Fiber Laser Power Monitoring Device and Its Fabrication Method

Abstract

This invention provides a fiber laser power monitoring device and its fabrication method. The device includes: an optical fiber, a cladding light filter, a photodetector, and a fixing structure; wherein the cladding light filter is located on both sides of the photodetector and is used to filter out cladding light in the optical fiber; the photodetector is used to detect signal light in the optical fiber; the fixing structure is used to fix the optical fiber, the cladding light filter, and the photodetector together. The monitoring device of this invention eliminates the influence of cladding light and other interference factors, effectively achieving accurate monitoring of the fiber laser power.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and more specifically, to a power monitoring device for fiber lasers and its fabrication method. Background Technology

[0002] Currently, the output power of fiber lasers is continuously increasing and they are widely used in various fields such as daily life, industry, and military. In precision machining, the stability of fiber laser output power has a crucial impact on the machining effect. However, due to factors such as pump source drift caused by temperature changes in the working environment, the thermal lensing effect of active fibers, and the long-term stability of passive optical components, the output power of fiber lasers is usually unstable. In extreme cases, if the internal optical components of the fiber laser are damaged, the problem cannot be detected in time based solely on the actual machining effect, leading to further deterioration of optical components or even destructive failure of the entire optical path, resulting in huge losses. Therefore, how to monitor the output power of fiber lasers in real time and accurately, effectively protect against failure risks, and adaptively adjust the laser output power based on monitoring feedback to keep it within a relatively stable range to meet the needs of precision machining is a key technology that is essential for domestically produced high-power fiber lasers to enter the high-end product market.

[0003] For all-fiber lasers, monitoring output power using fiber beam splitters is a common method, as described in patent CN115411595A. By properly controlling the splitting ratio of the beam splitter, the splitting power can accurately reflect the dynamic changes in laser output power. However, fiber beam splitters have limited signal tolerance, and adding a fiber device to the laser link introduces additional insertion loss and failure risks. Therefore, they are generally used for low-power fiber lasers and are not suitable for online power monitoring of high-power fiber lasers. Currently, for high-power fiber lasers, the following two methods are commonly used for power monitoring:

[0004] 1. Pump monitoring involves monitoring the actual output power and temperature of the pump source. Based on the target power and temperature values, the pump current and pump source temperature are adjusted to regulate the output power of the fiber laser, enabling real-time compensation and calibration. However, considering the long-term stability of other components in the optical path, there is no clear correlation between pump power and actual laser output power; it can only serve as a reference.

[0005] 2. Monitor the output power of the laser by monitoring the intensity of the cladding light scattered by the cladding light filter at the output end, such as... Figure 1As shown, the photodetector detects the cladding light scattered by the cladding light filter. The drawbacks of this method are: a. After prolonged operation, factors such as photon darkening, mode instability, and thermal defects within the gain fiber of the fiber can lead to an increase in cladding light and a decrease in signal light. Simply monitoring changes in cladding light cannot accurately reflect the actual laser power. b. For high-power fiber lasers, the cladding power scattered by the cladding light filter is high, causing the photodiode to heat up easily. The dark current caused by temperature changes reduces the accuracy of the diode's optical signal detection and also affects its lifespan. c. In actual processing, especially when processing highly reflective materials, some of the reflected light from the material surface enters the fiber cladding, interfering with the photodiode's detection results. Summary of the Invention

[0006] This invention provides a fiber laser power monitoring device and its fabrication method, aiming to monitor and adjust the output power of the fiber laser in real time to ensure the stability and accuracy of laser processing. The core components of the device include an optical fiber, a photodetector, a cladding optical filter, and a fixing structure. The graded texturing method of the cladding optical filter ensures uniform heat dissipation, avoids localized overheating, thereby preventing fiber damage and enhancing the long-term reliability of the device. The device characterizes the actual output power by detecting changes in the intensity of the radiated light from the fiber core signal light, thus providing real-time monitoring and adjustment.

[0007] In a first aspect, the present invention provides a fiber laser power monitoring device, characterized in that the device comprises: an optical fiber, a cladding optical filter, a photodetector, and a fixing structure; wherein...

[0008] The cladding light filter is located on both sides of the photodetector and is used to filter out the cladding light in the optical fiber;

[0009] The photodetector is used to detect signal light in the optical fiber;

[0010] The fixing structure is used to fix the optical fiber, the cladding optical filter and the photodetector into one unit.

[0011] Secondly, the present invention also provides a method for fabricating a fiber laser power monitoring device, characterized in that the device comprises: an optical fiber, a cladding optical filter, a photodetector, and a fixing structure; the method comprises:

[0012] The cladding light filter is disposed on both sides of the photodetector to filter out the cladding light in the optical fiber;

[0013] The optical detector is configured to detect the signal light in the optical fiber;

[0014] A fixed structure is used to fix the optical fiber, the cladding optical filter, and the photodetector into one unit.

[0015] The fiber laser power monitoring device and its fabrication method provided by this invention avoid interference from cladding light generated during internal and external laser processing on signal light detection. It offers high power monitoring accuracy, utilizes a gradient-textured cladding light filtering method, ensures uniform heat dissipation, and provides high long-term reliability. It can be used for online power monitoring of high-power fiber lasers. Precise online power monitoring allows for adaptive adjustment of laser output power. The control unit automatically compensates the pump drive for appropriate current based on real-time feedback of laser power to control the stability of the fiber laser output power and ensure consistent processing results. The fiber laser power online monitoring device of this invention has a simple structure and is easy to operate, making it suitable for engineering and commercial applications. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of an existing power online monitoring device;

[0018] Figure 2 This is a schematic diagram of a fiber laser power monitoring device provided in an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of another fiber laser power monitoring device provided in an embodiment of the present invention;

[0020] Figure 4 This is a graph showing the change of the actual output power of the fiber laser and the value collected by the power monitoring device over time, as provided in this embodiment of the invention.

[0021] Figure 5 The graph shows the variation of the error between the laser power fed back from four retests and the corresponding actual output power of the fiber laser provided in the embodiments of the present invention as a function of the fed-back laser power.

[0022] Figure 6 This is a flowchart illustrating the fabrication method of the fiber laser power monitoring device provided in this embodiment of the invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Invention Overview

[0025] As mentioned above, the present invention provides a fiber laser power monitoring device and its preparation method, which eliminates the influence of cladding light and other interference factors, and effectively realizes accurate monitoring of fiber laser power.

[0026] Exemplary device

[0027] Figure 2 This is a schematic diagram of the fiber laser power monitoring device provided in an embodiment of the present invention, as shown below. Figure 2 As shown, the device 100 provided in this embodiment includes: an optical fiber 101, a cladding optical filter 102, a photodetector 103, and a fixed structure 104.

[0028] The fixing structure 104 is used to fix the optical fiber 101, the cladding optical filter 102 and the photodetector 103 into one unit.

