Optical fiber laser power monitoring apparatus and preparation method therefor

Abstract

Provided in the present invention are an optical fiber laser power monitoring apparatus and a preparation method therefor. The apparatus comprises: an optical fiber, cladding light filters, an optical detector and a fixing structure, wherein the cladding light filters are located on two sides of the optical detector, and are used for filtering out cladding light from the optical fiber; the optical detector is used for detecting signal light in the optical fiber; and the fixing structure is used for fixing the optical fiber, the cladding light filters and the optical detector together. The monitoring apparatus of the present invention eliminates the effect of cladding light and other interference factors, thereby effectively realizing accurate monitoring of the power of an optical fiber laser.

Description

Optical fiber laser power monitoring device and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of laser, in particular to an optical fiber laser power monitoring device and a preparation method thereof. BACKGROUND

[0002] At present, the output power of optical fiber laser is constantly increasing and is widely used in various fields such as life, industry and military. In fine processing, the stability of the output power of the optical fiber laser has a key influence on the processing effect. In fact, due to the influence of the pump source wave drift caused by the temperature change in the working environment, the thermal lens effect of the active optical fiber itself, the long-term stability of the passive optical device and the like, the output power of the optical fiber laser is usually unstable. In the extreme case, if the internal optical device of the optical fiber laser is damaged, the problem cannot be found in time by judging only the actual processing effect, which will lead to further deterioration of the optical assembly and even cause destructive failure of the entire optical path, resulting in huge losses. Therefore, how to monitor the output power of the optical fiber laser in real time and accurately, effectively prevent failure risk, and at the same time adjust the output power of the laser to keep it in a relatively stable range to meet the needs of precision machining, is a key technology for domestic high-power optical fiber lasers to enter the high-end product market.

[0003] For optical fiber lasers with all-optical fiber structure, using a fiber optical splitter to monitor the output power is a common means, as proposed in patent CN115411595A. By reasonably controlling the splitting ratio of the splitter, the splitting power can accurately reflect the dynamic changes of the laser output power. However, the signal tolerance power of the fiber optical splitter is limited, and adding an optical fiber device on the laser link will also bring additional insertion loss and failure risk. It is generally used for low-power optical fiber lasers and is not suitable for power online monitoring of high-power optical fiber lasers. At present, for high-power optical fiber lasers, there are two common power monitoring methods:

[0004] 1. Pump monitoring method, by monitoring the actual output power and actual temperature of the pump source, adjusting the pump current and pump temperature according to the target power value and target temperature value, to adjust the output power of the optical fiber laser, to compensate and calibrate the output power in real time. However, considering the long-term stability of other devices in the optical path, there is no clear correspondence between the pump power and the actual laser output power, which can only be used as a reference.

[0005] 2. Monitoring the intensity of cladding light scattered by the cladding light filter to monitor the output power of the laser, as shown in FIG. 1, the photodetector detects the cladding light scattered by the cladding light filter. The disadvantages of this method are: a. After the fiber laser works for a long time, factors such as photon darkening, mode instability, and heat-induced defects in the gain fiber will cause the cladding light in the fiber to increase and the signal light to decrease, and simply monitoring the change of the cladding light cannot truly reflect the actual situation of the laser power; b. For high-power fiber lasers, the cladding light scattered by the cladding light filter has high power, and the photodiode is prone to heat, and the influence of temperature change on the dark current will reduce the accuracy of the photodiode in detecting the light signal, and also affect the service life of the photodiode; c. In actual processing, especially when processing high-reflectivity materials, part of the back reflection light on the material surface will enter the fiber cladding, which will interfere with the detection results of the photodiode.

[0006] SUMMARY

[0007] The present application provides a fiber laser power monitoring device and its preparation method, which aims 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 light filter, and a fixing structure. The gradual roughening method of the cladding light filter ensures uniform heat dissipation and prevents local overheating, thereby preventing fiber damage and enhancing the long-term reliability of the device. The device characterizes the actual output power by detecting the change in the radiation intensity of the core signal light, thereby providing real-time monitoring and adjustment.

[0008] In a first aspect, the present application provides a fiber laser power monitoring device, characterized in that the device comprises an optical fiber, a cladding light filter, a photodetector, and a fixing structure; wherein

[0009] The cladding light filter is located on both sides of the photodetector and is used to filter the cladding light in the optical fiber;

[0010] The photodetector is used to detect the signal light in the optical fiber;

[0011] The fixing structure is used to fix the optical fiber, the cladding light filter, and the photodetector as a whole.

[0012] In a second aspect, the present application further provides a preparation method of a fiber laser power monitoring device, characterized in that the device comprises an optical fiber, a cladding light filter, a photodetector, and a fixing structure; the method comprises:

[0013] The cladding light filter is located on both sides of the photodetector to filter the cladding light in the optical fiber;

[0014] The photodetector is used to detect the signal light in the optical fiber;

[0015] The fixed structure is arranged to fix the optical fiber, the cladding light filter and the light detector as a whole.

