Sweep frequency light source system based on duty ratio modulation and sweep frequency rate multiplication and modulation method

Abstract

The invention relates to the technical field of frequency sweeping laser, in particular to a frequency sweeping light source system based on duty ratio modulation and frequency sweeping rate multiplication and a modulation method. Comprising a sweep frequency light source module used for providing a unidirectional frequency scanning light signal with a frequency tuning function, performing wavelength scanning by tuning internal frequency driving or frequency resonance, changing resonant frequency and reducing the duty ratio of an output light source signal; a driving control signal generated by the signal generation device is sent to the sweep frequency light source module to realize frequency tuning; the optical separation-delay-coupling device is connected with the sweep-frequency light source module to carry out time delay and signal copying on a sweep-frequency light source; the temperature control module is connected with the sweep-frequency light source module and adjusts and maintains the working environment temperature of the sweep-frequency light source module; the monitoring feedback module is used for monitoring the stability of the light source in real time and judging whether the temperature, driving control frequency or waveform needs to be adjusted or not. The method has the advantages that the duty ratio is reduced, the sweep frequency rate is multiplied, and the sweep frequency rate and the signal stability are improved.

Description

Technical Field

[0001] The present invention relates to the field of frequency-sweeping laser technology, and in particular to a frequency-sweeping light source system and a modulation method based on duty cycle modulation and frequency-sweeping rate multiplication. Background Art

[0002] With the continuous development of medical conditions, my country's demand for modern medical equipment is also increasing. As one of the most important detection methods in ophthalmology, improving the performance of optical coherence tomography (OCT) systems is crucial.

[0003] As an important component of the OCT system, the performance of the swept-frequency light source is directly related to the core technical indicators and final performance of the OCT system, such as imaging resolution and detectable cross-sectional depth. Therefore, improving the performance of the swept-frequency light source is crucial.

[0004] When it comes to improving swept-source technology, the three most important factors are sweep rate, sweep range, and coherence length. The sweep rate of the source determines the imaging speed of the OCT system. For swept lasers, which require wavelength tuning via a wavelength tuning device, the sweep rate is limited by the speed of the wavelength tuning device, resulting in a low sweep rate that cannot meet the high sweep rate requirements of the OCT system.

[0005] There are many technical solutions in the existing technology to improve the scanning rate of swept-frequency light sources. However, most of the solutions cannot achieve a several-fold increase in the scanning rate. Using ordinary buffer level solutions to double the scanning rate will also cause signal distortion due to the gradual increase in buffer levels. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a frequency sweeping light source system and a modulation method based on duty cycle modulation and frequency sweeping rate multiplication.

[0007] The first object of the present invention is to provide a swept frequency light source system based on duty cycle modulation and sweep rate multiplication, comprising a swept frequency light source module, a signal generating device, an optical separation-delay-coupling device, a temperature control module and a monitoring feedback module; The frequency-sweeping light source module is used to provide a unidirectional frequency-sweeping optical signal with a frequency tuning function. It performs wavelength scanning by tuning the internal frequency drive or frequency resonance, changes the resonant frequency, and reduces the duty cycle of the output light source signal. The driving control signal generated by the signal generating device is sent to the frequency tuning device of the frequency sweeping light source module to achieve frequency tuning; The optical separation-delay-coupling device is connected to the swept-frequency light source module to perform time delay and signal replication on the swept-frequency light source; The temperature control module is connected to the frequency sweeping light source module to adjust and maintain the working environment temperature of the frequency sweeping light source module; The two ends of the monitoring feedback module are connected to the temperature control module and the signal generating device respectively, which are used to monitor the stability of the light source in real time and determine whether the signal generating device and the temperature control module need to be adjusted based on the monitored light source performance data.

[0008] Preferably, the swept frequency light source module includes a tunable light source, a frequency tuning device and a frequency selection device; A tunable light source is used to provide basic optical signal output; a frequency tuning device is used to control the frequency change of the light source to achieve wavelength scanning; a frequency selection device is used to select an optical signal of a specific wavelength to ensure that the wavelength of the output optical signal meets the requirements; the signal duty cycle is reduced by increasing the resonant wave amplitude of the frequency selection device and calibrating the center wavelength position of the frequency selection device.

[0009] Preferably, the optical separation-delay-coupling device is a light buffer stage device; the signal generating device is a semiconductor optical amplifier; the tunable light source is an FDML laser; and the frequency selection device is a Fabry-Perot filter used in the FDML laser. By changing the distance between the fiber end faces of the Fabry-Perot filter, the cavity length is changed, thereby adjusting the filter's transmission spectrum and achieving wavelength selection. By applying a sinusoidal signal to the Fabry-Perot filter and changing the frequency, amplitude, and offset of the modulation signal, the center wavelength and sweep range of the swept light source can be adjusted. A sinusoidal wave signal is applied to a semiconductor optical amplifier, and the duty cycle of the output signal is reduced by adjusting the duty cycle of the sinusoidal wave signal.

