WO2021017382A1

WO2021017382A1 - Method and system for controlling iq signal phase error

Info

Publication number: WO2021017382A1
Application number: PCT/CN2019/126870
Authority: WO
Inventors: 朱石超; 曹权
Original assignee: 烽火通信科技股份有限公司; 武汉飞思灵微电子技术有限公司; 武汉光谷信息光电子创新中心有限公司
Priority date: 2019-07-29
Filing date: 2019-12-20
Publication date: 2021-02-04
Also published as: CN110190907B; CN110190907A

Abstract

The present invention relates to the technical field of coherent optical modules. Disclosed are a method and a system for controlling IQ signal phase error, the method comprising the following steps: controlling the IQ signal phase error by adjusting the intensity coefficients of channels corresponding to I signal and Q signal, respectively. The present invention can reduce or even eliminate the quadrature angle phase error of IQ signals to improve the performance of the coherent optical communication system without providing a phase shifter or changing the original coherent optical communication system architecture.

Description

A method and system for controlling phase error of IQ signal

Technical field

The invention relates to the technical field of coherent optical modules, in particular to a method and system for controlling the phase error of an IQ signal.

Background technique

In a coherent optical communication system, in order to use the phase information of light, the signal is modulated and demodulated by I and Q, which can greatly increase the capacity and distance of the coherent optical communication system. The coherent receiver uses key components such as optical mixers to demodulate and obtain orthogonal I and Q signals.

However, in the actual demodulation process, due to certain process errors in the device, the demodulated I and Q signals are not perfectly orthogonal, and there is a quadrature angle phase error (referred to as phase error), which reduces demodulation performance and degrades system performance. , Such as optical signal-to-noise ratio (OSNR). In addition, the communication rate and coding complexity are still being further improved, and higher requirements are placed on the phase error of the on-chip integrated coherent receiver, and even the phase error has gradually become a key parameter restricting system performance.

In addition to process dependency, phase error also has temperature dependency and wavelength dependency. In addition, the phase error of different materials is different. Compared with materials such as PLC and InP, the refractive index difference of SOI chip is larger, and the phase error is usually larger. It is more difficult to reduce the phase error of silicon-based optoelectronic chips.

There are currently three methods for reducing IQ phase errors in coherent receivers: The first is to optimize the passive mixer structure. Currently reported passive mixers, such as those based on 2x4MMI, after design optimization, theoretically, the phase error can be less than 5 degrees within the operating wavelength range, and ideally even less than 3 degrees. However, this method is very sensitive to the process, and there are large process errors between chips and wafers. Therefore, in practice, the product phase error usually fluctuates in a large range, even far greater than the design value, resulting in a very low product yield.

The second method requires an active mixer structure to directly adjust the internal phase of the mixer through feedback. For example, a mixer with a 3dB coupler + phase shifter structure can reduce the IQ phase error by adjusting the internal phase of the mixer through the phase shifter. However, the phase shifter introduced by this method will bring additional costs. For example, the use of a PN junction phase shifter will cause unbalanced output and increase insertion loss. The use of a hot electrode type phase shifter will introduce thermal crosstalk, which is easily disturbed by temperature changes. At the same time, the phase shifter will additionally increase power consumption and bring reliability problems.

The third method is to use DSP orthogonalization algorithm to compensate. This method processes the data stream on the DSP side, and converts the original non-orthogonalized IQ data into orthogonal normalized IQ data. However, in practical applications, due to the existence of influence factors such as noise and dispersion, the compensation range of the algorithm is restricted. At the same time, the algorithm introduces a larger computational load, increases DSP power consumption, and greatly reduces applicable scenarios. For example, the DSP used in the data center may not support this algorithm. In addition, after the algorithm is compensated, the performance degradation of the coherent optical communication system caused by the phase error cannot be eliminated.

Summary of the invention

In view of the defects in the prior art, the purpose of the present invention is to provide an IQ signal phase error control method, which does not require a phase shifter, and can reduce or even eliminate IQ without changing the original coherent optical communication system architecture. The quadrature angle phase error of the signal improves the performance of the coherent optical communication system.

In order to achieve the above objectives, the technical solution adopted by the present invention is:

An IQ signal phase error control method, the method includes the following steps:

By adjusting the intensity coefficients of the channels corresponding to the I signal and the Q signal, the control of the phase error of the IQ signal is realized.

