Iq modulator bias control method, system, and medium based on dither vector monitoring

Abstract

The application discloses an IQ modulator bias control method and system based on a dithering vector monitoring, and a medium, and belongs to the optical communication field.The method comprises the following steps: taking the optical power of an IQ modulator being equal to a target optical power as a target, and coarsely adjusting I-path bias voltage and Q-path bias voltage applied to the IQ modulator in a set range; adding square wave signals to the obtained I-path bias voltage and Q-path bias voltage respectively; cyclically fixing two bias voltages in the I-path bias voltage, the Q-path bias voltage and P-path bias voltage, and finely adjusting the other bias voltage until the I-path dithering mapping vector absolute value, the Q-path dithering mapping vector absolute value and the P-path dithering mapping vector absolute value of the IQ modulator all converge to 0.The calculation method is greatly simplified, the calculation cost is reduced on the basis of ensuring the control accuracy, and the method is suitable for transmission scenes of any modulation format.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of optical communication, and more particularly relates to an IQ modulator bias control method, system and medium based on jitter vector monitoring. BACKGROUND

[0002] A coherent optical communication system is of great concern due to its huge transmission capacity, and an in-phase and quadrature phase modulator (IQM) is one of the most important components. Due to the internal structure and nonlinear transmission characteristics of the IQM, the bias point of the IQM is easily affected by changes in time, environmental temperature and applied electric field, thereby significantly reducing the transmission performance. Therefore, it is necessary to control the bias point of the IQM to maintain the target state.

[0003] The control of the IQ modulator includes bias phase control of an I-path MZM modulator, bias phase control of a Q-path MZM modulator and bias phase control of a P-path phase shifter. The currently used IQ modulator bias point control method mainly includes an optical power monitoring method and a jitter signal monitoring method. For the optical power monitoring method, the method of eliminating jitter by monitoring optical power and analyzing optical power changes. For the jitter signal monitoring method, the power spectrum of the 1st jitter harmonic signal and the 2nd jitter harmonic signal is analyzed and calculated through fast Fourier transform operation, or the control is performed in the manner of monitoring the harmonic signal through correlation calculation. The above methods all need to perform harmonic monitoring, and the calculation complexity and cost are high, and a direct digital frequency synthesizer needs to be used, and the hardware cost is also high. Therefore, how to develop an IQ modulator bias point control method with low cost, high precision and easy implementation is of great significance. SUMMARY

[0004] In view of the defects and improvement needs of the prior art, the application provides an IQ modulator bias control method, system and medium based on jitter vector monitoring, which aims to solve the problems of high measurement cost, poor stability and complex implementation of the existing IQ modulator bias point control method.

[0005] To achieve the above object, according to one aspect of the present application, an IQ modulator bias control method based on a dither vector monitor is provided, comprising: S1, coarsely adjusting I and Q bias voltages applied to the IQ modulator in a set range, with the target of the optical power of the IQ modulator being equal to a target optical power; S2, adding a square wave signal to the I and Q bias voltages obtained in the S1 to obtain new I and Q bias voltages; S3, cyclically fixing two bias voltages among the I, Q and P bias voltages, and finely adjusting the other bias voltage, until the absolute values of I, Q and P dither mapping vectors of the IQ modulator all converge to 0.

[0006] Further, the square wave signal is a random square wave sequence, and the random square wave sequence added in the S2 satisfies:

[0007]

[0008] Wherein, f I (n) is the nth point of the random square wave array added in the I bias voltage, f Q (n) is the nth point of the random square wave array added in the Q bias voltage, and N is the point number of the random square wave sequence.

[0009] Further, the amplitude of the random square wave sequence is 0.001V π ~0.1%V π , V π is the half-wave voltage of the IQ modulator, and the frequency bandwidth of the random square wave sequence is 1 kHz~100 kHz.

[0010] Further, the S3 further comprises: injecting a dither vector signal into the I path of the IQ modulator, and calculating an I dither mapping vector according to the real-time optical power of the IQ modulator; injecting a dither vector signal into the Q path of the IQ modulator, and calculating a Q dither mapping vector according to the real-time optical power of the IQ modulator; injecting a dither vector signal into the I and Q paths of the IQ modulator at the same time, monitoring I and Q dither vector mapping components in the output optical signal of the IQ modulator, and calculating a P dither mapping vector according to the projection of the I dither vector mapping component in the Q direction and the projection of the Q dither vector mapping component in the I direction.

