CN111064523B - Automatic control method and device for bias point of photoelectric modulator - Google Patents

Automatic control method and device for bias point of photoelectric modulator Download PDF

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CN111064523B
CN111064523B CN201911157665.2A CN201911157665A CN111064523B CN 111064523 B CN111064523 B CN 111064523B CN 201911157665 A CN201911157665 A CN 201911157665A CN 111064523 B CN111064523 B CN 111064523B
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bias
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modulator
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CN111064523A (en
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朱门
张会彬
李良灿
张�杰
赵永利
高文杰
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Beijing University of Posts and Telecommunications
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/564—Power control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H04B10/548—Phase or frequency modulation

Abstract

The invention provides an automatic control method and a device for a bias point of a photoelectric modulator, which are used for automatically controlling a bias working point of an IQ-MZM modulator, wherein the IQ-MZM modulator comprises an I path MZM modulator, a Q path MZM modulator and a P path phase shifter, and the method comprises the following steps: respectively superposing pilot signals of a first frequency on direct current bias voltages of an I-path MZM modulator and a Q-path MZM modulator, and superposing pilot signals of a second frequency on direct current bias voltages of a P-path phase shifter; the first frequency is twice the second frequency; and controlling the direct current bias voltage through feedback to enable a signal component of a first frequency in optical output power of the two MZM modulators and the P-path phase shifter to be a minimum value, so that bias operating points of the two MZM modulators and the P-path phase shifter are target bias operating points. The invention can realize the automatic control of the bias working point of the photoelectric modulator and reduce the cost.

Description

Automatic control method and device for bias point of photoelectric modulator
Technical Field
The invention relates to the technical field of optical communication, in particular to an automatic control method and device for a bias point of a photoelectric modulator.
Background
The IQ-MZM modulator consists of an I path MZM modulator, a Q path MZM modulator (Mach-Zehnder modulator) and a P path phase shifter, wherein the I path MZM modulator and the Q path MZM modulator are used for modulating two orthogonal phases of optical carrier signals, and the P path phase shifter is used for adjusting the phases of the two optical carrier signals. When the bias operating point control method is applied to an optical communication system, the bias operating point of the MZM modulator is easy to drift due to the influence of environmental changes, and the transmission performance and stability of the optical communication system are influenced, so that the bias operating point of the IQ-MZM modulator needs to be controlled to ensure that the modulator works in a normal working state.
The existing control method of bias working point of IQ-MZM modulator, one is time division multiplex detection harmonic signal, confirm the bias working point according to the harmonic signal, this kind of method needs to dispose first harmonic band-pass filter and second harmonic band-pass filter, the cost is higher, and can't be sensitive to the change situation of the reaction bias working point; and the other method is to superpose pilot signals with different frequencies in I, P, Q three bias voltage signals, perform ADC sampling on feedback signals output by each MZM modulator, then perform fast Fourier transform processing, and determine a bias working point by analyzing the change condition of each frequency component.
Disclosure of Invention
In view of the above, the present invention provides a method and an apparatus for automatically controlling a bias point of an optical electrical modulator, so as to solve the problem of high cost of controlling a bias operating point of an IQ-MZM modulator.
Based on the above purpose, the present invention provides an automatic control method for a bias point of a photoelectric modulator, which is used for automatically controlling a bias operating point of an IQ-MZM modulator, where the IQ-MZM modulator includes an I-path MZM modulator, a Q-path MZM modulator, and a P-path phase shifter, and the method includes:
respectively superposing pilot signals of a first frequency on direct current bias voltages of an I-path MZM modulator and a Q-path MZM modulator, and superposing pilot signals of a second frequency on direct current bias voltages of a P-path phase shifter; the first frequency is twice the second frequency;
and controlling the direct-current bias voltage through feedback to enable the signal component of the first frequency in the optical output power of the two MZM modulators and the optical output power of the P-path phase shifter to be a minimum value, so that the bias operating points of the two MZM modulators are target bias operating points.
Optionally, the feedback-controlling the dc bias voltage to make the signal component of the first frequency in the optical output powers of the two MZM modulators and the P-path phase shifter be a minimum value includes: and controlling the direct current bias voltage by using a PID control method so that the signal component of the first frequency in the optical output power of the two MZM modulators and the P-path phase shifter is minimum.
