Fiber laser optical path damage detection system and method

Abstract

This application proposes a fiber laser optical path damage detection system and method, relating to the field of fiber laser technology. The system includes: a signal modulation module for injecting a modulation signal into the seed signal light or pump light of the fiber laser, allowing the modulation signal to propagate along the optical path along with the main laser signal; a photodetector, located at the fusion splice or output of the main amplifier in the fiber laser, for converting the optical signal transmitted in the optical path into a detection electrical signal; a demodulation module for demodulating the detection electrical signal through a lock-in amplification mechanism to extract the amplitude information of the modulation signal component; and a processing module for comparing the current amplitude of the modulation signal component with a reference amplitude. When the amplitude attenuation ratio exceeds a preset loss threshold, the system determines that damage exists in the optical path and determines the damage level of the fusion splice based on the amplitude attenuation ratio. This application's solution can detect the leakage intensity at the fusion splice to determine the degree of optical path damage, providing proactive early warning in the early stages of optical path damage.

Description

Technical Field

[0001] This application relates to the field of fiber laser technology, and in particular to a fiber laser optical path damage detection system and method. Background Technology

[0002] As the power of fiber lasers gradually increases, the risk of fiber laser burnout also increases, thus requiring higher reliability. Current solutions typically involve placing photoelectric detection circuits at key monitoring points along the fiber laser's optical path to detect any abnormalities, enabling effective and timely protection. Specifically, the photoelectric detection circuit detects leaked scattered light from the fiber, analyzes abnormal changes in the scattered light intensity, and connects the photoelectric detection signal to a controller for data reading. The controller then determines whether the data falls within the expected normal threshold range, thereby identifying any abnormalities in the laser output.

[0003] However, most existing detection methods are passive, relying solely on monitoring the scattered and reflected light during normal laser operation. This passive detection method can only be detected after an anomaly has occurred and optical path damage has already caused certain consequences, and cannot provide proactive early warning in the early stages of optical path damage. Summary of the Invention

[0004] In view of this, this application proposes a fiber laser optical path damage detection system and method.

[0005] In a first aspect, this application provides a fiber laser optical path damage detection system, including: a signal modulation module, a photodetector, a demodulation module, and a processing module; The signal modulation module is used to inject a modulation signal into the seed signal light or pump light of the fiber laser, so that the modulation signal is transmitted along the optical path together with the main laser signal. The photodetector is located at the fusion splice or output end of the main amplifier in the fiber laser and is used to convert the optical signal transmitted in the optical path into a detection electrical signal. The demodulation module is used to demodulate the detected electrical signal through a lock-in amplification mechanism and extract the amplitude information of the modulated signal component; The processing module is used to compare the current amplitude of the modulated signal component with the reference amplitude. When the amplitude attenuation ratio is greater than the preset loss threshold, it is determined that there is damage to the optical path. The damage level of the optical path is determined according to the amplitude attenuation ratio. The reference amplitude is the amplitude information of the modulated signal component under the standard state of an intact optical path.

[0006] In one embodiment, the processing module is further configured to control the signal modulation module to inject the modulation signal into the seed signal light of the fiber laser when it is determined that a full-optical-path detection operation is to be performed.

[0007] In one embodiment, the processing module is further configured to control the signal modulation module to inject the modulation signal at the pre-pump bias when determining to perform detection work on the pre-pump to detection point optical path.

[0008] In one embodiment, the processing module is further configured to control the signal modulation module to inject the modulation signal at the main amplifier pump bias when it is determined that the main amplifier detection operation is to be performed.

[0009] In one embodiment, the demodulation module is a digital signal processor or a field-programmable gate array.

[0010] In one embodiment, the demodulation module includes a reference signal generation unit, an analog-to-digital conversion unit, a phase-sensitive detection unit, a digital low-pass filter unit, and an amplitude output unit. The reference signal generation unit is used to maintain clock synchronization with the signal modulation module and generate a synchronous reference signal that is in phase and frequency with the injected modulation signal. The analog-to-digital converter is used to convert the detected electrical signal into a digital signal; The phase-sensitive detection operation unit is used to perform a multiplication operation between the digital signal and the synchronization reference signal, so that the target signal is separated from the broadband noise in the frequency domain; The digital low-pass filter unit is used to perform low-pass filtering on the signal after multiplication, retaining the DC component that is proportional to the amplitude of the modulated signal. The amplitude output unit is used to calibrate and quantize the DC component, output amplitude data that is positively correlated with the intensity of the modulated signal light, and transmit it to the processing module.