[0016] The fiber laser power monitoring device and the preparation method thereof provided by the application avoid the interference of cladding light generated during the internal and external processing of the laser on the detection of signal light, have high power monitoring precision, a gradual roughening cladding light filtering method, uniform heat dissipation, high long-term reliability, and can be used for the power online monitoring of high-power fiber lasers; the accurate power online monitoring can be used for the adaptive adjustment of laser output power, and the control unit can automatically compensate the pump driving with appropriate current according to the real-time feedback of the laser power to control the stability of the fiber laser output power, thereby ensuring the consistency of the actual processing effect; the fiber laser power online monitoring device of the application has simple structure and is easy to operate, and is suitable for engineering and product application. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0018] Fig. 1 is a schematic diagram of a power online monitoring device in the prior art;

[0019] Fig. 2 is a schematic diagram of a fiber laser power monitoring device provided by an embodiment of the application;

[0020] Fig. 3 is a schematic diagram of another fiber laser power monitoring device provided by an embodiment of the application;

[0021] Fig. 4 is a graph showing the changes of the actual output power of the fiber laser and the acquisition value of the power monitoring device with time;

[0022] Fig. 5 is a graph showing the error between the feedback laser power and the corresponding actual output power of the fiber laser with the feedback laser power in four times of measurement provided by an embodiment of the application;

[0023] Fig. 6 is a flow chart of the preparation method of the fiber laser power monitoring device provided by an embodiment of the application. DETAILED DESCRIPTION

[0024] The technical solutions of the application will be further described in detail below with the drawings and embodiments.

[0025] SUMMARY

[0026] The application provides a fiber laser power monitoring device and a preparation method thereof.

[0027] Exemplary device

[0028] Figure 2 is a schematic diagram of the fiber laser power monitoring device provided by the embodiment of the application. As shown in Figure 2, the device 100 provided by the embodiment includes a fiber 101, a cladding light filter 102, a light detector 103, and a fixing structure 104.

[0029] The fixing structure 104 is used to fix the fiber 101, the cladding light filter 102, and the light detector 103 as a whole.

[0030] The fiber 101 is a passive fiber, which is only used for transmitting optical signals and does not perform optical amplification. For example, a double-clad passive fiber or a triple-clad passive fiber.

[0031] The core diameter / cladding diameter of the fiber 101 includes but is not limited to 20 / 250, 20 / 400, and 30 / 400.

[0032] The fiber 101 includes a middle region and stripping regions at left and right ends of the middle region.

[0033] The length of the middle region is greater than 1 cm.

[0034] The stripping regions are regions where the coating layer of the fiber 101 is stripped, and each stripping region includes a roughened region and non-roughened regions at left and right ends of the roughened region. The roughened region is used to absorb cladding light.

[0035] The roughened region is obtained by roughening the stripping region through a material corrosion method or a laser etching method. For example, the stripping region is wiped clean with alcohol, and then roughened by using a frosting paste or other etching liquid or a laser etching method, so as to remove residual cladding light.

[0036] The non-roughened regions at the left and right ends play a transition role, which prevents the middle region from being burned due to structural mutation between the roughened region and the complete coating layer, and reduces the risk of fiber damage. Each roughened region is provided with a non-roughened region with a length greater than 0.5 cm at each left and right end.

[0037] The cladding light filter 102 is located on both sides of the light detector 103, and is used to filter cladding light in the fiber 101.

[0038] The cladding light filter 102 includes the roughened region and a roughened region encapsulator.

[0039] The roughness of the inner cladding surface of the roughened region is greater near the middle region than away from the middle region.

[0040] Preferably, the roughness of the inner cladding surface of the roughened region decreases uniformly from the position near the middle region to the position away from the middle region. That is, the roughness of the inner cladding surface increases uniformly from the input end to the output end of the cladding light, so that the cladding light is absorbed uniformly, avoiding the rapid increase of local temperature due to the sudden change of the cladding structure of the optical fiber, achieving the effect of uniform temperature rise of the cladding light filter 102 as a whole. The gradual roughening directions of the left and right roughened regions are opposite, the roughness of the left roughened region increases from the input end to the output end of the forward laser, and the roughness of the right roughened region decreases from the input end to the output end of the forward laser. The left roughened region is used to filter the residual cladding light carried by the front-end laser, and the right roughened region is mainly used to filter the cladding light returned to the inside of the optical fiber from the surface of the workpiece during processing.

