A system for synchronizing an oscillating reference signal, Sref, and an oscillating remote signal, Srem, the system comprising a sender with a reference oscillator generating the reference signal (Sref) and a receiver with a remote signal source providing the remote signal (Srem), wherein the sender and the receiver are arranged remote from each other and are linked by an optical fiber, wherein the sender further comprises: - a laser for emission of a laser beam, including an optical coupler for coupling the laser beam into the optical fiber, - an optical amplitude modulator being arranged downstream the laser and being coupled to the reference oscillator for amplitude modulating the laser beam with the reference signal, Sref, and the receiver further comprises: - an optical reflector arranged downstream a remote end of the optical fiber emitting the transmitted modulated laser beam, wherein the reflector is configured to partially reflect the transmitted modulated laser beam back through the optical fiber towards the sender, characterized in that - the sender comprises a phase detector configured to detect a phase difference between the reference signal, Sref, and a signal in a back-reflected laser beam, which is the transmitted modulated laser beam being reflected back through the optical fiber from the receiver to the sender, - the sender and the receiver are coupled via a data link and a value of the detected phase difference is communicated via the data link from the sender to the receiver, - the receiver comprises a further phase detector configured to detect a further phase difference between the remote signal, Srem, and the reference signal, Sref, in the transmitted modulated laser beam, - the receiver is configured to correct the detected value of said further phase difference by the value of the phase difference detected by the phase detector in the sender, said value being received via the data link, for synchronizing the reference signal, Sref, and the remote signal, Srem. - a laser for emission of a laser beam, including an optical coupler for coupling the laser beam into the optical fiber, - an optical amplitude modulator being arranged downstream the laser and being coupled to the reference oscillator for amplitude modulating the laser beam with the reference signal, Sref, and the receiver further comprises: - an optical reflector arranged downstream a remote end of the optical fiber emitting the transmitted modulated laser beam, wherein the reflector is configured to partially reflect the transmitted modulated laser beam back through the optical fiber towards the sender, - the sender comprises a phase detector configured to detect a phase difference between the reference signal, Sref, and a signal in a back-reflected laser beam, which is the transmitted modulated laser beam being reflected back through the optical fiber from the receiver to the sender, - the sender and the receiver are coupled via a data link and a value of the detected phase difference is communicated via the data link from the sender to the receiver, - the receiver comprises a further phase detector configured to detect a further phase difference between the remote signal, Srem, and the reference signal, Sref, in the transmitted modulated laser beam, - the receiver is configured to correct the detected value of said further phase difference by the value of the phase difference detected by the phase detector in the sender, said value being received via the data link, for synchronizing the reference signal, Sref, and the remote signal, Srem.