A Method for Measuring the Overall Frequency Response of an Optical Transmitter Based on a Low-Bandwidth Photodetector

Abstract

This invention provides a method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector, comprising: dividing the overall frequency response range of the optical transmitter into several test regions; acquiring several initial subcarrier signals and preprocessing them; frequency-shifting the preprocessed initial subcarrier signals to each test region to obtain several test signals; transmitting a first test signal using the optical transmitter and detecting the first test signal at the optical receiver using a photodetector with a preset bandwidth; performing analog-to-digital conversion on the detection result to obtain the corresponding digital signal; reconstructing the digital signal using the PhareADMM algorithm to obtain the optical transmitter frequency response of the test region corresponding to the first test signal; repeating the above steps until all test signals have been transmitted to obtain the overall frequency response of the optical transmitter; this invention can realize the measurement of the overall frequency response of an optical transmitter under a low-bandwidth photodetector.

Description

Technical Field

[0001] This invention relates to the field of optical fiber communication technology, and more specifically, to a method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector. Background Technology

[0002] In recent years, with the rapid development of new technologies such as artificial intelligence and the Internet of Things, computing power has become an important indicator for measuring my country's economic situation. However, the development of computing networks requires high-quality transportation capacity, making the speed-up and capacity expansion of fiber optic communication systems an urgent matter.

[0003] Optical fiber communication systems consist of a transmitter, a transmission link, and a receiver. To improve communication speed and capacity, higher baud rates and modulation formats are widely used, making modern coherent optical communication systems more sensitive to transmitter degradation. For example, even a small mismatch between the I and Q branches in an optical transmitter can have a severe negative impact on system performance. If the overall frequency response of the transmitter can be obtained before deployment and digital pre-compensation is performed at the transmitter, the overall transmission performance of the system can be effectively improved and costs reduced.

[0004] Currently, most field measurements of optical transmitters employ sinusoidal wave frequency sweeping. For example, existing technology proposes a frequency response measurement technique for optical transmitters based on single-tone signal frequency sweeping. This scheme transmits a single-tone signal, applying the transmitter's amplitude-frequency response to the signal amplitude, and estimates the amplitude-frequency response of the optical transmitter by measuring the difference in output power. However, this scheme can only obtain the amplitude-frequency response. Another example is a method for monitoring the frequency response and time delay of optical transmitters disclosed in existing patent documents. This scheme divides the measurement area, applies the response to the corresponding two-tone signal, and after square-law detection, moves the response information to the beat frequency term in the low-frequency region, which is then received by a low-bandwidth PD, thus obtaining the overall frequency response. However, this scheme struggles to obtain the frequency response at zero frequency.

[0005] In summary, current technologies have the problem of difficulty in obtaining the overall frequency response of the transmitter. Summary of the Invention

[0006] To overcome the problem of difficulty in obtaining the overall frequency response of a transmitter in the prior art, this invention proposes a method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector. This method aims to solve the problem of measuring the frequency response of an optical transmitter at a lower cost and is of great significance for improving the performance of optical fiber communication systems.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] A method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector includes the following steps:

[0009] S1: Divide the overall frequency response range of the optical transmitter into several test regions, acquire several initial subcarrier signals and preprocess them, and then frequency-shift the preprocessed initial subcarrier signals to each of the test regions to obtain several test signals.

[0010] S2: A first test signal is emitted using an optical transmitter, and the first test signal is detected using a photodetector with a preset bandwidth at the optical receiver to obtain the detection result; the first test signal is any one of the plurality of test signals;

[0011] S3: Perform analog-to-digital conversion on the detection results to obtain the corresponding digital signal, and reconstruct the digital signal using the PhareADMM algorithm to obtain the optical transmitter frequency response of the test area corresponding to the first test signal;

[0012] S4: Repeat steps S2 to S3 until all signals to be tested have been transmitted, and obtain the overall frequency response of the optical transmitter.

[0013] Preferably, in step S1, the preprocessing includes: zero-fill upsampling and pulse shaping.

[0014] Preferably, the pulse shaping is performed after the subcarrier is zero-filled upsampled and then passed through a root-raised cosine filter.

[0015] Preferably, the roll-off factor of the root-raised cosine filter is 0.1.

[0016] Preferably, in step S1, the initial subcarrier signal is specifically a QAM symbol sequence containing a known bit stream.

[0017] Preferably, in step S2, the preset bandwidth of the photodetector is greater than the range of the test area corresponding to the first test signal.

