Reconfigurable real-time spectral measurement system and applications

Abstract

The application discloses a reconfigurable real-time spectrum measurement system and application, and relates to the field of spectrum measurement. The system comprises a pulse extraction module, a loop control module and a spectrum display module. The pulse extraction module is used for generating a first optical pulse signal and adjusting the repetition frequency of the first optical pulse signal to obtain a second optical pulse signal. The loop control module is used for controlling the size of the dispersion in the system to achieve the effect of adjustable system resolution and realize the mapping of the spectrum of the second optical pulse signal in the time dimension to obtain a to-be-measured optical pulse signal. The spectrum display module is used for photoelectric conversion of the to-be-measured optical pulse signal and real-time monitoring of the time-domain waveform of the to-be-measured optical pulse signal to obtain a monitoring result. The application can flexibly adjust the spectrum measurement resolution of the optical pulse signal according to actual requirements, and can also flexibly control the spectrum measurement refresh rate of the optical pulse signal according to actual requirements. The mode of the loop is used to reduce the cost and time of the dispersion fiber construction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of precision instruments, in particular to a reconfigurable real-time spectrum measurement system and application. BACKGROUND

[0002] Traditional spectrum acquisition principles include dispersion type and interference type. The dispersion type is to arrange the dispersed monochromatic light according to the wavelength size to obtain the target spectrum after the polychromatic light is dispersed by a dispersion element (such as a prism, a grating), which has the characteristics of mature technology and stable performance, but the realization of high spatial resolution and spectral resolution requires a small incident slit, which limits the light flux and signal-to-noise ratio; the interference type uses the Fourier transform spectrum characteristics of double-beam interference to realize the acquisition of spectrum data, which has the characteristics of large light flux and high wavelength accuracy, but it needs precise and stable dynamic mirror scanning when working, so it cannot realize real-time detection of the target spectrum.

[0003] Once the above two types of spectrometer systems are determined, the spectral resolution, bandwidth range and other parameters cannot be changed. In order to meet the needs of different tasks, it is necessary to have high spectral resolution and wide spectral range, which will lead to the decline of system signal-to-noise ratio and the increase of spectral image data volume. The decline of signal-to-noise ratio will affect the image acquisition quality, the increase of data volume will occupy a large storage space, and also prolong the data acquisition and processing time, which affects the real-time performance of the system.

[0004] The frequency-time mapping technology, sometimes also called real-time Fourier transform, maps the spectrum information of the signal to be measured to the time dimension, so that the time domain envelope of the output signal is proportional to the spectrum shape of the input microwave signal, and then the wideband spectrum information of the input signal can be directly read by an oscilloscope. Usually, the frequency-time mapping is completed by second-order dispersion, which uses the different transmission speeds of light with different frequencies in the dispersion medium to realize the mapping process from frequency to time. SUMMARY

[0005] The present application uses the frequency-time mapping technology to map the spectrum information of the optical pulse signal to the time dimension, and controls the change of the dispersion amount to control the resolution of the system and controls the change of the repetition rate of the optical pulse signal to control the refresh rate of the system.

[0006] To achieve the above purpose, the present application provides a reconfigurable real-time spectrum measurement system, which comprises: a pulse extraction module, a loop control module and a spectrum display module.

[0007] The pulse extraction module is used to generate a first optical pulse signal and adjust the repetition frequency of the first optical pulse signal to obtain a second optical pulse signal.

[0008] The loop control module is used for controlling the size of the dispersion in the system, realizing the mapping of the spectrum of the second optical pulse signal in the time dimension, and obtaining the to-be-measured optical pulse signal.

[0009] The spectrum display module is used for photoelectric conversion of the to-be-measured optical pulse signal, and real-time monitoring of the time-domain waveform of the to-be-measured optical pulse signal, and obtaining a monitoring result.

[0010] Preferably, the pulse extraction module comprises a mode-locked laser device, a first digital delay generation device and a first acousto-optic modulation device.

[0011] The mode-locked laser device is used for emitting the first optical pulse signal.

[0012] The first acousto-optic modulation device is used for selectively extracting the first optical pulse signal, realizing the adjustment of the repetition frequency of the first optical pulse signal, and obtaining the second optical pulse signal.

