Polarization-controlled optical device high-precision vector measurement device and method

Abstract

The invention belongs to the technical field of photoelectric detection, and discloses a polarization-controlled optical device high-precision vector measurement device and method. The device comprises a sweep frequency microwave source module, a laser source module, a bias voltage module, a dual-polarization Mach-Zehnder modulator module, a polarization control module, a device to be detected, a photoelectric detector, a microwave amplitude phase receiving module and a control and data processing module. The laser source module is connected with the dual-polarization Mach-Zehnder modulator module; the sweep frequency microwave source module is respectively connected with the dual-polarization Mach-Zehnder modulator module and the microwave amplitude phase receiving module; the bias voltage module is connected with the dual-polarization Mach-Zehnder modulator module; the dual-polarization Mach-Zehnder modulator module, the polarization control module, the device to be detected, the photoelectric detector, the microwave amplitude phase receiving module and the data processing module are connected in sequence. According to the invention, high-precision measurement can be carried out on the frequency response of the to-be-measured optical device, and the limitation of setting a small modulation index is overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic detection, and in particular, to a high-precision vector measurement device and method for a polarization-controlled optical device. Background Art

[0002] At present, with the integration and development of optical information devices and optoelectronic information devices, high-precision and high-resolution frequency response measurement plays an important role in the characterization, manufacturing, and maintenance of optical devices and photonic integrated circuits. Innovations and major breakthroughs in scientific frontiers such as single-molecule detection, slow light storage, and on-chip optical signal processing based on ultra-high-precision metrology urgently require high-precision and high-resolution frequency response measurement instruments as testing means. During the research, production, and application processes of optical information devices and optoelectronic information devices, it is necessary to accurately measure their frequency responses (including amplitude, phase, and polarization responses) to accurately characterize their performance.

[0003] Therefore, frequency response (amplitude response, phase response) measurement is an important means for the research, production, and potential application research of modern optical information devices and optoelectronic information devices. High-precision spectral analysis methods and measurement instruments for optical devices have become the key to the development of core optical integrated chips and related frontier scientific research. However, with more refined design and manufacturing, some optical devices have characteristics such as high Q value and narrow linewidth, and it is difficult for optical vector analysis techniques based on optical interference methods and traditional optical vector analysis techniques based on microwave modulation signal scanning to measure their frequency responses with higher precision. Therefore, it is urgent to introduce higher-precision frequency response measurement techniques to replace traditional low-precision measurements. Currently, a large amount of research has been conducted on high-precision frequency response measurement of optical devices at home and abroad.

[0004] For the currently proposed optical device frequency response measurement techniques, according to the characteristics of light sources and the signal processing methods adopted, the methods at home and abroad are roughly divided into the following two categories: The first category is the optical vector analysis technique based on optical interference methods; the other category is mainly the optical vector analysis technique based on single-sideband modulation.

[0005] Appendix Figure 1It is a schematic block diagram of a typical commercial optical vector analyzer. The optical carrier output by the tunable laser passes through the first Mach-Zehnder interferometer. By adjusting the polarization controller in the interference arm, the polarization state of the output optical signal is made orthogonal. Then it passes through the second Mach-Zehnder interferometer, and an optical device under test is cascaded in one of the interference arms. This path serves as the measurement path, and the transmitted optical carrier will be affected by the polarization-dependent loss and phase shift caused by the optical device under test. The output optical signal carries the amplitude and phase information of the optical device under test. The other interference arm is not cascaded with any device and serves as the reference path. The polarization beam splitter separates the two orthogonally polarized lights into two paths, and photoelectric conversion is carried out using two photodetectors respectively, and the currents of the orthogonally polarized states are received, then the frequency response (amplitude response, group delay, polarization mode dispersion) of the optical device under test can be obtained.

[0006] The advantages of this method lie in its relatively simple structure and high precision, and it can directly reflect and measure the frequency response of optical devices on the all-optical optical vector network analysis system.

