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 (103, 104), -- at least one modulation device (101, 102) 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 (103, 104), 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 (103, 104); and - a control device comprising: -- a signal comparing device configured to compare the optical partial signals of the at least two optical guide arms (103, 104), the signal comparing device being arranged between the optical splitter device and the at least one modulation device (101, 102), -- at least one control modulation device (117, 117a) arranged in at least one of the at least two optical guide arms (103, 104), 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 (117, 117a) 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 (103, 104), -- at least one modulation device (101, 102) 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 (103, 104), 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 (103, 104); and -- an optical splitter device configured to distribute an optical input signal in optical partial signals to at least two optical guide arms (103, 104), -- at least one modulation device (101, 102) 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 (103, 104), 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 (103, 104); and - a control device comprising: -- a signal comparing device configured to compare the optical partial signals of the at least two optical guide arms (103, 104), the signal comparing device being arranged between the optical splitter device and the at least one modulation device (101, 102), -- at least one control modulation device (117, 117a) arranged in at least one of the at least two optical guide arms (103, 104), 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 (117, 117a) 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 (103, 104), the signal comparing device being arranged between the optical splitter device and the at least one modulation device (101, 102), -- at least one control modulation device (117, 117a) arranged in at least one of the at least two optical guide arms (103, 104), 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 (117, 117a) based on the comparison of the partial optical signals by the signal comparing device.