[0010] Preferably, the tunable light source is a MEMS grating external cavity swept laser; the frequency selection device is an external cavity grating in the MEMS grating external cavity swept light source; By rotating the external cavity grating to control the grating angle, the wavelength is selected to achieve the output of the swept light source; by increasing the vibration angle of the galvanometer, the amplitude of the sine wave function is increased and the duty cycle of the signal is reduced.

[0011] Preferably, the tunable light source is a MEMS-VCSEL swept-frequency laser; the frequency selection device is an air gap in the VCSEL cavity modulated by the MEMS in the MEMS-VCSEL swept-frequency light source; By applying voltage to generate electrostatic force, the MEMS cantilever is deflected, the air gap height is changed, and then the effective cavity length of the VCSEL is changed, wavelength tuning is achieved, and a swept light source is output; the duty cycle is adjusted by changing the driving frequency and driving voltage of the MEMS to reduce the duty cycle of the signal.

[0012] Preferably, the optical separation-delay-coupling device comprises: The separation unit is used to separate the frequency-sweeping optical signal into two optical signals without changing the original properties of the signals, and the separation unit includes a wavelength division multiplexer or a coupler; The delay unit is used to delay one of the optical signals in time without changing other inherent properties, and the delay unit includes a single-mode optical fiber; The coupling unit is used to combine two optical signals into one beam; the coupling unit includes an optical coupler.

[0013] Preferably, the optical separation-delay-coupling device is used more than once, and the exponential growth of the frequency sweep rate is achieved by performing multiple frequency sweep light source light wave replications; The temperature control module is at least one of a heater, a refrigerator, and a thermocouple.

[0014] A second object of the present invention is to provide a modulation method for a swept frequency light source system based on duty cycle modulation and sweep rate multiplication, wherein duty cycle modulation is performed on the swept frequency light source system based on duty cycle modulation and sweep rate multiplication; the method specifically comprises the following steps: S1. Initialize the system: Start the swept light source module, adjust the temperature control module, and adjust the working environment temperature of the swept light source module to a preset stable range; S2. Input a periodic electrical signal to the frequency tuning device of the swept light source module through a signal generating device to adjust the driving frequency of the frequency driving device; by increasing the resonant wave amplitude of the frequency selection device and calibrating the center wavelength position of the frequency selection device, thereby reducing the signal duty cycle; S3. After the duty cycle modulation is completed, the optical signal output by the swept light source module is introduced into the optical separation - delay - coupling device to achieve a doubling of the sweep rate of the swept signal; S4 starts the monitoring feedback module, monitors the stability of the light source in real time, and obtains the output light signal of the light source; determines whether the signal generating device and the temperature control module need to be adjusted according to the monitored light source performance data; S5. Based on the monitoring feedback, fine-tune and optimize the system parameters to ensure the sweep performance and stability.

[0015] Preferably, the monitoring feedback module includes an algorithm unit and a control unit; the algorithm unit is used to analyze and process the monitored light source performance data to determine whether the signal generating device and the temperature control module need to be adjusted; if the monitored light source performance fluctuates or deviates, the control unit sends an adjustment instruction to the signal generating device and the temperature control module, adjusts the frequency, waveform, duty cycle and other parameters of the signal generating device according to the instruction, and adjusts the temperature control module to stabilize the working environment temperature to maintain the stability and accuracy of the system.

[0016] Preferably, the frequency selection device in step S2 is a Fabry-Perot filter used in an FDML laser; the cavity length is changed by changing the distance between the fiber end faces of the Fabry-Perot filter, thereby adjusting the transmission spectrum of the filter and achieving wavelength selection; the central wavelength and the sweep range of the swept light source are adjusted by applying a sinusoidal wave signal to the Fabry-Perot filter and changing the frequency, amplitude and offset of the modulation signal; Alternatively, the frequency selection device in step S2 is an external cavity grating in a MEMS grating external cavity swept frequency light source; the wavelength is selected by rotating the external cavity grating to control the grating angle, thereby realizing the output of the swept frequency light source; and the amplitude of the sine wave function is increased by increasing the vibration angle of the galvanometer, thereby reducing the duty cycle of the signal; Alternatively, the frequency selection device in step S2 is an air gap under MEMS modulation in a MEMS-VCSEL; an electrostatic force is generated by applying a voltage to the MEMS to deflect the MEMS cantilever, thereby changing the air gap height and thereby changing the effective cavity length of the VCSEL, thereby realizing a swept-frequency light source with adjustable output wavelength; and the duty cycle is adjusted by changing the driving frequency, driving voltage and phase of the MEMS.

