A novel frequency tuning signal generation device based on an optical frequency shifting loop

Abstract

This application relates to the field of microwave photonics and discloses a novel frequency-tuned signal generation device based on an optical frequency-shifting loop. The optical frequency-shifting loop includes an optical switch, a cyclic frequency-shifting loop, and an injection-locking module. The optical switch is used to truncate the input single-frequency continuous light to generate periodic optical pulses, which are then output to the cyclic frequency-shifting loop. The cyclic frequency-shifting loop performs N cyclic frequency shifts on each period of the optical pulse, generating a frequency-tuned signal whose frequency continuously increases with the number of cycles. This frequency-tuned signal is then injected into the injection-locking module. The injection-locking module locks the frequency of the injected frequency-tuned signal, boosts its power to a target power, and outputs it. This solution addresses the problems of decreased signal flatness, reduced repeatability, and low power when generating large-bandwidth signals. It significantly improves the flatness and repeatability of the output signal from the optical frequency-shifting loop, providing a high-power, high-flatness frequency-tuned signal.

Description

Technical Field

[0001] This application relates to the field of microwave photonics, and in particular to a novel frequency tuning signal generation device based on an optical frequency shifting loop. Background Technology

[0002] With the rapid development of microwave photonics technology, a photonic structure called Recirculating Frequency-Shifting Fiber Loop (RFSFL) has attracted widespread attention as a powerful and simple tool for a variety of applications. RFSFL is characterized by using gated optical pulses as input to the fiber loop, with a duration equal to or slightly shorter than the loop's round-trip time, typically achieved by periodically trunculating a single-frequency continuous-wave laser using an optical switch. This RFSFL is primarily used to synthesize stepped-frequency continuous-wave (SFCW) optical signals with ultra-wideband capabilities, absorption spectroscopy measurement, optical ranging, and distributed fiber optic sensing. Furthermore, when combined with photonic heterodyne detection, it can generate broadband microwave, millimeter-wave, and even terahertz signals for ranging and radar imaging. The rapid scanning capability and the inherent frequency-time linearity of the synthesized signal give RFSFL significant potential for achieving high-resolution, high-speed sensing across the entire electromagnetic spectrum.

[0003] As the requirements for distance resolution in distance measurement become increasingly stringent, signals with larger bandwidths are needed for measurement. Generating large-bandwidth signals using RFSFL (Radio Frequency Shifter) requires continuously increasing the number of cycles of the optical pulse in the frequency shift loop. Generating ultra-large bandwidth signals often necessitates hundreds or even thousands of cycles. After numerous cycles, the generated broadband signal becomes increasingly difficult to control, resulting in low power, generally poor signal flatness, and low repeatability of the generated SFCW (Short-Fold Fiber Wound) signal. Consequently, the broadband signal's performance falls far short of expectations in practical applications. This performance bottleneck has become a key obstacle restricting the penetration of RFSFL into high-end fields. Poor signal flatness leads to an imbalance in the transmission gain of different frequency components, causing ambiguity in peak positioning after ranging, directly reducing ranging accuracy, and potentially even affecting the ranging range. In the field of high-resolution microwave photonic radar, every 1dB deterioration in signal amplitude flatness increases the target distance resolution error by approximately 5%, while poor signal repeatability leads to large random fluctuations in ranging measurements, resulting in poor consistency of ranging results.

[0004] Therefore, the problems of reduced signal flatness, decreased signal repeatability, and lower power when generating large bandwidth signals are important issues that the industry urgently needs to address. Summary of the Invention The purpose of this application is to provide at least one novel frequency-tuned signal generation device based on an optical frequency-shifting loop, which can at least solve the problems of reduced signal flatness, reduced signal repeatability, and low power when generating large bandwidth signals. It can at least achieve a significant improvement in the flatness and repeatability of the output signal of the optical frequency-shifting loop, and provide a high-power, high-flatness frequency-tuned signal.

[0005] This application provides a novel frequency tuning signal generation device based on an optical frequency shifting loop, including an optical frequency shifting loop, wherein the optical frequency shifting loop includes: an optical switch, a cyclic frequency shifting loop, and an injection locking module; The optical switch is used to truncate the input single-frequency continuous light to generate periodic optical pulses, and output the optical pulses to the cyclic frequency shifting loop; The cyclic frequency shifting loop is used to perform N cyclic frequency shifts on the optical pulse in each cycle to generate a frequency tuning signal whose frequency continuously increases with the number of cycles. The frequency tuning signal is then injected into the injection locking module, where N is a positive integer. The injection locking module is used to lock the frequency of the injected frequency tuning signal, increase the power of the frequency tuning signal to the target power, and output it.