[0011] In one embodiment, the processing module is further configured to determine the damage level of the optical path as slight damage when the amplitude attenuation ratio is not greater than a first preset threshold; determine the damage level of the optical path as moderate damage when the amplitude attenuation ratio is greater than the first preset threshold but not greater than a second preset threshold; and determine the optical path as completely damaged when the amplitude attenuation ratio is greater than the second preset threshold.

[0012] In one embodiment, the processing module is further configured to determine the degree of transmission loss of the optical path between the modulation signal injection position and the detection point based on the amplitude attenuation ratio, and output a quantified damage degree parameter based on the degree of transmission loss; wherein, the modulation signal is transmitted along the optical path as an active detection signal along with the main laser signal, and the increase in optical signal transmission loss caused by damage at any position in the optical path is manifested as a corresponding attenuation of the amplitude of the modulation signal component, the amplitude attenuation ratio is positively correlated with the degree of optical path transmission loss, and the photodetector is set at the optical path detection port to collect the leaked scattered light to achieve non-invasive detection.

[0013] In one embodiment, the modulation signal is a sine wave or square wave with a frequency of 100 kHz, and the amplitude of the modulation signal is 0.1% of the intensity of the main laser signal.

[0014] Secondly, this application also provides a method for detecting optical path damage in a fiber laser, wherein the method is performed based on the fiber laser optical path damage detection system described in the first aspect; the method includes: The current amplitude and reference amplitude of the modulated signal component are obtained, wherein the reference amplitude is the amplitude information of the modulated signal component under the standard state of an intact optical path; The amplitude attenuation ratio is determined based on the current amplitude and the reference amplitude; When the amplitude attenuation ratio is greater than the preset loss threshold, it is determined that there is damage to the optical path, and the damage level of the optical path is determined according to the amplitude attenuation ratio.

[0015] The fiber laser optical path damage detection system of this application has the following advantages over related technologies: 1. The fiber laser optical path damage detection system of this application actively injects a modulation signal into the seed signal light or pump light of the fiber laser through a signal modulation module, and transmits it along the optical path together with the main laser. This overcomes the limitation of existing passive detection, which can only monitor scattered light and reflected light due to lag. Detection can be started during the power-on bias and pre-energy storage stage of the laser, without waiting for the damage to cause significant abnormal consequences. It can achieve active early warning in the early stage of optical path damage.

[0016] 2. By positioning the photodetector at the fusion splice or output of the main amplifier, and using the lock-in amplification mechanism of the demodulation module, the amplitude information of the modulation signal component is accurately extracted from the detected electrical signal, thus providing a directional reflection of the optical path transmission status at the fusion splice. Based on this, the processing module uses the amplitude of the modulation signal under ideal optical path conditions as a reference amplitude. By comparing the current amplitude with the reference amplitude to obtain the amplitude attenuation ratio and a preset damage threshold, it determines whether the optical path is damaged. The damage level of the optical path is then determined according to the attenuation ratio, providing a reliable reference for subsequent repair processing. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the application environment of the fiber laser optical path damage detection system in one embodiment of this application; Figure 2 This is a schematic diagram of the detection optical path of a fiber laser optical path damage detection system in one embodiment of this application; Figure 3 This is a schematic diagram of signal demodulation logic in one embodiment of this application; Figure 4 This is a schematic diagram illustrating the modulation and demodulation principle in one embodiment of this application; Figure 5 This is a flowchart illustrating a fiber laser optical path damage detection method in one embodiment of this application.

[0019] Explanation of reference numerals in the attached figures: 11-Fiber laser optical path damage detection system, 111-Signal modulation module, 112-Photodetector, 113-Demodulation module, 114-Processing module, 12-Fiber laser, 121-Seed source, 122-Preamplifier, 123-Main amplifier, 124-Laser main control. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] In some embodiments, such as Figure 1 and Figure 2As shown, this application provides a fiber laser optical path damage detection system 11, including: a signal modulation module 111, a photodetector 112, a demodulation module 113, and a processing module 114. It should be noted that the fiber laser 12 detected in this application adopts a master oscillation power amplifier architecture, including a seed source 121, a preamplifier 122, a main amplifier 123, a laser master controller 124, various passive optical devices, and fiber fusion splices. The seed source 121 serves as the laser signal originating unit, outputting a low-power, high-quality, and spectrally stable initial seed signal light, providing a high-quality signal substrate for subsequent power amplification. The preamplifier 122 incorporates a pre-amplifier pump, rare-earth-doped gain fiber, and matching beam combiner, used for preliminary power amplification of the weak signal light output from the seed source 121, boosting the signal light to a power level suitable for subsequent input stages. The main amplifier 123 is the core power enhancement unit of the laser, integrating a main amplifier pump, high-power gain fiber, and pump combiner structure. It is used to amplify the pre-amplified signal light at a high power rate and is the core section of the laser with the highest power handling capacity and the most concentrated component value. Passive optical components include pump combiners, fiber isolators, and output heads. The pump combiner combines the pump light and signal light and injects it into the gain fiber. Fiber isolators are placed between each stage of the link to ensure unidirectional optical signal transmission and suppress backlight damage to upstream components. The output head is located at the end of the optical path to output the final laser and ensure output safety. Fiber fusion splices are the connection nodes formed between different fiber segments and optical components through a fusion splicing process; they are essential structures for optical path transmission.

