Device response measurement system and method

Abstract

The invention provides a device response measurement system and method. According to the device response measurement system and method, outputs of pulse light sources with two different repetition frequencies are input into a photoelectric conversion device and an electro-optical frequency mixing device respectively, and electric signals generated by the photoelectric conversion device are transmitted through a radio frequency channel and then are loaded to the electro-optical frequency mixing device. Through multi-heterodyne beat frequency sampling, the sampling difficulty of a broadband signal is obviously reduced, so that response measurement of a broadband device is realized. The method does not need a complex microwave up-down conversion system, and has the advantages of low system complexity, low cost and wide coverage frequency range.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic and optoelectronic device measurement applications, and in particular to a device response measurement system and method. BACKGROUND

[0002] With the rapid development of high-speed optical networks, artificial intelligence, 5G mobile communications, super-large-capacity data centers and other information technologies, in order to cope with the surge in traffic, transmission networks are facing increasingly urgent demands for transmission rate and capacity improvement, so the bandwidth requirements of information systems and their core devices are rapidly increasing according to Shannon's theorem. At the same time, in order to further improve the detection accuracy and other performance of new generation radars, electromagnetic sensing and other technologies, higher frequency spectrum resources are being continuously explored and expanded. The performance of microwave photonics systems and radio frequency systems for the above applications is limited by the frequency response performance of the core devices, so it is urgent to develop and improve high-performance, wideband devices and systems that can cover more than 100 GHz or even up to THz. Therefore, high-frequency wideband devices play a key role in the development of cutting-edge information and communication technologies.

[0003] In recent years, the evolution of chip and device technology has continuously improved the wideband performance of devices. The continuous emergence of new materials and technologies such as silicon-based photonic devices, thin-film lithium niobate devices, surface plasmon devices, and two-dimensional nanomaterials has unprecedentedly improved the speed and efficiency of the interaction between light and electricity, making higher frequency optical and electrical devices possible.

[0004] To achieve the acquisition of the frequency response information of a device, it is necessary to have the ability to accurately generate and receive wideband microwave or terahertz signals. With the continuous improvement of the bandwidth of high-performance radio frequency devices and photonic devices, the signal generation and sampling capabilities of the measuring instruments used in the process of measuring frequency response characteristics pose a huge challenge. Currently, the main measurement methods and core instruments are still based on microwave electronic devices and technology. A typical method is a vector network analyzer that realizes up-conversion and down-conversion transformation based on microwave mixing principles. Another method is to use a step / pulse generator and a high-speed oscilloscope for time-domain measurement. These measurement methods are all centered on high-frequency electronic measurement systems, so improving the measurement bandwidth relies on the gradual improvement of the high-frequency wideband performance of the electrical system, and the implementation difficulty is increasing, so the speed of measurement bandwidth improvement is relatively slow. Moreover, the complex high-frequency microwave system makes these instruments relatively expensive and bulky.

[0005] The development of photonics technology provides different technical paths for the generation and measurement of high-frequency signals. In previous studies, the light pulse can be used to excite the optoelectronic device, and then the broadband electronic instrument, such as a high-speed oscilloscope or a broadband spectrum analyzer, can be used for measurement to obtain the response of the device. However, this method is still limited by the measurement bandwidth or sampling frequency of the electronic instrument. In recent years, the optical frequency comb technology has developed rapidly. The mode-locked optical frequency comb technology based on ultrafast laser has the outstanding performance advantages of large bandwidth and low noise. By controlling the pulse repetition frequency and other low-frequency parameters, the optical frequency characteristics can be precisely controlled. Therefore, the mode-locked optical frequency comb technology can be used as an ideal link between microwave and optical frequency. Due to its large bandwidth advantage and precise frequency control capability, the mode-locked optical frequency comb technology overcomes the shortcomings of previous photonics technology, which has a large bandwidth but is difficult to control accurately. The mode-locked optical frequency comb technology provides a new way to generate ultra-wideband high-frequency signals through broadband photonics technology. On the other hand, the dual optical frequency comb technology uses a similar optical frequency comb with a similar comb tooth frequency interval. By utilizing the time-frequency high correlation between the two similar optical frequency combs, large-scale and high-precision transformation between time-frequency signals can be achieved. The high-frequency signal is sampled and transformed to a low-frequency band through the vernier effect between the two combs, greatly compressing the signal bandwidth. This provides a new way for convenient measurement of wideband high-frequency signals. However, the previous frequency-stabilized optical frequency comb technology requires a complex frequency stabilization system, which limits its application in many fields.

[0006] The system and method provided by the present application utilize the ultra-wide bandwidth characteristics of microwave photonics technology based on dual optical frequency comb technology. In the present application, a wideband optical frequency comb generated through a mode-locked process is converted to a high-frequency band through photoelectric conversion based on optical pulse excitation to generate large-scale up-conversion. At the same time, the repetition frequency of this excitation optical comb is low, and it determines the spectral resolution of the spectral measurement result, so a high spectral resolution is obtained. Based on the vernier effect of dual optical combs, large-scale down-conversion is achieved to form a low-bandwidth signal corresponding to a wideband signal. This scheme simultaneously solves the problems of generation and acquisition of high-frequency wideband signals, eliminates the need for high-frequency microwave systems, and only requires a low-frequency electronic system to measure the wideband high-frequency signal. On the other hand, a non-frequency-stabilized optical frequency comb source is used to realize sampling. The sampling signal can obtain a high signal-to-noise ratio through long-time averaging, and the complexity of the system is significantly reduced. The above features enable the system to realize high-bandwidth, high-resolution, and fast frequency response measurement. SUMMARY

[0007] The present application provides a device response measurement system, comprising:

[0008] The pulse light source, the photoelectric conversion device, the radio frequency channel, the electro-optical mixing device, the pulse repetition frequency and repetition frequency difference extraction device, the data acquisition and processing device; wherein the pulse light source simultaneously generates light pulse 1 with repetition frequency f1 and light pulse 2 with repetition frequency f2, a part of the light pulse 1 output by the pulse light source as the optical signal 1, a part of the light pulse 2 output by the pulse light source as the optical signal 2, another part of the light pulse 1 and another part of the light pulse 2 output by the pulse light source as the optical signal 3; the optical signal 1 is input to the photoelectric conversion device to generate the electrical signal 1; the optical signal 2 is input to the electro-optical mixing device, the electrical signal 1 is loaded to the electro-optical mixing device after passing through the radio frequency channel to modulate the optical signal 2, and the modulated optical signal 2 is converted into the electrical signal 2 in the electro-optical mixing device; the pulse repetition frequency and repetition frequency difference extraction device processes the optical signal 3 to obtain and generate the repetition frequency and repetition frequency difference information of the light pulse 1 and the light pulse 2 in real time; the data acquisition and processing device samples the electrical signal 2 generated by the electro-optical mixing device, obtains the time domain response or frequency response of the photoelectric conversion device, the radio frequency channel or the electro-optical mixing device according to the sampling signal, the repetition frequency and repetition frequency difference information generated by the pulse repetition frequency and repetition frequency difference extraction device, and the sampling clock frequency information.