[0018] Preferably, in step S3, the iterative update expression of the PhareADMM algorithm is as follows:

[0019]

[0020]

[0021]

[0022]

[0023]

[0024] in, For the i-th iteration of the first measured signal, it is an intermediate variable used for phase update of the reconstructed signal. Let i be the measurement matrix of the first signal to be measured. Let i be the reconstructed signal vector of the i-th first signal to be tested. Let be the estimated vector of the optical transmitter frequency response within the test area corresponding to the i-th first signal to be tested. Let be the Lagrange multiplier corresponding to the i-th first signal to be tested. Let represent the amplitude information of the i-th first signal to be tested, and k be the iteration number index, ranging from 0 to K, where K is a positive integer. The iteration step size, As the stopping criterion for iteration, The Frobenius norm represents the vector. It represents the Hadamaji.

[0025] The present invention also provides an overall frequency response measurement system for an optical transmitter based on a low-bandwidth photodetector, comprising an optical transmitter, an optical receiver, and a data processing module; the optical receiver and the data processor are electrically connected.

[0026] The optical transmitter is used to acquire an initial subcarrier signal and preprocess it, then frequency-shift the preprocessed initial subcarrier signal to each of the regions to be tested to obtain several signals to be tested; and to transmit the signals to be tested.

[0027] The optical receiver is used to detect the signal to be tested using a photodetector and obtain the detection result.

[0028] The data processing module is used to perform analog-to-digital conversion on the detection results to obtain the corresponding digital signal, and to reconstruct the digital signal using the PhareADMM algorithm to obtain the corresponding optical transmitter frequency response.

[0029] The present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the above-described method.

[0030] The present invention also provides an electronic device, including a processor and a memory, the memory storing computer-readable instructions, which, when executed by the processor, perform the steps of the method described above.

[0031] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0032] This invention provides a method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector. First, the overall frequency response range of the optical transmitter is divided into several test regions. Several initial subcarrier signals are acquired and preprocessed. The preprocessed initial subcarrier signals are then frequency-shifted to each test region to obtain several test signals. Next, the optical transmitter transmits a first test signal, and a photodetector with a preset bandwidth is used at the optical receiver to detect the first test signal, obtaining the detection result. The first test signal is any one of the several test signals. Then, the detection result is processed by analog-to-digital conversion to obtain the corresponding digital signal. The PhareADMM algorithm is used to reconstruct the digital signal to obtain the optical transmitter frequency response of the test region corresponding to the first test signal. The above steps are repeated until all test signals have been transmitted, thus obtaining the overall frequency response of the optical transmitter.

[0033] This invention employs the same modulation format and symbol sequence as modern coherent optical communication systems at the transmitting end, eliminating the need to send specific training sequences. In terms of device selection, it uses a single low-bandwidth PD to receive the transmitter output signal, requiring only a few additional devices to measure the frequency response of the optical transmitter at the transmitting end, significantly reducing equipment costs. By obtaining the corresponding frequency band response through each subcarrier, the actual measurable frequency range is wider. Attached Figure Description

[0034] Figure 1 This is a flowchart of a method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector, as provided in Example 1.

[0035] Figure 2 This is a flowchart of a method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector, as provided in Example 2.

[0036] Figure 3 This is an overall framework diagram of the optical transmitter frequency response measurement method based on a low-bandwidth photodetector provided in Example 2.

[0037] Figure 4 The figure shows the simulation results of the overall frequency response measurement method of an optical transmitter based on a low-bandwidth photodetector provided in Example 2.

[0038] Figure 5 This is a system structure diagram of a method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector, as provided in Example 3. Detailed Implementation

[0039] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this application.

[0040] To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions;

[0041] It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0042] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] Example 1

[0044] like Figure 1 As shown, this embodiment provides a method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector, including the following steps:

[0045] S1: Divide the overall frequency response range of the optical transmitter into several test regions, acquire several initial subcarrier signals and preprocess them, and then frequency-shift the preprocessed initial subcarrier signals to each of the test regions to obtain several test signals.

[0046] S2: A first test signal is emitted using an optical transmitter, and the first test signal is detected using a photodetector with a preset bandwidth at the optical receiver to obtain the detection result; the first test signal is any one of the plurality of test signals;

[0047] S3: Perform analog-to-digital conversion on the detection results to obtain the corresponding digital signal, and reconstruct the digital signal using the PhareADMM algorithm to obtain the optical transmitter frequency response of the test area corresponding to the first test signal;

[0048] S4: Repeat steps S2 to S3 until all signals to be tested have been transmitted, and obtain the overall frequency response of the optical transmitter.

