Laser communication terminal and control method

Abstract

This disclosure relates to a laser communication terminal and control method. The laser communication terminal includes: a laser configured to output an optical carrier; a dual-parallel Mach-Zehnder modulator configured to receive a pilot signal and the optical carrier and output a modulated optical signal; a photoelectric conversion unit configured to convert the modulated optical signal into an electrical signal; a pilot signal generation unit configured to generate a pilot signal; and a bias control unit configured to determine a correlation value between the electrical signal and the pilot signal as an error signal, and to adjust the bias voltage of the dual-parallel Mach-Zehnder modulator based on the error signal. The solution of this disclosure can significantly save resources used for computation.

Description

Technical Field

[0001] The embodiments disclosed herein relate generally to the field of laser communication technology, and more specifically to a laser communication terminal and control method. Background Technology

[0002] The transmitting unit of the spaceborne laser communication terminal involves a dual parallel Mach-Zehnder modulator (DPMZM). However, due to the influence of the internal waveguide structure and materials of the DPMZM, mechanical vibration, the polarization state of light, and environmental temperature and humidity, the bias voltage of the modulator will slowly drift, which will greatly affect its operating characteristics.

[0003] To address these challenges, automatic feedback control of the bias voltage of the DPMZM is typically employed. This involves using Fast Fourier Transform (FFT) to extract harmonics. However, FFT has high computational complexity and consumes significant resources. Summary of the Invention

[0004] To address the aforementioned issues, this disclosure provides a laser communication terminal and control method that can significantly save resources when controlling the bias voltage of a dual parallel Mach-Zehnder modulator.

[0005] According to one aspect of this disclosure, a laser communication terminal is provided. The laser communication terminal includes: a laser configured to output an optical carrier; a dual parallel Mach-Zehnder modulator configured to receive a pilot signal and the optical carrier and output a modulated optical signal; a photoelectric conversion unit configured to convert the modulated optical signal into an electrical signal; a pilot signal generation unit configured to generate a pilot signal; and a bias control unit configured to determine a correlation value between the electrical signal and the pilot signal as an error signal, and to adjust a bias voltage relative to the dual parallel Mach-Zehnder modulator based on the error signal.

[0006] In some embodiments, the bias control unit includes: a multiplier configured to perform multiplication operations on corresponding elements of the electrical signal and the pilot signal to determine a multiplication result corresponding to each element; and an adder configured to accumulate the multiplication results corresponding to each element to determine the correlation value.

[0007] In some embodiments, the number of multipliers is equal to the number of elements, and each multiplier corresponds to one element to determine the multiplication result corresponding to each element.

[0008] In some embodiments, the number of multipliers is one, and the multiplier is configured to be time-division multiplexed to sequentially determine the multiplication result corresponding to each element.

[0009] In some embodiments, the dual parallel Mach-Zehnder modulator includes a first branch and a second branch connected in parallel. The first branch includes a first sub-Mach-Zehnder modulator, and the second branch includes a second sub-Mach-Zehnder modulator and a phase modulator connected in series.

[0010] According to a second aspect of this disclosure, a method for controlling a laser communication terminal, the laser communication terminal being the laser communication terminal of the first aspect of this disclosure, the method comprising: determining a correlation value between an electrical signal and a pilot signal with respect to an optical carrier to serve as an error signal; and adjusting a bias voltage with respect to a dual parallel Mach-Zehnder modulator based on the error signal.

[0011] In some embodiments, the method further includes: determining the maximum point of optical power, the minimum point of optical power, and the half-wave voltage corresponding to the dual parallel Mach-Zehnder modulator; determining the scanning range of the bias voltage of the dual parallel Mach-Zehnder modulator based on the maximum point of optical power, the minimum point of optical power, and the half-wave voltage; and scanning the bias voltage of the dual parallel Mach-Zehnder modulator within the scanning range at a first predetermined step size during a coarse scanning stage.

[0012] In some embodiments, the method further includes: determining a first voltage corresponding to the intermediate power value of the dual parallel Mach-Zehnder modulator; controlling the pilot signal generation unit to provide first pilot signals to the I-path and Q-path respectively; determining the error signal during the fine scanning stage; and adjusting the bias voltage of the dual parallel Mach-Zehnder modulator based on the error signal and a second predetermined step size, with the first voltage as the initial value, the second predetermined step size being smaller than the first predetermined step size.

