What is BS EN 60793-1-41 - Optical fibres about?
BS EN 60793 is a series on optical fibres. Optical fibres are flexible, transparent fibres made by drawing glass (silica) or plastic to a diameter slightly thicker than that of human hair. BS EN 60793-1-41 describes three methods for determining and measuring the modal bandwidth of multi-mode optical fibres (see IEC 60793-2-10, IEC 60793-30 series and IEC 60793-40 series). The base-band frequency response is directly measured in the frequency domain by determining the fibre response to a sinusoidally modulated light source. The base-band response can also be measured by observing the broadening of a narrow pulse of light. The calculated response is determined using differential mode delay (DMD) data. The three methods are:
- Method A – Time-domain (pulse distortion) measurement
- Method B – Frequency-domain measurement
- Method C – Overfilled launch modal bandwidth calculated from differential mode delay (OMBc)
Methods A and B can be performed using one of two launches: an overfilled launch (OFL) condition or a restricted mode launch (RML) condition. Method C is only defined for A1a.2 (and A1a.3 in preparation) multi-mode fibre and uses a weighted summation of DMD launch responses with the weights corresponding to an overfilled launch condition. The relevant test method and launch condition should be chosen according to the type of fibre.
Who is BS EN 60793-1-41 - Optical fibres for?
BS EN 60793-1-41 on optical fibres is useful for:
- Telecommunication component manufacturers
- Telecommunication equipment manufacturers
- Design engineers
- Quality control personnel
Why should you use BS EN 60793-1-41 - Optical fibres?
Optical fibres are used most often as a means to transmit light[a] between the two ends of the fibre and find wide usage in fibre-optic communications, where they permit transmission over longer distances and at higher bandwidths (data transfer rates) than electrical cables. BS EN 60793-1-41 describes a procedure that describes light launch conditions to the test fibre for the purpose of achieving a uniform overfilled launch with a laser diode or other light sources. Light launch conditions are established through the use of a mode scrambler. The mode scrambler is positioned between the light source and test fibre to produce a radiation distribution overfilling the test fibre core and numerical aperture, irrespective of the spatial radiation properties of the light source.
A "mode scrambler" is a device, which is positioned between the light source and test fibre to control launching conditions. A particular mode scrambler design is not specified. It should be emphasised that the performance of these scramblers depends upon the launch optics and fibre sizes (core and NA) used in the actual construction. The mode scrambler, regardless of design, is sufficient to reliably reproduce the launching conditions of BS EN 60793-1-41 to the test fibre. If the launching conditions to the test fibre remain stable enough to meet the required launching conditions for all subsequent measurements, the qualification tests need not be made in situ and are not required for every test using the mode scrambler. Such stability may be obtained, for example, by permanently pig-tailing or permanently connecting rising the source to the mode scrambler. For many modes scrambler designs, however, the launching conditions produced depend on the source/mode scrambler alignment and interaction with any intermediary optics such as connectors or optical imaging systems. If the source or any component in the optical system is changed, the qualification tests are repeated. Using BS EN 60793-1-41 you can describe three methods for determining and measuring the modal bandwidth of multi-mode optical fibres.
What’s changed since the last update?
BS EN 60793-1-41:2010 supersedes BS EN 60793-1-41:2003. BS EN 60793-1-41:2010 includes a technical change with respect to BS EN 60793-1-41:2003. These include:
- The addition of a third method for determining modal bandwidth based on DMD data and to improve measurement procedures for A4 fibres.