[0013] The first digital delay generation device is used for controlling the first acousto-optic modulation device and is synchronized with the mode-locked laser device.

[0014] Preferably, the loop control module comprises a 3dB coupling device, a dispersion element, an optical amplification device, a second digital delay generation device, a second acousto-optic modulation device and a third acousto-optic modulation device.

[0015] The 3dB coupling device is used for controlling the second optical pulse signal and the to-be-measured optical pulse signal to enter or exit the loop.

[0016] The dispersion element is used for mapping the spectrum of the second optical pulse signal in the time dimension.

[0017] The second digital delay generation device is used for controlling the second acousto-optic modulation device and the third acousto-optic modulation device.

[0018] The second acousto-optic modulation device is used for controlling whether the second optical pulse signal enters the loop again through the coupling device.

[0019] The third acousto-optic modulation device is used for controlling whether the second optical pulse signal enters the spectrum display module.

[0020] The optical amplification device is used for amplifying the second optical pulse signal, compensating for the loss of the 3dB coupling device, the second acousto-optic modulation device, the third acousto-optic modulation device and the dispersion element, and obtaining the to-be-measured optical pulse signal.

[0021] Preferably, the spectrum display module comprises a photoelectric detection device and a digital oscilloscope.

[0022] The photoelectric detection device is used to perform photoelectric conversion on the light pulse signal to be measured;

[0023] The digital oscilloscope is used to monitor the time-domain waveform of the optical pulse signal under test in real time and obtain the monitoring results.

[0024] Preferably, the working process of the loop control module includes:

[0025] When the second optical pulse signal needs to continue circulating in the loop for another cycle, the drive signal provided by the second digital delay generator must be at a high level, so that the second acousto-optic modulator functions as a closed optical switch, ensuring that the second optical pulse signal can completely pass through the second acousto-optic modulator and re-enter the loop. Since the second and third acousto-optic modulators are out of phase, the third acousto-optic modulator is in an open optical switch state at this time. Therefore, in this state, the spectrum display module will not receive the optical pulse signal. When the optical pulse signal reaches the required number of cycles, by appropriately controlling the drive signal provided by the second digital delay generator, the second acousto-optic modulator is opened and the third acousto-optic modulator is closed. The second acousto-optic modulator isolates the optical pulse signal under test from continuing to transmit in the loop, and the optical pulse signal under test reaches the spectrum display module through the third acousto-optic modulator.

[0026] Preferably, the method for obtaining the resolution of the monitoring results includes:

[0027]

[0028] Where n represents the number of cycles of the optical pulse signal, D represents the group velocity dispersion value of the dispersion compensation fiber, L represents the length of the dispersion compensation fiber, and f s This indicates the sampling frequency of the oscilloscope.

[0029] This application also provides an application of the above-mentioned reconfigurable real-time spectral measurement system, the steps of which include:

[0030] First, the optical pulses output by the mode-locked laser device are extracted using the first digital delay generator to change the repetition frequency of the optical pulse signal. Then, the second and third acousto-optic modulators are driven by the loop control module to control the number of loops of the optical pulse signal, and the dispersive element is installed in the loop to map the spectrum of the optical pulse signal in the time dimension. Finally, the optical pulses are photoelectrically converted by the spectrum display module, and the time-domain waveform of the optical pulse signal is monitored in real time by the digital oscilloscope.

[0031] Preferably, the method for controlling the number of cycles of the optical pulse signal in the loop includes:

[0032] When the optical pulse signal needs to continue to circulate in the loop for the next round, the driving signal provided by the second digital delay generator device must be at a high level, so that the second acousto-optic modulator realizes the role of a closed optical switch to ensure that the optical pulse signal can pass through the second acousto-optic modulator again to enter the loop; since the second acousto-optic modulator and the third acousto-optic modulator are in opposite phases, at this time the third acousto-optic modulator is in an open optical switch state, so in this state the spectrum display module will not receive the optical pulse signal; and when the optical pulse signal reaches the required number of circulation rounds, by appropriately controlling the driving signal provided by the second digital delay generator device so that the second acousto-optic modulator is open and the third acousto-optic modulator is closed, the second acousto-optic modulator blocks the to-be-measured optical pulse signal from continuing to transmit in the loop, and the to-be-measured optical pulse signal passes through the third acousto-optic modulator to reach the spectrum display module.

