A soliton pulse spacing regulation method based on nonlinear Fourier transform

Abstract

The application belongs to the field of fiber lasers, and particularly relates to a soliton pulse interval regulation method based on nonlinear Fourier transform, which comprises sequentially performing intensity normalization and nonlinear Fourier transform on full-field information of multiple soliton pulses to obtain nonlinear spectrum, and extracting each eigenvalue and corresponding discrete spectrum therefrom; identifying the eigenvalue set according to the size of the imaginary part of the eigenvalue to obtain a discrete spectrum set corresponding to the soliton pulse; determining the discrete spectrum corresponding to each soliton pulse according to the intensity size relationship of the multiple soliton pulses; regulating the modulus of the discrete spectrum corresponding to the soliton pulse according to the current interval and the required interval of any two soliton pulses in the time domain to realize the movement of the soliton pulse in the time domain and achieve the required interval; and performing inverse nonlinear Fourier transform on the nonlinear spectrum obtained after regulation to obtain the soliton pulse after interval regulation. The application guarantees the quality of the signal while regulating the interval of the soliton pulse.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fiber lasers, and more particularly, to a soliton pulse spacing regulation method based on nonlinear Fourier transform. BACKGROUND

[0002] The current human society is in a rapidly developing technology era, and the amount of information generated by production and life is increasing day by day. The widespread dissemination of a large amount of information is gradually eroding the available bandwidth capacity. Optical fiber transmission system has attracted widespread attention due to its high transmission rate, large channel capacity, and no transmission distance limitation. Since the optical soliton can keep the shape unchanged along the fiber, it becomes an ideal information carrier in the optical fiber transmission and is expected to be widely used in future large-capacity long-distance transmission system. In order to further improve the transmission capacity, multi-soliton can be used as an information carrier, which not only has the same transmission stability as single soliton, but also has greater data carrying capacity, and can be applied to new encoding methods to increase the number of information bits transported per cycle time.

[0003] However, the application of multi-soliton pulse in the field of communication still needs to overcome some problems, among which the soliton spacing in the multi-soliton must be controllable. The traditional method indirectly realizes the regulation of multi-soliton pulse spacing by adjusting the gain, dispersion, nonlinearity and other parameters in the laser cavity, which is difficult to directly and accurately control the spacing, and the change of laser parameters is easy to affect the stability of the generated multi-soliton, which has great limitations. SUMMARY

[0004] In view of the defects and improvement needs of the prior art, the present application provides a soliton pulse spacing regulation method based on nonlinear Fourier transform, which aims to regulate the soliton pulse spacing while ensuring the quality of the signal.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present application, a soliton pulse spacing regulation method based on nonlinear Fourier transform is provided, comprising:

[0006] Collecting the full-field information output by the fiber laser to obtain full-field information containing multiple soliton pulses;

[0007] After intensity normalization of the full-field information, nonlinear Fourier transform is performed to transform the time-domain soliton pulse to the nonlinear frequency domain to obtain a nonlinear frequency spectrum, and each eigenvalue and its corresponding discrete spectrum are extracted from the nonlinear frequency spectrum;

[0008] According to the magnitude of the imaginary part of the eigenvalue, the eigenvalue corresponding to the soliton pulse is identified from the eigenvalues, and a set of eigenvalues is obtained, so that a set of discrete spectra corresponding to the soliton pulse is obtained; according to the intensity size relationship of the plurality of soliton pulses, the discrete spectrum corresponding to each soliton pulse is determined from the set of discrete spectra;

[0009] According to the current interval and the required interval of any two soliton pulses in the time domain, a to-be-moved amount in the time domain is assigned to each soliton pulse in the any two soliton pulses, the modulus value of the discrete spectrum corresponding to each soliton pulse is regulated, so that the soliton pulse moves by the to-be-moved amount in the time domain, and the required interval is realized;

[0010]

[0011] Further, the implementation manner of identifying the eigenvalue corresponding to the soliton pulse from the eigenvalues is:

[0012] The observed intensity corresponding to each soliton pulse is assigned to I in formula I = 2Im(λ k ), and the calculated Im(λ k ) is taken as the approximate imaginary part value of the eigenvalue of the soliton pulse;

[0013] According to the plurality of approximate imaginary part values of the eigenvalues corresponding to the plurality of soliton pulses, the eigenvalues corresponding to the sidebands are eliminated from all the eigenvalues, and the eigenvalues corresponding to the soliton pulses are obtained.

