Consortium targets all-optical links

Consortium targets all-optical links

GEORGE LAWTON

Three regional Bell operating companies--Bell Atlantic Corp., BellSouth Corp. and Pacific Telesis Group--plus Bell Communications Research and three AT&T organizations--Bell Laboratories, Network Systems Group and Communications Services Group--have formed the Multiwavelength Optical Networking Consortium. Dubbed Monet, the consortium aims to accelerate the research and development of all-optical networking technologies for military and commercial applications. The consortium members will work together to deploy different optical architectures and evaluate various networking structures for performance and cost.

The consortium is funded by a five-year, $54 million allocation from the Department of Defense, Advanced Research Projects Agency in Washington, DC. Armed with the results of the Monet study, ARPA aims to improve the capacity and performance of the U.S. military, national and global information infrastructure. To support optical component and equipment studies, the agency is distributing $46 million to other consortia that comprise universities, government agencies, private companies and research laboratories.

The U.S. government has decided to invest millions of dollars to develop all-optical technology even though private industry is interested in the same technology. The answer, explains Adel Saleh, project manager of Monet, and head of the packaging and subsystems research department at Murray Hill, NJ-based AT&T Bell Laboratories, is that "there are risks involved. A company like AT&T might hesitate to venture in this direction. But when ARPA doles out investigation funds, the researchers are happy to do it. For its part, ARPA performs an important service because it claims the country needs aggressive, all-optical networking. We do this research to increase network flexibility, reliability and performance."

Bertram Hui, deputy officer of the defense science office at ARPA, declares that Monet is a last-ditch effort to determine whether optical networking has compelling applications for the Department of Defense. He states, "One difference between Monet and other projects is that usually the government supports research for two years and then gets out. We want to see this project through for five years. If it does not work, we will stop. On top of that, we will have businesses like AT&T and Bell Atlantic looking at [optical networking]. If it is really good, they will run with it."

Applying all-optical networking promises to benefit military and civilian applications. On the military front, the armed forces seek to obtain secure, real-time knowledge of enemy activities and instantly communicate that information to all their branches. On the commercial front, telephone companies are enthused because optical technology allows the simultaneous transmission of voice, video and data signals.

According to Dan Stanzione, president at AT&T Bell Laboratories, "This research should move us closer to an all-purpose network that will support a range of telecommunications standards. It will be highly efficient, accommodate future growth, and be a better bridge between commercial and defense-related networks."

Adds George Heilmeier, president at Bellcore in Livingston, NJ, "This consortium will move us toward an industry consensus among telecommunications network operators, equipment suppliers, operations software makers and standards forums on how to build a national-scale optical networking layer."

Ambitious goals

The consortium`s goals are ambitious and encompassing. Using optical networking, the group proposes to investigate local-exchange and long-distance network architectures; network management and control systems; telecommunications interface specifications; and the technical and economic viability of wavelength-division multiplexing in commercial and defense communications networks.

These networks would be capable of supporting all currently employed or future telecommunications standards, enabling graceful growth. The standards include synchronous optical network services ranging from optical carrier, level 1 (51.8 megabits per second) to OC-192 (9.953 gigabits per second) and asynchronous transfer mode broadband, multimedia and high-speed networking services.

To push all-optical technology to the point of commercialization, the networks are expected to support a variety of format-independent, bit-rate-independent and protocol-independent services. They would thus offer increased operational flexibility and economic advantages.

Because all-optical networking enables communications without the conversion of optical signals into electrical signals, this technology empowers networks with the capability of simultaneously and independently conveying several data streams over optical fiber. One optical fiber is, therefore, able to carry multiple channels of information, and each channel is separate and distinct from the others.

Hui advises that the consortium will explore two types of all-optical network architectures. One type would use a star architecture, in which a fixed number of nodes would communicate by using tunable lasers or receivers over a large number of frequencies. The other type would use approximately four to eight wavelengths. Signals would be wavelength-converted at optical routers; from there, the signals would be fed onto another network at a different wavelength.

Optical architectures scale well for global networks. A key problem, though, is the cost of producing the components needed for all-optical networks. Hui says the components ideally would be single chips that contain multiple lasers and modulators. Otherwise, the cost of independent optical components is too high to build reasonable commercial all-optical networks. Adds Hui, "Affordable lasers with multiple wavelengths do not yet exist."

Another crucial and expensive component is the wavelength router needed to optically interface a signal from one network to another. According to Saleh, "Wavelength conversion is one of the most important and limiting parts of this technology. There are dozens of talks on this technology, but not a single network is ready to go."

An interesting attribute of optical technology is that separate wavelengths are able to carry different protocols simultaneously down the same fiber. During the Monet trials, the network will carry Sonet signals to OC-192, ATM signals and such analog traffic as video and satellite feeds. Optical networking, therefore, has the bandwidth and the potential to increase the flexibility and economic advantages in commercial networks. Network providers, for example, could lease specific wavelengths to their customers for any desired protocol.

Other studies

ARPA is also funding several smaller all-optical networking projects. It is giving $7 million to IBM Corp. and Corning Inc. to develop an all-optical star network that has 32 channels. This project will draw upon IBM`s experience as a computer vendor and as a producer of such all-optical networks as Rainbow 2 (see Lightwave, January 1995, page 1) and Muxmaster (see Lightwave, March 1995, page 1). Corning will use its experience in fiber, optical amplifiers and planar couplers to produce high-fiber-count, wavelength-division multiplexing couplers for the network.

Another ARPA-sponsored project involves the $10 million New Optical Networks Technology Consortium. It is a follow-on to the ONTC all-optical network demonstrated at the Optical Fiber Conference `95 show (see Lightwave, February 1995, page 6). The participating companies included Bellcore, Northern Telecom, Columbia University, Hughes, Lawrence Livermore Laboratories, United Technologies, Rockwell International, Pacific Bell and Sprint.

These companies plan to implement the off-the-shelf components and equipment developed for the ONTC network. The team will demonstrate an open network in the San Francisco Bay Area that connects Lawrence Livermore Laboratories, Lawrence Berkeley Laboratories and Pacific Bell`s San Ramon Laboratory. Also in the works is an experiment that calls for modulating wireless receiver outputs onto a single wavelength. This methodology could be used for carrying multiple radio frequencies over a single fiber. q

George Lawton is a freelance writer based in San Francisco.

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