APPARATUS AND METHOD FOR DETERMINING OPTICAL PHASE DIFFERENCE OF SUB SIGNAL OF OPTICAL TRANSMITTER

1 . An apparatus for determining an optical phase difference of a sub-signal of an optical transmitter, comprising:

a memory; and

a processor coupled to the memory to:

input a first input signal to a first electro-optical conversion unit, to enable the first electro-optical conversion unit to modulate to-be-modulated light according to the first input signal and to obtain a first output signal;

input a second input signal to a second electro-optical conversion unit, to enable the second electro-optical conversion unit to modulate to-be-modulated light according to the second input signal and to obtain a second output signal, wherein correlation of the second input signal and the first input signal is not 0;

perform a coherent detection operation based on the first output signal and the second output signal to obtain a first output quantity and a second output quantity; and

determine an optical phase difference of an output signal of the first electro-optical conversion unit and an output signal of the second electro-optical conversion unit according to the first output quantity and the second output quantity.

2 . The apparatus according to claim 1 , wherein the first electro-optical conversion unit is a transmitter, or a partial modulation unit of the transmitter.

3 . The apparatus according to claim 1 , wherein the second electro-optical conversion unit outputs a finite number of states.

4 . The apparatus according to claim 1 , wherein

the second input signal is same as the first input signal; or

the second input signal is a weighted sum of the first input signal at a plurality of different moments; or

the second input signal is a symbol sequence of a weighted sum of the first input signal at a plurality of different moments; or

the second input signal is a product of a symbol sequence of a weighted sum of the first input signal at a plurality of different moments and a random amplitude sequence.

5 . The apparatus according to claim 1 , wherein the first electro-optical conversion unit is connected in parallel to the second electro-optical conversion unit, and the first electro-optical conversion unit is connected to a first input end of a low-speed coherent detection unit, and inputs the first output signal to the first input end, and the second electro-optical conversion unit is connected to a second input end of the low-speed coherent detection unit, and inputs the second output signal to the second input end; and

the low-speed coherent detection unit is further configured to:

perform a coherent detection operation on the first output signal and the second output signal to obtain the first output quantity and the second output quantity.

6 . The apparatus according to claim 1 , wherein the first electro-optical conversion unit is connected in series to the second electro-optical conversion unit, and a series structure of the first electro-optical conversion unit and the second electro-optical conversion unit is connected to a first input end of a low-speed coherent detection unit, and inputs a product of the first output signal and the second output signal to the first input end, and a second input end of the low-speed coherent detection unit is input a pre-set reference signal, and

the low-speed coherent detection unit is further configured to:

perform a coherent detection operation on the product of the first output signal and the second output signal as well as the pre-set reference signal to obtain the first output quantity and the second output quantity.

7 . The apparatus according to claim 1 , wherein the processor configured to:

substitute the first output quantity and the second output quantity into a formula, to obtain the optical phase difference, as follows:

φ

=

arg

⁡

(

I

1

-

j

⁢

I

2

)

where, I 1 is the first output quantity, I 2 is the second output quantity, φ is an optical phase difference of the output signal of the first electro-optical conversion unit and the output signal of the second electro-optical conversion unit, and arg (z) is principal argument angle of a complex number z.

8 . The apparatus according to claim 1 , wherein the processor is further configured to:

multiply the second input signal with a low-frequency square wave before the second input signal is input to the second electro-optical conversion unit; and

multiply the first output quantity and the second output quantity with the low-frequency square wave respectively, before the optical phase difference is determined based on the first output quantity and the second output quantity; and

the processor is further configured to:

input a product signal of the second input signal and the low-frequency square wave to the second electro-optical conversion unit; and

determine the optical phase difference according to a product of the first output quantity and the low-frequency square wave and a product of the second output quantity and the low-frequency square wave.

9 . The apparatus according to claim 1 , wherein the processor is further configured to:

pre-set input, at a pre-set moment, the second input signal to the second electro-optical conversion unit; and

input, at a moment other than the pre-set moment, a signal with correlation of 0 with the first input signal, or a 0 signal to the second electro-optical conversion unit.

10 . A method for determining an optical phase difference of a sub-signal of an optical transmitter, the method comprising:

inputting a first input signal to a first electro-optical conversion unit, to enable the first electro-optical conversion unit to modulate to-be-modulated light according to the first input signal and to obtain a first output signal;

inputting a second input signal to a second electro-optical conversion unit, to enable the second electro-optical conversion unit to modulate to-be-modulated light according to the second input signal and to obtain a second output signal, wherein correlation of the second input signal and the first input signal is not 0;

performing a coherent detection operation based on the first output signal and the second output signal to obtain a first output quantity and a second output quantity; and

determining an optical phase difference of an output signal of the first electro-optical conversion unit and an output signal of the second electro-optical conversion unit according to the first output quantity and the second output quantity.