[0033] Compared with the prior art, the application has the following beneficial effects:

[0034] The application can flexibly adjust the spectral measurement resolution of the optical pulse signal according to actual needs; at the same time, the spectral measurement refresh rate of the optical pulse signal can also be flexibly controlled according to actual needs. In addition, by using the mode of the loop, the cost and time of building a dispersion optical fiber are reduced, while meeting the experimental demand for a large amount of dispersion; at the same time, the application has strong real-time performance, high stability and good sensitivity in optical pulse spectrum monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0036] Figure 1 The system structure schematic diagram of the first embodiment of the application;

[0037] Figure 2 The spectrum schematic diagram of the original optical pulse signal of the second embodiment of the application;

[0038] Figure 3 The system measurement effect schematic diagram of the second embodiment of the application.

[0039] Explanation of reference numerals in the attached figures: S101, First digital delay generator; S102, Mode-locked laser; S103, First acousto-optic modulator; S104, Dispersion compensation fiber; S105, Second acousto-optic modulator; S106, Third acousto-optic modulator; S107, Second digital delay generator; S108, Optical amplifier; S109, First 3dB coupler; S1010, Second 3dB coupler; S1011, Photodetector; S1012, Digital oscilloscope. Detailed Implementation

[0040] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0041] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Example 1

[0043] like Figure 1 As shown in the schematic diagram of the system structure of this application embodiment, it includes: a pulse extraction module, a loop control module, and a spectrum display module; wherein, the pulse extraction module is used to generate a first optical pulse signal and perform selective extraction to adjust the repetition frequency of the first optical pulse signal to obtain a second optical pulse signal; the loop control module is used to control the number of cycles of the second optical pulse signal in the loop, and to load a dispersive element in the loop to realize the mapping of the spectrum of the optical pulse signal in the time dimension to generate the optical pulse signal to be measured; the spectrum display module is used to perform photoelectric conversion on the optical pulse signal to be measured, and to complete the real-time monitoring of the time-domain waveform of the optical pulse signal through a digital oscilloscope.

[0044] The pulse extraction module includes: a first digital delay generator S101, a mode-locked laser S102, and a first acousto-optic modulator S103; wherein, the mode-locked laser S102 is used to emit a first optical pulse signal, the first acousto-optic modulator S103 is used to selectively extract the first optical pulse signal, and the first digital delay generator S101 is used to control the first acousto-optic modulator and synchronize with the mode-locked laser.

[0045] The first digital delay generator S101 can be triggered by an external signal and frequency divided to obtain the required control signal. The mode-locked laser S102 can emit high-power, high-repetition-rate, and wide-bandwidth femtosecond optical pulse signals. The first acousto-optic modulator S103 can selectively extract the optical pulse signal emitted by the mode-locked laser S102 via the control signal of the first digital delay generator S101.

[0046] The loop control module includes: dispersion compensation fiber S104, second acousto-optic modulator S105, third acousto-optic modulator S106, second digital delay generator S107, optical amplifier S108, first 3dB coupler S109, and second 3dB coupler S1010; wherein the dispersion compensation fiber S104 is used to realize the time-dimensional mapping of the optical pulse signal spectrum; the second acousto-optic modulator S105 is used to control whether the optical pulse signal re-enters the loop through the coupler; the third acousto-optic modulator S106 is used for... The system controls whether the light pulse enters the spectrum display module; the second digital delay generator S107 is used to perform radio frequency control on the second acousto-optic modulator S105 and the third acousto-optic modulator S106; the optical amplifier S108 is used to amplify the second light pulse signal to compensate for loop loss; in this embodiment, the 3dB coupler consists of a first 3dB coupler S109 and a second 3dB coupler S1010; the first 3dB coupler S109 and the second 3dB coupler S1010 are used to realize the connection between the loop and the front and rear modules.

