High repetition frequency optical frequency comb mode locking detection method and system

Abstract

The invention provides a high repetition frequency optical frequency comb mode locking detection method and system. The method comprises the following steps: calculating an optical frequency comb repetition frequency theoretical value according to an optical frequency comb optical system cavity length; pump light is injected into an optical frequency comb optical system, output light converts an optical signal into an electric signal through a photoelectric detector, the electric signal filters out an optical frequency comb repetition frequency fundamental frequency signal through a band-pass amplifier and amplifies the optical frequency comb repetition frequency fundamental frequency signal, then the optical frequency comb repetition frequency fundamental frequency signal is subjected to frequency reduction to a KHz magnitude through a frequency division amplification signal processing unit, and then the optical frequency comb repetition frequency fundamental frequency signal enters an analog-to-digital converter; the current frequency division series and frequency division ratio of the frequency division amplification signal processing unit are determined by the microcontroller according to the optical frequency carding theory repetition frequency theoretical value; the microcontroller processes the signals collected by the analog-to-digital converter to obtain frequency spectrum information, if the fluctuation of the intensity corresponding to a frequency point in the frequency spectrum information within a certain time period is larger than a set threshold value, the optical frequency comb does not lock the mode, and if the fluctuation is not larger than the set threshold value, the optical frequency comb completes mode locking. According to the invention, the mode locking state of the high repetition frequency optical frequency comb can be accurately detected.

Description

Technical Field

[0001] This invention relates to the field of ultrafast optics technology, specifically to a method and system for detecting mode-locking of a high repetition frequency optical comb. Background Technology

[0002] As a core bridge connecting optical frequency standards and microwave frequency standards, optical frequency combs have significant advantages such as simple structure and low cost. Their comb-shaped spectral characteristics enable high-precision measurement of absolute optical frequency, providing a revolutionary tool for time and frequency transmission, absolute distance and angle measurement. In fields such as manned spaceflight, deep space exploration, satellite timing and modern manufacturing, optical frequency combs effectively improve the accuracy of parameter measurement and system integration in complex scenarios through multi-channel parallel measurement and phase synchronization technology, becoming a key technical support for precision metrology and engineering applications.

[0003] Currently, optical frequency combs mainly include three types: fiber optic frequency combs, electro-optical combs, and microcavity optical combs. Among them, electro-optical combs and microcavity optical combs generally have repetition frequencies in the GHz range, which are considered high repetition frequencies. For optical frequency combs to be truly applied in engineering, stable mode-locking of their oscillators is a primary prerequisite. In the mode-locked state, the repetition frequency of the optical frequency comb and the phase frequency of the carrier envelope must be strictly locked to ensure the absolute stability of the comb tooth frequency. However, the mode-locking process is extremely susceptible to interference from external environmental conditions. Changes in ambient temperature or mechanical vibration can cause deformation of the mechanical structure, optical fiber, lens frame, and other optical components in the optical frequency comb system. This not only reduces the coupling efficiency of the optical system but also increases the mode-locking threshold of the pump current. At the same time, the mode-locking threshold of the pump current varies under different environmental conditions. Traditional fixed pump threshold control methods cannot guarantee mode-locking stability, and the adaptability of the pump current also directly affects the mode-locking quality, which may even lead to mode-locking failure in severe cases.

[0004] Currently, the determination of the mode-locking status of optical frequency combs mainly includes optical and electrical methods. Optical methods directly measure spectral changes during the mode-locking process using a spectrometer, with spectral broadening and flattening as a characteristic of mode-locking completion. However, this method relies on offline measurement equipment and cannot achieve real-time online monitoring. Electrical methods mainly reflect the mode-locking status by measuring parameters related to the repetition frequency of the optical frequency comb. This is commonly achieved using devices such as frequency counters and spectrum analyzers. Although it has a certain degree of real-time capability, existing measurement equipment has limitations in high-frequency signal processing accuracy for optical frequency combs with high repetition frequencies of hundreds of MHz or even GHz. Furthermore, although there are reports of using microcontrollers to control peak detectors for judgment, the peak detection module has inherent bandwidth limitations and cannot accurately detect the mode-locking status of high-repetition-frequency optical frequency combs, which can easily lead to misjudgments.

