Four methods are described for measuring chromatic dispersion: (a) phase shift, (b) spectral group delay in the time domain, (c) differential phase shift, and (d) interferometry. Methods (a), (b) and (c) apply to class A1 graded-index multimode fibres and class B single-mode fibres. Method (d) applies to single-mode fibres, class B1 to B3 in the 1000 nm to 1700 nm wavelength range. The methods can be applied to laboratory, factory and field measurements of chromatic dispersion. The main changes in this second edition concern the addition of a new Annex E on chromatic dispersion fitting and the applicability to A4 fibres.