On the basis of the above technical solution, the control of the phase error of the IQ signal is realized by adjusting the intensity coefficients of the channels corresponding to the I signal and the Q signal, which specifically includes:

Collect and obtain the electric signal value vector of I signal and Q signal;

Calculate the function value of the target parameter. The target parameter is a function of the electrical signal value vector of the I signal and the Q signal as the independent variable, and the target parameter is configured as: when the function value of the target parameter approaches the maximum value, the IQ signal The phase error approaches the minimum;

Adjust the intensity coefficients of the channels corresponding to the I signal and the Q signal to make the function value of the target parameter approach the most value.

On the basis of the above technical solution, the expression of the target parameter is:

y=|E{I*Q}|/(E{|I|}*E{|Q|}), where:

E{|I|}=(|I ₁ |+|I ₂ |+|I ₃ |+...+|I _N-1 |+|I _N |)/N;

E{|Q|}=(|Q ₁ |+|Q ₂ |+|Q ₃ |+...+|Q _N-1 |+|Q _N |)/N;

E{I*Q}=(I ₁ *Q ₁ +I ₂ *Q ₂ +I ₃ *Q ₃ +...+I _N-1 *Q _N-1 +I _N *Q _N )/N;

I and Q are the electric signal value vectors of I signal and Q signal respectively, I _N is the Nth electric signal value of I signal in N acquisitions, and Q _N is the Nth signal of Q signal in N acquisitions Electric signal value, N is a positive integer.

On the basis of the above technical solution, the expression of the target parameter may also be:

y=(E{|I|}*E{|Q|})/|E{I*Q}|, where:

E{|I|}=(|I ₁ |+|I ₂ |+|I ₃ |+...+|I _N-1 |+|I _N |)/N;

E{|Q|}=(|Q ₁ |+|Q ₂ |+|Q ₃ |+...+|Q _N-1 |+|Q _N |)/N;

On the basis of the above technical solution, the intensity coefficients of the channels corresponding to the I signal and the Q signal are adjusted to make the function value of the target parameter approach the maximum value, thereby making the phase error of the IQ signal approach the minimum value, including:

S31. Preset the initial intensity coefficient of each channel, and calculate the initial value y _{0 of the} target parameter according to the initial value of the electrical signal value vector of the I signal and the Q signal;

S32. Divide the 4 channels into two groups to correspond to the I signal and the Q signal, and the phase difference of the two channels in each group is a preset degree, based on the boundary conditions of the intensity coefficient of the channel, alternate according to the preset The rule adjusts the intensity coefficients of the two groups of channels. When adjusting one of the channels, the first adjusted channel is used as the reference channel, and the adjustment direction of the reference channel is recorded. When the reference channel is adjusted once, the next The intensity coefficient of the adjusted channel is continuously adjusted, and E{|I|} and E{|Q|} are calculated in real time until it meets |E{|I|}-E{|Q|}|≤A, where A is the default Threshold

S33. Calculate the correction value of the target parameter by using the electrical signal values of the N times I signal and N times Q signal collected when |E{|I|}-E{|Q|}|≤A If the value is greater than the initial value y ₀ , step S34 is executed, and if the correction value is less than the initial value y ₀ , step S35 is executed;

S34. Return to step S32, and change the adjustment direction of the intensity coefficient of the reference channel;

S35. Return to step S32, and keep the adjustment direction of the intensity coefficient of the reference channel unchanged;

S36. Repeat steps S32 to S35 to make the correction value of the target parameter approach the maximum value.

On the basis of the above technical solution, the electrical signal value vectors of the I signal and the Q signal are collected and obtained, which specifically includes:

Use the voltage values of the I signal or the Q signal collected in each period of the N cycles as the vector element to establish the voltage value vector of the I signal and the Q signal;

Or, the current value of the I signal or the Q signal collected in each of the N cycles is used as the vector element to establish the current value vector of the I signal and the Q signal.