[0049] In the specific implementation process, firstly, based on the overall frequency response range of the optical transmitter, it is scientifically and reasonably divided into multiple test regions. For example, if the digital subcarrier (DSM) signal baud rate is 56 GBaud and the modulation format is 16QAM, the overall frequency response range of the optical transmitter is divided into four test intervals, each subcarrier corresponding to one test interval, with a baud rate of 14 Gbaud. The frequency range from 15.4 GHz to 30.8 GHz corresponds to the fourth subcarrier test region. This embodiment only simulates this region; the simulation process for the other three regions is similar. Segmentation can effectively reduce the complexity of a single measurement and improve measurement accuracy. Next, several initial subcarrier signals are generated, and the generated initial subcarrier signals are preprocessed. Specifically, this includes zero-fill upsampling and pulse shaping using a root-raised cosine filter, with the roll-off factor of the filter set to 0.1. Zero-fill upsampling makes the signal more sparse in the frequency domain, facilitating subsequent frequency shift operations; pulse shaping optimizes the spectral characteristics of the signal, reduces out-of-band radiation, and maintains signal integrity, ensuring signal quality during transmission. After preprocessing, the subcarrier signals are frequency-shifted to their corresponding test regions, forming several test signals. The optical transmitter then sequentially transmits these generated test signals. At the optical receiver, a photodetector with a preset bandwidth is used for detection. The bandwidth of this detector is strictly set to be greater than the range corresponding to the test signal region to ensure effective capture of signal strength information and avoid signal distortion or information loss due to insufficient detector bandwidth.

[0050] The analog signal detected by the photodetector is then converted into a digital signal through high-precision analog-to-digital conversion. This step discretizes the continuous analog signal, making it recognizable and analyzeable by the digital signal processing system, providing a data foundation for subsequent frequency response calculations. The PhareADMM algorithm is then used for in-depth processing of the converted digital signal. This algorithm, through a complex iterative calculation process, accurately recovers the phase information of the signal from the intensity information. Combined with the known amplitude information, the frequency response of the optical transmitter in the current test area is finally calculated.

[0051] Finally, the above measurement process will be repeated for all areas under test until the entire preset frequency band is covered. The system will then integrate and process the frequency response results obtained from each area to obtain the overall frequency response of the optical transmitter.

[0052] Traditional measurement methods often rely on expensive equipment such as high-bandwidth spectrum analyzers. These devices are costly, complex to operate, and have stringent requirements for the field measurement environment, making them difficult to adapt to diverse field conditions. This results in high costs for the purchase, maintenance, and operation of measurement equipment, severely restricting the widespread implementation of measurement work.

[0053] To address the shortcomings of existing measurement schemes in obtaining the overall frequency response of optical transmitters, this embodiment innovatively introduces a method for measuring the overall frequency response of optical transmitters based on a low-bandwidth photodetector. Specifically, the scheme employs a single low-bandwidth photodetector instead of a traditional high-bandwidth spectrum analyzer. This photodetector is inexpensive and offers stable and reliable performance. By rationally designing the measurement method and signal processing algorithm, and fully utilizing the performance of the low-bandwidth photodetector, accurate measurement of the overall frequency response of the optical transmitter is achieved, significantly reducing the procurement and maintenance costs of the measurement equipment and making the measurement scheme more economical and practical.

[0054] Furthermore, the transmitter uses the same modulation format and symbol sequence as the coherent optical communication system, eliminating the need to send specific training sequences and simplifying the measurement process. Simultaneously, by combining segmented frequency shifting technology and the PhareADMM phase retrieval algorithm, the amplitude and phase frequency responses of the optical transmitter can be fully acquired, effectively overcoming the limitations of zero-frequency measurement and achieving accurate measurement of frequency response over a wide frequency range. This ensures that the measurement results comprehensively and accurately reflect the actual performance of the optical transmitter.

[0055] Example 2

[0056] like Figure 2 As shown, this embodiment provides a method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector, including the following steps:

[0057] S1: Divide the overall frequency response range of the optical transmitter into several test regions, acquire several initial subcarrier signals and preprocess them, and then frequency-shift the preprocessed initial subcarrier signals to each of the test regions to obtain several test signals.