[0014] Further, the implementation manner of determining the discrete spectrum corresponding to each soliton pulse from the set of discrete spectra is:

[0015] The intensities of the plurality of soliton pulses are sorted according to the size, the sorting is one-to-one corresponding to the size sorting of the imaginary part of the eigenvalue in the set of eigenvalues, the corresponding relationship between the soliton pulse and the eigenvalue is determined, so that the corresponding relationship between the soliton pulse and the discrete spectrum is determined, and the discrete spectrum corresponding to each soliton pulse is obtained.

[0016] Further, when regulating the modulus value of the discrete spectrum corresponding to the soliton pulse k, the following formula is used to realize:

[0017] |Q′ d (λ k )| = exp[ln(|Q d (λ k )|) + 2Im(λ k )Δt]

[0018] In the formula, |Q′ d (λ k )| represents the changed discrete spectrum Q′​d (λ k ) the modulus of the discrete spectrum Q d (λ k ) before the change; Im(λ d (λ k ) the modulus of the discrete spectrum Q k (λ k ) of the current soliton pulse k; Δt represents the amount to be moved in the time domain allocated to the current soliton pulse k.

[0019] Further, when the amount to be moved in the time domain is allocated to each of the two soliton pulses, the amount to be moved in the time domain of one of the soliton pulses is 0, and the amount to be moved in the time domain of the other soliton pulse is the deviation amount of the current interval and the required interval.

[0020] The present application also provides a computer program product comprising a computer program which, when executed by a processor, implements the steps of the soliton pulse interval regulation method as described above.

[0021] The present application also provides a computer-readable storage medium, characterized in that the computer-readable storage medium comprises a stored computer program, wherein the computer program, when executed by a processor, controls the device in which the storage medium is located to perform the soliton pulse interval regulation method as described above.

[0022] Overall, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0023] The present application proposes a soliton pulse interval regulation method, which collects full-field information of a plurality of soliton pulses and extracts eigenvalues and corresponding discrete spectra through transformation, identifies eigenvalues corresponding to soliton pulses from the eigenvalues according to the size of the imaginary part of the eigenvalues, obtains an eigenvalue set, and thereby obtains a discrete spectrum set corresponding to the soliton pulses; determines the discrete spectrum corresponding to each soliton pulse from the discrete spectrum set according to the intensity size relationship of the plurality of soliton pulses; allocates an amount to be moved in the time domain to each soliton pulse of any two soliton pulses according to the current interval and the required interval of the two soliton pulses in the time domain, regulates the modulus of the discrete spectrum corresponding to each soliton pulse, and realizes the movement of the soliton pulse in the time domain by the corresponding amount to be moved, thereby realizing the required interval. The present application can directly and quantitatively change the position of each soliton in the time domain, and thereby realize accurate regulation of the soliton interval, and provide a high-quality signal source for a fiber communication system. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 A flowchart of a soliton pulse interval regulation method based on nonlinear Fourier transform is provided for the embodiments of the present application.

[0025] Figure 2 The following are time-domain waveforms, frequency-domain spectra, eigenvalue distribution maps, and discrete spectrum distribution maps of fiber laser output soliton pulses provided in embodiments of the present invention, wherein (a) is a time-domain waveform map, (b) is a frequency-domain spectrum map, (c) is an eigenvalue distribution map, and (d) is a discrete spectrum distribution map;

[0026] Figure 3 Regulation provided for embodiments of the present invention Figure 1 A schematic diagram of the position of soliton pulse 1; where (a) is the result of changing the magnitude of the discrete spectrum corresponding to soliton pulse 1 from |Q d (λ1)|=5.816×10 -24 Increase to |Q′ d (λ1)|=2.374×10 -10 (a) is a schematic diagram of the modulation, and (b) is a time-domain waveform obtained by inverse nonlinear Fourier transform after modulation corresponding to (a); (c) is a diagram of the modulus of the discrete spectrum corresponding to soliton pulse 1 from |Q d (λ1)|=5.816×10 -24 Reduce to |Q′ d (λ1)|=1.425×10 -37 (d) is a schematic diagram of the regulation; (c) is the time-domain waveform obtained by inverse nonlinear Fourier transform after regulation corresponding to (c).

