A time-domain overlap-based single-dfb seed source laser generating device and method

Abstract

The application discloses a single DFB seed source laser generating device and method based on time domain overlap. The device comprises a DFB semiconductor seed source, a current driving module, an acousto-optic modulation shunt module, N optical fiber delay lines and a beam combiner. The current driving module outputs driving current to the DFB semiconductor seed source, and outputs driving current containing N pulses in a working period, so that the DFB semiconductor seed source sequentially outputs single-frequency lasers with multiple different center wavelengths. The acousto-optic modulation shunt module separates the lasers into N light beams. The lengths of the optical fiber delay lines are configured according to the time sequence difference of the laser output. The beam combiner outputs the multiple light beams after time delay adjustment, so that the single-frequency lasers with different center wavelengths at least partially overlap in the same time domain. The application only uses a single DFB seed source to realize equivalent multi-frequency spectrum expansion, disperses instantaneous optical energy, reduces the energy density of a single wavelength, and effectively improves the stimulated Brillouin scattering suppression threshold.

Description

Technical Field

[0001] This invention relates to the field of narrow linewidth pulsed fiber laser technology, specifically to a single DFB seed source laser generation device and method based on temporal overlap. Background Technology

[0002] Distributed feedback (DFB) semiconductor lasers are commonly used seed sources in fiber optic amplification systems. Their most prominent advantage lies in their extremely narrow spectral linewidth. Typical DFB lasers can achieve single-mode output, with linewidths typically reaching the MHz or even kHz range. Therefore, they have irreplaceable application value in scenarios requiring high spectral purity, such as coherent communication, precision measurement, and spectral analysis. However, the stimulated Brillouin scattering (SBS) effect, prevalent in fiber amplifiers, has become a key bottleneck limiting the power increase of DFB seed light. The SBS effect has a very narrow gain bandwidth, typically only about 20–60 MHz. This means that when a DFB laser with a linewidth in the kHz–MHz range is injected into a fiber amplifier, almost all of its spectral energy falls perfectly within the SBS gain bandwidth. Even with relatively low injected power, the SBS effect is easily triggered, preventing further output power amplification and, in severe cases, causing system instability.

[0003] To address the aforementioned issues, a common approach in existing technologies is to broaden the laser linewidth through phase modulation. Specifically, an electro-optic phase modulator is placed between the DFB seed source and the fiber amplifier. This modulator applies periodic or random phase modulation to the DFB seed light, artificially broadening the originally extremely narrow spectral linewidth, for example, from the kHz level to the GHz level. This broadened spectral width exceeds the gain bandwidth of the SBS (Strain Beam Filter), thereby increasing the SBS threshold and allowing for higher injection power. Depending on the modulation signal used, phase modulation schemes can be further categorized into various implementation methods, such as sinusoidal modulation, white noise modulation, and pseudo-random code modulation.

[0004] However, phase modulation for linewidth broadening has several inherent drawbacks. First, phase modulation fundamentally alters the phase characteristics of the laser, inevitably sacrificing the coherence of the DFB laser, which is an unacceptable trade-off for applications relying on high coherence. Second, the phase-modulated spectrum is prone to inducing new nonlinear effects such as random self-pulses during high-power amplification, thus reducing system stability and output beam quality. Furthermore, different phase modulation methods have limitations in terms of bandwidth broadening, spectral flatness, system cost, and control complexity, making it difficult to simultaneously meet multiple performance requirements.

[0005] Therefore, how to overcome the shortcomings of the existing technology is the subject of this invention. Summary of the Invention

[0006] The purpose of this invention is to provide a single DFB seed source laser generator and method based on temporal overlap to solve the above-mentioned technical problems.

[0007] To achieve the above objectives, the first aspect of this application provides a single DFB seed source laser generator based on temporal overlap, comprising:

[0008] DFB semiconductor seed source;

[0009] The current driving module is electrically connected to the DFB semiconductor seed source and is used to output driving current to the DFB semiconductor seed source. During a working period, the driving current contains N pulses, where N is an integer greater than or equal to 2. The driving current generates a changing current value within the pulse duration interval, so that the DFB semiconductor seed source outputs a time-series distributed single-frequency laser with multiple different center wavelengths during the working period.

[0010] The acousto-optic modulation splitter module is located on the output optical path of the DFB semiconductor seed source. It is used to receive single-frequency lasers with different center wavelengths generated in the time domain and to spatially separate the single-frequency lasers output at different times into N split beams.