[0017] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) By changing the driving frequency and voltage of the frequency driving device of the frequency sweeping light source module and calibrating the phase, the signal duty cycle of the output light source is reduced, thereby narrowing the pulse width and outputting ultra-short pulses; the frequency selection device is regulated to improve the linearity of the frequency sweeping light source and avoid the distortion problem of the frequency sweeping signal caused by multiple buffer levels; (2) After reducing the signal duty cycle, the sweep rate is multiplied by an optical separation-delay-coupling device to achieve a doubling of the sweep rate; (3) By introducing monitoring feedback devices and other means to monitor and control stability, the stable output of the swept frequency light source can be achieved.

[0018] In summary, the present invention significantly improves the performance of the swept frequency light source through duty cycle modulation and sweep rate multiplication technology, while enhancing the stability and flexibility of the system, meeting the needs of high-precision and high-efficiency detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure is a schematic structural diagram of a swept frequency light source system based on duty cycle modulation and sweep rate multiplication according to an embodiment of the present invention.

[0020] Figure 2 Schematic diagrams of a light buffer stage device provided according to an embodiment of the present invention, respectively, are a single buffer stage structure and a multi-buffer stage structure.

[0021] Figure 3It is a waveform principle diagram of a frequency selection device provided according to an embodiment of the present invention.

[0022] Figure 4 1 is a schematic diagram of the principle of duty cycle modulation and adding a buffer stage device to multiply the sweep rate according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, identical modules are denoted by identical reference numerals. In the case of identical reference numerals, their names and functions are also identical. Therefore, their detailed description will not be repeated.

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0025] The present invention provides a frequency sweeping light source system based on duty cycle modulation and frequency sweeping rate multiplication ( Figure 1 ), including: a swept light source module, a signal generating device, an optical separation-delay-coupling device, a temperature control module and a monitoring feedback module; A signal generating device is a device that provides a periodic electrical signal, including but not limited to a signal generator, a circuit modulation device of a semiconductor optical amplifier (SOA), etc.; The swept frequency light source module is a unidirectional frequency scanning device with frequency tuning function. It selects wavelength by tuning the internal frequency drive or frequency resonance, changes the resonant frequency, and adjusts the voltage and phase to reduce the duty cycle of the output light source signal. It includes a tunable light source, a frequency tuning device, and a frequency selection device. A tunable light source is used to provide basic optical signal output; preferably, the tunable light source is an FDML laser, a MEMS grating external cavity swept laser, a MEMS-VCSEL, etc.; Frequency tuning device, used to control the frequency change of the light source to achieve wavelength scanning; A frequency selection device for selecting an optical signal of a specific wavelength to ensure that the wavelength of the output optical signal meets the requirements; preferably, the frequency selection device is a Fabry-Perot filter (FFP-TP) used in an FDML laser, or an external cavity grating in a MEMS grating external cavity swept light source, or an air gap under MEMS modulation in a MEMS-VCSEL swept light source; The output optical signal of the tunable light source is wavelength-selected by a frequency selection device; the driving control signal generated by the signal generating device is sent to the frequency tuning device of the frequency-sweeping light source module to achieve frequency tuning; the optical signal selected by the frequency selection device serves as the final output of the frequency-sweeping light source module.

[0026] The optical separation-delay-coupling device is connected to the swept-frequency light source module and is used to perform time delay and signal replication on the swept-frequency light source. In a specific embodiment, the optical separation-delay-coupling device is an optical buffer stage device (Optical Buffer Stage); Figure 2 A shows a single buffer level structure, and B shows a multi-buffer level structure; The optical separation-delay-coupling device comprises a separation unit, a delay unit and a coupling unit; The separation unit is used to split the frequency-sweep optical signal into two optical signals without changing the original properties of the signal, including but not limited to a wavelength division multiplexer, a coupler, etc.; The delay unit is used to delay one of the optical signals in time without changing the waveform and other inherent properties, including but not limited to single-mode optical fiber; The coupling unit is used to combine two optical signals into one beam, including but not limited to an optical coupler; Furthermore, the optical separation-delay-coupling device can be used without limit on the number of times, and the light wave of the frequency-sweeping light source can be replicated multiple times, thereby achieving an exponential growth in the frequency-sweeping rate.

[0027] The temperature control module is connected to the swept light source module to adjust and maintain the working environment temperature of the swept light source module; the temperature control module can effectively reduce the impact of temperature changes on optical performance and ensure the stability and accuracy of the system; preferably, the temperature control module is a heater, a cooler, a thermocouple, etc.