[0007] The deficiencies of this scheme are mainly manifested in:

[0008] This scheme is a laser frequency-sweeping tuning mechanism. Limited by the low wavelength accuracy and poor stability of the wavelength-scanning laser source, the resolution of this method is relatively limited, only at the pm level, the measurement accuracy is low, the measurement range is relatively narrow, and it cannot characterize the frequency response of optical devices with fine structures below MHz. At the same time, the phase response of the optical device under test is extracted and processed through optical coherence technology, which is extremely sensitive to external environmental influences. Therefore, an additional stable loop is required to ensure the normal operation of the optical vector analyzer, increasing the complexity of the measurement system and the device cost.

[0009] The optical vector analysis technology based on microwave photon technology is an emerging technology that combines microwave technology and photon technology. Through electro-optic modulation, the wavelength-scanning method carried out in the optical domain is transferred to the electrical domain, and by using high-precision electrical spectrum scanning and response analysis technology, this technology has the advantages of high resolution, high precision, and large dynamic range.

[0010] Appendix Figure 2It is a schematic diagram of the principle of a typical optical vector analysis system based on single-sideband modulation. The optical carrier output by the tunable laser generates sideband signals of each order through the electro-optic modulator, and the modulation frequency is generated under the control of the swept radio frequency signal source. By filtering out the sideband signals other than the optical carrier and the first-order sideband signal through the optical filter, an ideal optical single-sideband modulation signal is obtained as the measurement signal. After the first-order modulated optical sideband signal passes through the optical device under test, its amplitude and phase will change according to the amplitude and phase response of the device under test. After square-law detection by the photodetector, photoelectric conversion is realized, and the optical signal carrying the amplitude and phase information of the optical device under test is converted into an optical current. By setting, the phase-amplitude detector only receives the signal with the same frequency as the reference microwave signal, and the frequency response of the optical device under test can be measured.

[0011] The outstanding advantage of this measurement method lies in its high measurement resolution. It converts the scanning process of the optical frequency into the scanning of the electrical frequency, and uses the high precision of the electrical frequency to achieve a huge improvement in the measurement resolution. Currently, the highest resolution has reached 78 kHz. At the receiving end, by receiving the optical domain intensity, the frequency response of the optical device under test is converted into the amplitude and phase in the electrical domain, which not only improves the receiving accuracy, but also makes the phase-frequency response test possible, providing a more in-depth detailed analysis ability for optical signal analysis.

[0012] The deficiencies of this scheme are mainly manifested in:

[0013] 1. Large measurement error. The optical filter has a limited cosine roll-off characteristic and cannot accurately remove the residual sidebands. The measurement errors introduced by the beat frequency of the residual sidebands of the +1 order sideband of the single-sideband modulation and the beat frequency between the residual high-order sidebands are inevitable. And when measuring the band-stop optical device, the measurement error introduced by the residual first-order sideband is close to or even greater than the actual frequency response of the optical device under test, and the stopband depth cannot be accurately obtained, so the measurement error is large. The optical filter (such as WaveShaper, 90° and 120° hybrid coupler or Hilbert transformer, etc.) has a limited working bandwidth and cosine roll-off characteristic, and cannot accurately remove the residual sidebands. The measurement errors introduced by the beat frequency of the residual sidebands of the +1 order sideband of the single-sideband modulation and the beat frequency between the residual high-order sidebands are inevitable. Using the stimulated Brillouin scattering effect, its nonlinear effect cannot perfectly suppress the residual sideband signal. When measuring the band-stop optical device, the measurement error introduced by the residual first-order sideband is close to or even greater than the actual optical frequency response of the optical device under test, and the stopband depth cannot be accurately obtained, so the measurement error is large.

[0014] 2. Small measurement dynamic range. Limited by the nonlinear effect of the electro-optic modulator, in order to avoid generating high-order sidebands, a small modulation index is often set to obtain an ideal optical single-sideband modulation signal. The sideband suppression ratio of the obtained optical single-sideband modulation signal is small, resulting in a limited measurement dynamic range. Therefore, the frequency response of the larger notch depth part of the optical device under test cannot be accurately measured. Summary of the Invention

[0015] The purpose of the present invention is to disclose a high-precision vector measurement device and method for a polarization-controlled optical device, so as to solve the technical problems proposed in the background art.