[0011] N fiber delay lines are respectively set on the optical paths of N split beams. Each fiber delay line has a different fiber length, and the length of each fiber delay line is configured according to the output timing difference of each wavelength laser during the working period. It is used to apply transmission delay to each split beam and compensate for the timing difference between each split beam.

[0012] The beam combiner is connected to the output of N fiber delay lines to receive the time-delayed split beams and combine them for output, so that single-frequency lasers with different center wavelengths at least partially overlap in the same time domain.

[0013] In a further technical solution, the current driving module includes a waveform generation unit and a power amplification unit; the waveform generation unit is used to generate a voltage waveform, and the power amplification unit is used to convert the voltage waveform into a driving current and output it to the DFB semiconductor seed source.

[0014] In a further technical solution, within a working period, the N pulses are all linearly increasing ramp pulses, and the instantaneous current value of the i-th pulse satisfies: ;in Let be the current rise rate of the i-th pulse. The starting time of the i-th pulse is specified, and the peak current value of each pulse does not exceed three times the normal operating current of the DFB semiconductor seed source.

[0015] In a further technical solution, there is a pulse timing interval between adjacent discrete pulses of the drive current output. When the split beams are combined to achieve complete temporal overlap, the fiber corresponding to the first split beam to leave the acousto-optic modulation splitter module is used as the reference optical fiber. The formula for calculating the length of the delay line of the i-th fiber is as follows:

[0016]

[0017] in, The reference optical fiber length; The speed at which laser light travels in an optical fiber. c is the speed of light in a vacuum, and n is the refractive index of the optical fiber.

[0018] In a further technical solution, there is a pulse timing interval between adjacent discrete pulses of the drive current output. After beam combining, the time domains of the individual beams do not completely overlap and have a preset time difference misalignment. Using the fiber corresponding to the first beam to leave the acousto-optic modulation splitter module as the reference optical fiber, the first... Formula for calculating the length of a fiber optic delay line:

[0019]

[0020] in, For the reference optical fiber length, The speed at which laser light travels in an optical fiber. This is the preset time difference misalignment amount after adjacent pulses are combined.

[0021] In a further technical solution, the length of each fiber delay line is configured based on the actual measured time difference of each split beam leaving the acousto-optic modulation splitter module. When the split beams are combined to achieve complete time domain overlap, the split beam that leaves the acousto-optic modulation splitter module first is taken as the reference optical fiber. Then, the formula for calculating the length of the i-th fiber delay line is:

[0022] ;

[0023] in For the reference optical fiber length, , These represent the times when the i-th and reference optical beams leave the acousto-optic modulation splitter module, respectively. The speed at which laser light travels in an optical fiber.

[0024] In a further technical solution, when the time domains of the split beams after beam combining are not completely overlapping and have a preset time difference misalignment Δt; the formula for calculating the length of the i-th fiber delay line is:

[0025]

[0026] in For the reference optical fiber length, , The first The moment when the reference optical path beam leaves the acousto-optic modulation splitter module. This is the preset time difference misalignment between adjacent pulses. The speed at which laser light travels in an optical fiber.

[0027] In a further technical solution, the acousto-optic modulation splitter module includes an acousto-optic diffraction device; the acousto-optic diffraction device applies multiple different radio frequency signals to cause the incident laser to generate different diffraction angles, thereby realizing spatial beam splitting of single-frequency laser output at different times.

[0028] In a further technical solution, a collimator is provided between the acousto-optic modulation splitter module and each optical fiber delay line to couple the spatial split beam into each of the optical fiber delay lines.

[0029] According to a second aspect of this application, a single DFB seed source laser generation method based on temporal overlap is provided, comprising the following steps:

[0030] A driving current is output to the DFB semiconductor seed source; within a working period, the driving current contains N pulses, where N is an integer greater than or equal to 2; the driving current generates a changing current value within the pulse duration interval, so that the DFB semiconductor seed source outputs a time-series distributed single-frequency laser with multiple different center wavelengths within the working period;

[0031] By utilizing the acousto-optic diffraction effect, single-frequency lasers with different center wavelengths generated sequentially in the time domain are spatially separated into N beams.

[0032] Optical fiber delay lines are set on the optical paths of each beam splitter, and each optical fiber delay line has a different optical fiber length. The length of each optical fiber delay line is configured according to the output timing difference of each wavelength laser during the working period, which is used to apply differentiated transmission delay to each beam splitter and compensate for the timing difference between each beam splitter.