[0058] S2: A first test signal is emitted using an optical transmitter, and the first test signal is detected using a photodetector with a preset bandwidth at the optical receiver to obtain the detection result; the first test signal is any one of the plurality of test signals;

[0059] S3: Perform analog-to-digital conversion on the detection results to obtain the corresponding digital signal, and reconstruct the digital signal using the PhareADMM algorithm to obtain the optical transmitter frequency response of the test area corresponding to the first test signal;

[0060] S4: Repeat steps S2~S3 until all signals to be tested have been transmitted, and obtain the overall frequency response of the optical transmitter.

[0061] In step S1, the preprocessing includes: zero-fill upsampling and pulse shaping;

[0062] After the subcarrier is zero-filled upsampled, the pulse is shaped by a root-raised cosine filter; the roll-off factor of the root-raised cosine filter is specifically 0.1.

[0063] In step S1, the initial subcarrier signal is specifically a QAM symbol sequence containing a known bit stream;

[0064] In step S2, the preset bandwidth of the photodetector is greater than the range of the test area corresponding to the first test signal.

[0065] In step S3, the iterative update expression of the PhareADMM algorithm is as follows:

[0066]

[0067]

[0068]

[0069]

[0070]

[0071] in, For the i-th iteration of the first measured signal, it is an intermediate variable used for phase update of the reconstructed signal. Let i be the measurement matrix of the first signal to be measured. Let i be the reconstructed signal vector of the i-th first signal to be tested. Let be the estimated vector of the optical transmitter frequency response within the test area corresponding to the i-th first signal to be tested. Let be the Lagrange multiplier corresponding to the i-th first signal to be tested. Let represent the amplitude information of the i-th first signal to be tested, and k be the iteration number index, ranging from 0 to K, where K is a positive integer. The iteration step size, As the stopping criterion for iteration, The Frobenius norm represents the vector. It represents the Hadamaji.

[0072] In the specific implementation process, such as Figure 3 As shown, the measurement process begins first, with system initialization and settings for the test area, subcarrier parameters, and initial parameters for the PhareADMM algorithm. During this stage, the system loads pre-configured measurement parameters, including the division of the test area, the modulation format of the subcarrier signal (e.g., 16QAM), the frequency range of the initial subcarrier signal, the number of iterations of the PhareADMM algorithm, and the step size.

[0073] The system determines whether the initial subcarrier signal meets the frequency shift condition, i.e., whether the signal has undergone zero-fill upsampling and pulse shaping. If the initial subcarrier signal has undergone zero-fill upsampling and pulse shaping, it is frequency-shifted to the test region; otherwise, preprocessing is repeated. In the signal preprocessing stage, the system first performs zero-fill upsampling on the initial subcarrier signal. By inserting zero-value samples into the signal's time-domain data, the sampling rate is increased, making the signal sparser in the frequency domain, facilitating subsequent frequency shifting. Subsequently, the signal undergoes pulse shaping through a root-raised cosine filter with a roll-off factor set to 0.1 to optimize the signal's spectral characteristics, reduce out-of-band radiation, and maintain signal integrity. Next, the system frequency-shifts the preprocessed subcarrier signals to various test regions, forming several test signals. In practice, the transmitter frequency response is directly estimated; if the estimated frequency response matches the design, the scheme is feasible.

[0074] The system determines whether a signal to be tested has been selected for transmission. If a signal to be tested has been selected, the optical transmitter transmits the signal; otherwise, it selects the first signal from the list of signals to be tested for transmission. During the signal transmission phase, the system sequentially selects signals to be tested from the list for transmission. The list of signals to be tested stores all signals to be tested and waits to be transmitted in a preset order. When the system determines that a signal to be tested has not yet been transmitted, it selects the first signal from the list and sends it to the optical transmitter. After receiving the signal to be tested, the optical transmitter transmits the signal, and a photodetector with a preset bandwidth detects the received optical signal. The bandwidth of the photodetector is strictly set to be greater than the range corresponding to the signal to be tested to ensure effective capture of signal strength information and avoid signal distortion or information loss due to insufficient detector bandwidth. In this embodiment, a low-bandwidth photodetector is simulated by adding a low-pass filter with a cutoff frequency of 20 GHz after square-law detection.

[0075] The system determines whether the detection result has been acquired and analog-to-digital conversion (ADC) has been completed. If yes, it proceeds to the PhareADMM algorithm processing stage; otherwise, it waits for the detection result and performs ADC. The analog signal output by the photodetector needs to undergo ADC processing before it can be recognized and analyzed by the digital signal processing system. ADC performs high-precision sampling and quantization on the received analog signal, converting it into a digital signal. During the conversion process, the system ensures that the sampling frequency meets the requirements of the Nyquist sampling theorem to avoid signal aliasing. The converted digital signal is stored in a buffer, awaiting further processing. The system determines whether the detection result has been successfully acquired and ADC completed. If yes, it further processes the digital signal using the PhareADMM algorithm; otherwise, it continues to wait for the detection result and perform ADC until a valid digital signal is acquired.