[0005] More importantly, current optical frequency comb technology is rapidly developing towards higher repetition rates, wider spectral ranges, and miniaturization and integration. The miniaturization and real-time operation of high repetition rate optical frequency comb mode-locking judgment systems have become necessary development directions. However, existing mode-locking judgment methods all have their own technical bottlenecks and cannot meet the needs of engineering applications on their own. At the same time, optical frequency combs can only perform nonlinear transformations such as amplification, spectral expansion, and frequency doubling after mode-locking is completed; otherwise, irreversible damage to the system will occur. Existing measuring instruments can only feed back the mode-locking judgment results to the operator and cannot form a real-time linkage with the optical frequency comb pump circuit. When the optical frequency comb loses mode-locking due to external environmental interference, it cannot trigger the pump circuit to shut down or adjust parameters in time, which can easily damage the entire optical frequency comb system and seriously restrict the promotion and application of optical frequency combs in engineering scenarios. Summary of the Invention

[0006] In view of this, the present invention provides a mode-locking detection method and system for high repetition frequency optical combs, which can accurately detect the mode-locking state of high repetition frequency optical combs.

[0007] The technical solution adopted in this invention is as follows: A method for detecting mode-locking of a high repetition frequency optical comb, which calculates the theoretical value of the repetition frequency of the optical comb based on the cavity length of the optical comb's optical system; Pump light is injected into the optical frequency comb system. The output light is converted into an electrical signal by a photodetector. The electrical signal is filtered out by a bandpass amplifier to extract the fundamental frequency signal of the optical frequency comb repetition frequency and amplified. Then, it is down-frequencyd to the KHz level by a frequency divider and amplification signal processing unit before entering the analog-to-digital converter. The current division level and division ratio of the frequency division amplification signal processing unit are determined by the microcontroller based on the theoretical value of the optical frequency comb's theoretical repetition frequency. The microcontroller processes the signal acquired by the analog-to-digital converter to obtain spectrum information. If the intensity of the frequency point in the spectrum fluctuates within a certain time period, the optical frequency comb is not mode-locked; if it does not exceed the set threshold, the optical frequency comb is mode-locked.

[0008] Furthermore, the frequency division amplification signal processing unit includes two or more frequency dividers and amplifiers, with the number of frequency dividers and amplifiers being the same, and one frequency divider and one amplifier constituting one unit.

[0009] Furthermore, the microcontroller controls the frequency division amplification signal processing unit through the frequency division amplification management unit.

[0010] Furthermore, the frequency divider amplification management unit is an RF switch, which manages the number of stages of the currently selected frequency divider and amplifier by controlling the on / off state of the RF switch.

[0011] Furthermore, the system's mode-locking status detection result is output through logic levels, where 0 indicates no mode-locking and 1 indicates mode-locking.

[0012] Furthermore, after the initial detection of mode-locking, the microcontroller continues to process the signals acquired by the analog-to-digital converter to continuously determine whether the optical frequency comb is truly mode-locked.

[0013] Furthermore, pump light is injected into the optical frequency comb optical system through the pump source circuit; When the pump source circuit increases to the maximum output power, if the intensity extracted by the microcontroller still fluctuates more than the set threshold within a certain period of time, then the optical frequency comb is not mode-locked.

[0014] Furthermore, when the optical frequency comb loses its mode-locked state, the microcontroller detects this by judging the change in the spectrum information and inputs this result to the pump source circuit through a logic level, and the pump source circuit shuts down the pump light.

[0015] Furthermore, the system mode-locking status detection result is indicated by an indicator light: not mode-locked displays the first designated color; mode-locked displays the second designated color; if the optical frequency comb optical system is malfunctioning, the indicator light flashes alternately between the first and second designated colors.

[0016] The present invention also provides a high repetition rate optical comb mode-lock detection system, including an optical comb optical system, a photodetector, a bandpass amplifier, a frequency divider amplification signal processing unit, an analog-to-digital converter, and a microcontroller; The optical frequency comb optical system is used to receive pump light to complete mode locking; the photodetector is used to convert the optical signal of the output light of the optical frequency comb optical system into an electrical signal; the bandpass amplifier is used to filter out the fundamental frequency signal of the optical frequency comb repetition frequency from the electrical signal and amplify it. The frequency division amplification signal processing unit is used to down-frequency the amplified optical frequency comb repetition frequency base frequency signal to the KHz level; The analog-to-digital converter is used to acquire the down-frequency fundamental frequency signal of the optical frequency comb repetition frequency and send it to the microprocessor; The microcontroller is used to determine the current division level and division ratio of the frequency division amplification signal processing unit based on the theoretical value of the optical frequency comb's theoretical repetition frequency; and to process the signal collected by the analog-to-digital converter to obtain spectrum information. If the intensity of the frequency point in the spectrum information fluctuates within a certain time period, the optical frequency comb is not mode-locked; if it does not exceed the set threshold, the optical frequency comb is mode-locked.