[0041] In summary, the cladding light is gradually weakened instead of being suddenly absorbed in large quantities, which leads to rapid accumulation of local heat. If the surface of the roughened region is uniformly roughened, too much heat will be generated in the area where the cladding light begins to leak, causing damage to the optical fiber. By gradually increasing the roughness, the cladding light inside the entire optical fiber is uniformly and effectively filtered, ensuring the long-term stable operation of the optical fiber and reducing the interference and damage caused by the cladding light, thereby improving the power monitoring accuracy and reliability of the high-power fiber laser.

[0042] The roughened region encapsulator is used to suspend the roughened region, preventing dust from adhering to the roughened region and causing the optical fiber to burn out. In order to ensure that the entire stripped region is protected, the length of each roughened region encapsulator is longer than the length of the corresponding stripped region.

[0043] The roughened region encapsulator is made of transparent and smooth material. The transparent material ensures that the leaked cladding light can be transmitted to the filter covering structure 105, so that the filter covering structure 105 can absorb the cladding light. The smooth surface can prevent contaminants from adhering to the roughened region encapsulator, reducing the risk of contamination of the roughened region.

[0044] The roughened region encapsulator can also include a sandwich layer with circulating cooling liquid for absorbing cladding light and cooling the roughened region encapsulator. The color of the circulating cooling liquid is complementary to the color of the laser in the optical fiber 101. For example, if the wavelength of the laser is 630 nm, a green cooling liquid is selected. The circulating cooling liquid is driven by a pump, and the flow direction of the cooling liquid is shown by the arrows below in FIG. 2, flowing from both sides of the optical fiber 101 to the middle region of the optical fiber 101, for efficient cooling of the roughened region encapsulator.

[0045] The two ends of the roughened region encapsulator are fixed on the coating near the stripping port to prevent displacement or falling off during use, for example, using glue or other fixing materials.

[0046] The bottom of the fixing structure 104 includes a semicircular groove for placing the integrated structure of the roughened region encapsulator after encapsulating the roughened region and the optical fiber 101.

[0047] For example, the roughened region encapsulator uses glass tubes, and the two roughened regions are suspended in the middle of the two glass tubes. The two ends of the glass tubes are fixed with glue, and the glue is applied to the coating near the middle region stripping port. After the glass tube encapsulation is completed, the optical fiber glass tube integrated piece is placed in the semicircular groove at the bottom of the fixing structure 104, and the left glass tube is located at the input end of the device 100. The two ends of the two glass tubes are fixed with glue to the groove.

[0048] The device 100 also includes a filter cover structure 105 for encapsulating the cladding light filter 102 to shield the cladding light scattered by the cladding light filter 102, avoiding the influence of irregularly scattered cladding light on the detection results of the light detector.

[0049] In order to reduce the reflection and scattering of light, the filter cover structure 105 is a rough-surfaced dark material that can absorb most of the scattered light of the cladding light filter 102 and convert it into heat, which is then carried away by the external heat sink through the fixing structure 104. That is, the fixing structure 104 not only supports and fixes the filter cover structure 105, but also receives the energy of the scattered cladding light absorbed by the filter cover structure 105. The fixing structure 104 is also a rough-surfaced dark material, further reducing the interference of internal scattered cladding light on the light detector 103, maintaining the accuracy of the measurement and the stability of the system.

[0050] For example, the filter cover structure 105 and / or the fixing structure 104 can be black anodized to make the material surface rougher and have light absorption properties, thereby improving its ability to absorb scattered light and enhancing the heat dissipation efficiency.

[0051] The light detector 103 is used to detect the signal light in the optical fiber 101. For example, the light detector 103 is a photodiode that detects signal light by detecting radiation inside the fiber core of the optical fiber 101.

[0052] The device 100 also includes a light detector fixer 106 located above the middle region.

[0053] The lower surface of the light detector holder 106 and the upper surface of the fixing structure 104 both comprise semicircular fiber grooves, which are precisely aligned and cooperated to form a complete fiber groove with a diameter slightly larger than the outer diameter of the fiber 101 to avoid damaging the fiber 101.

[0054] The fiber groove is spherical to ensure that the radiation light generated by the signal light in the fiber 101 is concentrated in the fiber groove, facilitating accurate detection of the light detector 103.

[0055] Preferably, the surface of the fiber groove can be treated with copper or gold plating and polishing, or coated with a high-reflectivity material to enhance the reflection of the radiation light on the surface of the fiber groove, avoiding instability of the optical signal detection due to weak radiation light.

[0056] That is, the fiber groove is a hollow sphere with high reflectivity inside. After the light enters the sphere, it is reflected and diffused multiple times on the inner wall to form a uniform light field. Due to the high reflectivity and diffuse reflection characteristics of the inner wall, the light is uniformly distributed in the sphere, so that the luminance at any point on the sphere wall is equal, which ensures the accuracy and stability of the measurement results. By measuring the light energy of a small area on the inner wall of the fiber groove, the total light energy emitted by the light source can be calculated.

[0057] The surface of the light detector holder 106 is provided with a small hole, for example, with a diameter of about 2 mm.