[0028] The two ends of the monitoring and feedback module are respectively connected to the temperature control module and the frequency sweeping light source module, and are used to monitor the stability of the light source in real time and determine whether the temperature control module needs to be adjusted based on the monitored light source performance data; if adjustment is required, the monitoring and feedback module will send an adjustment instruction to the temperature control module; specifically, the input end of the monitoring and feedback module is connected to the output end of the frequency sweeping light source module to obtain the output light signal of the light source in real time; the output end of the monitoring and feedback module is connected to the control input end of the temperature control module for sending adjustment instructions; In a specific embodiment, the monitoring and feedback module includes an algorithm unit and a control unit; the algorithm unit is used to analyze and process the monitored light source performance data to determine whether the temperature control module needs to be adjusted; if fluctuations or deviations in the light source performance are detected, the control unit of the monitoring and feedback module sends adjustment instructions to the signal generating device and the temperature control module, adjusts the frequency, waveform, duty cycle and other parameters of the signal generating device according to the instructions, and adjusts the temperature control module to stabilize the working environment temperature to maintain the stability and accuracy of the system.

[0029] Specifically, in a swept-frequency light source module: the output optical signal of the tunable light source is wavelength-selected by a frequency selection device; for example, in an FDML laser, the output optical signal of the laser is wavelength-selected by a Fabry-Perot filter (FFP-TP); in a MEMS grating external cavity swept-frequency light source, the output optical signal of the laser is wavelength-selected by an external cavity grating; in a MEMS-VCSEL, the optical signal output by the laser is wavelength-selected by an air gap under MEMS modulation; The drive control signal (e.g., a sinusoidal signal) generated by the signal generator is fed into the frequency tuning device to control its operating state, thereby achieving frequency tuning. For example, wavelength selection can be achieved by adjusting the filter's transmission spectrum by changing the frequency, amplitude, and offset of the sinusoidal signal applied to the Fabry-Perot filter (FFP-TP). Alternatively, different wavelengths can be selected by controlling the vibration angle of the MEMS galvanometer. Alternatively, wavelength selection can be achieved by modulating the MEMS to control the air gap within the VCSEL. The swept frequency light source module can also include an auxiliary adjustment device, which is used to fine-tune the frequency tuning device or the frequency selection device to optimize the swept frequency performance; for example, the manual fine adjustment of the six-axis device is used to adjust the position of the MEMS galvanometer to ensure that the central wavelength is aligned with the zero point position of the sine wave function, thereby increasing the swept frequency rate and reducing signal distortion caused by dispersion.

[0030] In a specific embodiment, the swept-frequency light source module uses a Fourier Domain Mode-Locking (FDML) laser as an example. The laser achieves wavelength selection and tuning through a Fabry-Perot filter (FFP-TP). By varying the distance between the fiber end faces, the cavity length is changed, thereby adjusting the filter's transmission spectrum to achieve wavelength selection. Specifically, a sinusoidal signal is applied to the FFP-TP, and the frequency, amplitude, and offset of the modulation signal are varied to adjust the center wavelength and sweep range of the swept-frequency light source. Because the frequency of the drive control signal is limited by the filter's inherent resonant frequency, significantly increasing the sweep rate requires reducing the signal duty cycle and then multiplying the sweep rate through a buffer stage. Applying a sinusoidal signal to the SOA reduces the duty cycle of the output signal by adjusting the sine wave signal's duty cycle. Simultaneously, the amplitude of the applied sine wave function can be adjusted to a certain extent to increase the amplitude of the sine wave function, further reducing the signal duty cycle. Furthermore, the zero point position of the sine wave function can be calibrated by adjusting the phase of the signal generator.

[0031] In a specific embodiment, the swept-frequency light source module uses a microelectromechanical system (MEMS) grating external cavity swept-frequency light source as an example. The basic principle of a swept-frequency laser is to use an external cavity grating for wavelength selection, control the grating's rotation via MEMS, and select the wavelength using different grating angles, thereby achieving the output of a swept-frequency light source. For the MEMS galvanometer, its vibration rate can still be viewed as a sine wave function. Increasing the galvanometer's vibration angle is equivalent to increasing the amplitude of the sine wave function, thereby reducing the signal duty cycle. At the same time, by manually fine-tuning the galvanometer's position along six axes and aligning the central wavelength with the zero point of the sine wave function, the sweep rate can be maximized while minimizing the problem of swept-frequency signal distortion caused by subsequent dispersion.