[0009] In one example, the pulse light source simultaneously generates two light pulses from the same optical resonant cavity, or two optical resonant cavities with partially overlapping optical paths, or two optical resonant cavities with different optical paths and not integer multiples of each other, and the two light pulses generated by the pulse light source have different repetition frequencies that are not integer multiples of each other.

[0010] In one example, the repetition frequency of at least one of the light pulse 1 and the light pulse 2 is free-running and not actively controlled by the feedback control device.

[0011] In one example, the photoelectric conversion device is a photodiode, a photodetector, a photomultiplier tube, a photoresistor, a photoconductive device, a nonlinear optical material, or a surface effect device.

[0012] In one example, the electrical signal 1 is a microwave, millimeter wave or terahertz wave signal.

[0013] In one example, the radio frequency channel is an active or passive waveguide device, an antenna, a lens, a reflector, a spatial coupling device, and combinations thereof in the microwave, millimeter wave or terahertz wave band.

[0014] In one example, the electro-optical mixing device is a combination of an optical modulator and a photodetector, a superconducting detector or a photoconductive device.

[0015] In one example, the optical modulator is an electro-optical modulator, an electro-optical crystal, a nonlinear crystal, a nonlinear optical fiber, a nonlinear waveguide, an optical coupler, and combinations thereof.

[0016] In one example, the pulse repetition frequency and repetition frequency difference extraction device generates the pulse repetition frequency difference information in a manner that generates a clock signal with a frequency that is an integer multiple of the pulse repetition frequency difference, and the data acquisition and processing device samples using the clock signal as a sampling clock.

[0017] The application provides a device response measurement method, characterized in that comprising:

[0018] Step 1, a pulsed light source simultaneously generates light pulse 1 with a repetition frequency f1 and light pulse 2 with a repetition frequency f2, part of the light pulse 1 as light signal 1, part of the light pulse 2 as light signal 2, and another part of the light pulse 1 and the light pulse 2 as light signal 3, the repetition frequency difference Δf is equal to the minimum value of the absolute value of (f1-round(f1÷f2)*f2) and the absolute value of (f2-round(f2÷f1)*f1), wherein round is a rounding operation; when the maximum value of f1÷f2 and f2÷f1 is greater than 1 and less than 1.5, Δf is the absolute value of f2-f1.

[0019] Step 2, input the light signal 1 to the photoelectric conversion device to generate an electrical signal 1, the electrical signal 1 is loaded to the electro-optical mixing device after passing through the radio frequency channel, and the light signal 2 passing through the electro-optical mixing device is modulated, and the electro-optical mixing device converts the modulated light signal 2 into an electrical signal 2;

[0020] Step 3, the light signal 3 is input to the pulse repetition frequency and repetition frequency difference extraction device to obtain and generate the repetition frequency information of at least one of the light pulse 1 and the light pulse 2, and simultaneously generate a signal containing the pulse repetition frequency difference information;

[0021] Step 4, the data acquisition and processing device samples the electrical signal 2 generated by the electro-optical mixing device to obtain a sampling signal, calculates the time domain response and the frequency response according to the sampling signal, the sampling clock frequency information, the repetition frequency difference information and the repetition frequency information generated by the pulse repetition frequency and repetition frequency difference extraction device, and calculates the time domain response and the frequency response of one or more of the photoelectric conversion device, the radio frequency channel and the electro-optical mixing device according to the known time domain response and the frequency response of the photoelectric conversion device, the radio frequency channel and the electro-optical mixing device.

[0022] In one example, in step 1, the repetition frequency of at least one of the light pulse 1 and the light pulse 2 is free running without using a feedback control device to actively control.

[0023] In one example, in step 2, the direct current bias of the optical modulator in the electro-optical mixing device is set in the linear modulation working area.

[0024] In one example, in step 4, the data acquisition and processing device samples with a sampling clock, and according to the sampling clock frequency, the measurement time interval Ts of the sampling signal can be obtained, and then according to the pulse repetition frequency and the repetition frequency difference information, the actual time interval is obtained, that is, Ts is multiplied by the conversion coefficient (Δf / f1) to obtain the actual time value corresponding to the time domain response, and the time-frequency transformation of the sampling signal is performed, and according to the pulse repetition frequency and the repetition frequency difference information, the actual frequency value corresponding to the frequency response is obtained. The conversion from the measurement time to the actual time can also be performed in the time domain, and after the time-frequency transformation, the frequency value corresponding to the frequency response is divided by the conversion coefficient (Δf / f1) to obtain the actual frequency value.

[0025] In one example, in step 4, the data acquisition and processing device samples with a clock signal whose frequency is an integer multiple (M times) of the pulse repetition frequency difference generated by the pulse repetition frequency and repetition frequency difference extraction device, and the actual time interval between each sampling point of the obtained sampling signal is 1 / (M*f1), and then the actual time value corresponding to the time domain response is obtained, and the time-frequency transformation of the sampling signal is performed, and according to the repetition frequency f1 of the optical pulse 1 and M, the actual frequency value corresponding to the frequency response is obtained.

[0026] In one example, in step 5, for the measurement of the response of the radio frequency device, in the case of sequentially connecting the photoelectric conversion device, the radio frequency channel and the electro-optical mixing device, the sampling signal is measured to obtain the time domain response 1 and the frequency response 1; in the case of connecting the radio frequency device to the radio frequency channel, the time domain response 2 and the frequency response 2 are measured, the frequency response of the radio frequency channel is obtained by dividing the frequency response 2 by the frequency response 1, and the time domain response of the radio frequency device is obtained by deconvolving the time domain response 1 with the time domain response 2.

