A method for automatically identifying the state of a dual-optical comb using spectral information

Abstract

The present invention discloses a method for automatically identifying a dual-comb state using spectral information, and the steps are as follows: realizing dual-comb pulses based on a traditional identification method, splitting the dual-comb into two single-comb signals and connecting them to two spectrometers respectively, collecting the two single-comb pulses to obtain the target spectral shape; obtaining the real-time spectral shape of two groups of equally spaced longitudinal mode comb teeth by photoelectric combination; and then calculating the similarity between the real-time spectral shape and the target dual-comb spectral shape to identify the dual-comb state. The present invention has the following beneficial effects: (1) Automatically identifying the dual-comb state using spectral information; (2) A method for obtaining the real-time spectral data of the optical comb for dual-comb state discrimination through a dispersive medium, an analog-to-digital converter and a computing unit; (3) Comparing the similarity between the real-time spectral data and the target spectral data, including calculation methods such as mean square error and correlation coefficient, and comparing the similarity with the threshold similarity to determine whether it is a dual-comb state.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic technology, and in particular relates to a method for automatically identifying a dual-optical comb state by using spectral information. Background Art

[0002] Optical frequency combs are referred to as light combs. In the time domain, they appear as a sequence of equally spaced ultrashort pulses. In the frequency domain, they appear as comb teeth of equally spaced longitudinal modes. The frequency difference between adjacent comb teeth is equal to the repetition frequency of the time domain pulse sequence. Professor Hall of the Joint Astrophysical Laboratory of the United States also won the 2005 Nobel Prize in Physics for the invention of the optical comb.

[0003] A dual-comb refers to a pair of optical combs with a small repetition frequency difference, which can achieve higher measurement accuracy and has better application prospects. In 2002, Professor Schiller first proposed the idea of ​​dual-comb measurement and verified its feasibility and effectiveness. However, the dual-comb system is complex to implement and difficult to achieve stable and high-precision adjustment, so the intelligent control of the dual-comb is particularly important. The intelligent control technology of the dual-comb mainly includes automatic recognition of the dual-comb pulse state and intelligent feedback control of the optical cavity. Automatic recognition of the dual-comb pulse state is a very important part of intelligent control.

[0004] At present, manual real-time observation and time-domain pulse information recognition are the common methods for dual-comb pulse state recognition. Manual real-time observation refers to the recognition of dual-comb pulses through devices such as oscilloscopes or spectrometers. This method cannot achieve real-time monitoring of pulses and the integration of intelligent dual-comb modules. The number of dual-comb pulses in a set time window is fixed. Time-domain pulse information recognition is to sample the pulses in the set time window through a high-speed analog-to-digital converter (ADC), and then count the pulses to recognize the dual-comb pulse state. This method requires the use of a high-sampling rate ADC and may lead to misjudgment. Summary of the invention

[0005] In order to solve the defects and shortcomings in the above-mentioned prior art, the present invention provides a method for automatically identifying the state of dual-comb pulses using spectral information, which is helpful to realize the integration of intelligent dual-comb modules and can realize accurate identification of the dual-comb pulse state under low ADC sampling rate conditions, and is efficient and easy to integrate.

[0006] The technical solution of the present invention is a method for automatically identifying the state of a dual optical comb using spectral information, the steps are as follows:

[0007] 1) Based on the traditional recognition method, the dual-comb pulse is realized, the dual-comb is split into two single-comb signals and connected to two spectrometers respectively, and the two single-comb pulses are collected to obtain the target spectral shape;

[0008] 2) Obtain the real-time spectral shape of two sets of equally spaced longitudinal mode comb lines through photoelectric combination;

[0009] 3) Then the similarity between the real-time spectral shape and the target dual-comb spectral shape is calculated to identify the dual-comb state.

