A laser resistant to high return light and a manufacturing method thereof

Abstract

The application relates to the field of optical transmission technology, in particular to a laser resistant to high return light and a manufacturing method thereof. The laser is coupled with a red light unit and a laser unit through a red light fiber and a main fiber. The red light fiber is a gradient refractive index fiber, the red light signal can be transmitted into the main fiber through the gradient refractive index design, and the red light signal is transmitted forward along the laser unit. The refractive index of the red light fiber is set to be smaller than the refractive index of the main fiber. Due to the different refractive indexes of the red light fiber and the main fiber, the return light is totally reflected at the coupling position of the main fiber and the red light fiber, so that the return light is effectively limited in the main fiber, the return light is reversely transmitted along the main fiber, and the risk that the return light damages the red light diode in the red light unit is reduced.

Description

Technical Field

[0001] This invention relates to the field of optical transmission technology, and in particular to a laser resistant to high backlighting and its manufacturing method. Background Technology

[0002] As the applications of fiber lasers continue to expand, the demand for laser stability is also increasing. The diversity of application scenarios leads to the use of different versions of lasers. For the cutting and processing of certain metal materials, such as copper and aluminum, these materials have a high surface reflectivity to the laser light from the fiber laser. The laser light reflected from the surface can be back-coupled into the fiber core or cladding of the fiber laser. This back-reflected laser light can be amplified and transmitted to the indicator optical path when it passes through the gain fiber of the fiber laser. In addition, due to incomplete reflection of the high-reflectivity grating in the resonant cavity optical path or the Raman laser light generated by the system, it will also be back-reflected into the indicator optical path through the fiber core. All of the laser light transmitted back along the fiber core can cause serious damage to the red diode in the indicator optical path, which can ultimately have a serious impact on the reliability and stability of the fiber laser.

[0003] Existing anti-return light technologies generally include: The first method is to use a red light indicator light to pass through a mode stripper, and then coil the optical fiber to squeeze the return light originally in the fiber core into the cladding, and then remove the return light by the mode stripper; The second method is to remove the cladding light through spatial coupling, and to use a spatial alignment scheme to process the cladding light. In this method, since the divergence angle of the return light is large, the red light passes through a focusing lens and the return light passes through a collimating lens, which further reduces the return light.

[0004] The shortcomings of existing technology are:

[0005] 1. Reducing cladding light by winding will also strip away some red light, and the coil cannot prevent the reflected light propagating in the fiber core from returning to the semiconductor, thus damaging the red diode.

[0006] 2. Spatial coupling is expensive, and the high power of the returned light can cause the lens to heat up, resulting in a decrease in red light, or even causing the lens to burn out.

[0007] Therefore, overcoming the shortcomings of the existing technology is an urgent problem to be solved in this technical field. Summary of the Invention

[0008] The technical problem to be solved by this invention is how to attenuate the reflected light in order to reduce the risk of damage to the red diode in a high-power laser caused by the reflected light.

[0009] The present invention adopts the following technical solution:

[0010] In a first aspect, a laser resistant to high backlighting is provided, comprising: a laser unit 1, a red light unit 2, a main optical fiber 3, and a red light optical fiber 4, wherein the output end of the red light unit 2 is coupled to one end of the red light optical fiber 4, and the other end of the red light optical fiber 4 is coupled to the side of the main optical fiber 3; the output end of the main optical fiber 3 is coupled to the input end of the laser unit 1.

[0011] The red light unit 2 is used to emit red light signals, and the red light optical fiber 4 is used to receive the red light signals and transmit the red light signals to the main optical fiber 3;

[0012] The refractive index of the red optical fiber 4 is lower than that of the main optical fiber 3, so that the return light from the output end of the main optical fiber 3 is transmitted in the reverse direction along the main optical fiber 3.

[0013] Preferably, the refractive index of the core of the red optical fiber 4 gradually decreases as its core radius increases, until it matches the refractive index of its cladding.

[0014] Preferably, the red light unit 2 includes a red light diode 20, a stripper 21 and an output optical fiber 22 coupled sequentially along the optical path, and the output optical fiber 22 is fused to one end of the red light optical fiber 4.

[0015] The red light diode 20 is used to generate the red light signal, and the stripper 21 is used to perform mode field adaptation and mode stripping on the optical fiber through which the red light signal flows, so as to perform mode matching with the output optical fiber 22.