[0032] In a specific embodiment, the swept-frequency light source module uses a microelectromechanical system-vertical cavity surface emitting laser (MEMS-VCSEL) as an example. A MEMS-VCSEL is a swept-frequency light source that uses a MEMS-assisted method to change the VCSEL cavity length, thereby achieving tuning. The electrostatic force generated by the applied voltage deflects the MEMS cantilever, changing the air gap height, and thus the effective cavity length of the VCSEL, achieving a swept-frequency light source with tunable output wavelength. The signal duty cycle modulation and sweep rate multiplication principle is similarly achieved by varying the MEMS drive frequency, drive voltage, and phase to adjust the duty cycle, and then multiplying the sweep rate through a fiber buffer stage.

[0033] The swept frequency light source module is a waveform time repetition device for unidirectional frequency scanning. The swept frequency light source with a frequency tuning device selects the wavelength through the frequency drive or frequency resonance inside or outside the tuning device. It is manifested by changing the resonant frequency of the device itself or introducing a frequency control device, while adjusting the voltage and the duty cycle of the modulation signal to achieve the purpose of reducing the duty cycle of the output light source signal; further, by adjusting the phase, offset or manually adjusting the position angle of the frequency selection device to calibrate the center position of the signal wave of the center wavelength, avoiding the distortion of the swept frequency signal caused by the dispersion of the long fiber after adding the fiber buffer stage. The specific principle is as follows Figure 3 As shown, it is obvious that the sweep time required for one cycle after increasing the waveform amplitude is less than the original sweep time, and the central wavelength is aligned with the origin of the vibration waveform of the frequency selection device, and its rate is the slope of the sine wave, that is, the origin is the point with the fastest sweep rate.

[0034] For a sweep cycle, the sweep signal is adjusted to control its duty cycle below 50%, 25%, and 12.5% respectively. The sine wave signal is modulated to 1 / 2, 1 / 4, and 1 / 8 of the original, and the sweep signal is copied into 2, 4, and 8 parts respectively through the buffer level structure, as shown in the following example: Figure 4As shown in the figure, the sweep rate is 2, 4, and 8 times the original sweep rate, respectively, achieving an exponential increase in the sweep rate. At the same time, when the sweep signal after duty cycle modulation is continuously compressed to near the origin of the sine wave function, its linearity will be better, and the output of the swept light source will be more uniform and stable.

[0035] For the above system, a modulation method of a swept frequency light source system based on duty cycle modulation and sweep rate multiplication is provided, which specifically includes the following steps: S1. Initialize the system: Start the swept light source module, adjust the temperature control module, and adjust the working environment temperature of the swept light source module to a preset stable range; Specifically, start the swept-frequency light source module to ensure that it is in normal working condition; check whether the signal generating device, optical separation-delay-coupling device, temperature control module and monitoring feedback module are connected normally and in standby state; adjust the temperature control module to adjust the working environment temperature of the swept-frequency light source module to a preset stable range to reduce the impact of temperature changes on optical performance.

[0036] S2. Modulate the duty cycle of the swept-frequency signal output by the swept-frequency light source module: Based on the target application requirements, a periodic electrical signal is input to the frequency tuning device of the swept-frequency light source module through the signal generating device to adjust the driving frequency of the frequency driving device; the resonant wave amplitude and the central wavelength position of the frequency selecting device are adjusted by increasing the voltage, phase, and offset of the frequency selecting device to reduce the signal duty cycle. For FDML lasers, the distance between the fiber end faces in the Fabry-Perot filter (FFP-TP) is changed by changing the driving voltage, that is, the voltage, phase and modulation signal duty cycle of the Fabry-Perot cavity are changed, thereby reducing the signal duty cycle of the swept light source; For MEMS grating external cavity swept light source, the wavelength is selected by rotating the external cavity grating to control the grating angle, thereby achieving the output of the swept light source; by increasing the vibration angle of the galvanometer, the amplitude of the sine wave function is increased and the duty cycle of the signal is reduced; For MEMS-VCSEL, wavelength selection is achieved by changing the effective cavity length of the VCSEL by changing the loading voltage; duty cycle adjustment is achieved by changing the driving frequency, driving voltage and phase of the MEMS.

[0037] S3 achieves sweep rate doubling of the sweep signal: After completing the duty cycle modulation, the optical signal output by the sweep light source module is introduced into the optical separation - delay - coupling device to achieve sweep rate doubling of the sweep signal; The sweeping optical signal is separated into two parts by a separation unit of an optical separation device without changing the original properties of the signal; a delay unit is used to time-delay one of the optical signals without changing other inherent properties such as the waveform; and finally, a coupling unit is used to combine the two optical signals into one beam, thereby doubling the sweeping rate of the sweeping signal and thus exponentially increasing the sweeping rate.