[0027] Figure 4 Regulation provided for embodiments of the present invention Figure 1 A schematic diagram of the position of soliton pulse 2; where (a) is the result of changing the magnitude of the discrete spectrum corresponding to soliton pulse 2 from |Q d (λ2)|=3.455×10 25 Increase to |Q′ d (λ2)|=7.070×10 33 (a) is a schematic diagram of the modulation; (b) is a time-domain waveform obtained by inverse nonlinear Fourier transform after modulation corresponding to (a); (c) is a diagram of the modulus of the discrete spectrum corresponding to soliton pulse 2 from |Q d (λ2)|=3.455×10 25 Reduce to |Q′ d (λ2)|=1.688×10 17 (d) is a schematic diagram of the regulation; (c) is the time-domain waveform obtained by inverse nonlinear Fourier transform after regulation corresponding to (c). Detailed Implementation

[0028] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0029] Embodiment one

[0030] A soliton pulse spacing regulation method based on nonlinear Fourier transform, as shown in Figure 1 , comprises:

[0031] Collecting full-field information output by a fiber laser to obtain full-field information containing multiple soliton pulses;

[0032] After intensity normalization of the full-field information, nonlinear Fourier transform is performed to transform the time-domain soliton pulses to the nonlinear frequency domain to obtain a nonlinear frequency spectrum, and each eigenvalue and its corresponding discrete spectrum are extracted from the nonlinear frequency spectrum;

[0033] According to the size of the imaginary part of the eigenvalue, the eigenvalue corresponding to the soliton pulse is identified from each eigenvalue to obtain an eigenvalue set, so as to obtain a discrete spectrum set corresponding to the soliton pulse; according to the intensity size relationship of the above multiple soliton pulses, the discrete spectrum corresponding to each soliton pulse is determined from the discrete spectrum set;

[0034] According to the current spacing and the required spacing of any two soliton pulses in the time domain, a to-be-moved amount in the time domain is allocated to each soliton pulse in the any two soliton pulses, the modulus value of the discrete spectrum corresponding to each soliton pulse is regulated, so as to realize the movement of the soliton pulse in the time domain by the to-be-moved amount, and realize the required spacing;

[0035] Inverse nonlinear Fourier transform is performed on the nonlinear frequency spectrum obtained after the above regulation to obtain soliton pulses after spacing regulation.

[0036] The above multiple soliton pulses include but are not limited to two. The full-field information of the multiple soliton pulse signals includes intensity and phase information. The intensity normalization operation is performed on the pulse full-field information. Specifically, the pulse intensity is normalized according to the pulse energy:

[0037]

[0038] Wherein, q is the amplitude of the soliton pulse, Q s is a normalization coefficient related to the pulse energy, for example, Q s = 0.456, q' is the normalized pulse amplitude.

[0039] Each time-domain soliton pulse and sideband in the soliton pulse corresponds to an eigenvalue and a discrete spectrum in the nonlinear domain. The eigenvalue and the corresponding discrete spectrum extracted from the nonlinear spectrum contain the eigenvalue and the discrete spectrum of the sideband. Each eigenvalue and the discrete spectrum form a set of data corresponding to a time-domain soliton pulse or a coherent sideband. Considering that the imaginary part of the eigenvalue is related to the intensity of the time-domain soliton or the sideband, and the modulus of the discrete spectrum is related to the position (time center) of the time-domain soliton, the corresponding eigenvalue and the discrete spectrum of the soliton are distinguished by the value of the imaginary part of the eigenvalue.

[0040] As a preferred embodiment, the implementation of identifying the eigenvalue corresponding to the soliton pulse from the eigenvalues is as follows:

[0041] The observed intensity corresponding to each soliton pulse is assigned to I in formula I = 2Im(λ k ), and the calculated Im(λ k ) is taken as the approximate imaginary part of the eigenvalue of the soliton pulse.

[0042] According to the approximate imaginary parts of the eigenvalues corresponding to the multiple soliton pulses, the eigenvalues corresponding to the sidebands are removed from all the eigenvalues, and the eigenvalues corresponding to the soliton pulses are obtained.

[0043] In theory, the imaginary part of the eigenvalue is related to the intensity of the soliton or the sideband, and the corresponding relationship is as follows:

[0044] I = 2Im(λ k )

[0045] where I is the intensity of the soliton or the sideband, λ k is the eigenvalue of the soliton or the sideband, and Im(λ k ) represents the imaginary part of the eigenvalue.