[0029] The optical fiber 101 is a passive optical fiber, used only for transmitting optical signals and not for optical amplification. For example, it is a double-clad passive optical fiber or a triple-clad passive optical fiber.

[0030] The core diameter / cladding diameter of the optical fiber 101 includes, but is not limited to, 20 / 250, 20 / 400, and 30 / 400.

[0031] The optical fiber 101 includes a central region and stripped regions at the left and right ends of the central region.

[0032] The length of the intermediate region is greater than 1 centimeter.

[0033] The stripping region is the area where the coating layer of the optical fiber 101 is stripped off. The stripping region includes a textured region and non-textured regions at both ends of the textured region. The textured region is used to absorb cladding light.

[0034] The roughened area is obtained by roughening the stripped area using an etchant or laser etching method. For example, the stripped area is cleaned with alcohol and then roughened with an etchant such as glass frosting paste or a laser etching method to remove residual cladding light.

[0035] The non-textured regions at both ends serve as a transition, preventing structural abrupt changes between the texturized region and the complete coating layer from burning the flammable coating layer in the middle, thus reducing the risk of fiber damage. A non-textured region of more than 0.5 cm is reserved at each end of the texturized region.

[0036] The cladding light filter 102 is located on both sides of the photodetector 103 and is used to filter out the cladding light in the optical fiber 101.

[0037] The cladding light filter 102 includes the texturing region and the texturing region encapsulator.

[0038] The degree of texturing on the inner cladding surface of the fiber in the texturing region is greater near the central region than far from the central region.

[0039] Preferably, the degree of texturing on the inner cladding surface of the fiber in the texturing region decreases uniformly from the position near the central region to the position away from the central region. That is, a gradient texturing method is adopted, and the degree of texturing on the inner cladding surface of the fiber increases uniformly from the cladding light input end to the output end, thereby uniformly absorbing cladding light and avoiding a large amount of cladding light leakage at the front end due to abrupt changes in the fiber cladding structure, which would cause a rapid increase in local temperature. This achieves the effect of uniform temperature rise of the cladding light filter 102 as a whole. The gradient texturing directions of the left and right texturing regions are opposite. The texturing degree of the left texturing region increases from light to dark from the forward laser input end to the output end, while the texturing degree of the right texturing region decreases from dark to light from the forward laser input end to the output end. The left texturing region is used to filter out residual cladding light carried by the front-end laser, while the right texturing region is mainly used to filter out cladding light that returns from the workpiece surface into the fiber during processing.

[0040] In summary, the goal is to gradually reduce cladding light, rather than suddenly absorbing a large amount of cladding light, which would lead to rapid localized heat accumulation. If the surface of the texturing region is uniformly texturing, excessive heat will be generated in the area where cladding light leakage begins, potentially damaging the fiber. By gradually increasing the degree of texturing, the cladding light throughout the entire fiber is filtered out uniformly and effectively, ensuring long-term stable operation of the fiber and reducing interference and damage caused by cladding light. This improves the power monitoring accuracy and reliability of high-power fiber lasers.

[0041] The texturing region encapsulator is used to suspend and encapsulate the texturing region, preventing external dust from adhering to the texturing region and causing the optical fiber to burn out. To ensure that the entire stripping region is protected, the length of each texturing region encapsulator is longer than the length of the corresponding stripping region.

[0042] The texturing region encapsulator is made of a transparent material with smooth inner and outer surfaces. The transparent material ensures that leaked cladding light can pass through to the filter cover structure 105, so that the filter cover structure 105 can absorb the cladding light. The smooth surface prevents contaminants from adhering to the texturing region encapsulator, reducing the risk of contamination of the texturing region.

[0043] The texturing region encapsulator may further include a sandwich layer containing a circulating coolant for absorbing cladding light and cooling the texturing region encapsulator. The color of the circulating coolant is complementary to the color of the laser in the optical fiber 101. For example, if the laser wavelength is 630 nm, a green coolant would be used. The circulating coolant is driven by a pump, and the coolant flow direction is as follows: Figure 2 As indicated by the arrow below, the flow originates from both sides of the optical fiber 101 toward the central region of the optical fiber 101, for efficient cooling of the textured region encapsulator.

[0044] Both ends of the texturized area encapsulator are fixed to the coating layer near the peeling opening to prevent it from shifting or falling off during use, for example, by using glue or other fixing materials.

[0045] The bottom of the fixing structure 104 includes a semi-circular groove, which is used to place the integrated structure consisting of the texturing region encapsulator after encapsulating the texturing region and the optical fiber 101.

[0046] For example, the texturing region encapsulator uses glass tubes, with two texturing regions suspended between two glass tubes. Adhesive is applied to both ends of the glass tubes for fixation, with the adhesive applied to the coating layer near the stripping opening of the corresponding middle region. After the glass tube encapsulation is completed, the integrated fiber optic glass tube is placed in the semi-circular groove at the bottom of the fixing structure 104, with the left glass tube located at the input end of the device 100. Adhesive is applied to both ends of the two glass tubes to fix them to the groove.

[0047] The device 100 further includes a filter cover structure 105, which is used to encapsulate the cladding light filter 102 to block the cladding light scattered by the cladding light filter 102, so as to avoid the irregularly scattered cladding light from affecting the detection results of the photodetector.

[0048] To reduce light reflection and scattering, the filter cover structure 105 is made of a dark-colored material with a rough surface. It can absorb most of the scattered light from the cladding light filter 102 and convert it into heat, which is then carried away by the fixing structure 104 via an external heat sink. That is, the fixing structure 104 is not only used to support and fix the filter cover structure 105, but also to receive the energy of the scattered cladding light absorbed by the filter cover structure 105. The fixing structure 104 is also made of a dark-colored material with a rough surface, which further reduces the interference of the internal scattered cladding light on the photodetector 103, maintaining the accuracy of the measurement and the stability of the system.

[0049] For example, the filter cover structure 105 and / or the fixing structure 104 may be treated with black anodizing to make the material surface rougher and have light-absorbing properties, thereby improving its ability to absorb scattered light and enhancing heat dissipation efficiency.

[0050] The photodetector 103 is used to detect signal light in the optical fiber 101. For example, the photodetector 103 is a photodiode, which detects signal light by detecting radiation inside the fiber core of the optical fiber 101.

[0051] The device 100 also includes a photodetector holder 106, which is located above the intermediate region.

[0052] The lower surface of the photodetector holder 106 and the upper surface of the fixing structure 104 both include semi-circular fiber grooves. The two are precisely aligned and cooperate with each other to form a complete fiber groove. The diameter of the fiber groove is slightly larger than the outer diameter of the fiber 101 to avoid damaging the fiber 101.

[0053] The fiber optic slot is spherical, which ensures that the radiation light generated by the signal light in the fiber optic 101 is concentrated in the fiber optic slot, which facilitates accurate detection by the photodetector 103.

