Holey fibers, bragg taps, and the future of the Internet at upcoming optics meeting

Washington, DC, February 28, 2001 ----- A giant conference devoted to fiber optics will take place on March 17-22, 2001 at the Anaheim Convention Center in Anaheim, California. Known as OFC 2001--short for the 2001 Optical Fiber Communication Conference and Exhibit--this meeting details a lot of the technical breakthroughs occurring in fiber optics. More than 25,000 attendees are expected. The meeting is sponsored by numerous societies, including the Optical Society of America (OSA) and IEEE.

INTRODUCTION
Nothing travels faster than light. Not only it is the fastest form of energy in the universe, but light can also carry a tremendous amount of information. Telecommunications companies have been capitalizing on these facts for several decades, and the world is being transformed by fiber optics--in which light travels through tiny, glass-based wires to transmit information. As our information revolution calls for even greater access to data, and faster speeds of transmission, significant advances in fiber optics are still ahead. This is the age of fiber optic science.

Spurred by necessity, the fiber optics industry is inspiring many scientific breakthroughs. OFC is a place where many of the breakthroughs first get announced. OFC was the place where researchers presented the early details of a now-widespread form of fiber optics communications, known as WDM--wavelength division multiplexing, in which a light signal is split up into several data streams, each in different parts of the optical spectrum. In addition to the technical sessions, many optics companies announce significant new technologies and products at OFC. The tradition is expected to continue at this meeting.

MEETING PRESSROOM
A pressroom will be located at the conference from Sunday afternoon, March 18 through Wednesday afternoon, March 21. It will be available for members of the press and for public relations officers.

LOOKING INTO THE FUTURE: OPPORTUNITIES AND TECHNOLOGY
The keynote speakers at this year's OFC Plenary Session on Monday morning will focus on the future of fiber optics and the Internet: Where is the technology taking us, and where will the new opportunities be in the years ahead? The first speaker, Vab Goel of Norwest Venture Partners, will talk about the changing networking industry and opportunities emerging in the field. Goel has been called one of the "top 25 unsung heroes on the Net" by Interactive magazine, and speaks nationally and internationally on the future of the Internet. Also speaking is Robert Lucky, corporate vice president of Telcordia Technologies. Lucky will address the impact of changing technologies on networks, companies and economies. In addition to inventing the adaptive equalizer (a technique for correcting distortion in telephone signals--used in all high-speed data transmission today), Lucky writes a bimonthly article for Spectrum magazine on his observations about the engineering profession. (Monday, March 19th, 2001, 8:30 - 11:00 AM, Anaheim Convention Center Arena)

HIGHLIGHTS OF THE TECHNICAL SESSIONS
Here is a sample of the many talks at the meeting:

PUTTING THE PEDAL TO THE METAL ON THE INFORMATION SUPERHIGHWAY
The Defense Advanced Research Projects Administration (DARPA) developed the basic Internet infrastructure that fundamentally changed the way the world works, plays, and shops. But the growing importance of electronic communication often leads to virtual traffic jams on the information highway. DARPA is again taking the initiative in cyberspace as it helps to assemble and test the Supernet, the next generation Internet, with components capable of data transmission at gigabits per second--thousands of times faster than the current Internet data rates. DARPA Project Manager Mari Maeda (703-696-2255, mmaeda@darpa.mil ) will present an overview of the research and technology vital for building the Supernet in session TuK1 (March 20, 1:30) and describe a few of the potential applications that will benefit from high speed communications. (More information on the Supernet at http://www.ngi-supernet.org/ )

AN IMPROVED DIGITAL POLYMER SWITCH
Most fiber-optics components are based on inorganic materials, such as glass. But some researchers are developing fully organic, polymer versions of optical components. Polymers are cheap, easy to make, and easy to integrate with other components. Ulrich Siebel of the University of Berlin (011-49-30-314-22934, siebel@sun6hft.ee.tu-berlin.de) and his colleagues have designed a polymer digital switch for relaying signals to different parts of a telecommunications network. The switch incorporates an attenuator, a device that reduces the power of the incoming signal to desired levels. As a result, the new switch has significantly lower amounts of undesirable "crosstalk," which is essentially noise introduced to one of the communications lines connected to a switch from another line also connected to the switch. (Talk WR4, March 21, 2:45 p.m.)