[0038] If the frequency sweep rate needs to be further increased, the optical separation-delay-coupling device can be used multiple times to replicate the light waves of the frequency sweep light source, thereby achieving an exponential increase in the frequency sweep rate.

[0039] S4. Stability monitoring and feedback adjustment: Start the monitoring feedback module to monitor the stability of the light source in real time and obtain the output light signal of the light source; determine whether the temperature control module needs to be adjusted based on the monitored light source performance data; The algorithm unit of the monitoring and feedback module analyzes and processes the monitored light source performance data to determine whether the temperature control module needs to be adjusted. If the monitored light source performance fluctuates or deviates, the control unit of the monitoring and feedback module sends adjustment instructions to the signal generator and the temperature control module. According to the instructions, the frequency, waveform, duty cycle and other parameters of the signal generator are adjusted, and the temperature control module is adjusted to stabilize the working environment temperature to maintain the stability and accuracy of the system. At the same time, the monitoring feedback module can also monitor other key components such as the optical separation-delay-coupling device to ensure the stable operation of the entire system and achieve stable output of high-speed sweep frequency signals.

[0040] S5. System optimization and adjustment: Based on the monitoring feedback, fine-tune and optimize the various system parameters, such as further adjusting the driving frequency of the frequency drive device, the waveform amplitude and position of the frequency selection device, and the delay time of the optical delay device, to achieve the best frequency scanning performance and stability.

[0041] In addition, the system should be maintained regularly to check the connection and working status of each component to ensure the long-term stable operation of the system.

[0042] Through the above-mentioned modulation method, the present invention creates a device that can effectively reduce the signal duty cycle of the swept frequency light source, and achieve the output of a high-sweep frequency rate signal by multiplying the sweep frequency rate. At the same time, with the help of a monitoring feedback device, the stable output of the signal is achieved, meeting the needs of non-destructive testing equipment in fields such as biomedicine and manufacturing for high-speed swept frequency light sources.

[0043] The present invention aims to provide a high-speed frequency sweeping light source system, which reduces the duty cycle by adjusting the tuning frequency, voltage, and duty cycle of the modulation signal of the frequency sweeping light source, and further reduces the duty cycle and avoids subsequent frequency sweeping signal distortion by adjusting the phase, offset, or manually adjusting the position angle of the frequency selection device to calibrate the center point of the tuning device; then, an optical separation device, an optical delay device, and an optical coupling device are connected outside the cavity to multiply the frequency sweeping rate, thereby increasing the frequency sweeping rate exponentially; further, a monitoring feedback device is introduced to perform positive feedback regulation to achieve stable output of high-speed frequency sweeping signals. Key technical points include but are not limited to the following aspects: (1) Designed for a frequency sweeping light source with a frequency driving device, the signal duty cycle of the frequency sweeping light source is reduced by adjusting the driving frequency of the frequency driving device. (2) The signal duty cycle is further reduced and the subsequent stability of the frequency sweeping signal is maintained by performing waveform amplitude enhancement and position correction on the frequency selection device, thereby avoiding frequency sweeping signal distortion caused by multiple buffer levels. (3) Under the premise of reducing the signal duty cycle, the sweep rate of the sweep signal is multiplied through the optical separation-delay-coupling device to achieve the output of a high sweep rate signal. (4) It has a monitoring feedback device that can perform positive feedback adjustment to eliminate the interference of internal and external unstable factors and achieve stable output of high-speed sweep signals. Its main advantages are: 1. Significantly improve the sweep rate: By adjusting the driving frequency, voltage, phase, etc. of the frequency driving device to reduce the signal duty cycle, and using an optical separation-delay-coupling device to multiply the signal sweep rate, the sweep rate is increased exponentially, meeting the demand for high sweep rates in fields such as biomedical imaging (such as OCT systems) and non-destructive testing in manufacturing.

[0044] 2. Optimize signal quality: (1) Reduce signal duty cycle: By adjusting the voltage and phase of the frequency driving device, the resonant wave amplitude of the frequency selection device is increased and the central wavelength position of the frequency selection device is calibrated to further reduce the signal duty cycle, thereby narrowing the pulse width, outputting ultra-short pulses, and improving the resolution and accuracy of the signal; (2) Avoid signal distortion: Through precise waveform amplitude enhancement and position correction, the distortion problem of the swept frequency signal caused by multiple buffer levels is avoided, ensuring the stability and consistency of the signal; (3) Improve linearity: Due to the modulation of the duty cycle, the swept frequency signal is continuously compressed to the vicinity of the origin of the sine wave function, its linearity is improved, and the output of the swept frequency light source is more uniform and stable.