[0054] Preferably, the surface of the fiber optic channel can be treated with copper plating or gold plating and polishing, or it can be coated with a high reflectivity material to enhance the reflection of radiated light on the surface of the fiber optic channel and avoid instability in optical signal detection due to weak radiated light.

[0055] A fiber optic cable trench is essentially a hollow sphere with high internal reflectivity. Light entering the sphere undergoes multiple reflections and diffuse reflections on the inner wall, creating a uniform light field. Due to the high reflectivity and diffuse reflection characteristics of the inner wall, the light is evenly distributed within the sphere, ensuring equal illuminance at any point on the wall. This guarantees the accuracy and stability of the measurement results. By measuring the light energy of a small area on the inner wall of the fiber optic cable trench, the total light energy emitted by the light source can be calculated.

[0056] The surface of the photodetector holder 106 is provided with small holes, for example, the diameter of the small holes is about 2 mm.

[0057] The photodetector 103 is embedded above the photodetector holder 106 and detects the radiation light generated by the signal light concentrated in the central region inside the fiber optic slot through the small hole.

[0058] When there is strong pump residual light, Raman scattered light, or other unwanted stray light in the optical fiber 101, in order to avoid these stray lights interfering with the photodetector 103 and affecting the accurate detection of output power, the device 100 also includes a filter, which is located between the photodetector 103 and the photodetector holder 106, for filtering out stray light other than signal light.

[0059] The device 100 further includes a control unit. The photodetector 103 is used to convert the detected optical signal into a current signal. The control unit is used to convert the current signal into a sampled value to characterize the actual output power of the fiber laser. For example, a photodiode converts the detected optical signal into a current signal. The current signal is converted into a voltage signal by the control circuit of the control unit. The voltage signal is then processed by the control unit to convert it into the required sampled value. The change in the sampled value is used to characterize the change in the actual output power of the fiber laser.

[0060] When the cladding light in the optical fiber 101 is strong, the device 100 also includes a temperature sensor 107, which is embedded in the upper surface of the photodetector holder 106. This sensor monitors the temperature change of the photodetector holder 106 in real time to determine if there are temperature fluctuations in the photodetector 103. Since the photodetector 103 is sensitive to temperature changes, the resulting changes in dark current within the photodetector 103 can affect the actual photocurrent signal and cause errors in the test results. The temperature fluctuations detected by the temperature sensor 107 can be used to calibrate the detection values ​​of the photodetector 103. This also identifies whether the scattered light generated by the two cladding light filters 102 affects the photodetector 103.

[0061] The device 100 also includes a top cover 108, which is used to seal the device 100 to prevent external dust from entering the interior and adhering to the surface of the optical fiber 101, causing the optical fiber to burn, and / or to avoid interference from external optical signals to the photodetector 103.

[0062] In summary, the entire fiber laser power monitoring device 100 characterizes the actual output power of the signal light by detecting the intensity change of the radiation light of the fiber core signal light, reducing the interference of cladding light generated during the internal and external processing of the fiber laser on the detection. At the same time, it takes into account the impact of temperature changes on the detection of the photodetector 103. The accuracy and long-term reliability of power monitoring are greatly improved. It can be used for online power monitoring of high-power fiber lasers. Moreover, the device 100 has a simple structure and is easy to operate, making it suitable for engineering and product applications.

[0063] As an optional embodiment, a 3500W fiber laser employing a high-power fiber laser online power monitoring device is provided, the online power monitoring device being as follows: Figure 3 As shown, it is located at the output end of the optical path structure of the fiber laser. To reduce the thermal impact of the two cladding optical filters 102 on the photodetector 103, the fixing structure 104 in this embodiment is a water-cooled plate, and the two cladding optical filters 102 are directly placed in the grooves on the water-cooled plate, which simplifies the structure of the upper cover 108. The optical fiber 101 used is a double-clad passive optical fiber with a core diameter / cladding diameter of 20 / 250 and a numerical aperture of 0.07 / 0.46. The stripped areas on both the left and right sides are 8cm. After the stripped areas are cleaned with alcohol, they are roughened with glass frosting paste. The roughening degree of the inner cladding surface of the fiber in the roughened area decreases uniformly from the position near the middle area to the position away from the middle area. 0.51 cm of unroughened area is reserved at both ends of each roughened area, that is, the unroughened area is 0.51 cm on each side. The roughened area encapsulator is a glass tube with an inner diameter of 0.8 mm, an outer diameter of 2.8 mm, and a length of 9 cm. Figure 4The data records the actual output power of the fiber laser and the changes in the acquired values ​​over a 53-minute period. Fluctuations in water temperature cause periodic changes in the actual output power, and the acquired values ​​provide corresponding periodic feedback, maintaining consistency with the changes in actual output power. Based on the correspondence between the acquired values ​​and laser power, the corresponding formula is processed and embedded into the control unit. The laser power can then be automatically and in real-time calculated based on the acquired values. Figure 5 The error between the actual output power and the feedback laser power corresponding to four retests of the fiber laser is shown. From low power to high power, the error between the two is basically controlled at about 1%. The feedback laser power can accurately represent the magnitude of the actual output power.

[0064] Exemplary methods

[0065] Accordingly, this embodiment of the invention also provides a method for fabricating a fiber laser power monitoring device 100. The device 100 includes: an optical fiber 101, a cladding optical filter 102, a photodetector 103, and a fixing structure 104. Figure 6 This is a flowchart illustrating the fabrication method of the fiber laser power monitoring device 100 provided in this embodiment of the invention. This embodiment includes the following steps:

[0066] S601: Set cladding light filters 102 on both sides of the photodetector 103 to filter out cladding light in the optical fiber 101.

[0067] S602: The photodetector 103 is set to detect the signal light in the optical fiber 101.

[0068] S603: The fixing structure 104 is set to fix the optical fiber 101, the cladding optical filter 102 and the photodetector 103 into one unit.

[0069] The cladding light filter 102 includes the texturing region.

[0070] The step of setting the cladding light filter 102 on both sides of the photodetector 103 to filter out the cladding light in the optical fiber 101 specifically includes:

[0071] The coating layers at both ends of the middle region of the optical fiber 101 are stripped to obtain the stripped area;

[0072] The middle section of the stripped area is roughened to obtain a roughened area;

[0073] By reserving a section of the area with the coating removed but not yet roughened at each end of the roughened area, a non-roughened area is obtained.

[0074] The degree of texturing on the inner cladding surface of the fiber in the texturing region is greater near the central region than far from the central region.

[0075] The degree of texturing on the inner cladding surface of the fiber in the texturing region decreases uniformly from the position near the middle region to the position far away from the middle region.

[0076] The length of the intermediate region is greater than 1 centimeter;

[0077] The length of the non-hairled region is greater than 0.5 cm.