[0011] Further, the S3 comprises: S31, fixing the Q-path bias voltage and the P-path bias voltage, taking the I-path jitter mapping vector absolute value reduction as a target, fine-tuning the I-path bias voltage; S32, fixing the I-path bias voltage and the P-path bias voltage, taking the Q-path jitter mapping vector absolute value reduction as a target, fine-tuning the Q-path bias voltage; S33, fixing the I-path bias voltage and the Q-path bias voltage, taking the P-path jitter mapping vector absolute value reduction as a target, fine-tuning the P-path bias voltage; S34, repeatedly executing the S31-S33 until the I-path jitter mapping vector absolute value, the Q-path jitter mapping vector absolute value and the P-path jitter mapping vector absolute value all converge to 0.

[0012] Further, the I-path bias voltage, the Q-path bias voltage and the P-path bias voltage after each fine-tuning are respectively:

[0013]

[0014]

[0015]

[0016] wherein, V I(n+1) , V Q(n+1) , V P(n+1) are respectively the I-path bias voltage, the Q-path bias voltage and the P-path bias voltage after the n+1th fine-tuning, are respectively the I-path jitter mapping vector, the Q-path jitter mapping vector and the P-path jitter mapping vector after the nth fine-tuning, K p1 is a first proportional parameter, K i1 is a first integral parameter, K d1 is a first differential parameter, K p2 is a second proportional parameter, K i2 is a second integral parameter, K d2 is a second differential parameter, K p3 is a third proportional parameter, K i3 is a third integral parameter, K d3 is a third differential parameter.

[0017] Further, the S1 comprises: initializing the I-path bias voltage, the Q-path bias voltage and the P-path bias voltage to 0; fixing the P-path bias voltage, taking the optical power of the IQ modulator tending to the target optical power as a target, alternately coarsely tuning the I-path bias voltage and the Q-path bias voltage within the set range.

[0018] Further, the S1 further comprises: giving the target optical power according to a target function of the IQ modulator; wherein the target optical power is a direct current optical power minimum point or a direct current optical power maximum point of the IQ modulator, or is any point between the direct current optical power minimum point and the direct current optical power maximum point.

[0019] According to another aspect of the present application, there is provided an IQ modulator bias control system based on jitter vector monitoring, comprising: a coarse adjustment module, configured to coarsely adjust I and Q bias voltages applied to the IQ modulator in a set range, with the optical power of the IQ modulator equaling a target optical power as a target; an adding module, configured to add square wave signals to the I and Q bias voltages obtained by the IQ modulator coarse adjustment module, to obtain new I and Q bias voltages; and a fine adjustment module, configured to fix two of the I, Q and P bias voltages and finely adjust the other bias voltage, until the absolute values of I, Q and P jitter mapping vectors of the IQ modulator all converge to 0.

[0020] According to another aspect of the present application, there is provided a computer readable storage medium, having a computer program stored thereon, the program being executed by a processor to implement the IQ modulator bias control method based on jitter vector monitoring as described above.

[0021] Overall, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0022] (1) An IQ modulator bias control method based on jitter vector monitoring is provided, the size and direction of the introduced I, Q and P jitter mapping vectors are used to perform closed-loop feedback control on the IQ modulator bias point, compared with the prior art, without the need for frequency spectrum analysis or correlation calculation on the feedback signal of the disturbance signal, only addition and subtraction operations are needed, greatly simplifying the calculation method, reducing the calculation cost on the basis of ensuring control accuracy; in addition, the size of the I, Q and P jitter mapping vectors is irrelevant to the radio frequency signal input from the outside of the IQ modulator, and has no dependence on the input signal, so that the method is applicable to any modulation format transmission scenario;

[0023] (2) The square wave signal is used as the jitter vector, and the anti-interference property of the square wave signal can improve the signal-to-noise ratio of the monitoring vector, therefore, the method has lower requirements for the amplitude of the square wave signal than other traditional bias control methods, and has higher control accuracy, and experiments have verified that the control accuracy of the method can be within ±1°, with extremely high control accuracy;