[0022] The signal modulation module 111 is used to inject a modulation signal into the seed signal light or pump light of the fiber laser 12, so that the modulation signal is transmitted along the optical path along with the main laser signal. The signal modulation module 111 injects the modulation signal into the seed signal light or pump light by superimposing a modulation electrical signal into the DC bias circuit of the corresponding light source of the fiber laser 12. The injected modulation signal is typically a sinusoidal signal or square wave with a frequency of approximately 100 kHz, and its intensity amplitude is approximately 0.1% of the main laser signal, which is a weak signal disturbance that does not interfere with the normal operation of the laser. The injection position of the modulation signal can be flexibly selected according to the detection requirements; it can be injected into the seed signal light link (e.g., the signal optical path of seed source 121 and preamplifier 122) or the pump source link (e.g., preamplifier pump and main amplifier pump).

[0023] In applications, the modulated signal, along with the main laser signal, is amplified by preamplifier 122 and transmitted to the main amplifier 123. It then enters the gain medium of the main amplifier 123 via the fusion splice at the input of the main amplifier 123. The applicable frequency range of the modulated signal is directly related to the injection method: if the modulated signal is injected into the seed signal light, the modulation frequency can reach the megahertz level; if the modulated signal is injected into the pump light, the modulation frequency is typically limited to tens of kilohertz due to the relaxation time of the upper energy level in the fiber amplifier gain medium (such as erbium-doped or ytterbium-doped fiber), and the selection of the modulation frequency must match the demodulation parameters of the downstream signal.

[0024] A photodetector 112 is positioned at the splice or output of the main amplifier 123 in the fiber laser 12 to convert the optical signal transmitted in the optical path into a detection electrical signal. The splice detection location can be selected from leakage nodes such as the splice after the wavelength division multiplexer at the input of the main amplifier 123 or the splice behind the output isolator. Positioning it at a specific splice point allows for directional monitoring of the optical path transmission integrity at that node, enabling precise location of damage. Positioning it at the output of the optical path covers the entire main amplifier 123 and the overall optical path status of subsequent output links. The selection of the location comprehensively considers the feasibility of structural installation and the leakage intensity at the corresponding position. Detection can be completed simply by collecting scattered light leaked from the fiber surface or device end face, without interfering with the main optical path transmission path and thus not interfering with the normal output of the laser.

[0025] The demodulation module 113 is used to demodulate the detection electrical signal through a lock-in amplification mechanism to extract the amplitude information of the modulation signal component. The detection electrical signal is mixed with the main laser background component, circuit thermal noise, and environmental stray noise. The modulation signal component carrying the optical path transmission state is very weak. However, the lock-in amplification mechanism can perform phase-sensitive detection based on a reference signal that is in phase and frequency with the injected modulation signal. With the strong noise suppression characteristics of its equivalent narrowband filter, it can effectively filter out various irrelevant interference components in an environment with extremely low signal-to-noise ratio. Thus, the amplitude information of the modulation signal component in the detection electrical signal can be accurately extracted, and the amplitude change characteristics of the modulation signal after optical path transmission can be completely preserved.

[0026] The processing module 114 is used to compare the current amplitude of the modulated signal component with the reference amplitude. When the amplitude attenuation ratio is greater than the preset loss threshold, it is determined that there is damage to the optical path. The damage level of the optical path is determined according to the amplitude attenuation ratio. The reference amplitude is the amplitude information of the modulated signal component under the standard state of the optical path being intact.