[0078] The specific steps for roughening the middle section of the stripped area to obtain the roughened area are as follows:

[0079] The stripped area is roughened by etching with corrosive materials or by laser etching to obtain the roughened area.

[0080] The optical fiber 101 is a passive optical fiber;

[0081] The core diameter / cladding diameter of the optical fiber 101 includes 20 / 250, 20 / 400, and 30 / 400.

[0082] The cladding light filter 102 also includes a texturing region encapsulator;

[0083] The step of setting the cladding light filter 102 on both sides of the photodetector 103 to filter out the cladding light in the optical fiber 101 further includes:

[0084] Configure the textured region encapsulator.

[0085] The specific steps for setting the textured region encapsulator are as follows: fix both ends of the textured region encapsulator to the coating layer near the peeling port, so that the textured region encapsulator suspends and encapsulates the textured region.

[0086] The length of each of the texturing region encapsulators is longer than the length of the corresponding stripped region.

[0087] The textured area encapsulator is made of a transparent material with smooth inner and outer surfaces.

[0088] The texturing region encapsulator may further include a sandwich layer containing a circulating coolant for absorbing cladding light and cooling the texturing region encapsulator. The color of the circulating coolant is complementary to the color of the laser in the optical fiber 101.

[0089] The bottom of the fixing structure 104 includes a semi-circular groove;

[0090] The specific steps of fixing the optical fiber 101, the cladding optical filter 102, and the photodetector 103 into one unit using the fixing structure 104 include:

[0091] An integral structure consisting of the textured region encapsulator (after encapsulating the textured region) and the optical fiber 101 is placed in the semi-circular groove.

[0092] The device 100 also includes a filter cover structure 105;

[0093] The method further includes setting a filter cover structure 105 to encapsulate the cladding light filter 102 to block the cladding light scattered by the cladding light filter 102.

[0094] The filter cover structure 105 is made of a dark material with a rough surface.

[0095] The fixing structure 104 is made of a dark-colored material with a rough surface;

[0096] The method further includes setting the fixed structure 104 to receive the energy of the scattered cladding light absorbed by the filter cover structure 105.

[0097] The photodetector 103 is a photodiode.

[0098] The device 100 also includes a photodetector holder 106;

[0099] The method further includes positioning the photodetector holder 106 above the intermediate region.

[0100] The method further includes engaging the lower surface of the photodetector holder 106 with the semi-circular fiber optic groove on the upper surface of the fixing structure 104 to form a fiber optic groove, thereby concentrating the radiation light generated by the signal light in the intermediate region inside it.

[0101] The surface of the fiber optic groove is treated with copper plating or gold plating and polishing.

[0102] The fiber optic slot is spherical.

[0103] The diameter of the fiber slot is larger than the outer diameter of the fiber 101.

[0104] The specific steps of setting the photodetector holder 106 above the middle region are as follows: providing small holes on the surface of the photodetector holder 106;

[0105] The specific steps for setting the photodetector 103 to detect the signal light in the optical fiber 101 are as follows:

[0106] The photodetector 103 is embedded above the photodetector holder 106 so that the photodetector 103 can detect the radiation light generated by the signal light concentrated in the middle region inside the fiber optic slot through the small hole.

[0107] The method further includes placing a filter between the photodetector 103 and the photodetector holder 106 to filter out stray light other than the signal light.

[0108] The specific steps for setting the photodetector 103 to detect the signal light in the optical fiber 101 are as follows:

[0109] The photodetector 103 is configured to convert the detected light signal into a current signal;

[0110] The method also includes setting up a control unit to convert the current signal into a sampled value to characterize the actual output power of the fiber laser.

[0111] The method further includes setting a temperature sensor 107 embedded in the upper surface of the photodetector holder 106 to monitor the temperature change of the photodetector holder 106 in real time, thereby identifying whether the scattered light generated by the cladding light filter 102 affects the photodetector 103.

[0112] The method also includes providing a top cover 108 to seal the device 100 and prevent the entry of external dust and / or external light signals.

[0113] The fixed structure 104 is a water-cooled plate.

[0114] The numerical aperture of the optical fiber 101 is 0.07 / 0.46.

[0115] As an optional embodiment, the specific preparation method is as follows: First, take a section of double-clad passive optical fiber 101, such as 20 / 250, 20 / 400, 30 / 400, etc., and remove a section of the coating layer on both sides of the middle position of the optical fiber 101, leaving more than 1 cm unremoved in the middle of the optical fiber 101. Clean the removed area with alcohol, and then roughen it with an etchant such as glass frosting paste or laser etching to remove residual cladding light. Leave more than 0.5 cm unremoved at both ends of the stripped section. Use a gradient roughening method, and the roughening degree of the inner cladding surface of the optical fiber increases uniformly from the cladding light input end to the output end, thereby uniformly absorbing cladding light and avoiding a large amount of cladding light leakage at the front end due to abrupt changes in the cladding structure of the optical fiber 101, which would cause a rapid increase in local temperature. This achieves the effect of uniform temperature rise of the cladding light filter 102 as a whole.

[0116] Second, after the double-clad optical fiber 101 has undergone texturing, a glass tube is used as a texturing region encapsulator to encapsulate the texturing region, preventing external dust from adhering to the texturing region and causing the optical fiber 101 to burn out. The glass tube is longer than the coating stripping area, and the two texturing regions are placed between the two glass tubes respectively. Adhesive is applied to both ends of the glass tubes for fixation, with the adhesive applied to the coating near the stripping point of the coating stripping area. After the glass tube encapsulation is completed, the integrated optical fiber glass tube is placed in the semi-circular groove at the bottom of the device fixing structure 104. The left cladding optical filter 102 is located at the input end of the device, and the two glass tubes are fixed to the groove with adhesive applied to both ends.

[0117] Third, the upper filter cover structure 105 is used to block the cladding light scattered by the cladding light filter 102, so as to avoid the cladding light randomly scattered by the cladding light from affecting the detection results of the photodetector 103. The filter cover structure 105 is treated with black anodizing, which can absorb most of the scattered light from the cladding light filter 102 and convert it into heat, which is then carried away by the fixing structure 104 through the external heat sink. The fixing structure 104 can also be black anodized, which further reduces the uncertainty caused by the internal scattered cladding light.

[0118] Fourth, the photodetector holder 106 is positioned above the optical fiber 101 between the two clad optical filters 102, i.e., in the middle region. Both the upper middle surface of the fixing structure 104 and the lower surface of the photodetector holder 106 are engraved with semi-circular fiber grooves. These grooves cooperate with each other, with the fiber groove diameter slightly larger than the outer diameter of the double-clad optical fiber 101 to prevent damage to the fiber 101 and to ensure that the radiation light generated by the signal light in the double-clad optical fiber 101 is concentrated within the fiber groove. The surface of the fiber groove is plated with copper or gold and polished to enhance the reflection of the radiation light on the groove surface, preventing instability in optical signal detection due to insufficient radiation light. The photodetector 103 is embedded above the photodetector holder 106. A filter is built between the photodetector 103 and the lower surface of the photodetector holder 106. The radiation of the signal light is detected through a small hole (hole diameter ~2mm) on the lower surface of the photodetector holder 106. The filter removes stray light such as pump light and Raman light, retaining only the signal light. The photodetector 103 converts the detected light signal into a current signal. The current signal is converted into a voltage signal by the control unit. The voltage signal is converted into the required acquisition value by the control unit. The change of the acquired value is used to characterize the change of the actual output power of the laser.