[0058] The light detector 103 is embedded above the light detector holder 106 and detects the radiation light generated by the signal light in the middle area concentrated inside the fiber groove through the small hole.

[0059] When there is strong pump residual light or Raman scattered light and other unnecessary stray light in the fiber 101, in order to avoid the interference of these stray light with the light detector 103 affecting the accurate detection of the output power, the device 100 further comprises a filter between the light detector 103 and the light detector holder 106 for filtering out stray light other than signal light.

[0060] The device 100 further comprises a control unit, and the light detector 103 is further used to convert the detected optical signal into a current signal, and the control unit is used to convert the current signal into a collection value to represent 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, and the voltage signal is converted into the required collection value by the data processing of the control unit, and the change of the collection value represents the change of the actual output power of the fiber laser.

[0061] When the cladding light in the optical fiber 101 is strong, the device 100 further comprises a temperature sensor 107 embedded in the upper surface of the light detector holder 106 for real-time monitoring of the temperature change of the light detector holder 106 to determine whether the temperature of the light detector 103 fluctuates. The light detector 103 is sensitive to temperature change, and the change of the dark current inside the light detector 103 caused by the temperature change will affect the actual photocurrent signal and cause certain error to the test result. The temperature fluctuation detected by the temperature sensor 107 can be used to calibrate the detection value of the light detector 103. That is, whether the scattered light generated by the two sections of the cladding light filter 102 affects the light detector 103 is identified.

[0062] The device 100 further comprises a cover 108 for sealing the device 100 to avoid external dust from entering the inside and adhering to the surface of the optical fiber 101 to cause fiber burn, and / or to avoid the interference of external light signal to the detection of the light detector 103.

[0063] In summary, the entire optical fiber laser power monitoring device 100 represents the actual output power of the signal light by detecting the intensity change of the radiated light of the core signal light, reduces the interference of the cladding light generated during the internal and external processing of the optical fiber laser to the detection, and considers the influence of the temperature change on the detection of the light detector 103. The accuracy and long-term reliability of the power monitoring are greatly improved, and the device 100 can be used for online monitoring of the power of high-power optical fiber lasers, and the device 100 has simple structure and is easy to operate, which is suitable for engineering and product application.

[0064] As an optional embodiment, a 3500W fiber laser with a high-power fiber laser power online monitoring device is provided. The power online monitoring device is shown in Fig. 3, which is located at the output end of the fiber laser optical path structure. In order to reduce the thermal influence of the two-section cladding light filter 102 on the photodetector 103, the fixed structure 104 is a water-cooled plate in this embodiment, and the two-section cladding light filter 102 is directly placed in the groove on the water-cooled plate, which simplifies the structure of the upper cover 108. The used fiber 101 is a double-clad passive optical fiber, with a core diameter / cladding diameter of 20 / 250, a numerical aperture of 0.07 / 0.46, and a stripping area of 8 cm on both sides. After the stripping area is cleaned with alcohol, a glass frosting paste is used for frosting. The frosting degree of the inner cladding surface of the frosting area uniformly decreases from the position close to the middle area to the position away from the middle area. Each of the left and right ends of each frosting area is reserved 0.51 cm without frosting, i.e., each of the non-frosting areas is 0.51 cm. The frosting area packaging device 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. Fig. 4 shows the changes of the actual output power and the collected value of the fiber laser within 53 min. The periodic change of the actual output power is caused by the fluctuation of the water temperature, and the collected value makes a periodic feedback accordingly, which is consistent with the change of the actual output power. According to the corresponding relationship between the collected value and the laser power, the corresponding formula is fixed to the control unit through data processing. The size of the laser power can be automatically and real-time fed back according to the collected value. Fig. 5 shows the error between the actual output power and the feedback laser power corresponding to the four times of re-measurement of the fiber laser. From low power to high power, the error between them is basically controlled at about 1%, and the feedback laser power can accurately represent the size of the actual output power.

[0065] Exemplary methods

[0066] Correspondingly, the embodiment of the present application also provides a preparation method of the fiber laser power monitoring device 100. The device 100 comprises a fiber 101, a cladding light filter 102, a photodetector 103 and a fixed structure 104. Fig. 6 is a flow chart of the preparation method of the fiber laser power monitoring device 100 provided by the embodiment of the present application, which comprises the following steps:

[0067] S601: The cladding light filter 102 is arranged on both sides of the photodetector 103 to filter the cladding light in the fiber 101.

[0068] S602: The photodetector 103 is arranged to detect the signal light in the fiber 101.

[0069] S603: The fixed structure 104 is arranged to fix the fiber 101, the cladding light filter 102 and the photodetector 103 as a whole.

[0070] The cladding light filter 102 comprises the roughened region.

