This thesis discusses the possibility of a seamless switch between optical ground stations (OGSs) in ground-to-GEO communication. First an overview is given of the characteristics of a future optical DVB-S2 feederlink. The equipment at an OGS, the equipment on board of a satellite and the terrestrial network is described along with the effects of the atmosphere on the optical signal. The objective is to synchronise the signals from two different OGSs towards the satellite. Two existing solutions are presented which do not achieve the required performance. Nevertheless the principle of an existing Ka-band site diversity is promising and is adapted to be used in the proposed solution which uses a fixed delay line combined with a variable photonic delay line (VPDL). The solution is based on the principle of equalising the travelling paths via the two OGSs. To determine the required length of the VPDL a downlink sequence is sent from the satellite to both OGSs and then to a control centre, following the same path as the uplink. The time-delay difference measurement is done on the downlink sequence and used to add a time delay to one of the links. The performance of several VPDLs are discussed. At the moment of writing this thesis, no existing continuous tunable VPDL meets the requirements of the system. Therefore a system of concatenated switches and delay lines is proposed and tested in simulations. The satellite movement and the atmospheric turbulences are disturbances on the system that can not be controlled. Predictions of the satellite movement are available, but the turbulences are considered to be purely stochastic. A control strategy is proposed which uses the timing difference measurements on a downlink sequence to control the VPDL, thereby synchronising the OGSs. The measurements are thus done on a parallel feedback system which provides an estimation of the performance metric. A simulation model is built in Simulink containing the signal generation, a switching system, transmission channels for two OGSs and a DVB-S2 receiver. Included in the simulation model is the proposed time delay compensation system. The simulations show the feasibility of the proposed solution. The VPDL will need a precision of a quarter of a symbol time to be seamless. Further tests are necessary to show if the simulation model provides realistic performances.