[0006] Optionally, the injection locking module includes a slave laser, wherein the slave laser is the master laser with the cyclic frequency shifting loop; The injection locking module is used to control the power of the injected frequency tuning signal and the frequency difference between the frequency tuning signal and the slave laser when the slave laser is operating in the optical injection locking mode, so that the slave laser locks the frequency of the frequency tuning signal, increases the power of the frequency tuning signal to the target power and outputs it.

[0007] Optionally, the injection locking module further includes: a circulator; The circulator is used to inject the frequency tuning signal output from the cyclic frequency shifting loop into the slave laser, and to output the frequency tuning signal output from the slave laser.

[0008] Optionally, the injection locking module further includes: an optical attenuator; The optical attenuator is used to control the power attenuation of the frequency tuning signal output by the cyclic frequency shifting loop to the target injection power, and output it to the circulator; The circulator is specifically used to inject the frequency-tuned signal, attenuated to the target injection power, into the slave laser.

[0009] Optionally, the laser has a driver; The driver is used to control the temperature of the slave laser to stabilize within a target temperature range in order to prevent the slave laser from losing lock.

[0010] Optionally, the laser is a laser without an optical isolator.

[0011] Optionally, the slave laser includes a distributed feedback laser or a Fabry-Perot laser.

[0012] Optionally, the optical fibers and optical devices used in the optical path before the output end of the laser are all polarization-maintaining fibers to maintain the polarization state of the light, so as to ensure stable output from the laser.

[0013] Optionally, the cyclic frequency shifting loop includes a first optical coupler, an optical amplifier, an optical filter, and an optical frequency shifter connected in sequence; The optical frequency shifting loop further includes an arbitrary waveform generator; the arbitrary waveform generator is used to control the switching of the optical switch based on a first driving signal, so that the optical switch is periodically turned on and remains on for a first duration. Turn off the second duration The first duration Equal to the duration of one cycle frequency shift in the cyclic frequency shift loop. ; and, based on the second driving signal, controlling the switching of the optical frequency shifter, wherein the first driving signal and the second driving signal are complementary signals; the period of the frequency tuning signal satisfy ; The optical switch is specifically used to output the optical pulse to the first optical coupler; The first optical coupler is used to split the input optical pulse into two beams and output them to the optical amplifier and the injection locking module, respectively; The optical amplifier and the optical filter are used to amplify the frequency-shifting spectral region of the input optical pulse and output it to the optical frequency shifter; wherein, the optical filter is used for frequencies of The optical signal operates in bandpass mode, or the optical filter is for frequencies of... and greater than The optical signal operates in bandpass mode to suppress ASE noise while limiting the spectral shape. The frequency of the single-frequency continuous light; The optical frequency shifter is used to shift and fix the frequency of each passing optical pulse. The output is then sent to the first optical coupler, and after N cyclic frequency shifts, the optical pulse reaches its bandwidth. .

[0014] Optional components also include: a light source, a second optical coupler, a third optical coupler, and a photodetector; The light source is used to generate single-frequency continuous light; The second optical coupler is used to split the single-frequency continuous light into two beams and output them to the optical frequency shifting loop and the third optical coupler, respectively; The third optical coupler is used to receive the frequency tuning signal from the optical frequency shifting loop and the single-frequency continuous light from the second optical coupler, and output it to the photodetector; The photodetector is used to detect light intensity and outputs a step frequency signal with a constant chirp rate and increasing bandwidth with the number of cycles based on the detection result.

[0015] The advantages of this application compared to the prior art are: The novel frequency-tuning signal generation device based on an optical frequency-shifting loop disclosed in this application employs an optical switch, a cyclic frequency-shifting loop, and an optical injection locking module to jointly construct a novel optical frequency-shifting loop. The optical switch is used to truncate the input single-frequency continuous light to generate periodic optical pulses, which are then output to the cyclic frequency-shifting loop. The cyclic frequency-shifting loop performs N cyclic frequency shifts on the optical pulses in each cycle, generating a frequency-tuning signal whose frequency continuously increases with the number of cycles. The frequency-tuning signal is then injected into the injection locking module, where N is a positive integer. The injection locking module locks the frequency of the injected frequency-tuning signal, boosts the power of the frequency-tuning signal to a target power, and outputs it. This improves the power, flatness, and repeatability of the frequency-tuning signal output by the optical frequency-shifting loop, providing a high-power, high-flatness frequency-tuning signal. It solves the problems of decreased signal flatness and reduced signal repeatability when generating large-bandwidth signals, and also addresses the application limitations caused by low signal power. Attached Figure Description

[0016] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, and these illustrative descriptions do not constitute a limitation on the embodiments.

