Optical signal modulator comprising a modulator unit having an optical ingress port for inputting optical radiation, a first and second optical output port (51, 52) each for outputting modulated optical radiation, and an electrical ingress port for inputting an electrical modulation signal, the modulator unit being configured to modulate the optical radiation in response to the electrical modulation signal (Em), a photodetector connected to the second optical output port and configured to measure the modulated optical radiation that is emitted at the second optical output port, and to provide a monitor signal, and an electrical signal combiner having a first input port for inputting an external electrical data signal, a second electrical input port for inputting a correction signal that is based on the monitor signal, and an electrical output port that is connected to the electrical ingress port of the modulator unit, wherein the combiner is configured to generate said electrical modulation signal (Em) by combining the external electrical data signal and the correction signal, characterized in that an amplifier is electrically arranged between the photodetector and the signal combiner and the amplifier is configured to amplify the monitor signal and thereby generate the correction signal, wherein the signal modulator is configured to generate an optical data signal of a given bit duration, and wherein the modulator unit, the photodetector, the amplifier and the combiner are integrated in a same semiconductor chip in such a close distance that the signal path extending from the output port of the combiner via the electrical ingress port of the modulator unit, the second output port of the modulator unit, the photodetector, and the amplifier to the second electrical input port of the combiner is so short that the signal travel time is smaller than 25 % of said given bit duration. a modulator unit having an optical ingress port for inputting optical radiation, a first and second optical output port (51, 52) each for outputting modulated optical radiation, and an electrical ingress port for inputting an electrical modulation signal, the modulator unit being configured to modulate the optical radiation in response to the electrical modulation signal (Em), a photodetector connected to the second optical output port and configured to measure the modulated optical radiation that is emitted at the second optical output port, and to provide a monitor signal, and an electrical signal combiner having a first input port for inputting an external electrical data signal, a second electrical input port for inputting a correction signal that is based on the monitor signal, and an electrical output port that is connected to the electrical ingress port of the modulator unit, wherein the combiner is configured to generate said electrical modulation signal (Em) by combining the external electrical data signal and the correction signal, an amplifier is electrically arranged between the photodetector and the signal combiner and the amplifier is configured to amplify the monitor signal and thereby generate the correction signal, wherein the signal modulator is configured to generate an optical data signal of a given bit duration, and wherein the modulator unit, the photodetector, the amplifier and the combiner are integrated in a same semiconductor chip in such a close distance that the signal path extending from the output port of the combiner via the electrical ingress port of the modulator unit, the second output port of the modulator unit, the photodetector, and the amplifier to the second electrical input port of the combiner is so short that the signal travel time is smaller than 25 % of said given bit duration.