A Mach-Zehnder modulator with control device for operating point control, comprising: - a Mach-Zehnder modulator comprising: -- an optical splitter device configured to distribute an optical input signal in optical partial signals to at least two optical guide arms , -- at least one modulation device configured as an optical phase modulator for phase modulation of the optical input signal in at least one of the at least two optical guide arms , and -- an optical combining device , the optical combining device being configured to combine the optical partial signals of the at least two optical guide arms ; and - a control device comprising: -- a signal comparing device configured to compare the optical partial signals of the at least two optical guide arms , the signal comparing device being arranged between the optical splitter device and the at least one modulation device , -- at least one control modulation device arranged in at least one of the at least two optical guide arms , and -- a control circuit , the control circuit being configured to control an operating point of the Mach-Zehnder modulator at least by controlling the at least one control modulation device based on the comparison of the partial optical signals by the signal comparing device. - a Mach-Zehnder modulator comprising: -- an optical splitter device configured to distribute an optical input signal in optical partial signals to at least two optical guide arms , -- at least one modulation device configured as an optical phase modulator for phase modulation of the optical input signal in at least one of the at least two optical guide arms , and -- an optical combining device , the optical combining device being configured to combine the optical partial signals of the at least two optical guide arms ; and -- an optical splitter device configured to distribute an optical input signal in optical partial signals to at least two optical guide arms , -- at least one modulation device configured as an optical phase modulator for phase modulation of the optical input signal in at least one of the at least two optical guide arms , and -- an optical combining device , the optical combining device being configured to combine the optical partial signals of the at least two optical guide arms ; and - a control device comprising: -- a signal comparing device configured to compare the optical partial signals of the at least two optical guide arms , the signal comparing device being arranged between the optical splitter device and the at least one modulation device , -- at least one control modulation device arranged in at least one of the at least two optical guide arms , and -- a control circuit , the control circuit being configured to control an operating point of the Mach-Zehnder modulator at least by controlling the at least one control modulation device based on the comparison of the partial optical signals by the signal comparing device. -- a signal comparing device configured to compare the optical partial signals of the at least two optical guide arms , the signal comparing device being arranged between the optical splitter device and the at least one modulation device , -- at least one control modulation device arranged in at least one of the at least two optical guide arms , and -- a control circuit , the control circuit being configured to control an operating point of the Mach-Zehnder modulator at least by controlling the at least one control modulation device based on the comparison of the partial optical signals by the signal comparing device. <EOS>