[0119] Fifth, a temperature sensor 107 is embedded on the upper surface of the photodetector holder 106 to monitor the temperature change of the photodetector holder 106 in real time, so as to identify whether the scattered light generated by the two cladding light filters 102 will have a thermal effect on the photodetector 103. Since the photodetector 103 is sensitive to temperature changes, the change in dark current inside the photodetector 103 caused by temperature changes will affect the accuracy of the actual current of the photodetector 103 and cause a certain error in the test results.

[0120] Sixth, install the top cover 108. The top cover 108 of the device plays a sealing role, preventing external dust from entering the interior and adhering to the surface of the optical fiber 101, causing the optical fiber 101 to burn. In addition, it avoids interference from external light signals to the detection of the photodetector 103.

[0121] It should be noted that although several devices, units, or modules of the fiber laser power monitoring device have been mentioned in the detailed description above, this division is merely exemplary and not mandatory. In fact, according to embodiments of the present invention, the features and functions of two or more modules described above can be embodied in one module. Conversely, the features and functions of one module described above can be further divided and embodied by multiple modules.

[0122] Furthermore, although the operations of the fabrication method of the fiber laser power monitoring device of the present invention are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0123] While the spirit and principles of the invention have been described with reference to several specific embodiments, it should be understood that the invention is not limited to the disclosed specific embodiments, and the division of aspects does not imply that features in these aspects cannot be combined for benefit; such division is merely for ease of description. The invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0124] This invention provides:

[0125] 1. A fiber laser power monitoring device, characterized in that the device comprises: an optical fiber, a cladding optical filter, a photodetector, and a fixed structure; wherein...

[0126] The cladding light filter is located on both sides of the photodetector and is used to filter out the cladding light in the optical fiber;

[0127] The photodetector is used to detect signal light in the optical fiber;

[0128] The fixing structure is used to fix the optical fiber, the cladding optical filter and the photodetector into one unit.

[0129] 2. The monitoring device according to item 1, characterized in that the optical fiber includes a middle region and stripping regions at the left and right ends of the middle region, wherein the stripping regions are regions where the coating layer of the optical fiber is stripped.

[0130] The stripping area includes the fuzzy area and the non-fuzzy areas at both ends of the fuzzy area.

[0131] 3. The monitoring device according to item 2, characterized in that the degree of texturing of the inner cladding surface of the fiber in the texturing region is greater near the intermediate region than far from the intermediate region.

[0132] 4. The monitoring device according to item 3, characterized in that the degree of texturing of the inner cladding surface of the fiber in the texturing region decreases uniformly from a position near the middle region to a position far from the middle region.

[0133] 5. The monitoring device according to any one of items 2-4, characterized in that the length of the intermediate region is greater than 1 cm;

[0134] The length of the non-hairled region is greater than 0.5 cm.

[0135] 6. The monitoring device according to any one of items 2-4, characterized in that the roughened region is obtained by roughening the stripped region by means of an etching method using an etchant or a laser etching method.

[0136] 7. The monitoring device according to any one of items 1-4, wherein the optical fiber is a passive optical fiber;

[0137] The fiber core diameter / cladding diameter includes 20 / 250, 20 / 400, and 30 / 400.

[0138] 8. The monitoring device according to any one of items 2-4, wherein the cladding light filter includes the texturing region and the texturing region encapsulator.

[0139] 9. The monitoring device according to item 8, wherein the texturing region encapsulator is used to encapsulate the texturing region in a suspended manner;

[0140] Both ends of the texturing region encapsulator are fixed to the coating layer near the peeling opening.

[0141] 10. The monitoring device according to item 9, wherein the length of each of the texturing region encapsulators is longer than the length of the corresponding stripping region.

[0142] 11. The monitoring device according to item 8, wherein the textured area encapsulator is made of a transparent material with smooth inner and outer surfaces.

[0143] 12. The monitoring device according to item 8, characterized in that the bottom of the fixed structure includes a semi-circular groove for placing the integrated structure composed of the texturing region encapsulator after encapsulating the texturing region and the optical fiber.

[0144] 13. The monitoring device according to any one of items 1-4, characterized in that the device further includes a filter cover structure for encapsulating the cladding light filter to block the cladding light scattered by the cladding light filter.

[0145] 14. The monitoring device according to item 13, characterized in that the filter cover structure is a dark material with a rough surface.

[0146] 15. The monitoring device according to item 13 or 14, characterized in that the fixing structure is further used to receive the energy of the scattered cladding light absorbed by the filter covering structure;

[0147] The fixing structure is made of a dark-colored material with a rough surface.

[0148] 16. The monitoring device according to any one of items 1-4, wherein the photodetector is a photodiode.

[0149] 17. The monitoring device according to any one of claims 2-4, characterized in that the device further includes a photodetector holder located above the intermediate region.

[0150] 18. The monitoring device according to item 17, characterized in that the lower surface of the photodetector fixture and the upper surface of the fixing structure both include a semi-circular optical fiber groove, which together form an optical fiber groove;

[0151] The fiber optic slot is used to concentrate the radiation light generated by the signal light in the intermediate region inside it.

[0152] 19. The monitoring device according to item 18, wherein the surface of the fiber optic channel is treated with copper plating or gold plating polishing.

[0153] The fiber optic slot is spherical.

[0154] 20. The monitoring device according to item 18, wherein the diameter of the optical fiber slot is greater than the outer diameter of the optical fiber.

[0155] 21. The monitoring device according to item 18, characterized in that the surface of the photodetector holder is provided with small holes;

[0156] The photodetector is embedded above the photodetector holder and detects the radiation light generated by the signal light concentrated in the central region inside the fiber optic slot through the small hole.

[0157] 22. The monitoring device according to claim 21, characterized in that the device further includes a filter located between the photodetector and the photodetector holder for filtering out stray light other than the signal light.

[0158] 23. The monitoring device according to any one of items 1-4, characterized in that the device further includes a control unit;

[0159] The photodetector is also used to convert the detected optical signal into a current signal;

[0160] The control unit is used to convert the current signal into a sampled value to characterize the actual output power of the fiber laser.

[0161] 24. The monitoring device according to claim 17, characterized in that the device further includes a temperature sensor embedded in the upper surface of the photodetector fixture, for real-time monitoring of the temperature change of the photodetector fixture, so as to identify whether the scattered light generated by the cladding light filter affects the photodetector.