[0013] In some embodiments, adjusting the bias voltage of the dual parallel Mach-Zehnder modulator based on the error signal and a second predetermined step size, using the first voltage as an initial value, includes: maintaining the adjustment direction of the bias voltage of the dual parallel Mach-Zehnder modulator in response to determining that the error signal is positive; and determining that the current bias voltage is closer to the optimal operating point of the dual parallel Mach-Zehnder modulator in response to determining that the current error signal is greater than the error signal corresponding to the previous scan operation.

[0014] In some embodiments, the method further includes: setting the bias voltages for the Q-path and the P-path to zero, and scanning the bias voltages for the I-path to determine the maximum point of optical power, the minimum point of optical power, and a first voltage.

[0015] In some embodiments, the method further includes: determining a second voltage corresponding to the minimum point of optical power; controlling the pilot signal generation unit to provide a first pilot signal to the I-path; determining the error signal during a fine scanning phase of the bias voltage of the I-path; and adjusting the bias voltage of the I-path based on the properties of the error signal and a second predetermined step size, using the second voltage as an initial value.

[0016] In some embodiments, adjusting the bias voltage with respect to the I-path based on the properties of the error signal and a second predetermined step size, using the second voltage as an initial value, includes: decreasing the bias voltage with respect to the I-path in response to determining that the error signal is a positive value; and increasing the bias voltage with respect to the I-path in response to determining that the error signal is a negative value.

[0017] In some embodiments, the method further includes: setting the bias voltages for the I-path and the Q-path to the bias voltages corresponding to the maximum point of optical power; scanning the bias voltages for the P-path to determine a third voltage corresponding to the intermediate power value for the P-path; controlling the pilot signal generation unit to provide a first pilot signal to the I-path and a second pilot signal to the Q-path, the first pilot signal and the second pilot signal being orthogonal; determining the error signal during a fine scanning phase of the bias voltages for the P-path; and adjusting the bias voltages for the P-path based on the properties of the error signal and a second predetermined step size, using the third voltage as an initial value.

[0018] According to the technical solution of this disclosure, the laser communication terminal includes: a laser configured to output an optical carrier; a dual parallel Mach-Zehnder modulator configured to receive a pilot signal and the optical carrier and output a modulated optical signal; a photoelectric conversion unit configured to convert the modulated optical signal into an electrical signal; a pilot signal generation unit configured to generate a pilot signal; and a bias control unit configured to determine the correlation value between the electrical signal and the pilot signal as an error signal, and to adjust the bias voltage of the dual parallel Mach-Zehnder modulator according to the error signal. The technical solution of this disclosure obtains the error signal by calculating the correlation value between the electrical signal and the pilot signal, which can significantly save resources used for computation.

[0019] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0020] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. In the drawings, the same or similar reference numerals denote the same or similar elements.

[0021] Figure 1A block diagram of a laser communication terminal according to an embodiment of the present disclosure is shown.

[0022] Figure 2 A block diagram of a bias control unit according to an embodiment of the present disclosure is shown.

[0023] Figure 3 A flowchart of the method for controlling a laser communication terminal disclosed herein is shown.

[0024] Figure 4 A flowchart illustrating a method for controlling a laser communication terminal according to an embodiment of the present disclosure is shown.

[0025] Figure 5 A schematic block diagram of an example electronic device for controlling a laser communication terminal, which can be used to implement embodiments of the present disclosure, is shown. Detailed Implementation

[0026] The exemplary embodiments of this disclosure are described below with reference to the accompanying drawings, including various details of the embodiments to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this disclosure. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0027] The term "comprising" and its variations as used herein signify open inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "one example embodiment" and "one embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc., may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0028] As described above, when performing automatic feedback control of the bias voltage of the DPMZM in a laser communication terminal, the Fast Fourier Transform (FFT) is used to extract harmonics. The FFT has high computational complexity and consumes a lot of resources.

[0029] For example, automatic bias control schemes for DPMZM generally employ two main categories: DC power monitoring and pilot methods. The first is the DC power detection method, which identifies the DC component in the electrical signal detected by the detector and uses feedback compensation voltage to ensure the DC portion is unrestricted, thereby locking the DC bias point. The second is the pilot method, which superimposes a low-frequency, small-amplitude pilot signal onto the data signal and determines the bias point state by detecting the harmonic components of this pilot signal in the modulated output optical signal. The technical solution described in patent document CN118157766A uses Fast Fourier Transform (FFT) to extract harmonics.