On the basis of the above technical solution, the voltage value of the I signal or the Q signal collected in each of the N cycles is used as the vector element to establish the voltage value vector of the I signal and the Q signal, which specifically includes:

Collect the voltage value of I signal once in each period of N cycles, the voltage value of I signal meets: V _I =R ₁ cos(ωt)-R ₂ cos(ωt+Δθ _2-1 )=R _I cos (ωt+Δθ _I );

Collect the voltage value of the Q signal in each period of N cycles, and the voltage value of the Q signal satisfies V _Q = R ₃ cos(ωt+Δθ _3-1 )-R ₄ cos(ω _t +Δθ _4-1 )=R _Q cos(ω _t +Δθ _Q );

_{Wherein, R i (i = 1 ~} 4) represents an intensity coefficient of the i-th channels, ω is the signal light and the local light optical frequency _{difference, Δθ j-1 (j =} 2,3,4) represents the j-th passage The phase difference between the channel and the first channel, R _I and R _Q are the intensity coefficients of _I and _Q respectively, and Δθ _Q -Δθ _I -π/2 represents the phase error;

Take the collected voltage values of the N channels I signals as the values of the N elements of the voltage value vector of the I channels;

The voltage values of the N signals of the Q channels are collected as the values of the N elements of the voltage value vector of the Q signals.

On the basis of the above technical solution, the intensity coefficient of the channel is adjusted by adjusting the optical power of the output optical path of the optical mixer, the responsivity of the photodiode PD, and/or the gain coefficient of the transimpedance amplifier TIA.

Another object of the present invention is to provide an IQ signal phase error control system, which does not require a phase shifter and can reduce or even eliminate the quadrature angle phase error of the IQ signal without changing the original coherent optical communication system architecture. Improve the performance of coherent optical communication systems.

An IQ signal phase error control system, including:

The control unit is used to control the phase error of the IQ signal by adjusting the intensity coefficients of the channels corresponding to the I signal and the Q signal.

On the basis of the above technical solution, the control unit includes:

An acquisition module, which is used to acquire the electrical signal value vectors of the I signal and the Q signal;

The calculation module is used to calculate the function value of the target parameter. The target parameter is a function of the electrical signal value vector of the I signal and the Q signal as an independent variable, and the target parameter is configured as: When the function value approaches the maximum value, the phase error of the IQ signal approaches the minimum value; and

The adjustment module is used to adjust the intensity coefficients of the channels corresponding to the I-channel signal and the Q-channel signal, so that the function value of the target parameter approaches the maximum value, and then the phase error of the IQ signal approaches the minimum value.

On the basis of the above technical solution, the adjustment module adjusts the intensity coefficient of the channel by adjusting the optical power of the optical mixer output optical path, the photodiode PD responsivity and/or the transimpedance amplifier TIA gain coefficient.

Compared with the prior art, the advantages of the present invention are:

The present invention collects the current or voltage values of the I signal and the Q signal, and defines target parameters to characterize the phase error. Separately adjust the intensity coefficients of the 4 channels to make the target parameter reach the minimum or maximum value, and then the corresponding phase error to the minimum value, so as to realize the compensation of the system phase error. Moreover, the method adopted in the present invention does not change the original hardware composition of the system, does not require a phase shifter, has low power consumption and low cost, and can meet the requirements of the ultra-100G coherent optical communication system for phase error.

Description of the drawings

FIG. 1 is a flowchart of an IQ signal phase error control method in an embodiment of the present invention;

FIG. 2 is a flowchart of step S3 in FIG. 1;

Fig. 3 is a schematic diagram of adjustment results in an embodiment of the present invention;

Figure 4 is a schematic diagram of an IQ signal phase error control system in an embodiment of the present invention;

Fig. 5 is a schematic diagram of a control unit in an embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the drawings and embodiments.

The embodiment of the present invention provides an IQ signal phase error control method. The method includes the following steps:

In this embodiment, the electrical signal values of the I signal and the Q signal are changed by adjusting the intensity coefficients of the channels corresponding to the I signal and the Q signal, which can affect the phase error of the IQ signal to achieve control The purpose of IQ signal phase error.

Specifically, referring to Figure 1, the control of the phase error of the IQ signal is achieved by adjusting the intensity coefficients of the channels corresponding to the I signal and the Q signal, which specifically includes:

S1. Collect and obtain the electric signal value vector of the I signal and the Q signal;

The electric signal value vector for the I-channel signal and the Q-channel signal is established using the electric signal values of the I-channel signal or the Q-channel signal collected in each period of N cycles as the vector elements. The value of N should be moderate, and the accuracy and calculation amount need to be considered comprehensively. In this embodiment, it may be 10 ³ , 10 ⁴ or 10 ^5. Preferably, the value of N is 10 ⁵ .