[0162] 25. The monitoring device according to any one of claims 1-4, characterized in that the device further includes a top cover for sealing the device to prevent the entry of external dust and / or external light signals.

[0163] 26. The monitoring device according to any one of items 1-4, characterized in that the fixing structure is a water-cooled plate.

[0164] 27. The monitoring device according to any one of items 1-4, characterized in that the numerical aperture of the optical fiber is 0.07 / 0.46.

[0165] 28. The monitoring device according to item 8, characterized in that the texturing region encapsulator includes a sandwich layer containing circulating coolant.

[0166] 29. A method for fabricating a fiber laser power monitoring device, characterized in that the device comprises: an optical fiber, a cladding optical filter, a photodetector, and a fixing structure; the method comprises:

[0167] The cladding light filter is disposed on both sides of the photodetector to filter out the cladding light in the optical fiber;

[0168] The optical detector is configured to detect the signal light in the optical fiber;

[0169] A fixed structure is used to fix the optical fiber, the cladding optical filter, and the photodetector into one unit.

[0170] 30. The preparation method according to item 29, characterized in that the cladding light filter includes the texturing region;

[0171] The specific steps of setting the cladding light filter on both sides of the photodetector to filter out the cladding light in the optical fiber include:

[0172] The coating layers at both ends of the middle region of the optical fiber are stripped to obtain the stripped area;

[0173] The middle section of the stripped area is roughened to obtain a roughened area;

[0174] By reserving a section of the area with the coating removed but not yet roughened at each end of the roughened area, a non-roughened area is obtained.

[0175] 31. The preparation method according to item 30, characterized in that the degree of texturing of the inner cladding surface of the fiber in the texturing region is greater near the intermediate region than far from the intermediate region.

[0176] 32. The preparation method according to item 31, characterized in that the degree of texturing of the inner cladding surface of the fiber in the texturing region decreases uniformly from a position near the intermediate region to a position far from the intermediate region.

[0177] 33. The preparation method according to any one of items 30-32, characterized in that the length of the intermediate region is greater than 1 cm;

[0178] The length of the non-hairled region is greater than 0.5 cm.

[0179] 34. The preparation method according to any one of items 30-32, characterized in that the step of texturing the middle section of the stripped region to obtain the texturized region specifically comprises:

[0180] The stripped area is roughened by etching with corrosive materials or by laser etching to obtain the roughened area.

[0181] 35. The preparation method according to any one of items 29-32, characterized in that the optical fiber is a passive optical fiber;

[0182] The fiber core diameter / cladding diameter includes 20 / 250, 20 / 400, and 30 / 400.

[0183] 36. The preparation method according to any one of items 30-32, characterized in that the cladding optical filter further includes a texturing region encapsulator;

[0184] The step of setting the cladding light filter on both sides of the photodetector to filter out the cladding light in the optical fiber further includes:

[0185] Configure the textured region encapsulator.

[0186] 37. The preparation method according to item 36, characterized in that the step of setting the texturing region encapsulator specifically comprises: fixing both ends of the texturing region encapsulator to the coating layer near the peeling port, so that the texturing region encapsulator suspends and encapsulates the texturing region.

[0187] 38. The preparation method according to item 37, characterized in that the length of each of the texturing region encapsulators is longer than the length of the corresponding stripping region.

[0188] 39. The preparation method according to item 36, characterized in that the texturized region encapsulator is made of a transparent material with smooth inner and outer surfaces.

[0189] 40. The preparation method according to item 36, characterized in that the bottom of the fixing structure includes a semi-circular groove;

[0190] The specific steps of setting up the fixing structure to fix the optical fiber, the cladding optical filter, and the photodetector into one unit include:

[0191] An integral structure consisting of a textured region encapsulator (after encapsulating the textured region) and the optical fiber is placed in the semi-circular groove.

[0192] 41. The preparation method according to any one of claims 29-32, characterized in that the apparatus further includes a filter cover structure;

[0193] The method further includes setting a filter cover structure to encapsulate the cladding light filter to block the cladding light scattered by the cladding light filter.

[0194] 42. The preparation method according to item 41, characterized in that the filter cover structure is a dark-colored material with a rough surface.

[0195] 43. The preparation method according to item 41 or 42, characterized in that the fixing structure is a dark-colored material with a rough surface;

[0196] The method further includes setting the fixed structure to receive the energy of the scattered cladding light absorbed by the filter cover structure.

[0197] 44. The preparation method according to any one of items 29-32, characterized in that the photodetector is a photodiode.

[0198] 45. The preparation method according to any one of items 30-32, characterized in that the device further includes a photodetector holder;

[0199] The method further includes positioning the photodetector holder above the intermediate region.

[0200] 46. ​​The preparation method according to item 45, characterized in that the method further includes engaging the lower surface of the photodetector fixture with the semi-circular fiber groove on the upper surface of the fixing structure to form a fiber groove, so as to concentrate the radiation light generated by the signal light in the intermediate region inside it.

[0201] 47. The preparation method according to item 46, characterized in that the surface of the optical fiber groove is treated with copper plating or gold plating polishing;

[0202] The fiber optic slot is spherical.

[0203] 48. The preparation method according to item 46, characterized in that the diameter of the optical fiber groove is larger than the outer diameter of the optical fiber.

[0204] 49. The preparation method according to item 46, characterized in that the step of setting the photodetector holder above the intermediate region specifically comprises: setting small holes on the surface of the photodetector holder;

[0205] The specific steps for setting up the photodetector to detect the signal light in the optical fiber are as follows:

[0206] The photodetector is embedded above the photodetector holder so that the photodetector can detect the radiation light generated by the signal light concentrated in the central region inside the fiber optic slot through the small hole.

[0207] 50. The preparation method according to item 49, characterized in that the method further includes placing a filter between the photodetector and the photodetector holder to filter out stray light other than the signal light.

[0208] 51. The preparation method according to any one of items 29-32, characterized in that the step of setting the photodetector to detect the signal light in the optical fiber specifically comprises:

[0209] The photodetector is configured to convert the detected light signal into a current signal;

[0210] The method also includes setting up a control unit to convert the current signal into a sampled value to characterize the actual output power of the fiber laser.

[0211] 52. The preparation method according to item 45, characterized in that the method further includes setting a temperature sensor embedded in the upper surface of the photodetector fixture to monitor the temperature change of the photodetector fixture in real time, thereby identifying whether the scattered light generated by the cladding light filter affects the photodetector.

[0212] 53. The preparation method according to any one of claims 29-32, characterized in that the method further includes providing a top cover to seal the device to prevent the entry of external dust and / or external light signals.

[0213] 54. The preparation method according to any one of items 29-32, characterized in that the fixing structure is a water-cooled plate.