[0047] The spectrum display module includes: a photoelectric detection device S1011 and a digital oscilloscope S1012; the photoelectric detection device S1011 is used to complete the photoelectric conversion of the light pulse signal under test; the digital oscilloscope S1012 is used for real-time monitoring of the time domain waveform of the light pulse signal under test to obtain the monitoring results.

[0048] Example 2

[0049] The application of this system in real life will be described in detail below with reference to this embodiment.

[0050] The external electrical output terminal of the mode-locked laser S102 is connected to the external trigger input interface of the first digital delay generator S101 to complete the synchronization and stabilization function of the two instruments. The first digital delay generator S101 pre-divides the external trigger signal and connects the frequency-divided output electrical pulse to the RF interface of the first acousto-optic modulator S103. The optical pulse output terminal of the mode-locked laser S102 is connected to the optical signal modulation interface of the first acousto-optic modulator S103. Through the frequency-divided electrical pulse control of the first digital delay generator S101, the acousto-optic modulator S103 completes the pulse extraction of the laser source, realizes the change of the optical pulse signal repetition rate, and thus achieves controllable refresh rate of the real-time spectral system.

[0051] Compared with common single-mode fiber, the dispersion compensation fiber S104 in the loop control module can provide a larger amount of dispersion for the system at the same length. The second acousto-optic modulator S105 and the third acousto-optic modulator S106 are controlled by the same drive signal but are opposite to each other; the second acousto-optic modulator S105 and the third acousto-optic modulator S106 have a unique advantage and can be used as an optical switch; the second digital delay generator S107 can adjust the delay time and pulse width of the output drive signal, which is used to control the second acousto-optic modulator S105 and the third acousto-optic modulator S106 to complete the control function of the in-out circulation of the optical pulse. The optical amplifier S108 can amplify the power of the optical pulse signal to make up for the loss caused by the coupler, optical switch and fiber link. The first 3dB coupler S109 and the second 3dB coupler S1010 can realize the distribution or combination of optical signal power among different optical fibers.

[0052] The delay time and pulse width of the output drive signal of the second digital delay generator S107 are adjusted, which is used to control the second acousto-optic modulator S105 and the third acousto-optic modulator S106 to complete the control function of the in-out circulation of the optical pulse. The second optical pulse signal enters the loop transmission through the first 3dB coupler S109, and the dispersion compensation fiber S104 and the optical amplifier S108 carried by the loop realize the mapping of the optical pulse signal spectrum in the time dimension and the amplification of the optical power, respectively. After a certain loop delay, the optical pulse signal reaches the loop output end, and the second 3dB coupler S1010 divides the optical pulse signal into two parts in proportion, which are transmitted to the third acousto-optic modulator S106 and the next module, respectively. Driven by the control signal, the loop control system completes the control of the second acousto-optic modulator S105 and the third acousto-optic modulator S106 which are opposite to each other, realizes the effect of optical pulse circulation for multiple turns and in-out of the loop. When the second optical pulse signal needs to continue to circulate in the loop for the next turn, the drive signal provided by the second digital delay generator S107 must be at a high level, so that the second acousto-optic modulator S105 realizes the function of a closed optical switch to ensure that the second optical pulse signal can enter the loop again through the second acousto-optic modulator S105. Since the second acousto-optic modulator S105 and the third acousto-optic modulator S106 are opposite to each other, the third acousto-optic modulator S106 is in an open optical switch state at this time, so in this state, the next module will not receive the optical pulse signal. When the optical pulse signal reaches the required circulation number, the drive signal provided by the second digital delay generator S107 is appropriately controlled so that the second acousto-optic modulator S105 is open and the third acousto-optic modulator S106 is closed, the second acousto-optic modulator S105 blocks the optical pulse signal from continuing to transmit in the loop, and the optical pulse signal reaches the next module through the third acousto-optic modulator S106. By controlling the circulation number of the optical pulse, the size of the total dispersion of the system can be controlled to realize the reconfiguration of the resolution.

[0053] The calculation expression of system resolution is as follows:

[0054]

[0055] Wherein, n represents the number of cycles of the optical pulse signal, D represents the group velocity dispersion value of the dispersion compensation fiber S104, L represents the length value of the dispersion compensation fiber, f s represents the sampling frequency of the oscilloscope.