Optionally, a bandpass filter with a center frequency of the first frequency is used to obtain the signal component of the first frequency in the optical output power.
Optionally, the method further includes: detecting whether bias working points of the two MZM modulators and the P-path phase shifter drift or not;
and if the drift occurs, correcting the bias working point by using the PID control method so as to correct the drift bias working point to the target bias working point.
Optionally, the method for detecting whether the bias operating points of the two MZM modulators and the P-way phase shifter drift is to determine whether output signals of the two MZM modulators and the P-way phase shifter exceed a drift threshold, and if the output signals exceed the drift threshold, determine that the bias operating points of the MZM modulators and/or the P-way phase shifter drift.
Optionally, the method for correcting the bias operating point by using the PID control method to correct the shifted bias operating point to the target bias operating point is that the PID control method controls the magnitude of the dc bias voltage, so that the signal component of the first frequency in the output optical power of the MZM modulator and/or the P-path phase shifter is minimized, and the adjusted dc bias voltage corresponds to the target bias operating point.
The embodiment of the present invention further provides an automatic control device for a bias point of a photoelectric modulator, configured to automatically control a bias working point of an IQ-MZM modulator, where the IQ-MZM modulator includes an I-path MZM modulator, a Q-path MZM modulator, and a P-path phase shifter, and the automatic control device includes:
the superposed signal determining module is used for superposing pilot signals of a first frequency on direct current bias voltages of the I path MZM modulator and the Q path MZM modulator respectively and superposing pilot signals of a second frequency on direct current bias voltages of the P path phase shifter; the first frequency is twice the second frequency;
and the feedback control module is used for controlling a direct-current bias voltage in a feedback manner to enable a signal component of a first frequency in optical output power of the two MZM modulators and the P-path phase shifter to be a minimum value, so that bias operating points of the two MZM modulators and the P-path phase shifter are target bias operating points.
Optionally, the feedback control module is configured to control the dc bias voltage by using a PID controller, so that a signal component of the first frequency in the optical output powers of the two MZM modulators and the P-way phase shifter is a minimum value.
Optionally, a bandpass filter with a center frequency of the first frequency is used to obtain the signal component of the first frequency in the optical output power.
Optionally, the apparatus further comprises: the detection module is used for detecting whether bias working points of the two MZM modulators and the P-path phase shifter drift or not;
and the correction module is used for correcting the bias working point by utilizing the PID controller when the detection module judges that the bias working point sends drift so as to correct the drift bias working point to the target bias working point.
It can be seen from the above that, the method and apparatus for automatically controlling the bias point of the electro-optical modulator provided by the present invention includes superimposing the pilot signal of the first frequency on the dc bias voltages of the I-path MZM modulator and the Q-path MZM modulator, and superimposing the pilot signal of the second frequency on the dc bias voltage of the P-path phase shifter; the first frequency is twice the second frequency; and controlling the direct current bias voltage through feedback to enable a signal component of a first frequency in optical output power of the two MZM modulators and the P-path phase shifter to be a minimum value, so that bias operating points of the two MZM modulators and the P-path phase shifter are target bias operating points. The invention can realize the automatic control of the bias working point of the photoelectric modulator, reduce the system cost and is particularly suitable for an optical communication system based on the OFDM technology.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic flow chart of a method according to an embodiment of the present invention;
FIG. 2 is a diagram illustrating the relationship between the harmonic component and the bias operating point according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of an apparatus according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a system configuration according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.
It is to be noted that technical terms or scientific terms used in the embodiments of the present invention should have the ordinary meanings as understood by those having ordinary skill in the art to which the present disclosure belongs, unless otherwise defined. The use of "first," "second," and similar terms in this disclosure is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
FIG. 1 is a schematic flow chart of a method according to an embodiment of the present invention. As shown in the figure, the method for automatically controlling the bias point of the electro-optical modulator provided in the embodiment of the present invention is used for automatically controlling the bias operating point of an IQ-MZM modulator, where the IQ-MZM modulator includes two MZM modulators of I path and Q path and a P path phase shifter, and the method includes:
s101: respectively superposing pilot signals of a first frequency on direct current bias voltages of an I-path MZM modulator and a Q-path MZM modulator, and superposing pilot signals of a second frequency on direct current bias voltages of a P-path phase shifter; the first frequency is twice the second frequency;
s102: and controlling the direct-current bias voltage through feedback to enable the signal component of the first frequency in the optical output power of the two MZM modulators and the P-path phase shifter to be the minimum value, and ensuring that the bias working points of the two MZM modulators and the P-path phase shifter are the target bias working points.