[0033] The N-way split beams, after time delay adjustment, are input into the beam combiner to complete the beam combination output, so that single-frequency lasers with different center wavelengths at least partially overlap in the same time domain.

[0034] The single DFB seed source laser generation device and method based on temporal overlap provided in this application have the following technical advantages:

[0035] This invention employs a single DFB semiconductor seed source, and through driving current regulation, enables the DFB to sequentially output single-frequency lasers with multiple different center wavelengths during its operating period. An acousto-optic modulation splitter module then spatially separates the sequential multi-wavelength lasers into multiple beams. Differential transmission delays are introduced via fiber delay lines of varying lengths to compensate for the inherent timing differences between the beams. Finally, at the combiner, the time domains of the different wavelength lasers achieve at least partial overlap. The entire device requires only one laser to achieve equivalent multi-frequency spectral expansion, dispersing instantaneous light energy into multiple wavelength components, effectively reducing single-wavelength energy density, significantly improving the stimulated Brillouin scattering suppression threshold, and greatly increasing the upper limit of the output power of the fiber amplification system while ensuring narrow-linewidth laser coherence.

[0036] Compared with traditional multi-DFB parallel beam combining schemes, this invention can achieve multi-wavelength time-domain superposition using only a single DFB seed source, eliminating the need for multiple independent lasers and matching driving circuits. This simplifies the system structure, significantly reduces hardware costs, and makes the system more compact. Furthermore, it eliminates the spectral overlap failure problem caused by inconsistent wavelength temperature drift among multiple lasers, resulting in superior long-term system stability. The driving current can be flexibly configured with different pulse patterns, allowing dynamic adjustment of the spectral broadening width and pulse envelope shape according to actual SBS suppression requirements, thus adapting to various application scenarios with different power levels and linewidth requirements. Attached Figure Description

[0037] Figure 1 This is a system structure diagram of Embodiment 1 of the present invention;

[0038] Figure 2 This is a schematic diagram of the driving current waveform (flat top) according to Embodiment 1 of the present invention.

[0039] Figure 3 This is a waveform diagram of the original DFB output timing pulses in Embodiment 1 of the present invention;

[0040] Figure 4 This is a schematic diagram of the time-domain superposition (complete superposition) after fiber delay bundling in Embodiment 1 of the present invention.

[0041] Figure 5 This is a pulse frequency distribution diagram after beam combining according to Embodiment 1 of the present invention;

[0042] Figure 6 This is a waveform diagram of the original DFB output timing pulses in Embodiment 1 of the present invention (not completely superimposed, staggered by Δt).

[0043] Figure 7 This is a schematic diagram of the time-domain superposition of fiber delay bundles in Embodiment 1 of the present invention (incomplete superposition).

[0044] Figure 8 This is a schematic diagram of the driving current waveform in Embodiment 2 of the present invention (the top is tilted, the slope is the same, and the peak values ​​are different).

[0045] Figure 9 This is a waveform diagram of the original DFB output timing pulse in Embodiment 2 of the present invention;

[0046] Figure 10 This is a schematic diagram of the time-domain superposition (complete superposition) after fiber delay bundling in Embodiment 2 of the present invention.

[0047] Figure 11 This is a graph showing the pulse frequency distribution and variation trend after beam combining in Embodiment 2 of the present invention.

[0048] Figure 12 This is a schematic diagram of the driving current waveform in Embodiment 3 of the present invention (linearly inclined with different slopes).

[0049] Figure 13 This is a waveform diagram of the original DFB output timing pulse in Embodiment 3 of the present invention;

[0050] Figure 14 This is a schematic diagram of the time-domain superposition (complete superposition) after fiber delay bundling in Embodiment 3 of the present invention.

[0051] Figure 15 This is a graph showing the pulse frequency distribution and variation trend after the three beams are combined according to an embodiment of the present invention.

[0052] Figure 16 This is a flowchart of an embodiment of the method of the present invention;

[0053] In the above attached diagram: 1-DFB semiconductor seed source; 2-current drive module; 3-acoustic-optic modulation splitter module; 4-fiber delay line; 5-combiner; 6-collimator. Detailed Implementation

[0054] 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 a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0055] The terms "first," "second," etc., used in this article do not specifically refer to order or sequence, nor are they intended to limit this case; they are merely used to distinguish components or operations described using the same technical terms.

[0056] The terms "connection" or "positioning" as used in this article can refer to two or more components or devices making direct physical contact with each other, or making indirect physical contact with each other, or to two or more components or devices operating or moving with each other.

