by Rosemary McGlashon
IEC SC86B/WG6 (“Standards and Specifications for Fibre Optic Interconnecting Devices and Related Components”) has made considerable progress with the publication of several singlemode optical interface standards from the three-tier IEC 61755 series.
The documents contain the essential information to ensure that products conforming to the standards will work together repeatedly to a known level of optical performance and that the performance is maintained over the environmental extremes specified.
Level 1 of the series, IEC 61755-1 (“Optical Interfaces for Singlemode Non-dispersion Shifted Fibres”), was published in 2005. It contains “General and Guidance” information, including definitions, the grading system, and the structure of the document series.
Level 2, IEC 61755-2 series, is the fibre optical interface. This is currently composed of two documents published in 2006: IEC 61755-2-1 for nonangled and IEC 61755-2-2 for angled physically contacting non-dispersion-shifted singlemode fibre. The documents give performance grades against both insertion loss and return loss and the criteria for meeting these grades based on theoretical models for these properties.
Level 3, IEC 61755-3 series, is the connector optical interface. This currently has four documents published in 2006: IEC 61755-3-1, -2, -5, and -6 for cylindrical ferrules (zirconia and copper/nickel alloy). Work is in progress on companion documents for plastic rectangular ferrules (thermoset and thermoplastic).
Level 3 documents contain the essential features that are functionally critical to the optical attenuation and return loss performance of an optical interface in the mated condition. The standards define the material of the ferrule, location of the fibre core in relation to the datum target, and a number of key parameters including the endface radius, fibre undercut, and apex offset.
WG6 is also working on the Level 2 multimode interface. There is still considerable work to do on this since the theoretical models are more complicated than for standard singlemode. There is scope to add more fibre types to Level 2 or connector material types to Level 3 as required.Rosemary McGlashon is European technical manager at 3M United Kingdom plc and secretary of IEC SC86B/WG6. She can be reached at rmcglashon1@ mmm.com.