[0046] The actual observed intensity contains the intensity of the sideband, which is not the actual intensity of the soliton pulse itself. Here, the observed intensity is approximated as the intensity of the soliton pulse to obtain an approximate imaginary part of the eigenvalue of the soliton pulse, which is used to identify the eigenvalue of the soliton pulse. Since the imaginary part of the eigenvalue of the sideband is significantly different from the imaginary part of the eigenvalue of the soliton pulse, this method is effective, and it is reliable after subsequent verification.

[0047] As a preferred embodiment, the implementation of determining the discrete spectrum corresponding to each soliton pulse from the set of discrete spectra is as follows:

[0048] The intensities of the multiple soliton pulses are sorted according to the size, and the sorting is one-to-one corresponding to the size sorting of the imaginary parts of the eigenvalues in the set of eigenvalues to determine the correspondence between the soliton pulses and the eigenvalues, thereby determining the correspondence between the soliton pulses and the discrete spectra, and obtaining the discrete spectrum corresponding to each soliton pulse.

[0049] As a preferred implementation, the following formula can be used to adjust the magnitude of the discrete spectrum corresponding to the soliton pulse k:

[0050] |Q′ d (λ k )|=exp[ln(|Q d (λ k )|)+2Im(λ k )Δt]

[0051] In the formula, |Q′ d (λ k | represents the modified discrete spectrum Q′ corresponding to the current soliton pulse k. d (λ k The modulus of |Q; d (λ k | represents the discrete spectrum Q before modification corresponding to the current soliton pulse k. d (λ k The modulus of ); Im(λ k ) represents the eigenvalue λ of the current soliton pulse k. k The imaginary part; Δt represents the amount of time-domain shift allocated to the current soliton pulse k.

[0052] Theoretically, the magnitude of the discrete spectrum is related to the position (time center) of the corresponding time-domain soliton pulse, and the correspondence is as follows:

[0053]

[0054] in, Let |Q be the theoretical position of the soliton pulse (i.e., the theoretical time center of the pulse). d (λ k )| represents the modulus of the discrete spectrum.

[0055] When other soliton pulses are present, the influence of the interaction between soliton pulses on the time center needs to be considered. The theoretical formula is as follows:

[0056]

[0057] Among them, t k To account for the true position of the soliton pulses after interaction correction, the second term on the right-hand side of the equation describes the interaction exerted by soliton pulse j on soliton pulse k. `sign` is the sign function; when soliton pulse k is to the right of soliton pulse j, A function value of 1 indicates that the interaction exerted by soliton pulse j causes a positive shift in the position of soliton pulse k; conversely, a value of -1 indicates a negative shift in the position of soliton pulse k.

[0058] This embodiment proposes adjusting the magnitude of the discrete spectrum corresponding to the soliton pulse to change the position of the corresponding time-domain soliton pulse, thereby controlling the soliton pulse spacing. If the position of soliton pulse k is to be moved by Δt = t′... k -t k Based on the above formula, the following formula can be derived:

[0059] |Q′ d (λ k )|=exp[ln(|Q d (λ k )|)+2Im(λ k )Δt]

[0060] Where |Q′ d (λ k )| represents the modulus of the discrete spectrum corresponding to the soliton k after modulation.

[0061] As a preferred implementation, when allocating a shift amount in the time domain for each of any two soliton pulses, the shift amount in the time domain for one soliton pulse is 0, and the shift amount in the time domain for the other soliton pulse is the deviation between the current spacing and the required spacing, so as to facilitate calculation and control.

[0062] To verify the effectiveness of this embodiment, the following example is provided:

[0063] The fiber laser has a total cavity length of 5.6 meters, consisting of a 2.6-meter single-mode fiber and a 3-meter erbium-doped fiber. The dispersion parameter of the fibers within the cavity is -23 ps. 2 / km, mode-locking is achieved through nonlinear polarization rotation technology. Stable soliton pulse output is obtained by adjusting the pump power. For example... Figure 2 The image shows the normalized output of a dual soliton pulse from a fiber laser. Among them, Figure 2 (a) in the figure represents the time-domain waveform. Figure 2 (b) in the diagram represents the frequency domain spectrum. The nonlinear spectrum of a soliton pulse consists of a continuous spectrum, eigenvalues, and a discrete spectrum. The continuous spectrum represents the continuous wave background in the pulse, which is directly removed in this example. The imaginary parts of the eigenvalues ​​correspond to the intensities of the soliton and sidebands. Figure 2 In the equation (c), the corresponding eigenvalues ​​are given. The eigenvalues ​​with larger imaginary parts are those corresponding to the two solitons, while the eigenvalues ​​with smaller imaginary parts are those corresponding to the sidebands. The eigenvalues ​​corresponding to soliton pulse 1 and soliton pulse 2 are λ1 = 0.215 + 3.134i and λ2 = 0.217 + 3.190i, respectively. Figure 2 In the diagram, (d) represents the corresponding discrete spectrum, and there is a one-to-one correspondence between the discrete spectrum and the eigenvalues. The moduli of the discrete spectrum corresponding to the soliton are |Q|. d (λ1)|=5.816×10 -24 and|Q d(λ2)|=3.455×10 25 .for Figure 2 In (c) and (d), each soliton pulse uniquely corresponds to an eigenvalue and a discrete spectrum; the rest are the eigenvalues ​​and discrete spectra corresponding to coherent sidebands.

[0064] like Figure 3 As shown, by adjusting the magnitude of the discrete spectrum corresponding to the soliton pulse, the time-domain soliton pulse with the changed position can be obtained through inverse nonlinear Fourier transform. Figure 3 (a) and Figure 3 In (c), the sideband and the discrete spectrum corresponding to soliton pulse 2 are ignored, and only the discrete spectrum corresponding to soliton pulse 1 is controlled. Figure 3 In (a) of the diagram, the magnitude of the discrete spectrum corresponding to soliton pulse 1 is changed from |Q d (λ1)|=5.816×10 -24 Increase to |Q′ d (λ1)|=2.374×10 -10 (Discrete spectrum Q) d (λ1) is a solid hexagonal star, Q′ d (λ1) is a hollow hexagon. Figure 3 In (b), the time-domain waveform is obtained by inverse nonlinear Fourier transform after increasing the magnitude of the discrete spectrum corresponding to soliton pulse 1. Soliton pulse 1 is shifted to the right by 5 ps. Figure 3 In (c), the magnitude of the discrete spectrum corresponding to soliton pulse 1 is changed from |Q d (λ1)|=5.816×10 -24 Reduce to |Q′ d (λ1)|=1.425×10 -37 (Discrete spectrum Q) d (λ1) is a solid hexagonal star, Q′ d (λ1) is a hollow hexagon. Figure 3 In the figure, (d) is the time-domain pulse waveform recovered by inverse nonlinear Fourier transform after reducing the magnitude of the discrete spectrum corresponding to soliton pulse 1. Soliton pulse 1 is shifted to the left by 5 ps.

[0065] Specifically, to shift soliton pulse 1 5 ps to the right, according to the aforementioned formula, the modulus of the discrete spectrum corresponding to soliton pulse 1 should be shifted from |Q... d (λ1)|=5.816×10 -24 Increase to |Q′ d (λ1)|=2.374×10 -10 ,like Figure 3 As shown in Figure (a). The remaining eigenvalues ​​and discrete spectra remain unchanged. Then, the eigenvalues ​​and discrete spectra corresponding to solito pulses 1 and 2 are subjected to an inverse nonlinear Fourier transform to obtain time-domain pulses, as shown in Figure (a).Figure 3 As shown in Figure (b), the eigenvalues ​​and discrete spectra corresponding to the continuous spectrum and sidebands are removed during the inverse transform, corresponding to the removal of the continuous wave background in the time domain. Figure 3 Figure (b) shows pure solitons without a continuous wave background. The position of soliton pulse 1 on the left moves from -9.291 ps to -4.291 ps, shifting 5 ps to the right, while the position of soliton pulse 2 remains unchanged. To shift soliton pulse 1 5 ps to the left, according to the aforementioned formula, the modulus of the discrete spectrum corresponding to soliton pulse 1 should be shifted from |Q... d (λ1)|=5.816×10 -24 Reduce to |Q′ d (λ1)|=1.425×10 -37 ,like Figure 3 As shown in Figure (c). The remaining eigenvalues ​​and discrete spectrum remain unchanged. The time-domain pulse after the inverse nonlinear Fourier transform is as follows: Figure 4 As shown in Figure (d), the position of soliton pulse 1 on the left moves from -9.291 ps to -14.291 ps, shifting 5 ps to the left, while the position of soliton pulse 2 remains unchanged.

