A method for measuring polarization response of optical devices

Abstract

The present invention relates to the field of microwave photon measurement technology and discloses a method for measuring the polarization response of an optical device, comprising a frequency sweep source, an optical beam splitter, a frequency shift module, a polarization state generating module, a polarization controller, an optical device to be measured, an optical coupler, a polarization beam splitter, a first photodetector, a second photodetector, a third photodetector, a time delay module, and a receiving module. The method and apparatus for measuring the polarization response of an optical device, combined with optical signal frequency shifting technology and optical vector analysis technology, can directly measure the ratio of Jones vector elements of an optical signal of the optical device, thereby constructing the Jones matrix of the optical device. The present invention can avoid the conversion between the Stokes vector and the Jones vector, or between the Mueller matrix and the Jones matrix, thereby facilitating the measurement of the polarization response of an optical device and the analysis of the polarization performance of an optical path.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave photon measurement, and in particular to a method for measuring polarization response of an optical device. Background Art

[0002] With the recent development of optical information systems, the polarization response of optical devices has become increasingly important in their transmission. For example, polarization-dependent loss (PDL) characterizes the difference in insertion loss across polarization states in next-generation optical information systems and is a key polarization parameter for measuring optical devices. Measuring the polarization response of optical devices supports the development and testing of optical components (including active and passive fiber optic components such as optical amplifiers and optical filters) in next-generation optical information systems, including optical communications, optical sensing, and optical processing.

[0003] To address the problem of measuring the polarization response of optical devices, Jones proposed in 1941 a method to describe the polarization state of an optical signal using the relationship between the projections of the lightwave electric vector on two arbitrary orthogonal polarization bases, known as the Jones matrix method. Methods for measuring the polarization response of optical devices, both domestically and internationally, can be broadly categorized into two types: traditional and modern. The traditional method, the ergodic polarization state method, measures the response of an optical device at each polarization state. The advantages of this method are its simplicity and the lack of calibration requirements. However, its disadvantage is the time required to traverse the polarization state at each wavelength, which is time-consuming and prevents efficient measurement (R., N. and KB Comparison of Optical Polarization-Dependent Loss Measurement Methods. in Photonic Networks; 21st ITG-Symposium. 2020.). To shorten the time required to measure polarization-dependent loss using the ergodic polarization state method, modern measurement methods such as the Mueller matrix method and the Jones matrix eigenvalue method have been proposed. The Jones matrix method is suitable for dealing with coherence issues in polarized light, but the Jones vector is in complex form, making its phase difficult to measure directly. The Stokes space method uses light intensity to describe everything and can be measured directly. It is the main method used in experiments. However, since it deals with the intensity of the light signal, it is not easy to solve the interference problem of the light signal. Therefore, if the Stokes space method is used to obtain the Jones matrix of the optical device to be measured, it is usually necessary to convert the Stokes vector to the Jones vector, or convert the Mueller matrix to the Jones matrix (Xiao Yueyu, Yang Huixiang, Xu Huaibao, et al. Measurement of the Jones matrix under arbitrary orthogonal basis vectors based on Stokes space [J]. Progress in Laser & Optoelectronics, 2016, 53(9): 243-249.). This makes it inconvenient to measure the polarization response of optical devices and analyze the polarization performance of optical paths. Therefore, a method for measuring the polarization response of optical devices is proposed to solve the problems existing in the above background. Summary of the Invention

[0004] To achieve the above object, the present invention provides the following technical solution: a method for measuring the polarization response of an optical device, comprising the following steps:

[0005] Step 1: First, the optical signal output by the frequency sweep source is divided into two paths, entering the measurement system and the compensation system respectively;

[0006] Step 2: Calibrate the measurement system: Split the optical signal input to the measurement system into two signals, perform frequency shift processing on the first signal to obtain a frequency-shifted optical signal, and sequentially pass the second optical signal through the polarization controller 2 and the polarization state generating module. Set the polarization state of the output optical signal of the polarization state generating module to 45°, then adjust the polarization controller 2 so that the signal power at the two output ports of the polarization beam splitter is equal. Photodetector 1 and photodetector 2 respectively perform photoelectric detection on the signals at the two polarization states output by the polarization beam splitter to obtain calibration signals and their ratios.