[0071] The step of disposing the cladding light filter 102 on both sides of the light detector 103 to filter the cladding light in the optical fiber 101 specifically comprises:

[0072] Stripping the coating layers on both ends of the middle region of the optical fiber 101 to obtain a stripped region;

[0073] Roughening the middle section of the stripped region to obtain a roughened region;

[0074] Reserving a section of the stripped coating layer on both ends of the roughened region which has not been roughened to obtain a non-roughened region.

[0075] The roughening degree of the inner cladding surface of the roughened region is greater near the middle region than far from the middle region.

[0076] The roughening degree of the inner cladding surface of the roughened region decreases uniformly from near the middle region to far from the middle region.

[0077] The length of the middle region is greater than 1 cm;

[0078] The length of the non-roughened region is greater than 0.5 cm.

[0079] The step of roughening the middle section of the stripped region to obtain a roughened region specifically comprises:

[0080] The roughened region is obtained by roughening the stripped region through a corrosion material corrosion method or a laser etching method.

[0081] The optical fiber 101 is a passive optical fiber;

[0082] The core / cladding diameter of the optical fiber 101 comprises 20 / 250, 20 / 400, 30 / 400.

[0083] The cladding light filter 102 further comprises a roughened region encapsulator;

[0084] The step of disposing the cladding light filter 102 on both sides of the light detector 103 to filter the cladding light in the optical fiber 101 specifically further comprises:

[0085] The roughened region encapsulator is disposed.

[0086] The step of disposing the roughened region encapsulator specifically comprises: fixing both ends of the roughened region encapsulator on the coating layers near the stripping openings, so that the roughened region encapsulator suspends and encapsulates the roughened region.

[0087] Each of the roughened region encapsulator is longer than the length of the corresponding stripped region.

[0088] The roughened region encapsulator is made of transparent material with smooth inner and outer surfaces.

[0089] The roughened region encapsulator can further comprise a sandwich layer with circulating coolant for absorbing the cladding light and cooling the roughened region encapsulator. The circulating coolant is of a color that is complementary to the color of the laser light in the optical fiber 101.

[0090] The bottom of the fixing structure 104 comprises a semicircular groove;

[0091] The step of fixing the optical fiber 101, the cladding light filter 102 and the light detector 103 as a whole by the fixing structure 104 specifically comprises:

[0092] Placing the whole structure composed of the roughened region encapsulator encapsulating the roughened region and the optical fiber 101 in the semicircular groove.

[0093] The device 100 further comprises a filter covering structure 105;

[0094] The method further comprises setting the filter covering structure 105 to encapsulate the cladding light filter 102 to shield the cladding light scattered by the cladding light filter 102.

[0095] The filter covering structure 105 is made of dark material with rough surface.

[0096] The fixing structure 104 is made of dark material with rough surface;

[0097] The method further comprises setting the fixing structure 104 to also receive the energy of the scattered cladding light absorbed by the filter covering structure 105.

[0098] The light detector 103 is a photodiode.

[0099] The device 100 further comprises a light detector fixer 106;

[0100] The method further comprises setting the light detector fixer 106 above the middle region.

[0101] The method further comprises matching the lower surface of the light detector fixer 106 with the semicircular fiber groove on the upper surface of the fixing structure 104, so that the two form a fiber groove to concentrate the radiation light generated by the signal light in the middle region inside.

[0102] The surface of the fiber groove is treated with copper or gold plating and polishing;

[0103] The fiber groove is spherical.

[0104] The fiber groove has a diameter larger than the outer diameter of the fiber 101.

[0105] The step of disposing the photodetector holder 106 above the middle region specifically comprises: disposing a small hole on the surface of the photodetector holder 106;

[0106] The step of disposing the photodetector 103 to detect the signal light in the fiber 101 specifically comprises:

[0107] The step of disposing the photodetector 103 above the photodetector holder 106 so that the photodetector 103 detects the radiation light generated by the signal light in the middle region inside the fiber groove through the small hole.

[0108] The method further comprises disposing a filter between the photodetector 103 and the photodetector holder 106 to filter out stray light other than the signal light.

[0109] The step of disposing the photodetector 103 to detect the signal light in the fiber 101 specifically comprises:

[0110] The step of disposing the photodetector 103 to convert the detected light signal into a current signal;

[0111] The method further comprises disposing a control unit to convert the current signal into a collection value to represent the actual output power of the fiber laser.

[0112] The method further comprises disposing a temperature sensor 107 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 cladding light filter 102 affects the photodetector 103.

[0113] The method further comprises disposing a cover 108 to seal the device 100 to prevent the entry of external dust and / or external light signals.

[0114] The fixing structure 104 is a water-cooled plate.

[0115] The numerical aperture of the fiber 101 is 0.07 / 0.46.