[0027] In one example, in step 5, for the measurement of the response characteristics of the photoelectric conversion device, in the case of sequentially connecting the photoelectric conversion device, the radio frequency channel and the electro-optical mixing device, the sampling signal is measured to obtain the time domain response 1 and the frequency response 1, and according to the previously obtained time domain response 3 and the frequency response 3 of the radio frequency channel and the electro-optical mixing device, the frequency response of the photoelectric conversion device is obtained by dividing the frequency response 1 by the frequency response 3, and the time domain response of the photoelectric conversion device is obtained by deconvolving the time domain response 1 with the time domain response 3.

[0028] In one example, in step 5, for the measurement of the response characteristic of the electro-optic mixing device, the sampling signal is measured in the case of connecting the photoelectric conversion device, the radio frequency channel and the electro-optic mixing device in sequence, to obtain the time domain response 1 and the frequency response 1, and according to the time domain response 4 and the frequency response 4 of the photoelectric conversion device and the radio frequency channel obtained in advance, the frequency response of the electro-optic mixing device is obtained by dividing the frequency response 1 by the frequency response 4, and the time domain response of the electro-optic mixing device is obtained by deconvolving the time domain response 4 with the time domain response 1. BRIEF DESCRIPTION OF DRAWINGS

[0029] The application will be further described in detail below in conjunction with the accompanying drawings, in which:

[0030] Figure 1 is a schematic diagram of a device response measurement system

[0031] Figure 2 is a system structure diagram of Example 1;

[0032] Figure 3 is a structure diagram of a dual-wavelength fiber mode-locked laser in Example 1;

[0033] Figure 4 is a spectrum diagram of the dual-wavelength fiber mode-locked laser in Example 1;

[0034] Figure 5 is a frequency spectrum diagram of the dual-wavelength fiber mode-locked laser in Example 1;

[0035] Figure 6 is a sampling signal diagram in Example 1;

[0036] Figure 7 is a time domain response of the sampling signal in Example 1 after transformation to actual time; Figure 6

[0037] Figure 8 is a frequency response of the electro-optic intensity modulator obtained in Example 1;

[0038] Figure 9 is a frequency response of the microwave device Bias-Tee obtained in Example 1;

[0039] Figure 10 is a phase response of the microwave device Bias-Tee obtained in Example 1;

[0040] Figure 11 is a system structure diagram of Example 2;

[0041] Figure 12 is a system structure diagram of Example 3;

[0042] Figure 13 is a system structure diagram of Example 4. DETAILED DESCRIPTION​

[0043] The technical solutions in the embodiments of the present application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some but not all of the embodiments of the present application.

[0044] Example 1

[0045] In this example, the structure diagram of the broadband device response measurement system is shown in Figure 2 The pulse light source of the system includes a dual-wavelength fiber mode-locked laser, an optical coupler and a wavelength division multiplexer 1. The structure diagram of the dual-wavelength fiber mode-locked laser is shown in Figure 3 The resonant cavity of the dual-wavelength fiber mode-locked laser is a ring-shaped optical resonant cavity structure, which is sequentially connected by fiber elements such as a pump laser, a wavelength division multiplexer, an erbium-doped fiber, an optical isolator, a carbon nanotube saturable absorber, an online polarizer with a polarization maintaining tail fiber, an optical coupler and a polarization controller. The carbon nanotube saturable absorber is a mode locker to achieve passive mode locking; the optical isolator realizes unidirectional transmission of light in the optical resonant cavity; the polarization controller and the online polarizer can achieve periodic spectral filtering; the pump laser provides the required pump energy for mode locking through the wavelength division multiplexer. The connection order of the devices in the ring-shaped optical resonant cavity can be changed. By adjusting the pump current of the pump laser and the polarization controller, the dual-wavelength fiber mode-locked laser generates two optical pulse signals with different center wavelengths from the same optical resonant cavity with the same optical path. Due to the dispersion effect, the two optical pulse signals with different center wavelengths have different transmission optical paths in the same optical resonant cavity, so the two generated optical pulse signals have different repetition frequencies. The optical resonant cavity of the dual-wavelength fiber mode-locked laser is free-running, and there is no active feedback control device for the cavity length or the pulse repetition frequency in the system, and there is no active feedback control for the repetition frequencies and the repetition frequency difference of the two optical pulses. The spectrum of the optical pulse signal is shown in Figure 4 The 3dB bandwidth of the spectrum of the optical pulse 1 with a center wavelength of 1544nm is 4.5nm, and its repetition frequency f1 is 42.9411MHz; the 3dB bandwidth of the spectrum of the optical pulse 2 with a center wavelength of 1564nm is 3.2nm, and its repetition frequency f2 is equal to 42.9387MHz. The repetition frequencies of the two optical pulses are different and are not integer multiples of each other, and the repetition frequency difference Δf is the minimum value of |f1-round(f1 / f2)*f2| and |f2-round(f2 / f1)*f1|, where round is the rounding operation and || is the absolute value operation. When the maximum value of f1÷f2 and f2÷f1 is greater than 1 and less than 1.5, Δf=|f2-f1|. In this example, Δf is 2394Hz. The frequency spectrum diagram of the two optical pulses after photoelectric detection is shown in Figure 5

[0046] ​The output light of the dual-wavelength fiber mode-locked laser is divided into two parts by an optical coupler. One part of the light passes through a wavelength division multiplexer 1, and two light pulses with different repetition frequencies and wavelengths are separated. The light pulse 1 with a center wavelength of 1544 nm is used as optical signal 1, and the light pulse 2 with a center wavelength of 1564 nm is used as optical signal 2. The other part of the light is used as optical signal 3, which contains part of the light pulse 1 and part of the light pulse 2. The optical signal 1 is input to a photodetector 1 with a 3dB bandwidth of 50 GHz. Since the spectral width of the optical signal 1 is much larger than the bandwidth of the photodetector 1, the photodetector 1 generates a wideband radio frequency signal with a bandwidth matching the bandwidth of the photodetector under the excitation of the optical signal 1. This radio frequency signal is used as electrical signal 1. The electrical signal 1 is input to the radio frequency input port of an electro-optical intensity modulator through a microwave coaxial cable. The bias voltage of the electro-optical intensity modulator is set to be near the linear modulation region of the positive and negative 45 degrees, 135 degrees or the direct current bias phase. The optical signal 2 is input to the electro-optical intensity modulator and is modulated by the output signal of the microwave coaxial cable and then is incident on a photodetector 2. The photodetector 2 is a low-speed photodetector with a bandwidth less than the repetition frequency of the light pulse 2, which is 22 MHz in this example. The photodetector 2 outputs electrical signal 2. The bandwidth of the electrical signal 2 is less than the repetition frequency of the light pulse 2, and can be less than half of the repetition frequency of the light pulse 2. The combination of the electro-optical intensity modulator and the photodetector 2 forms an electro-optical mixing device, which realizes the asynchronous sampling and photoelectric conversion of the optical signal 2 to the optical signal 1, thereby generating the electrical signal 2.