[0016] The output optical fiber 22 is used to transmit the red light signal to the red light optical fiber 4.

[0017] Preferably, the stripper 21 includes a mode field adapter 210 and a red light mode stripper 211 coupled in sequence;

[0018] The mode field adapter 210 is used to perform mode matching between the output pigtail of the red light diode 20 and the output optical fiber 22, and the red light mode stripper 211 is used to set the stripping area in the mode matching area to reduce the transmission loss of the red light signal.

[0019] Preferably, the laser unit 1 includes a forward combiner 10, a high-reflection grating 11, a gain fiber 12, a low-reflection grating 13, a reverse combiner 14, and an output head 15, which are sequentially coupled along the forward transmission direction of the red light signal; at least one forward pump diode 16 is connected to the forward combiner 10, and at least one reverse pump diode 17 is connected to the reverse combiner 14.

[0020] The forward combiner 10 is used to couple the first pump light emitted by the forward pump diode 16 into the gain fiber 12; the reverse combiner 14 is used to couple the second pump light output by the reverse pump diode 17 into the gain fiber 12.

[0021] The gain fiber 12 is used to obtain gain through the excitation of the first pump light and the second pump light, and forms a resonant structure through the grating pair composed of the high-reflection grating 11 and the low-reflection grating 13 to realize the oscillation amplification of the laser to output the excitation light;

[0022] The excitation light is output as a positive excitation light through the low-reflection grating 13, and the positive excitation light is output through the output head 15.

[0023] Preferably, a laser mode stripper 30 is provided at the rear end of the fusion splice between the red optical fiber 4 and the main optical fiber 3 on the main optical fiber 3. The laser mode stripper 30 is used to guide the returned light into the corresponding heat dissipation device.

[0024] In a second aspect, a method for manufacturing a laser resistant to high backlighting is provided, for manufacturing a laser resistant to high backlighting as described in the first aspect, comprising:

[0025] The output end of the red light unit 2 is coupled to one end of the red light optical fiber 4;

[0026] The red optical fiber 4 is processed to make its refractive index lower than that of the main optical fiber 3, and the other end of the red optical fiber 4 is coupled to the side of the main optical fiber 3.

[0027] The output end of the main optical fiber 3 is coupled to the input end of the laser unit 1.

[0028] Preferably, the refractive index of the red optical fiber 4 is lower than that of the main optical fiber 3, and the other end of the red optical fiber 4 is coupled to the side of the main optical fiber 3, including:

[0029] The red optical fiber 4 is heat-treated so that the numerical aperture of the red optical fiber 4 is lower than that of the main optical fiber 3.

[0030] The coating layer of the red optical fiber 4 is stripped to expose its cladding, and the end of the red optical fiber 4 is cut flat.

[0031] The core of the red optical fiber 4 is expanded to make its refractive index lower than that of the main optical fiber 3, and the red optical fiber 4 is then heated, melted, and tapered.

[0032] The coating layer of the main optical fiber 3 is stripped off, and the red optical fiber 4, which has been heated, fused, and tapered, is fused to the cladding of the main optical fiber 3 to couple the red optical fiber 4 onto the main optical fiber 3.

[0033] Preferably, the formula for calculating the numerical aperture NA of the optical fiber is:

[0034]

[0035] Where n1 is the refractive index of the fiber core and n2 is the refractive index of the fiber cladding.

[0036] Preferably, a red light mode stripper 211 is coupled into the red light unit 2, and a laser mode stripper 30 is coupled into the main optical fiber 3. The fabrication method further includes:

[0037] The etching or etching process begins on the surface of the red optical fiber 4 until the cladding at a preset position on the red optical fiber 4 is removed to form a red mode stripper 211.

[0038] The process begins with etching or etching the surface of the main optical fiber 3 until the fiber core at a preset position on the main optical fiber 3 is removed, thus forming a laser stripper 30.