[0116] As an optional embodiment, the specific preparation method is as follows: first, a double-clad passive optical fiber 101 such as 20 / 250, 20 / 400, 30 / 400, etc. is taken, and the coating layer is removed at both sides of the middle position of the optical fiber 101, and the middle of the optical fiber 101 is reserved for more than 1 cm without being removed. The removed area is cleaned with alcohol, and then is roughened by etching liquid such as glass frosting paste or laser etching method, etc. to remove residual cladding light. The left and right ends of the removed coating layer are each reserved for more than 0.5 cm without roughening. A gradual roughening method is adopted, 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, so as to uniformly absorb the cladding light, avoid the rapid rise of local temperature caused by the sudden change of the cladding structure of the optical fiber 101 at the front end, and achieve the effect of uniform temperature rise of the whole cladding light filter 102.

[0117] Second, after the double-clad optical fiber 101 is roughened, glass tubes are used as roughened area packaging devices to package the roughened areas to prevent dust from adhering to the roughened areas and causing the optical fiber 101 to burn. The glass tubes are longer than the removed coating layer, and the two roughened areas are respectively placed in the middle of the two glass tubes. The two ends of the glass tubes are respectively fixed by glue, and the glue is applied on the coating layer near the removed coating layer. After the glass tube packaging is completed, the optical fiber glass tube integral part is placed in the semicircular groove at the bottom of the device fixing structure 104. The left segment cladding light filter 102 is located at the input end of the device, and the two ends of the two glass tubes are respectively fixed in the groove by glue.

[0118] Third, the filter covering structure 105 is used to block the cladding light scattered by the cladding light filter 102, so as to avoid the influence of the irregularly scattered cladding light on the detection result of the light detector 103. The filter covering structure 105 is subjected to black anodizing treatment, can absorb most of the scattered light of the cladding light filter 102 and convert it into heat, which is then taken away by the external heat sink of the fixing structure 104. The fixing structure 104 can also be subjected to black anodizing, further reducing the uncertainty caused by the internal scattered cladding light.

[0119] Fourthly, the optical detector fixer 106 is placed above the middle region of the optical fiber 101 between the two cladding light filters 102. The middle upper surface of the fixing structure 104 and the lower surface of the optical detector fixer 106 are both engraved with semicircular optical fiber grooves, which are matched with each other and slightly larger than the outer diameter of the double-clad optical fiber 101 to avoid the double-clad optical fiber 101 being pressed and to ensure that the radiation light generated by the signal light in the double-clad optical fiber 101 is concentrated in the optical fiber groove. The surface of the optical fiber groove is plated with copper or gold and polished to enhance the reflection of the radiation light on the groove surface and avoid the instability of the optical signal detection due to the weak radiation light. The optical detector 103 is embedded above the optical detector fixer 106. The optical detector 103 and the lower surface of the optical detector fixer 106 are provided with a filter. The radiation light of the signal light is detected through the small hole (with a diameter of about 2 mm) on the lower surface of the optical detector fixer 106. The filter filters out the stray light such as the pump light and the Raman light and only retains the signal light. The optical detector 103 converts the detected optical 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 collection value by the control unit. The change of the collected collection value represents the change of the actual output power of the laser.

[0120] Fifthly, the temperature sensor 107 is embedded on the upper surface of the optical detector fixer 106 to monitor the temperature change of the optical detector fixer 106 in real time to identify whether the scattered light generated by the two cladding light filters 102 will cause a thermal effect on the optical detector 103. The optical detector 103 is sensitive to the temperature change. The change of the dark current in the optical detector 103 caused by the temperature change will affect the accuracy of the actual current of the optical detector 103 and cause certain errors to the test results.

[0121] Sixthly, the upper cover 108 is installed to seal the device to avoid the external dust from entering the inside and adhering to the surface of the optical fiber 101 to cause the burn of the optical fiber 101 and to avoid the interference of the external optical signal on the detection of the optical detector 103.

[0122] It should be noted that although the several devices, units, or modules of the optical fiber laser power monitoring device are mentioned in the foregoing detailed description, such division is merely exemplary and not mandatory. In fact, according to the embodiments of the present application, 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 into multiple modules.

[0123] Furthermore, although the operations of the method for making the fiber laser power monitoring device of the present application are described in a particular order, this is not meant to be a limitation on the order in which such operations are performed, or the ordering of the steps. Additionally or alternatively, certain steps can be omitted, combined, performed in a different order, and / or performed concurrently.

[0124] While the principles and spirit of the application have been described with reference to several specific embodiments, it is to be understood that the application is not limited to the specific embodiments disclosed, and that the division of aspects is not meant to imply that features from these aspects cannot be combined to benefit, but is merely for ease of presentation. The application is intended to cover any and all modifications and equivalent arrangements within the spirit and scope of the claims appended hereto.