[0016] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0017] In the first aspect, the present invention provides a high-precision vector measurement device for a polarization-controlled optical device, including a swept-frequency microwave source module, a laser source module, a bias voltage module, a dual-polarization Mach-Zehnder modulator module, a polarization control module, a device under test, a photodetector, a microwave amplitude and phase receiving module, and a control and data processing module;

[0018] The laser source module is connected to the dual-polarization Mach-Zehnder modulator module;

[0019] The swept-frequency microwave source module is respectively connected to the dual-polarization Mach-Zehnder modulator module and the microwave amplitude and phase receiving module;

[0020] The bias voltage module is connected to the dual-polarization Mach-Zehnder modulator module;

[0021] The dual-polarization Mach-Zehnder modulator module, the polarization control module, the device under test, the photodetector, the microwave amplitude and phase receiving module, and the data processing module are connected in sequence.

[0022] Preferably, the dual-polarization Mach-Zehnder modulator module includes a first sub-modulator x-MZM, a second sub-modulator y-MZM, a 90° polarization rotator, and a polarization beam combiner;

[0023] The first sub-modulator x-MZM is respectively connected to the laser source module, the swept-frequency microwave source module, the bias voltage module, and the polarization beam combiner;

[0024] The second sub-modulator x-MZM is respectively connected to the laser source module and the 90° polarization rotator;

[0025] The 90° polarization rotator is connected to the polarization beam combiner.

[0026] Preferably, the laser source module is used to input the generated continuous optical carrier signal into the first sub-modulator x-MZM and the second sub-modulator y-MZM respectively.

[0027] Preferably, the swept microwave source module is used to apply a microwave radio frequency swept signal to the first sub-modulator x-MZM; the bias voltage module is used to apply a bias voltage to the first sub-modulator x-MZM, so that the first sub-modulator x-MZM outputs an optical single sideband modulation signal to the polarization beam combiner.

[0028] Preferably, the 90° polarization rotator is used to rotate the polarization state of the signal output by the second sub-modulator y-MZM by 90°, and then output the obtained signal to the polarization beam combiner.

[0029] Preferably, the polarization beam combiner is used to combine the signal output by the first sub-modulator x-MZM and the signal output by the 90° polarization rotator into a polarization multiplexed optical single sideband modulation signal.

[0030] Preferably, the polarization control module is used to process the polarization multiplexed optical single sideband modulation signal and then output a linearly polarized optical single sideband modulation signal to the device under test.

[0031] Preferably, the photodetector is used to convert the optical signal output by the device under test into a photocurrent signal;

[0032] The microwave amplitude and phase receiving module is used to receive the photocurrent signal in the photocurrent signal output by the photodetector that has the same scanning frequency as the microwave radio frequency swept signal generated by the swept microwave source module.

[0033] Preferably, the control and data processing module is used to control the swept microwave source module to apply a microwave radio frequency swept signal to the first sub-modulator x-MZM, and is used to collect and process the amplitude and phase information of the photocurrent signal received and extracted by the microwave amplitude and phase receiving module to obtain the amplitude-phase information of the photocurrent signal.

[0034] In a second aspect, the present invention provides a high-precision vector measurement method for a polarization-controlled optical device, which is applied to the above-mentioned high-precision vector measurement device for a polarization-controlled optical device, and includes:

[0035] The laser source module inputs the generated continuous optical carrier signal into the dual-polarization Mach-Zehnder modulator module;

[0036] The control and data processing module controls the swept microwave source module to apply a microwave radio frequency swept signal to the dual-polarization Mach-Zehnder modulator module;

[0037] The bias voltage module applies a bias voltage to the dual-polarization Mach-Zehnder modulator module;

[0038] The dual-polarization Mach-Zehnder modulator module generates a polarization multiplexed optical single sideband modulation signal based on the continuous optical carrier signal, the microwave radio frequency swept signal, and the bias voltage, and outputs the polarization multiplexed optical single sideband modulation signal to the polarization control module;

[0039] The polarization control module generates a linearly polarized optical single-sideband modulation signal with a phase shift condition of θ1 based on the polarization multiplexed optical single-sideband modulation signal and outputs it to the device under test;

[0040] The photodetector converts the first optical signal output by the device under test into a first photocurrent signal;

[0041] The microwave amplitude and phase receiving module receives the first photocurrent signal in the first photocurrent signal output by the photodetector, which has the same scanning frequency as the microwave radio frequency scanning signal generated by the swept microwave source module;