[0017] Figure 1 This is a schematic diagram of the structure of a novel frequency tuning signal generation device based on an optical frequency shifting loop, provided in one embodiment of this application. Figure 1 ; Figure 2 This is a comparative schematic diagram of the frequency tuning signal output by a cyclic frequency shifting loop and an injection locking module provided in another embodiment of this application; Figure 3 This is a schematic diagram of the structure of a novel frequency tuning signal generation device based on an optical frequency shifting loop, provided in another embodiment of this application. Figure 2 . Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the various embodiments of this application to help readers better understand this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0019] The embodiments of this application relate to a novel frequency tuning signal generation device based on an optical frequency shifting loop.

[0020] Compared with the prior art, the embodiments of this application, in the novel frequency tuning signal generation device based on the optical frequency shifting loop, employ an optical switch, a cyclic frequency shifting loop, and an optical injection locking module to jointly construct a novel optical frequency shifting loop. The optical switch is used to truncate the input single-frequency continuous light to generate periodic optical pulses, and outputs the optical pulses to the cyclic frequency shifting loop. The cyclic frequency shifting loop is used to perform N cyclic frequency shifts on the optical pulses of each period, generating a frequency tuning signal whose frequency continuously increases with the number of cycles. The frequency tuning signal is injected into the aforementioned injection locking module, where N is a positive integer. The injection locking module is used to lock the frequency of the injected frequency tuning signal, increase the power of the frequency tuning signal to the target power, and output it. In this way, the power, flatness, and repeatability of the frequency tuning signal output by the optical frequency shifting loop are improved, providing a high-power, high-flatness frequency tuning signal. This solves the problem of decreased signal flatness and reduced signal repeatability when generating large bandwidth signals, and also solves the problem of application limitations caused by low signal power.

[0021] The following is a detailed description of the implementation details of the novel frequency tuning signal generation device based on an optical frequency shifting loop in this embodiment. The following content is only for the convenience of understanding and is not necessary for implementing this solution.

[0022] The embodiments of this application provide a novel frequency tuning signal generation device based on an optical frequency shifting loop, such as... Figure 1 As shown, it includes an optical frequency shifting loop 10, which includes an optical switch 11, a cyclic frequency shifting loop 12, and an injection locking module 13. The optical switch 11 is used to cut off the input single-frequency continuous light to generate periodic optical pulses, and output the optical pulses to the cyclic frequency shifting loop 12; The cyclic frequency shifting loop 12 is used to perform N cyclic frequency shifts on the optical pulse of each cycle, generating a frequency tuning signal whose frequency continuously increases with the number of cycles, and injecting the frequency tuning signal into the above-mentioned injection locking module 13, where N is a positive integer; The injection locking module 13 is used to lock the frequency of the injected frequency tuning signal, increase the power of the frequency tuning signal to the target power, and output it.

[0023] The optical switch 11, the cyclic frequency shifting loop 12, and the injection locking module 13 constitute a novel optical frequency shifting loop.

[0024] The cyclic frequency shifting loop 12 is an RFSFL (Radio Frequency Shifting Fluid). In the cyclic frequency shifting loop 12, the frequency of the optical pulse increases with each cycle, thereby generating a frequency tuning signal with continuously accumulating frequency. In a single cycle of frequency shifting, the optical pulse is shifted to a fixed frequency. After N cyclic frequency shifts, the bandwidth is reached. For example, N is a positive integer greater than 1.

[0025] The injection locking module 13 has an optical injection locking function, which can lock the frequency tuning signal output by the cyclic frequency shifting loop 12, thereby locking the frequency of the frequency tuning signal output by the cyclic frequency shifting loop 12, and ensuring that the power of the frequency tuning signal is stably output according to the target power set by the injection locking module 13. The target power is the original output power of the injection locking module 13 itself. The target power can be set according to actual needs, and can meet high-power requirements. The output signal of the optical frequency shifting loop 10 is the frequency tuning signal whose frequency is locked by the injection locking module 13 and reaches the target power. In other words, the output signal of the optical frequency shifting loop 10 is a frequency conversion signal. For example, the final frequency tuning signal is a stepped-frequency continuous wave optical signal.