[0024] (3) preferably, the random square wave signal is used, compared with the periodic square wave signal, the random square wave signal has higher bandwidth, the random square wave signal has lower power spectrum density and lower power spectrum peak value under the same power, so that the random dithering vector has lower disturbance to the transmission link signal, in addition, the random square wave signal has stronger anti-interference capability, so that the method can be applied to special scenes such as high power and high noise;

[0025] (4) in the adjustment process, the size and direction of the mapping vector are calculated to obtain the electro-optical characteristic parameters and curve of the IQ modulator, therefore, the method can set the tracking target as the minimum direct current light power, the maximum direct current light power or any value between the two, the function is more comprehensive and the application range is wider. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The flow chart of the IQ modulator bias control method based on the dithering vector monitoring provided by the embodiment of the application is shown in the figure.

[0027] Figure 2 The structure diagram of the IQ modulator provided by the embodiment of the application is shown in the figure.

[0028] Figure 3 The block diagram of the IQ modulator bias control system based on the dithering vector monitoring provided by the embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the application clearer, the application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application, and are not used to limit the application. In addition, the technical features involved in each embodiment of the application described below can be combined with each other as long as there is no conflict.

[0030] In the application, the terms "first", "second", etc. (if any) in the application and the drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0031] Figure 1 The flow chart of the IQ modulator bias control method based on the dithering vector monitoring provided by the embodiment of the application is shown in the figure. Figure 1 , in combination with Figure 2 , the IQ modulator bias control method based on the dithering vector monitoring in the embodiment is described in detail, and the method comprises operations S1-S3.

[0032] Referring to Figure 1The IQ modulator is composed of two sub-Mach-Zehnder modulators (MZM) and a phase shifter P (or phase delay). The I-path MZM (MZM_I) and the Q-path MZM (MZM_Q) can respectively modulate the phase of the optical carrier signals loaded on the I-path and the Q-path, and the phase shifter P ensures that the phases of the two optical carriers are orthogonal when they are combined.

[0033] In operation S1, the I-path bias voltage and the Q-path bias voltage applied to the IQ modulator are coarsely adjusted within a set range, with the goal that the optical power of the IQ modulator is equal to the target optical power.

[0034] In this embodiment, the optical power of the IQ modulator can be measured by the signal acquisition module and the power monitoring module; the dithering mapping vector can be monitored by the dithering vector monitoring module; and the bias point control can be realized by the feedback control module and the function selection module.

[0035] The signal acquisition module includes a 1:9 optical coupler or a 1:99 optical coupler, a photodetector, an analog-to-digital converter, etc. The input end of the 1:9 optical coupler or the 1:99 optical coupler is connected to the output end of the IQ modulator, the 10% output end of the 1:9 optical coupler or the 1% output end of the 1:99 optical coupler is connected to the input end of the photodetector, and the output end of the photodetector is connected to the input end of the analog-to-digital converter; the 1:9 optical coupler or the 1:99 optical coupler is the input end of the signal acquisition module, and the analog-to-digital converter is the output end of the signal acquisition module. The 1:9 optical coupler or the 1:99 optical coupler functions to divide the IQ modulator output optical signal into two signals with proportional power and the same composition. In order to meet the demand of normal service transmission, the small-power optical signal should be used for bias point control; the photodetector has a sensitivity greater than -40 dBm to meet the demand of minimum optical power adjustment and convert the optical signal into an electrical signal in real time; the analog-to-digital converter quantizes, samples and encodes the electrical signal into a digital signal and outputs it to the power monitoring module and the dithering vector monitoring module. Before being output to the analog-to-digital converter, the photodetector will be subjected to signal separation and amplification. The real-time optical signal will be separated into a direct current signal and an alternating current signal. The direct current signal is usually amplified by 2-10 times, and the alternating current signal is usually amplified by 10-30 times to ensure that the signal can reach the sampling threshold of the analog-to-digital converter. The direct current signal is input to the power monitoring module, and the alternating current signal is input to the dithering vector monitoring module. The power monitoring module is used to calculate the direct current average optical power s'(t) of the IQ modulator:

[0036]

[0037]

[0038] Where s(t) is the real-time optical power of the IQ modulator, t is time, and T is the detection period. I(t) is the optical power signal of the I-channel MZM modulator, and Q(t) is the optical power signal of the MZM modulator. I(t) and Q(t) satisfy:

