What is BS EN IEC 60793‑1‑49 - Optical fibres about?
BS EN IEC 60793 is a series on optical fibres. Optical fibres are used most often as a means to transmit light between the two ends of the fibre and find wide usage in fibre-optic communications. BS EN IEC 60793‑1‑49 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.
BS EN IEC 60793‑1‑49 describes a method for characterizing the modal structure of a graded-index multimode fibre. This information is useful for assessing the bandwidth performance of fibre especially when the fibre is intended to support a range of launch conditions, for example, those produced by standardized laser transmitters.
Who is BS EN IEC 60793‑1‑49 - Optical fibres for?
BS EN IEC 60793‑1‑49 on optical fibres is useful for:
- Optical fibre manufacturer
- Telecommunication sector
- Design engineer
- Quality control personnel
- Research and development facilities
Why should you use BS EN IEC 60793‑1‑49 - Optical fibres?
An optical fibre is a flexible, transparent fibre made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. BS EN IEC 60793‑1‑49 describes measurement methods and test procedures. With this method, the output from a probe fibre that is single-mode at the test wavelength excites the multimode fibre under test. The probe spot is scanned across the end-face of the fibre under test at specified radial positions, and a set of response pulses are acquired at these positions.
Three specifiable parameters can be derived from the collected set of data. The first parameter, differential modal delay (DMD), is the difference in optical pulse delay time between the fastest and slowest mode groups of the fibre under test. DMD specifications place limits on modal delay over a specified range of probe fibre radial offset positions.
The second specifiable parameter is derived by combining the pulses using sets of specific radial weights to determine an approximation of a set of pulses from typical transmitters. Using Fourier transforms, the calculated effective modal bandwidth (EMBc) is determined for each weight set.
The third specifiable parameter, the computed overfilled launch bandwidth, OMBc, is determined in a manner like EMBc, but by applying just one weight set to the set of pulses; this weight set corresponds to the overfilling condition, where all mode groups are equally excited.
The test's intent as described in BS EN IEC 60793‑1‑49 is to quantify the effects of interactions of the fibre modal structure and the source modal characteristics excluding the source's spectral interaction with fibre chromatic dispersion. Adding the effects of fibre chromatic dispersion and the source spectral characteristics will reduce the overall transmission bandwidth, but this is a separate calculation in most transmission models. Using BS EN IEC 60793‑1‑49 you understand the method for characterizing the modal structure of a graded-index multimode fibre.
What’s changed since the last update?
BS EN IEC 60793‑1‑49:2018 supersedes BS EN 60793‑1‑49:2006. BS EN IEC 60793‑1‑49:2018 includes some technical changes with respect to BS EN 60793‑1‑49:2006. These include:
- Better alignment with original intent by filling some omissions and therefore improving measurement rigor
- The measurement of fibres with smaller differential mode delay (and higher modal bandwidth) such as type a1a.3 fibres of IEC 60793-2-10 [1]1 that are used in constructing om4 performance category cables; new requirements on specifying detector amplitude and temporal response, specimen deployment conditions, four-quadrant scanning, and uniformity of radial locations for calculating the bandwidth