Fiber-optic system design guides undergo upgrades

Fiber-optic system design guides undergo upgrades

THOMAS F. McINTOSH

The design methodology for fiber-optic systems in the form of design guides is progressing through U.S. and international standards bodies. These design guides define the fiber-related information required, the available generic loss and bandwidth models, and the process design steps. In many cases, the design is an iterative process. Therefore, system designers can investigate different configurations to optimize the system parameters most important for the application.

The design methodology for multimode fiber systems has been documented with the publication of the Electronic Industries Association/Telecommunications Industry Association`s eia/tia-626, "Multimode Fiber-Optic Link Transmission Design," dated December 1995. This guide was generated under the guidance of subcommittee FO-2.2, Fiber Optic Local Area Networks, chaired by James D. Kevern, AMP Inc. It addresses digital fiber-optic links with capacities to approximately 500 Mbaud that use graded-index multimode optical fiber and either light-emitting diode or laser sources. Gair Brown, at the Naval Surface Warfare Center, was the document editor and major technical content contributor.

The design methodology contained in eia/tia-626 has been adopted for publication as an international design guide by the International Electrotechnical Commission`s (IEC) subcommittee 86C, working group 1, chaired by Allen H. Cherin of Lucent Technologies Inc., with this column`s author as document editor.

IEC 1282-2, "Design Guide for Multimode Digital Systems," has undergone working group review and was forwarded to the IEC in Geneva last June for translation and distribution as a Committee Draft with Vote (CDV). This design guide incorporates all the technical methodology of eia/tia-626 but is edited for IEC format and omits most of the tutorial information contained in the U.S. document.

IEC 1282-1, "Design Guide for Single-Mode Digital and Analogue Systems," was also forwarded to Geneva last June as a CDV. This document was edited by Kiyoshi Nawata and Mitsuaki Nishie, Sumitomo Electric, and is tightly based on eia/tia-559, "Single-Mode Fiber Optic System Transmission Design," March 1989. Limited design rules for analog systems (cable-TV systems) were incorporated.

Presently, an initiative is under way in TIA FO-2.1/6.6 joint subcommittee on singlemode optical fiber telecommunication systems, chaired by Dr. Cherin, to produce a much-needed revision of eia/tia-559. This outdated document addresses the design of a regenerator section in which the transmitter and receiver come from the same vendor. In addition, only laser systems operating in the 1300-nm region over dispersion nonshifted singlemode fiber are included.

A task group (TG1) under the leadership of Gair Brown has met, reviewed the relevant documentation and agreed on the scope of the new design guide. This task group has further developed a detailed document outline and is presently collecting information from U.S. and international standards bodies, including the IEC and the International Telecommunication Union. New technologies, such as Sonet/SDH with vendor-independent interoperability, optical-fiber amplifiers and dense wavelength-division multiplexing, will be included.

Other items under study encompass the system design constraints of fiber nonlinearities, polarization mode dispersion, and dispersion compensators and compensating systems. The task group welcomes new members who can make technical contributions to this work. Call Dr. Cherin at (770) 798-2619 or Gair Brown at (540) 653-1579. n

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