[0030] It is worth noting that FFT, as a global spectrum analysis tool, has limitations: FFT has a computational complexity of O(N log N), requiring a large number of data points to ensure spectral resolution. The massive data buffer and complex butterfly operations place a heavy burden on the digital signal processing (DSP) resources of onboard equipment and introduce significant processing latency, making it difficult to meet the urgent need for fast real-time control in satellite laser communication. Furthermore, in low signal-to-noise ratio or strong interference environments onboard, weak pilot harmonic components in the FFT spectrum are easily submerged by background noise, leading to detection failure and decreased system stability.

[0031] To at least partially address one or more of the aforementioned problems and other potential issues, exemplary embodiments of this disclosure provide a laser communication terminal and control method. In the technical solution of this disclosure, the laser communication terminal includes: a laser configured to output an optical carrier; a dual-parallel Mach-Zehnder modulator configured to receive a pilot signal and the optical carrier and output a modulated optical signal; a photoelectric conversion unit configured to convert the modulated optical signal into an electrical signal; a pilot signal generation unit configured to generate a pilot signal; and a bias control unit configured to determine a correlation value between the electrical signal and the pilot signal as an error signal, and to adjust the bias voltage of the dual-parallel Mach-Zehnder modulator based on the error signal. The technical solution of this disclosure obtains the error signal by calculating the correlation value between the electrical signal and the pilot signal, which can significantly save resources used for computation.

[0032] The following description, in conjunction with the accompanying drawings, describes the embodiments of this disclosure.

[0033] Figure 1A block diagram of a laser communication terminal 100 according to an embodiment of the present disclosure is shown. It should be understood that the laser communication terminal 100 may also include other components. The laser communication terminal 100 includes, for example, a laser 102, a dual parallel Mach-Zehnder modulator 104, a photoelectric conversion unit 106, a pilot signal generation unit 108, and a bias control unit 110. In some embodiments, the laser communication terminal 100 may further include, for example, a driving unit 112, which is disposed, for example, between the pilot signal generation unit 108 and the dual parallel Mach-Zehnder modulator 104.

[0034] Regarding laser 102, it is configured, for example, to output an optical carrier.

[0035] Regarding the dual parallel Mach-Zehnder modulator 104, it is configured, for example, to receive a pilot signal and an optical carrier and output a modulated optical signal.

[0036] A dual parallel Mach-Zehnder modulator (DPMZM) includes, for example, a first branch and a second branch connected in parallel. The first branch includes a first sub-Mach-Zehnder modulator 141, and the second branch includes a second sub-Mach-Zehnder modulator 142 connected in series and a phase modulator 143.

[0037] Regarding the photoelectric conversion unit 106, it is configured, for example, to convert a modulated optical signal into an electrical signal. The photoelectric conversion unit 106 includes, for example, a beam splitter 161 and a photodetector 162. The beam splitter 161 is, for example, a 10:90 beam splitter, wherein after the modulated optical signal passes through the beam splitter 161, 10% of the modulated optical signal is converted into an electrical signal by the photodetector 162. For example, this modulated optical signal is converted into a photocurrent by the photodetector, then converted into a digital signal by an analog-to-digital converter before entering the bias control unit 110. The other path (i.e., the remaining 90% of the modulated optical signal) can be used for subsequent signal transmission, testing, or signal processing.

[0038] Regarding the pilot signal generation unit 108, it is configured, for example, to generate pilot signals.

[0039] Regarding the bias control unit 110, it is configured, for example, to determine the correlation value between the electrical signal and the pilot signal as an error signal, and to adjust the bias voltage with respect to the dual parallel Mach-Zehnder modulator 104 based on the error signal.