[0042] The control and data processing module performs data acquisition and processing on the amplitude and phase information extracted by the microwave amplitude and phase receiving module from the received first photocurrent signal to obtain the amplitude-phase information of the first photocurrent signal;

[0043] The polarization control module generates a linearly polarized optical single-sideband modulation signal with a phase shift condition of θ2 based on the polarization multiplexed optical single-sideband modulation signal and outputs it to the device under test, where θ1 and θ2 are different;

[0044] The photodetector converts the second optical signal output by the device under test into a second photocurrent signal;

[0045] The microwave amplitude and phase receiving module receives the second photocurrent signal in the second photocurrent signal output by the photodetector, which has the same scanning frequency as the microwave radio frequency scanning signal generated by the swept microwave source module;

[0046] The control and data processing module performs data acquisition and processing on the amplitude and phase information extracted by the microwave amplitude and phase receiving module from the received second photocurrent signal to obtain the amplitude-phase information of the second photocurrent signal;

[0047] The control and data processing module performs digital processing on the amplitude-phase information of the first photocurrent signal and the amplitude-phase information of the second photocurrent signal respectively to obtain the frequency response of the optical device under test.

[0048] Beneficial effects:

[0049] 1. Compared with the ordinary optical vector analysis method based on optical single-sideband modulation, the polarization control technology is adopted, which can perform high-precision measurement on the frequency response of the device under test under the condition of a large modulation index without sacrificing the measurement dynamic range, further improving the measurement accuracy.

[0050] 2. When measuring the frequency response of a device under test, in order to measure with a large measurement dynamic range, measurements are often carried out under conditions of a large modulation index. Due to the non-linear effect of the electro-optic modulator, the measurement error is relatively large. The present invention uses polarization control technology for secondary measurement, innovatively overcoming the limitation of setting a small modulation index in previous electro-optic modulation to avoid generating high-order sidebands, and providing a reliable technical means for high-precision analysis of the frequency response of the optical device under test. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0052] Figure 1 It is a schematic diagram of a typical commercial optical vector analyzer.

[0053] Figure 2 It is a schematic diagram of a typical optical vector analysis system based on single-sideband modulation.

[0054] Figure 3 It is a schematic diagram of a high-precision vector measurement device for a polarization-controlled optical device of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0056] In the first aspect, as Figure 3 shown in an embodiment, the present invention provides a high-precision vector measurement device for a polarization-controlled optical device, including a swept microwave source module, a laser source module, a bias voltage module, a dual-polarization Mach-Zehnder modulator module, a polarization control module, a device under test, a photodetector, a microwave amplitude and phase receiving module, and a control and data processing module;

[0057] The laser source module is connected to the dual-polarization Mach-Zehnder modulator module;

[0058] The swept microwave source module is respectively connected to the dual-polarization Mach-Zehnder modulator module and the microwave amplitude and phase receiving module;

[0059] The bias voltage module is connected to the dual-polarization Mach-Zehnder modulator module;

[0060] The dual-polarization Mach-Zehnder modulator module, polarization control module, device under test, photodetector, microwave amplitude and phase receiving module, and data processing module are connected in sequence.

[0061] Preferably, the dual-polarization Mach-Zehnder modulator module includes an upper first sub-modulator x-MZM, a second sub-modulator y-MZM, a 90° polarization rotator, and a polarization beam combiner;

[0062] The first sub-modulator x-MZM is respectively connected to the laser source module, the swept microwave source module, the bias voltage module, and the polarization beam combiner;

[0063] The second sub-modulator x-MZM is respectively connected to the laser source module and the 90° polarization rotator;

[0064] The 90° polarization rotator is connected to the polarization beam combiner.

[0065] Preferably, the laser source module is used to input the generated continuous optical carrier signal into the first sub-modulator x-MZM and the second sub-modulator y-MZM respectively.

[0066] Preferably, the swept microwave source module is used to apply a microwave radio frequency swept signal to the first sub-modulator x-MZM; the bias voltage module is used to apply a bias voltage to the first sub-modulator x-MZM, so that the first sub-modulator x-MZM outputs an optical single sideband modulation signal to the polarization beam combiner.

[0067] Preferably, the 90° polarization rotator is used to rotate the polarization state of the signal output by the second sub-modulator y-MZM by 90°, and then output the obtained signal to the polarization beam combiner.