[0039]

[0040]

[0041]

[0042] According to an embodiment of the present invention, before performing operation S1, the method further includes: specifying a target optical power based on the target function of the IQ modulator; wherein the target optical power is the minimum point s′(t) of the DC optical power of the IQ modulator. min Or the point of maximum DC optical power s′(t) max Or, it could be the point of minimum DC optical power, s′(t). min The point of maximum DC optical power s′(t) max Any point between these values. The target optical power can be adjusted to maximum power, minimum power, or any power in between through the value set in the function selection module.

[0043] According to an embodiment of the present invention, operation S1 includes sub-operations S11-S12.

[0044] In sub-operation S11, the I-channel bias voltage V I Q-path bias voltage V Q and P-circuit bias voltage V P Initialize to 0.

[0045] In sub-operation S12, the P-path bias voltage V is fixed. P With the goal of making the optical power of the IQ modulator approach the target optical power, the bias voltage V of the I-path is coarsely adjusted alternately within a set range. I and Q-path bias voltage V Q .

[0046] Taking a digital-to-analog converter module with an output range of -10V to 10V and a target optical power of the minimum DC optical power as an example, the setting range can be set to -10V to 10V, and the bias voltage output value can be set to a range of -10V to 10V with a spacing of V. π Several voltage points of / 10. Adjust V according to the above-mentioned voltage points. I V Q V P Keeping it constant, increase V sequentially. I The value of V is monitored, and the average DC optical power corresponding to the bias voltage at this time is found to find the minimum average DC optical power. I ; Keep VI , V P is fixed, V Q is adjusted in the same way Q , and V I is adjusted in the same way Q , until the direct current light power is as small as possible. It should be noted that during the adjustment, V Q may be adjusted first, and then V I may be adjusted.

[0047] During the above coarse adjustment, the real-time light power of the IQ modulator with the dithering vector can be expressed as:

[0048]

[0049] In operation S2, a square wave signal is added to the I-bias voltage and the Q-bias voltage obtained in operation S1 respectively to obtain new I-bias voltage and Q-bias voltage.

[0050] In the embodiment of the present application, the added square wave signal can be a periodic square wave sequence or a random square wave sequence.

[0051] When the square wave signal is a periodic square wave sequence, the periodic square wave sequence f I (t) added to the I-bias voltage and the periodic square wave sequence f Q (t) added to the Q-bias voltage can be expressed as:

[0052]

[0053]

[0054] wherein the amplitude A is 0.001V π ~0.1%V π , and k is an integer. The frequency bandwidth of the periodic square wave sequence is 1kHz~100kHz. T I , T Q may be the same or different. When they are the same, the direct current signal after the photodetector needs to be filtered out, and when they are different, the direct current signal after the photodetector does not need to be filtered out.

[0055] When the square wave signal is a random square wave sequence, the random square wave sequence f I added to the I-bias voltage and the random square wave sequence f Q added to the Q-bias voltage can be expressed as:

[0056] f I =A{1,-1,-1,-1,1,-1,1…} ​

[0057] f Q = A{1, -1, 1, 1, 1, -1, 1, 1, 1, -1,...}

[0058] f I , f Q satisfy:

[0059]

[0060] wherein f I (n) is the nth point of the random square wave array added in the I-path bias voltage, f Q (n) is the nth point of the random square wave array added in the Q-path bias voltage, and N is the number of points of the random square wave sequence. The amplitude A of the random square wave sequence is 0.001V π ~ 0.1%V π , V π is the half-wave voltage of the IQ modulator, the frequency bandwidth of the random square wave sequence is 1 kHz ~ 100 kHz. The integral sum of the random square wave sequence is 0, and the mean value does not have a direct current component.

[0061] T I , T Q is usually 2 ms ~ 400 ms, and the detection period T is usually 1 ms ~ 200 ms. In order to ensure the real-time performance and calculation accuracy of the IQ modulator, the detection period should not be set too long, and is preferably set to 100 ms. Usually, when the periodic square wave is set as the dithering vector signal, the frequency is 1 kHz ~ 10 kHz; when the random square wave is set as the dithering vector signal, the bandwidth is set to 1 kHz ~ 100 kHz, and the signal sampling frequency is 200 ~ 750 kHz.