[0017] Beneficial effects: 1. The microprocessor of this invention performs calculation and processing on the signals collected by the analog-to-digital converter. The processed object is a digital signal that is independent of clock stability and can detect the mode-locking state of an optical frequency comb system with a repetition frequency value as high as 3GHz.

[0018] Furthermore, depending on the repetition frequency of the optical frequency comb, the microcontroller controls the frequency division amplification management unit to achieve frequency division and frequency division amplification stage control, so as to adapt to different repetition frequencies and different optical frequency comb systems for mode-locked detection. In addition, the microcontroller strictly sets the frequency division ratio of the frequency division amplification signal processing unit according to the theoretical value of the optical frequency comb's theoretical repetition frequency, which can improve the signal-to-noise ratio of the optical frequency comb's repetition frequency after frequency division and strictly ensure detection accuracy.

[0019] 2. This invention transforms the detection of the mode-locked state of an optical frequency comb into the detection of spectral information of signals down to the kHz level. The kHz level is typically a low frequency and can be easily achieved using a series of low-cost analog-to-digital converters, greatly reducing the design difficulty of the mode-locked detection scheme. Simultaneously, for different high-repetition-frequency optical frequency comb systems, the final result reduces the high repetition frequency value to the kHz level, significantly reducing signal processing difficulty and increasing processing speed. This allows a single signal processing algorithm to be universally applicable to all current high-repetition-frequency fiber optic frequency comb systems.

[0020] 3. The device used in this invention can be integrated into a single design. Compared with traditional measurement devices such as spectrometers, frequency counters, or spectrum analyzers for detecting the mode-locking state of optical frequency combs, it has the advantages of small system size, high reliability, and the output of the system mode-locking state detection result through logic level, which greatly improves the signal's anti-interference ability, ease of interpretation, and compatibility with digital systems.

[0021] 4. This invention can detect the specific reasons why the optical frequency comb cannot achieve mode locking. Specifically, by detecting the mode locking state and the setting state of the pump source current, it can be determined whether the inability to achieve mode locking is caused by insufficient pump light intensity or by changes in the optical system structure.

[0022] 5. In addition to achieving high-reliability detection of the optical frequency comb's mode-locking status, this invention can also achieve continuous monitoring of the optical frequency comb's mode-locking status. Once the optical frequency comb loses mode-locking due to external environmental factors, the system can transmit the loss of lock status to the pump source circuit via logic level within 1ms. The pump source circuit will then immediately shut down the pump light to prevent damage to the optical frequency comb system and achieve the purpose of protecting the optical frequency comb system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the device structure of the present invention. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] This invention provides a method for detecting mode-locking of a high repetition frequency optical comb, the method being as follows: First, once the optical frequency comb system is assembled, the theoretical range of its repetition frequency values ​​is determined, specifically by the following formula:

[0026] in, v c The speed of light in a vacuum is 299,792,458 m / s. f r The repetition frequency, L This is the laser cavity length of the optical frequency comb system.

[0027] Once the laser cavity length is determined, the microcontroller can calculate the theoretical value of the optical frequency comb repetition frequency using a formula, and record this value as a reference value for the optical frequency comb repetition frequency.

[0028] Next, pump light is injected into the optical frequency comb optical system through the pump source circuit to provide energy for the pulsed laser within the optical frequency comb optical system to perform optical oscillations within the cavity, thereby supporting the optical frequency comb oscillator to complete mode locking. During the process of the pump source circuit injecting pump light into the optical frequency comb optical system, the output light of the optical frequency comb optical system is converted into an electrical signal by a photodetector. The electrical signal is then filtered out by a bandpass amplifier to obtain the fundamental frequency signal of the optical frequency comb repetition frequency, and the signal is amplified to meet the power requirements of subsequent devices such as frequency dividers.

[0029] Then, the fundamental frequency signal of the optical frequency comb repetition frequency after passing through the bandpass amplifier is input to the frequency divider amplification signal processing unit, which performs frequency down-amplification processing on it, reducing it to the KHz level.