[0045] 3. Enhanced system stability: A monitoring feedback device is introduced to monitor the stability of the light source in real time. Through positive feedback regulation, interference from internal and external unstable factors is eliminated, achieving stable output of high-speed sweep signals. Environmental stabilization devices such as temperature control devices are used to regulate the operating environment of the sweep light source, reducing the impact of external factors such as temperature changes on optical performance, further improving system stability.

[0046] 4. Flexibility and Scalability: The optical separation-delay-coupling device can be used an unlimited number of times, enabling multiple replications of the swept-source lightwave, achieving exponential growth in the sweep rate and meeting the diverse sweep rate requirements of different application scenarios. Strong Compatibility: The present invention is applicable to a variety of swept-source types, such as FDML lasers, MEMS grating external cavity swept-sources, and MEMS-VCSELs, demonstrating broad applicability and compatibility.

[0047] 5. Improve system performance: A power amplifier can be connected to amplify the signal, further improving system performance and meeting high-power application scenarios. By controlling and modulating the waveform using a periodic signal source, precise control of the swept light source can be achieved, improving overall system performance.

[0048] 6. Economic benefits: By optimizing the performance of the swept-frequency light source, the detection efficiency and imaging quality are improved, the detection time and cost are reduced, and the economic benefits and market competitiveness of the equipment are improved.

[0049] 7. Wide range of applications: This invention is applicable to multiple fields such as biomedical imaging (such as optical coherence tomography (OCT), industrial non-destructive testing, and optical communications, and has broad application prospects and practical application value.

[0050] In summary, the present invention significantly improves the performance of the swept frequency light source through duty cycle modulation and sweep rate multiplication technology, while enhancing the stability and flexibility of the system, meeting the needs of high-precision and high-efficiency detection.

[0051] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved. This is not limited herein.

[0052] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A swept frequency light source system based on duty cycle modulation and sweep rate multiplication, characterized by: It includes a frequency sweep light source module, a signal generating device, an optical separation-delay-coupling device, a temperature control module and a monitoring feedback module; The frequency-sweeping light source module is used to provide a unidirectional frequency-sweeping optical signal with a frequency tuning function. It performs wavelength scanning by tuning the internal frequency drive or frequency resonance, changes the resonant frequency, and reduces the duty cycle of the output light source signal. The driving control signal generated by the signal generating device is sent to the frequency tuning device of the frequency sweeping light source module to achieve frequency tuning; The optical separation-delay-coupling device is connected to the swept-frequency light source module to perform time delay and signal replication on the swept-frequency light source; The temperature control module is connected to the frequency sweeping light source module to adjust and maintain the working environment temperature of the frequency sweeping light source module; The two ends of the monitoring feedback module are connected to the temperature control module and the signal generating device respectively, which are used to monitor the stability of the light source in real time and determine whether the signal generating device and the temperature control module need to be adjusted based on the monitored light source performance data.

2. The swept frequency light source system based on duty cycle modulation and sweep rate multiplication according to claim 1, characterized in that: The frequency sweeping light source module includes a tunable light source, a frequency tuning device and a frequency selection device; A tunable light source is used to provide basic optical signal output; a frequency tuning device is used to control the frequency change of the light source to achieve wavelength scanning; a frequency selection device is used to select an optical signal of a specific wavelength to ensure that the wavelength of the output optical signal meets the requirements; the signal duty cycle is reduced by increasing the resonant wave amplitude of the frequency selection device and calibrating the center wavelength position of the frequency selection device.

3. The swept frequency light source system based on duty cycle modulation and sweep rate multiplication according to claim 2, characterized in that: The optical separation-delay-coupling device is a light buffer stage device; the signal generating device is a semiconductor optical amplifier; the tunable light source is an FDML laser; and the frequency selection device is a Fabry-Perot filter used in the FDML laser. By changing the distance between the fiber end faces of the Fabry-Perot filter, the cavity length is changed, thereby adjusting the filter's transmission spectrum and achieving wavelength selection. By applying a sinusoidal signal to the Fabry-Perot filter and changing the frequency, amplitude, and offset of the modulation signal, the center wavelength and sweep range of the swept light source can be adjusted. A sinusoidal wave signal is applied to a semiconductor optical amplifier, and the duty cycle of the output signal is reduced by adjusting the duty cycle of the sinusoidal wave signal.

4. The swept frequency light source system based on duty cycle modulation and sweep rate multiplication according to claim 2, characterized in that: The tunable light source is a MEMS grating external cavity swept laser; the frequency selection device is an external cavity grating in the MEMS grating external cavity swept light source; By rotating the external cavity grating to control the grating angle, the wavelength is selected to achieve the output of the swept light source; by increasing the vibration angle of the galvanometer, the amplitude of the sine wave function is increased and the duty cycle of the signal is reduced.