[0076] Determine whether the frequency response calculation for the current test region has been completed. If yes, store the calculation result; otherwise, continue executing the PhareADMM algorithm until convergence. The PhareADMM algorithm uses the reconstructed phase and amplitude information to calculate the frequency response. During the calculation process, the algorithm gradually improves the calculation accuracy through iterative updates. In this embodiment, the iterative update expression of the PhareADMM algorithm is as follows:

[0077]

[0078]

[0079]

[0080]

[0081]

[0082] in Let be the intermediate variable used for phase update of the reconstructed signal during the i-th subcarrier iteration process. Let i be the measurement matrix for the i-th subcarrier. Let i be the reconstructed signal vector of the i-th subcarrier. Let be the estimated vector of the optical transmitter frequency response within the frequency range of the i-th subcarrier. For the i-th subcarrier, the composite form of the Lagrange multiplier is... Let represent the amplitude information of the i-th subcarrier, and k be the iteration number index of the algorithm, ranging from 0 to K. Step size, As a stop standard, The Frobenius norm represents the vector. Represents the Hadamah altar;

[0083] After each iteration, the system determines whether the convergence condition is met, i.e., whether the number of iterations has reached a preset value or the error is less than a set threshold. If the convergence condition is met, the frequency response calculation for the current test region is considered complete, and the calculation result is stored. If the convergence condition is not met, the PhareADMM algorithm continues to be executed until the convergence requirement is met. The simulation results are as follows: Figure 4 As shown;

[0084] Finally, the frequency response results of all tested areas are integrated to form the overall frequency response of the optical transmitter, and the measurement results are output. This step collects the frequency response results of each tested area and integrates the data. During the integration process, the system fully considers the frequency response characteristics of each tested area to ensure the accuracy and reliability of the overall frequency response results. Ultimately, the overall frequency response curve or data report of the optical transmitter is generated, and the measurement results are output.

[0085] Example 3

[0086] like Figure 5 As shown, this embodiment provides an overall frequency response measurement system for an optical transmitter based on a low-bandwidth photodetector, including an optical transmitter 301, an optical receiver 302, and a data processing module 303;

[0087] The optical transmitter 301 is used to acquire an initial subcarrier signal and preprocess it, then frequency-shift the preprocessed initial subcarrier signal to each of the regions to be tested to obtain several signals to be tested; and to transmit the signals to be tested.

[0088] The optical receiver 302 is used to detect the signal to be tested using a photodetector and obtain the detection result;

[0089] The data processing module 303 is used to perform analog-to-digital conversion on the detection results to obtain the corresponding digital signal, and to reconstruct the digital signal using the PhareADMM algorithm to obtain the corresponding optical transmitter frequency response.

[0090] In the specific implementation process, the optical transmitter 301 is responsible for generating and transmitting the signal under test. The optical transmitter 301 first acquires the initial subcarrier signal, using a 16QAM modulation format and containing a known bit stream to ensure the accuracy and reliability of the measurement. Subsequently, the signal enters a preprocessing stage, performing a zero-filling upsampling operation. This increases the signal's sampling rate by inserting zero-value samples, making the signal more sparse in the frequency domain. Next, the signal undergoes pulse shaping through a root-raised cosine filter with a roll-off factor of 0.1 to optimize the signal's spectral characteristics, reduce out-of-band radiation, and maintain signal integrity. The preprocessed subcarrier signal is then frequency-shifted to various test regions, forming multiple signals under test.

[0091] The optical receiver 302 is equipped with a photodetector with a preset bandwidth, which is slightly larger than the frequency band corresponding to the signal under test, to ensure effective capture of signal strength information. The photodetector converts the received optical signal into an electrical signal.

[0092] The data processing module 303 performs analog-to-digital conversion and signal reconstruction. It receives analog signals from the optical receiver and converts them into digital signals using a high-precision analog-to-digital converter. Then, it uses the PhareADMM algorithm to process the digital signals, iteratively updating the phase information and combining it with amplitude information to calculate the frequency response of the optical transmitter 301 in the corresponding test area. This process is repeated until all test signals have been measured, and finally, the measurement results from each area are integrated to form the overall frequency response of the optical transmitter 301.