[0057] The terms “include,” “including,” and “have” used in this article are all open-ended, meaning they include but are not limited to.

[0058] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of the art, the subject matter, and the specific context. Certain terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing the case.

[0059] The terms “front,” “back,” “up,” “down,” “left,” and “right” used in this article are directional terms. In this case, they are only used to describe the positional relationship between the structures and are not intended to limit the specific direction of the protection scheme or its actual implementation.

[0060] The technical principles of this solution are explained below:

[0061] The output wavelength of a DFB semiconductor laser is determined by the equivalent refractive index of its active region, which changes with the injected carrier concentration. When a pulsed driving current is injected into a DFB laser, the dynamic change of the current over time causes a continuous change in the carrier concentration, resulting in a momentary drift in the output wavelength, a phenomenon known as frequency chirp.

[0062] Specifically, during the rising edge of the pulse current, the injected current continues to increase, the carrier concentration continues to rise, the refractive index of the active region decreases accordingly, and the output wavelength drifts towards shorter wavelengths. The faster the current rise rate, the greater the change in carrier concentration per unit time, and the faster the wavelength drifts over time.

[0063] Therefore, for pulses with different current rise rates, even if the starting current and peak current are the same, the instantaneous current values ​​at the same moment will differ, resulting in different instantaneous output wavelengths. Utilizing this characteristic, multiple laser components with different instantaneous wavelengths can be obtained within the same time window by configuring current pulses with different rise rates.

[0064] Theoretically, DFB semiconductor seed sources produce single-mode output. When the injection current increases, the number of electron-hole pairs in the active region increases, the carrier concentration rises, and the equivalent refractive index n changes. At the same time, according to the longitudinal mode frequency condition Δν=c / (2nL), the change in the equivalent refractive index will cause a change in the optical cavity length (2nL), ultimately leading to a shift in the laser center wavelength.

[0065] Different injected currents result in different electron-hole pair densities corresponding to different equivalent refractive index (n) values, leading to differences in the optical cavity length and a shift in the center wavelength with instantaneous changes in the current. As the current rate increases, the number of charge carriers increases, the refractive index increases, and the center wavelength redshifts, becoming longer. Conversely, as the current rate decreases, the center wavelength blueshifts, becoming shorter.

[0066] Based on the above principle, by rapidly changing the driving current to modulate the output wavelength of the DFB, the single-frequency wavelength can be changed at different instants, thereby effectively broadening the output spectrum of the DFB semiconductor laser in the time domain and outputting spectral components of different wavelengths at different times.

[0067] By utilizing this time-domain spectral broadening characteristic, different spectral components at different times can be used to equalize the pulse energy density in the subsequent fiber amplifier, so that the total optical energy is distributed across multiple frequency components, thereby effectively suppressing the stimulated Brillouin scattering (SBS) effect and ultimately achieving higher single-pulse energy output.

[0068] like Figure 1 As shown, this embodiment provides a single DFB seed source laser generator based on temporal overlap, including a DFB semiconductor seed source 1, a current driving module 2, an acousto-optic modulation splitter module 3, N fiber delay lines 4, and a beam combiner 5. In this embodiment, N=4, that is, a four-pulse driving and four-optical-path splitting architecture is adopted within one working period.

[0069] In this embodiment, the DFB semiconductor seed source 1 is a 1064nm band distributed feedback semiconductor laser with a center wavelength of 1064.000nm at 40mA, a threshold current of 15mA, a rated operating current of 100mA, a wavelength tuning coefficient of approximately 0.005nm / mA, and a single longitudinal mode linewidth of less than 10MHz.

[0070] The current drive module 2 is electrically connected to the DFB semiconductor seed source 1 and includes a waveform generation unit and a power amplification unit. The waveform generation unit uses a high-speed arbitrary waveform generator to generate a voltage signal with a preset waveform; the power amplification unit uses a high-speed current driver to convert the voltage signal into a corresponding drive current and output it to the DFB semiconductor seed source 1.

[0071] like Figure 2 As shown, in this embodiment, the driving current is a flat-top pulse waveform, consisting of four sequentially output discrete pulses. Each pulse has a pulse width of 4ns, and the timing interval t between adjacent pulses is 6ns. The peak current values ​​of the four pulses are 40mA, 60mA, 80mA, and 100mA, respectively, increasing sequentially. Both the rising and falling edges of the pulses are rapid transitions of 0.2ns, and the current remains constant during the flat-top phase.