[0040] Figure 2A block diagram of a bias control unit 110 according to an embodiment of the present disclosure is shown. The bias control unit 110 includes, for example, a TIA (transimpedance amplifier), an operational amplifier, an ADC (analog-to-digital converter), a correlation calculation unit 111, and a DAC (digital-to-analog converter). The correlation calculation unit 111 is used to perform correlation operations. The correlation calculation unit 111 includes, for example, a multiplier and an adder. After the modulated optical signal passes through the TIA, operational amplifier, and ADC, correlation calculation is performed between the modulated optical signal and the pilot signal in the correlation calculation unit 111. When performing correlation calculation, the correlation calculation unit 111 uses, for example, a multiplication and accumulation operation on the sampled digital signal using a multiplier and an adder to obtain the correlation value. The correlation operation can be implemented, for example, with reference to the following formula (1): (1) in, The digital sample value (e.g., represented by a binary number) characterizes the electrical signal obtained by converting the modulated optical signal to be detected. The digital sample value (e.g., represented by a binary number) represents the preset desired pilot signal. It should be noted that n∈[0,N-1], that is, the electrical signal converted from the modulated optical signal is represented by an N-bit binary number, and the pilot signal is also represented by an N-bit binary number. This represents the cross-correlation value between the input electrical signal to be detected and the desired frequency signal. The core function of cross-correlation operation is to measure the similarity between the two signals. The larger the cross-correlation result, the higher the similarity between the electrical signal to be detected and the pilot signal, which means that the transmission quality of the modulated optical signal is better and the system operating point is closer to the ideal state.

[0041] The calculated correlation values ​​can be used as error signals for bias control. Based on the error signals, the operating point drift can be determined, and the drift voltage can be compensated.

[0042] In some embodiments, the bias control unit 110 includes a multiplier and an adder. The multiplier is configured to perform multiplication operations on corresponding elements of the electrical signal and the pilot signal to determine the multiplication result corresponding to each element; the adder is configured to accumulate the multiplication results corresponding to each element to determine a correlation value.

[0043] In some embodiments, the number of multipliers is equal to the number of elements, and each multiplier corresponds to one of the elements to determine the multiplication result corresponding to each element.

[0044] In some embodiments, the number of multipliers is one, and the multiplier is configured to be time-division multiplexed to sequentially determine the multiplication result corresponding to each element.

[0045] The obtained correlation values ​​are input to the three DC bias voltage ports of the dual parallel Mach-Zehnder modulator 104 after being processed by a DAC. Additionally, the pilot signal, along with the signal output from the bias control unit 110, is also sent to the DC bias ports of the dual parallel Mach-Zehnder modulator 104 for DC voltage compensation and operating point locking. The three DC bias voltage outputs of the bias control unit 110 are respectively connected to the three DC bias voltage ports of the dual parallel Mach-Zehnder modulator 104.

[0046] Figure 3 A flowchart of the method for controlling a laser communication terminal according to this disclosure is shown. For example, after startup, a coarse scan stage is first entered, in which scan parameters are set, and then the power is calculated by scanning the bias voltage (i.e., the bias voltage). Next, feature points are searched. Then, the coarse scan bias voltage is output. Next, a fine scan stage is entered. In the fine scan stage, pilot signals are generated, then correlation detection is performed, and the bias voltage is updated based on the direction. Finally, the final bias voltage is output.

[0047] For example, the process begins with a coarse scan phase. By enabling the drive circuit to output a larger step voltage for coarse scanning, the first sub-Mach-Zehnder modulator 141, the second sub-Mach-Zehnder modulator 142, and the phase modulator 143 are scanned, and parameters such as the step voltage value, maximum and minimum DC power, and half-wave voltage are recorded. After the coarse scan phase, the process moves to a fine tracking phase for more precise voltage adjustment. The pilot signal from the pilot signal generation unit 108 is directly used as the correlation reference signal. By calculating the cross-correlation value between the pilot signal and the acquired feedback data signal (e.g., the electrical signal output by the photoelectric conversion unit 106), the first and second harmonic components of the current pilot signal are directly extracted. The correlation result (i.e., the correlation value between the electrical signal and the pilot signal) is used as an error signal. The sign and amplitude of the correlation value determine whether the current DC operating point has drifted and the degree of drift, thus compensating for the bias voltage.

[0048] Figure 4 A flowchart illustrating a method 400 for controlling a laser communication terminal according to an embodiment of this disclosure is shown. Method 400 can be executed by a bias control unit 110, or in… Figure 5 The method is performed at the illustrated electronic device 500. It should be understood that method 400 may also include additional steps not shown and / or the steps shown may be omitted, and the scope of this disclosure is not limited in this respect.

