IEC 62614-1:2020 pdf download

IEC 62614-1:2020 pdf download.Fibre optics – Multimode launch conditions – Part 1: Launch condition requirements for measuring multimode attenuation
1 Scope
This part of IEC 62614 describes the launch condition requirements used for measuring multimode attenuation in passive components and in installed cable plants. In this document, the fibre types that are addressed include category A1-OMx, where x = 2, 3, 4 and 5 (50 µm/125 µm), and A1-OM1 (62,5 µm/125 µm) multimode fibres, as specified in IEC 60793-2-10. The nominal test wavelengths detailed are 850 nm and 1 300 nm. This document can be suitable for multimode attenuation measurements for other multimode categories and/or other wavelengths, but the source condition for other categories and wavelengths are not defined here. The purpose of these requirements is as follows: to ensure consistency of field measurements when different types of test equipment are used; to ensure consistency of factory measurements when different types of test equipment are used; to ensure consistency of field measurements when compared with factory measurements. This document describes launch condition requirements for optical attenuation using sources with a controlled encircled flux (EF).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 61280-1-4, Fibre optic communication subsystem test procedures – Part 1-4: General communication subsystems – Light source encircled flux measurement method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.3.1 encircled flux EF fraction of cumulative near-field power to the total output power as a function of radial distance from the optical centre of the core 3.2 multimode attenuation attenuation pertaining to multimode fibres and/or multimode fibre components, systems and subsystems 3.3 reference grade launch cord launch cords constructed with a reference grade termination at the interface to the device under test 3.4 reference grade termination connector and plug with tightened tolerances terminated onto an optical fibre with tightened tolerances such that the expected attenuation of a connection formed by mating two such assemblies is lower and more repeatable than a standard-grade termination Note 1 to entry: An adapter, required to assure the reduced attenuation, may be considered part of the reference grade termination where required by the test configuration. Note 2 to entry: IEC 61755-6-2 defines reference grade terminations for 50/125 µm fibre.
4 Background on multimode launch conditions
There have been a wide range of launch conditions used for testing multimode fibre components and systems. Light sources, typically used in measuring attenuation, can produce varying modal distributions when launched into multimode fibre. These differing modal distributions, combined with the differential mode attenuation (DMA) inherent in most multimode components, commonly cause measurement variations when measuring attenuation of multimode components. For example, attenuation measurement variations can occur when two similar light sources or different launch cords are used. Legacy (LED based) applications had a wide power budget, which in most cases masked the variance in results between the factory and field measurement. As technology has evolved, the system requirements for attenuation have become more stringent. Demanding application requirements are driving the need for accurate and reproducible multimode attenuation measurements over a variety of field-test instruments. Attenuation measurement experiments, with different instruments having the same standards compliant set up, produce measurement variations that are induced by their differing launch conditions.Experts have concluded that the launch condition should be expressed at the interface between the test instrument launch cord and the terminated fibre to be tested. That is, the launch condition should be based in part on the measured near field at the output of the launch cord. The key to making reproducible attenuation measurements across various sources is to narrowly constrain the range of power distribution at large radii so that all compliant sources produce closely agreeing attenuation measurement results. This is because the variation in the allowed power distribution at large radii across different sources translates directly into variability of attenuation measurements. Smaller power variations enable more reproducible attenuation measurements.