Coherent transmitter, method for controlling coherent transmitter, and coherent transceiver system

A method for controlling a coherent transmitter, wherein the method comprises:

• splitting, using a first beam splitter, a first optical signal to obtain a second optical signal and a third optical signal;
• modulating, using a first modulator, the second optical signal to obtain a first modulated signal;
• modulating, using a second modulator, the third optical signal to obtain a second modulated signal, wherein the first modulated signal and the second modulated signal have a same phase;
• adjusting, using a phase shift adjuster, a first phase of a first sub-signal in the first modulated signal;
• adjusting, using the phase shift adjuster, a second phase of a fourth sub-signal in the first sub-signal, wherein there is a first phase difference between the first sub-signal and the first modulated signal and a second phase difference between the fourth sub-signal and the first modulated signal, and wherein the second phase difference is twice as large as the first phase difference;
• combining, using a first beam combiner, a second sub-signal in the first modulated signal and the fourth sub-signal to obtain a first combined signal;
• combining, using a second beam combiner, a third sub-signal in the first sub-signal and the second modulated signal to obtain a second combined signal;
• performing, using a first photodiode (PD), optical-to-electrical conversion on the first combined signal to obtain a first electrical signal;
• and
• controlling, using a controller and based on the first electrical signal, a first voltage applied to the phase shift adjuster, to cause the first phase difference between the first sub-signal and the first modulated signal to fall within a preset range.

A coherent transceiver system, comprising:

• a light source configured to output an optical signal;
• a coherent transmitter coupled to the light source and configured to output a modulated signal, wherein the coherent transmitter comprises:
• a first signal modulator, wherein the first signal modulator comprises:
• a first beam splitter, wherein the first beam splitter is configured to split a first optical signal to obtain a second optical signal and a third optical signal;
• a first modulator coupled to the first beam splitter, wherein the first modulator is configured to modulate the second optical signal to obtain a first modulated signal;
• a second modulator coupled to the first beam splitter, wherein the second modulator is configured to modulate the third optical signal to obtain a second modulated signal, and wherein the first modulated signal and the second modulated signal have a same phase;
• a first phase shift adjuster coupled to the first modulator, wherein the first phase shift adjuster is configured to:
• adjust a first phase of a first sub-signal in the first modulated signal, wherein there is a first phase difference between the first sub-signal and the first modulated signal;
• and
• adjust a second phase of a fourth sub-signal in the first sub-signal, wherein there is a second phase difference between the fourth sub-signal and the first modulated signal, and wherein the second phase difference is twice as large as the first phase difference;
• a first beam combiner coupled to the first phase shift adjuster, wherein the first beam combiner is configured to combine a second sub-signal in the first modulated signal and the fourth sub-signal to obtain a first combined signal;
• and
• a second beam combiner coupled to the second modulator and the first phase shift adjuster, wherein the second beam combiner is configured to combine a third sub-signal in the first sub-signal and the second modulated signal to obtain a second combined signal, and wherein the modulated signal is the second combined signal;
• a first photodiode (PD) coupled to the first signal modulator, wherein the first PD is configured to perform optical-to-electrical conversion on the first combined signal to obtain a first electrical signal;
• and
• a controller coupled to the first signal modulator and the first PD, wherein the controller is configured to control, based on the first electrical signal, a first voltage applied to the first phase shift adjuster, to cause the first phase difference to fall within a preset range;
• and
• a coherent receiver coupled to the coherent transmitter, wherein the coherent receiver is configured to:
• mix the optical signal and the modulated signal to obtain a first mixed signal;
• and
• demodulate the first mixed signal.