[0047] Meanwhile, the optical signal 3 is input to a pulse repetition frequency and repetition frequency difference extraction device composed of a wavelength division multiplexer 2, a photodetector 3, a photodetector 4, a phase-locked loop device and a digital frequency meter. The wavelength division multiplexer 2 separates the two light pulses with different repetition frequencies in the optical signal 3. The light pulse 1 with the repetition frequency f1 is incident on the photodetector 3 to generate an electrical pulse with the repetition frequency f1. The light pulse 2 with the repetition frequency f2 is incident on the photodetector 4 to generate an electrical pulse with the repetition frequency f2. The electrical pulse signals generated by the photodetector 3 and the photodetector 4 are input to the phase-locked loop device, which generates a signal that tracks the change of the repetition frequency difference Δf in real time and generates a frequency multiplication signal with a frequency of M times the repetition frequency difference Δf in real time. In this example, M = 20000, i.e., a clock signal with a frequency of about 47.88 MHz is formed. The frequency of the clock signal is more than twice the bandwidth of the electrical signal 2. The signal of the photodetector 3 is also input to the digital frequency meter to measure the repetition frequency f1 of the light pulse 1 in real time and obtain real-time information of the repetition frequency f1.

[0048] Analog-digital conversion acquisition card is used as a part of data acquisition and processing device to sample the electrical signal 2. In this example, the clock signal which is an integer multiple of the repetitive frequency difference obtained by the phase-locked loop device is used as the sampling clock of the analog-digital conversion acquisition card to sample the electrical signal 2. The obtained sampling signal is shown in Fig. 1. Figure 6

[0049] Analog-digital conversion acquisition card can also be used to sample the electrical signal 2 under a fixed clock, and the computer obtains the repetitive frequency and repetitive frequency difference information generated by the repetitive frequency and repetitive frequency difference extraction device in real time, and obtains the sampling signal through signal processing.

[0050] Two analog-digital conversion acquisition cards can also be used to sample the electrical signal 2 and the signal carrying the repetitive frequency difference generated by the repetitive frequency and repetitive frequency difference extraction device under a fixed clock, and then digital interpolation resampling is performed to obtain the sampling signal.

[0051] The computer or digital signal processor or field programmable gate array is used to process the sampling signal. At this time, the sampling signal is measured when the photoelectric detector 1, the microwave coaxial cable, and the electro-optical intensity modulator and the photoelectric detector 2 are connected in sequence, and is recorded as sampling signal 1.

[0052] Figure 6 The measurement time interval between the sampling points of the sampling signal 1 shown in Fig. 1 is 1 / (M*Δf), and the corresponding actual time interval is 1 / (M*Δf)*(Δf / f1), that is, 1 / (M*f1). The horizontal axis of the sampling signal 1 shown in Fig. 1 is converted into an actual time axis by the above actual time interval, and the time domain response 1 shown in Fig. 2 is obtained. Figure 6 Figure 7 When the data acquisition is performed using a sampling clock with a frequency that is a multiple of the repetitive frequency difference, only the value of f1 and the multiple M of the repetitive frequency difference converted to the sampling clock are needed to convert the actual time value according to the number of sampling points. The curve is the time domain response of the cascade of the photoelectric detector 1, the microwave coaxial cable, the electro-optical intensity modulator, and the photoelectric detector 2 under the excitation of the optical pulse 1. When the frequency response of the photoelectric detector 2 is flat within 0.5 times of the repetitive frequency f2, the time domain response mainly reflects the response of the cascade of the photoelectric detector 1, the microwave coaxial cable, and the electro-optical intensity modulator. When the time domain response characteristics of any two devices are known, the time domain response of the third device can be obtained by deconvolution.

[0053] ​​To obtain the response of the microwave coaxial cable used as an RF channel, after obtaining the measured time-domain response 1, the microwave coaxial cable can be removed from the system. That is, the output electrical signal 1 of photodetector 1 can be directly connected to the RF input of the electro-optic intensity modulator via the RF connector as another RF channel. The sampled signal 2 at this time is measured, and the time-domain response 2 is obtained using the same time information processing method as sampled signal 1. The time-domain response of the microwave coaxial cable can be obtained by deconvolving the time-domain response 2 with the time-domain response 1.

[0054] The frequency domain response of the device is obtained by the following method:

[0055] right Figure 6 The sampled signal 1 for one sampling period is subjected to a Fourier transform to obtain the frequency domain amplitude / intensity and phase information of the signal. Based on the actual time interval 1 / (M*f1) and the number of sampling points M within one period, the interval of the actual frequency values ​​corresponding to the frequency domain sampling points is f1. The obtained system frequency domain intensity information is as follows: Figure 8 As shown. Other methods, such as fast convolution, short-time Fourier transform, or correlation superposition, can also be used to analyze the sampled signal in the frequency domain or time-frequency domain to achieve time-frequency transformation.

[0056] Based on the pre-obtained frequency responses of the microwave coaxial cable and photodetector 1, including the frequency responses corresponding to the pulse waveforms of optical pulse 1 and optical pulse 2 and photodetector 2, the frequency responses of other parts are obtained. Dividing the system frequency domain information by the frequency responses of other parts yields the frequency response of the electro-optic intensity modulator, such as... Figure 8 As shown.