[0214] 55. The preparation method according to any one of items 29-32, characterized in that the numerical aperture of the optical fiber is 0.07 / 0.46.

[0215] 56. The monitoring device according to claim 36, characterized in that the texturing region encapsulator includes a sandwich layer containing circulating coolant.

Claims

1. A fiber laser power monitoring device, characterized in that, The device includes: an optical fiber, a cladding optical filter, a photodetector, and a fixed structure; wherein... The optical fiber has an intermediate detection region and a first stripping region and a second stripping region located on both sides of the intermediate detection region. The first stripping region and the second stripping region have a roughness distribution that gradually decreases from near the intermediate detection region to both ends, so that the cladding light is preferentially and uniformly filtered out near the intermediate detection region, thereby avoiding the local heat accumulation in the intermediate detection region from affecting the detection accuracy of the Rayleigh scattering signal. The cladding light filter is located on both sides of the photodetector, respectively covering and disposed in the first stripping area and the second stripping area, and is used to filter out the cladding light in the optical fiber; The photodetector is positioned outside the intermediate detection region to detect Rayleigh scattering signal light that passes through the cladding and is scattered from the fiber core. The fixing structure is used to fix the optical fiber, the cladding optical filter, and the photodetector into a whole. The fixing structure includes a closed hollow spherical reflecting cavity formed by splicing symmetrical semi-circular grooves above and below the optical fiber. The inner wall of the hollow spherical reflecting cavity is used to allow Rayleigh scattered signal light to be reflected and diffusely reflected multiple times after entering the cavity, forming a uniform light field. A detection hole is provided on the hollow spherical reflecting cavity. The photodetector is fixed at the detection hole to receive part of the Rayleigh scattered signal light emitted through the detection hole. Based on the ratio of the aperture size of the detection hole to the total area of ​​the inner wall of the hollow spherical reflecting cavity, the total optical power of the Rayleigh scattered signal light in the hollow spherical reflecting cavity is calculated, thereby characterizing the output power of the fiber laser.

2. The monitoring device according to claim 1, characterized in that, The first and second stripping regions include a hairy region and non-hairy regions at the left and right ends of the hairy region.

3. The monitoring device according to claim 2, characterized in that, The degree of texturing on the inner cladding surface of the fiber in the texturing region is greater near the central region than far from the central region.

4. The monitoring device according to claim 3, characterized in that, The degree of texturing on the inner cladding surface of the fiber in the texturing region decreases uniformly from the position near the middle region to the position far away from the middle region.

5. The monitoring device according to any one of claims 2-4, characterized in that, The length of the intermediate region is greater than 1 centimeter; The length of the non-hairled region is greater than 0.5 cm.

6. The monitoring device according to any one of claims 2-4, characterized in that, The roughened region is obtained by roughening the stripped region through corrosion with an corrosive material or by laser etching.

7. The monitoring device according to any one of claims 1-4, characterized in that, The optical fiber is a passive optical fiber; The fiber core diameter / cladding diameter includes 20 / 250, 20 / 400, and 30 / 400.

8. The monitoring device according to any one of claims 2-4, characterized in that, The cladding light filter includes the texturing region and the texturing region encapsulator.

9. The monitoring device according to claim 8, characterized in that, The textured region encapsulator is used to encapsulate the textured region in a suspended manner. Both ends of the texturing region encapsulator are fixed to the coating layer near the peeling opening.

10. The monitoring device according to claim 9, characterized in that, The length of each of the texturing region encapsulators is longer than the length of the corresponding stripped region.

11. The monitoring device according to claim 8, characterized in that, The textured area encapsulator is made of a transparent material with smooth inner and outer surfaces.

12. The monitoring device according to claim 8, characterized in that, The bottom of the fixed structure includes a semi-circular groove for placing the texturing region encapsulator and the optical fiber, which together form an integrated structure.

13. The monitoring device according to any one of claims 1-4, characterized in that, The device also includes a filter cover structure for encapsulating the cladding light filter to block the cladding light scattered by the cladding light filter.

14. The monitoring device according to claim 13, characterized in that, The filter cover structure is made of a dark-colored material with a rough surface.

15. The monitoring device according to claim 13 or 14, characterized in that, The fixed structure is also used to receive the energy of the scattered cladding light absorbed by the filter cover structure; The fixing structure is made of a dark-colored material with a rough surface.

16. The monitoring device according to any one of claims 1-4, characterized in that, The photodetector is a photodiode.

17. The monitoring device according to any one of claims 2-4, characterized in that, The device also includes a photodetector holder located above the central region.

18. The monitoring device according to claim 17, characterized in that, The lower surface of the photodetector fixture and the upper surface of the fixing structure both include semi-circular fiber grooves, which together form fiber grooves. The fiber optic slot is used to concentrate the radiation light generated by the signal light in the intermediate region inside it.

19. The monitoring device according to claim 18, characterized in that, The surface of the fiber optic groove is treated with copper plating or gold plating and polishing. The fiber optic slot is spherical.

20. The monitoring device according to claim 18, characterized in that, The diameter of the fiber slot is larger than the outer diameter of the fiber.

21. The monitoring device according to claim 18, characterized in that, The surface of the photodetector holder is provided with small holes; The photodetector is embedded above the photodetector holder and detects the radiation light generated by the signal light concentrated in the central region inside the fiber optic slot through the small hole.

22. The monitoring device according to claim 21, characterized in that, The device also includes a filter located between the photodetector and the photodetector holder for filtering out stray light other than the signal light.

23. The monitoring device according to any one of claims 1-4, characterized in that, The device also includes a control unit; The photodetector is also used to convert the detected optical signal into a current signal; The control unit is used to convert the current signal into a sampled value to characterize the actual output power of the fiber laser.

24. The monitoring device according to claim 17, characterized in that, The device also includes a temperature sensor embedded in the upper surface of the photodetector holder, used to monitor the temperature change of the photodetector holder in real time, so as to identify whether the scattered light generated by the cladding light filter affects the photodetector.

25. The monitoring device according to any one of claims 1-4, characterized in that, The device also includes a top cover for sealing the device and preventing the entry of external dust and / or external light signals.

26. The monitoring device according to any one of claims 1-4, characterized in that, The fixed structure is a water-cooled plate.

27. The monitoring device according to any one of claims 1-4, characterized in that, The numerical aperture of the optical fiber is 0.07 / 0.

46.

28. The monitoring device according to claim 8, characterized in that, The texturized area encapsulator includes a sandwich layer containing circulating coolant.