In the embodiment of the present invention, a method for determining a bias operating point of an MZM modulator includes:
when a pilot signal is superimposed on the dc bias voltage of the MZM modulator, the frequency of the pilot signal is 1kHz, and the amplitude of the pilot signal is 5% of the rf signal (the signal to be modulated input by the rf signal input terminal of the MZM modulator), the output optical power of the MZM modulator can be expressed as:
Figure BDA0002285238910000041
wherein, PinIs the optical power, T, input to the MZM modulatorDIs the insertion loss of the MZM modulator,
Figure BDA0002285238910000042
is the phase shift caused by the dc bias voltage,
Figure BDA0002285238910000043
is the phase offset caused by the pilot signal;
Figure BDA0002285238910000051
Figure BDA0002285238910000052
wherein A is a pilot signalAmplitude, ω being the angular frequency, V, of the pilot signalπAnd (omega) refers to the half-wave voltage of the MZM modulator as a function of frequency. VDCIs the dc component of the bias voltage, i.e. the dc bias voltage,
Figure BDA0002285238910000053
is the phase of the dc bias voltage relative to the half-wave voltage.
Order to
Figure BDA0002285238910000054
Then:
Figure BDA0002285238910000055
taylor expansion:
Figure BDA0002285238910000056
therefore, after passing through the photo detector PD with responsivity η, the first harmonic in the generated current signal can be expressed as:
Figure BDA0002285238910000057
the second harmonic can be expressed as:
Figure BDA0002285238910000058
Figure BDA0002285238910000059
r is the amplitude ratio of the first harmonic to the second harmonic, TdIs the insertion loss of the MZM modulator.
Fig. 2 is a schematic diagram of a relationship between a harmonic component and a bias operating point according to an embodiment of the present invention. As shown in the figure, according to the derivation, waveform diagrams of the first harmonic component and the second harmonic component can be obtained, when the bias working point of the MZM modulator is a NULL point or a Peak point, the first harmonic reaches a minimum value, and the second harmonic reaches a maximum value; when the bias operating point of the MZM modulator is at a + Quad point or a-Quad point, the first harmonic reaches a maximum value, and the second harmonic reaches a minimum value, so that the position of the bias operating point of the MZM modulator can be determined by detecting the amplitudes of the first harmonic, the second harmonic and the direct-current bias voltage signal. For an I-path MZM modulator, a Q-path MZM modulator and a P-path phase shifter, the corresponding bias working point position can be determined by utilizing the amplitudes of the corresponding primary harmonic, secondary harmonic and direct-current bias voltage signals of each path, wherein when the bias working point of the P-path phase shifter is at an orthogonal point (+ Quad point or-Quad point), the P-path phase shifter works in a stable state.
In one application scenario, when an IQ-MZM modulator is applied in an optical communication system based on an OFDM (Orthogonal Frequency Division Multiplexing) technique, the bias operating point of an I-path MZM modulator is required to be at Null point, the bias operating point of a Q-path MZM modulator is required to be at Null point, and the bias operating point of a P-path phase shifter is required to be at Orthogonal point (+ Quad point or-Quad point). Therefore, for the I-path MZM modulator and the Q-path MZM modulator, when the first harmonic amplitude reaches the minimum value and the second harmonic amplitude reaches the maximum value, the bias working points of the I-path MZM modulator and the Q-path MZM modulator are NULL points (or Peak points, which can be determined by combining the output optical power, if the output optical power is close to the minimum value, the bias working points are NULL points, and if the output optical power is close to the maximum value, the bias working points are Peak points), that is, when the first harmonic amplitude reaches the minimum value and the second harmonic amplitude reaches the maximum value, the I-path MZM modulator and the Q-path MZM modulator work in the optimum stable state; for the P phase shifter, when the amplitude of the first harmonic reaches the maximum value and the amplitude of the second harmonic reaches the minimum value, the bias working point of the P phase shifter is at the Quad point, namely when the amplitude of the first harmonic reaches the maximum value and the amplitude of the second harmonic reaches the minimum value, the P phase shifter works in the optimal stable state.