[0062] In the embodiment, the anti-interference property of the square wave signal is utilized to improve the signal-to-noise ratio of the monitored dithering vector, and the requirement for the square wave signal amplitude is lower than that of other traditional bias control schemes. Compared with the periodic square wave sequence, the random square wave array has a higher bandwidth, a lower power spectrum density and a lower power spectrum peak value under the same power, so that the random dithering vector has a lower disturbance to the transmission link signal.

[0063] The I-path bias voltage V I and the Q-path bias voltage V Q after adding the square wave signal are respectively:

[0064] V I = f I + V' I

[0065] V Q = f Q + V' Q

[0066] wherein, V' I , V' Q are the I-path bias voltage and the Q-path bias voltage respectively before adding the square wave signal.

[0067] In operation S3, two of the I-path bias voltage, the Q-path bias voltage and the P-path bias voltage are fixed, and the other bias voltage is finely adjusted until the I-path dithering mapping vector absolute value, the Q-path dithering mapping vector absolute value and the P-path dithering mapping vector absolute value of the IQ modulator all converge to 0.

[0068] According to the embodiment of the present application, before operation S3, the following operations (1)-(3) are further included, which can be realized by a dithering vector monitoring module.

[0069] (1) injecting a dithering vector signal into the I-path of the IQ modulator, and calculating the I-path dithering mapping vector according to the real-time optical power of the IQ modulator

[0070]

[0071] (2) injecting a dithering vector signal into the Q-path of the IQ modulator, and calculating the Q-path dithering mapping vector according to the real-time optical power of the IQ modulator

[0072]

[0073] (3) injecting a dithering vector signal into the I-path and the Q-path of the IQ modulator simultaneously, monitoring the I-path dithering vector mapping component and the Q-path dithering vector mapping component in the output optical signal of the IQ modulator, and calculating the P-path dithering mapping vector according to the projection of the I-path dithering vector mapping component in the Q-path direction and the projection of the Q-path dithering vector mapping component in the I-path direction

[0074]

[0075] wherein, I I (A), I I (-A) are the optical powers when the I-path output dithering vector amplitude is A, -A respectively, I Q (A), I Q (-A) are the optical powers when the Q-path output dithering vector amplitude is A, -A respectively, are the projection of the I-path dithering vector mapping component in the Q-path direction and the projection of the Q-path dithering vector mapping component in the I-path direction respectively, V BiasI , V BiasQ , V BiasP are the bias of the I-path control signal, the bias of the Q-path control signal and the bias of the P-path control signal of the IQ modulator at the current moment respectively, VπI , V πQ , V πP respectively are IQ modulator I path half-wave voltage, Q path half-wave voltage, P path half-wave voltage.

[0076] According to the embodiment of the application, the operation S3 comprises sub-operation S31-sub-operation S33.

[0077] In the sub-operation S31, the I path bias voltage is fine-tuned with the Q path bias voltage and the P path bias voltage fixed, with the I path dithering mapping vector absolute value reduction as the target.

[0078] In the IQ modulator, the I path and the Q path are orthogonal, at this time the bias phase of the I path and the Q path is π, and the bias phase of the phase shifter P is π / 2 or 3π / 2. When the I path dithering mapping vector absolute value is reduced, the bias phase of the MZM_I tends to be π or 0, and the adjustment step should be less than 1%V ~ 40%V. With the increase of the bias voltage, when the change direction of the mapping vector is positive vector→zero vector→negative vector, the bias phase of the MZM_I tends to be 0; otherwise, the bias phase of the MZM_I tends to be π. The Q path adjustment principle is the same as the I path adjustment principle. π π

[0079] In the sub-operation S32, the Q path bias voltage is fine-tuned with the I path bias voltage and the P path bias voltage fixed, with the Q path dithering mapping vector absolute value reduction as the target.

[0080] In the sub-operation S33, the P path bias voltage is fine-tuned with the I path bias voltage and the Q path bias voltage fixed, with the P path dithering mapping vector absolute value reduction as the target.