Claims

1. A fiber laser power monitoring device, characterized by, The device comprises an optical fiber, a cladding light filter, a light detector and a fixing structure, wherein The cladding light filter is located on both sides of the light detector and is used to filter the cladding light in the optical fiber; The light detector is used to detect the signal light in the optical fiber; The fixing structure is used to fix the optical fiber, the cladding light filter and the light detector as a whole.

2. The monitoring device of claim 1, wherein, The optical fiber comprises a middle region and stripping regions at both ends of the middle region, and the stripping regions are regions where the coating of the optical fiber is stripped; The stripping region comprises a roughened region and non-roughened regions at both ends of the roughened region.

3. The monitoring device of claim 2, wherein, The roughened degree of the inner cladding surface of the roughened region is greater near the middle region than far from the middle region.

4. The monitoring device of claim 3, wherein, The roughened degree of the inner cladding surface of the roughened region decreases uniformly from near the middle region to far from the middle region.

5. The monitoring device according to any one of claims 2-4, characterized in that, The length of the middle region is greater than 1 cm; The length of the non-roughened 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 stripping region through a material corrosion method or a laser etching method.

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

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

9. The monitoring device of claim 8, wherein, The roughened region encapsulator is used to suspend and encapsulate the roughened region; The two ends of the roughened region encapsulator are fixed on the coating near the stripping port.

10. The monitoring device of claim 9, wherein, The length of each roughened region encapsulator is longer than the length of the corresponding stripping region.

11. The monitoring device of claim 8, wherein, The roughened region encapsulator is made of a transparent material with smooth inner and outer surfaces.

12. The monitoring device of claim 8, wherein, The bottom of the fixing structure comprises a semicircular groove for placing the integrated structure composed of the roughened region encapsulator after encapsulating the roughened region and the optical fiber.

13. The monitoring device according to any one of claims 1-4, characterized in that, The device further comprises a filter covering structure for encapsulating the cladding light filter to shield the cladding light scattered by the cladding light filter.

14. The monitoring device of claim 13, wherein, The filter covering structure is made of a dark material with rough surface.

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

16. The monitoring device according to any one of claims 1-4, characterized by The light detector is a photodiode.

17. The monitoring device according to any one of claims 2-4, characterized by The device further comprises a light detector fixator located above the middle region.

18. The monitoring device of claim 17, wherein, The lower surface of the light detector fixator and the upper surface of the fixing structure each comprise a semicircular optical fiber groove, and the two form an optical fiber groove. The optical fiber groove is used to concentrate the radiation light generated by the signal light in the middle region inside the optical fiber groove.

19. The monitoring device of claim 18, wherein, The surface of the optical fiber groove is treated by copper plating or gold plating polishing; The optical fiber groove is spherical.

20. The monitoring device of claim 18, wherein, The diameter of the optical fiber groove is greater than the outer diameter of the optical fiber.

21. The monitoring device of claim 18, wherein, The surface of the light detector fixator is provided with a small hole; The light detector is embedded above the light detector fixator and detects the radiation light generated by the signal light in the middle region concentrated inside the optical fiber groove through the small hole.

22. The monitoring device of claim 21, wherein, The device further comprises a filter located between the light detector and the light detector fixator for filtering stray light other than signal light.

23. The monitoring device of any one of claims 1-4, wherein, The device further comprises a control unit; The light detector is further configured to convert the detected light signal into an electric current signal; The control unit is configured to convert the electric current signal into a collection value to represent the actual output power of the fiber laser.

24. The monitoring device of claim 17, wherein, The device further comprises a temperature sensor embedded in the upper surface of the light detector holder, which is configured to monitor the temperature change of the light detector holder in real time to identify whether the scattered light generated by the cladding light filter affects the light detector.

25. The monitoring device of any one of claims 1-4, wherein, The device further comprises a cover configured to seal the device to prevent external dust and / or external light signals from entering.

26. The monitoring device of any one of claims 1-4, wherein, The fixing structure is a water-cooled plate.

27. The monitoring device of any one of claims 1-4, wherein, The numerical aperture of the optical fiber is 0.07 / 0.

46.

28. The monitoring device of claim 8, wherein, The roughened region encapsulator comprises a sandwich layer having circulating cooling liquid.

29. A method for fabricating a fiber laser power monitoring device, characterized in that, The device comprises an optical fiber, a cladding light filter, a light detector, and a fixing structure; and the method comprises: The cladding light filter is arranged on both sides of the light detector to filter the cladding light in the optical fiber; The light detector is configured to detect the signal light in the optical fiber; The fixing structure is configured to fix the optical fiber, the cladding light filter, and the light detector as a whole.

30. The preparation method according to claim 29, characterized in that, The cladding light filter comprises the roughened region; The step of arranging the cladding light filter on both sides of the light detector to filter the cladding light in the optical fiber specifically comprises: The coating layers on both ends of the middle region of the optical fiber are stripped to obtain a stripped region; The middle section of the stripped region is roughened to obtain a roughened region; Each of the left and right ends of the roughened region is reserved a section of the stripped coating layer that is not roughened to obtain a non-roughened region.

