Terabit transmission records, communicating with chaos, and fiber optics with fluids

PRESSROOM AND PRESS LUNCHEON
A media and public relations lounge will be located at the conference from March 18 through March 21. It will be available for members of the press and for public relations officers of exhibiting companies. There will also be a working media room available.

In addition, OFC will host a scientific press luncheon from noon to 2:00 PM on March 19 in Room 206 A - B. The purpose of this luncheon is to give the press an in-depth look at select OFC topics. Following their talks, the speakers will be available to field reporters' questions. A press release containing more details on the press luncheon will be available in the next two weeks.

PLENARY SESSION
Optics and the Internet, the value chain of optical networking, and an avuncular fiber engineer's observations on optical fiber communications are the subjects of plenary talks by three industry leaders. Vinton G. Cerf (Senior Vice President of Internet Architecture, Worldcom), Tingye Li (lightwave communications consultant, formerly of AT&T Labs-Research), and Geoffrey Moore (Chairman and founder of the Chasm Group) will deliver their plenary addresses Tuesday morning (8:30-11:00AM, March 19, 2002).

SOME HIGHLIGHTS OF THE TECHNICAL SESSIONS:

TRANSMISSION RECORDS IN THE TERABITS
As demand for bandwidth increases, so has research into pushing the limits of fiber optic transmission rates. Several groups are presenting record-setting results at OFC this year, including an announcement by Agere Systems that, to their knowledge, they have set a new record in transmission capacity: 3.2 terabits (trillion bits) per second (Tb/s) over a 1,000-km fiber using DWDM (dense wavelength division multiplexing). DWDM is attractive for future optical networks because systems take up less floor space and consume less power, resulting in lower system costs. In DWDM systems different colors of light signals are combined or "multiplexed" and transmitted through a single optical fiber, allowing transmission capacity to be increased by several orders of magnitude. The transmission being reported by Agere consisted of 40 channels operating at 80Gb/s each, and was made possible using the state-of the art components and subsystems. Contact: Glen Haley, glenhaley@agere.com (Paper TuA5, Tuesday, 12:15 PM).

TRANSOCEANIC CLASS TRANSMISSION RECORD
A paper by Mitsubishi Japan focuses on the highest transmission rate to date over long distances, simulating the feasibility of high-bandwidth transoceanic fiber-optic trunk lines. Researchers Katsuhiro Shimizu (shimi/ocrl@tellurite.stanford.edu) and Takashi Mizuochi achieved what they say is a transoceanic class transmission rate record of 1.3 Tb/s over 8,400 km on a single fiber. The group used 65 channels at a bit-rate of 20 Gb/s, which they say offers the best solution for the present in terms of potential for reduced cost, ease of operation, and reliable transmission when compared with bit rates of 10 Gb/s (the current standard) and 40 Gb/s. The authors also developed novel technologies to improve the signal-to-noise ratio to solve fiber nonlinearity difficulties. The authors contend that this development opens new possibilities for next-generation submarine cable systems and terrestrial systems that could connect Japan, the US, Asia and Europe, as well as provide the trunk infrastructure for connecting the major cities of the world (WX4, Wednesday, 5:00PM).

PRACTICALLY CHAOTIC COMMUNICATION
The highest bit rate ever achieved with a chaotic communication system is now good enough to meet commercial communication standards--potentially leading to highly secure information exchange at reasonable transmission rates. Shou Tang and Jia-ming Liu (liu@ee.ucla.edu) of UCLA will describe a system consisting of coupled, chaotic lasers that transmit data hidden in a chaotic waveform at 2.5 Gbits/s (ThD2, Thursday, 9:30AM).

PHOTONICS INNOVATION: MICROFLUIDIC FIBER OPTICS
Holey fibers, consisting of arrays of hollow channels that run the length of optical fibers, provide transmission characteristics that promise a host of intriguing applications. Inserting fluid into holey fibers has now opened the door to a whole new class of devices with tunable transmission characteristics. Microfluidic fiber optics are the subject of a paper presented by a group of researchers from Lucent, Optical Fiber Solutions, and Harvard University. A small potion of fluid placed in a holey fiber serves as a liquid plug that can be moved along a fiber's length. By positioning the liquid in specially designed fibers that have actuators and pumps incorporated on their surfaces, the researchers (Robert Windeler, rsw@lucent.com) can dynamically tune devices, including wavelength-selective attenuators and switchable broadband attenuators. The researchers propose that their unusual innovation is an important new direction for photonics research has the potential to provide essential technologies for next-generation optical networks (ThK1 and ThK3, 11:00AM and 11:30AM, Thursday).