[0010] Preferably, the step 1) is based on dual-wavelength mode locking, intracavity bidirectional transmission dual output ports or a multi-channel polarization multiplexing platform, and uses optical means to separate two groups of equally spaced longitudinal mode comb lines to obtain two single-comb pulses.

[0011] Preferably, the step 2) uses time-stretch-dispersion Fourier technology to achieve real-time sampling of two-way single-comb spectra.

[0012] Preferably, the time stretch-dispersion Fourier technique specifically utilizes dispersion to distinguish different wavelength components in the optical pulse, which can realize the mapping of spectral information in the time domain. Two single-comb pulses pass through the dispersive medium respectively, and then undergo photoelectric conversion through a photodiode. Finally, the analog-to-digital converter samples the two single-comb spectral data into a computing unit.

[0013] The present invention uses a dispersive medium to broaden the pulse to obtain the real-time spectrum of the pulse, which effectively reduces the requirements for the sampling rate of the analog-to-digital converter and proposes a judgment method based on the real-time spectrum. Compared with the judgment method of time-domain pulse counting, it can achieve more accurate judgment.

[0014] Preferably, a method for automatically identifying a dual-comb state using spectral information comprises the following specific steps: performing beam splitting based on the dual-comb implementation means, connecting the two single-comb signals after the beam splitting to two spectrometers respectively, manually adjusting the parameters of the laser cavity, and then manually observing whether the dual-comb state is achieved, and if so, storing the two sets of spectral data as target spectra; and recording the target spectral data as A and B respectively. target =[a t1 , a t2 , …, a tn ]

[0015] and B target =[b t1 , b t2 , …, b tn ],

[0016] a tn and b tn Represents the two-channel target single-comb amplitudes collected by the analog-to-digital converter at discrete point n;

[0017] When the dual-comb pulse state is recognized, the data received by the two analog-to-digital converters are recorded as A and real =[a r1 , ar2 , …, a rn ]

[0018] and B real =[b r1 , b r2 , …, b rn ]

[0019] a r1 and b r1 Represents the two-channel real-time single-comb amplitudes collected by the ADC discrete point n at time;

[0020] In the calculation unit, taking into account the different input powers, the coefficients are calculated separately:

[0021] k A =max(A target ) / max(A real )

[0022] k B =max(B target ) / max(B real )

[0023] Then calculate k A *A real and A target The similarity between A , k B *B real and B target The similarity between B ;

[0024] Assuming that the more similar the spectra are, the higher the similarity, then the similarity threshold is set to Q TH , when Q A +Q B >Q TH It can be determined that the current output waveform in the cavity is in a dual-comb state.

[0025] Preferably, the similarity Q A and Q B The mean square error method is used for calculation, and the calculation formula is as follows:

[0026]

[0027]

[0028] Preferably, the dual-wavelength mode-locked body refers to a dual-wavelength dual-comb spectrum containing two central wavelengths λ1 and λ2, laser is coupled out from the dual-comb cavity, and then divided into two beams through a coupler and passed through optical filters with central wavelengths λ1 and λ2 to obtain two single-comb pulses A and B.

[0029] Preferably, the two optical combs of the dual-polarization dual optical comb used in the multi-channel polarization multiplexing have the same central wavelength λ, but their polarization states are approximately orthogonal, so after coupling the laser out of the cavity, two single-comb pulses A and B can be obtained through a polarization controller and a polarization beam splitter.

[0030] Preferably, the intracavity bidirectional transmission dual output end specifically refers to the two optical combs of the bidirectional dual optical comb also having the same central wavelength λ, but the output directions from the cavity are different, so a fiber coupler is used to directly output two single comb pulses A and B from the cavity.