[0030] This frequency division and amplification signal processing unit includes two or more frequency dividers and amplifiers, with the number of frequency dividers and amplifiers being the same; one frequency divider and one amplifier constitute one unit. In this embodiment, three frequency dividers and three amplifiers are used. The three frequency dividers are a first-stage frequency divider, a second-stage frequency divider, and a third-stage frequency divider, with basic division ratios of 64, 128, and 256 times, respectively. The amplifiers used have a 3GHz bandwidth and a gain of 24dB, meeting the current design requirements for the repetition frequency of fiber optic frequency combs.

[0031] The frequency divider amplification signal processing unit is controlled by the frequency divider amplification management unit controlled by the microcontroller. The frequency divider amplification management unit is actually an RF switch, which manages the number of stages of the currently selected frequency divider and amplifier by controlling the on / off state of the RF switch.

[0032] The specific number of stages used in the frequency division amplification signal processing unit is as follows: the microcontroller allocates the number of frequency division stages based on the theoretical value of the optical frequency comb repetition frequency, so that the frequency signals output by the frequency division amplification signal processing unit are all reduced to the kHz level before entering the analog-to-digital converter. In this embodiment, the frequency of the optical frequency comb repetition frequency fundamental signal is reduced to below 10kHz, thereby reducing the repetition frequency signal of the high-repetition-frequency optical frequency comb to a low-frequency signal, thus achieving effective detection at a lower cost. The specific selection of the optical frequency comb repetition frequency and the division factor is shown in the table below:

[0033] To enhance the signal-to-noise ratio of the optical frequency comb repetition frequency during the frequency division process, the microcontroller needs to strictly control the number of frequency division stages to achieve reliable mode-locking state judgment.

[0034] Based on the theoretical value of the current optical frequency comb repetition frequency, the microcontroller determines the number of frequency division stages in the frequency division amplification signal processing unit of the current optical frequency comb system. The output signal of the frequency division amplification signal processing unit is acquired by a high-precision analog-to-digital converter. Based on the acquired signal, the following process is used to determine whether mode-locking has been completed: As the pump current increases, mode competition occurs in the optical frequency comb when mode locking is not yet complete within the oscillator cavity of the optical frequency comb system. As a result, the repetition frequency of the optical frequency comb is an unstable signal (fluctuating on the order of hundreds of kHz or even MHz), with large frequency value changes. The low-frequency signal after frequency division also exhibits instability. The analog-to-digital converter acquires the repetition frequency signal of the optical frequency comb after frequency division, converts the analog signal into a digital signal, and the microcontroller performs fast Fourier transform (FFT) signal processing on the digital signal to obtain the spectrum information of the digital signal.

[0035] When the pump current is insufficient, the spectrum of the processed FFT signal is unstable and has large jitter, indicating that the optical frequency comb has not completed mode-locking. As the pump current of the optical frequency comb continues to increase, once mode-locking occurs, the mode inside the optical frequency comb cavity is fixed after mode-locking, and a relatively stable optical frequency comb repetition frequency signal will be generated. At this time, the FFT processing result of the acquired signal will have a stable spectral characteristic, and the amount of spectral change is very small, indicating that the optical frequency comb has completed mode-locking.

[0036] For mode-locked optical frequency combs, the repetition frequency tends to stabilize, typically drifting within the range of Hz or mHz. After signal frequency division, the signal frequency remains essentially unchanged, and the intensity corresponding to each frequency point in the spectral information has also stabilized. In other words, after FFT processing, mode-locked optical frequency combs exhibit two characteristics: firstly, the frequency characteristics stabilize after FFT calculation, remaining essentially unchanged; secondly, the intensity corresponding to each frequency point remains unchanged. Generally, a fluctuation in the intensity corresponding to a frequency point of no more than 5 dBm is considered sufficient to determine that the signal strength is stable, indicating that the optical frequency comb has successfully completed mode-locking.

[0037] Without mode locking, the following situations may occur: First, the intensity becomes unstable, resulting in significant changes in the intensity of the corresponding frequency point after FFT calculation. Second, without mode locking, the repetition frequency jitter will be large, causing jitter and drift in the frequency point position in the frequency domain after FFT calculation, leading to instability. Third, without mode locking, mode competition exists within the optical system cavity of the optical frequency comb. Multiple similar frequency components are generated near the fundamental repetition frequency, resulting in numerous other frequency components near the frequency point position in the frequency domain after FFT calculation, rather than a single frequency point. Therefore, the stability of the intensity corresponding to a frequency point in the spectral information over a certain period can be used to determine whether the optical frequency comb has completed mode locking. If the fluctuation of the intensity corresponding to a frequency point in the spectral information over a certain period exceeds a set threshold, the optical frequency comb is not mode-locked; if it does not exceed the set threshold, the optical frequency comb has completed mode locking. In this embodiment, the set threshold is 5 dBm.