[0072] Since the output wavelength of the DFB semiconductor seed source 1 is determined by the instantaneous injection current, flat-top pulses with different peak values ​​correspond to different fixed center wavelengths. 40mA corresponds to a wavelength of approximately 1064nm, 60mA to approximately 1064.1nm, 80mA to approximately 1064.2nm, and 100mA to approximately 1064.3nm. The four pulses are output sequentially, forming four sets of non-overlapping fixed wavelength sequences in the time domain.

[0073] The acousto-optic modulation splitter module 3 is located on the output optical path of the DFB semiconductor seed source 1. It employs an acousto-optic diffractometer to achieve beam splitting by applying four different radio frequency (RF) signals. The frequencies of the four RF signals are 40MHz, 60MHz, 80MHz, and 100MHz, respectively. The RF signals of different frequencies excite the acousto-optic crystal to generate ultrasonic gratings with different spatial periods. The diffraction angle of the incident laser, which satisfies the Bragg diffraction condition, varies with the RF frequency, thereby diffracting the four sequentially output lasers of different wavelengths into four different spatial transmission channels, achieving spatial beam splitting.

[0074] Furthermore, a collimator 6 is provided between the acousto-optic modulation splitter module 3 and each optical fiber delay line 4 to efficiently couple the spatial split beam into each optical fiber delay line 4, thereby reducing optical path coupling loss.

[0075] Four fiber delay lines 4 are respectively installed on the optical paths of the four split beams, and each fiber delay line 4 has a different fiber length. The length of each fiber delay line 4 is configured according to the output timing difference of each wavelength of laser during the working period, and is used to apply differentiated transmission delay to each split beam to compensate for the timing difference between each split beam.

[0076] In this embodiment, a standard single-mode silica fiber is used, with a refractive index n of approximately 1.5. The laser propagation speed in the fiber is v0 = c / n ≈ 2 × 10⁻⁶. 8 m / s, corresponding to a transmission delay of approximately 5ns / m per unit length.

[0077] When the split beams are combined to achieve complete temporal overlap, the fiber corresponding to the beam that first leaves the acousto-optic modulation splitter module 3 is used as the reference optical fiber, and the length of the reference optical fiber is... Let's assume the length is 20m. The formula for calculating the length of the i-th fiber delay line is:

[0078]

[0079] Substituting t=6ns and v0=2×10 8 m / s, the length difference between adjacent optical fibers can be obtained as ΔL = 6ns × 2 × 10 8 m / s = 1.2m.

[0080] Therefore, the lengths of the four fiber delay lines are as follows:

[0081] Route 1 (Reference Route): L1 = 20m;

[0082] Route 2: L2 = 20m - 1.2m = 18.8m;

[0083] Route 3: L3 = 20m - 2.4m = 17.6m;

[0084] Route 4: L4 = 20m - 3.6m = 16.4m;

[0085] With the above configuration, the first generated wavelength beam passes through a longer fiber delay line, resulting in a greater transmission delay; the second generated wavelength beam passes through a shorter fiber delay line, resulting in a smaller transmission delay. After the four beams pass through fiber delay lines of different lengths, the timing difference is completely compensated, and finally, complete temporal overlap is achieved at the combiner 5.

[0086] The combiner 5 is connected to the output of the four fiber delay lines 4 respectively. A 4×1 fiber combiner is used to receive the split beams after time delay adjustment and combine them for output.

[0087] like Figure 3 The diagram shows the original pulse output from the DFB semiconductor seed source 1. Four flat-top pulses are output sequentially in the time domain, spaced 6 ns apart, with each pulse corresponding to a fixed center wavelength.

[0088] like Figure 4 The diagram shows the output pulse after delay compensation by the fiber delay line and combining by combiner 5. The four pulses are perfectly aligned and overlapped in the time domain, forming a pulse envelope with a width of approximately 4 ns.

[0089] like Figure 5 The image shows the frequency distribution of the combined pulse. At this instant, four discrete single-frequency components exist simultaneously, corresponding to wavelengths of 1064.000 nm, 1064.100 nm, 1064.200 nm, and 1064.300 nm, respectively. The combined pulse contains multiple components of different wavelengths throughout its duration, dispersing the instantaneous optical energy across four wavelength channels. The single-wavelength energy density is reduced to one-quarter of its original value, effectively suppressing the stimulated Brillouin scattering effect during subsequent fiber amplification.