[0026] The value of N can be controlled by optical switch 11, making a large number of frequency steps possible, thereby realizing the output of ultra-wideband stepped frequency continuous wave optical signals.

[0027] This scheme employs a novel optical frequency shifting loop combining cyclic frequency shifting technology and optical injection locking. During optical injection locking, the injection locking module 13 locks the frequency of the frequency tuning signal and its frequency changes, thus maintaining the original output power of the injection locking module 13 itself. In this way, a significant and stable increase in the output signal power of the optical frequency shifting loop 10 is achieved, effectively overcoming the limitations of the original optical frequency shifting loop in generating large-bandwidth signals, such as low power, uneven output signal, and poor repeatability. It realizes the generation of high-power, high-flatness, ultra-wideband, and high-linearity frequency tuning signals based on optical injection locking technology and cyclic frequency shifting loop, which has great potential for advancing related detection, sensing, and measurement applications in the microwave, millimeter-wave, terahertz wave, and spectral regions. Based on this, this solution provides an optical frequency shifting loop that can generate high-power, high-flatness frequency-tuned signals. This optical frequency shifting loop can synthesize stepped-frequency continuous-wave optical signals based on pulsed light injection and loop switching RFSFL. The chirp rate and bandwidth are controllable, the signal bandwidth range is large, the structure is simple, and the output signal power is greatly improved by using optical injection locking. It can also maintain the stability of the output signal power of the optical frequency shifting loop, and greatly improve the flatness and repeatability of the output signal of the optical frequency shifting loop.

[0028] In this embodiment, an optical frequency shifting loop 10 is constructed by using an optical switch 11, a cyclic frequency shifting loop 12, and an optical injection locking module 13. The optical switch 11 is used to cut off the input single-frequency continuous light to generate periodic light pulses, and output the light pulses to the cyclic frequency shifting loop 12. The cyclic frequency shifting loop 12 is used to perform N cyclic frequency shifts on the light pulses of each cycle to generate a frequency tuning signal whose frequency continuously increases with the number of cycles. The frequency tuning signal is injected into the injection locking module 13, which is used to lock the frequency of the injected frequency tuning signal, increase the power of the frequency tuning signal to the target power, and output it. In this way, the power, flatness, and repeatability of the frequency tuning signal output by the optical frequency shifting loop 10 are improved, and a high-power, high-flatness frequency tuning signal is provided.

[0029] In some embodiments, such as Figure 1 As shown, the injection locking module 13 includes a slave laser, which is a master laser with a cyclic frequency shifting loop 12.

[0030] The injection locking module 13 is used to control the power of the injected frequency tuning signal and the frequency difference between the frequency tuning signal and the slave laser when the slave laser is operating in the optical injection locking mode, so that the slave laser locks the frequency of the frequency tuning signal, increases the power of the frequency tuning signal to the target power and outputs it.

[0031] The laser has an optical injection-locked mode, and the laser operates within the range of parameters (such as wavelength and power) of the injection-locked mode to ensure frequency locking stability, thereby continuously and stably locking the frequency of the frequency-tuned signal.

[0032] The frequency tuning signal output by the cyclic frequency shifting loop 12 is injected into the slave laser via optical injection locking. By controlling the power of the frequency tuning signal and the frequency difference between the frequency tuning signal and the slave laser, the slave laser locks the frequency of the frequency tuning signal output by the cyclic frequency shifting loop 12, thereby increasing the power of the frequency tuning signal to the target power and outputting it. This significantly improves the power, flatness, and repeatability of the output signal of the optical frequency shifting loop 10.

[0033] The target power is the original output power of the laser itself.

[0034] Specifically, the slave laser is controlled to operate in a stable optical injection locked state. The frequency tuning signal output from the cyclic frequency shifting loop 12 is injected into the slave laser. At this time, the frequency output by the slave laser changes with the frequency of the frequency tuning signal output by the cyclic frequency shifting loop 12, while the output power of the slave laser remains at its original output power. The output signal of the slave laser is the output signal of the entire optical frequency shifting loop 10, that is, the frequency tuning signal that has been frequency-locked by the slave laser and has reached the target power. In this way, a high-power, highly flat output signal of the optical frequency shifting loop 10 is obtained, achieving the purpose of optimizing the output signal of the optical frequency shifting loop 10.

