A chirp signal generating apparatus and method

Abstract

The application discloses a kind of linear frequency modulation signal generating device and method, including integrated mutual injection laser for generating single periodic state optical signal, optical signal is divided into two beams by optical fiber splitter, one of which sequentially passes through short delay unit, first photoelectric detector and then enters first electric coupler, the other sequentially passes through long delay unit, second photoelectric detector and then enters first electric coupler, the electric signal synthesized by the first electric coupler is amplified by the radio frequency power amplifier and then input into the electric splitter and divided into two ways, one of which outputs linear frequency modulation signal, the other is coupled with driving signal input into the second electric coupler and then directly modulated onto integrated mutual injection laser.The application can generate linear frequency modulation signal with high stability, high purity and large time-bandwidth product, and the structure of the device is exquisite, easy to integrate and low in cost.

Description

Technical Field

[0001] This invention relates to the field of microwave optoelectronics technology, specifically to a linear frequency modulated signal generation device and method. Background Technology

[0002] Frequency Modulated Continuous Wave (FMCW) radar is one of the most widely used radar technologies, favored for its ease of waveform generation, efficient spectrum utilization, and low interception probability. As a type of FMCW, linear frequency modulated (LFM) signals are easier to generate and process, and are frequently used in radar systems. Traditional methods for generating LFM signals mainly rely on electronic devices, including voltage-controlled oscillators and direct digital synthesizers. However, due to limitations in current analog-to-digital conversion rates, the generated LFM signals often have low center frequencies, narrow bandwidths, and low spectral purity, failing to meet the current radar requirements for high-precision, high-resolution signals.

[0003] As radar systems develop towards higher resolution and higher frequency bands, microwave photonics (MWP) technology has been introduced into the generation of FMCW radar signals. Pulse compression radar can resolve the contradiction between the maximum effective range and resolution of radar. Among them, Zhuang, J., Li, X., Li, S., & Chan, S. (2016). Frequency-modulated microwave generation with feedback stabilization using an optically injected semiconductor laser. Optics Letters, 41 24, 5764-5767.) proposed a frequency-modulated microwave signal generation system with stable feedback based on an optically injected semiconductor laser. This system can generate signals with high stability and large bandwidth. To improve the spectral purity of the generated signal, a photoelectric feedback loop is also introduced into the system. However, this system is an optical injection system based on a discrete laser, which requires the use of a high-speed external modulator and a polarization state controller. The photoelectric effect of the high-speed external modulator MZM is relatively weak, requiring high-power current drive, resulting in high power consumption and increasing the cost of signal generation. The polarization state controller increases the polarization sensitivity of the system, making it susceptible to external jitter and limiting its application scenarios. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a linear frequency modulation signal generation device and method. The device has a compact structure, is easy to integrate, has low cost, and can generate a linear frequency modulation signal with high stability, high purity, and a large time-bandwidth product.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] In a first aspect, the present invention provides a linear frequency modulated signal generating device, comprising an integrated mutual injection laser, an optical fiber splitter, a short delay unit, a long delay unit, a first photodetector, a second photodetector, a first electrical coupler, an RF power amplifier, an electrical splitter, and a second electrical coupler;

[0007] The integrated cross-injection laser is used to generate a single-cycle optical signal from the input signal. The optical signal is split into two beams by an optical fiber splitter. One beam passes through the short delay unit and the first photodetector in sequence before entering the first electrical coupler. The other beam passes through the long delay unit and the second photodetector in sequence before entering the first electrical coupler. The electrical signal synthesized by the first electrical coupler is amplified by the radio frequency power amplifier and then input into the electrical splitter to be split into two paths. One path outputs a linear frequency modulated signal, and the other path is coupled with the drive signal and input into the second electrical coupler and directly modulated onto the integrated cross-injection laser.

[0008] In conjunction with the first aspect, optionally, the integrated mutual injection laser includes a front laser, a rear laser, and a phase region sharing the same ridge waveguide structure. The phase region is located between the front laser and the rear laser. Both the front laser and the rear laser are provided with electrical isolators between themselves and the phase region. The front laser and the rear laser are in a mutual injection state.