In the embodiment of the invention, a first pilot signal is superposed on the direct current bias voltage of an I-path MZM modulator, a second pilot signal is superposed on the direct current bias voltage of a Q-path MZM modulator, a third pilot signal is superposed on the direct current bias voltage of a P-path phase shifter, the frequencies of the first pilot signal and the second pilot signal are both first frequencies, the frequency of the third pilot signal is second frequency, and the first frequency is twice the second frequency.
When determining the target bias operating point of the MZM modulator based on the relationship between the first harmonic and the second harmonic shown in fig. 2 and the optical output power of the MZM modulator, it may be determined whether the modulator operates at the target bias operating point according to the amplitude of the signal component (first harmonic component) of the first frequency in the optical output power of the MZM modulator; that is, when the signal component of the first frequency in the optical output power of the MZM modulator reaches the minimum value, the bias operating point of the MZM modulator is determined to be the target bias operating point.
In some embodiments, the signal component of the first frequency in the optical output power is obtained by performing filtering processing using a band-pass filter whose center frequency is the first frequency.
In this embodiment of the present invention, in step S102, the direct current bias voltage is feedback-controlled to make the signal component of the first frequency in the optical output powers of the two MZM modulators and the P-way phase shifter be the minimum value, and the direct current bias voltage may be controlled by using a PID control (proportional-integral-derivative control) method to make the signal component of the first frequency in the optical output powers of the two MZM modulators and the P-way phase shifter be the minimum value.
The PID control method of the PID controller comprises the following steps: let r (t) be the target value, i.e. the target minimum value of the signal component of the first frequency; y (t) is the actual value, i.e. the value of the received signal component of the current first frequency; a control deviation e (t) r (t) -y (t) which is a target value and an actual value; the proportional coefficient of the PID controller is Kp, the integral time is Ti, the integral coefficient is Ki Kp T/Ti, the differential time is Td, the differential coefficient is Kp Td/T, T is the sampling period of the received signal, and the output value of the PID controller is:
Figure BDA0002285238910000071
wherein k isAnd at the sampling moment, taking an integer. u. ofkFor the calculated output value at the kth sampling instant, ekControl deviation value input for kth sampling time, ek-1The control deviation value input for the (k-1) th sampling moment. According to the formula (9), the control deviation e at the previous timekE from the current timek-1Calculating and outputting the DC bias voltage value uk。
In an embodiment, for the I-path MZM modulator, the pilot signal S1 with the first frequency is superimposed on the dc bias voltage Vdc1 of the I-path MZM modulator, and at the same time, the magnitude of the dc bias voltage Vdc1 is controlled by the I-path PID control method, so that the signal component with the first frequency in the output optical power of the I-path MZM modulator is the minimum, and the dc bias voltage Vdc1 at this time corresponds to the target bias operating point of the I-path MZM modulator.
For the Q-path MZM modulator, a pilot signal S2 with a first frequency is superimposed on the dc bias voltage Vdc2 of the Q-path MZM modulator, and at the same time, the magnitude of the dc bias voltage Vdc2 is controlled by the Q-path PID control method, so that the signal component with the first frequency in the output optical power of the Q-path MZM modulator is the minimum, and the dc bias voltage Vdc2 at this time corresponds to the target bias operating point of the Q-path MZM modulator. Alternatively, the pilot signal S1 and the pilot signal S2 may be the same signal.
For the P-path phase shifter, the pilot signal S3 of the second frequency is superimposed on the dc bias voltage Vdc3 of the P-path phase shifter, and meanwhile, the magnitude of the dc bias voltage Vdc3 is controlled by the P-path PID control method, so that the signal component of the first frequency in the output optical power of the P-path phase shifter is the minimum, and the dc bias voltage Vdc3 at this time corresponds to the target bias operating point of the P-path phase shifter. The embodiment of the invention realizes the feedback adjustment of the bias working point by a PID control method, and can enable the MZM modulator to quickly and accurately reach the working stable state. In the embodiment of the present invention, the method for automatically controlling the bias point of the optoelectronic modulator further includes:
and detecting whether the bias working points of the two MZM modulators and the P-path phase shifter drift or not, and if so, correcting the bias working points by using a PID control method so as to correct the drifting bias working points to target bias working points.