[0035] In some embodiments, such as Figure 1 As shown, the injection locking module 13 further includes a circulator; the circulator is used to inject the frequency tuning signal output from the cyclic frequency shifting loop 12 into the laser and output the frequency tuning signal output from the laser.

[0036] A circulator allows a beam of light to travel unidirectionally in a fixed sequence.

[0037] Based on this, in this embodiment, a circulator is used to inject the frequency tuning signal output by the cyclic frequency shifting loop 12 into the slave laser, ensuring that the frequency tuning signal of the cyclic frequency shifting loop 12 can be accurately injected into the slave laser. At the same time, the frequency tuning signal locked by the slave laser and reaching the target power is accurately output, avoiding interference between optical signals.

[0038] In some embodiments, such as Figure 1 As shown, the injection locking module 13 also includes: an optical attenuator; the optical attenuator is used to control the power attenuation of the frequency tuning signal output by the cyclic frequency shifting loop 12 to the target injection power, and output it to the circulator; The circulator is specifically used to inject a frequency-tuned signal attenuated to the target injection power into the laser.

[0039] The target injection power is the injection power required to achieve the laser's optical injection locked mode. By adjusting the optical attenuator, the power of the frequency tuning signal output from the cyclic frequency shift loop 12 can be attenuated to the target injection power required by the laser.

[0040] The target injection power can be determined by the relationship between the injection power and the detuning frequency (i.e., the frequency difference between the frequency tuning signal and the slave laser). The frequency difference can be controlled by the wavelength of the slave laser. In this way, the slave laser can be controlled to operate in a stable optical injection locked state by adjusting the relationship between the injection power and the detuning frequency.

[0041] In this embodiment, by setting an optical attenuator, the frequency tuning signal output by the cyclic frequency shifting loop 12 can be injected into the slave laser after passing through the optical attenuator. By adjusting the optical attenuator, the injection power can be actively controlled to meet the requirements of injection locking technology.

[0042] In some embodiments, the laser is a laser without an optical isolator.

[0043] To meet the requirements of optical injection locking technology, the slave laser can be any existing laser without an isolator. By setting the slave laser to a laser without an optical isolator, it is ensured that the frequency tuning signal output from the cyclic frequency shifting loop 12 can be injected into the cavity of the slave laser.

[0044] For example, the laser may include a distributed feedback (DFB) laser or a Fabry-Perot (FP) laser.

[0045] Because DFB lasers possess high side-mode rejection ratios and excellent single-mode characteristics, they can effectively maintain phase coherence and suppress mode competition in the injection-locked state, making them suitable for applications with high requirements for signal purity and phase noise. In this embodiment, a DFB laser is used as the slave laser. Utilizing its high side-mode rejection ratio and stable single-mode characteristics, the phase synchronization performance between the master and slave lasers can be effectively improved during the injection-locked process, thereby enhancing the signal-to-noise ratio and frequency stability of the final frequency-tuned signal.

[0046] FP lasers have a simple structure and low cost, but they are prone to multimode oscillations during free operation, making them suitable for applications where system cost is sensitive and the number of cycles is limited.

[0047] In some embodiments, the slave laser has a driver; the driver is used to control the temperature of the slave laser to stabilize within a target temperature range to prevent the slave laser from losing lock.

[0048] The stability of optical injection locking is highly affected by the temperature of the external environment. Temperature fluctuations can easily cause laser characteristic drift and may lead to loss of locking.

[0049] The target temperature range is the temperature range that ensures the laser operates in injection-locked mode.

[0050] In this embodiment, a driver is used to stably control the temperature of the slave laser to prevent temperature fluctuations caused by changes in the external environment, which could lead to a loss of lock.

[0051] In some embodiments, the driver is also used to adjust the bias current from the laser to stabilize the voltage from the laser.

[0052] By precisely adjusting the bias current and temperature of the laser, flexible control over the power and wavelength output from the laser can be achieved, thereby further optimizing noise performance and frequency tuning range in broadband signal generation.

[0053] In some embodiments, such as Figure 1 As shown, the cyclic frequency shifting loop 12 includes a first optical coupler, an optical amplifier, an optical filter, and an optical frequency shifter connected in sequence.