[0049] At step 402, the correlation value between the electrical signal and the pilot signal with respect to the optical carrier is determined as an error signal.

[0050] At step 404, the bias voltage of the dual parallel Mach-Zehnder modulator is adjusted according to the error signal.

[0051] In some embodiments, the method 400 further includes: determining the maximum point of optical power, the minimum point of optical power, and the half-wave voltage corresponding to the dual parallel Mach-Zehnder modulator; determining the scanning range of the bias voltage of the dual parallel Mach-Zehnder modulator based on the maximum point of optical power, the minimum point of optical power, and the half-wave voltage; and scanning the bias voltage of the dual parallel Mach-Zehnder modulator within the scanning range at a first predetermined step size during a coarse scanning stage.

[0052] In some embodiments, the method 400 further includes: determining a first voltage corresponding to the intermediate power value of the dual parallel Mach-Zehnder modulator; controlling the pilot signal generation unit to provide first pilot signals to the I-path and Q-path respectively; determining the error signal during the fine scanning stage; and adjusting the bias voltage of the dual parallel Mach-Zehnder modulator based on the error signal and a second predetermined step size, with the first voltage as the initial value, the second predetermined step size being smaller than the first predetermined step size.

[0053] In some embodiments, adjusting the bias voltage of the dual parallel Mach-Zehnder modulator based on the error signal and a second predetermined step size, using the first voltage as an initial value, includes: maintaining the adjustment direction of the bias voltage of the dual parallel Mach-Zehnder modulator in response to determining that the error signal is positive; and determining that the current bias voltage is closer to the optimal operating point of the dual parallel Mach-Zehnder modulator in response to determining that the current error signal is greater than the error signal corresponding to the previous scan operation.

[0054] In some embodiments, the method 400 further includes: setting the bias voltage with respect to the Q path and the P path to zero, and scanning the bias voltage with respect to the I path to determine the maximum point of optical power, the minimum point of optical power, and a first voltage.

[0055] In some embodiments, the method 400 further includes: determining a second voltage corresponding to the minimum point of optical power; controlling the pilot signal generation unit to provide a first pilot signal to the I-path; determining the error signal during a fine scanning phase of the bias voltage of the I-path; and adjusting the bias voltage of the I-path based on the properties of the error signal and a second predetermined step size, using the second voltage as an initial value.

[0056] In some embodiments, adjusting the bias voltage with respect to the I-path based on the properties of the error signal and a second predetermined step size, using the second voltage as an initial value, includes: decreasing the bias voltage with respect to the I-path in response to determining that the error signal is a positive value; and increasing the bias voltage with respect to the I-path in response to determining that the error signal is a negative value.

[0057] In some embodiments, the method 400 further includes: setting the bias voltages for the I-path and the Q-path to the bias voltages corresponding to the maximum point of optical power; scanning the bias voltages for the P-path to determine a third voltage corresponding to the intermediate power value for the P-path; controlling the pilot signal generation unit to provide a first pilot signal to the I-path and a second pilot signal to the Q-path, the first pilot signal and the second pilot signal being orthogonal; determining the error signal during a fine scanning phase of the bias voltages for the P-path; and adjusting the bias voltages for the P-path based on the properties of the error signal and a second predetermined step size, using the third voltage as an initial value.

[0058] In some embodiments, the laser communication terminal 100 operates in accordance with the following steps.

[0059] Step 1: After the laser communication terminal 100 is powered on, it enters the coarse scanning stage. The purpose of coarse scanning is to find the operating point close to the bias voltage, so as to reduce the time required to lock the operating point in the fine tracking (i.e., fine scanning) stage.

[0060] First, determine the scanning range for the bias voltage of the dual parallel Mach-Zehnder modulator 104. For example, the coarse scan process needs to include at least one maximum transmission point and one minimum transmission point. The maximum transmission point is, for example, the point where the optical power corresponding to the dual parallel Mach-Zehnder modulator reaches its maximum value; the minimum transmission point is, for example, the point where the optical power corresponding to the dual parallel Mach-Zehnder modulator reaches its minimum value.

[0061] Based on the transfer function characteristics of the dual parallel Mach-Zehnder modulator 104, it can be determined that the set scanning range is, for example, slightly larger than twice the half-wave voltage of the dual parallel Mach-Zehnder modulator 104.