31. The method of claim 30, wherein, The roughening degree of the inner cladding surface of the roughened region is greater near the middle region than far from the middle region.

32. The method of claim 31, wherein, The roughening degree of the inner cladding surface of the roughened region uniformly decreases from near the middle region to far from the middle region.

33. The method of manufacturing according to any one of claims 30-32, wherein, The length of the middle region is greater than 1 cm; The length of the non-roughened region is greater than 0.5 cm.

34. The method of manufacturing according to any one of claims 30-32, wherein, The step of roughening the middle section of the stripped region to obtain a roughened region specifically comprises: The stripped region is roughened by an etching material etching method or a laser etching method to obtain the roughened region.

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

36. The method of manufacturing according to any one of claims 30-32, wherein, The cladding light filter further comprises a roughened region encapsulator; The step of arranging the cladding light filter on both sides of the light detector to filter the cladding light in the optical fiber specifically further comprises: The roughened region encapsulator is arranged.

37. The method of claim 36, wherein the method is performed in a single step. The step of arranging the roughened region encapsulator specifically comprises: fixing both ends of the roughened region encapsulator on the coating layers near the stripping ports, so that the roughened region encapsulator suspends and encapsulates the roughened region.

38. The method of claim 37, wherein the method is carried out at a temperature of about 20°C to about 30°C. The length of each roughened region encapsulator is longer than the length of the corresponding stripped region.

39. The method of claim 36, wherein the method is performed in a single step. The roughened region encapsulator is made of transparent and smooth material.

40. The preparation method according to claim 36, characterized in that, The bottom of the fixing structure comprises a semicircular groove; The step of setting the fixing structure to fix the optical fiber, the cladding light filter and the light detector as a whole comprises: placing a cladding region encapsulator encapsulating the cladding region and the optical fiber in the semicircular groove.

41. The method of manufacturing according to any one of claims 29-32, wherein, The device further comprises a filter covering structure. The method further comprises setting a filter covering structure to encapsulate the cladding light filter to shield the cladding light scattered by the cladding light filter. The filter covering structure is a rough-surfaced dark material.

42. The method of claim 41, wherein, The fixing structure is a rough-surfaced dark material.

43. The method of manufacturing according to claim 41 or 42, wherein, The method further comprises setting the fixing structure to also receive the energy of the scattered cladding light absorbed by the filter covering structure. The light detector is a photodiode.

44. The method of making according to any one of claims 29-32, wherein, The device further comprises a light detector holder.

45. The method of making according to any one of claims 30-32, wherein, The method further comprises setting the light detector holder above the middle region. The method further comprises matching the lower surface of the light detector holder with the semicircular fiber groove of the upper surface of the fixing structure, so that the two form a fiber groove to concentrate the radiation light generated by the signal light in the middle region inside.

46. The method of claim 45, wherein, The surface of the fiber groove is treated with copper or gold plating and polishing.

47. The method of claim 46, wherein the method is carried out at a temperature of about 20°C to about 30°C. The fiber groove is spherical. The diameter of the fiber groove is larger than the outer diameter of the optical fiber.

48. The preparation method according to claim 46, characterized in that, The step of setting the light detector holder above the middle region specifically comprises setting a small hole on the surface of the light detector holder.

49. The method of claim 46, wherein the method is carried out at a temperature of about 20°C to about 30°C. The step of setting the light detector to detect the signal light in the optical fiber specifically comprises: The method further comprises setting a filter between the light detector and the light detector holder to filter out stray light other than the signal light. The step of setting the light detector to detect the signal light in the optical fiber specifically comprises:

50. The method of claim 49, wherein, The step of setting the light detector to detect the signal light in the optical fiber specifically comprises:

51. The method of making according to any one of claims 29-32, wherein, The method further comprises setting a control unit to convert the current signal into a collection value to represent the actual output power of the fiber laser. The method further comprises setting a temperature sensor embedded in the upper surface of the light detector holder to monitor the temperature change of the light detector holder in real time, so as to identify whether the scattered light generated by the cladding light filter affects the light detector. The method further comprises setting a cover to seal the device to prevent the entry of external dust and / or external light signals.

52. The method of claim 45, wherein the method is carried out at a temperature of about 20°C to about 30°C. The fixing structure is a water-cooled plate.

53. The method of making according to any one of claims 29-32, wherein, The numerical aperture of the optical fiber is 0.07 / 0.

46.

54. The method of making of any one of claims 29-32, wherein, The cladding region encapsulator comprises a sandwich layer with circulating cooling liquid.

55. The method of making of any one of claims 29-32, wherein, ​ 56. The monitoring device of claim 36, wherein, ​

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