[0081] When the P path dithering mapping vector absolute value is reduced, the bias phase of the phase shifter tends to be π / 2 or 3π / 2, and the adjustment step should be less than 1%V ~ 40%V. With the increase of the bias voltage, when the change direction of the mapping vector is positive vector→zero vector→negative vector, the bias phase of the MZM_I tends to be π / 2; otherwise, the bias phase of the MZM_I tends to be 3π / 2. π π

[0082] In the sub-operation S34, the sub-operation S31-sub-operation S33 are repeatedly executed until the I path dithering mapping vector absolute value, the Q path dithering mapping vector absolute value and the P path dithering mapping vector absolute value all converge to 0.

[0083] ​​​​Since the whole control process needs multiple iterations to reach the optimal target bias point (π, π, π / 2), the sub-operation S31-sub-operation S33 needs to be repeated multiple times. When the physical characteristics such as environmental temperature and pressure change, the state of the electro-optic crystal of the IQ modulator changes, the bias state and characteristic parameters of each MZM modulator in the IQ modulator change, and then the bias state of the modulator deviates. Therefore, real-time dynamic tracking and locking of the target bias phase are needed. Even if the characteristic parameters of the IQ modulator change, and tend to 0, the bias phase of the corresponding IQ modulator will not change, and therefore only the bias voltage needs to be adjusted to achieve real-time dynamic tracking and locking of the target bias phase. and

[0084] It should be noted that during the loop adjustment process, V I , V Q , and V P may be adjusted in this order, or V I , V P , and V Q may be adjusted in this order, or V Q , V I , and V P may be adjusted in this order, or V Q , V P , and V I may be adjusted in this order, or V P , V I , and V Q may be adjusted in this order, or V P , V Q , and V I may be adjusted in this order.

[0085] In this embodiment, only the I-path dither mapping vector, the Q-path dither mapping vector, the P-path dither mapping vector, and the bias voltage need to be tracked and adjusted to keep each bias phase of the IQ modulator locked around the target bias point. Therefore, a corresponding closed-loop feedback control algorithm is needed to speed up this feedback adjustment process.

[0086] Preferably, the PID control method is used for the fine adjustment operation in this embodiment. The I-path bias voltage, the Q-path bias voltage, and the P-path bias voltage after each fine adjustment are as follows:

[0087]

[0088]

[0089]

[0090] wherein V​I(n+1) , V Q(n+1) , V P(n+1) respectively are the I-path bias voltage, the Q-path bias voltage, the P-path bias voltage after the (n+1)th fine adjustment, respectively are the I-path dither mapping vector, the Q-path dither mapping vector, the P-path dither mapping vector after the nth fine adjustment, K p1 is a first proportional parameter, K i1 is a first integral parameter, K d1 is a first differential parameter, K p2 is a second proportional parameter, K i2 is a second integral parameter, K d2 is a second differential parameter, K p3 is a third proportional parameter, K i3 is a third integral parameter, K d3 is a third differential parameter. The parameters used in the PID control can be determined according to the actual application scenario. Through the above feedback adjustment, V I , V Q , V P will automatically converge to the target value.

[0091] The control mode of the iterative tracking is not limited to the PID control. As long as the scheme of using the dither vector mapping monitoring to feedback adjust the bias phase is adopted, the equivalent replacement and improvement of the parameters of the scheme should be included in the protection scope of the present application. For example, the Newton iteration method is used for iterative tracking, and the fast and stable robust control can also be achieved.

[0092] The feedback control module outputs the I-path bias voltage, the Q-path bias voltage and the P-path bias voltage to the digital-to-analog converter, and the digital-to-analog converter outputs each path bias voltage to the IQ modulator bias voltage output pin correspondingly.

[0093] Compared with the current other scheme related detection (CI) and spectrum analysis method, the method in the embodiment of the present application has higher sensitivity, lower algorithm complexity and faster tracking time. This is because the vector signal has better anti-noise capability, so that the method in the embodiment has higher sensitivity, lower algorithm complexity and shorter tracking time. The tracking time of the method is only 0.3s-0.5s.

[0094] The embodiment of the present application is specifically described for the case of single polarization IQ modulator. For the double polarization IQ modulator, the specific implementation and the above single polarization IQ modulator scheme are similar, and details are not repeated here.