[0027] It is understood that the processing module 114 pre-stores the amplitude of the modulation signal component calibrated under the standard state of the optical path being intact as the judgment reference amplitude, and then obtains the current amplitude of the modulation signal component output by the demodulation module 113 in real time. By calculating the attenuation ratio of the current amplitude relative to the reference amplitude, and combining the optical path transmission characteristics that the degree of splice damage is positively correlated with the attenuation of the modulation signal amplitude, the amplitude attenuation ratio is compared with a preset damage threshold. When the attenuation ratio is greater than the preset damage threshold, it is determined that there is damage to the optical path, and the damage level of the optical path is determined according to the degree of change of the amplitude attenuation ratio, thereby realizing the quantitative evaluation and classification judgment of the optical path damage state.

[0028] The aforementioned fiber laser optical path damage detection system 11 actively injects a modulation signal into the seed signal light or pump light of the fiber laser 12 through the signal modulation module 111, and the modulation signal is transmitted along the optical path together with the main laser. This overcomes the limitation of existing passive detection systems, which can only monitor scattered light and reflected light due to lag. Detection can be started during the laser's power-on bias and pre-energy storage stages, without waiting for damage to cause significant abnormal consequences, and can provide proactive early warning in the early stages of optical path damage. The photodetector 112 is fixedly set at the fusion point or output end of the main amplifier 123, and in conjunction with the lock-in amplification mechanism of the demodulation module 113, the amplitude information of the modulation signal component is accurately extracted from the detection electrical signal, which can directionally reflect the optical path transmission status at the fusion point. Based on this, the processing module 114 uses the amplitude of the modulation signal under the standard state of an intact optical path as the reference amplitude. By comparing the amplitude attenuation ratio obtained by comparing the current amplitude with the reference amplitude and the preset damage threshold, it determines whether the optical path is damaged, and determines the damage level of the optical path according to the attenuation ratio, providing a reliable reference for subsequent repair processing.

[0029] In some embodiments, the processing module 114 is further configured to control the signal modulation module 111 to inject a modulation signal into the seed signal light of the fiber laser 12 when it is determined that a full-optical-path detection operation is to be performed.

[0030] The processing module 114 can determine the optical path detection requirements based on the input instructions.

[0031] It is understood that the processing module 114 can switch the injection path of the modulation signal according to different detection range requirements. When it is determined to perform full optical path detection, it sends a control command to the signal modulation module 111 to control it to inject the modulation signal into the seed signal optical link of the fiber laser 12. Specifically, the modulation electrical signal is superimposed on the pump bias circuit of the seed source 121 so that the modulation component is fused with the seed light signal. Since the seed light is the starting signal source of the entire optical path, it will flow through the preamplifier 122, the main amplifier 123 and all fusion points and passive devices along the way until the detection point. The modulation signal injected can completely traverse the entire optical path from the seed end to the detection end, thereby supporting full coverage detection of the integrity of the entire optical path transmission.

[0032] In some embodiments, the processing module 114 is further configured to control the signal modulation module 111 to inject a modulation signal at the pre-pump bias when determining to perform detection work on the pre-pump to detection point optical path.

[0033] It is understandable that when the processing module 114 determines to perform optical path detection in the preamplifier-to-detection point section, it outputs a control command to the signal modulation module 111, controlling it to inject the modulation signal into the bias of the preamplifier pump. During the preamplifier operation, the pump drive current superimposed with the modulation signal causes the pump output energy to fluctuate synchronously with the modulation law, thereby causing the gain level of the gain medium of the preamplifier 122 to change periodically. Ultimately, the signal light output by the preamplifier 122 carries the corresponding modulation component. This modulation component is transmitted along the subsequent optical path with the main laser and arrives at the detection point, thus enabling directional detection of the degree of optical path damage from the preamplifier 122 to the detection point.

[0034] In some embodiments, the processing module 114 is further configured to control the signal modulation module 111 to inject a modulation signal at the main amplifier pump bias when it is determined that the detection operation of the main amplifier 123 is to be performed.

[0035] In applications, the high-value portion of the laser is concentrated in the main amplifier, which is also the area with high power handling and vulnerability. Adding a modulated signal here can solve most problems. Therefore, to protect the high-value components, the main amplifier pump terminal can be injected with a modulation signal.

[0036] It is understandable that the processing module 114 can determine, based on the specific testing requirements of the main amplifier 123 or the protection targets of the core high-value components, when performing testing work on the main amplifier 123 section, issue corresponding control commands to the signal modulation module 111 to control it to inject the modulation signal into the pump bias of the main amplifier. During the operation of the main amplifier 123, the pump drive current superimposed with the modulation signal will cause the pump output energy to fluctuate synchronously with the modulation law, thereby allowing the signal light output by the main amplifier 123 to carry the corresponding modulation component, thereby directionally detecting the degree of damage to the main amplifier 123. As the core component of the laser with concentrated cost, high power handling, and relatively fragile structure, the main amplifier 123 is also the most vulnerable critical section in the optical path. Injecting a modulation signal here can rely on the sufficient pump energy of the main amplifier to obtain higher signal resolution and signal-to-noise ratio, with better detection accuracy and reliability. It can not only specifically monitor the operating status of the core high-value components, but also achieve key protection for high-risk sections of the optical path.