[0057] Similarly, based on the pre-obtained frequency response of the microwave coaxial cable and the electro-optic intensity modulator, including the frequency response corresponding to the pulse characteristics of optical pulse 1 and optical pulse 2 and photodetector 2, the frequency response of other parts is obtained. By dividing the system frequency domain information by the frequency response of other parts, the frequency response characteristics of photodetector 1 can be obtained.

[0058] When measuring a microwave device, the frequency response of a T-type bias-tee microwave device is measured. The time domain response of the microwave device is obtained in the same way as the time domain response of the microwave coaxial cable, and the frequency response is obtained by Fourier transform of the time domain response. The frequency domain information of the system is measured when the microwave device is connected in the microwave link, i.e. the output electrical signal of the photodetector is connected through the microwave device to the input of the microwave coaxial cable, and the frequency domain information of the system is measured. Then the microwave device is removed from the system, i.e. the output of the photodetector is directly connected to the microwave coaxial cable, and the frequency domain information of the system is measured again. The frequency response of the Bias-Tee is obtained by calculating the ratio of the two frequency domain information of the system. The frequency domain intensity response and the phase response are shown in Figure 9 and Figure 10

[0059] Example 2

[0060] In this example, the structure of the broadband device response measurement system is shown in Figure 11 The pulse light source of the system includes two free-running mode-locked lasers 1 and 2. In this example, the two mode-locked lasers can be actively mode-locked lasers, passively mode-locked lasers or hybrid mode-locked lasers. The mode-locked laser 1 and the mode-locked laser 2 each have an optical resonator, and the two optical resonators are independent of each other and have different optical path lengths, and the optical path lengths are not integer multiples of each other. The mode-locked laser 1 and the mode-locked laser 2 respectively generate optical pulses 1 and 2 with different repetition frequencies. The repetition frequency f1 of the optical pulses 1 is 25 MHz, and the repetition frequency f2 of the optical pulses 2 is 50.0001 MHz. The repetition frequencies of the two optical pulses are different and are not integer multiples of each other. The repetition frequency difference Δf of the two optical pulses is the minimum value of |f1-round(f1 / f2)*f2| and |f2-round(f2 / f1)*f1|, where round is the rounding operation, and || is the absolute value operation. In this example, Δf is 100 Hz. The mode-locked laser 1 and the mode-locked laser 2 are both free-running, and the repetition frequencies and the repetition frequency difference of the optical pulses 1 and 2 are not actively controlled by using cavity length control and repetition frequency feedback control devices. The optical pulses 1 are split into two parts by the optical coupler 1, one part is the optical signal 1, and the other part is input to the pulse repetition frequency and repetition frequency difference extraction device as part of the optical signal 3. The optical pulses 2 are split into two parts by the optical coupler 2, one part is the optical signal 2, and the other part is also input to the pulse repetition frequency and repetition frequency difference extraction device as another part of the optical signal 3.

[0061] ​The optical signal 1 is input to the photoelectric detector 1 with a bandwidth of 30GHz as a photoelectric conversion device, and the photoelectric detector 1 generates an electrical signal 1 with a bandwidth matching the photoelectric detector under the excitation of the optical signal 1. The electrical signal 1 is a broadband pulsed microwave signal. The electrical signal 1 is input from the 1 port of the circulator, and output from the 2 port to the antenna. The reflected signal of the antenna is input to the 2 port of the circulator, and output from the 3 port to the radio frequency input port of the electro-optical intensity modulator with a 3dB bandwidth of about 30GHz. The bias voltage of the electro-optical intensity modulator is set at 45 degrees or other modulator linear modulation operating point. At the same time, the optical signal 2 is input to the electro-optical intensity modulator, and the electrical signal output from the 3 port of the circulator is modulated and incident on the photoelectric detector 2. The photoelectric detector 2 is a low-speed photoelectric detector, and in this example, f1 is less than f2, and the 3dB bandwidth of the photoelectric detector 2 is less than the repetition frequency of the optical pulse 1. The photoelectric detector 2 outputs an electrical signal 2. The combination of the electro-optical intensity modulator and the photoelectric detector 2 constitutes an electro-optical mixing device, which realizes asynchronous sampling and photoelectric conversion of the optical signal 2 to the optical signal 1, thereby generating the electrical signal 2.

[0062] The pulse repetition frequency and repetition frequency difference extraction device is a combination of two photoelectric detectors and two high-precision frequency meters, which measures the repetition frequencies of the optical pulse 1 and the optical pulse 2 in real time to obtain the corresponding repetition frequency and repetition frequency difference information. The analog-digital conversion acquisition card samples the electrical signal 2 using a fixed clock with a frequency greater than or equal to twice the bandwidth of the electrical signal 2, and the obtained sampling data is processed in the computer.

[0063] The subsequent data processing process is similar to that of Example 1, but in this example, the time interval of the sampling signal is determined by the fixed clock, and the measured pulse repetition frequency and repetition frequency difference are used to realize the proportional transformation in the time domain and frequency domain transformation of the sampling signal. The obtained is the time domain response and frequency response of the cascade of the photoelectric detector 1, the circulator 1 port to the 2 port, the antenna reflection, the circulator 2 port to the 3 port, and the electro-optical modulator. The frequency response of the antenna is the S11 reflection response, and when the response of any one device is required, the processing is similar to the time domain deconvolution and frequency domain division in Example 1.

[0064] Example 3

[0065] In this example, the structure diagram of the broadband device response measurement system is as follows Figure 12The system is shown in the figure. The pulse light source of the system comprises two ring-shaped optical resonators with partially overlapped optical paths, i.e. optical resonator 1 and optical resonator 2. The two optical resonators respectively comprise a pump laser, a wavelength division multiplexer, an erbium-doped optical fiber, an optical isolator, a carbon nanotube saturable absorber, an optical coupler, an optical circulator and a polarization controller. The carbon nanotube saturable absorber is a shared part of the two optical resonators. The optical resonator 1 further comprises a fiber stretching device to stretch the length of the optical fiber in the cavity. The amount of fiber stretching is controlled by monitoring the repetition frequency of the optical pulse generated by the optical resonator 1, so as to actively control the repetition frequency of the optical pulse generated by the optical resonator 1. The other optical resonator 2 does not have an active control device for the repetition frequency and works in a free-running state. The lengths of the two optical resonators are different and are not integer multiples of each other. The two optical resonators respectively generate two optical pulse signals with different repetition frequencies which are not integer multiples of each other.