[0038] As an improvement, the system's mode-lock status detection result is output via logic levels, with 0 indicating no mode-lock and 1 indicating mode-lock. Simultaneously, the system's mode-lock status detection result is indicated by an indicator light: no mode-lock displays a first specified color (which can be red); mode-lock displays a second specified color (which can be green); if the optical frequency comb system malfunctions, the indicator light flashes alternately between the first specified color (red) and the second specified color (green). That is, when mode-locked, the mode-lock status indicator light is red, and the output value is 0. When mode-locked, the mode-lock status indicator light turns green, and the output value is 1.

[0039] To improve the accuracy of the judgment results, it is usually necessary to continuously perform FFT processing on the acquired signal after the initial detection of mode locking, and continuously judge whether mode locking is truly achieved, thereby improving the robustness of the detection system. The detection results can be directly output via logic levels, and the output results are fed back to the pump source circuit. Replacing signal communication with logic levels prevents communication errors and improves the reliability of system detection.

[0040] In special circumstances, when the pump source circuit increases to its maximum output power, if the optical frequency comb mode-lock detection system still does not have stable spectral information after signal acquisition, FFT signal processing, and spectral information extraction, it indicates that the system has not detected effective mode-locking. This proves that the optical path coupling of the optical frequency comb optical system has deviated due to environmental temperature, mechanical vibration, etc., and the system's mode-locking status indicator light will flash red and green alternately, prompting the operator to adjust the optical system. When the optical system is properly adjusted, the mode-locking status indicator light will turn green because it has detected that the optical frequency comb optical system has completed mode-locking.

[0041] If the optical frequency comb suddenly loses its mode-locked state due to external environmental factors or accidental touch, the microcontroller will immediately detect the change in the spectrum information and input this result to the pump source circuit through a logic level. The pump source circuit will then immediately shut down the pump light to prevent damage to the optical frequency comb system.

[0042] This invention also provides a high repetition rate optical comb mode-locking detection system, such as... Figure 1 As shown, it includes an optical frequency comb optical system, a photodetector, a bandpass amplifier, a frequency divider amplification signal processing unit, an analog-to-digital converter, and a microcontroller; The optical frequency comb system is used to receive pump light to complete mode locking; Photodetectors are used to convert the optical signal output from an optical frequency comb system into an electrical signal; A bandpass amplifier is used to filter out the fundamental frequency signal of the optical frequency comb repetition frequency from an electrical signal and amplify it; The frequency division amplification signal processing unit is used to down-frequency the amplified optical frequency comb repetition frequency base frequency signal to the KHz level; The analog-to-digital converter is used to acquire the down-frequency fundamental frequency signal of the optical frequency comb and send it to the microprocessor; The microcontroller determines the current division level and division ratio of the frequency division amplification signal processing unit based on the theoretical repetition frequency of the optical frequency comb; it processes the signal acquired by the analog-to-digital converter to obtain spectral information, and determines whether the optical frequency comb has completed mode-locking based on whether the intensity corresponding to the mid-frequency point in the spectral information is stable within a certain time period. If the fluctuation of the intensity corresponding to the mid-frequency point in the spectral information is greater than a set threshold within a certain time period, the optical frequency comb is not mode-locked; if it is not greater than the set threshold, the optical frequency comb has completed mode-locking.

[0043] Furthermore, the automatic mode-locking detection system also includes a pump source circuit, a frequency divider amplifier management unit, and status indicator lights.

[0044] The pump source circuit is used to provide the necessary initial energy input for the laser to generate laser light in the optical frequency comb optical system.

[0045] The frequency divider amplification management unit is used to control the frequency divider amplification signal processing unit under the control of the microcontroller, and to manage the frequency divider and amplifier stages currently selected by the frequency divider amplification signal processing unit.

[0046] The status indicator light is used to indicate the system's mode-locking status detection result: mode-locked, mode-locked, or abnormal. Mode-locked displays the first specified color; mode-locked displays the second specified color; if the optical frequency comb system is abnormal, the indicator light flashes alternately between the first and second specified colors. The first specified color can be red, and the second specified color can be green.