[0066] like Figure 4 As shown, Figure 4 (a) and Figure 4 In (c), the sideband and the discrete spectrum corresponding to soliton pulse 1 are omitted, and only the discrete spectrum corresponding to soliton pulse 2 is controlled. Figure 4 In (a), the magnitude of the discrete spectrum corresponding to soliton pulse 2 is changed from |Q d (λ2)|=3.455×10 25 Increase to |Q′ d (λ2)|=7.070×10 33 (Discrete spectrum Q) d (λ2) is a solid hexagonal star, Q′ d (λ2) is a hollow hexagon. Figure 4 In (b), the time-domain waveform is obtained by inverse nonlinear Fourier transform after increasing the magnitude of the discrete spectrum corresponding to soliton pulse 2. Soliton pulse 2 is shifted to the right by 3 ps. Figure 4 In (c), the magnitude of the discrete spectrum corresponding to soliton pulse 2 is changed from |Q d (λ2)|=3.455×10 25 Reduce to |Q′ d (λ2)|=1.688×10 17 (Discrete spectrum Q) d (λ2) is a solid hexagonal star, Q′ d (λ2) is a hollow hexagon. Figure 4In the diagram, (d) represents the time-domain pulse waveform recovered by inverse nonlinear Fourier transform after reducing the magnitude of the discrete spectrum corresponding to soliton pulse 2. Soliton pulse 2 has shifted 3p to the left.

[0067] Specifically, to shift soliton pulse 2 3 ps to the right, the modulus of the discrete spectrum corresponding to soliton pulse 2 should be changed from |Q d (λ2)|=3.455×10 25 Increase to |Q′ d (λ2)|=7.070×10 33 ,like Figure 4 As shown in Figure (a). The eigenvalues ​​and discrete spectra of the remaining soliton pulses remain unchanged. Then, the eigenvalues ​​and discrete spectra corresponding to soliton pulses 1 and 2 are subjected to inverse nonlinear Fourier transform to obtain the time-domain pulses, as shown in Figure (a). Figure 4 As shown in Figure (b), the position of soliton pulse 1 on the left remains unchanged, while the position of soliton pulse 2 moves from 9.961 ps to 12.961 ps, shifting 3 ps to the right. To shift soliton pulse 2 3 ps to the left, the modulus of the discrete spectrum corresponding to soliton pulse 2 should be changed from |Q... d (λ2)|=3.455×10 25 Reduce to |Q′ d (λ2)|=1.688×10 17 ,like Figure 4 As shown in Figure (c). The remaining eigenvalues ​​and discrete spectrum remain unchanged. The time-domain pulse after the inverse nonlinear Fourier transform is as follows: ​ As shown in Figure (d), the position of soliton pulse 1 on the left remains unchanged, while the position of soliton pulse 2 moves from 9.961 ps to 6.961 ps, shifting 3 ps to the left. Therefore, by adjusting the magnitude of the discrete spectrum corresponding to the soliton in the nonlinear domain, the position of the soliton pulse in the time domain can be precisely controlled, thereby controlling the soliton pulse spacing.

[0068] In summary, this embodiment provides a method for controlling the spacing of soliton pulses using nonlinear Fourier transform technology. After acquiring the full-field information of the soliton pulses output from the fiber laser, the pulse intensity is normalized. Then, a nonlinear Fourier transform is performed to transform the time-domain pulses to the nonlinear domain, obtaining their eigenvalues ​​and discrete spectra. Next, this embodiment proposes a specific scheme for adjusting the discrete spectrum corresponding to the soliton pulses based on the eigenvalues ​​and discrete spectra. Finally, the eigenvalues ​​and the adjusted discrete spectra are subjected to an inverse nonlinear Fourier transform to obtain multiple soliton pulses with controlled spacing. This embodiment provides a method for controlling the spacing of soliton pulses in the field of fiber lasers, which can directly change the pulse position and precisely control the spacing of multiple pulses, providing a high-quality signal source for fiber optic communication systems.

[0069] Example 2

[0070] A computer program product comprising a computer program which, when executed by a processor, implements the steps of the soliton pulse spacing regulation method as described above.

[0071] The related technical solutions are the same as those of Embodiment One, and will not be described here again.

[0072] Embodiment Three

[0073] A computer-readable storage medium comprising a stored computer program, wherein the computer program, when executed by a processor, controls a device in which the storage medium is located to perform the soliton pulse spacing regulation method as described above.