[0062] For example, the scanning range of the bias voltage of the dual parallel Mach-Zehnder modulator is determined based on the maximum and minimum optical power points and the half-wave voltage. During the coarse scanning phase, the bias voltage of the dual parallel Mach-Zehnder modulator is scanned within the scanning range according to a first predetermined step size.

[0063] In some embodiments, a trade-off can be made between the step length (i.e., step size) in the coarse scan and fine tracking phases. The smaller the step length of the coarse scan, i.e. the higher the accuracy, the shorter the time it takes for the fine tracking to lock onto the working point; if the step length of the coarse scan is larger, i.e. the lower the accuracy, the longer the time it takes for the fine tracking to lock onto the working point.

[0064] In some embodiments, the coarse scanning stage adopts... The scanning is performed using a step length. Characterizes the step size of the coarse scan phase; Characterizing half-wave voltage requires clarification as it is a core parameter in optical communication modulation. It should be understood that half-wave voltage represents the voltage required to create a half-wavelength optical path difference (corresponding to a 180-degree phase difference) between the two perpendicularly polarized components of a light wave during transmission. Furthermore, half-wave voltage can characterize the driving voltage difference required to create a 180-degree phase difference between the optical signals in the two arms (e.g., the first sub-Mach-Zehnder modulator 141 and the second sub-Mach-Zehnder modulator 142) of a dual parallel Hertzsprung-Zehnder modulator.

[0065] Step 2: With the amplitude of the radio frequency signal (e.g., optical carrier signal) and the input optical power remaining unchanged, the bias control unit 110 performs bias voltage scanning on the first sub-Mach-Zehnder modulator 141, the second branch including the second sub-Mach-Zehnder modulator 142 connected in series, and the phase modulator 143, respectively.

[0066] For example, the bias control unit 110 controls the quadrature operating points of the I-channel and Q-channel. First, the bias control unit 110 sets the bias voltages of the Q-channel and P-channel to zero. Then, the bias control unit 110 scans the bias voltage value of the I-channel. This scanning process is, for example, based on the first step length. The bias control unit 110 determines the maximum and minimum points of the optical power of the dual parallel Mach-Zehnder modulator 104. Based on the maximum and minimum points of the optical power, the bias control unit 110 determines the intermediate value of the optical power and the voltage corresponding to the intermediate value. (e.g., the first voltage).

[0067] Then, the fine-tracking phase for the I and Q paths begins. This phase uses relevant detection to detect pilot harmonics, enabling real-time tracking of the bias point in response to environmental changes. This ensures the bias voltage remains near the optimal operating point for as long as possible, and as close as possible to the optimal bias point. In the absence of an RF signal, a pilot amplitude is applied to the DC bias voltage ports of the I and Q paths. ,frequency pilot signal The initial value obtained from the coarse scan Based on (e.g., the first voltage), combined with a smaller step length Perform a more refined voltage scan, i.e., the adjusted bias voltage. , ,in This represents the direction of bias voltage adjustment. By finding the correlation value between the data signal and the pilot signal after the pilot signal is added, and using this as an error signal for bias control, the position of maximum first harmonic of the pilot signal can be located: if the current correlation value is positive, it indicates that the current adjustment direction is effective and should be maintained; if the current correlation value amplitude is greater than the previous correlation value amplitude, it indicates that the current bias position is closer to the optimal operating point. Conversely, the opposite is also true.

[0068] Step 3: Control the I-channel to operate at the minimum operating point: First, set the bias voltages corresponding to the Q-channel and P-channel to 0, scan the bias voltage values ​​of the I-channel, record the minimum optical power point, and record the corresponding voltage at this time. (e.g., the second voltage).

[0069] Then, the I-channel fine tracking stage begins, where a pilot amplitude of [value missing] is applied to the DC bias voltage port of the I-channel. ,frequency pilot signal Where A, for example, characterizes the pilot amplitude (e.g., as...). Initial values ​​obtained from coarse scanning. Based on this, combined with a smaller step length Perform a more refined voltage scan, i.e., the adjusted bias voltage. , ,in This represents the direction of bias voltage adjustment. By finding the correlation value between the data signal and the pilot signal after the pilot signal is added, and using this as an error signal for bias control, the position of minimum first harmonic is found: if the current correlation value is greater than zero, it indicates that the current bias point is to the right of the operating point, the current bias voltage is too high, and the voltage needs to be reduced; if the current correlation value is less than zero, it indicates that the current bias point is to the left of the operating point, the current bias voltage is too low, and the voltage needs to be increased.

