Electro-optic modulator for modulating optical radiation comprising at least one upstream modulation subunit, at least one downstream modulation subunit and at least one phase-matching unit, wherein the upstream and downstream modulation subunits (MOD1, MOD2) are optically connected in series such that the optical radiation passes the downstream modulation subunit after passing the upstream modulation subunit, wherein the upstream modulation subunit comprises an upstream electrode, wherein a proximal end of the upstream electrode is adapted for receiving an electrical upstream modulation signal and located in an optical upstream section where the radiation enters the upstream modulation subunit, and wherein a distal end of the upstream electrode is located in an optical downstream section where the radiation leaves the upstream modulation subunit, wherein the downstream modulation subunit comprises a downstream electrode, wherein a proximal end of the downstream electrode is adapted for receiving an electrical downstream modulation signal and located in an optical upstream section where the radiation enters the downstream modulation subunit, and wherein a distal end of the downstream electrode is located in an optical downstream section where the radiation leaves the downstream modulation subunit, wherein the phase-matching unit is configured to delay the downstream modulation signal such that a phase difference between the upstream modulation signal at the distal end of the upstream electrode and the downstream modulation signal at the proximal end of the downstream electrode is minimal, characterized in that the phase-matching unit comprises a tunable delay line configured to delay the downstream modulation signal in response to a control signal, and a phase detector of the phase-matching unit is connected to the distal end of the upstream electrode and the proximal end of the downstream electrode, and configured to generate the control signal which indicates the phase difference between the distal end and the proximal end. at least one upstream modulation subunit, at least one downstream modulation subunit and at least one phase-matching unit, wherein the upstream and downstream modulation subunits (MOD1, MOD2) are optically connected in series such that the optical radiation passes the downstream modulation subunit after passing the upstream modulation subunit, wherein the upstream modulation subunit comprises an upstream electrode, wherein a proximal end of the upstream electrode is adapted for receiving an electrical upstream modulation signal and located in an optical upstream section where the radiation enters the upstream modulation subunit, and wherein a distal end of the upstream electrode is located in an optical downstream section where the radiation leaves the upstream modulation subunit, wherein the downstream modulation subunit comprises a downstream electrode, wherein a proximal end of the downstream electrode is adapted for receiving an electrical downstream modulation signal and located in an optical upstream section where the radiation enters the downstream modulation subunit, and wherein a distal end of the downstream electrode is located in an optical downstream section where the radiation leaves the downstream modulation subunit, wherein the phase-matching unit is configured to delay the downstream modulation signal such that a phase difference between the upstream modulation signal at the distal end of the upstream electrode and the downstream modulation signal at the proximal end of the downstream electrode is minimal, the phase-matching unit comprises a tunable delay line configured to delay the downstream modulation signal in response to a control signal, and a phase detector of the phase-matching unit is connected to the distal end of the upstream electrode and the proximal end of the downstream electrode, and configured to generate the control signal which indicates the phase difference between the distal end and the proximal end.