[0074] The related technical solutions are the same as those of Embodiment One, and will not be described here again.

[0075] The present application provides a soliton pulse spacing regulation method in the field of fiber lasers, which can effectively regulate the soliton pulse spacing and provide more efficient and stable tool and technical support for the fields of optical fiber communication and ultrafast laser measurement.

[0076] Those skilled in the art will readily understand that the above description is only the preferred embodiments of the present application and is not intended to limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for controlling the spacing of soliton pulses based on nonlinear Fourier transform, characterized in that, include: The full-field information of the fiber laser output is collected to obtain full-field information containing multiple soliton pulses; After normalizing the intensity of the full-field information, a nonlinear Fourier transform is performed to transform the time-domain soliton pulse to the nonlinear frequency domain to obtain the nonlinear spectrum. From the nonlinear spectrum, each eigenvalue and its corresponding discrete spectrum are extracted. Based on the magnitude of the imaginary part of the eigenvalues, the eigenvalues ​​corresponding to the soliton pulses are identified from the eigenvalues ​​to obtain the eigenvalue set, thereby obtaining the discrete spectrum set corresponding to the soliton pulses; based on the intensity relationship of the multiple soliton pulses, the discrete spectrum corresponding to each soliton pulse is determined from the discrete spectrum set; Based on the current and required spacing between any two soliton pulses in the time domain, a shift amount is allocated to each of the two soliton pulses in the time domain, and the modulus of the discrete spectrum corresponding to each soliton pulse is adjusted to realize the shift of the soliton pulse in the time domain by the shift amount to achieve the required spacing. The nonlinear spectrum obtained after the aforementioned modulation is subjected to an inverse nonlinear Fourier transform to obtain the soliton pulse with adjustable spacing.

2. The soliton pulse spacing control method according to claim 1, characterized in that, The method for identifying the eigenvalues ​​corresponding to soliton pulses from the aforementioned eigenvalues ​​is as follows: The observed intensity corresponding to each soliton pulse is assigned to the formula I = 2Im(λ). k In ), I will be the calculated Im(λ) k ), which serves as an approximate eigenvalue λ for the soliton pulse. k The value of the imaginary part; Based on the multiple approximate eigenvalues ​​λ corresponding to the multiple soliton pulses k The imaginary part of the eigenvalue is used to remove the eigenvalues ​​corresponding to the sidebands from all eigenvalues, thus obtaining the eigenvalues ​​corresponding to the soliton pulse.

3. The soliton pulse spacing control method according to claim 1, characterized in that, The method for determining the discrete spectrum corresponding to each soliton pulse from the discrete spectrum set is as follows: The intensities of the multiple soliton pulses are sorted by magnitude, and this sorting is matched one-to-one with the sorting of the imaginary parts of the eigenvalues ​​in the eigenvalue set to determine the correspondence between soliton pulses and eigenvalues, thereby determining the correspondence between soliton pulses and discrete spectra, and obtaining the discrete spectrum corresponding to each soliton pulse.

4. The soliton pulse spacing control method according to claim 1, characterized in that, When adjusting the magnitude of the discrete spectrum corresponding to the soliton pulse k, the following formula is used: |Q′ d (l k )|=exp[ln(|Q d (l k )|)+2Im(λ k )Δt] In the formula, |Q′ d (λ k | represents the modified discrete spectrum Q′ corresponding to the current soliton pulse k. d (λ k The modulus of |Q; d (λ k | represents the discrete spectrum Q before modification corresponding to the current soliton pulse k. d (λ k The modulus of ); Im(λ) k ) represents the eigenvalue λ of the current soliton pulse k. k The imaginary part; Δt represents the amount of time-domain shift allocated to the current soliton pulse k.

5. The soliton pulse spacing control method according to claim 1, characterized in that, When assigning a time-domain shift amount to each of the two soliton pulses, the time-domain shift amount to one soliton pulse is 0, and the time-domain shift amount to the other soliton pulse is the deviation between the current spacing and the required spacing.

6. A computer program product, characterized in that, It includes a computer program that, when executed by a processor, implements the steps of the soliton pulse spacing control method as described in any one of claims 1 to 5.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein the computer program, when executed by a processor, controls the device containing the storage medium to perform the soliton pulse spacing control method as described in any one of claims 1 to 5.

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