[0009] In conjunction with the first aspect, optionally, an optical isolator is provided at the output port of the integrated mutual injection laser.

[0010] In conjunction with the first aspect, optionally, the integrated mutual injection laser is connected to an optical fiber splitter via an optical fiber patch cord.

[0011] In conjunction with the first aspect, optionally, the short delay unit includes a short single-mode fiber and a first optical attenuator, the short single-mode fiber being connected to the first optical attenuator; the long delay unit includes a long single-mode fiber and a second optical attenuator, the long single-mode fiber being connected to the second optical attenuator.

[0012] In conjunction with the first aspect, optionally, the length of the long single-mode fiber is an integer multiple of the length of the short single-mode fiber.

[0013] In conjunction with the first aspect, optionally, the ratio of optical power output from the two ports of the optical fiber splitter is 1:1.

[0014] In conjunction with the first aspect, optionally, the power output ratio of the two ports of the electrical splitter is 1:9; wherein, the electrical signal with a ratio of 1 is used as the output linear frequency modulated signal, and the other electrical signal with a ratio of 9 is coupled with the drive signal input to the second electrical coupler and then directly modulated onto the integrated mutual injection laser.

[0015] In a second aspect, the present invention provides a method for generating a linear frequency modulated signal, wherein a linear frequency modulated signal is generated using a linear frequency modulated signal generating device as described in any of the first aspects.

[0016] In conjunction with the second aspect, optionally, the step of generating a linear frequency modulated electrical signal includes:

[0017] A bias current is applied to the integrated mutual injection laser to make the integrated mutual injection laser operate in a single-cycle state to generate a single-cycle optical signal.

[0018] The optical signal is input to the optical fiber splitter via an optical fiber patch cord and split into two identical beams. One beam, after passing through a short delay unit and a first photodetector, generates an electrical signal, which, along with the other beam, after passing through a long delay unit and a second photodetector, generates an electrical signal. These signals are then coupled to a first electrical coupler and amplified by a power amplifier.

[0019] The amplified electrical signal is input to an electrical splitter and split into two paths. One path, accounting for 10% of the signal, is used as the output linear frequency modulated signal, while the other path, accounting for 90%, is coupled to the drive signal input to the second electrical coupler and then directly modulated onto the integrated mutual injection laser.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0021] 1. This invention utilizes an integrated inter-injection laser that can not only serve as a seed light source, but also replaces the microwave photonic filter and high-speed external modulator of the traditional discrete optical injection system. This avoids the need for additional use of ultra-narrowband optical filters and external modulators, simplifies the structure of the device, reduces its size, lowers the cost, and enhances the stability of the generated signal.

[0022] 2. This invention splits the optical signal into two beams via an optical fiber splitter. One beam passes sequentially through the short-delay unit and the first photodetector before entering the first electrical coupler. The other beam passes sequentially through the long-delay unit and the second photodetector before entering the first electrical coupler, forming a dual-feedback loop structure. The short-delay unit establishes the dominant feedback mode, achieving Fourier mode-locking. Its mode frequency interval is the same as the single-cycle switching frequency, thus optimizing the oscillation frequency of each single cycle of the optical signal. The long-delay unit provides an auxiliary feedback mode, which, through self-injection locking, improves the spectral purity of the dominant feedback mode.

[0023] 3. The method of the present invention can achieve individual control of the front laser / laser on the integrated mutual injection laser by controlling the bias current, and simultaneously change their output light intensity and wavelength, which can realize linear frequency modulation signal with a bandwidth of hundreds of GHz, greatly increasing the detection accuracy of radar; and the feedback microwave signal can be loaded not only on the back laser, but also on the front laser. Compared with the traditional single injection method of separate master and slave lasers, its modulation path is more flexible.