[0031] The beneficial effects of the present invention are as follows:

[0032] (1) Automatic identification of dual-comb states using spectral information;

[0033] (2) A method for obtaining real-time optical comb spectral data for dual optical comb state discrimination through a dispersive medium, an analog-to-digital converter (ADC), and a computing unit;

[0034] (3) By calculating the similarity between the real-time spectral data and the target spectral data (including calculation methods such as mean square error and correlation coefficient), and comparing the similarity with the threshold similarity, it is determined whether it is a dual-comb state. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of real-time sampling of two-channel single-comb spectra of the present invention;

[0036] Figure 2 Schematic diagram of dual-wavelength dual-comb spectrum;

[0037] Figure 3 Schematic diagram of dual-wavelength dual-comb beam splitting;

[0038] Figure 4 Schematic diagram of dual-polarization dual-comb spectrum;

[0039] Figure 5 Schematic diagram of dual-polarization dual-comb beam splitting;

[0040] Figure 6 Schematic diagram of bidirectional dual-comb spectrum;

[0041] Figure 7 Schematic diagram of bidirectional dual-comb beam splitting. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings, but this does not limit the protection scope of the present invention.

[0043] The dual-comb implementation schemes include dual-wavelength mode locking, intracavity bidirectional transmission dual output ports, and multi-channel polarization multiplexing. Figure 2The dual-wavelength dual-comb spectrum shown in the figure contains two central wavelengths λ1 and λ2. The laser is coupled out from the dual-comb cavity and then split into two beams through a coupler. Two single-comb pulses A and B are obtained through optical filters with central wavelengths λ1 and λ2. The beam splitting diagram is shown in the figure below. Figure 3 As shown. Figure 4 As shown in the figure, the two optical combs of the dual-polarization dual-optical comb have the same central wavelength λ, but the polarization states of the two are approximately orthogonal. Therefore, after coupling the laser out of the cavity, two single-comb pulses A and B can be obtained through the polarization controller and polarization beam splitter. The beam splitting diagram is as follows Figure 5 .like Figure 6 As shown in the figure, the two optical combs of the bidirectional dual optical comb also have the same central wavelength λ, but the directions of output from the cavity are different. Therefore, a fiber coupler can be used to directly output two single comb pulses A and B from the cavity. The beam splitting diagram is shown in Figure 7 shown.

[0044] In order to achieve real-time sampling of two-way single-comb spectra, the present invention uses a method for automatically identifying the dual-comb state using spectral information, which adopts the time-stretch-dispersion Fourier technique. The time-stretch-dispersion Fourier technique uses dispersion to distinguish different wavelength components in the optical pulse, and can achieve the mapping of spectral information in the time domain. Figure 1 As shown, two single-comb pulses pass through dispersive media (such as optical fiber, grating, etc.) respectively, and then undergo photoelectric conversion through a photodiode (PD). Finally, an analog-to-digital converter (ADC) samples the two single-comb spectral data into a calculation unit.

[0045] The specific steps are as follows:

[0046] Based on the realization of dual-comb, the beam is split, and the two single-comb signals after the splitting are connected to two spectrometers respectively. The parameters of the laser cavity are manually adjusted (such as polarization controller), and then it is manually observed whether the dual-comb state is achieved. If it is achieved, the two sets of spectral data are stored as the target spectrum; and the target spectrum data are recorded as A and B respectively. target =[a t1 , a t2 , …, a tn ]

[0047] and B target =[b t1 , b t2 , …, b tn ](a tn and b tn represents the two-channel target single comb amplitude collected by the analog-to-digital converter (ADC) at discrete point n. In the dual-comb pulse state recognition, the data received by the two-channel analog-to-digital converter (ADC) are recorded as

[0048] A real=[a r1 , a r2 , …, a rn ]

[0049] and B real =[b r1 , b r2 , …, b rn ](a r1 and b r1 Represents the two-channel real-time single-comb amplitude collected by the ADC discrete point n at time).