29. A method for fabricating a fiber laser power monitoring device, characterized in that, The apparatus includes: an optical fiber, a cladding optical filter, a photodetector, and a fixed structure; the method includes: An intermediate detection area and a first stripping area and a second stripping area located on both sides of the intermediate detection area are provided in the middle of the optical fiber. The first and second stripping areas are roughened to form a surface roughness distribution that gradually decreases from near the middle detection area to both ends. This allows the cladding light to be preferentially and uniformly filtered out near the middle detection area, thereby avoiding local heat accumulation in the middle detection area from affecting the detection accuracy of the Rayleigh scattering signal. The cladding light filter is disposed on both sides of the photodetector, respectively covering and disposed in the first stripping area and the second stripping area, to filter out the cladding light in the optical fiber; The photodetector is positioned outside the intermediate detection region to detect Rayleigh scattering signal light that passes through the cladding and is scattered from the fiber core. A fixed structure is used to fix the optical fiber, the cladding optical filter, and the photodetector into a single unit. The fixed structure includes a closed hollow spherical reflecting cavity formed by splicing symmetrical semi-circular grooves above and below the optical fiber. The inner wall of the hollow spherical reflecting cavity is used to allow Rayleigh scattered signal light to be reflected and diffusely reflected multiple times after entering the cavity, forming a uniform light field. A detection hole is provided on the hollow spherical reflecting cavity, and the photodetector is fixed at the detection hole to receive part of the Rayleigh scattered signal light emitted through the detection hole. Based on the ratio of the aperture size of the detection hole to the total area of ​​the inner wall of the hollow spherical reflecting cavity, the total optical power of the Rayleigh scattered signal light in the hollow spherical reflecting cavity is calculated, thereby characterizing the output power of the fiber laser.

30. The preparation method according to claim 29, characterized in that, The cladding light filter includes the texturing region; The specific steps of setting the cladding light filter on both sides of the photodetector to filter out the cladding light in the optical fiber include: The coating layers at both ends of the middle region of the optical fiber are stripped to obtain the stripped area; The middle section of the stripped area is roughened to obtain a roughened area; By reserving a section of the area with the coating removed but not yet roughened at each end of the roughened area, a non-roughened area is obtained.

31. The preparation method according to claim 30, characterized in that, The degree of texturing on the inner cladding surface of the fiber in the texturing region is greater near the central region than far from the central region.

32. The preparation method according to claim 31, characterized in that, The degree of texturing on the inner cladding surface of the fiber in the texturing region decreases uniformly from the position near the middle region to the position far away from the middle region.

33. The preparation method according to any one of claims 30-32, characterized in that, The length of the intermediate region is greater than 1 centimeter; The length of the non-hairled region is greater than 0.5 cm.

34. The preparation method according to any one of claims 30-32, characterized in that, The specific steps for roughening the middle section of the stripped area to obtain the roughened area are as follows: The stripped area is roughened by etching with corrosive materials or by laser etching to obtain the roughened area.

35. The preparation method according to any one of claims 29-32, characterized in that, The optical fiber is a passive optical fiber; The fiber core diameter / cladding diameter includes 20 / 250, 20 / 400, and 30 / 400.

36. The preparation method according to any one of claims 30-32, characterized in that, The cladding optical filter also includes a texturing region encapsulator; The step of setting the cladding light filter on both sides of the photodetector to filter out the cladding light in the optical fiber further includes: Configure the textured region encapsulator.

37. The preparation method according to claim 36, characterized in that, The specific steps for setting the textured region encapsulator are as follows: fix both ends of the textured region encapsulator to the coating layer near the peeling port, so that the textured region encapsulator suspends and encapsulates the textured region.

38. The preparation method according to claim 37, characterized in that, The length of each of the texturing region encapsulators is longer than the length of the corresponding stripped region.

39. The preparation method according to claim 36, characterized in that, The textured area encapsulator is made of a transparent material with smooth inner and outer surfaces.

40. The preparation method according to claim 36, characterized in that, The bottom of the fixing structure includes a semi-circular groove; The specific steps of setting up the fixing structure to fix the optical fiber, the cladding optical filter, and the photodetector into one unit include: An integral structure consisting of a textured region encapsulator (after encapsulating the textured region) and the optical fiber is placed in the semi-circular groove.

41. The preparation method according to any one of claims 29-32, characterized in that, The device also includes a filter cover structure; The method further includes setting a filter cover structure to encapsulate the cladding light filter to block the cladding light scattered by the cladding light filter.

42. The preparation method according to claim 41, characterized in that, The filter cover structure is made of a dark-colored material with a rough surface.

43. The preparation method according to claim 41 or 42, characterized in that, The fixing structure is made of a dark-colored material with a rough surface; The method further includes setting the fixed structure to receive the energy of the scattered cladding light absorbed by the filter cover structure.

44. The preparation method according to any one of claims 29-32, characterized in that, The photodetector is a photodiode.

45. The preparation method according to any one of claims 30-32, characterized in that, The device also includes a photodetector holder; The method further includes positioning the photodetector holder above the intermediate region.

46. ​​The preparation method according to claim 45, characterized in that, The method further includes engaging the lower surface of the photodetector fixture with the semi-circular fiber optic groove on the upper surface of the fixing structure to form a fiber optic groove, thereby concentrating the radiation light generated by the signal light in the intermediate region within it.

47. The preparation method according to claim 46, characterized in that, The surface of the fiber optic groove is treated with copper plating or gold plating and polishing. The fiber optic slot is spherical.

48. The preparation method according to claim 46, characterized in that, The diameter of the fiber slot is larger than the outer diameter of the fiber.

49. The preparation method according to claim 46, characterized in that, The specific step of setting the photodetector holder above the middle region is as follows: setting small holes on the surface of the photodetector holder; The specific steps for setting up the photodetector to detect the signal light in the optical fiber are as follows: The photodetector is embedded above the photodetector holder so that the photodetector can detect the radiation light generated by the signal light concentrated in the central region inside the fiber optic slot through the small hole.

50. The preparation method according to claim 49, characterized in that, The method further includes placing a filter between the photodetector and the photodetector holder to filter out stray light other than the signal light.

51. The preparation method according to any one of claims 29-32, characterized in that, The specific steps for setting up the photodetector to detect the signal light in the optical fiber are as follows: The photodetector is configured to convert the detected light signal into a current signal; The method also includes setting up a control unit to convert the current signal into a sampled value to characterize the actual output power of the fiber laser.

52. The preparation method according to claim 45, characterized in that, The method further includes setting a temperature sensor embedded in the upper surface of the photodetector fixture to monitor the temperature change of the photodetector fixture in real time, thereby identifying whether the scattered light generated by the cladding light filter affects the photodetector.

53. The preparation method according to any one of claims 29-32, characterized in that, The method also includes providing a top cover to seal the device and prevent the entry of external dust and / or external light signals.

54. The preparation method according to any one of claims 29-32, characterized in that, The fixed structure is a water-cooled plate.

55. The preparation method according to any one of claims 29-32, characterized in that, The numerical aperture of the optical fiber is 0.07 / 0.

46.

56. The monitoring device according to claim 36, characterized in that, The texturized area encapsulator includes a sandwich layer containing circulating coolant.

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