[0068] Preferably, the polarization beam combiner is used to combine the signal output by the first sub-modulator x-MZM and the signal output by the 90° polarization rotator into a polarization multiplexed optical single sideband modulation signal.

[0069] To improve the dynamic range of the optical vector measurement system, it is set that the amplitude of the radio frequency swept signal applied to the upper arm of the modulator, that is, the first sub-modulator x-MZM, is a relatively large voltage value, ensuring measurement with a large modulation index.

[0070] At this time, the upper arm of the modulator obtains an optical single sideband modulation signal, and the lower arm obtains an unmodulated optical carrier signal. After being combined by the polarization beam combiner built in the modulator, a polarization multiplexed single sideband modulation signal with orthogonal polarization state components is obtained.

[0071] Preferably, the polarization control module is used to process the polarization multiplexed optical single sideband modulation signal and then output a linearly polarized optical single sideband modulation signal to the device under test.

[0072] Preferably, the polarization control module includes a polarization controller and a polarizer;

[0073] The input end of the polarization controller is connected to the polarization beam combiner, and the output end is connected to the polarizer;

[0074] The output end of the polarizer is connected to the device under test.

[0075] Preferably, the photodetector is used to convert the optical signal output by the device under test into an optical current signal;

[0076] The microwave amplitude and phase receiving module is used to receive the optical current signal in the optical current signal output by the photodetector, which has the same scanning frequency as the microwave radio frequency scanning signal generated by the frequency-swept microwave source module.

[0077] Preferably, the control and data processing module is used to control the frequency-swept microwave source module to apply a microwave radio frequency scanning signal to the first sub-modulator x-MZM, and is used to perform data acquisition and processing on the amplitude and phase information of the optical current signal received and extracted by the microwave amplitude and phase receiving module, so as to obtain the amplitude-phase information of the optical current signal.

[0078] The function of the microwave amplitude and phase receiving module is to screen out and receive the optical current signal that has the same scanning frequency as the microwave radio frequency scanning signal generated by the frequency-swept microwave source module, then extract the amplitude and phase information of the optical current signal, and transmit it to the control and data processing module.

[0079] In the process of converting the wavelength scanning in the optical domain to the electrical domain in the present invention, a dual-polarization Mach-Zehnder modulator is adopted to obtain a polarization multiplexed optical single-sideband modulation signal with orthogonal polarization state components; through the combined action of the polarization control module composed of a polarization controller and a polarizer, a linearly polarized optical single-sideband modulation signal with different phase shifts is obtained, and the optical device under test is measured with this signal, and the two measurement results are processed to obtain the accurate frequency response of the device under test. Through polarization control, the present invention can eliminate the measurement error caused by the beat frequency between the sideband signals of each order, and can achieve high-precision measurement of the frequency response of optical devices; in addition, the present invention is no longer limited by the need to set a small modulation index for the modulator, and can achieve a larger measurement range. Compared with the prior art, the present invention can measure the frequency response of the optical device to be measured with higher precision and a larger dynamic measurement range.

[0080] In a second aspect, the present invention also provides a high-precision vector measurement method for a polarization-controlled optical device, which is applied to the above-mentioned high-precision vector measurement device for a polarization-controlled optical device, and includes:

[0081] The laser source module inputs the generated continuous optical carrier signal into the dual-polarization Mach-Zehnder modulator module;

[0082] The control and data processing module controls the swept-frequency microwave source module to apply a microwave radio frequency swept-frequency signal to the dual-polarization Mach-Zehnder modulator module;

[0083] The bias voltage module applies a bias voltage to the dual-polarization Mach-Zehnder modulator module;

[0084] The dual-polarization Mach-Zehnder modulator module generates a polarization multiplexed optical single sideband modulation signal based on a continuous optical carrier signal, a microwave radio frequency swept-frequency signal, and a bias voltage, and outputs the polarization multiplexed optical single sideband modulation signal to the polarization control module;

[0085] Specifically, an optical single sideband modulation signal E x-MZM (t) is obtained in the upper branch (x-MZM branch) inside the dual-polarization Mach-Zehnder modulator, and an unmodulated optical carrier E y-MZM (t) is obtained in the lower branch (y-MZM branch), which can be respectively expressed as:

[0086]

[0087]

[0088] Among them, E0 is the amplitude of the continuous optical carrier signal generated by the laser source module, ω c , ω m are respectively the angular frequencies of the optical carrier and the microwave radio frequency swept-frequency signal, and A n is the complex amplitude of the nth-order sideband.