[0047] Based on this high repetition frequency optical comb mode-locking detection system, the above-mentioned detection method can be used to detect the mode-locking status of the high repetition frequency optical comb system, and the judgment result is output in logic level, so the detection result has high reliability.

[0048] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for detecting mode-locking of a high-repetition-frequency optical comb, characterized in that, The theoretical value of the repetition frequency of the optical frequency comb is calculated based on the cavity length of the optical system of the optical frequency comb. Pump light is injected into the optical frequency comb system. The output light is converted into an electrical signal by a photodetector. The electrical signal is filtered out by a bandpass amplifier to extract the fundamental frequency signal of the optical frequency comb repetition frequency and amplified. Then, it is down-frequencyd to the KHz level by a frequency divider and amplification signal processing unit before entering the analog-to-digital converter. The current division level and division ratio of the frequency division amplification signal processing unit are determined by the microcontroller based on the theoretical value of the optical frequency comb's theoretical repetition frequency. The microcontroller processes the signal acquired by the analog-to-digital converter to obtain spectrum information. If the intensity of the frequency point in the spectrum fluctuates within a certain time period, the optical frequency comb is not mode-locked; if it does not exceed the set threshold, the optical frequency comb is mode-locked.

2. The high repetition rate optical comb mode-locking detection method as described in claim 1, characterized in that, The frequency division amplification signal processing unit includes two or more frequency dividers and amplifiers, with the number of frequency dividers and amplifiers being the same. One frequency divider and one amplifier constitute one unit.

3. The high repetition rate optical comb mode-locking detection method as described in claim 1, characterized in that, The microcontroller controls the frequency division amplification signal processing unit through the frequency division amplification management unit.

4. The high repetition rate optical comb mode-locking detection method as described in claim 3, characterized in that, The frequency divider amplifier management unit is an RF switch that controls the on / off state of the RF switch to manage the number of stages of the currently selected frequency divider and amplifier.

5. The high repetition rate optical comb mode-locking detection method according to any one of claims 1-4, characterized in that, The system mode-locking status detection result is output through logic levels, where 0 indicates no mode-locking and 1 indicates mode-locking.

6. The high repetition rate optical comb mode-locking detection method as described in claim 1, characterized in that, After the initial detection of mode-locking, the microcontroller continues to process the signals acquired by the analog-to-digital converter, continuously determining whether the optical frequency comb is truly mode-locked.

7. The high repetition rate optical comb mode-locking detection method as described in claim 5, characterized in that, Pump light is injected into the optical frequency comb system through the pump source circuit; When the pump source circuit increases to the maximum output power, if the intensity extracted by the microcontroller still fluctuates more than the set threshold within a certain period of time, then the optical frequency comb is not mode-locked.

8. The high repetition rate optical comb mode-locking detection method as described in claim 7, characterized in that, When the optical frequency comb loses its mode-locked state, the microcontroller detects this by judging the change in the spectrum information and inputs this result to the pump source circuit through a logic level, and the pump source circuit shuts down the pump light.

9. The high repetition rate optical comb mode-locking detection method as described in claim 5, characterized in that, The system's mode-locking status detection result is indicated by an indicator light: not mode-locked displays the first specified color; mode-locked displays the second specified color; if the optical frequency comb system malfunctions, the indicator light flashes alternately between the first and second specified colors.

10. A high repetition rate optical comb mode-locking detection system, characterized in that, It includes an optical frequency comb system, a photodetector, a bandpass amplifier, a frequency divider amplification signal processing unit, an analog-to-digital converter, and a microcontroller; The optical frequency comb optical system is used to receive pump light to complete mode locking; the photodetector is used to convert the optical signal of the output light of the optical frequency comb optical system into an electrical signal; the bandpass amplifier is used to filter out the fundamental frequency signal of the optical frequency comb repetition frequency from the electrical signal and amplify it. The frequency division amplification signal processing unit is used to down-frequency the amplified optical frequency comb repetition frequency base frequency signal to the KHz level; The analog-to-digital converter is used to acquire the down-frequency fundamental frequency signal of the optical frequency comb repetition frequency and send it to the microprocessor; The microcontroller is used to determine the current division level and division ratio of the frequency division amplification signal processing unit based on the theoretical value of the optical frequency comb's theoretical repetition frequency; and to process the signal collected by the analog-to-digital converter to obtain spectrum information. If the intensity of the frequency point in the spectrum information fluctuates within a certain time period, the optical frequency comb is not mode-locked; if it does not exceed the set threshold, the optical frequency comb is mode-locked.

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