HOLEY OPTICAL FIBERS AND WHITE LIGHT LASERS
One might think that there's not much new under the sun in the basic design of optical fibers, the solid glass threads that guide light for such applications as telecommunications, laser surgery, and laser machining. But a new optical fiber design, known as the holey fiber, is expanding possible applications not only for optical fibers, but for light itself. With the holey fiber, one can transmit significantly greater powers of light without destroying the fiber, and send optical signals through with less distortion than ever before. This can potentially enable more powerful laser surgery inside the body, more effective laser machining, and a host of increased applications for optical telecommunications. Traditional optical fibers absorb a good amount of light in their glass core. A holey optical fiber, as the name suggests, is made of hollow glass tubes bundled together like a fistful of straws. They're arranged in a specific geometrical pattern of glass tubes separated by air. Then they're melted together and collapsed to a microscopic diameter. Sending light waves through the tube causes light to scatter from the various glass-air boundaries in such a way that the waves at each scattered point combine or interfere to make light go straight down the central hole in the tube, rather than spill into the fiber's glass portions where some of it would get absorbed. In this way, the holey fiber acts like a two-dimensional "photonic crystal," a specially tailored geometrical structure for manipulating light waves. Philip Russell of the University of Bath (p.s.j.russell@bath.ac.uk, 011-44-1225-826946), who announced the first working holey optical fiber at an OFC postdeadline session several years ago, will present a tutorial on this topic. He will describe how the fibers have enabled his lab and Lucent Technologies to develop a powerful "white light laser"--a light source with the brightness of a laser, but with a range of colors, or "bandwidth," of white light. Such a laser has potential applications as a tiny measuring device on future space probes, and for medical imaging using safe non-ionizing light. (Tutorial TuL1, March 20, 1:30-3:30 p.m.) Anders Bjarklev of the Technical University of Denmark (ab@com.dtu.dk) will review recent advances in research and development of these fibers. (Talk TUC1, Tuesday, 8:30 a.m.)

HOLEY OPTICAL FIBERS AS NONLINEAR DEVICES
Periklis Petropoulos of the University of Southampton (pp@orc.soton.ac.uk, 011-44-23-8059- 3141) will present a holey optical fiber that is up to 30 times more nonlinear than conventional silica fiber types. (Talk TuC3, March 20, 9:15 a.m.) Nonlinear, in this case, means that a high-intensity optical beam of a certain wavelength can generate light at new wavelengths by virtue of its interaction with the fiber. Fiber nonlinearity can be used to enable a number of all-optical functions in telecommunications such as all-optical switching and routing, and regeneration of degraded optical signals (the application presented in this talk). Such all-optical devices can be more than a thousand times faster than their electronic counterparts. The fibers are also very good at preserving the polarization (electric-field direction) of the transmitted light, a property that can be important for such devices. In addition, the researchers are investigating their approach in other glass types besides silica, such as chalcogenide (GLS) glass, offering the promise of another 100-fold increase in nonlinearity. If successful, this approach would provide a practical way of switching 100 milliwatt optical signals in devices of a meter in length, much shorter than is currently possible with conventional fibers.

10 GB/S TRANSMISSION OVER 100 KM USING DIRECTLY MODULATED LASERS
In work that aims to bring inexpensive local-area-network technology to larger-scale communications networks, Corning Incorporated has demonstrated a laser/fiber system in which 1550 nm "directly-modulated" light (light converted directly into an optical signal) can be transmitted at rates of up to 10 Gigabits per second over distances of 100 km between two connection points on a novel version of the commonly used "single-mode" fiber. This was done without having to compensate for error-causing dispersion effects in the fiber, in which the light signal splits up into different components owing to the fiber environment. Previously only distances of about 10 km were possible with low-cost directly modulated lasers and conventional single-mode fiber. The laser wavelength used is 1543 nm but transmission should still be good for single-channel or multiplexed systems (in which several data streams are sent simultaneously through the fiber) across the 1528-1620 nm range serviced by standard amplifiers, which strengthen optical signals at regular points. The long-distance transmission is achieved by sending the signal pulse down a special negative-dispersion fiber. With negative dispersion, the leading edge of the pulse, which is blue-shifted travels slower than the trailing edge, which is red-shifted. This serves to compress the optical pulses, reducing adjacent pulse interference to allow longer transmission distances. The main use for the new transmission mode will be in extending low-cost Ethernet-type network technology from Local Area Networks (which serve a single building or small region) into high-capacity Wide Area Networks (which serve much larger geographical regions). A somewhat slower (2.5 Gb/s) system operates at distances of up to 320 km. (Ionnis Tomkos, tomkosi@corning.com). Paper TuU6, March 20, 5:15 PM

BRAGG-TAPPING INTO NETWORKS
In the ever-changing field of optical networks, wavelength-division multiplexing (WDM) is a very flexible means of transmitting data. Now researchers at AT&T Labs are striving to make a good thing even better with a new device called a Bragg Tap. In conventional networks, optical information is transmitted from one "node," or connection point, to another. At each node, data at specific carrier wavelengths are added to or removed from the network. The Bragg Tap, on the other hand, allows a node to peel off a tiny portion of a signal rather than extracting it altogether. The invention makes possible the broadcast of a signal to multiple nodes with one wavelength, while simultaneously permitting point-to-point data transmission at other wavelengths. Sheryl Woodward of AT&T Labs (732-420-9054, sheri@research.att.com) will discuss a demonstration of broadcasting over a WDM network in session WBB2 (March 21, 4:30) and outline the benefits of high-speed, one-way connections to multiple locations with this powerful and cost-effective technology.