[0089] The unmodulated optical carrier in the lower branch is subjected to a 90° polarization rotator, and its polarization state rotates by 90°. At this time, the polarization state components of the signals in the upper and lower branches are orthogonal to each other. Then the two signals pass through the built-in polarization beam combiner to merge into a polarization multiplexed optical single sideband modulation signal E DPol-MZM (t), which is expressed as:

[0090]

[0091] Among them, and are two orthogonal polarization directions.

[0092] The control polarization control module generates a linearly polarized optical single sideband modulation signal with a phase shift condition of θ1 based on the polarization multiplexed optical single sideband modulation signal and outputs it to the device under test;

[0093] By setting the last quarter-wave plate of the polarization controller, a linearly polarized optical single sideband modulation signal with a phase shift condition of θ1 is obtained.

[0094] Specifically, the polarization control module consists of a polarization controller and a polarizer. By adjusting the last quarter-wave plate of the polarization controller, a phase shift θ is introduced between the mutually orthogonal polarization state components of the polarization multiplexed optical single-sideband modulation signal. By adjusting the half-wave plate of the polarization controller, the angle α between the polarization multiplexed signal after the phase shift is introduced and the polarizer is set to 45°. The mutually orthogonal polarization state components will be combined into one polarization state component to obtain a linearly polarized optical single-sideband modulation signal E out (t), which can be expressed as:

[0095]

[0096] where θ is the phase shift between the two orthogonal polarization signals; α is the angle between the polarizer and one of the main axes of the output signal of the dual-polarization Mach-Zehnder modulator, which is set to 45°.

[0097] After the linearly polarized optical single-sideband modulation signal passes through the optical device under test, the phase and amplitude of the optical carrier and the sidebands will change according to the frequency response of the optical device under test and the frequency response of the measurement system itself. The optical signal E(t) after the response can be expressed as:

[0098]

[0099] where H(ω) is the overall frequency response, which is the product of the frequency response H sys (ω) of the system itself and the frequency response H DUT (ω) of the optical device under test, that is, H(ω) = H sys (ω) · H DUT (ω).

[0100] When passing through the optical device under test, each sideband signal of the generated linearly polarized optical single-sideband modulation signal will be affected by the frequency response of the optical device under test and the frequency response of the measurement system itself, that is, carry the overall frequency response. H(ω c +nω m ) is the overall frequency response carried by each sideband signal at the corresponding frequency; H(ω c ) is the overall frequency response carried by the continuous optical carrier at the corresponding frequency.

[0101] The photodetector converts the first optical signal output by the device under test into a first photocurrent signal;

[0102] Specifically, through the square-law detection of the photodetector, photoelectric conversion is achieved, and the optical signal is converted into a photocurrent signal.

[0103] In the microwave amplitude and phase receiving module, the first photocurrent signal received is the one with the same scanning frequency as the microwave radio frequency sweep signal generated by the swept microwave source module among the first photocurrent signals output by the photodetector.

[0104] Specifically, through setting, the phase and amplitude receiving module is made to only receive the photocurrent signal with the same scanning frequency as the microwave radio frequency sweep signal. Therefore, the photocurrent I obtained after passing through the photodetector and the phase and amplitude receiving module is as shown in the following formula:

[0105]

[0106] where η is the responsivity of the photodetector, E * (t) is the conjugate complex form of E(t), and exp*(·) is the conjugate complex constant.

[0107] The control and data processing module performs data acquisition and processing on the amplitude and phase information extracted from the first photocurrent signal received by the microwave amplitude and phase receiving module to obtain the amplitude-phase information of the first photocurrent signal;

[0108] The control polarization control module generates a linearly polarized optical single sideband modulation signal with a phase shift condition of θ2 based on the polarization multiplexed optical single sideband modulation signal and outputs it to the device under test, where θ1 and θ2 are not the same;

[0109] By adjusting the last quarter-wave plate of the polarization controller, another linearly polarized optical single sideband modulation signal with a phase shift condition of θ2 (θ2≠θ1) is obtained.