Optionally, taking the I-path MZM modulator as an example, the pilot signal S1 is superimposed on the dc bias voltage of the I-path MZM modulator, and is used to detect whether the output signal of the I-path MZM modulator exceeds a drift threshold, and if the output signal exceeds the drift threshold, it is determined that the bias operating point of the I-path MZM modulator drifts, and at this time, the magnitude of the dc bias voltage Vdc1 is controlled by the I-path PID control method, so that the signal component of the first frequency in the output optical power of the I-path MZM modulator is minimum, and the adjusted dc bias voltage Vdc1 corresponds to the target bias operating point of the I-path MZM modulator. The method for correcting the bias working points of the Q-path MZM modulator and the P-path phase shifter is the same as that of the I-path MZM modulator, and repeated description is not provided in the invention.
Fig. 3 is a schematic structural diagram of an apparatus according to an embodiment of the present invention. As shown in the figure, the automatic control device for bias point of the optoelectronic modulator of the embodiment of the invention comprises:
the superposed signal determining module is used for superposing pilot signals of a first frequency on direct current bias voltages of the I path MZM modulator and the Q path MZM modulator respectively and superposing pilot signals of a second frequency on direct current bias voltages of the P path phase shifter; the first frequency is twice the second frequency;
and the feedback control module is used for controlling the direct-current bias voltage in a feedback manner to enable the signal component of the first frequency in the optical output power of the two MZM modulators and the optical output power of the P-path phase shifter to be the minimum value, and ensuring that the bias working points of the two MZM modulators and the P-path phase shifter are the target bias working points.
In some embodiments, the feedback control module is configured to control the dc bias voltage by using a PID control method so that a signal component of the first frequency in the optical output power of the two MZM modulators and the P-way phase shifter is a minimum value.
Optionally, a bandpass filter with a center frequency of the first frequency is used to obtain the signal component of the first frequency in the optical output power.
In some embodiments, the apparatus for automatically controlling the bias point of the electro-optical modulator further comprises:
the detection module is used for detecting whether bias working points of the two MZM modulators and the P-path phase shifter drift or not;
and the correction module is used for correcting the bias working point by utilizing a PID control method when the detection module judges that the bias working point sends drift so as to correct the drift bias working point to a target bias working point.
The apparatus of the foregoing embodiment is used to implement the corresponding method in the foregoing embodiment, and has the beneficial effects of the corresponding method embodiment, which are not described herein again.
Fig. 4 is a schematic structural diagram of a system according to an embodiment of the present invention. As shown in the figure, the system for automatically controlling the bias point of the electro-optical modulator provided by the embodiment of the present invention includes an IQ-MZM modulator, an optical splitter, a photodetector PD, a band pass filter, and I, Q, P three PID controllers. Direct current bias voltage and superposed pilot signals are respectively applied to an I-path MZM modulator, a Q-path MZM modulator and a P-path phase shifter of the IQ-MZM modulator, wherein a first pilot signal S1 with a first frequency is superposed on the direct current bias voltage Vdc1 of the I-path MZM modulator, a second pilot signal with the first frequency is superposed on the direct current bias voltage Vdc2 of the Q-path MZM modulator, and a third pilot signal S3 with a second frequency is superposed on the direct current bias voltage Vdc3 of the P-path phase shifter; an optical signal output by the IQ-MZM modulator is divided into one path by an optical splitter and enters a photoelectric detector, the photoelectric detector converts the optical signal into an electric signal, the electric signal is amplified by an amplifying circuit and then is filtered by a band-pass filter with the center frequency being a first frequency, the filtered signal is converted into a digital signal by an analog-to-digital conversion unit (ADC), and the digital signal sampled by the ADC is correspondingly input into three PID controllers for feedback control; the three PID controllers are used for respectively controlling the magnitude of the corresponding direct current bias voltage, so that the signal component of the first frequency in the output optical power of the corresponding MZM modulator is minimum, the adjusted direct current bias voltage corresponds to the target bias working point of the MZM modulator, the automatic control process of the bias working point of the IQ-MZM modulator is realized, the system cost can be reduced due to the fact that only one band-pass filter is used, the PID controllers are used for realizing feedback control adjustment of the bias working point, the bias working point can be quickly adjusted to the target bias working point, and the MZM modulator is guaranteed to work in a stable state.