[0056] Finally, the photoelectric conversion of the optical pulse signal is completed by the photoelectric detection device S1011, and the real-time monitoring of the time-domain waveform thereof is completed in the digital oscilloscope S1012.

[0057] As can be seen from the above expression: when the characteristic parameters of the dispersion compensation fiber and the sampling rate of the digital oscilloscope S1012 are certain, changing the number of cycles of the optical pulse signal in the loop can control the change of the system resolution, the higher the number of cycles, the better the system resolution. For example, in the actual setting, the group velocity dispersion value of the dispersion compensation fiber is 17x10 -6 ps / nm 2 , the length value of the dispersion compensation fiber is 6000m, the sampling rate of the digital oscilloscope S1012 is 20GSa / s, and the number of cycles is 1, the theoretical system resolution is 3.9216nm; when only the number of cycles of the optical pulse signal in the loop is changed to 10, the theoretical system resolution is 0.3922nm; when the number of cycles of the optical pulse signal in the loop is 40, the theoretical system resolution is 0.098nm. In order to verify, the time-domain waveform received at the spectrum display module after the optical pulse signal is circulated in the loop for 1, 10 and 40 cycles respectively is as Figure 3 .

[0058] The center frequency of the input optical pulse signal is 193.1THz, and the 3dB bandwidth is about 15nm, and it has passed two band-stop filters with center frequencies of 193.2THz and 193THz and bandwidths of 0.8nm. Figure 2 The spectrum diagram of the original optical pulse signal is given as Figure 3 a reference for the system measurement effect diagram. It can be seen that in the result diagram, the more the number of cycles, the more detailed spectral information can be shown. When the optical pulse signal is circulated in the loop for only 1 cycle, only the general envelope of the spectrum can be seen in the result diagram, and with the increase of the number of cycles, the system resolution is better, so that the characteristic spectrum of the band-stop filter can be directly observed.

[0059] The application utilizes pulse extraction to change the repetition rate of the optical pulse signal, and utilizes loop control to realize the effect of multiplying or reducing the dispersion amount, so that the controllable measurement refresh rate and resolution are realized at the same time without changing the experimental device, and the spectral shape of the optical pulse signal can be monitored in real time.

[0060] The above-described embodiments are only descriptions of the preferred modes of the application, and do not limit the scope of the application. Without departing from the design spirit of the application, various modifications and improvements to the technical solutions of the application made by those skilled in the art shall fall within the protection scope determined by the claims of the application.

Claims

1. A reconfigurable real-time spectral measurement system, characterized by, The application relates to a pulse extraction module, a loop control module and a spectrum display module. The pulse extraction module is used for generating a first optical pulse signal and adjusting the repetition frequency of the first optical pulse signal to obtain a second optical pulse signal. The loop control module is used for controlling the size of the dispersion in the system to realize the mapping of the spectrum of the second optical pulse signal in the time dimension and obtain a to-be-detected optical pulse signal. The spectrum display module is used for photoelectric conversion of the to-be-detected optical pulse signal and real-time monitoring of the time-domain waveform of the to-be-detected optical pulse signal to obtain a monitoring result. The pulse extraction module comprises a mode-locked laser device, a first digital delay generation device and a first acousto-optic modulation device.

2. The reconfigurable real-time spectral measurement system of claim 1, wherein, The mode-locked laser device is used for emitting the first optical pulse signal. The first acousto-optic modulation device is used for selectively extracting the first optical pulse signal to realize the adjustment of the repetition frequency of the first optical pulse signal and obtain the second optical pulse signal. The first digital delay generation device is used for controlling the first acousto-optic modulation device and is synchronous with the mode-locked laser device. The loop control module comprises a 3dB coupling device, a dispersion element, an optical amplification device, a second digital delay generation device, a second acousto-optic modulation device and a third acousto-optic modulation device.