[0037] In some embodiments, the demodulation module 113 is a digital signal processor or a field-programmable gate array.

[0038] It is understandable that if the demodulation module 113 is a digital signal processor or a field-programmable gate array (FPGA), then a fully digital architecture can be used to implement the phase-locked loop (PLL) amplification and demodulation function. Its demodulation parameters can be flexibly configured through software, adapting to the modulation frequency requirements of different scenarios such as seed light injection and pump light injection without modifying the hardware circuit. It supports demodulation of a wide range of modulation signals from tens of kilohertz to megahertz, making the solution more adaptable. In addition, the digital operation mode is not affected by the temperature drift and parameter drift of analog devices, has stronger resistance to environmental interference, and has better demodulation accuracy and long-term operational stability. It can stably output accurate modulation signal amplitude data, avoiding damage judgment errors caused by hardware parameter deviations. At the same time, this architecture can integrate the entire demodulation process, such as phase-sensitive detection, digital filtering, and amplitude quantization, into a single chip, effectively reducing the complexity of peripheral circuits and the number of components, improving module integration and system reliability. Moreover, relying on the high-speed signal processing capability of the digital signal processor and the parallel operation characteristics of the FPGA, real-time demodulation output of the modulation signal can be achieved, fully meeting the low-latency detection requirements in scenarios such as laser power-on self-test and real-time monitoring during operation.

[0039] In some embodiments, such as Figure 3 and Figure 4 As shown, the demodulation module 113 includes a reference signal generation unit, an analog-to-digital conversion unit, a phase-sensitive detection and calculation unit, a digital low-pass filter unit, and an amplitude output unit.

[0040] The reference signal generation unit is used to maintain clock synchronization with the signal modulation module 111, generating a synchronization reference signal that is in phase and frequency with the injected modulation signal. The analog-to-digital conversion unit converts the detected electrical signal into a digital signal. The phase-sensitive detection unit performs a multiplication operation between the digital signal and the synchronization reference signal, separating the target signal from broadband noise in the frequency domain. The digital low-pass filter unit performs low-pass filtering on the multiplied signal, retaining the DC component proportional to the modulation signal amplitude. The amplitude output unit calibrates and quantizes the DC component, outputting amplitude data positively correlated with the modulation signal intensity, and transmits it to the processing module 114.

[0041] The core of demodulation module 113 is phase-sensitive detection technology. When the reference signal generation unit operates, the system generates a reference signal that is in phase and frequency with the original modulation signal. The analog-to-digital converter unit converts the detected electrical signal into a digital signal. The phase-sensitive detection arithmetic unit multiplies the digital signal obtained from the detected electrical signal with the synchronization reference signal in a multiplier to obtain a DC component and a high-frequency component proportional to the amplitude of the modulation signal. Let the input signal be Acos(ωt+θ), and the in-phase and frequency-coherent reference signal be cos(ωt+θ). Multiplying them yields:

[0042] Acos(ωt+θ)cos(ωt+θ)=A / 2+A / 2*cos(2ωt+2θ) As can be seen from the above equation, the product contains a DC component (A / 2) and a second harmonic component (A / 2*cos(2ωt+2θ)). Then, by simply filtering the signal after the multiplication operation using a digital low-pass filter unit to remove the high-frequency components, the DC signal proportional to the amplitude of the modulated signal can be extracted.

[0043] In some embodiments, the processing module 114 is further configured to determine the damage level of the optical path as slight damage when the amplitude attenuation ratio is not greater than a first preset threshold; determine the damage level of the optical path as moderate damage when the amplitude attenuation ratio is greater than the first preset threshold but not greater than a second preset threshold; and determine the optical path as completely damaged when the amplitude attenuation ratio is greater than the second preset threshold.