[0007] Step 3: Connect the optical device to be measured and adjust the polarization state generating module to generate optical signals with three different polarization states: 0°, 90°, and 45°. Photodetector 1 and photodetector 2 respectively detect the signals in the two polarization states output by the polarization beam splitter to obtain the corresponding measurement signals and their ratios.

[0008] Step 4: The optical signal input to the compensation system is divided into two signals. The first signal passes through the delay module to obtain a delayed optical signal. The delayed optical signal and the second signal are coupled and then enter the photodetector 3 for photoelectric detection to obtain a compensation signal.

[0009] Step 5: The receiving module extracts the amplitude and phase information of the calibration signal and the measurement signal, calculates the element ratios of the Jones vector of the output optical signal of the optical device to be measured under the three input polarization states, constructs the Jones matrix of the optical device to be measured, and then calculates the polarization response of the optical device to be measured, such as polarization-dependent loss and polarization mode dispersion, according to the Jones matrix eigenvalue method;

[0010] Step 6: The receiving module calculates the instantaneous angular frequency of the compensation signal, and then uses the calculated instantaneous angular frequency ωs to replace the instantaneous angular frequency of the calibration signal and the measurement signal output by the measurement system, thereby completing the error compensation of the measurement system and solving the frequency offset problem introduced by the nonlinearity of the frequency modulation of the swept frequency source;

[0011] Step 7: Control the frequency sweep source to generate a linear frequency sweep optical signal.

[0012] Preferably, in step 7, the frequency sweep source repeats steps 1 to 6 at each frequency point to obtain the polarization response of the optical device to be measured within a certain frequency band.

[0013] Preferably, an acousto-optic modulator or a certain length of optical fiber is used as a frequency shift module to generate a frequency-shifted optical signal. An acousto-optic modulator or a certain length of optical fiber is used as a frequency shift module to generate a frequency-shifted optical signal.

[0014] Preferably, a polarization state generating module is used to generate optical signals with different polarization states.

[0015] Preferably, in the compensation system, an optical fiber of a certain length is used as a delay module. In the compensation system, an optical fiber of a certain length is used as a delay module.

[0016] An optical device polarization response measurement device includes a swept frequency source, an optical beam splitter, a frequency shift module, a polarization state generation module, a polarization controller, an optical device to be measured, an optical coupler, a polarization beam splitter, a first photodetector, a second photodetector, a third photodetector, a time delay module, and a receiving module, wherein:

[0017] Sweep frequency source, used to output linear frequency modulation continuous wave signal;

[0018] The optical beam splitter is used to split the input optical signal into two optical signals according to a certain ratio;

[0019] The frequency shift module is used to apply a fixed frequency shift to one of the optical signals output by the optical beam splitter 2 in the measurement system;

[0020] A polarization state generating module, used to generate polarized light signals of different polarization states;

[0021] A polarization controller, used to control or adjust the polarization state of an optical signal;

[0022] Optical coupler, used to couple two different optical signals into one optical signal;

[0023] Polarization beam splitter, used to decompose polarized light signals into two output ports with orthogonal polarization states;

[0024] a first photodetector, configured to photoelectrically detect an output signal from the polarization beam splitter S, and output a calibration signal and a measurement signal having a frequency identical to the frequency shift amount of the frequency shift module;

[0025] a second photodetector, configured to photoelectrically detect an output signal from the p-end of the polarization beam splitter, and output a calibration signal and a measurement signal having a frequency identical to the frequency shift amount of the frequency shift module;

[0026] a third photoelectric detector, configured to perform photoelectric detection on the compensation branch signal and output a compensation signal with a frequency related to the delay module;

[0027] The delay module is used to generate an optical signal with a certain delay;

[0028] The receiving module is used to extract the amplitude and phase information of the output signals of the first and second photoelectric detectors, and perform signal processing on the output signal of the third photoelectric detector.

