Single mode guided optics have recently taken a predominant place in communications systems. For instance single mode fibres enable long span, high data rate transmission links to be installed. In such fibers the data rate is ultimately limited by the chromatic dispersion, that is, the spectral variations of the propagation time. It will first be shown that chromatic dispersion is the fundamental limit to the data rate. Then, the dispersive properties of optical fibres will be described. The chromatic dispersion is experimentally deduced by differentiating the propagation delay measurements with respect to the wavelength. The experimental challenge is to measure the propagation delay with a 1 ps resolution per kilometre of fibre continuously over the full 1200 to 1600 nm spectral range. It has never been achieved so far. For this purpose two complementary experimental methods are proposed. On one hand, an interferometric method has been developed enabling meter-length fibre samples to be measured. Fibre birefringence can also be estimated by this technique without using any polarizing devices. On the other hand, a novel phase shift method using a double optical modulation has been achieved enabling long installed fibres to be measured.