In this embodiment, one complete collection will collect 2N data in N cycles, and the next complete collection will collect 2N data in another N cycles. The collected electrical signal refers to the voltage or current that changes over time.

As a better implementation manner, in this embodiment, the electrical signal values of the I-channel signal and the Q-channel signal are collected once at the respective decision points of each of the N cycles. The decision point is for the eye diagram. The eye diagram is the result of accumulating and superimposing the bits of the collected serial signal with the afterglow method. When the signal-to-noise ratio reaches the optimal value, the eye diagram opening reaches the maximum. It is the best time for sampling, also called the decision point.

In this embodiment, you can select whether to collect voltage or current according to needs:

When collecting voltage, the voltage value vector of the I signal and the Q signal is established. The value of the N elements in the voltage value vector of the I signal or the Q signal is: the I collected on each of the N cycles The voltage value of channel signal or Q channel signal.

When collecting current, the current value vector of the I signal and the Q signal is established. The value of the N elements in the current value vector of the I signal or the Q signal is: the I collected on each of the N cycles Current value of channel signal or Q channel signal.

The following takes voltage as an example for specific introduction:

The optical mixer in this embodiment is a 90-degree optical mixer, and its output is 4 channels. This determines the number of channels is also 4, and also determines the phase difference between the channels.

Collect the voltage value of I signal once in each period of N cycles, and the voltage value of I signal meets: V _I =R ₁ cos(ωt)-R ₂ cos(ωt+Δθ _2-1 )=R _I cos (ωt+Δθ _I );

Collect the voltage value of the Q signal in each period of N cycles, and the voltage value of the Q signal meets V _Q = R ₃ cos(ωt+Δθ _3-1 )-R ₄ cos(ωt+Δθ _4-1 ) =R _Q cos(ωt+Δθ _Q );

_{Wherein, R i (i = 1 ~} 4) represents an intensity coefficient of the i-th channels, ω is the signal light and the local light optical frequency _{difference, Δθ j-1 (j =} 2,3,4) represents the j-th passage The phase difference between the channel and the first channel, R _I and R _Q are the intensity coefficients of _I and _Q respectively, Δθ _Q -Δθ _I -π/2 represents the phase error; and R _I , R _Q , Δθ _I and Δθ _Q satisfy :

Similarly, if you need to collect current, it is similar to voltage, but the difference lies in the addition of resistance or impedance.

In the above description, the intensity coefficient of the channel mainly reflects the intensity information, or the magnitude of the amplitude.

On the physical level, the i-th channel actually includes but is not limited to the i-th output optical path of the optical mixer, the i-th photodiode PD, and the i-th transimpedance amplifier TIA.

Therefore, the intensity coefficient of the channel is at least related to the following factors: the optical power Pi of the _i- th channel, the responsivity RE _i of the i-th PD, and the gain coefficient A _{i of the i-th} TIA. The intensity coefficient of the i-th path can approximately satisfy the following relationship: R _i =P _i ×RE _i ×A _i .

Thus, the intensity coefficient of the channel can be adjusted by adjusting the optical power of the output optical path of the optical mixer, the responsivity of the photodiode PD, and/or the gain coefficient of the transimpedance amplifier TIA.

The intensity coefficients of I and Q mainly refer to the amplitude of the electrical signal of the I signal and the Q signal. If the voltage is collected, it is the amplitude of the voltage, and if the current is collected, it is the amplitude of the current.

S2. Calculate the function value of the target parameter. The target parameter is a function with the electrical signal value vectors of the I signal and the Q signal as the independent variable, and the target parameter is configured as: when the function value of the target parameter approaches the maximum value, The phase error of IQ signal approaches the minimum;

The target parameters here can be set reasonably according to actual needs, and the conditions that need to be met are: when the target parameter approaches the maximum value, the phase error of the IQ signal approaches the minimum value. That is to say, it only needs to be satisfied: when the target parameter approaches the maximum or minimum, the phase error of the IQ signal can approach the minimum.