[0029] Preferably, the frequency shift module may be an acousto-optic modulator, or an optical fiber of a certain length.

[0030] Preferably, the receiving module may be a vector network analyzer or an oscilloscope.

[0031] Preferably, the delay module may be an optical fiber of a certain length.

[0032] Compared with the prior art, the present invention provides a method for measuring the polarization response of an optical device, which has the following beneficial effects:

[0033] 1. This method and apparatus for measuring the polarization response of optical devices, combining optical signal frequency shifting technology with optical vector analysis techniques, can directly measure the ratio of Jones vector elements in an optical device's optical signal, thereby constructing the device's Jones matrix. This invention avoids the conversion between the Stokes vector and the Jones vector, or between the Mueller matrix and the Jones matrix, facilitating the measurement of optical device polarization response and the analysis of optical path polarization performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The figure is a schematic structural diagram of a specific embodiment of the optical device polarization response measurement device of the present invention. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment is a specific implementation of a method for measuring polarization response of an optical device.

[0038] See also Figure 1-1 A method for measuring the polarization response of an optical device comprises the following steps:

[0039] Step 1: First, the optical signal output by the frequency sweep source is divided into two paths, entering the measurement system and the compensation system respectively;

[0040] Step 2: Calibrate the measurement system: Split the optical signal input to the measurement system into two signals, perform frequency shift processing on the first signal to obtain a frequency-shifted optical signal, and sequentially pass the second optical signal through the polarization controller 2 and the polarization state generating module. Set the polarization state of the output optical signal of the polarization state generating module to 45°, then adjust the polarization controller 2 so that the signal power at the two output ports of the polarization beam splitter is equal. Photodetector 1 and photodetector 2 respectively perform photoelectric detection on the signals at the two polarization states output by the polarization beam splitter to obtain calibration signals and their ratios.

[0041] Step 3: Connect the optical device to be measured and adjust the polarization state generating module to generate optical signals with three different polarization states: 0°, 90°, and 45°. Photodetector 1 and photodetector 2 respectively detect the signals in the two polarization states output by the polarization beam splitter to obtain the corresponding measurement signals and their ratios.

[0042] Step 4: The optical signal input to the compensation system is divided into two signals. The first signal passes through the delay module to obtain a delayed optical signal. The delayed optical signal and the second signal are coupled and then enter the photodetector 3 for photoelectric detection to obtain a compensation signal.

[0043] Step 5: The receiving module extracts the amplitude and phase information of the calibration signal and the measurement signal, calculates the element ratios of the Jones vector of the output optical signal of the optical device under test under the three input polarization states, constructs the Jones matrix of the optical device under test, and then calculates the polarization response of the optical device under test, such as polarization-dependent loss and polarization mode dispersion, according to the Jones matrix eigenvalue method;

[0044] Step 6: The receiving module calculates the instantaneous angular frequency of the compensation signal, and then uses the calculated instantaneous angular frequency ωs to replace the instantaneous angular frequency of the calibration signal and the measurement signal output by the measurement system, thereby completing the error compensation of the measurement system and solving the frequency offset problem introduced by the nonlinearity of the frequency modulation of the swept frequency source;

[0045] Step 7: Control the frequency sweep source to generate a linear frequency sweep optical signal.

[0046] Through the above-mentioned technical solution, the present invention combines optical signal frequency shifting technology and RF signal optical vector analysis technology to measure the polarization response of optical devices. Specifically, the optical signal with a frequency of ωs output by a swept frequency source is first split into two paths, which enter the measurement system and compensation system respectively. The operating principle of the measurement system is as follows: the input optical signal is first split into two signals. The first signal is frequency shifted by an amount of ∆ω to obtain a frequency-shifted optical signal with a frequency of ωs-∆ω. The second optical signal passes through the polarization controller 2 and the polarization state generation module in sequence, setting the polarization state of the output optical signal of the polarization state generation module to 45°. The polarization controller 2 is then adjusted to equalize the signal power at the two output ports of the polarization beam splitter. Photodetectors 1 and 2 respectively detect the signals at the two polarization states output by the polarization beam splitter to obtain calibration signals and their ratios. The optical device to be measured is then connected, and the polarization state generation module is adjusted to generate optical signals with three different polarization states: 0°, 90°, and 45°. Photodetectors 1 and 2 respectively detect the signals at the two polarization states output by the polarization beam splitter to obtain corresponding measurement signals and their ratios.