[0044] For example, the calculation process for the current amplitude of the modulated signal component can be described below. Assuming the laser is a 500W nanosecond pulsed laser, based on the small-signal perturbation model, the optical path is decomposed into cascaded subsystems, focusing on the gain dynamic characteristics of the high-power saturated amplifier, treating the entire link as a cascaded system. Let the modulated signal be a small-signal perturbation injected into the seed, with a complex amplitude of... The system transfer function can be written as:

[0045] in, Electro-optic modulation response (usually considered as flat gain) ), For the gain response of preamplifier 122, The gain response of the main amplifier 123 (core component). For the passive transmission response of the output isolator and fusion splice, This represents the response of the photodetector 112 and the transimpedance amplifier (TIA).

[0046] For ytterbium-doped (Yb) fiber amplifiers, the gain dynamics are dominated by the rate equation. For signal optical power... and the number of particles in the upper energy level The simplified rate equation is:

[0047] in, The lifetime of the upper energy level (Yb is approximately 0.8~1ms). For stimulated emission cross section, This represents the pumping rate.

[0048] At a high power output of 500W, the main amplifier 123 is in a state of deep saturation. At this time, the stimulated emission rate is extremely fast, and the effective upper level lifetime is compressed to: in, This represents the photon flux. For a quantity in the 500W range, the equivalent stimulated emission lifetime is... Typically, it takes from a few microseconds to tens of microseconds (depending on the core area and power density).

[0049] By applying a small-signal perturbation to the rate equation near the steady-state operating point and taking its Laplace transform, we obtain a first-order low-pass form for the signal gain response to the input signal: in, This is the steady-state small-signal gain coefficient.

[0050] Passive fiber optic components themselves do not change with frequency (ignoring picosecond-level dispersion delay), and are proportional components. Let the transmittance of the output isolator be... The transmittance of the weld point is Passive link (isolation device + fusion splice) response The calculation formula is:

[0051] in, This is the loss coefficient at the weld joint. This is the effective length of the weld joint. When the weld joint is intact... (Typical value). When damage occurs at the weld joint (microcracks, ablation, thermal stress deformation), the mode field matching at that point deteriorates, and scattering loss increases. Decrease. In the initial stages of damage at this point, the loss changes. It is directly proportional to the degree of damage.

[0052] The photodetector 112 receives light intensity signals, and its equivalent circuit is a transimpedance amplifier. Limited by the op-amp's gain-bandwidth product and the photodetector's junction capacitance, the response of the photodetector 112 is also a first-order low-pass:

[0053] in, For responsiveness (A / W), This is the cutoff angular frequency of the photodetector (typically ranging from a few MHz to tens of MHz). The above steps are cascaded, and the extremely short latency of fiber optic transmission is ignored. (The phase term does not affect amplitude detection) The overall system transfer function is: Among them, the total system gain coefficient for: This is a typical second-order low-pass system (with two poles). At the set modulation frequency... Below, the amplitude detected by the lock-in amplifier is:

[0054] The system transfer function is equivalent to a bandpass filter, whose passband gain coefficient is negatively correlated with the weld point loss coefficient. By extracting the change (amplitude) of this gain coefficient through a lock-in amplifier, the degree of weld point damage can be quantitatively inverted.

[0055] In this embodiment, damage to the weld joint is directly manifested as The decrease of, i.e. It decays proportionally.

[0056] In good condition: The output amplitude is .

[0057] Damage status: The output amplitude is .

[0058] Therefore, the relative change caused by the damage is: Correspondingly, the amplitude attenuation ratio is positively correlated with the degree of damage to the fusion joint. When the amplitude attenuation ratio is not greater than the first preset threshold, the damage level of the optical path is determined to be minor (A1 level). This corresponds to initial minor damage to the fusion joint, such as micro-cracks, slight contamination, or localized minor ablation. The transmission loss of the optical path only increases slightly and has not yet affected the normal operation of the laser. The laser can continue to be used at full power. When the amplitude attenuation ratio is greater than the first preset threshold but not greater than the second preset threshold, the damage level of the optical path is determined to be moderate (A2 level). At this time, the transmission loss of the fusion joint has significantly increased, and the damage is at risk of rapid deterioration under the continuous action of high-power laser. The laser needs to reduce its power output. When the amplitude attenuation ratio is greater than the second preset threshold, the optical path is determined to be completely damaged (A3 level). This corresponds to a severe failure state, such as overall breakage or large-area burn-out of the fusion joint. The optical path transmission function is completely lost, and it cannot transmit effective modulation signals. The laser is locked and output is not allowed.