MICRO-RING RESONATORS: THE FIRST POLYMER MICROPHOTONIC DEVICES
Researchers at the University of Southern California (Payam Rabiei, rabiei@usc.edu) have used polymers to make micro-photonic components. Micro-photonics is the combination of very small optical components on a chip. The group constructed a microscopic polymer version of an electro-optic modulator, a device that employs electric fields to switch optical signals on and off. To the researchers' knowledge, this is the first demonstration of polymers in microphotonics and the first demonstration of a micro-photonic electro-optic modulator. These polymer ring resonators can vary in diameter from 40-400 microns, where one micron is a millionth of a meter. An advantage of polymer components is that they are potentially inexpensive and relatively easy to manufacture. Also it is possible to incorporate them into standard CMOS electronic circuits, making them compatible with present technology (TuF6, Tuesday, 12:15 PM).

OPTICAL FLOW SWITCHING - NO NEED TO BANISH ELECTRONIC ROUTERS
A group of researchers from The Massachusetts Institute of Technology (MIT) has found a way to reconcile all-optical signal switching without getting rid of the current electronic routers which make up the backbone of most Wavelength Division Multiplexing (WDM) long-haul networks. Bishwaroop Ganguly (ganguly@mit.edu) and Vincent Chan believe that their concept of Optical Flow Switching, which uses cheaper optical switches at electronic router sites, would allow for optical switching of large data transmissions with smaller transmissions being handled electronically. Currently electronic routers translate incoming optical transmissions to electronic data, re-modulate them, and then translate them back to optical information for transmission over a new fiber toward their final destination. The MIT researchers suggest that some of the cost of this electric translation, which becomes much more expensive as transactions get larger (hundreds of megabytes) because the routers must be much faster, can be solved by allowing all-optical switches, which are cheaper for high data rate transmissions, to be used in conjunction with electronic switching electronic routers. Ganguly and Chan say this technique, which has been tested on the ONRAMP next generation Internet testbed, could go a long way to alleviating electronic bottleneck problems in next-generation optical networks (WG2, Wednesday, 9:00AM).

QUANTUM WELLS AS ULTRAFAST GENERATORS OF ZEROES AND ONES
Recent work at Bell Labs has uncovered a potentially important fiber-optics application for quantum wells, nanometer-scale sandwiches in which the "bread" is one semiconductor material and the "filling" is another type of semiconductor. Quantum wells have properties that depend on both the semiconductor materials and the thicknesses of the layers in the sandwich. Studying gallium nitride/aluminum gallium nitride (GaN/AlGaN) quantum wells, researchers (including Claire Gmachl, cg@lucent.com, Hock Ng, and coworkers at Bell Labs) have discovered ultrafast energy jumps of electrons in the quantum wells. Occurring on a timescale of 200 femtoseconds (one femtosecond is a quadrillionth of a second), this process could potentially be exploited to make ultrafast modulators, devices that switch light pulses on and off at extremely rapid rates. Such ultrafast modulators would be highly desirable for fiber optics telecommunications: The faster a light beam can switch on and off, the faster an optical system can transmit data. The work that the researchers are presenting at OFC 2002 is the first step towards such devices. In addition to observing the ultrafast, 200-fs electron energy jumps, one of the fastest ever measured for energy transitions in a semiconductor in this wavelength range, they succeeded in demonstrating the suitability of the GaN/AlGaN material system for the fiber-optic wavelength range. The next steps will be to design and demonstrate optoelectronic devices based on these ultrafast energy transitions (TuF2, Tuesday, 11:15 AM).