[0047] Specifically, in step 7, the frequency sweep source repeats steps 1 to 6 at each frequency point to obtain the polarization response of the optical device to be measured within a certain frequency band.

[0048] Specifically, an acousto-optic modulator or a certain length of optical fiber is used as a frequency shift module to generate a frequency-shifted optical signal. An acousto-optic modulator or a certain length of optical fiber is used as a frequency shift module to generate a frequency-shifted optical signal.

[0049] Specifically, a polarization state generating module is used to generate optical signals with different polarization states.

[0050] Specifically, in the compensation system, a certain length of optical fiber is used as a delay module. In the compensation system, a certain length of optical fiber is used as a delay module.

[0051] Example 2

[0052] This embodiment is a specific implementation of a device for measuring polarization response of an optical device.

[0053] An optical device polarization response measurement device includes a swept frequency source, an optical beam splitter, a frequency shift module, a polarization state generation module, a polarization controller, an optical device to be measured, an optical coupler, a polarization beam splitter, a first photodetector, a second photodetector, a third photodetector, a time delay module, and a receiving module, wherein:

[0054] Sweep frequency source, used to output linear frequency modulation continuous wave signal;

[0055] The optical beam splitter is used to split the input optical signal into two optical signals according to a certain ratio;

[0056] The frequency shift module is used to apply a fixed frequency shift to one of the optical signals output by the optical beam splitter 2 in the measurement system;

[0057] A polarization state generating module, used for generating polarized light signals with two perpendicular polarization states;

[0058] A polarization controller, used to control or adjust the polarization state of an optical signal;

[0059] Optical coupler, used to couple two different optical signals into one optical signal;

[0060] Polarization beam splitter, used to decompose polarized light signals into two output ports with orthogonal polarization states;

[0061] A first photodetector is used to photoelectrically detect the output signal of the polarization beam splitter S end, and output a calibration signal and a measurement signal having the same frequency as the frequency shift amount of the frequency shift module;

[0062] The second photodetector is used to photoelectrically detect the output signal of the p-end of the polarization beam splitter, and output a calibration signal and a measurement signal with the same frequency as the frequency shift amount of the frequency shift module;

[0063] a third photoelectric detector, configured to perform photoelectric detection on the compensation branch signal and output a compensation signal with a frequency related to the delay module;

[0064] The delay module is used to generate an optical signal with a certain delay;

[0065] The receiving module is used to extract the amplitude and phase information of the output signals of the first and second photoelectric detectors, and perform signal processing on the output signal of the third photoelectric detector.

[0066] Specifically, the frequency shift module may be an acousto-optic modulator or an optical fiber of a certain length.

[0067] Specifically, the receiving module may be a vector network analyzer or an oscilloscope.

[0068] Specifically, the delay module may be an optical fiber of a certain length.

[0069] Example 3

[0070] This embodiment is a specific implementation of the working principle of the compensation system.

[0071] The working principle of the compensation system includes the following steps:

[0072] Step 1: First, the input optical signal is divided into two signals. The first signal passes through the delay module to obtain a delayed optical signal. The delayed optical signal and the second signal are coupled and enter the photodetector 3 for photoelectric detection to obtain a compensation signal.