[0066] The optical resonator 1 and the optical resonator 2 generate optical pulses 1 and 2 with repetition frequencies of 60 MHz and 60.0001 MHz, respectively. The optical pulses 1 are split by the optical coupler 3 into two parts, one of which is the optical signal 1 and the other of which is input into the pulse repetition frequency and repetition frequency difference extraction device; the optical pulses 2 are split by the optical coupler 4 into two parts, one of which is the optical signal 2 and the other of which is also input into the pulse repetition frequency and repetition frequency difference extraction device. The calculation method of the repetition frequency difference is the same as that in Example 1. The optical signal 1 is input into a single-row wave carrier photodiode (UTC-PD) with a bandwidth of 120 GHz to generate an electrical signal 1 matching the bandwidth of the UTC-PD. The UTC-PD can also be replaced by a photomultiplier tube, a photoresistor or other devices capable of realizing wideband photoelectric conversion. The electrical signal 1 is transmitted through a waveguide device and then input into the radio frequency input port of an electro-optical modulator with a 3 dB bandwidth of about 120 GHz. The bias voltage of the electro-optical modulator is set near 45 degrees or other linear modulation operating points. At the same time, the optical signal 2 is input into the electro-optical modulator, modulated by the electrical signal output by the waveguide device and then incident on the photodetector 2. The waveguide device can also be replaced by other active or passive waveguide devices, antennas or space coupling devices in the microwave and millimeter wave bands and combinations thereof. The electro-optical modulator can also be replaced by an electro-optical crystal, a nonlinear crystal, a nonlinear optical fiber, a nonlinear waveguide, an optical coupler, an acousto-optical modulator, a magneto-optical modulator and combinations thereof. The photodetector 2 is a low-speed photodetector with a bandwidth less than the repetition frequency of the optical pulses 2, which is 20 MHz in this example. The photodetector 2 outputs an electrical signal 2. The combination of the electro-optical modulator and the photodetector 2 constitutes an electro-optical mixing device, which realizes asynchronous sampling and photoelectric conversion of the optical signal 2 on the optical signal 1, thereby generating the electrical signal 2. The pulse repetition frequency and repetition frequency difference extraction device is a combination of two photodetectors and an FPGA processing the outputs of the two photodetectors, which measures the repetition frequencies of the optical pulses 1 and 2 in real time to obtain the corresponding repetition frequencies and repetition frequency difference. An analog-digital conversion acquisition card samples the electrical signal 2 using a fixed clock, and the obtained sampling data is processed in a computer.

[0067] According to the fixed clock sampling frequency, the measurement time interval Ts of the sampling signal can be obtained, and then the actual time interval can be obtained according to the pulse repetition frequency and the repetition frequency difference information, that is, Ts is multiplied by the conversion factor (Δf / f1) to obtain the actual time interval, and then the time domain response similar to Figure 7 is obtained. The subsequent data processing process is similar to that in Example 1, and the obtained is the time domain response and frequency response of the cascade of the UTC-PD, the waveguide device and the electro-optical modulator. The time domain response or frequency response of any one of the devices can be obtained by processing similar to the time domain deconvolution and frequency domain division in Example 1.

[0068] Example 4

[0069] In this example, the pulsed light source includes a polarization multiplexed single cavity dual comb laser, which generates light pulse 1 and light pulse 2 with orthogonal polarization and different repetition frequencies simultaneously. The resonant cavity of the polarization multiplexed single cavity dual comb laser is a ring resonant cavity structure, which is sequentially connected by a pump laser, a wavelength division multiplexer, an erbium-doped fiber, an optical isolator, a carbon nanotube saturable absorber, a polarization maintaining fiber, a polarization controller, an optical coupler and a fiber stretcher. The polarization maintaining fiber provides birefringence, and by adjusting the polarization controller, the light pulse 1 and the light pulse 2 with orthogonal polarization can be simultaneously mode-locked. Due to the birefringence effect, the repetition frequencies of the light pulse 1 and the light pulse 2 are different. By actively controlling the fiber stretcher, the repetition frequency of the light pulse 1 is stabilized at 50 MHz, while the repetition frequency difference between the light pulse 1 and the light pulse 2 is affected by the birefringence in the cavity and is not actively feedback controlled. The repetition frequency of the light pulse 2 is not actively controlled and is about 50.0001 MHz.

[0070] The output of the laser is separated into light pulse 1 and light pulse 2 with orthogonal polarization after passing through the polarization beam splitter, and the optical amplifier 1 and the optical amplifier 2 amplify the two optical signals respectively and adjust the dispersion by adding a single-mode optical fiber to achieve spectral broadening and pulse compression. The pulse width after amplification and compression is about 110 fs. After amplification and compression, the two optical signals pass through the optical coupler, and one output of the optical coupler 2 is optical signal 1, and the other is transmitted to the pulse repetition frequency and repetition frequency difference extraction device as part of optical signal 3; one output of the optical coupler 3 is optical signal 2, and the other is also transmitted to the pulse repetition frequency and repetition frequency difference extraction device as part of optical signal 3, and the repetition frequency difference of the light pulse 1 and the light pulse 2 is obtained according to the same definition as in Example 1. Optical signal 1 is input into photoconductive antenna 1 and converted into terahertz wave radiation into a spatial coupling device composed of a concave mirror, a terahertz lens and a concave mirror. Optical signal 2 is input into photoconductive antenna 2 and mixed with the terahertz wave signal received from the spatial coupling device, outputting electrical signal 2 containing device response information. Photoconductive antenna 1 can also be replaced by a nonlinear optical material or a surface effect device that can radiate terahertz signals, and photoconductive antenna 2 can also be replaced by a combination of a nonlinear crystal, a nonlinear fiber, a nonlinear waveguide and a photodetector that can receive terahertz signals.

[0071] In this example, the data acquisition and processing device is composed of a narrow-band low-noise electric amplifier, a filter, an analog-digital conversion acquisition card and a computer. The electric signal 2 is input to the analog-digital conversion acquisition card after being amplified by the narrow-band low-noise electric amplifier and filtered, and the output of the acquisition card is processed by the computer. The remaining part of this example and the data processing part are similar to those of Example 2. The time-domain response and the frequency response of the cascade of the photoconductive antenna 1, the space coupling device and the photoconductive antenna 2 are obtained. The response of any one of the devices can be obtained by using the time-domain deconvolution and the frequency-domain division processing similar to those in Example 1.