[0050] In the calculation unit, taking into account the different input powers, the coefficients are calculated separately:

[0051] k A =max(A target ) / max(A real )

[0052] k B =max(B target ) / max(B real )

[0053] Then calculate k A *A real and A target The similarity between A ,

[0054] k B *B real and V target The similarity between B Assuming that the more similar the spectra are, the higher the similarity, then the similarity threshold is set to Q TH , when Q1+Q B >Q TH It can be determined that the current cavity output waveform is in the dual-comb state. A and Q B It can be calculated using the mean square error method, and the calculation formula is as follows:

[0055]

[0056]

Claims

1. A method for automatically identifying the state of a dual optical comb using spectral information, characterized in that: Here are the steps: 1) Based on the traditional recognition method, the dual-comb pulse is realized, the dual-comb is split into two single-comb signals and connected to two spectrometers respectively, and the two single-comb pulses are collected to obtain the target spectral shape; 2) Obtain the real-time spectral shape of two sets of equally spaced longitudinal mode comb lines through photoelectric combination; 3) Then the similarity between the real-time spectral shape and the target dual-comb spectral shape is calculated to identify the dual-comb state; The step 1) uses optical means to separate two groups of equally spaced longitudinal mode comb lines based on dual-wavelength mode locking, intracavity bidirectional transmission dual output ports or a multi-channel polarization multiplexing platform to obtain two single-comb pulses; The step 2) uses time stretching-dispersion Fourier technology to achieve real-time sampling of two-way single-comb spectra; The method for automatically identifying the dual-comb state using spectral information has the following specific steps: Based on the realization of dual optical comb, the two single comb signals after beam splitting are connected to two spectrometers respectively. The parameters of the laser cavity are manually adjusted, and then it is manually observed whether the dual optical comb state is achieved. If it is achieved, the two sets of spectral data are stored as the target spectrum; and the target spectrum data are recorded as and , and Represents the discrete points of the analog-to-digital converter The two-channel single-comb amplitudes of the targets collected at all times; When the dual-comb pulse state is recognized, the data received by the two analog-to-digital converters are recorded as and , and Indicates ADC discrete points Two channels of real-time single-comb amplitudes collected at all times; In the calculation unit, taking into account the different input powers, the coefficients are calculated separately: ， ， Then calculate and Similarity between , and Similarity between ; Set the similarity threshold to ,when It can be determined that the current output waveform in the cavity is in a dual-comb state.

2. The method for automatically identifying the state of a dual optical comb using spectral information according to claim 1, characterized in that: The time stretch-dispersion Fourier technique specifically uses dispersion to distinguish different wavelength components in light pulses, which can realize the mapping of spectral information in the time domain. Two single-comb pulses pass through the dispersive medium respectively, and then undergo photoelectric conversion through a photodiode. Finally, the analog-to-digital converter samples the two single-comb spectral data into the computing unit.

3. The method for automatically identifying the state of a dual optical comb using spectral information according to claim 1, characterized in that: Similarity and The mean square error method is used for calculation, and the calculation formula is as follows: ， 。 4. The method for automatically identifying the state of a dual optical comb using spectral information according to claim 1, characterized in that: The dual-wavelength mode-locked body refers to the dual-wavelength dual-comb spectrum containing two central wavelengths and , the laser is coupled out from the dual-comb cavity, and then split into two beams through the coupler with a central wavelength of and Two single-comb pulses A and B are obtained through the optical filter.

5. The method for automatically identifying the state of a dual optical comb using spectral information according to claim 1, characterized in that: The two optical combs of the dual polarization dual optical comb used in the multi-channel polarization multiplexing have the same central wavelength. However, the polarization states of the two are approximately orthogonal. Therefore, after coupling the laser out of the cavity, two single-comb pulses A and B can be obtained through the polarization controller and polarization beam splitter.

6. The method for automatically identifying the state of a dual optical comb using spectral information according to claim 1, characterized in that: The intracavity bidirectional transmission dual output port specifically refers to the two optical combs of the bidirectional dual optical comb having the same central wavelength. , but the directions of output from the cavity are different, so a fiber coupler is used to directly output two single-comb pulses A and B from the cavity.

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