[0073] Step 2: The receiving module extracts the amplitude and phase information of the calibration signal and the measurement signal, calculates the element ratio of the Jones vector of the optical signal output by the optical device under test, constructs the Jones matrix of the optical device under test, and then calculates the polarization response of the optical device under test, such as polarization-dependent loss and polarization mode dispersion, using the Jones matrix eigenvalue method;

[0074] Step 3: At the same time, the receiving module processes the compensation signal, which can effectively solve the measurement error introduced by the nonlinearity of the frequency sweep source and improve the accuracy of the measurement system.

[0075] Example 4

[0076] This embodiment is a specific implementation of the working principle of the measurement system.

[0077] The working principle of the measurement system includes the following steps:

[0078] Step 1: First, the input optical signal is divided into two signals. The first signal is frequency shifted by ∆ω to obtain a frequency-shifted optical signal with a frequency of ωs-∆ω.

[0079] Step 2: The second optical signal passes through the polarization controller 2 and the polarization state generating module in sequence. The polarization state of the output optical signal of the polarization state generating module is set to 45°. The polarization controller 2 is then adjusted to make the signal power at the two output ports of the polarization beam splitter equal. The photodetector 1 and the photodetector 2 respectively perform photoelectric detection on the signals at the two polarization states output by the polarization beam splitter to obtain the calibration signal and its ratio.

[0080] Step 3: Then connect the optical device to be measured and adjust the polarization state generating module to generate optical signals with three different polarization states of 0°, 90°, and 45°. Photodetector 1 and photodetector 2 respectively perform photoelectric detection on the signals at the two polarization states output by the polarization beam splitter to obtain the corresponding measurement signals and their ratios.

[0081] Example 5

[0082] This embodiment is a further specific implementation of the measurement principle.

[0083] The measurement principle includes the following steps:

[0084] Step 1: First, the working principle of the measurement system is introduced: Assume that the angular frequency of the swept optical signal input to the measurement system by the swept frequency source is ωs, then the expression of the two signals after passing through the optical beam splitter 2 is:

[0085]

[0086] Where, Ac is the amplitude of the swept optical signal;

[0087] Step 2: The frequency shift module applies a fixed frequency shift of ∆ω to the first frequency-sweep optical signal, generating a frequency-shifted optical signal with an angular frequency of ωs − ∆ω. The frequency-shifted optical signal can be expressed as:

[0088]

[0089] Where Afs is the amplitude of the signal;

[0090] Step 3: Using the two orthogonal polarization axes (fast axis and slow axis) s and p of the polarization beam splitter as the reference coordinate system, the Jones vector of the optical signal after passing through the polarization state generator module is:

[0091]

[0092] Where As and Ap represent the amplitude changes of the optical signal input to the optical device under test projected on the s and p axes, respectively. φs and φp represent the projected phase changes, respectively.

[0093] Step 4: Assume that the Jones vector of the signal passing through the optical device to be measured is:

[0094]

[0095] Where As,out and Ap,out represent the amplitude changes of the output optical signal projected on the s and p axes, respectively. φs,out and φp,out represent the projected phase changes, respectively.

[0096] Step 5: Adjust the polarization controller 1 so that the signal powers at the two output ports of the polarization beam splitter are equal. At this time, the Jones vector of the output signal of the polarization controller 1 is:

[0097]

[0098] Where Asfs and Apfs represent the amplitude changes of the optical signal projected on the s and p axes, respectively. φsfs and φpfs represent the projected phase changes, respectively. The expression of the signal coupled into the polarization beam splitter is:

[0099]

[0100] Step 6: The output signals on the two polarization axes s and p of the polarization beam splitter are photodetected by photodetector 1 and photodetector 2 respectively. The photocurrent component with a frequency of Δω in the output current signal is extracted as the measurement signal. The corresponding signal expression is:

[0101]

[0102]

[0103] Wherein, η1(Δω) and η2(Δω) are the frequency responses of photodetector 1 and photodetector 2 at a frequency of Δω.