[0070] Step 4: Control the P-path to operate at the quadrature operating point. Fix the bias voltage values ​​of the I-path and Q-path at the maximum optical power points, scan the bias voltage of the P-path, record the maximum and minimum optical power values, and calculate the bias voltage value of the intermediate value QUAD from these values. (For example, the third voltage). Orthogonal pilot signals are applied to the I and Q paths respectively. , The pilot signals are orthogonal cosine signals, and two orthogonal pilot signals have minimal impact on the jitter of the data signal. During modulation, the applied pilot signals carry information about the operating point drift. Entering the P-path fine tracking stage, a small step value is used for left and right scanning to find the maximum value of the second harmonic of the pilot signal, thus obtaining the adjusted voltage. , .

[0071] Step 5: The core algorithms for controlling different operating points are, for example: locking the orthogonal point operating point, whose core control algorithm is based on the maximum first harmonic of the pilot signal; locking the minimum transmission point operating point, whose core control algorithm is based on the minimum first harmonic of the pilot signal.

[0072] Step 6: After digital-to-analog conversion by DAC, the analog compensation voltage output by bias control unit 110 is applied to dual parallel Mach-Zehnder modulator 104 through drive circuit and pilot signal to control the operating point of dual parallel Mach-Zehnder modulator 104.

[0073] Figure 5 A schematic block diagram of an example electronic device 500 for controlling a laser communication terminal, which can be used to implement embodiments of the present disclosure, is shown. As shown, the electronic device 500 includes a central processing unit (i.e., CPU 501), which can perform various appropriate actions and processes according to computer program instructions stored in read-only memory (i.e., ROM 502) or loaded from storage unit 508 into random access memory (i.e., RAM 503). Various programs and data required for the operation of the electronic device 500 may also be stored in RAM 503. The CPU 501, ROM 502, and RAM 503 are interconnected via bus 504. Input / output interfaces (i.e., I / O interfaces 505) are also connected to bus 504.

[0074] Multiple components in electronic device 500 are connected to I / O interface 505, including: input unit 506, such as keyboard, mouse, microphone, etc.; output unit 507, such as various types of monitors, speakers, etc.; storage unit 508, such as disk, optical disk, etc.; and communication unit 509, such as network card, modem, wireless transceiver, etc. Communication unit 509 allows electronic device 500 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0075] The various processes and handling described above, such as method 400, can be executed by CPU 501. For example, in some embodiments, method 400 can be implemented as a computer software program tangibly contained in a machine-readable medium, such as storage unit 508. In some embodiments, part or all of the computer program can be loaded and / or installed on electronic device 500 via ROM 502 and / or communication unit 509. When the computer program is loaded into RAM 503 and executed by CPU 501, one or more actions of method 400 described above can be performed.

[0076] This disclosure relates to methods, apparatus, systems, electronic devices, computer-readable storage media, and / or computer program products. A computer program product may include computer-readable program instructions for performing various aspects of this disclosure.

[0077] In some embodiments, the method 400 described above can be implemented as a computer program product. The computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for performing various aspects of this disclosure.

[0078] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0079] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge computing devices. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to computer-readable storage media within the respective computing / processing device.

[0080] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0081] Various aspects of this disclosure are described herein with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer-readable program instructions.

[0082] These computer-readable program instructions can be provided to a processing unit of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processing unit of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner. Thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0083] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0084] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of an instruction, which contains one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0085] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

[0086] The above are merely optional embodiments of this disclosure and are not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A laser communication terminal, characterized in that, include: The laser is configured to output an optical carrier. A dual parallel Mach-Zehnder modulator is configured to receive a pilot signal and an optical carrier and output a modulated optical signal. The photoelectric conversion unit is configured to convert a modulated optical signal into an electrical signal; The pilot signal generation unit is configured to generate pilot signals; as well as A bias control unit is configured to determine the correlation value between the electrical signal and the pilot signal as an error signal, and to adjust the bias voltage with respect to the dual parallel Mach-Zehnder modulator based on the error signal.

