Abstract: A controller may apply an electrical signal to each of two arms of a Mach-Zehnder Interferometer (MZI) and may dither the electrical signals applied to one, or both, of the arms between a nominal state, a high state and a low state such that there is a constant phase difference between the arms in the high and low states compared to the nominal state, wherein each electrical signal comprises a static component (IL, IR, IL?, IR?) and a dither component. The controller may change the static component of the respective electrical signal applied to one, or both, of the arms in accordance with changes to an operating point during variation of the dither component and may vary a dither magnitude in accordance with changes in the electrical signal applied to one, or both, of the arms so as to maintain the constant phase difference.

Abstract: A controller may apply an electrical signal to each of two arms of a Mach-Zehnder Interferometer (MZI) and may dither the electrical signals applied to one, or both, of the arms between a nominal state, a high state and a low state such that there is a constant phase difference between the arms in the high and low states compared to the nominal state, wherein each electrical signal comprises a static component (IL, IR, IL?, IR?) and a dither component. The controller may change the static component of the respective electrical signal applied to one, or both, of the arms in accordance with changes to an operating point during variation of the dither component and may vary a dither magnitude in accordance with changes in the electrical signal applied to one, or both, of the arms so as to maintain the constant phase difference.

Abstract: There is described an optical modulation system for transmitting modulated optical light. The system comprises an electro-optic modulator having at least two arms through which light is transmitted and an imbalance electrode located on at least one arm. A current source is configured to inject current into the imbalance electrode for modifying the phase of light passing through the arm. A dither generator is configured to modulate the injected current, or bias voltage applied to at least one of the arms, with a dither signal. A phase sensitive detector is configured to detect an error in the phase of light emitted by the modulator. An operating point controller is configured to monitor the detected phase error and adjust the current injected into the imbalance arm so as to compensate for the detected error and thereby control an operating point of the modulator.

Abstract: There is described an optical modulation system for transmitting modulated optical light. The system comprises an electro-optic modulator having at least two arms through which light is transmitted and an imbalance electrode located on at least one arm. A current source is configured to inject current into the imbalance electrode for modifying the phase of light passing through the arm. A dither generator is configured to modulate the injected current, or bias voltage applied to at least one of the arms, with a dither signal. A phase sensitive detector is configured to detect an error in the phase of light emitted by the modulator. An operating point controller is configured to monitor the detected phase error and adjust the current injected into the imbalance arm so as to compensate for the detected error and thereby control an operating point of the modulator.