ALL-OPTICAL MULTIPLEXING AND DEMULTIPLEXING WITH SEMICONDUCTOR MICRORINGS
Optical communication systems commonly take advantage of a technique called "multiplexing," in which several data streams are simultaneously sent down a fiber. This technique multiplies the amount of data by the number of data streams, or "channels" that are used. When the optical information is decoded, however, the data streams need to be separated, a process called "demultiplexing." A University of Maryland group (P.-T. Ho, ho@eng.umd.edu) has now demonstrated a novel scheme for all-optical multiplexing/demultiplexing, one that uses nonlinear semiconductor microring resonators. These compact micro-resonators (only 20 microns in diameter) were fabricated using gallium arsenide/aluminum gallium arsenide semiconductors. In these structures, laser light can cause the microring's refractive index, the amount of which it can bend or re-direct light, to change by means of a process called two-photon absorption. The micro-resonators possessed quality factors close to 10,000 - the highest values ever reported for semiconductor optical resonators of their type. The high Q factors indicate low power losses in the device and other attributes which are important factors for efficient signal processing. The devices have potential applications in high-speed, all-optical time-division multiplexing data in communication systems (TuU4, Tuesday, March 19, 5:30 PM).

FIRST FIELD TEST OF 160 GIGABIT-PER-SECOND TRANSMISSION CHANNEL
To maximize data transmission speeds, fiber-optics systems commonly send multiple optical signals of different colors or "wavelengths"; this is called wavelength division multiplexing (WDM). For each WDM wavelength or "channel," the transmission rate is further increased by doing the following: one sends multiple streams of data in such a way so that the individual streams are slightly offset with respect to one another in time. This is called TDM, or time division multiplexing. For transmission rates of up to 40Gbit/s per WDM channel, TDM is performed in the electrical domain (ETDM). Presently, companies are planning to install 40 Gbit/s ETDM systems. For next-generation TDM systems with 160 Gbit/s bit rates, electrical signal processing does not presently work.. Optical signal processing (OTDM) must be introduced. Researchers are making remarkable progress in this front. In a collaboration between Heinrich-Hertz-Institut (HHI) in Berlin, Germany and Lucent Technologies Nuernberg, Germany, researchers (including Reinhold Ludwig, Ludwig@hhi.de) have performed the first 160 Gbit/s field experiment (based on 40Gbit/s ETDM), using part of the fiber network of German Telecom near the city of Darmstadt. The tests were carried out in 116 km of standard single mode fiber (SMF), which is the type of fiber predominantly installed in most countries including the USA and Europe. While numerous technical issues still need to be addressed, these field trials show that this technique has a promising potential for practical applications. One of these issues, in-service quality monitoring at the full line rate of 160Gbit/s based on an optical sampling technique, is also a major pursuit at HHI and other research institutes (TuA1, TuN5, ThU1).

COMBINING SOUND AND LIGHT FOR MORE FLEXIBILITY
As traffic on wavelength division multiplexing (WDM) networks increases, so does the need to make the systems more flexible. One of the ways of doing this is to use an optical add/drop multiplexer (OADM) to add, remove, or pass through single-wavelength signals from the main fiber line that is made up of many wavelengths propagating together. Researchers from the University of Valencia in Spain believe they have found a way to make a more dynamic OADM - by using sound. Antonio Diez (Antonio.diez@uv.es) and his colleagues combine the spectral properties of Bragg gratings with the dynamic nature of the acousto-optic affect (using acoustic waves to modify the properties of the light in a fiber) in a new OADM design. Their prototype has a response time of 95 microseconds, and the researchers believe that responses of less than 50 microseconds are achievable with the advantage of being a crosstalk-free OADM (WC5, Wednesday March 20, 10:00AM).

FIBER OPTICS FOR ISLANDS AND COASTS
Presently, it is difficult to deploy high-speed optical fiber communications between islands and along coasts. But the markets for such systems are growing. Researchers are striving to develop high-capacity optical transmission systems for these areas without the use of repeaters, devices installed at specific intervals of the fiber-optic line to boost an optical signal. However, repeaters are inconvenient to install offshore. One particularly attractive solution is the remotely pumped amplifier, where pump power is inserted at the end of the transmission line while the amplification is taking place remotely in a dedicated region of the fiber span. However, transmission systems presented up to now either were limited in the common fiber optic wavelength range (the C band, about 1525-1565 nm wavelength) or in transmission distances shorter than 200 km. Richard Neuhauser of Siemens AG (Richard.Neuhauser@icn.siemens.de) and colleagues will present a new remote pump scheme enabling, for the first time, high capacity transmission for distances of greater than 200 km in two wavelength bands. Over an unrepeatered distance of 220 km, the researchers successfully demonstrated transmission of 3.2 Tb/s (42.5 Gb/s over 80 data streams, or channels) in the C and the L band (the extended wavelength band, about 1570-1610 nm). They will discuss the ultimate limits of this technique as well as potential improvements (TuR2, Tuesday, 4:45 PM).