The expression of the target parameter in this embodiment is:

y=|E{I*Q}|/(E{|I|}*E{|Q|}), where:

E{|I|}=(|I ₁ |+|I ₂ |+|I ₃ |+...+|I _N-1 |+|I _N |)/N;

E{|Q|}=(|Q ₁ |+|Q ₂ |+|Q ₃ |+...+|Q _N-1 |+|Q _N |)/N;

When the expression of the target parameter in this embodiment is adopted, the condition that it satisfies is: when the target parameter approaches the minimum value, the phase error of the IQ signal approaches the minimum value.

Another target parameter is given below. When the target parameter approaches the maximum value, the phase error of the IQ signal approaches the minimum value.

That is, the expression of the target parameter is:

y=(E{|I|}*E{|Q|})/|E{I*Q}|, where:

E{|I|}=(|I ₁ |+|I ₂ |+|I ₃ |+...+|I _N-1 |+|I _N |)/N;

E{|Q|}=(|Q ₁ |+|Q ₂ |+|Q ₃ |+...+|Q _N-1 |+|Q _N |)/N;

S3. Adjust the intensity coefficients of the channels corresponding to the I-channel signal and the Q-channel signal, so that the function value of the target parameter approaches the maximum value, and then the phase error of the IQ signal approaches the minimum value.

As shown in Fig. 2, step S3 specifically includes the following steps:

The optical mixer in this embodiment is a 90-degree optical mixer, and its output is 4 channels. This determines the number of channels is also 4, and also determines the phase difference between the channels. Therefore, it is necessary to set the initial intensity coefficients for the 4 channels respectively. Then, the electrical signal values of the I signal and the Q signal collected in a certain N period are used as the initial value for calculation to obtain the initial value y _{0 of the} target parameter.

Divide the 4 channels into two groups to correspond to the I signal and the Q signal. The condition to be met for grouping is that the phase difference of the two channels in each group is a preset degree, usually the ideal value of this preset degree It is 180 degrees.

In this embodiment, a variable optical attenuator (VOA) or a semiconductor optical amplifier (SOA) may be used to adjust the output optical power of the optical mixer, or the TIA gain coefficient may be used to adjust the intensity coefficient of the channel. The boundary condition of the intensity coefficient of the channel refers to the adjustment range of the intensity coefficient of the channel, for example, it is set in the range of [x ₁ , x ₂ ] for adjustment. The preset alternation rule refers to: adjusting one set of channels P times first, and then adjusting another set of channels Q times as a cycle, repeating the adjustment of the two sets of channels. For example, if P and Q are both 1, then the two sets of channels alternate in sequence. If P and Q are both 10, first adjust one set of channels 10 times, then adjust the other set of channels 10 times, and follow Loop this way.

Setting the condition |E{|I|}-E{|Q|}|≤A is to judge whether E{|I|} is equal to E{|Q|}. Generally speaking, when the difference between the two is satisfied in the preset Within the threshold range of, the two can be considered equal. When the two are equal, the signal quality can be well guaranteed.

For the adjustment direction of the reference channel, the adjustment direction refers to the increase or decrease of the intensity coefficient of the reference channel, and the change of the adjustment direction means that if you choose to increase the intensity coefficient of the reference channel at the beginning, it will be decreased during the next adjustment. The intensity coefficient of the reference channel.

In the actual adjustment, the adjustment amount, that is, the adjustment step δR, increases or decreases by one adjustment step δR each time it is adjusted. δR can be a fixed value, or an adaptive algorithm can be designed, that is, the step length can be changed as the adjustment progresses. This step-size-related algorithm is also a conventional algorithm.

S36. Repeat steps S32 to S35 to make the correction value of the target parameter approach the maximum value, and then make the IQ signal phase error approach the minimum value.

It can be seen from the above that, in this embodiment, it is necessary to satisfy: when the target parameter approaches the minimum value, the IQ signal phase error approaches the minimum value. Therefore, if the correction value is greater than the initial value y ₀ , it indicates that the value of the target parameter becomes larger and the adjustment direction of the reference channel needs to be changed. If the correction value is less than the initial value y ₀ , it indicates that the adjustment direction of the reference channel is correct. Keep this adjustment direction and continue to adjust , Make the target parameter gradually approach the minimum, and then make the IQ signal phase error approach the minimum.