[0104] Step 7: Under calibration, that is, remove the optical device to be tested, set the polarization state of the output optical signal of the polarization state generator module to 45°, and then adjust the polarization controller 2 to make the signal power at the two output ports of the polarization beam splitter equal. At this time, the Jones vector of the optical signal input to the optical device to be tested has the following relationship:

[0105]

[0106] At this time, the expression of the calibration signal under the two polarization axes s and p of the polarization beam splitter is:

[0107]

[0108]

[0109] According to the formula, the ratio expression of the calibration signal under the two polarization axes s and p of the polarization beam splitter can be deduced as follows:

[0110]

[0111] Therefore, the ratio k of the two elements of the Jones vector of the optical signal output from the optical device to be measured can be expressed as:

[0112]

[0113] Because the Jones vector of the optical signal input to the optical device under test is known, a vector network analyzer (VNA) can be used as a receiving module to dynamically extract the amplitude and phase information of the measurement and calibration signals. Alternatively, an oscilloscope can be used as a receiving module to offline process the amplitude and phase information of the photocurrent (Δω) output by the two photodetectors. This allows the ratio of the two elements of the Jones vector of the optical signal output from the optical device under test to be calculated. Compared to using a VNA as a receiving module, using an oscilloscope as a receiving module for offline processing of experimental data provides faster measurement speeds and better results.

[0114] Step 8: Adjust the polarization state generating module to change the polarization state of the optical signal input to the optical device to be measured, so as to obtain different ratios of the two elements of the Jones vector of the optical signal output from the optical device to be measured.

[0115] Assume that the Jones vector of the optical signal with polarization states of 0°, 90°, and 45° input to the optical device to be measured is:

[0116]

[0117]

[0118]

[0119] Then the ratios of the two elements of the Jones vectors of the corresponding three output optical signals are:

[0120]

[0121]

[0122]

[0123] Use k1, k2, k3 to perform the following complex number operations:

[0124]

[0125] Then at the frequency point ωs, the Jones matrix of the optical device to be measured can be expressed as:

[0126]

[0127] Where c is an unknown complex constant.

[0128] Step 9: According to the Jones matrix eigenvalue method, the polarization parameter theory of the optical device is measured. Multiply the Jones matrix by its own conjugate transpose to obtain:

[0129]

[0130] Here, "H" means conjugate transpose.

[0131] Then, the polarization-dependent loss of the optical device to be measured can be written as

[0132]

[0133] Among them, r1(ω) and r2(ω) are the two eigenvalues ​​of the matrix M (ωs).

[0134] Step 10: Construct the following matrix based on the Jones transmission matrix at different wavelengths of the optical device to be measured

[0135]

[0136] Where ∆ωs is the difference in angular frequency between the two measured signals, and H-1(ωs) is the inverse matrix of H(ωs).

[0137] Step 11: The differential group delay (DGD) can be calculated according to the formula and can be expressed as

[0138]

[0139] Where ρ1(ω) and ρ2(ω) are the two eigenvalues ​​of the matrix Γ(ω). The polarization mode dispersion of the optical device under test can be obtained by taking the root mean square of the differential group delay at each frequency point within the measurement range.

[0140] Step 12: The error elimination principle of the compensation system is introduced below: Assume that the instantaneous angular frequency of the frequency-modulated continuous wave output by the sweep source is ωs(t),

[0141] Its signal expression is:

[0142]

[0143] Since swept frequency sources typically exhibit FM nonlinearity—that is, the linear FM slope k is not constant—there is a discrepancy between the instantaneous frequency at each sampling point in the measurement system and the instantaneous frequency determined by multiplying the FM slope by time. Therefore, knowing the true instantaneous frequency corresponding to each sampling point is necessary to obtain a correct frequency response. To address the FM nonlinearity issue of FM continuous waves, a compensation system is used to obtain the true instantaneous frequency of the FM continuous wave.

[0144] Assume that the angular frequency of the swept frequency optical signal input into the compensation system is ωs(t), and assume that the delay introduced by the delay module is τ, then the beat frequency signal generated by the photodetector 3 is:

[0145]

[0146] Where E0 is the amplitude of the beat signal, and ωs(t) is the instantaneous angular frequency of the frequency modulated continuous wave, which can be obtained by performing Hilbert transform on the beat signal.