Fig. 5 is a schematic diagram illustrating a more specific hardware structure of an electronic device according to this embodiment, where the electronic device may include: a processor 1010, a memory 1020, an input/output interface 1030, a communication interface 1040, and a bus 1050. Wherein the processor 1010, memory 1020, input/output interface 1030, and communication interface 1040 are communicatively coupled to each other within the device via bus 1050.
The processor 1010 may be implemented by a general-purpose CPU (Central Processing Unit), a microprocessor, an Application Specific Integrated Circuit (ASIC), or one or more Integrated circuits, and is configured to execute related programs to implement the technical solutions provided in the embodiments of the present disclosure.
The Memory 1020 may be implemented in the form of a ROM (Read Only Memory), a RAM (Random Access Memory), a static storage device, a dynamic storage device, or the like. The memory 1020 may store an operating system and other application programs, and when the technical solution provided by the embodiments of the present specification is implemented by software or firmware, the relevant program codes are stored in the memory 1020 and called to be executed by the processor 1010.
The input/output interface 1030 is used for connecting an input/output module to input and output information. The i/o module may be configured as a component in a device (not shown) or may be external to the device to provide a corresponding function. The input devices may include a keyboard, a mouse, a touch screen, a microphone, various sensors, etc., and the output devices may include a display, a speaker, a vibrator, an indicator light, etc.
The communication interface 1040 is used for connecting a communication module (not shown in the drawings) to implement communication interaction between the present apparatus and other apparatuses. The communication module can realize communication in a wired mode (such as USB, network cable and the like) and also can realize communication in a wireless mode (such as mobile network, WIFI, Bluetooth and the like).
Bus 1050 includes a path that transfers information between various components of the device, such as processor 1010, memory 1020, input/output interface 1030, and communication interface 1040.
It should be noted that although the above-mentioned device only shows the processor 1010, the memory 1020, the input/output interface 1030, the communication interface 1040 and the bus 1050, in a specific implementation, the device may also include other components necessary for normal operation. In addition, those skilled in the art will appreciate that the above-described apparatus may also include only those components necessary to implement the embodiments of the present description, and not necessarily all of the components shown in the figures.
Computer-readable media of the present embodiments, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), Digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information that can be accessed by a computing device.
Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, is limited to these examples; within the idea of the invention, also features in the above embodiments or in different embodiments may be combined, steps may be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.
In addition, well known power/ground connections to Integrated Circuit (IC) chips and other components may or may not be shown within the provided figures for simplicity of illustration and discussion, and so as not to obscure the invention. Furthermore, devices may be shown in block diagram form in order to avoid obscuring the invention, and also in view of the fact that specifics with respect to implementation of such block diagram devices are highly dependent upon the platform within which the present invention is to be implemented (i.e., specifics should be well within purview of one skilled in the art). Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the invention, it should be apparent to one skilled in the art that the invention can be practiced without, or with variation of, these specific details. Accordingly, the description is to be regarded as illustrative instead of restrictive.
While the present invention has been described in conjunction with specific embodiments thereof, many alternatives, modifications, and variations of these embodiments will be apparent to those of ordinary skill in the art in light of the foregoing description. For example, other memory architectures (e.g., dynamic ram (dram)) may use the discussed embodiments.