Based on the target parameters given in the embodiment, the adjustment result obtained through simulation is shown in Figure 3 (including two parts (a) and (b)). The simulation conditions ignore the sampling error, ignore the signal noise, etc., use a random value as the signal code stream, and the phase error before compensation is 20 degrees (in this case, R ₁ =R ₂ =R ₃ =R ₄ ). In the simulation, I and Q are adjusted alternately. After the I channel and the Q channel are adjusted once, one iteration is considered to be completed.

The abscissa in Fig. 3 is the number of iterations, the ordinate in (a) is the phase error after compensation by the adjustment intensity coefficient, and the ordinate in (b) is the value of the target parameter y after each iteration. It can be seen that after adjusting the intensity coefficient, the phase error is compensated.

In summary, the present invention collects the current or voltage values of the I signal and the Q signal and defines target parameters to characterize the phase error. Separately adjust the intensity coefficients of the 4 channels to make the target parameter reach the minimum or maximum value, and then the corresponding phase error to the minimum value, so as to realize the compensation of the system phase error. Moreover, the method adopted in the present invention does not change the original hardware composition of the system, does not require a phase shifter, has low power consumption and low cost, and can meet the requirements of the ultra-100G coherent optical communication system for phase error.

Referring to FIG. 4, an embodiment of the present invention also provides an IQ signal phase error control system, including: an optical mixer, an I-channel photodetector, a Q-channel photodetector, and a control unit. As shown in Figure 5, the control unit includes an acquisition module, a calculation module, and an adjustment module.

Among them, the optical mixer is used to mix the received signal light and the local oscillator light and output;

I path photodetector, the input end of which is connected with the output end of the optical mixer;

Q-channel photodetector, the input end of which is connected to the output end of the optical mixer;

The input terminal of the acquisition module is respectively connected with the output terminals of the I-channel photodetector and the Q-channel photodetector, and the acquisition module is used to acquire the electric signal value vectors of the I-channel signal and the Q-channel signal.

An electrical signal refers to a voltage or current that changes with time. In this embodiment, you can select whether to collect voltage or current according to needs:

When collecting voltages, the collecting module is used to collect the voltage values of the I-channel signal and the Q-channel signal in each period of the N cycles, as the value of the N elements that establish the voltage value vector of the I-channel signal and the Q-channel signal.

When collecting current, the collecting module is used to collect the current values of the I-channel signal and the Q-channel signal in each period of the N cycles, as the value of the N elements that establish the current value vector of the I-channel signal and the Q-channel signal.

The following takes the voltage collected by the collecting module as an example for specific introduction:

In this embodiment, the control unit may be a DSP (Digital Signal Processing, digital signal processing) chip. Both the I-channel photodetector and the Q-channel photodetector include a photodiode PD, or the I-channel photodetector and the Q-channel photodetector both include a photodiode PD and a transimpedance amplifier TIA. The photodiode PD is used to convert the optical signal into a current signal, and the transimpedance amplifier TIA is used to convert the current signal of the photodiode PD into a voltage signal. It can be determined whether to collect the current value or the voltage value through the above two implementation methods.

Further, in this embodiment, the electrical signal values of one I signal and one Q signal are respectively collected at the respective decision points of each of the N cycles. The decision point is for the eye diagram. The eye diagram is the result of accumulating and superimposing the bits of the collected serial signal with the afterglow method. When the signal-to-noise ratio reaches the optimal value, the eye diagram opening reaches the maximum. It is the best time for sampling, also called the decision point. The decision point is determined by the control unit, such as the general algorithm calculation of the DSP chip.

The calculation module is used to calculate the function value of the target parameter. The target parameter is a function of the electrical signal value vector of the I signal and the Q signal as an independent variable, and the target parameter is configured as: when the target parameter tends to When it is near the minimum value, the phase error of the IQ signal approaches the minimum value.

As a better implementation, the expression of the target parameter is:

y=|E{I*Q}|/(E{|I|}*E{|Q|}), where:

E{|I|}=(|I ₁ |+|I ₂ |+|I ₃ |+...+|I _N-1 |+|I _N |)/N;

E{|Q|}=(|Q ₁ |+|Q ₂ |+|Q ₃ |+...+|Q _N-1 |+|Q _N |)/N;

That is, the expression of the target parameter is:

y=(E{|I|}*E{|Q|})/|E{I*Q}|, where:

E{|I|}=(|I ₁ |+|I ₂ |+|I ₃ |+...+|I _N-1 |+|I _N |)/N;

E{|Q|}=(|Q ₁ |+|Q ₂ |+|Q ₃ |+...+|Q _N-1 |+|Q _N |)/N;

Preferably, the adjustment module adjusts the intensity coefficient of the channel by adjusting the optical power of the output optical path of the optical mixer, the responsivity of the photodiode PD, and/or the gain coefficient of the transimpedance amplifier TIA.