5. The swept frequency light source system based on duty cycle modulation and sweep rate multiplication according to claim 2, characterized in that: The tunable light source is a MEMS-VCSEL swept-frequency laser; the frequency selection device is an air gap in the VCSEL cavity modulated by the MEMS in the MEMS-VCSEL swept-frequency light source; By applying voltage to generate electrostatic force, the MEMS cantilever is deflected, the air gap height is changed, and then the effective cavity length of the VCSEL is changed, wavelength tuning is achieved, and a swept light source is output; the duty cycle is adjusted by changing the driving frequency and driving voltage of the MEMS to reduce the duty cycle of the signal.

6. The swept frequency light source system based on duty cycle modulation and sweep rate multiplication according to claim 2, characterized in that: The optical separation-delay-coupling device comprises: The separation unit is used to separate the frequency-sweeping optical signal into two optical signals without changing the original properties of the signals, and the separation unit includes a wavelength division multiplexer or a coupler; The delay unit is used to delay one of the optical signals in time without changing other inherent properties, and the delay unit includes a single-mode optical fiber; The coupling unit is used to combine two optical signals into one beam; the coupling unit includes an optical coupler.

7. The swept frequency light source system based on duty cycle modulation and sweep rate multiplication according to claim 1, characterized in that: The optical separation-delay-coupling device can be used more than once, and the exponential growth of the frequency sweep rate can be achieved by replicating the light wave of the frequency sweep light source multiple times; The temperature control module is at least one of a heater, a refrigerator, and a thermocouple.

8. A modulation method for a swept-frequency light source system based on duty cycle modulation and sweep rate multiplication, comprising performing duty cycle modulation on the swept-frequency light source system based on duty cycle modulation and sweep rate multiplication according to claim 1; characterized in that: The specific steps include: S1. Initialize the system: Start the swept light source module, adjust the temperature control module, and adjust the working environment temperature of the swept light source module to a preset stable range; S2. Input a periodic electrical signal to the frequency tuning device of the swept light source module through a signal generating device to adjust the driving frequency of the frequency driving device; by increasing the resonant wave amplitude of the frequency selection device and calibrating the center wavelength position of the frequency selection device, thereby reducing the signal duty cycle; S3. After the duty cycle modulation is completed, the optical signal output by the swept light source module is introduced into the optical separation - delay - coupling device to achieve a doubling of the sweep rate of the swept signal; S4 starts the monitoring feedback module, monitors the stability of the light source in real time, and obtains the output light signal of the light source; determines whether the signal generating device and the temperature control module need to be adjusted according to the monitored light source performance data; S5. Based on the monitoring feedback, fine-tune and optimize the system parameters to ensure the sweep performance and stability.

9. The modulation method of a swept frequency light source system based on duty cycle modulation and sweep rate multiplication according to claim 8, characterized in that: The monitoring feedback module includes an algorithm unit and a control unit; the algorithm unit is used to analyze and process the monitored light source performance data to determine whether the signal generating device and the temperature control module need to be adjusted; if the monitored light source performance fluctuates or deviates, the control unit sends an adjustment instruction to the signal generating device and the temperature control module, adjusts the frequency, waveform, duty cycle and other parameters of the signal generating device according to the instruction, and adjusts the temperature control module to stabilize the working environment temperature to maintain the stability and accuracy of the system.

10. The modulation method of a swept frequency light source system based on duty cycle modulation and sweep rate multiplication according to claim 8, characterized in that: The frequency selection device in step S2 is a Fabry-Perot filter used in an FDML laser. The cavity length is changed by changing the distance between the fiber end faces of the Fabry-Perot filter, thereby adjusting the transmission spectrum of the filter and achieving wavelength selection. The central wavelength and the sweep range of the swept frequency light source are adjusted by applying a sinusoidal wave signal to the Fabry-Perot filter and changing the frequency, amplitude and offset of the modulation signal. Alternatively, the frequency selection device in step S2 is an external cavity grating in a MEMS grating external cavity swept frequency light source; the wavelength is selected by rotating the external cavity grating to control the grating angle, thereby realizing the output of the swept frequency light source; and the amplitude of the sine wave function is increased by increasing the vibration angle of the galvanometer, thereby reducing the duty cycle of the signal; Alternatively, the frequency selection device in step S2 is an air gap under MEMS modulation in a MEMS-VCSEL; an electrostatic force is generated by applying a voltage to the MEMS to deflect the MEMS cantilever, thereby changing the air gap height and thereby changing the effective cavity length of the VCSEL, thereby realizing a swept-frequency light source with adjustable output wavelength; and the duty cycle is adjusted by changing the driving frequency, driving voltage and phase of the MEMS.

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