[0024] 4. This invention utilizes an integrated mutual injection laser combined with a dual feedback loop structure to generate a linear frequency modulated signal with high stability, high purity, and a large time-bandwidth product. The generated linear frequency modulated signal also has good pulse compression characteristics. Furthermore, the device of this invention has a compact structure, is easy to integrate, and is convenient to use, making it suitable for widespread application. Attached Figure Description

[0025] Figure 1 This is a structural principle block diagram of a linear frequency modulation signal generation device provided in an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the specific structure of a linear frequency modulation signal generation device provided in an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of the spectrum generated by the two loops when the linear frequency modulation signal generating device provided in the embodiment of the present invention starts oscillating without a driving signal;

[0028] Figure 4 The time-frequency diagram is obtained by performing a short-time Fourier transform on the time-series waveform of the linear frequency modulation signal generated by the device provided in the embodiment of the present invention.

[0029] Figure 5 Spectral detail diagram and time-domain waveform diagram of the linear frequency modulated signal generated by the device provided in the embodiments of the present invention;

[0030] Figure 6 The autocorrelation curve of the 8GHz linear frequency modulated signal generated by the device provided in the embodiment of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0032] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] This invention provides a linear frequency modulated signal generation device that utilizes microwave photonics technology and the nonlinear effect in an integrated cross-injection laser to introduce a photoelectric feedback loop, thereby achieving the generation of a high-purity, high-bandwidth linear frequency modulated signal.

[0035] Reference Figure 1 As shown, the linear frequency modulated signal generating device provided in this embodiment includes: an integrated mutual injection laser, an optical fiber splitter, a short delay unit, a long delay unit, a first photodetector, a second photodetector, a first electrical coupler, an RF power amplifier, an electrical splitter, and a second electrical coupler. The integrated mutual injection laser is used to generate a single-cycle optical signal from the input signal. The optical signal is input to the optical fiber splitter through an optical fiber patch cord and split into two beams. One beam passes through the short delay unit and the first photodetector in sequence and then enters the first electrical coupler. The other beam passes through the long delay unit and the second photodetector in sequence and then enters the first electrical coupler. The electrical signal synthesized by the first electrical coupler is amplified by the RF power amplifier and then input to the electrical splitter to be split into two paths. One path outputs a linear frequency modulated signal, and the other path is coupled with the driving signal and input to the second electrical coupler and directly modulated onto the integrated mutual injection laser.

[0036] Specifically, such as Figure 2As shown, the integrated mutual-injection laser includes a front laser, a rear laser, and a phase region sharing the same ridge waveguide structure. The phase region is located between the front and rear lasers. Electrical isolators are installed between the front and rear lasers and the phase region, and the front and rear lasers are in a mutual-injection state. Furthermore, an optical isolator is installed at the output port of the integrated mutual-injection laser to prevent external light injection or reflected light signals from damaging the laser.

[0037] Furthermore, the integrated inter-injection laser provided in this embodiment does not require an additional polarization controller due to the very small length of its phase region. The integrated inter-injection laser operates in a single-cycle state, and the wavelength interval between the two lasers is the single-cycle oscillation frequency, which has a large tuning range of 0.1-0.8 nm. In the single-cycle state, due to the photon-photon resonance effect, amplification of specific frequency microwave signals can be generated at the optical longitudinal mode, increasing the direct modulation bandwidth and modulation response. Therefore, the integrated inter-injection laser provided in this embodiment inherently possesses filtering functionality. Furthermore, this embodiment uses a waveform generator to generate a low-repetition-rate sawtooth wave as a driving signal to directly modulate the integrated inter-injection laser, causing the detuning frequencies of the two laser wavelengths to change approximately linearly within one pulse cycle in the single-cycle state, thereby generating a linearly modulated signal after the photodetector beats.

[0038] It should be noted that the integrated cross-injection laser provided in this embodiment is used to generate a single-period light source as a seed light source, and utilizes the photon-photon resonance effect to achieve selective amplification of the oscillator feedback mode;

[0039] An optical fiber splitter is used to split an optical signal into two paths; in this embodiment, the optical power ratio of the two ports of the optical fiber splitter is 1:1, and the optical power of the two output ports is the same.

[0040] The short delay unit is used to establish the dominant feedback mode and achieve Fourier mode locking. Its frequency interval is the same as the single-cycle switching frequency, thereby optimizing the oscillation frequency of each single cycle.