[0059] In some embodiments, the processing module 114 is further configured to determine the degree of transmission loss of the optical path between the modulation signal injection position and the detection point based on the amplitude attenuation ratio, and output a quantified damage degree parameter based on the degree of transmission loss; wherein, the modulation signal is transmitted along the optical path as an active detection signal along with the main laser signal, and the increase in optical signal transmission loss caused by damage at any position in the optical path is manifested as a corresponding attenuation of the amplitude of the modulation signal component, the amplitude attenuation ratio is positively correlated with the degree of optical path transmission loss, and the photodetector is set at the optical path detection port to collect the leaked scattered light to achieve non-invasive detection.

[0060] The core detection mechanism of this application is understood to be: by actively injecting a modulation signal as an optical path "probe," and utilizing the characteristic that changes in optical path transmission loss cause corresponding attenuation of the modulation signal amplitude, the detection and quantification of optical path damage can be achieved. Specifically, the modulation signal propagates along the optical path along with the main laser. When damage or performance degradation occurs at any location in the optical path (including but not limited to fiber fusion splices, pump combiners, fiber isolators, gain fiber segments, etc.), it will lead to an increase in the transmission loss of the optical signal, and the intensity of the modulation signal reaching the photodetector will decrease accordingly, manifested as an attenuation of the modulation signal component amplitude. The wider the damage range and the more severe the damage, the greater the transmission loss and the more significant the attenuation of the modulation signal amplitude. The photodetector is set at the optical path detection port (such as the surface of the fusion splice or the output end), and achieves non-invasive detection by collecting scattered light leaked from the fiber surface or device end face, without intervening in the main optical path transmission path. Based on the detected amplitude attenuation ratio, the processing module 114 can quantitatively invert the transmission loss of the optical path from the modulation signal injection position to the detection point, and then output quantified damage parameters to provide data basis for laser operation status monitoring, fault source analysis and protection strategy adjustment.

[0061] In some embodiments, please refer to Figure 5 This application also provides a method for detecting optical path damage in a fiber laser, which is performed based on a fiber laser optical path damage detection system according to any of the above schemes. The fiber laser optical path damage detection method includes the following steps S501 to S503.

[0062] S501: Obtain the current amplitude and reference amplitude of the modulated signal component, wherein the reference amplitude is the amplitude information of the modulated signal component under the standard state where the optical path is intact.

[0063] S502: Determine the amplitude attenuation ratio based on the current amplitude and the reference amplitude.

[0064] S503: When the amplitude attenuation ratio is greater than the preset loss threshold, it is determined that there is damage to the optical path, and the damage level of the fusion splice is determined according to the amplitude attenuation ratio.

[0065] It should be noted that the fiber laser optical path damage detection method provided in this application embodiment and the fiber laser optical path damage detection system provided in this application embodiment are based on the same inventive concept. Therefore, the specific implementation of this embodiment can refer to the implementation of the aforementioned fiber laser optical path damage detection system, and the repeated parts will not be described again.

[0066] In some embodiments, an electronic device provided in this application includes a processor and a memory; the memory stores a computer program, wherein the computer program, when executed by the processor, implements the above-described fiber laser optical path damage detection method.

[0067] Specifically, the processor may include, for example, a general-purpose microprocessor, an instruction set processor and / or an associated chipset and / or a special-purpose microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor may also include onboard memory for caching purposes. The processor may be a single processing unit or multiple processing units for performing different actions of the method flow according to embodiments of this application.

[0068] Memory can be any medium capable of containing, storing, transmitting, propagating, or transmitting instructions. For example, memory can include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, instruments, or propagation media. Specific examples of memory include: magnetic storage devices such as magnetic tape or hard disk drives (HDDs); optical storage devices such as optical discs (CD-ROMs); and also random access memory (RAM) or flash memory; and / or wired / wireless communication links.

[0069] This application also provides a non-transitory computer storage medium storing a computer program thereon, which, when executed by a processor, implements the aforementioned fiber laser optical path damage detection method. This computer-readable medium may be included in the device / apparatus / system described in the above embodiments; or it may exist independently and not assembled into that device / apparatus / system. The aforementioned computer-readable medium carries one or more programs, which, when executed, implement the method as described in the embodiments of this application.

[0070] According to embodiments of this application, a computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this application, a computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In this application, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media can also be any computer-readable medium other than computer-readable storage media, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wireless, wired, optical fiber, radio frequency signals, etc., or any suitable combination thereof.