[0093] The system in this embodiment uses the modulation format and symbol sequence of modern coherent optical communication systems at the transmitting end, eliminating the need to send additional training sequences, thus simplifying the measurement process and reducing operational complexity. Simultaneously, it achieves comprehensive measurement of the frequency response of the optical transmitter 301 using only a single low-bandwidth photodetector, significantly reducing equipment costs and making the overall frequency response measurement system more widely applicable and cost-effective. Through efficient collaboration between modules, the overall frequency response measurement system can complete measurement tasks accurately and quickly.

[0094] The same or similar labels correspond to the same or similar parts;

[0095] The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this application.

[0096] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector, characterized in that, Includes the following steps: S1: Divide the overall frequency response range of the optical transmitter into several test regions, acquire several initial subcarrier signals and preprocess them, and then frequency-shift the preprocessed initial subcarrier signals to each of the test regions to obtain several test signals. S2: A first test signal is emitted using an optical transmitter, and the first test signal is detected using a photodetector with a preset bandwidth at the optical receiver to obtain the detection result; the first test signal is any one of the plurality of test signals; S3: Perform analog-to-digital conversion on the detection results to obtain the corresponding digital signal, and reconstruct the digital signal using the PhareADMM algorithm to obtain the optical transmitter frequency response of the test area corresponding to the first test signal; The iterative update expression for the PhareADMM algorithm is shown below: in, Let be the intermediate variable used for phase update of the reconstructed signal during the iteration of the i-th first measured signal. Let i be the measurement matrix of the first signal to be measured. Let i be the reconstructed signal vector of the i-th first signal to be tested. Let be the estimated vector of the optical transmitter frequency response within the test area corresponding to the i-th first signal to be tested. Let be the Lagrange multiplier corresponding to the i-th first signal to be tested. Let represent the amplitude information of the i-th first signal to be tested, and k be the iteration number index, ranging from 0 to K, where K is a positive integer. The iteration step size, As the stopping criterion for iteration, The Frobenius norm represents the vector. Represents the Hadamah altar; S4: Repeat steps S2 to S3 until all signals to be tested have been transmitted, and obtain the overall frequency response of the optical transmitter.

2. The method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector according to claim 1, characterized in that, In step S1, the preprocessing includes: zero-fill upsampling and pulse shaping.

3. The method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector according to claim 2, characterized in that, The pulse shaping is performed using a root-raised cosine filter.

4. The method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector according to claim 3, characterized in that, The roll-off factor of the root-raised cosine filter is specifically 0.

1.

5. The method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector according to claim 1, characterized in that, In step S1, the initial subcarrier signal is specifically a QAM symbol sequence containing a known bit stream.

6. The method for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector according to claim 1, characterized in that, In step S2, the preset bandwidth of the photodetector is greater than the range of the test area corresponding to the first test signal.

7. A system for measuring the overall frequency response of an optical transmitter based on a low-bandwidth photodetector, characterized in that, It includes an optical transmitter, an optical receiver, and a data processing module; the optical receiver and the data processor are electrically connected. The optical transmitter is used to acquire the initial subcarrier signal and preprocess it, and then frequency-shift the preprocessed initial subcarrier signal to each test area to obtain several test signals. And transmit the signal to be tested; The optical receiver is used to detect the signal to be tested using a photodetector and obtain the detection result. The data processing module is used to perform analog-to-digital conversion on the detection results to obtain the corresponding digital signal, and to reconstruct the digital signal using the PhareADMM algorithm to obtain the corresponding optical transmitter frequency response. The iterative update expression of the PhareADMM algorithm is as follows: in, Let be the intermediate variable used for phase update of the reconstructed signal during the iteration of the i-th first measured signal. Let i be the measurement matrix of the first signal to be measured. Let i be the reconstructed signal vector of the i-th first signal to be tested. Let be the estimated vector of the optical transmitter frequency response within the test area corresponding to the i-th first signal to be tested. Let be the Lagrange multiplier corresponding to the i-th first signal to be tested. Let represent the amplitude information of the i-th first signal to be tested, and k be the iteration number index, ranging from 0 to K, where K is a positive integer. The iteration step size, As the stopping criterion for iteration, The Frobenius norm represents the vector. It represents the Hadamaji.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

9. An electronic device, characterized in that, It includes a processor and a memory, the memory storing computer-readable instructions, which, when executed by the processor, perform the steps of the method as described in any one of claims 1 to 6.

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