[0054] The optical frequency shifting loop 10 also includes an arbitrary waveform generator 14; the arbitrary waveform generator 14 is used to control the switching of the optical switch 11 based on the first driving signal, so that the optical switch 11 is periodically turned on and continues for a first duration. Turn off the second duration First duration It equals the duration of one cycle frequency shift in the cyclic frequency shift loop 12. ; and, based on the second driving signal, controlling the switching of the optical frequency shifter, wherein the first driving signal and the second driving signal are complementary signals; the period of the frequency tuning signal satisfy .

[0055] The optical switch 11 is specifically used to output optical pulses to the first optical coupler.

[0056] The first optical coupler is used to split the input optical pulse into two beams and output them to the optical amplifier and injection locking module 13 respectively.

[0057] Optical amplifiers and optical filters are used to amplify the frequency-shifting spectral region of the input optical pulse and output it to an optical frequency shifter; wherein, the optical filter is used for frequencies of... The optical signal operates in bandpass mode, or the optical filter is for frequencies of... and greater than The optical signal operates in bandpass mode to suppress amplified spontaneous emission (ASE) noise while limiting the spectral shape. It represents the frequency of a single-frequency continuous light.

[0058] Optical frequency shifters are used to shift and fix the frequency of each passing optical pulse. The output is then sent to the first optical coupler, and after N cyclic frequency shifts, the optical pulse reaches the bandwidth. .

[0059] Specifically, the single-frequency continuous wave is amplitude modulated by a first driving signal through an optical switch 11, which is periodically opened. Turn off the second duration This produces periodic optical pulses, i.e., gated optical pulses. The optical pulses output from optical switch 11 are sent to the first optical coupler.

[0060] The first optical coupler splits the optical pulse from the optical switch 11 into two beams. One beam is output to the injection-locked module 13, and the other beam serves as the seed signal input and is output to the optical amplifier. The optical amplifier and optical filter are used to amplify the frequency-shifted spectral region of the optical pulse and output it to the optical frequency shifter. Ignoring ASE noise, the optical filter is suitable for frequencies of... The optical signal operates in bandpass mode. Considering ASE noise, the optical filter is suitable for frequencies of... The optical signal operates in bandpass mode and has a certain frequency tolerance, allowing the optical filter to also handle frequencies greater than [frequency value missing]. The optical signal operates in bandpass mode to suppress ASE noise while limiting the spectral shape.

[0061] The first optical coupler also outputs the optical pulses after frequency shifting by the optical frequency shifter to the optical amplifier for the next cycle of frequency shifting; and outputs the optical pulses after frequency shifting by the optical frequency shifter to the injection locking module 13.

[0062] The cyclic frequency shifting loop 12 consists of a first optical coupler, an optical amplifier, an optical filter, and an optical frequency shifter connected sequentially. The optical amplifier can be an erbium-doped fiber amplifier (EDFA). The optical filter can be an optical band-pass filter (OBPF). Together, the EDFA and OBPF provide amplification in the frequency-shifting spectral region, compensating for loop losses primarily caused by external coupling and insertion loss of each device. Each time the optical pulse passes through the optical frequency shifter, it accumulates a pulse that is precisely equal to... The fixed frequency shift reaches the bandwidth after the Nth cycle. When the second drive signal of the optical frequency shifter is turned off, the frequency shifting loop terminates, and a new seed signal is then injected into the cyclic frequency shifting loop 12.

[0063] The first driving signal and the second driving signal are complementary signals, which makes the optical switch 11 and the optical frequency shifter work at different times, so that there is only one cycle of optical pulse in the cyclic frequency shifting loop 12. The complementary signals can prevent interference and improve the signal-to-noise ratio.

[0064] In this embodiment, the cyclic frequency shifting loop 12, through the cooperation of the first optical coupler, optical amplifier, optical filter and optical frequency shifter connected in sequence, can achieve precise cyclic frequency shifting.

[0065] Under the control of the first driving signal, the optical switch 11 can flexibly adjust the width and period of the optical pulse, thereby actively controlling the number of cycles N and the period and bandwidth of the frequency tuning signal.

[0066] There are various types of optical switches 11. For example, an optical switch 11 may be constructed using a Mach-Zehnder modulator, which can achieve the optical switch function through DC bias control. In this embodiment, the optical switch is constructed using an acousto-optic modulator. The periodic electrical pulse signal generated by the arbitrary waveform generator is modulated onto the input optical signal by the acousto-optic modulator, thereby converting the periodic electrical pulse signal into a periodic optical pulse signal, realizing the optical switch function. Furthermore, the operating state of the optical switch can be changed by altering the period and pulse width of the signal generated by the arbitrary waveform generator.

