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. Four methods are described 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; – class B single-mode fibres (all categories). Method D applies to the measurement of chromatic dispersion values of single-mode fibres categories B1 to B3 in 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 temperatures as stated in IEC 60793-1-1. 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 forshorter piece fibres (1 m to 10 m). Information common to all three methods is contained in clauses 1 to 8, and information pertaining to each individual method appears in annexes A, B, C and D, respectively.