[0110] The photodetector converts the second optical signal output by the device under test into a second photocurrent signal;

[0111] In the microwave amplitude and phase receiving module, the second photocurrent signal received is the one with the same scanning frequency as the microwave radio frequency sweep signal generated by the swept microwave source module among the second photocurrent signals output by the photodetector;

[0112] The control and data processing module performs data acquisition and processing on the amplitude and phase information extracted from the second photocurrent signal received by the microwave amplitude and phase receiving module to obtain the amplitude-phase information of the second photocurrent signal;

[0113] The control and data processing module performs digital processing on the amplitude-phase information of the first photocurrent signal and the amplitude-phase information of the second photocurrent signal respectively to obtain the frequency response of the optical device under test.

[0114] The control and data processing module extracts the amplitude-frequency response and phase-frequency response of the photocurrent signal, performs normalization processing using the calibration step, and finally obtains the accurate frequency response of the optical device under test.

[0115] Specifically, it can be seen that the second term in formula (6) contains the beat frequency signals between the sidebands of various orders that cause measurement errors. To achieve high precision, it is necessary to eliminate these measurement errors. By adjusting the last quarter-wave plate of the polarization controller twice, any different phase shifts θ1 and θ2 can be obtained. The photocurrents measured under two different phase shift conditions are respectively expressed as:

[0116]

[0117]

[0118] Processing the measurement results in formulas (7) and (8) can reduce measurement errors. The overall frequency response of the device under test at the frequency of (ω c +ω m ) can be given by the following formula:

[0119]

[0120] H(ω) = H sys (ω)·H DUT (ω). To obtain and remove the frequency response H sys (ω) of the measurement system itself, a calibration step is performed. In this calibration step, the optical device under test is removed and the two test ports are directly connected, that is, H DUT (ω) = 1. At this time, the frequency response of the measurement system itself can be expressed as:

[0121]

[0122] where, I sys1 and I sys2 are the photocurrents obtained from two measurements during the calibration process respectively.

[0123] From formulas (9) and (10), the actual accurate frequency response of the device under test with the measurement errors caused by the beat frequencies between the sidebands of various orders eliminated can be obtained, and the expression is:

[0124]

[0125] where, is the measurable complex constant of the optical device under test at the frequency of ω c .

[0126] According to formula (11), it can be known that the accurate frequency response of the device under test is independent of the introduced phase shift. Therefore, there is no need to set a specific introduced phase shift during measurement.

[0127] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A high-precision vector measurement device for polarization-controlled optical devices, characterized in that, It includes a swept-frequency microwave source module, a laser source module, a bias voltage module, a dual-polarization Mach-Zehnder modulator module, a polarization control module, a device under test, a photodetector, a microwave amplitude and phase receiving module, and a control and data processing module; The laser source module is connected to the dual-polarization Mach-Zehnder modulator module; The swept-frequency microwave source module is respectively connected to the dual-polarization Mach-Zehnder modulator module and the microwave amplitude and phase receiving module; The bias voltage module is connected to the dual-polarization Mach-Zehnder modulator module; The dual-polarization Mach-Zehnder modulator module, the polarization control module, the device under test, the photodetector, the microwave amplitude and phase receiving module, and the data processing module are connected in sequence.

2. The high-precision vector measurement device for a polarization-controlled optical device according to claim 1, characterized in that, The dual-polarization Mach-Zehnder modulator module includes a first sub-modulator x-MZM, a second sub-modulator y-MZM, a 90° polarization rotator, and a polarization combiner; The first sub-modulator x-MZM is respectively connected to the laser source module, the swept-frequency microwave source module, the bias voltage module, and the polarization combiner; The second sub-modulator x-MZM is respectively connected to the laser source module and the 90° polarization rotator; The 90° polarization rotator is connected to the polarization combiner.

3. A high-precision vector measurement device for a polarization-controlled optical device according to claim 2, characterized in that, The laser source module is used to input the generated continuous optical carrier signal into the first sub-modulator x-MZM and the second sub-modulator y-MZM respectively.