As a better implementation, the adjustment module is used to adjust the intensity coefficients of the channels corresponding to the I-channel signal and the Q-channel signal, so that the target parameter approaches the maximum value, and then the IQ signal phase error approaches the minimum value. The specific process includes:

S31. Preset the initial intensity coefficient of each channel, and calculate the initial value y _{0 of the} target parameter according to the initial electrical signal value vector of the I signal and the Q signal;

The preset alternation rule refers to: adjusting one set of channels P times first, and then adjusting another set of channels Q times as a cycle, repeating the adjustment of the two sets of channels. As shown in the figure, the 4 channels can be divided into two groups, the first group includes channel 1 and channel 2, and the second group includes channel 3 and channel 4. The adjustment order of the first group and the second group can be exchanged, the adjustment order of the channel 1 and the channel 2 in the first group can be exchanged, and the adjustment order of the channel 3 and the channel 4 in the second group can also be exchanged.

For example, if P and Q are both 1, then the first group and the second group are alternated in turn. If both P and Q are 10, then the first group can be adjusted 10 times in succession, and then the second group can be adjusted continuously. 10 times and cycle in this way.

The present invention is not limited to the above-mentioned embodiments. For those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also regarded as the protection of the present invention. Within range. The content not described in detail in this specification belongs to the prior art known to those skilled in the art.

Claims

An IQ signal phase error control method, characterized in that the method includes the following steps:

Collect and obtain the electric signal value vector of I signal and Q signal;

Calculate the function value of the target parameter. The target parameter is a function of the electrical signal value vector of the I signal and the Q signal as the independent variable, and the target parameter is configured as: when the function value of the target parameter approaches the maximum value, the IQ signal The phase error approaches the minimum;

Adjust the intensity coefficients of the channels corresponding to the I signal and the Q signal to make the function value of the target parameter approach the most value.
The method for controlling the phase error of an IQ signal according to claim 1, wherein the expression of the target parameter is:

y=|E{I*Q}|/(E{|I|}*E{|Q|}), where:

E{|I|}=(|I 1 |+|I 2 |+|I 3 |+...+|I N-1 |+|I N |)/N;

E{|Q|}=(|Q 1 |+|Q 2 |+|Q 3 |+...+|Q N-1 |+|Q N |)/N;

E{I*Q}=(I 1 *Q 1 +I 2 *Q 2 +I 3 *Q 3 +...+I N-1 *Q N-1 +I N *Q N )/N;

I and Q are the electric signal value vectors of I signal and Q signal respectively, I N is the Nth electric signal value of I signal in N acquisitions, and Q N is the Nth signal of Q signal in N acquisitions Electric signal value, N is a positive integer.
The method for controlling the phase error of an IQ signal according to claim 1, wherein the expression of the target parameter is:

y=(E{|I|}*E{|Q|})/|E{I*Q}|, where:

E{|I|}=(|I 1 |+|I 2 |+|I 3 |+...+|I N-1 |+|I N |)/N;

E{|Q|}=(|Q 1 |+|Q 2 |+|Q 3 |+...+|Q N-1 |+|Q N |)/N;

E{I*Q}=(I 1 *Q 1 +I 2 *Q 2 +I 3 *Q 3 +...+I N-1 *Q N-1 +I N *Q N )/N;

I and Q are the electric signal value vectors of I signal and Q signal respectively, I N is the Nth electric signal value of I signal in N acquisitions, and Q N is the Nth signal of Q signal in N acquisitions Electric signal value, N is a positive integer.
An IQ signal phase error control method according to claim 2 or 3, characterized in that the intensity coefficient of the channel corresponding to the I signal and the Q signal is adjusted to make the function value of the target parameter approach the maximum value, and then Make the phase error of the IQ signal approach the minimum, including:

S31. Preset the initial intensity coefficient of each channel, and calculate the initial value y 0 of the target parameter according to the initial value of the electrical signal value vector of the I signal and the Q signal;