[0090] Furthermore, such as Figure 6 , Figure 7 As shown, this embodiment can also be configured for a non-complete overlap condition. After beam combining, the time domains of the individual beams do not completely overlap, and there is a preset time difference misalignment Δt between adjacent pulses. In this embodiment, Δt is set to 0.5 ns.

[0091] At this point, the length of each fiber delay line is determined jointly by the pulse timing interval t and the time difference misalignment Δt due to incomplete overlap. .

[0092] Substituting t=6ns, Δt=0.5ns, and v0=2×10 8 Given m / s, the lengths of the four fiber delay lines under the incomplete overlap condition are:

[0093] Route 1 (Reference Route): L1 = 20m;

[0094] Route 2: L2 = 20m - 1.1m = 18.9m;

[0095] Route 3: L3 = 20m - 2.2m = 17.8m;

[0096] Route 4: L4 = 20m - 3.3m = 16.7m;

[0097] By configuring the length of the fiber delay line, the four pulses overlap only partially in the time domain. Although the number of wavelengths coexisting at the same time is slightly reduced, the spectral coverage time within the entire pulse cycle is lengthened and the single-frequency energy accumulation time is shortened, which can still achieve a good SBS suppression effect. At the same time, the total width of the output pulse can be flexibly adjusted.

[0098] It is important to note that the time difference misalignment Δt should not be too large. If Δt is too large, the temporal overlap region between adjacent pulses will be too small, significantly reducing the number of wavelengths coexisting at the same time, which will weaken the SBS suppression effect brought about by multi-wavelength spectral expansion. Generally, Δt should not exceed half of the pulse timing interval t, preferably not exceeding one-third of t, to ensure sufficient temporal overlap between each pulse, maintain the spectral expansion effect of multiple wavelength components coexisting simultaneously, and balance the flexibility of pulse width adjustment with SBS suppression capability.

[0099] Example 2: The difference between this example and Example 1 lies in the waveform configuration of the driving current. For example... Figure 8 As shown, in this embodiment, the driving current is a top-tilted trapezoidal pulse current. The four pulses have the same rising slope, but different peak currents.

[0100] Specifically, the pulse width of each of the four pulses is 4 ns, and the timing interval t between adjacent pulses is 6 ns. The base current of each pulse is 40 mA, and the current rise slope k is 15 mA / ns. Therefore, the peak currents of the four pulses are as follows:

[0101] The first pulse: 40mA + 15mA / ns × 4ns = 100mA; the second to fourth pulses are 115mA, 130mA, and 145mA respectively.

[0102] As the internal current of each pulse continuously rises, the DFB output wavelength changes continuously with the instantaneous current, with the wavelength continuously red-shifting within the rising edge interval of a single pulse. The wavelength scanning ranges of the four pulses are different, and the higher the peak current, the larger the wavelength scanning range.

[0103] like Figure 9 The diagram shows the original pulse output from the DFB semiconductor seed source 1. Four pulses are output sequentially in the time domain, and the light intensity of each pulse increases synchronously with the current.

[0104] like Figure 10 The diagram shows the output pulse after delay compensation by the fiber delay line and combining by combiner 5. The rising edges of the four pulses are perfectly aligned and overlapped in the time domain, forming a pulse envelope with a width of approximately 4 ns.

[0105] like Figure 11 The figure shows the frequency distribution and trend of the combined pulse. At this instant, four different single-frequency components exist simultaneously; and as time progresses, the four frequency components move synchronously towards longer wavelengths, forming a dynamic frequency sweep effect. Compared to the fixed discrete wavelength of the flat-top pulse, the ramp pulse scheme has more spectral components, more uniform energy distribution, and better SBS suppression effect.

[0106] The remaining structure and working principle of this embodiment are the same as those of Embodiment 1, and will not be repeated here.

[0107] Example 3: The difference between this example and Examples 1 and 2 lies in the configuration of the driving current. For example... Figure 12 As shown, in this embodiment, the driving current is a linear inclined ramp pulse, and the current rise rate of the four pulses is different from each other.

[0108] Specifically, the pulse width of each of the four pulses is 4 ns, and the timing interval t between adjacent pulses is 6 ns. The base current of each pulse is 0 mA, and the current rise rates of the four pulses are as follows:

[0109] k1 = 15 mA / ns;

[0110] k2 = 20 mA / ns;

[0111] k3 = 25 mA / ns;

[0112] k4 = 30 mA / ns;

[0113] The corresponding peak pulse currents are approximately 60 mA, 80 mA, 100 mA, and 120 mA, respectively.