4. A high-precision vector measurement device for a polarization-controlled optical device according to claim 3, characterized in that, The swept-frequency microwave source module is used to apply a microwave radio frequency swept signal to the first sub-modulator x-MZM; the bias voltage module is used to apply a bias voltage to the first sub-modulator x-MZM, so that the first sub-modulator x-MZM outputs an optical single sideband modulation signal to the polarization combiner.

5. The high-precision vector measurement device for a polarization-controlled optical device according to claim 4, wherein The 90° polarization rotator is used to rotate the polarization state of the signal output by the second sub-modulator y-MZM by 90°, and then output the obtained signal to the polarization combiner.

6. The high-precision vector measurement device for a polarization-controlled optical device according to claim 5, characterized in that, The polarization combiner is used to combine the signal output by the first sub-modulator x-MZM and the signal output by the 90° polarization rotator into a polarization multiplexed optical single sideband modulation signal.

7. A high-precision vector measurement device for a polarization-controlled optical device according to claim 6, characterized in that, The polarization control module is used to process the polarization multiplexed optical single sideband modulation signal and then output a linearly polarized optical single sideband modulation signal to the device under test.

8. A high-precision vector measurement device for a polarization-controlled optical device according to claim 7, characterized in that The photodetector is used to convert the optical signal output by the device under test into a photocurrent signal; The microwave amplitude and phase receiving module is used to receive the photocurrent signal in the photocurrent signal output by the photodetector, which has the same scanning frequency as the microwave radio frequency swept signal generated by the swept-frequency microwave source module.

9. The high-precision vector measurement device for a polarization-controlled optical device according to claim 8, characterized in that, The control and data processing module is used to control the swept-frequency microwave source module to apply a microwave radio frequency swept signal to the first sub-modulator x-MZM, and is used to perform data acquisition and processing on the amplitude and phase information extracted by the microwave amplitude and phase receiving module from the received photocurrent signal to obtain the amplitude-phase information of the photocurrent signal.

10. A high-precision vector measurement method for a polarization-controlled optical device, applied to the high-precision vector measurement device for a polarization-controlled optical device according to any one of claims 1-9, characterized in that, It includes: The laser source module inputs the generated continuous optical carrier signal into the dual-polarization Mach-Zehnder modulator module; The control and data processing module controls the swept-frequency microwave source module to apply a microwave radio frequency swept signal to the dual-polarization Mach-Zehnder modulator module; The bias voltage module applies a bias voltage to the dual-polarization Mach-Zehnder modulator module; The dual-polarization Mach-Zehnder modulator module generates a polarization-multiplexed optical single-sideband modulation signal based on a continuous optical carrier signal, a microwave radio frequency swept signal, and a bias voltage, and outputs the polarization-multiplexed optical single-sideband modulation signal to the polarization control module; The control polarization control module generates a linearly polarized optical single-sideband modulation signal with a phase shift condition of θ1 based on the polarization-multiplexed optical single-sideband modulation signal and outputs it to the device under test; The photodetector converts the first optical signal output by the device under test into a first photocurrent signal; The microwave amplitude and phase receiving module receives the first photocurrent signal in the first photocurrent signal output by the photodetector that has the same scanning frequency as the microwave radio frequency swept signal generated by the swept microwave source module; The control and data processing module performs data acquisition and processing on the amplitude and phase information extracted by the microwave amplitude and phase receiving module from the received first photocurrent signal to obtain the amplitude-phase information of the first photocurrent signal; The control polarization control module generates a linearly polarized optical single-sideband modulation signal with a phase shift condition of θ2 based on the polarization-multiplexed optical single-sideband modulation signal and outputs it to the device under test, where θ1 and θ2 are different; The photodetector converts the second optical signal output by the device under test into a second photocurrent signal; The microwave amplitude and phase receiving module receives the second photocurrent signal in the second photocurrent signal output by the photodetector that has the same scanning frequency as the microwave radio frequency swept signal generated by the swept microwave source module; The control and data processing module performs data acquisition and processing on the amplitude and phase information extracted by the microwave amplitude and phase receiving module from the received second photocurrent signal to obtain the amplitude-phase information of the second photocurrent signal; The control and data processing module performs digital processing on the amplitude-phase information of the first photocurrent signal and the amplitude-phase information of the second photocurrent signal respectively to obtain the frequency response of the optical device under test.

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