COMPUTING OUTAGES WITH IMPORTANCE SAMPLING
When designing a fiber-optics transmission system, one must plan carefully to ensure that communications signals will drop out, or become undetectable, no more frequently than the typical industry standard of one-thousandth of one percent (10^-5) of the time. When an optical signal contains sufficiently large numbers of errors due to noise, or random fluctuations, a receiver cannot properly detect the signal. These events are known as "outages" and translate into service interruptions. A fact of life in optical networks, outages must be anticipated in the design of a system. In paper TuI7 (Tuesday, 3:30 PM), Ivan Lima and colleagues at the University of Maryland-Baltimore County (lima@engr.umbc.edu) will demonstrate a new technique for computing the probabilities of outages induced by the combined effects of polarization, which is the direction of a light wave's electrical field. Polarization-related errors are a serious problem in long-distance transmission systems. For example, polarization dependent loss (PDL) occurs when the signal suffers a loss that is a function of its polarization. Traditional "Monte Carlo" techniques for estimating polarization errors are too slow for efficiently computing the relatively rare probabilities (10^-5-10^-6) of polarization-related outages. Lima and his colleagues instead adopt an approach known as "importance sampling." Importance sampling makes rare events occur more frequently than they ordinarily would, then weights these rare events downward to get the correct statistical results. With this approach, the researchers computed polarization-related outages using less than 1% of the computational time of standard techniques without a loss in accuracy. Lima and colleagues believe that importance sampling will soon become an essential technique for the design of optical-fiber transmission systems. Importance sampling was first applied to optics in an OFC 2001 paper by Northwestern's Gino Biondini, who is now at Ohio State, and is now being applied in several papers at OFC 2002 (including WI2, WI3 and WI7).

EXAMINING EFFICIENCY IN AN ALL-OPTICAL NETWORK
In traditional fiber-optics communication systems, O-E-O is a familiar refrain: It's the conversion of an optical (O) signal to an electrical (E) one, then back to the optics realm (O). Such conversions have been necessary at a fiber-optics system's nodes, or connection points, where optical signals can be processed or rerouted. That's because conventional nodes contain electrical devices for processing optical signals. However, emerging all-optical communications networks eliminate a lot of the O-E-O conversion. This reduces the amount of electronic equipment in an optical network, and brings many benefits such as potentially lower costs and faster provisioning. Nonetheless, all-optical systems pose challenges of their own. All-optical systems take advantage of optical bypass, in which optical signals passing through a node stay in the optical domain if they do not require any processing at the node. One aspect of optical bypass that needs to be dealt with is wavelength assignment. If traffic stays in the optical domain, then it uses the same wavelength (assuming all-optical wavelength conversion is not available). Thus, it becomes important that the "wavelength continuity constraint" does not result in a loss of network efficiency. Using realistic conditions, Jane Simmons of Corvis Corporation (jsimmons@corvis.com) will show that even with a significant amount of optical bypass, there is virtually no loss of network efficiency in an all-optical express network backbone topology. She concludes that the small amount of wavelength conversion that occurs in all-optical express networks (for example, due to the small amount of regeneration needed for restoration in quality of the optical signal) is sufficient to achieve virtually the same network efficiency as can be achieved with full wavelength conversion at all nodes (TuG2, Tuesday, 11:30 AM).

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

For more information, please contact Ben Stein (301-209-3091, bstein@aip.org), Rory Richards (301-209-3088, rrichard@aip.org), or James Riordon (301-209-3084, jriordon@aip.org), of the American Institute of Physics To register as a member of the media, please contact Elizabeth Renz (202-416-1956, erenz@osa.org) of the Optical Society of America.

Also see the OFC website at http://www.ofcconference.org/

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OFC 2002
March 17-22, 2002
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