[0067] Alternatively, the optical switch 11 can be an optical switch composed of an acousto-optic modulator. This device is based on the acousto-optic effect and can convert periodic electrical pulse signals into periodic optical pulse signals. The electrical pulse signals act on the modulator in the form of amplitude modulation, thereby modulating the electrical signals onto the optical carrier to generate periodic optical pulse signals, thus constructing an optical switch.

[0068] There are various types of optical frequency shifters. For example, optical frequency shifters use electro-optic modulators or acousto-optic modulators. Since the extinction ratio of electro-optic modulators is currently much lower than that of acousto-optic modulators, electro-optic modulators can be used when the number of cycles is small. However, when the number of cycles is large and an ultra-wide bandwidth signal is generated, acousto-optic modulators can be used to improve the extinction ratio of the optical frequency shifter.

[0069] In this embodiment, the optical frequency shifter is composed of an acousto-optic modulator. Utilizing its high extinction ratio, it approximates the cooperation between an optical switch within the loop that can periodically reset the loop and an external optical switch, preventing any interference between the recirculated light wave in the loop and the next injected seed signal, thus improving the signal-to-noise ratio of the final frequency-tuned signal. Furthermore, this method allows direct adjustment of the pulse width and period of the optical pulse, thereby controlling the time width and number of cycles of the generated signal, and further adjusting the signal period and bandwidth, achieving flexible optimization of signal performance.

[0070] In some embodiments, the optical fibers and optical devices used in the optical path before the output of the laser are all polarization-maintaining fibers to maintain the polarization state of the light, so as to ensure stable output from the laser.

[0071] In the optical frequency shifting loop 10, all optical fibers and optical devices except for the arbitrary waveform generator 14 use polarization-maintaining fibers to maintain the polarization state of the light, thereby stabilizing the output of the entire optical frequency shifting loop 10 and the output from the laser.

[0072] See Figure 2 This diagram shows a comparison of the frequency tuning signals output by the cyclic frequency shifting loop 12 and the injection locking module 13. Figure 2 In the diagram, the dashed line represents the effect of the frequency tuning signal output by the injection locking module 13, and the solid line represents the effect of the frequency tuning signal directly output by the cyclic frequency shifting loop 12. The horizontal axis represents time t, and the vertical axis represents voltage U. Obviously, the frequency tuning signal output by the injection locking module 13 has a better effect, and is a high-power, high-flatness frequency tuning signal.

[0073] like Figure 3 As shown in the figure, the novel frequency tuning signal generation device based on optical frequency shifting loop provided in this application embodiment further includes: a light source 20, a second optical coupler 30, a third optical coupler 40, and a photodetector 50; The light source 20 is used to generate single-frequency continuous light; The second optical coupler 30 is used to split the single-frequency continuous light into two beams and output them to the optical frequency shifting loop 10 and the third optical coupler 40, respectively. The third optical coupler 40 is used to receive the frequency tuning signal from the optical frequency shifting loop 10 and the single-frequency continuous light from the second optical coupler 30, and output it to the photodetector 50. The photodetector 50 is used to detect light intensity and outputs a step frequency signal with constant chirp rate and increasing bandwidth with the number of cycles based on the detection result.

[0074] The aforementioned light source 20 is a laser.

[0075] Among them, the novel frequency tuning signal generation device based on optical frequency shifting loop can be applied to ranging scenarios, and of course, it can also be applied to other scenarios.

[0076] In this embodiment, since the optical frequency shifting loop 10 can provide a high-power, high-flatness frequency tuning signal, the step frequency signal output by the photodetector 50 is thus a high-power, high-flatness signal. In ranging scenarios, the novel frequency tuning signal generation device based on the optical frequency shifting loop can improve the accuracy and resolution of ranging results, avoid affecting the range, and improve the consistency of ranging results.

[0077] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing this application, and in practical applications, various changes can be made to them in form and detail without departing from the spirit and scope of this application.

Claims

1. A novel frequency tuning signal generation device based on an optical frequency shifting loop, characterized in that, The optical frequency shifting loop includes: an optical switch, a cyclic frequency shifting loop, and an injection locking module; The optical switch is used to truncate the input single-frequency continuous light to generate periodic optical pulses, and output the optical pulses to the cyclic frequency shifting loop; The cyclic frequency shifting loop is used to perform N cyclic frequency shifts on the optical pulse in each cycle to generate a frequency tuning signal whose frequency continuously increases with the number of cycles. The frequency tuning signal is then injected into the injection locking module, where N is a positive integer. The injection locking module is used to lock the frequency of the injected frequency tuning signal, increase the power of the frequency tuning signal to the target power, and output it.