3. The reconfigurable real-time spectral measurement system of claim 1, wherein, The 3dB coupling device is used for controlling the input and output of the second optical pulse signal and the to-be-detected optical pulse signal into the loop. The dispersion element is used for mapping the spectrum of the second optical pulse signal in the time dimension. The second digital delay generation device is used for controlling the second acousto-optic modulation device and the third acousto-optic modulation device. The second acousto-optic modulation device is used for controlling whether the second optical pulse signal passes through the coupling device into the loop again. The third acousto-optic modulation device is used for controlling whether the second optical pulse signal enters the spectrum display module. The optical amplification device is used for amplifying the second optical pulse signal to compensate for the loss of the 3dB coupling device, the second acousto-optic modulation device, the third acousto-optic modulation device and the dispersion element and obtain the to-be-detected optical pulse signal. The spectrum display module comprises a photoelectric detection device and a digital oscilloscope.

4. The reconfigurable real-time spectral measurement system of claim 3, wherein, The photoelectric detection device is used for completing the photoelectric conversion of the to-be-detected optical pulse signal. The digital oscilloscope is used for real-time monitoring of the time-domain waveform of the to-be-detected optical pulse signal to obtain a monitoring result. The working process of the loop control module comprises:

5. The reconfigurable real-time spectral measurement system of claim 4, wherein, ​ When the second optical pulse signal needs to continue to circulate in the loop, the driving signal provided by the second digital delay generator must be at a high level, so that the second acousto-optic modulation device realizes the role of a closed optical switch, to ensure that the second optical pulse signal can pass through the second acousto-optic modulation device again to enter the loop; since the second acousto-optic modulation device and the third acousto-optic modulation device are in opposite phases, at this time the third acousto-optic modulation device is in an open optical switch state, so in this state the spectrum display module does not receive the optical pulse signal; and when the optical pulse signal reaches the required number of circulation, by appropriately controlling the driving signal provided by the second digital delay generator so that the second acousto-optic modulation device is open and the third acousto-optic modulation device is closed, the second acousto-optic modulation device blocks the to-be-tested optical pulse signal from continuing to transmit in the loop, and the to-be-tested optical pulse signal reaches the spectrum display module through the third acousto-optic modulation device.

6. The reconfigurable real-time spectral measurement system of claim 4, wherein, The method for obtaining the resolution of the monitoring result comprises: where n represents the number of cycles of the optical pulse signal, D represents the group velocity dispersion value of the dispersion compensation optical fiber, L represents the length value of the dispersion compensation optical fiber, f s represents the sampling frequency of the oscilloscope.

7. Use of a reconfigurable real-time spectroscopy measurement system for controlling a reconfigurable real-time spectroscopy measurement system according to any one of claims 1 to 6, characterized by the steps of comprising: First, the first digital delay generator is used to extract the optical pulse output by the mode-locked laser device, to change the repetition frequency of the optical pulse signal; Then, the loop control module is used to drive the second acousto-optic modulation device and the third acousto-optic modulation device to control the number of circulations of the optical pulse signal in the loop, and the dispersion element is carried in the loop to realize the mapping of the spectrum of the optical pulse signal in the time dimension; finally, the spectrum display module is used for photoelectric conversion of the optical pulse, and the digital oscilloscope is used to complete real-time monitoring of the time-domain waveform of the optical pulse signal.

8. The use of a reconfigurable real-time spectral measurement system according to claim 7, characterized in that, The method for controlling the number of circulations of the optical pulse signal in the loop comprises: When the optical pulse signal needs to continue to circulate in the loop, the driving signal provided by the second digital delay generator must be at a high level, so that the second acousto-optic modulation device realizes the role of a closed optical switch, to ensure that the optical pulse signal can pass through the second acousto-optic modulation device again to enter the loop; since the second acousto-optic modulation device and the third acousto-optic modulation device are in opposite phases, at this time the third acousto-optic modulation device is in an open optical switch state, so in this state the spectrum display module does not receive the optical pulse signal; and when the optical pulse signal reaches the required number of circulation, by appropriately controlling the driving signal provided by the second digital delay generator so that the second acousto-optic modulation device is open and the third acousto-optic modulation device is closed, the second acousto-optic modulation device blocks the to-be-tested optical pulse signal from continuing to transmit in the loop, and the to-be-tested optical pulse signal reaches the spectrum display module through the third acousto-optic modulation device.

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