ALL-FIBER SWITCH EMPLOYS ACOUSTICS
Researchers at the Korea Advanced Institute of Science and Technology (Hee Su Park, heesu@kaist.ac.kr) will report on an all-fiber optical switch that can select certain wavelengths of light propagating in an optical fiber and switch them into another fiber. This capability of wavelength-selective switching is essential for next-generation "intelligent" optical networks that require dynamic control of signal paths for each wavelength. The novel device uses sound waves guided by the optical fiber, and the light remains in fibers throughout the device, leading to a highly efficient switch. The selection of the switched wavelength is easily accomplished by controlling the frequency of the sound wave. The sound wave provides a faster switching time (1/25,000 second in this work) compared to mechanical or heat-based switching mechanisms. Today's optical communications systems use a large number of closely spaced optical wavelengths as independent signal-carrying channels. Signals carried by different wavelengths can be routed to different destinations using various kinds of passive wavelength filters, but the optical network is static and not flexible. One of the key technical challenges for the new approach is to develop means to control the wavelength response of the switch. (Talk WJ4, March 21, 12:00 p.m.)

PHOTONIC ANALOG-TO-DIGITAL CONVERTERS RAMP UP
New hybrid optical/electronic devices are jockeying into position to replace slowpokes in advanced radar and communications systems. Analog-to-digital converters (ADCs) are often bottlenecks in high-bandwidth radar and analog communication systems. The devices, which convert optical, electrical, or electromagnetic signals to digital data, generally operate at a fraction of data transmission rates typical of optical fibers and antennas. Photonic ADCs are hybrid optical/electronic components that may provide high-speed alternatives to comparatively slow, conventional converters. The devices consist of optical sections which divide signals based on wavelength or timing, followed by parallel arrays of electronic channels. Because each channel only sees a fraction of the initial data train, the electronics requirements are greatly reduced. Thomas Clark of Sowilo Networks Inc. in Columbia, MD (443-259-6945, tclark@sowilo.com) will present an overview of recent advances in photonic ADC research in session WU1 (March 21, 2:00), and describe various applications, advantages, and other issues surrounding the technology.

SAGNAC INTERFEROMETER: AN INEXPENSIVE TOOL FOR MEASURING FIBER LENGTH AND ERROR-CAUSING CHROMATIC DISPERSION
Researchers in Japan have developed a simple and potentially inexpensive new tool for fixing a certain kind of error in fiber-optics networks. When a stream of optical pulses gets transmitted through a long fiber, each pulse tends to spread out as the different colors or frequencies separate. This is due to a process known as "chromatic dispersion." When this broadening is too large, one pulse can interfere with its neighbors, causing errors in data transmission. To combat this problem, one can add fiber with the appropriate length and dispersion properties to counteract this effect. But one must first know the fiber's length and average dispersion. Kazi Abedin at the Communications Research Laboratory in Japan (now visiting MIT, abedin@mit.edu) and his colleagues have designed a simple, cost-effective technique for accurately measuring these properties in fibers. It employs a "Sagnac interferometer," a device that traditionally measures rotation, such as that of the Earth. The device splits the light wave into two components which then combine or interfere with each other to provide the information about dispersion and fiber length. (ThB3)

ALL-FIBER POLARIZATION MONITORING
One way to double the information-carrying capacity of fiber-optics lines outright would be to exploit a property in light known as its polarization. Polarization describes the direction in which light's electric field vibrates. In principle, fibers could simultaneously handle two optical signals with perpendicular or "orthogonal" polarizations. But in practice, it's presently very difficult to send two polarizations through a fiber without the two signals interfering with one another. In fact, single optical signals often contain components of both polarizations. Furthermore, interference between the two polarizations is starting to show up in today's demanding communications systems as defects in the transmitted data. To detect and correct such "polarization mode dispersion (PMD)," Paul Westbrook of Lucent Technologies (908-582-3641, westbrook@lucent.com) will present a review of emerging all-fiber devices for polarization monitoring and their applications in optical telecommunications. Such monitors are little more than a piece of optical fiber. One example is a fiber that contains tiny gratings that can selectively scatter only one polarization out of the fiber. By putting several into a fiber and measuring the power scattered by each, it's possible to measure the polarization of light in the fiber. The devices present an alternative to what are known as bulk optic devices, which are bigger and require a break in the fiber to monitor polarization. The all-fiber devices are also potentially useful for the day in which polarization-based signals become feasible.(WJ1, March 21, 11:00 a.m.)

These items were prepared by Ben Stein, James Riordon, Phil Schewe, and Rory McGee of the American Institute of Physics in cooperation with the Optical Society of America and the respective OFC speakers.

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OFC Meeting, March 17-22, 2001
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