2. The novel frequency tuning signal generation device based on an optical frequency shifting loop according to claim 1, characterized in that, The injection locking module includes a slave laser, wherein the slave laser is a master laser with the cyclic frequency shifting loop; The injection locking module is used to control the power of the injected frequency tuning signal and the frequency difference between the frequency tuning signal and the slave laser when the slave laser is operating in the optical injection locking mode, so that the slave laser locks the frequency of the frequency tuning signal, increases the power of the frequency tuning signal to the target power and outputs it.

3. The novel frequency tuning signal generation device based on an optical frequency shifting loop according to claim 2, characterized in that, The injection locking module further includes: a circulator; The circulator is used to inject the frequency tuning signal output from the cyclic frequency shifting loop into the slave laser, and to output the frequency tuning signal output from the slave laser.

4. The novel frequency tuning signal generation device based on an optical frequency shifting loop according to claim 3, characterized in that, The injection locking module further includes: an optical attenuator; The optical attenuator is used to control the power attenuation of the frequency tuning signal output by the cyclic frequency shifting loop to the target injection power, and output it to the circulator; The circulator is specifically used to inject the frequency-tuned signal, attenuated to the target injection power, into the slave laser.

5. The novel frequency tuning signal generation device based on an optical frequency shifting loop according to claim 2, characterized in that, The laser has a driver; The driver is used to control the temperature of the slave laser to stabilize within a target temperature range in order to prevent the slave laser from losing lock.

6. The novel frequency tuning signal generation device based on an optical frequency shifting loop according to claim 2, characterized in that, The laser is a laser without an optical isolator.

7. The novel frequency tuning signal generation device based on an optical frequency shifting loop according to claim 6, characterized in that, The laser source includes a distributed feedback laser or a Fabry-Perot laser.

8. The novel frequency tuning signal generation device based on an optical frequency shifting loop according to claim 2, characterized in that, The optical fibers and optical devices used in the optical path before the output of the laser all employ polarization-maintaining fibers to maintain the polarization state of the light, so as to ensure stable output from the laser.

9. The novel frequency tuning signal generation device based on an optical frequency shifting loop according to any one of claims 1 to 8, characterized in that, The cyclic frequency shifting loop includes a first optical coupler, an optical amplifier, an optical filter, and an optical frequency shifter connected in sequence; The optical frequency shifting loop further includes an arbitrary waveform generator; the arbitrary waveform generator is used to control the switching of the optical switch based on a first driving signal, so that the optical switch is periodically turned on and remains on for a first duration. Turn off the second duration The first duration Equal to the duration of one cycle frequency shift in the cyclic frequency shift loop. ; Furthermore, the switching of the optical frequency shifter is controlled based on the second driving signal, wherein the first driving signal and the second driving signal are complementary signals; the period of the frequency tuning signal... satisfy ; The optical switch is specifically used to output the optical pulse to the first optical coupler; The first optical coupler is used to split the input optical pulse into two beams and output them to the optical amplifier and the injection locking module, respectively; The optical amplifier and the optical filter are used to amplify the frequency-shifting spectral region of the input optical pulse and output it to the optical frequency shifter; wherein, the optical filter is used for frequencies of The optical signal operates in bandpass mode, or the optical filter is for frequencies of... and greater than The optical signal operates in bandpass mode to suppress ASE noise while limiting the spectral shape. The frequency of the single-frequency continuous light; The optical frequency shifter is used to shift and fix the frequency of each passing optical pulse. The output is then sent to the first optical coupler, and after N cyclic frequency shifts, the optical pulse reaches its bandwidth. .

10. The novel frequency tuning signal generation device based on an optical frequency shifting loop according to claim 1, characterized in that, Also includes: Light source, second optical coupler, third optical coupler, and photodetector; The light source is used to generate single-frequency continuous light; The second optical coupler is used to split the single-frequency continuous light into two beams and output them to the optical frequency shifting loop and the third optical coupler, respectively; The third optical coupler is used to receive the frequency tuning signal from the optical frequency shifting loop and the single-frequency continuous light from the second optical coupler, and output it to the photodetector; The photodetector is used to detect light intensity and outputs a step frequency signal with a constant chirp rate and increasing bandwidth with the number of cycles based on the detection result.

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