[0041] The long delay unit is used to provide an auxiliary feedback mode, which improves the spectral purity of the dominant feedback mode through self-injection locking;

[0042] The first photodetector and the second photodetector are both used for photoelectric conversion, converting the linear frequency modulated optical carrier signal into a linear frequency modulated electrical signal output; the first electrical coupler and the first electrical coupler are both used to couple two electrical signals into one electrical signal.

[0043] An electrical splitter is used to split a single electrical signal into two electrical signals. The present invention uses an electrical splitter with an output power ratio of 1:9 at two ports. One electrical signal with a ratio of 1 is used as the output linear frequency modulated signal, and the other electrical signal with a ratio of 9 is coupled to the second electrical coupler with the drive signal input and then directly modulated onto the integrated mutual injection laser.

[0044] Radio frequency power amplifiers are used to amplify the current of feedback signals and provide loop gain.

[0045] As one embodiment of the present invention, the short delay unit includes a short single-mode fiber and a first optical attenuator, and the long delay unit includes a long single-mode fiber and a second optical attenuator; the length of the long single-mode fiber is an integer multiple of the length of the short single-mode fiber; wherein, the delay unit may also use a micro resonant cavity to replace the fiber optic disk to improve the miniaturization and integration of the device.

[0046] Furthermore, the single-cycle oscillation frequency of the integrated cross-injection laser provided in this embodiment continuously switches with time within one pulse period. Each single-cycle oscillation mode can be optimized through feedback modes. To optimize the quality of each single-cycle oscillation mode, this embodiment sets short-delay units and long-delay units to ensure delay matching. The switching time of the single-cycle oscillation mode depends on the duration of the driving signal. The short feedback loop is used as the main feedback loop, while the long loop enhances the mode linewidth through self-injection locking. Therefore, the time delay of the short loop should be an integer multiple of the short loop's length; otherwise, the feedback signal will not only have no effect on the optimized linear frequency modulated signal but will also lead to multiple modulation modes and additional mode competition within the laser, thereby disrupting the original state inside the laser. In Fourier mode-locking technology, loop delay is crucial. If the loop delay is mismatched, the single-cycle state operating within the cavity of the integrated cross-injection semiconductor laser cannot achieve frequency consistency with the RF signal fed back to the laser, thus causing positive feedback optimization to fail. Figure 3 As shown in the diagram, the spectrum of the linear frequency modulation signal generator provided in this embodiment when it starts oscillating without a driving signal can be used to measure the free oscillation frequency. The delay is the reciprocal of the free oscillation frequency. The non-overlapping frequency modes generated by the short loop and the long loop are canceled out, while the overlapping frequency modes are retained (e.g., Figure 3 (As shown by the dark lines), and the contrast of the comb teeth and the line width have been improved.

[0047] In one embodiment, the present invention also provides a method for generating a linear frequency modulated (LFM) signal, which uses the above-described LFM signal generating apparatus to generate a LFM signal, and the specific steps include:

[0048] Step 1: Apply a bias current to the integrated mutual injection laser to make the integrated mutual injection laser operate in a single-cycle state to generate a single-cycle optical signal;

[0049] In step 1, a bias current is applied to the integrated laser, and the intensity and wavelength of the output optical signals of the front and rear lasers are changed simultaneously, so that the integrated mutual-injection laser operates in a single-cycle state. The single-cycle state is a nonlinear effect generated in the integrated mutual-injection laser. When the output optical signals of the front and rear lasers are mutually injected and their frequencies are close, the output optical signal of the integrated mutual-injection laser will enter the single-cycle state. When the single-cycle optical signal enters the photodetector for photoelectric conversion, a point-frequency microwave signal, i.e., the single-cycle oscillation frequency, is obtained. The frequency of this signal is the difference in wavelength between the output optical signals of the front and rear lasers. A bias current can also be applied to the phase region to change the refractive index of the material. When the optical signals of the front and rear lasers pass through the phase region, their optical path and power change accordingly, thereby slightly changing the injection ratio between the front and rear lasers and achieving the effect of precisely tuning the wavelength interval between them.