[0114] The slower the rise rate, the smaller the change in injected current per unit time, and the smaller the instantaneous wavelength drift of the DFB laser; the faster the rise rate, the larger the wavelength drift per unit time. When the rising edges of four pulses overlap in the time domain, due to the difference in wavelength drift rates of each pulse, the instantaneous wavelengths corresponding to the four beams at the same moment are different, realizing the time-domain superposition of multiple wavelength components and broadening the instantaneous spectral range.

[0115] like Figure 13 The diagram shows the original pulse output from the DFB semiconductor seed source 1. Four pulses are output sequentially in the time domain, and the light intensity of each pulse changes synchronously with the current, forming an asymmetric triangular waveform with different slopes.

[0116] like Figure 14 The diagram shows the output pulse after delay compensation by the fiber delay line and combining by combiner 5. The rising edges of the four pulses are perfectly aligned and overlapped in the time domain, forming a pulse envelope with a width of approximately 4 ns.

[0117] like Figure 15 The diagram shows the frequency distribution and trend of the combined pulse. At this instant, four different single-frequency components exist simultaneously; and as time progresses, the four frequency components shift towards longer wavelengths, creating a dynamic frequency sweep effect. The dashed box represents the complete frequency sweep interval of the pulse, and the arrows represent the instantaneous frequency change as the pulse progresses. Pulses corresponding to currents with different peak values ​​and slopes have different frequency sweep bandwidths; the larger the peak current, the wider the frequency sweep bandwidth of the pulse.

[0118] In this embodiment, after the four ramp pulses with different slopes are superimposed, the instantaneous wavelength continuously changes dynamically throughout the entire pulse duration, accumulating to form a wider continuous spectrum. The energy is distributed across continuous frequency points, and the instantaneous energy density of any single frequency point is extremely low. The SBS suppression effect is significantly better than that of the flat-top pulse scheme.

[0119] The remaining structure and working principle of this embodiment are the same as those of Embodiment 1, and will not be repeated here.

[0120] like Figure 16 As shown, this embodiment provides a single DFB seed source laser generation method based on temporal overlap, including the following steps:

[0121] S1. Output driving current to the DFB semiconductor seed source; within a working period, the driving current contains N pulses, where N is an integer greater than or equal to 2; the driving current generates a changing current value within the pulse duration interval, causing the DFB semiconductor seed source to output a time-series distributed single-frequency laser with multiple different instantaneous center wavelengths within the working period.

[0122] S2. Utilizing the acousto-optic diffraction effect, single-frequency lasers with different center wavelengths generated sequentially in the time domain are spatially separated into N beams.

[0123] S3. Fiber delay lines are set on the optical paths of each beam splitter, and each fiber delay line has a different fiber length. The length of each fiber delay line is configured according to the output timing difference of each wavelength laser during the working period, which is used to apply differentiated transmission delay to each beam splitter and compensate for the timing difference between each beam splitter.

[0124] S4. Input the N-way split beams, which have undergone time delay adjustment, into the beam combiner to complete the beam combining output, so that single-frequency lasers with different center wavelengths at least partially overlap in the same time domain.

[0125] The working principle of the above method is consistent with that of the device embodiment, and will not be described in detail here.

[0126] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A single DFB seed source laser generator based on temporal overlap, characterized in that, include: DFB semiconductor seed source; The current driving module is electrically connected to the DFB semiconductor seed source and is used to output driving current to the DFB semiconductor seed source. During a working period, the driving current contains N pulses, where N is an integer greater than or equal to 2. The driving current generates a changing current value within the pulse duration interval, so that the DFB semiconductor seed source outputs a time-series distributed single-frequency laser with multiple different center wavelengths during the working period. The acousto-optic modulation splitter module is located on the output optical path of the DFB semiconductor seed source. It is used to receive single-frequency lasers with different center wavelengths generated in the time domain and to spatially separate the single-frequency lasers output at different times into N split beams. N fiber delay lines are respectively set on the optical paths of N split beams. Each fiber delay line has a different fiber length, and the length of each fiber delay line is configured according to the output timing difference of each wavelength laser during the working period. It is used to apply transmission delay to each split beam and compensate for the timing difference between each split beam. The beam combiner is connected to the output of N fiber delay lines to receive the time-delayed split beams and combine them for output, so that single-frequency lasers with different center wavelengths at least partially overlap in the same time domain.

