IEC develops system guidelines
BY ALLEN H. CHERIN
Working Group 1 (WG1) of the International Electrotechnical Commission (IEC) Subcommittee SC86C has developed a number of informative system guidelines related to the design and evaluation of singlemode and multimode optical-fiber communication systems. Three of the guidelines support a statistical methodology for designing and analyzing singlemode communication systems. The statistical treatment of transmission parameters has become increasingly important to the process of designing cost-effective high-bit-rate systems. The statistical treatment of attenuation, polarization-mode dispersion (PMD), and chromatic dispersion are outlined in the following guidelines:
- IEC 61282-2, Design guide for singlemode digital and analog systems. This published document includes both a worst-case and statistical model for calculating the attenuation of an optical link.
- IEC 61282-3, Guideline for the calculation of polarization-mode dispersion in fiber-optic systems. This guideline describes methods for calculating PMD and differential group delay due to the optical-fiber cables and optical components in an optical link. Examples are given to illustrate the methods for calculating total optical-link PMD from typical cable and optical-component data. The calculations include the statistics of concatenating individual optical-fiber cables drawn from a specified distribution.
- IEC 61282-8, Guideline for the statistical treatment of chromatic dispersion in singlemode fiber-optic communication systems. This guideline describes methods for calculating the chromatic-dispersion concatenation statistics of an optical link utilizing the statistics of the different fiber products within the link. The concatenation statistics depend on the assumption that chromatic dispersion adds in a linear fashion and invokes the central limit theorem. Tom Hanson (Corning Inc., USA) is the project leader for both the PMD and chromatic-dispersion guidelines. These guidelines are currently being reviewed and voted upon by the national committee members of IEC SC86C.
SC86C WG1 is also working on guidelines related to nonlinear effects and dispersion compensation in singlemode fiber-optic systems:
- IEC 61282-4, Guideline to accommodate and utilize nonlinear effects in singlemode analog and digital fiber-optic systems. These nonlinear effects occur at high optical powers and include stimulated scattering and phenomena due to the Kerr effect in fibers. They can either hinder or enhance signal transmission.
- IEC 61282-5, Guideline for the accommodation and compensation of dispersion in fiber-optic communication systems. Several methods are described and are applied so far to links with dispersion-unshifted fiber only. Felix Kapron (Corning Inc., USA) is the project leader of these guidelines, which are currently being reviewed and voted on by the national committee members of IEC SC86C.
WG1 is cooperating through active liaison with the International Telecommunication Union (ITU) to produce guidelines that will complement ITU draft Recommendation G.dsn, "Optical systems design and engineering considerations."
Allen H. Cherin chairs IEC SC86C WG1 and represents Lucent Technologies on several IEC and TIA committees. He can be contacted at (770) 798-2619; fax: (770) 798-4654; e-mail: email@example.com.