Time transfer for clock synchronisation over optical fibre is investigated as an alternative to GPS satellite transfer. With time synchronisation over optical fibre, the time it takes for the time signal to get from the sender to the receiver varies. Experiments have been done to see how much, where a modulated laser light signal, with a frequency of 15 MHz and a wavelength of 1550 nm, has been sent through optical fibres with a total length of 378 km. The temperature dependence of the signal delay was measured to 28 ps/°C/km. Measurements were also done for the equipment used for sending and receiving the signal, for which the variations in time were measured to be 17 ps/°C. A mixer was used to measure the variations in time for the signal to pass through the optical fibres. Measurements were done to establish the relation between the output and the phase difference between the two input signals. From the resulting curve a curve fitting was done to calculate the variations in time which gave a maximum error of 0.5 % compared to the measured data.