DANSK - Dansk Standard

Optical fibres - Part 1-49: Measurement methods and test procedures - Differential mode delay
 N DS/EN 60793-1-49

Annotation

This part of IEC 60793 applies only to multimode, graded-index glass-core (category A1)

fibres. The test method is commonly used in production and research facilities, but is not

easily accomplished in the field.

This standard describes a method for characterizing the modal structure of a graded-index

multimode fibre. This information is useful for assessing the bandwidth performance of a fibre

especially when the fibre is intended to support a variety of launch conditions such as those

produced by standardized laser transmitters.

With this method, the output from a fibre that is single-mode at the test wavelength excites

the multimode fibre under test. The probe spot is scanned across the endface of the fibre

under test, and the optical pulse delay is determined at specified offset positions.

Two results can be produced from the same data. First, the difference in optical pulse delay

time between the fastest and slowest mode groups of the fibre under test can be determined.

The user specifies the upper and lower limits of radial offset positions over which the probe

fibre is scanned in order to specify desired limits of modal structure. The DMD data is then