S32. Divide the 4 channels into two groups to correspond to the I signal and the Q signal, and the phase difference of the two channels in each group is a preset degree, based on the boundary conditions of the intensity coefficient of the channel, alternate according to the preset The rule adjusts the intensity coefficients of the two groups of channels. When adjusting one of the channels, the first adjusted channel is used as the reference channel, and the adjustment direction of the reference channel is recorded. When the reference channel is adjusted once, the next The intensity coefficient of the adjusted channel is continuously adjusted, and E{|I|} and E{|Q|} are calculated in real time until it meets |E{|I|}-E{|Q|}|≤A, where A is the default Threshold

S33. Calculate the correction value of the target parameter by using the electrical signal values of the N times I signal and N times Q signal collected when |E{|I|}-E{|Q|}|≤A If the value is greater than the initial value y 0 , step S34 is executed, and if the correction value is less than the initial value y 0 , step S35 is executed;

S34. Return to step S32, and change the adjustment direction of the intensity coefficient of the reference channel;

S35. Return to step S32, and keep the adjustment direction of the intensity coefficient of the reference channel unchanged;

S36. Repeat steps S32 to S35 to make the correction value of the target parameter approach the maximum value.
The method for controlling the phase error of an IQ signal according to claim 4, wherein the collecting and obtaining the electric signal value vector of the I signal and the Q signal specifically includes:

Use the voltage values of the I signal or the Q signal collected in each period of the N cycles as the vector element to establish the voltage value vector of the I signal and the Q signal;

Or, the current value of the I signal or the Q signal collected in each of the N cycles is used as the vector element to establish the current value vector of the I signal and the Q signal.
An IQ signal phase error control method according to claim 5, characterized in that the voltage value of the I signal or the Q signal collected in each period of the N cycles is used as a vector element to establish the I signal and The voltage value vector of the Q signal includes:

Collect the voltage value of I signal once in each period of N cycles, the voltage value of I signal meets: V I =R 1 cos(ωt)-R 2 cos(ωt+Δθ 2-1 )=R I cos (ωt+Δθ I );

Collect the voltage value of the Q signal in each period of N cycles, and the voltage value of the Q signal meets V Q = R 3 cos(ωt+Δθ 3-1 )-R 4 cos(ωt+Δθ 4-1 ) =R Q cos(ωt+Δθ Q );

Wherein, R i (i = 1 ~ 4) represents an intensity coefficient of the i-th channels, ω is the signal light and the local light optical frequency difference, Δθ j-1 (j = 2,3,4) represents the j-th passage The phase difference between the channel and the first channel, R I and R Q are the intensity coefficients of I and Q respectively, and Δθ Q -Δθ I -π/2 represents the phase error;

Take the collected voltage values of the N channels I signals as the values of the N elements of the voltage value vector of the I channels;

The voltage values of the N signals of the Q channels are collected as the values of the N elements of the voltage value vector of the Q signals.
An IQ signal phase error control method according to claim 1, characterized in that: the optical power of the optical mixer output optical path, the photodiode PD responsivity and/or the transimpedance amplifier TIA gain coefficient are adjusted to control the channel The intensity factor is adjusted.
An IQ signal phase error control system, characterized in that it comprises:

The control unit is used to control the phase error of the IQ signal by adjusting the intensity coefficients of the channels corresponding to the I signal and the Q signal.
The IQ signal phase error control system according to claim 8, wherein the control unit comprises:

An acquisition module, which is used to acquire the electrical signal value vectors of the I signal and the Q signal;

The calculation module is used to calculate the function value of the target parameter. The target parameter is a function of the electrical signal value vector of the I signal and the Q signal as an independent variable, and the target parameter is configured as: When the function value approaches the maximum value, the phase error of the IQ signal approaches the minimum value; and

The adjustment module is used to adjust the intensity coefficients of the channels corresponding to the I-channel signal and the Q-channel signal, so that the function value of the target parameter approaches the maximum value, and then the phase error of the IQ signal approaches the minimum value.
The IQ signal phase error control system of claim 9, wherein the adjustment module adjusts the optical power of the optical mixer output optical path, the photodiode PD responsivity and/or the transimpedance amplifier TIA gain coefficient To adjust the intensity coefficient of the channel.