legacy lans. It supports data transfers more than 30 times faster than Category 5 unshielded twisted-pair copper wiring. Furthermore, it costs less than conventional glass fiber, is easier to bend and deploy in lan environments, and adjusts to new optical technologies for home and office uses.

For example, Fast Ethernet hubs running on pof at 100 Mbits/sec were manufactured and installed in various sites across the country last year. In the first quarter of 1997, eight pof hubs were installed and evaluated in major computer companies.

Market goals

The positioning of pof from a market standpoint has been as the technology that fills the price/performance void between glass and copper systems. Presently, pof represents approximately 1% of the data communications wiring market, which is estimated at $2.1 billion in 1996. By claiming just 5% of this market, the total pof sales for 1997 (including all components), could exceed $135 million. Growth trends in this marketplace are expected to continue at an accelerated rate.

Many companies are already providing plastic fiber component accessories such as connectors, transceivers, fiber, interface cards, and hubs. They include Hewlett-Packard, Toshiba, amp, nec, Motorola, Honeywell, Adaptec/Cogent, Packard Hughes, Panduit, Molex, Toshiba, Thomas & Betts, Leviton, Sony, Boeing, and Boston Optical Fiber.

Moreover, these companies are working together to set pof standards for fiber-to-the-desk and fiber-to-the-home applications. They are also working closely with, and have been accepted by, important standards-setting groups such as the atm Forum, iec, eia/tia, nemi, vesa, and ieee-1394 standards committees.

For the past three years, the Defense Advanced Research Projects Agency has funded pof projects such as the High-Speed Plastic Network Consortium. Involved in these programs are Boeing, Honeywell, Lucent Technologies, the University of Alabama, Harris Corp., McDonnell Douglas, Mercury Computer, the University of Southern California, and Boston Optical Fiber.

These projects focus on future generations of pof in the areas of new advanced materials, connection systems, terminations, and electro-optical, infrared, vertically arrayed surface-emitting lasers. Application areas are geared toward home and atm lans, military aircraft, automobiles, multimedia services, and the Internet.

The physical characteristics of pof meet the same challenges as those for copper and glass. With its ability to endure the temperature limits of -40° to +85°C, plastic fiber can operate in nearly all networking environments. It can also withstand a bend radius of 25 mm with no break or damage to the fiber. This robust strength allows plastic fiber to be installed and pulled easily through plenums and walls.

Plastic optical fiber is emerging as the next progressive standard for lan cabling installations by network managers, installers, and integrators. The installation or labor factor of pof is less than either copper or glass. The material cost of pof lies between the cost of high-speed copper cable and glass fiber. Plastic fiber`s versatility and ruggedness are also attracting increased usage as a high-bandwidth, low-cost, fiber-optic replacement for outdated copper cabling (see table).

Copper is not a secure medium. Even though elaborate measures are generally taken to shield computer boxes, copper is still susceptible to electromagnetic interference (emi) and electromagnetic radiation, which impair signal transfer and compromise critical data. In addition, copper lines are vulnerable to electronic eavesdropping.

Plastic versus glass

With its high bandwidth, glass fiber is highly effective for underground and vertical backbone implementations, but it has several disadvantages when used in lan installations. Glass fiber is somewhat fragile for use in horizontal systems. The small core diameter of glass fiber (8 to 100 microns) makes connectorization and critical alignment of fiber a task that requires much skill. The relative size difference between plastic and glass fiber-optic cable is one of plastic`s biggest advantages. Plastic`s larger core diameter--980 microns--over that for glass fiber--62.5 microns--allows it to be more easily connectorized. Typically, plastic fiber can be coupled in less than two minutes and is less susceptible to losses due to dirt and contamination.

The cost of pof can be as much as 40% less than the typical cost of approximately 30 cents per foot for multimode glass fiber. When high cost and product availability considerations are added to the mix for short-haul applications (glass fiber is obtained in set amounts and gives rise to waste), plastic fiber is at parity with glass fiber.

Moreover, glass fiber installation and management require extensive and costly technical expertise and equipment. For example, a routine glass fiber termination could range from 5 to 20 minutes depending on the application. Plastic fiber cable termination can be done in about 1 minute. Based on a network installation of 100 terminations, the saved labor time can be substantial.

Networking applications

To date, there has been no practical solution to the lan bandwidth dilemma. Telecommunications companies have made exceptional progress with glass fiber network backbones, but they have made no significant breakthroughs for "the last 100 meters" to the computer desktop. Instead, the communications industry relies heavily on copper wire cabling solutions for the local loop, but this approach falters at high bandwidths.

Clearly, user pressure to increase bandwidth is intensifying. Many companies, however, still reeling from past enormous investments in migrating to client/server computing environments, are hesitant to spend additional funds for upgrading their network infrastructures. Consequently, they are looking for ways to increase bandwidth without costly overhauls of their existing lan infrastructures.

Because of its flexibility and immunization to factory floor noise interference, pof has been used successfully in industrial control communications and manufacturing applications for several years. Using converters that connect to standard interface protocols such as RS-232, RS-422, and 100-Mbit/sec networking, pof provides secure communication links in tough industrial manufacturing environments. Rugged, robust pof networks can increase productivity by enabling fast transmission of control signals and instructions, and they eliminate the emi that can cripple copper wire links.

Whether communicating to a soho application with a several-hundred-node network or just to a single desktop computer, pof offers interoperability across various platforms (see figure). It also enables bidirectional, high-resolution video and image transfers and the fast data transfers necessary for high-speed Internet access. Stock quotations, large detailed corporate information, interactive multimedia, and medical images are among the bandwidth-intensive applications that can be quickly relayed through pof-based networks.

In the automotive industry, cars are being fitted with computerized sensor systems using plastic fiber as a lightweight, durable networking medium to interconnect computers, navigational equipment, and facsimile machines.

In military applications, pof delivers large amounts of secure information at high speed. Futuristic applications call for equipping combat soldiers with wearable computing, that is, lightweight, water-resistant plastic fiber "smart suits" that can be plugged into computers to download and store, as well as send, receive, and display mission-critical data.

In-flight video entertainment is estimated to reach new levels as plastic fiber is integrated into airplanes. In this approach, airlines will be able to offer passengers their choice of amusement--from movies and video games to catalog shopping and Internet access.

The communications market appears ready for the next generation of lans needed to handle emerging technologies. It is demanding fast, cost-effective methods to transfer data among resource-rich applications and systems. In addition to corporations, soho businesses can use pof to affordably implement secure, high-bandwidth lans for both internal and external communications. q

Capable of handling megabit and gigabit data rates, plastic optical fiber is expected to make inroads into small business, office, and home networks as the preferred interconnection medium. Plastic fiber is well-suited to linking digital-based recording, video, audio, data, and computer equipment, especially over the proposed ieee-1394B 800-Mbit/sec serial-bus standard for digital multimedia devices.