2. The laser communication terminal according to claim 1, characterized in that, The bias control unit includes: A multiplier is configured to perform multiplication operations on corresponding elements of the electrical signal and the pilot signal to determine a multiplication result for each element; and An adder is configured to accumulate the multiplication results corresponding to each of the elements in order to determine the relevant value.

3. The laser communication terminal according to claim 2, characterized in that, The number of multipliers is equal to the number of elements, and each multiplier corresponds to one of the elements in order to determine the multiplication result corresponding to each element.

4. The laser communication terminal according to claim 2, characterized in that, The number of multipliers is one, and the multiplier is configured for time-division multiplexing in order to sequentially determine the multiplication result corresponding to each element.

5. The laser communication terminal according to claim 1, characterized in that, The dual parallel Mach-Zehnder modulator includes a first branch and a second branch connected in parallel. The first branch includes a first sub-Mach-Zehnder modulator, and the second branch includes a second sub-Mach-Zehnder modulator connected in series and a phase modulator.

6. A method for controlling a laser communication terminal, said laser communication terminal as described in any one of claims 1 to 5, characterized in that, The method includes: Determine the correlation value between the electrical signal and the pilot signal regarding the optical carrier to serve as an error signal; and The bias voltage of the dual parallel Mach-Zehnder modulator is adjusted based on the error signal.

7. The method according to claim 6, characterized in that, Also includes: Determine the maximum and minimum optical power points and half-wave voltage corresponding to the dual parallel Mach-Zehnder modulator; The scanning range of the bias voltage of the dual parallel Mach-Zehnder modulator is determined based on the maximum point of optical power, the minimum point of optical power, and the half-wave voltage. And during the coarse scan phase, the bias voltage of the dual parallel Mach-Zehnder modulator is scanned within the scan range at a first predetermined step size.

8. The method according to claim 7, characterized in that, Also includes: Determine the first voltage corresponding to the power midpoint of the dual parallel Mach-Zehnder modulator; The pilot signal generation unit controls the first pilot signal to be provided to both the I-channel and the Q-channel; The error signal is determined during the fine scanning phase; as well as Using the first voltage as the initial value, the bias voltage of the dual parallel Mach-Zehnder modulator is adjusted according to the error signal and the second predetermined step size, where the second predetermined step size is smaller than the first predetermined step size.

9. The method according to claim 8, characterized in that, Using the first voltage as an initial value, adjusting the bias voltage of the dual parallel Mach-Zehnder modulator according to the error signal and the second predetermined step size includes: In response to determining that the error signal is positive, the adjustment direction of the bias voltage with respect to the dual parallel Mach-Zehnder modulator is maintained; and In response to determining that the current error signal is greater than the error signal corresponding to the previous scan operation, it is determined that the current bias voltage is closer to the optimal operating point of the dual parallel Mach-Zehnder modulator.

10. The method according to claim 9, characterized in that, Also includes: Set the bias voltages for the Q and P paths to zero, and scan the bias voltages for the I path to determine the maximum and minimum optical power points and the first voltage.

11. The method according to claim 10, characterized in that, Also includes: Determine the second voltage corresponding to the point of minimum optical power; The pilot signal generation unit controls the first pilot signal to be provided to the I-channel; The error signal is determined during the fine scan phase regarding the bias voltage of the I-path; as well as Using the second voltage as the initial value, the bias voltage of the I-path is adjusted according to the properties of the error signal and the second predetermined step size.

12. The method according to claim 11, characterized in that, Using the second voltage as an initial value, adjusting the bias voltage with respect to the I-path according to the properties of the error signal and the second predetermined step size includes: In response to determining that the error signal is positive, the bias voltage with respect to path I is reduced; and In response to determining that the error signal is negative, the bias voltage for the I-path is increased.

13. The method according to claim 11, characterized in that, Also includes: Set the bias voltages for the I and Q paths to the bias voltages corresponding to the maximum optical power points, and scan the bias voltages for the P path to determine the third voltage corresponding to the median power value for the P path. The control pilot signal generation unit provides a first pilot signal to the I channel and a second pilot signal to the Q channel, respectively. The first pilot signal and the second pilot signal are orthogonal. The error signal is determined during the fine scan phase regarding the bias voltage of the P-path; as well as Using the third voltage as the initial value, the bias voltage of the P-path is adjusted according to the properties of the error signal and the second predetermined step size.

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