[0072] The above merely illustrates the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can make appropriate changes or modifications within the technical scope disclosed by the present application, and such changes or modifications shall be covered within the protection scope of the present application.

Claims

1. A device response measurement system, characterized by, The device comprises a pulsed light source, a photoelectric conversion device, a radio frequency channel, an electro-optical mixing device, a pulse repetition frequency and repetition frequency difference extraction device, and a data acquisition and processing device; the pulsed light source simultaneously generates light pulses 1 with a repetition frequency f1 and light pulses 2 with a repetition frequency f2, a part of the light pulses 1 output by the pulsed light source is used as an optical signal 1, a part of the light pulses 2 output by the pulsed light source is used as an optical signal 2, and another part of the light pulses 1 and another part of the light pulses 2 output by the pulsed light source are used as an optical signal 3; the optical signal 1 is input to the photoelectric conversion device to generate an electrical signal 1; the optical signal 2 is input to the electro-optical mixing device, and the electrical signal 1 is loaded onto the electro-optical mixing device after passing through the radio frequency channel to modulate the optical signal 2, and the modulated optical signal 2 is converted into an electrical signal 2 in the electro-optical mixing device; the pulse repetition frequency and repetition frequency difference extraction device processes the optical signal 3 to obtain the repetition frequency and repetition frequency difference information of the light pulses 1 and the light pulses 2 in real time; The data acquisition and processing device samples the electrical signal 2 generated by the electro-optical mixing device, obtains the time domain response or frequency response of the photoelectric conversion device, the radio frequency channel or the electro-optical mixing device according to the sampling signal, the repetition frequency and repetition frequency difference information generated by the pulse repetition frequency and repetition frequency difference extraction device, and the sampling clock frequency information.

2. The device response measurement system of claim 1, wherein, The pulsed light source simultaneously generates two light pulses from the same optical resonant cavity, or two optical resonant cavities with partially overlapping optical paths, or two optical resonant cavities with different optical paths that are not integer multiples of each other, and the two light pulses generated by the pulsed light source have different repetition frequencies that are not integer multiples of each other.

3. The device response measurement system as defined in claim 2, wherein The repetition frequency of at least one of the light pulses 1 and the light pulses 2 is free-running and not actively controlled by a feedback control device.

4. The device response measurement system of claim 1, wherein, The photoelectric conversion device is a photodiode, a photodetector, a photomultiplier tube, a photoresistor, a photoconductive device, a nonlinear optical material, or a surface effect device.

5. The device response measurement system of claim 1, wherein, The electrical signal 1 is a microwave, millimeter wave, or terahertz wave signal.

6. The device response measurement system of claim 1, wherein, The radio frequency channel is an active or passive waveguide device, an antenna, a lens, a reflector, a spatial coupling device, or a combination thereof in the microwave, millimeter wave, or terahertz wave band.

7. The device response measurement system of claim 1, wherein, The electro-optical mixing device is a combination of an optical modulator and a photodetector, a superconducting detector, or a photoconductive device.

8. The electro-optical mixing device of claim 7, wherein, The optical modulator is an electro-optical modulator, an electro-optical crystal, a nonlinear crystal, a nonlinear optical fiber, a nonlinear waveguide, an optical coupler, or a combination thereof.

9. The device response measurement system of claim 1, wherein, The pulse repetition frequency and repetition frequency difference extraction device generates pulse repetition frequency difference information in a manner that generates a clock signal with a frequency that is an integer multiple of the pulse repetition frequency difference, and the data acquisition and processing device samples with the clock signal as the sampling clock.