[0071] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0072] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application, even if such combinations or combinations are not explicitly described in this application. All such combinations and / or combinations fall within the scope of this application. Therefore, the scope of this application should not be limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A fiber laser optical path damage detection system, characterized in that, include: Signal modulation module, photodetector, demodulation module, and processing module; The signal modulation module is used to inject a modulation signal into the seed signal light or pump light of the fiber laser, so that the modulation signal is transmitted along the optical path together with the main laser signal. The photodetector is located at the fusion splice or output end of the main amplifier in the fiber laser and is used to convert the optical signal transmitted in the optical path into a detection electrical signal. The demodulation module is used to demodulate the detected electrical signal through a lock-in amplification mechanism and extract the amplitude information of the modulated signal component; The processing module is used to compare the current amplitude of the modulated signal component with the reference amplitude. When the amplitude attenuation ratio is greater than the preset loss threshold, it is determined that there is damage to the optical path. The damage level of the optical path is determined according to the amplitude attenuation ratio. The reference amplitude is the amplitude information of the modulated signal component under the standard state of an intact optical path.

2. The fiber laser optical path damage detection system as described in claim 1, characterized in that, The processing module is also used to control the signal modulation module to inject the modulation signal into the seed signal light of the fiber laser when it is determined that a full-optical-path detection operation is to be performed.

3. The fiber laser optical path damage detection system as described in claim 1, characterized in that, The processing module is also used to control the signal modulation module to inject the modulation signal at the pre-pump bias when determining to perform the detection work of the pre-pump to detection point optical path.

4. The fiber laser optical path damage detection system as described in claim 1, characterized in that, The processing module is also used to control the signal modulation module to inject the modulation signal at the main amplifier pump bias when it is determined that the main amplifier detection work is to be performed.

5. The fiber laser optical path damage detection system as described in claim 1, characterized in that, The demodulation module is a digital signal processor or a field-programmable gate array.

6. The fiber laser optical path damage detection system as described in claim 5, characterized in that, The demodulation module includes a reference signal generation unit, an analog-to-digital conversion unit, a phase-sensitive detection and calculation unit, a digital low-pass filter unit, and an amplitude output unit. The reference signal generation unit is used to maintain clock synchronization with the signal modulation module and generate a synchronous reference signal that is in phase and frequency with the injected modulation signal. The analog-to-digital converter is used to convert the detected electrical signal into a digital signal; The phase-sensitive detection operation unit is used to perform a multiplication operation between the digital signal and the synchronization reference signal, so that the target signal is separated from the broadband noise in the frequency domain; The digital low-pass filter unit is used to perform low-pass filtering on the signal after multiplication, retaining the DC component that is proportional to the amplitude of the modulated signal. The amplitude output unit is used to calibrate and quantize the DC component, output amplitude data that is positively correlated with the intensity of the modulated signal light, and transmit it to the processing module.

7. The fiber laser optical path damage detection system as described in claim 1, characterized in that, The processing module is further configured to determine the damage level of the optical path as slight damage when the amplitude attenuation ratio is not greater than the first preset threshold; determine the damage level of the optical path as moderate damage when the amplitude attenuation ratio is greater than the first preset threshold but not greater than the second preset threshold; and determine the optical path as completely damaged when the amplitude attenuation ratio is greater than the second preset threshold.

8. The fiber laser optical path damage detection system as described in claim 7, characterized in that, The processing module is further configured to determine the degree of transmission loss of the optical path between the modulation signal injection position and the detection point based on the amplitude attenuation ratio, and output a quantified damage degree parameter based on the degree of transmission loss; wherein, the modulation signal is transmitted along the optical path as an active detection signal along with the main laser signal, and the increase in optical signal transmission loss caused by damage at any position in the optical path is manifested as a corresponding attenuation of the amplitude of the modulation signal component, the amplitude attenuation ratio is positively correlated with the degree of optical path transmission loss, and the photodetector is set at the optical path detection port to collect the leaked scattered light to achieve non-invasive detection.

9. The fiber laser optical path damage detection system as described in claim 1, characterized in that, The modulation signal is a sine wave or square wave with a frequency of 100kHz, and the amplitude of the modulation signal is 0.1% of the intensity of the main laser signal.

10. A method for detecting optical path damage in a fiber laser, characterized in that, The fiber laser optical path damage detection method is performed based on the fiber laser optical path damage detection system as described in any one of claims 1 to 9; The fiber laser optical path damage detection method includes: The current amplitude and reference amplitude of the modulated signal component are obtained, wherein the reference amplitude is the amplitude information of the modulated signal component under the standard state of an intact optical path; The amplitude attenuation ratio is determined based on the current amplitude and the reference amplitude; When the amplitude attenuation ratio is greater than the preset loss threshold, it is determined that there is damage to the optical path, and the damage level of the optical path is determined according to the amplitude attenuation ratio.

Images