The embodiments of the invention are intended to embrace all such alternatives, modifications and variances that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, substitutions, improvements and the like that may be made without departing from the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (6)

1. An automatic control method for bias points of an optical-electrical modulator, which is used for automatically controlling bias working points of an IQ-MZM modulator, wherein the IQ-MZM modulator comprises an I-path MZM modulator, a Q-path MZM modulator and a P-path phase shifter, and the method comprises the following steps:
respectively superposing pilot signals of a first frequency on direct current bias voltages of an I-path MZM modulator and a Q-path MZM modulator, and superposing pilot signals of a second frequency on direct current bias voltages of a P-path phase shifter; the first frequency is twice the second frequency;
controlling the direct-current bias voltage by using a PID control method to enable the signal component of the first frequency in the optical output power of the two MZM modulators and the optical output power of the P-path phase shifter to be a minimum value, so that the bias working points of the two MZM modulators are target bias working points;
the PID control method comprises the following steps: let r (t) be the target minimum of signal components at the first frequency; y (t) is the value of the received signal component of the current first frequency; a control deviation e (t) from the target minimum value and the value of the signal component of the current first frequency is r (t) -y (t); the proportional coefficient of the PID controller is Kp, the integral time is Ti, the integral coefficient is Ki Kp T/Ti, the differential time is Td, the differential coefficient is Kp Td/T, T is the sampling period of the received signal, and at the k sampling time, the DC offset voltage value u output by the PID controllerkComprises the following steps:
Figure FDA0003108306910000011
wherein e iskControl deviation value input for kth sampling time, ek-1The control deviation value input at the kth-1 sampling moment is j is an integer;
the method further comprises the following steps: detecting whether bias working points of the two MZM modulators and the P-path phase shifter drift or not;
and if the drift occurs, correcting the bias working point by using the PID control method so as to correct the drift bias working point to the target bias working point.
2. The method of claim 1, wherein the signal component of the first frequency in the optical output power is obtained using a band pass filter centered at the first frequency.
3. The method of claim 1, wherein the method for detecting whether the bias operating points of the two MZM modulators and the P-way phase shifter are shifted is to determine whether the output signals of the two MZM modulators and the P-way phase shifter exceed a shift threshold value, and if the output signals of the two MZM modulators and the P-way phase shifter exceed the shift threshold value, it is determined that the bias operating points of the MZM modulators and/or the P-way phase shifter are shifted.
4. The method according to claim 3, wherein the step of correcting the bias operating point by the PID control method to correct the shifted bias operating point to the target bias operating point is to control the magnitude of the DC bias voltage by the PID control method so that the signal component of the first frequency in the output optical power of the MZM modulator and/or the P-way phase shifter is minimized and the adjusted DC bias voltage corresponds to the target bias operating point.
5. An automatic control device for bias point of an optical-electrical modulator, which is used for automatically controlling the bias working point of an IQ-MZM modulator, wherein the IQ-MZM modulator comprises an I-path MZM modulator, a Q-path MZM modulator and a P-path phase shifter, and the automatic control device comprises:
the superposed signal determining module is used for superposing pilot signals of a first frequency on direct current bias voltages of the I path MZM modulator and the Q path MZM modulator respectively and superposing pilot signals of a second frequency on direct current bias voltages of the P path phase shifter; the first frequency is twice the second frequency;
a feedback control module, configured to control a dc bias voltage by using a PID controller, so that a signal component of a first frequency in optical output powers of the two MZM modulators and the P-way phase shifter is a minimum value, and a bias operating point of the two MZM modulators and the P-way phase shifter is a target bias operating point;
let r (t) be the target minimum of signal components at the first frequency; y (t) is the value of the received signal component of the current first frequency; a control deviation e (t) from the target minimum value and the value of the signal component of the current first frequency is r (t) -y (t); the proportional coefficient of the PID controller is Kp, the integral time is Ti, the integral coefficient is Ki Kp T/Ti, the differential time is Td, the differential coefficient is Kp Td/T, T is the sampling period of the received signal, and at the k-th sampling time, the direct current bias voltage value u output by the PID controllerkComprises the following steps:
Figure FDA0003108306910000021
wherein e iskControl deviation value input for kth sampling time, ek-1The control deviation value input at the kth-1 sampling moment is j is an integer;
the detection module is used for detecting whether bias working points of the two MZM modulators and the P-path phase shifter drift or not;
and the correction module is used for correcting the bias working point by utilizing the PID controller when the detection module judges that the bias working point sends drift so as to correct the drift bias working point to the target bias working point.
6. The apparatus of claim 5 wherein the signal component of the first frequency in the optical output power is obtained using a band pass filter centered at the first frequency.
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