[0050] Step 2: The optical signal is input to the fiber optic splitter and split into two identical beams via fiber optic patch cords; the electrical signal generated by one beam passing through the short delay unit and the first photodetector in sequence, and the electrical signal generated by the other beam passing through the long delay unit and the second photodetector in sequence, are input to the first electrical coupler for coupling and then amplified by the power amplifier;

[0051] Specifically, by adjusting the first optical attenuator of the short delay unit and the second optical attenuator of the long delay unit, the loop gain of the photoelectric feedback is changed, so that the signal-to-noise ratio of the generated linear frequency modulated signal can achieve the best effect.

[0052] Step 3: The amplified electrical signal is input to the electrical splitter and split into two paths. One path, accounting for 10%, is used as the output linear frequency modulated signal, and the other path, accounting for 90%, is coupled to the drive signal input to the second electrical coupler and then directly modulated onto the integrated cross-injection laser.

[0053] In step 3, the driving signal is a low-repetition-rate sawtooth wave signal generated by a waveform generator, which is used to achieve rapid switching of the single-cycle oscillation frequency. This also changes the rapid change of the oscillation frequency in the photoelectric oscillator, realizing the generation of a linear frequency modulation signal.

[0054] During the experiment, in this embodiment, the bias currents of the pre- and post-injection lasers were fixed at 135mA and 146mA, respectively, with no power applied to the phase region. The output signal frequency interval between the pre- and post-injection lasers was 15GHz. The longer the fiber, the narrower the generated signal linewidth. Theoretically, a longer fiber in the long delay unit improves the purity of the linear frequency modulated signal. However, excessively long fibers increase system cost and size. Therefore, in this embodiment, the lengths of the short single-mode fiber and the long single-mode fiber were set to 1249 meters and 5102 meters, respectively. At this length, the delay of the long delay unit is exactly four times that of the short loop delay, resulting in the best spectral purity of its feedback mode. The mode frequency interval of the short delay unit was 163.65kHz, and the mode frequency interval of the long delay unit was 40.913kHz, with a corresponding time delay τ. SL and τ LL The delay times are approximately 6.11 µs and 24.44 µs, respectively; to ensure that the short-delay mode dominates in this opto-oscillator, the optical power (P) of the short-delay unit is... SL It should be greater than the power of the long delay unit (P). LL ), P in the experiment SL = -7.5dBm,P LL = -16dBm; Experimental results are as follows Figure 4-6 As shown.

[0055] Reference Figure 4 As shown, the time-frequency diagram obtained after performing a short-time Fourier transform on the time-series waveform of the linear frequency modulation signal generated by the present invention is displayed. The generated linear frequency modulation signal has a maximum bandwidth of 8GHz and a time-bandwidth product of 48800. The dark lines are thinner, indicating higher signal purity. The improvement in spectral purity is reflected in the increased contrast of individual comb teeth and the narrower line width. Figure 5 In this study, the comb tooth contrast reached 45dB, demonstrating that this invention effectively improves the time-bandwidth product and spectral purity of linear frequency modulated signals generated by optical technology.

[0056] Reference Figure 6 As shown, the pulse compression characteristics of the linear frequency modulated signal generated by this invention are verified using the autocorrelation function; the full width at half-wave (WWHM) and pulse compression ratio are key parameters for measuring its pulse compression characteristics, both of which can be seen from the signal autocorrelation curve; the pulse compression ratio is approximately equal to the time-bandwidth product of the uncompressed pulse, a value derived by multiplying the time duration by the spectral bandwidth; this means that pulses with a higher time-bandwidth product will result in a higher pulse compression ratio, ultimately achieving improved distance resolution; from Figure 6The autocorrelation curve of the generated linear frequency modulated (LFM) signal shows that it has a center frequency of 14 GHz, a bandwidth of 8 GHz, and a time length of 6.11 μs. Theoretically, its time-bandwidth product is calculated to be 48800. The full width at half maximum (FWHM) of the curve is 132 ps, and the corresponding pulse compression ratio is calculated to be 46288, which is close to the theoretical time-bandwidth product value. Therefore, the LFM signal generated by this invention has good pulse compression characteristics.

