Trends in fiber-optic connector standardization

by THOMAS BALL and BRUCE G. LeFEVRE

Fiber-optic connector standards are defined and developed by components organizations (e.g., iec sc86b internationally and tia FO6.3 in the United States) for use by system designers, equipment manufacturers, and installers. They are often referenced as requirements in physical layers of systems standards developed by user groups. At present, standards and specifications covering approximately 25 basic connector types are finalized or in progress in the Telecommunications Industry Association and the International Electrotechnical Commission (iec). About two-thirds of these standards and specifications were initiated after the connectors had come into broad usage in fiber-optic networks (primarily telephony) and the need for standardization was apparent. The remainder are new or enhanced technology designs, geared toward multiple fiber connections for consideration in new system requirements from Fibre Channel, atm Forum, Gigabit Ethernet, and others.

As fiber-optic connector technology evolved from telecommunications to include data and multimedia applications, connector standardization moved from envelope (single limit) dimensions and third-party inspections to a system of "interlinking" standards. These standards provide user groups with flexible alternatives to developing and maintaining sets of procurement (quality assurance) specifications, and assurance of multiple-vendor interconnection performance. The interlinking standards, started by iec sc86b, have five classifications:

Interface--Defines necessary and suffi-

cient dimensions (and parameters) for mechanical intermateability of connectors with adapters and device receptacles.

Tests/measurements--Provides meth-

ods for measuring critical parameters and evaluating performance under various environments.

Performance--Defines the schedule of

tests and measurements, with defined conditions, severities, and pass/fail criteria, to prove fitness of design and quality for specific applications and environments.

Reliability--Provides tests, measure-

ments, and analytical methods for projecting failure rate as a function of time. The period for which a connector continues to meet required performance criteria is an estimate of its life expectancy.

Quality assurance--Provides methods

for ensuring consistent product quality over time via inspection and tests linked to sampling procedures.

Work is under way to add an additional important link to the system. The interface standard is mechanical only; it guarantees physical fit but does not directly address parameters affecting position and alignment of the optical waveguides. iec/sc86b/wg6 is currently working to include these in an optical interface standard, with the expectation that components conforming to a particular class of interface will give a certain minimum level of performance (reflectance and attenuation) when randomly mated. There is active debate over how this should be done and whether it will achieve the objective.

tia FO6.3 is developing intermateability, reliability, and test and measurement standards and supports the iec sc86b work on performance and optical interface standards with U.S. Technical Expert participation and Technical Advisory Group vote and comments. Other standards bodies maintain liaisons with the iec to avoid conflict and redundancy where possible.

When completed, the interlinking standards system will provide more-flexible means of specifying connector requirements for a range of applications. q

Thomas Ball is manager of fiber-optic standards development at amp Inc., Harrisburg, PA, and is chair of tia FO6.3 and technical advisor and chief delegate for the U.S. National Committee to iec sc86b. He can be reached at tel: (717) 592-6268 or e-mail: [email protected]. Bruce G. LeFevre is a member of technical staff at Network Cable Systems, Lucent Technologies, Norcross, GA. He chairs standards working groups tia FO6.3.8 and iec sc86b/wg4 and serves as a U.S. Delegate to iec Bio 86B. He can be reached at tel: (770) 798-2837 or e-mail: [email protected].