2. The single DFB seed source laser generator based on temporal overlap according to claim 1, characterized in that, The current drive module includes a waveform generation unit and a power amplification unit; the waveform generation unit is used to generate a voltage waveform, and the power amplification unit is used to convert the voltage waveform into a drive current and output it to the DFB semiconductor seed source.

3. The single DFB seed source laser generator based on temporal overlap according to claim 1, characterized in that, During a working period, all N pulses are linearly increasing ramp pulses, and the instantaneous current value of the i-th pulse satisfies: ;in Let be the current rise rate of the i-th pulse. The starting time of the i-th pulse is specified, and the peak current value of each pulse does not exceed three times the normal operating current of the DFB semiconductor seed source.

4. The single DFB seed source laser generator based on temporal overlap according to claim 1, characterized in that, The adjacent discrete pulses of the drive current output have a pulse timing interval. When the split beams are combined to achieve complete temporal overlap, the fiber corresponding to the first split beam to leave the acousto-optic modulation splitter module is used as the reference optical fiber. The formula for calculating the length of the delay line of the i-th fiber is as follows: ； in, The reference optical fiber length; The speed at which laser light travels in an optical fiber. c is the speed of light in a vacuum, and n is the refractive index of the optical fiber.

5. The single DFB seed source laser generator based on temporal overlap according to claim 1, characterized in that, The adjacent discrete pulses of the drive current output have a pulse timing interval. After beam combining, the time domains of the individual beams do not completely overlap and have a preset time difference misalignment. Using the fiber corresponding to the first beam to leave the acousto-optic modulation splitter module as the reference optical fiber, the first... The formula for calculating the length of the optical fiber delay line is: ； in, For the reference optical fiber length, The speed at which laser light travels in an optical fiber. This is the preset time difference misalignment amount after adjacent pulses are combined.

6. The single DFB seed source laser generator based on temporal overlap according to claim 1, characterized in that, The length of each fiber delay line is configured based on the actual measured time difference of each split beam leaving the acousto-optic modulation splitter module. When the split beams are combined to achieve complete time domain overlap, the split beam that leaves the acousto-optic modulation splitter module first is taken as the reference optical fiber. The formula for calculating the length of the i-th fiber delay line is: ； in For the reference optical fiber length, , These represent the times when the i-th and reference optical beams leave the acousto-optic modulation splitter module, respectively. The speed at which laser light travels in an optical fiber.

7. The single DFB seed source laser generator based on temporal overlap according to claim 1, characterized in that, When the time domains of the individual beams after beam combining are not completely overlapped and have a preset time difference misalignment Δt; the formula for calculating the length of the i-th fiber delay line is: ； in For the reference optical fiber length, , The first The moment when the light beam from the reference optical path leaves the acousto-optic modulation splitter module. This is the preset time difference misalignment between adjacent pulses. The speed at which laser light travels in an optical fiber.

8. The single DFB seed source laser generator based on temporal overlap according to claim 1, characterized in that, The acousto-optic modulation splitter module includes an acousto-optic diffraction device; the acousto-optic diffraction device applies multiple different radio frequency signals to cause the incident laser to generate different diffraction angles, thereby realizing spatial splitting of single-frequency laser output at different times.

9. The single DFB seed source laser generator based on temporal overlap according to claim 1, characterized in that, A collimator is provided between the acousto-optic modulation splitter module and each fiber delay line to couple the spatial split beam into each fiber delay line.

10. A single DFB seed source laser generation method based on temporal domain overlap, characterized in that, Includes the following steps: A driving current is output to the DFB semiconductor seed source; within a working period, the driving current contains N pulses, where N is an integer greater than or equal to 2; the driving current generates a changing current value within the pulse duration interval, so that the DFB semiconductor seed source outputs a time-series distributed single-frequency laser with multiple different center wavelengths within the working period; By utilizing the acousto-optic diffraction effect, single-frequency lasers with different center wavelengths generated sequentially in the time domain are spatially separated into N beams. Optical fiber delay lines are set on the optical paths of each beam splitter, and each optical fiber delay line has a different optical fiber length. The length of each optical fiber delay line is configured according to the output timing difference of each wavelength laser during the working period, which is used to apply differentiated transmission delay to each beam splitter and compensate for the timing difference between each beam splitter. The N-way split beams, after time delay adjustment, are input into the beam combiner to complete the beam combining output, so that single-frequency lasers with different center wavelengths at least partially overlap in the same time domain.

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