[0095] Figure 3 is the block diagram of the IQ modulator bias control system based on the dither vector monitoring provided by the embodiment of the present application. Referring to Figure 3The IQ modulator bias control system 300 based on the dither vector monitoring comprises a fine adjustment module 310, an adding module 320 and a coarse adjustment module 330.

[0096] The fine adjustment module 310 performs operation S1, for example, to coarsely adjust the I-path bias voltage and the Q-path bias voltage applied to the IQ modulator in a set range, with the optical power of the IQ modulator equal to the target optical power as the target.

[0097] The adding module 320 performs operation S2, for example, to add a square wave signal to the I-path bias voltage and the Q-path bias voltage obtained by the IQ path coarse adjustment module, respectively, to obtain new I-path bias voltage and Q-path bias voltage.

[0098] The coarse adjustment module 330 performs operation S3, for example, to loop two bias voltages of the I-path bias voltage, the Q-path bias voltage and the P-path bias voltage, and finely adjust the other bias voltage, until the I-path dither mapping vector absolute value, the Q-path dither mapping vector absolute value and the P-path dither mapping vector absolute value of the IQ modulator all converge to 0.

[0099] The IQ modulator bias control system 300 based on the dither vector monitoring is used to perform the IQ modulator bias control method based on the dither vector monitoring in the above Figures 1-2 embodiment. The details of the present embodiment not described above can be referred to the above Figures 1-2 embodiment. The details of the present embodiment not described above can be referred to the above

[0100] The present embodiment further provides a computer readable storage medium having a computer program stored thereon. The program is executed by a processor to implement the IQ modulator bias control method based on the dither vector monitoring in the above Figures 1-2 embodiment. The details of the present embodiment not described above can be referred to the above

[0101] Those skilled in the art can easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An IQ modulator bias control method based on dither vector monitoring, characterized by, Comprising: S1, targeting at the light power of the IQ modulator equaling to a target light power, coarsely adjusting the I-path bias voltage and the Q-path bias voltage applied on the IQ modulator within a set range; S2, adding a square wave signal to the I-path bias voltage and the Q-path bias voltage obtained in the S1 respectively to obtain new I-path bias voltage and Q-path bias voltage; S3, fixing two bias voltages among the I-path bias voltage, the Q-path bias voltage and the P-path bias voltage cyclically and finely adjusting the other bias voltage until the I-path jitter mapping vector absolute value, the Q-path jitter mapping vector absolute value and the P-path jitter mapping vector absolute value of the IQ modulator all converge to 0; The I route jitter mapping vector : The QoS mapping vector : The P-jitter mapping vector : wherein, , are optical powers when the amplitude of the I-channel output dither vector is , A is the amplitude of the square wave signal; , are optical powers when the amplitude of the Q-channel output dither vector is , , are the projections of the I-channel dither vector mapping component in the Q-channel direction and the Q-channel dither vector mapping component in the I-channel direction, respectively; , , are the biases of the I-channel control signal, the Q-channel control signal, the P-channel control signal of the IQ modulator; , , are the I-channel half-wave voltage, the Q-channel half-wave voltage, the P-channel half-wave voltage of the IQ modulator, respectively; is the half-wave voltage of the IQ modulator.​​​ 2. The method for IQ modulator bias control based on dither vector monitoring as claimed in claim 1, wherein, The square wave signal is a random square wave sequence, and the random square wave sequence added in the S2 satisfies: wherein, is the i-th point of a random square wave array added to the I-path bias voltage point, is the i-th point of a random square wave array added to the Q-path bias voltage point, is the number of points of the random square wave sequence.

3. The method for IQ modulator bias control based on dither vector monitoring as claimed in claim 2, wherein, The amplitude of the random square wave sequence is , is the half-wave voltage of the IQ modulator, and the frequency bandwidth of the random square wave sequence is 1 kHz to 100 kHz.

4. The method for IQ modulator bias control based on dither vector monitoring as claimed in claim 1, wherein, The S3 further comprises: injecting a jitter vector signal into the I-path of the IQ modulator and calculating an I-path jitter mapping vector according to the real-time light power of the IQ modulator; injecting a jitter vector signal into the Q-path of the IQ modulator and calculating a Q-path jitter mapping vector according to the real-time light power of the IQ modulator; injecting a jitter vector signal into the I-path and the Q-path of the IQ modulator simultaneously, monitoring the I-path jitter vector mapping component and the Q-path jitter vector mapping component in the output light signal of the IQ modulator, and calculating a P-path jitter mapping vector according to the projection of the I-path jitter vector mapping component in the Q-path direction and the projection of the Q-path jitter vector mapping component in the I-path direction.