[0057] In summary, the linear frequency modulation (LFM) signal generation device and method provided in the embodiments of the present invention can generate a LFM signal with high stability, high purity and large time-bandwidth product, and the LFM signal has good pulse compression characteristics; moreover, the device has a compact structure, is easy to integrate, is convenient and flexible to use, and has low cost, and has good application prospects.

[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A linear frequency modulation signal generating device, characterized in that, It includes an integrated mutual injection laser, an optical fiber splitter, a short delay unit, a long delay unit, a first photodetector, a second photodetector, a first electrical coupler, an RF power amplifier, an electrical splitter, and a second electrical coupler; The integrated inter-injection laser is used to generate a single-cycle optical signal. The optical signal is split into two beams by an optical fiber splitter. One beam passes through the short delay unit and the first photodetector in sequence before entering the first electrical coupler. The other beam passes through the long delay unit and the second photodetector in sequence before entering the first electrical coupler. The electrical signal synthesized by the first electrical coupler is amplified by the radio frequency power amplifier and then input into the electrical splitter to be split into two paths. One path outputs a linear frequency modulated signal, and the other path is coupled with the drive signal and input into the second electrical coupler and directly modulated onto the integrated inter-injection laser.

2. The linear frequency modulation signal generating device according to claim 1, characterized in that, The integrated mutual injection laser includes a front laser, a rear laser, and a phase region sharing the same ridge waveguide structure. The phase region is located between the front laser and the rear laser. Both the front laser and the rear laser are equipped with electrical isolators between themselves and the phase region. The front laser and the rear laser are in a mutual injection state.

3. The linear frequency modulation signal generating device according to claim 2, characterized in that, An optical isolator is provided at the output port of the integrated mutual injection laser.

4. The linear frequency modulation signal generating device according to claim 1, characterized in that, The integrated mutual injection laser is connected to the fiber optic splitter via fiber optic patch cords.

5. The linear frequency modulation signal generating apparatus according to any one of claims 1 to 4, characterized in that, The short delay unit includes a short single-mode fiber and a first optical attenuator, and the short single-mode fiber is connected to the first optical attenuator; the long delay unit includes a long single-mode fiber and a second optical attenuator, and the long single-mode fiber is connected to the second optical attenuator.

6. The linear frequency modulation signal generating device according to claim 5, characterized in that, The length of the long single-mode fiber is an integer multiple of the length of the short single-mode fiber, and the length of the long single-mode fiber is greater than the length of the short single-mode fiber.

7. The linear frequency modulation signal generating device according to claim 1, characterized in that, The ratio of optical power output from the two ports of the optical fiber splitter is 1:

1.

8. The linear frequency modulation signal generating apparatus according to claim 1 or 7, characterized in that, The power output ratio of the two ports of the electrical splitter is 1:9; wherein, the electrical signal with a ratio of 1 is used as the output linear frequency modulation signal, and the other electrical signal with a ratio of 9 is coupled with the drive signal input to the second electrical coupler and then directly modulated onto the integrated mutual injection laser.

9. A method for generating a linear frequency modulated signal, characterized in that, A linear frequency modulation signal is generated using the linear frequency modulation signal generating device as described in any one of claims 1 to 7.

10. The linear frequency modulation signal generation method according to claim 9, characterized in that: The step of generating a linear frequency modulated electrical signal includes: A bias current is applied to the integrated mutual injection laser to make the integrated mutual injection laser operate in a single-cycle state to generate a single-cycle optical signal. The optical signal is input to the optical fiber splitter via an optical fiber patch cord and split into two identical beams. One beam, after passing through a short delay unit and a first photodetector, generates an electrical signal, which, along with the other beam, after passing through a long delay unit and a second photodetector, generates an electrical signal. These signals are then coupled to a first electrical coupler and amplified by a power amplifier. The amplified electrical signal is input to an electrical splitter and split into two paths. One path, accounting for 10% of the signal, is used as the output linear frequency modulated signal, while the other path, accounting for 90%, is coupled to the drive signal input to the second electrical coupler and then directly modulated onto the integrated mutual injection laser.

Images