[0147] The expression of Hilbert transform is:

[0148]

[0149] So the Hilbert transform of the beat frequency signal is:

[0150]

[0151] Step 13: The phase of the beat frequency signal generated by the photodetector 2 can be obtained by the formula and:

[0152]

[0153] From this, the instantaneous frequency of the FMCW can be obtained as:

[0154]

[0155] By replacing the angular frequencies of the reference signal and the measurement signal output by the measurement system with the instantaneous angular frequency calculated by the formula, the error compensation of the measurement system can be completed, thereby solving the frequency offset problem introduced by the nonlinearity of the frequency modulation of the swept frequency source.

[0156] In summary, the present invention can achieve high-precision measurement of polarization responses such as polarization response, amplitude response and phase response of optical devices.

[0157] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring polarization response of an optical device, characterized by: The steps include: Step 1: First, the optical signal output by the frequency sweep source is divided into two paths, entering the measurement system and the compensation system respectively; Step 2, calibrate the measurement system: divide the optical signal input to the measurement system into two signals, perform frequency shift processing on the first signal to obtain a first frequency-shifted optical signal, the first frequency-shifted optical signal passes through the polarization controller 1, and then enters the optical coupler 1, adjust the polarization controller 1 so that the signal power of the two output ports of the polarization beam splitter is equal, the second optical signal passes through the polarization controller 2 and the polarization state generating module in sequence, and the polarization state of the output optical signal of the polarization state generating module is set to 45°, the second optical signal passes through the optical coupler 1, and then enters the polarization beam splitter, and then adjust the polarization controller 2 so that the signal power of the two output ports of the polarization beam splitter is equal, the photodetector 1 and the photodetector 2 respectively perform photoelectric detection on the signals on the two polarization states output by the polarization beam splitter to obtain a calibration signal and its ratio, and the optical coupler 1 couples the two differently processed optical signals into one optical signal; Step 3: Connect the optical device to be measured and adjust the polarization state generating module to generate optical signals with three different polarization states: 0°, 90°, and 45°. Photodetector 1 and photodetector 2 respectively detect the signals in the two polarization states output by the polarization beam splitter to obtain the corresponding measurement signals and their ratios. Step 4: The optical signal input to the compensation system is divided into two signals. The first signal passes through the delay module to obtain a delayed optical signal. The delayed optical signal and the second signal are coupled and then enter the photodetector 3 for photoelectric detection to obtain a compensation signal. Step 5: The receiving module extracts the amplitude and phase information of the calibration signal and the measurement signal, calculates the element ratios of the Jones vector of the output optical signal of the optical device to be measured under the three input polarization states, constructs the Jones matrix of the optical device to be measured, and then calculates the polarization-dependent loss and polarization mode dispersion polarization response of the optical device to be measured according to the Jones matrix eigenvalue method; Step 6: The receiving module calculates the instantaneous angular frequency of the compensation signal, and then uses the calculated instantaneous angular frequency ωs to replace the instantaneous angular frequency of the calibration signal and the measurement signal output by the measurement system, thereby completing the error compensation of the measurement system and solving the frequency offset problem introduced by the nonlinearity of the frequency modulation of the swept frequency source; Step 7: Control the frequency sweep source to generate a linear frequency sweep optical signal.

2. The method for measuring polarization response of an optical device according to claim 1, wherein: In step 7, the frequency sweep source repeats steps 1 to 6 at each frequency point to obtain the polarization response of the optical device to be measured within a certain frequency band.

3. The method for measuring polarization response of an optical device according to claim 1, wherein: An acousto-optic modulator or a certain length of optical fiber is used as a frequency shift module to generate a frequency-shifted optical signal.

4. The method for measuring polarization response of an optical device according to claim 1, wherein: Use the polarization state generation module to generate optical signals with different polarization states.

5. The method for measuring polarization response of an optical device according to claim 1, wherein: In the compensation system, an optical fiber of a certain length is used as a delay module.

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