This part of IEC 60793 establishes uniform requirements for measuring the chromatic
dispersion of optical fibre, thereby assisting in the inspection of fibres and cables for
commercial purposes.
Chromatic dispersion varies with wavelength. Some methods and implementations measure
the group delay as a function of wavelength and the chromatic dispersion and dispersion
slope are deduced from the derivatives (with respect to wavelength) of this data. This
differentiation is most often done after the data are fitted to a mathematical model. Other
implementations can allow direct measurement (of the chromatic dispersion) at each of the
required wavelengths.
For some categories of fibre, the chromatic dispersion attributes are specified with the
parameters of a specific model. In these cases, the relevant recommendation or standard
defines the model appropriate for the definition of the specified parameters. For other fibre
categories, the dispersion is specified to be within a given range for one or more specified
wavelength intervals. In the latter case, either direct measurements may be made at the
wavelength extremes or some fitting model may be used to allow either group delay
measurement methods or implementations or storage of a reduced set of parameters that may
be used to calculate the interpolated dispersion for particular wavelengths which may not
have actual direct measurement values.
Annex E gives a general description of chromatic dispersion fitting and outlines a number of
fitting equations suitable for use with any of the measurement methods or fibre categories.
This standard gives four methods for measuring chromatic dispersion:
– method A: phase shift;
– method B: spectral group delay in the time domain;
– method C: differential phase shift;
– method D: interferometry.
Methods A, B, and C apply to the measurement of chromatic dispersion of the following fibres
over a specified wavelength range:
– class A1 graded-index multimode fibres;
– category A4f, A4g and A4h multimode fibres;
– class B single-mode fibres (all categories).
Method D applies to the measurement of chromatic dispersion values of single-mode fibres
categories B1, B2, B4 and B5 over the 1 000 nm to 1 700 nm wavelength range.
The methods can be applied to laboratory, factory and field measurements of chromatic
dispersion, and the wavelength range of the measurements can be tailored as required.
Measurements are made at temperature as stated in IEC 60793-1-1, Table 1 – Standard
range of atmospheric conditions (Temperature 23 °C ±5 °C).
The methods are suitable for fibre or cable lengths greater than 1 km. They may also be
applied to shorter lengths, but accuracy and repeatability may be compromised. Method D is
the preferred method for shorter piece fibres (1 m to 10 m).
Information common to all methods is contained in Clauses 1-8, and information pertaining to
each individual method appears in Annexes A, B, C, and D, respectively.
BS EN 60793-1-42:2007 history
2013BS EN 60793-1-42:2013 Optical fibres. Measurement methods and test procedures. Chromatic dispersion
2007BS EN 60793-1-42:2007 Optical fibres - Measurement methods and test procedures - Chromatic dispersion
2002BS EN 60793-1-42:2002 Optical fibres - Measurement methods and test procedures - Chromatic dispersion