5. The method for IQ modulator bias control based on dither vector monitoring as claimed in claim 1, wherein, The S3 comprises: S31, fixing the Q-path bias voltage and the P-path bias voltage, targeting at the I-path jitter mapping vector absolute value reduction, finely adjusting the I-path bias voltage; S32, fixing the I-path bias voltage and the P-path bias voltage, targeting at the Q-path jitter mapping vector absolute value reduction, finely adjusting the Q-path bias voltage; S33, fixing the I-path bias voltage and the Q-path bias voltage, targeting at the P-path jitter mapping vector absolute value reduction, finely adjusting the P-path bias voltage; S34, repeating the S31-S33 until the I-path jitter mapping vector absolute value, the Q-path jitter mapping vector absolute value and the P-path jitter mapping vector absolute value all converge to 0.

6. The method for IQ modulator bias control based on dither vector monitoring according to claim 1 or 5, wherein, The I-path bias voltage, the Q-path bias voltage and the P-path bias voltage after each fine adjustment are respectively: in, , , The first The I-channel bias voltage, Q-channel bias voltage, and P-channel bias voltage after fine-tuning. , , For respectively the first The finely tuned I-path jitter mapping vector, Q-path jitter mapping vector, and P-path jitter mapping vector The first proportional parameter, The first integration parameter, Let be the first differential parameter. This is the second proportional parameter. For the second integral parameter, For the second differential parameter, This is the third proportional parameter. For the third integral parameter, This is the third differential parameter.

7. The method for IQ modulator bias control based on dither vector monitoring as claimed in claim 1, wherein, The S1 comprises: initializing the I-path bias voltage, the Q-path bias voltage and the P-path bias voltage to 0; fixing the P-path bias voltage, targeting at the light power of the IQ modulator tending to the target light power, alternately coarsely adjusting the I-path bias voltage and the Q-path bias voltage within the set range.

8. The method for IQ modulator bias control based on dither vector monitoring according to claim 1 or 7, wherein, The S1 further comprises: giving the target light power according to the target function of the IQ modulator; wherein the target light power is the direct current light power minimum point or the direct current light power maximum point of the IQ modulator, or is any point between the direct current light power minimum point and the direct current light power maximum point.

9. An IQ modulator bias control system based on dither vector monitoring, characterized by, Comprising: a coarse adjustment module, configured to target at the light power of the IQ modulator equaling to a target light power, coarsely adjusting the I-path bias voltage and the Q-path bias voltage applied on the IQ modulator within a set range; An adding module is configured to add square wave signals to the I-path bias voltage and the Q-path bias voltage obtained by the IQ coarse adjustment module to obtain new I-path bias voltage and Q-path bias voltage; A fine adjustment module is configured to fix two bias voltages among the I-path bias voltage, the Q-path bias voltage and the P-path bias voltage in a cycle, and fine adjust the other bias voltage until the I-path jitter mapping vector absolute value, the Q-path jitter mapping vector absolute value and the P-path jitter mapping vector absolute value of the IQ modulator all converge to 0. The I jitter mapping vector : The QoS mapping vector : The P-jitter mapping vector : wherein, , are optical powers when the amplitude of the I-channel output dither vector is , A is the amplitude of the square wave signal; , are optical powers when the amplitude of the Q-channel output dither vector is , , are the projections of the I-channel dither vector mapping component in the Q-channel direction and the Q-channel dither vector mapping component in the I-channel direction, respectively; , , are the biases of the I-channel control signal of the IQ modulator at the current moment, the bias of the Q-channel control signal of the IQ modulator, the bias of the P-channel control signal of the IQ modulator; , , , are the I-channel half-wave voltage, the Q-channel half-wave voltage and the P-channel half-wave voltage of the IQ modulator, respectively; is the half-wave voltage of the IQ modulator.​​ 10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to implement the IQ modulator bias control method based on the jitter vector monitoring according to any one of claims 1-8.

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