10. A device response measurement method characterized by, The device comprises a pulsed light source, a photoelectric conversion device, a radio frequency channel, an electro-optical mixing device, a pulse repetition frequency and repetition frequency difference extraction device, and a data acquisition and processing device; the pulsed light source simultaneously generates light pulses 1 with a repetition frequency f1 and light pulses 2 with a repetition frequency f2, a part of the light pulses 1 output by the pulsed light source is used as an optical signal 1, a part of the light pulses 2 output by the pulsed light source is used as an optical signal 2, and another part of the light pulses 1 and another part of the light pulses 2 output by the pulsed light source are used as an optical signal 3; the optical signal 1 is input to the photoelectric conversion device to generate an electrical signal 1; the optical signal 2 is input to the electro-optical mixing device, and the electrical signal 1 is loaded onto the electro-optical mixing device after passing through the radio frequency channel to modulate the optical signal 2, and the modulated optical signal 2 is converted into an electrical signal 2 in the electro-optical mixing device; the pulse repetition frequency and repetition frequency difference extraction device processes the optical signal 3 to obtain the repetition frequency and repetition frequency difference information of the light pulses 1 and the light pulses 2 in real time; The data acquisition and processing device samples the electrical signal 2 generated by the electro-optical mixing device, obtains the time domain response or frequency response of the photoelectric conversion device, the radio frequency channel or the electro-optical mixing device according to the sampling signal, the repetition frequency and repetition frequency difference information generated by the pulse repetition frequency and repetition frequency difference extraction device, and the sampling clock frequency information. The pulsed light source simultaneously generates two light pulses from the same optical resonant cavity, or two optical resonant cavities with partially overlapping optical paths, or two optical resonant cavities with different optical paths that are not integer multiples of each other, and the two light pulses generated by the pulsed light source have different repetition frequencies that are not integer multiples of each other. The repetition frequency of at least one of the light pulses 1 and the light pulses 2 is free-running and not actively controlled by a feedback control device. The photoelectric conversion device is a photodiode, a photodetector, a photomultiplier tube, a photoresistor, a photoconductive device, a nonlinear optical material, or a surface effect device. The electrical signal 1 is a microwave, millimeter wave, or terahertz wave signal. The radio frequency channel is an active or passive waveguide device, an antenna, a lens, a reflector, a spatial coupling device, or a combination thereof in the microwave, millimeter wave, or terahertz wave band. The electro-optical mixing device is a combination of an optical modulator and a photodetector, a superconducting detector, or a photoconductive device. The optical modulator is an electro-optical modulator, an electro-optical crystal, a nonlinear crystal, a nonlinear optical fiber, a nonlinear waveguide, an optical coupler, or a combination thereof. The pulse repetition frequency and repetition frequency difference extraction device generates pulse repetition frequency difference information in a manner that generates a clock signal with a frequency that is an integer multiple of the pulse repetition frequency difference, and the data acquisition and processing device samples with the clock signal as the sampling clock. The device comprises a pulsed light source, a photoelectric conversion device, a radio frequency channel, an electro-optical mixing device, a pulse repetition frequency and repetition frequency difference extraction device, and a data acquisition and processing device; the pulsed light source simultaneously generates light pulses 1 with a repetition frequency f1 and light pulses 2 with a repetition frequency f2, a part of the light pulses 1 output by the pulsed light source is used as an optical signal 1, a part of the light pulses 2 output by the pulsed light source is used as an optical signal 2, and another part of the light pulses 1 and another part of the light pulses 2 output by the pulsed light source are used as an optical signal 3; the optical signal 1 is input to the photoelectric conversion device to generate an electrical signal 1; the optical signal 2 is input to the electro-optical mixing device, and the electrical signal 1 is loaded onto the electro-optical mixing device after passing through the radio frequency channel to modulate the optical signal 2, and the modulated optical signal 2 is converted into an electrical signal 2 in the electro-optical mixing device; the pulse repetition frequency and repetition frequency difference extraction device processes the optical signal 3 to obtain the repetition frequency and repetition frequency difference information of the light pulses 1 and the light pulses 2 in real time; In step 1, the pulse light source simultaneously generates light pulse 1 with a repetition frequency f1 and light pulse 2 with a repetition frequency f2, a part of the light pulse 1 is used as optical signal 1, a part of the light pulse 2 is used as optical signal 2, and another part of the light pulse 1 and the light pulse 2 is used as optical signal 3, the repetition frequency difference Δf is equal to the minimum value of the absolute value of (f1-round(f1÷f2)*f2) and the absolute value of (f2-round(f2÷f1)*f1), wherein round is a rounding operation; In step 2, the optical signal 1 is input to the photoelectric conversion device to generate the electrical signal 1, the electrical signal 1 is loaded to the electro-optical mixing device after passing through the radio frequency channel, and the optical signal 2 passing through the electro-optical mixing device is modulated, and the electro-optical mixing device converts the modulated optical signal 2 into the electrical signal 2; In step 3, the optical signal 3 is input to the pulse repetition frequency and repetition frequency difference extraction device to obtain and generate the repetition frequency information of at least one of the light pulse 1 and the light pulse 2, and simultaneously generate a signal containing the pulse repetition frequency difference information; In step 4, the data acquisition and processing device samples the electrical signal 2 generated by the electro-optical mixing device to obtain a sampling signal, calculates the time domain response and the frequency response according to the sampling signal, the sampling clock frequency information, the repetition frequency difference information and the repetition frequency information generated by the pulse repetition frequency and repetition frequency difference extraction device, and calculates the time domain response and the frequency response of one or more of the photoelectric conversion device, the radio frequency channel and the electro-optical mixing device according to the known time domain response and the frequency response of the photoelectric conversion device, the radio frequency channel and the electro-optical mixing device.

11. The device response measurement method according to claim 10, wherein In step 1, the repetition frequency of at least one of the light pulse 1 and the light pulse 2 is free running without using a feedback control device to actively control.

12. The device response measurement method according to claim 10, wherein In step 2, the direct current bias of the optical modulator in the electro-optical mixing device is set in the linear modulation working area.

13. The device response measurement method according to claim 10, wherein In step 4, the data acquisition and processing device samples with a sampling clock, and the measurement time interval Ts of the sampling signal can be obtained according to the sampling clock frequency, the actual time interval can be obtained according to the pulse repetition frequency and the repetition frequency difference information, and the actual time value corresponding to the time domain response is obtained, the time-frequency transformation of the sampling signal is performed, and the actual frequency value corresponding to the frequency response is obtained according to the pulse repetition frequency and the repetition frequency difference information.

14. The device response measurement method according to claim 10, wherein In step 4, the data acquisition and processing device samples with a clock signal whose frequency is an integer multiple (M times) of the pulse repetition frequency difference information generated by the pulse repetition frequency and repetition frequency difference extraction device, the actual time interval between each sampling point of the obtained sampling signal is 1 / (M*f1), and the actual time value corresponding to the time domain response is obtained, the time-frequency transformation of the sampling signal is performed, and the actual frequency value corresponding to the frequency response is obtained according to the repetition frequency f1 of the light pulse 1 and M.

15. The device response measurement method according to claim 10, wherein In step 5, for the measurement of the response of the radio frequency device, the sampling signal is measured in the case of connecting the photoelectric conversion device, the radio frequency channel and the electro-optical mixing device in sequence, to obtain the time domain response 1 and the frequency response 1; the time domain response 2 and the frequency response 2 are measured in the case of connecting the radio frequency device to the radio frequency channel, the frequency response of the radio frequency channel is obtained by dividing the frequency response 2 by the frequency response 1, and the time domain response of the radio frequency device is obtained by deconvolving the time domain response 2 from the time domain response 1.

16. The device response measurement method according to claim 10, wherein In step 5, for the measurement of the response of the photoelectric conversion device, the sampling signal is measured in the case of connecting the photoelectric conversion device, the radio frequency channel and the electro-optical mixing device in sequence, to obtain the time domain response 1 and the frequency response 1; the time domain response 3 and the frequency response 3 of the radio frequency channel and the electro-optical mixing device are obtained in advance, the frequency response of the photoelectric conversion device is obtained by dividing the frequency response 1 by the frequency response 3, and the time domain response of the photoelectric conversion device is obtained by deconvolving the time domain response 1 from the time domain response 3.

17. The device response measurement method according to Claim 10, wherein In step 5, for the measurement of the response of the photoelectric conversion device, the sampling signal is measured in the case of connecting the photoelectric conversion device, the radio frequency channel and the electro-optical mixing device in sequence, to obtain the time domain response 1 and the frequency response 1; the time domain response 3 and the frequency response 3 of the radio frequency channel and the electro-optical mixing device are obtained in advance, the frequency response of the photoelectric conversion device is obtained by dividing the frequency response 1 by the frequency response 3, and the time domain response of the photoelectric conversion device is obtained by deconvolving the time domain response 1 from the time domain response 3.

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