[0039] The portion of the red optical fiber 4 containing the red optical mode stripper 211 and the portion of the main optical fiber 3 containing the laser mode stripper 30 are integrated into the device housing.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] This invention couples the red light unit 2 and the laser unit 1 via a red light fiber 4 and a main fiber 3. The red light fiber 4 is a graded-index fiber, which allows the red light signal to be transmitted to the main fiber 3 and forward along the laser unit 1 through the graded-index design. The refractive index of the red light fiber 4 is set to be less than that of the main fiber 3. Due to the difference in refractive index between the red light fiber 4 and the main fiber 3, the reflected light will undergo total internal reflection at the coupling point between the main fiber 3 and the red light fiber 4, thus being effectively confined within the main fiber 3. This allows the reflected light to be transmitted in the reverse direction along the main fiber 3, reducing the risk of the reflected light damaging the red light diode 20 in the red light unit 2. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, 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.

[0043] Figure 1 This is a schematic diagram of the structure of a laser with high backlight resistance provided in an embodiment of the present invention;

[0044] Figure 2 This is another structural schematic diagram of a laser with high backlight resistance provided in an embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram of the structure of the red light unit of a laser with high backlight resistance provided in an embodiment of the present invention;

[0046] Figure 4 This is a schematic diagram of the structure of a laser unit of a laser with high backlight resistance provided in an embodiment of the present invention;

[0047] Figure 5 This is a schematic diagram of the structure of a laser stripper for a laser with high backlight resistance provided in an embodiment of the present invention;

[0048] Figure 6 This is a schematic flowchart of a method for manufacturing a laser with high backlight resistance according to an embodiment of the present invention;

[0049] Figure 7 This is another schematic diagram of the process for manufacturing a laser with high backlight resistance provided in an embodiment of the present invention;

[0050] Figure 8 This is a schematic diagram of the structure of a red light stripper and a laser stripper for a laser with high backlight resistance provided in an embodiment of the present invention;

[0051] Figure 9 This is a schematic diagram of the integrated structure of a red light stripper and a laser stripper for a laser with high backlight resistance, provided in an embodiment of the present invention.

[0052] Figure 10 This is a schematic diagram showing the integrated setup of a red light stripper and a laser stripper in an anti-high backlight laser according to an embodiment of the present invention.

[0053] In all the accompanying drawings, the same reference numerals denote the same structure, wherein:

[0054] Laser unit 1, forward combiner 10, high-reflection grating 11, gain fiber 12, low-reflection grating 13, reverse combiner 14, output head 15, forward pump diode 16, reverse pump diode 17, red light unit 2, red light diode 20, stripper 21, mode field adapter 210, red light mode stripper 211, output fiber 22, main fiber 3, laser mode stripper 30, red light fiber 4. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0056] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as openly inclusive, meaning "including, but not limited to." In the description of the specification, terms such as "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples" are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples; that is, although they may be incorporated into embodiments or examples using the above terms for reasons such as order and position, it does not limit them to be incorporated in combination by a single embodiment or example.

[0057] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of this disclosure, unless otherwise stated, "a plurality of" means two or more. Furthermore, for example, the description may use the prefix "A" or "B" to describe the same type of nouns as two independent entities. In this case, the corresponding features defined with "A" and "B" are used only to distinguish between similar entities and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0058] In describing some embodiments, the terms "coupled," "coupled," and "connected," and their derivative expressions, may be used. For example, the term "connected" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact with each other. Similarly, the term "coupled" may be used in describing some embodiments to indicate that two or more components have direct physical or electrical contact. However, the terms "connected" or "coupled" may also refer to two or more components that do not have direct contact with each other but still cooperate or interact with each other, such as "optical coupling," "wireless connection," etc. The embodiments disclosed herein are not necessarily limited to the scope of this invention.

[0059] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0060] Example 1:

[0061] In lasers, the main reasons for backlighting include the following four aspects: (1) Laser and pump light are bidirectional transmissions. The grating mainly reflects laser light with a core wavelength of 1080nm±2nm. However, as the power increases in the laser, the loss of active and passive optical fibers causes laser scattering. Some laser light exceeding 1080nm will leak from the high-reflectivity grating into the cladding, forming backlighting. (2) To control the Raman spectroscopy of the entire laser, back pumping is generally used. Some unabsorbed pump light will propagate along the cladding of the active optical fiber, forming backlighting. (3) The active optical fiber used in lasers is generally very long. The active optical fiber will be coiled along a certain bending radius. In high-power fiber lasers, some laser modes are poor, and the bending angle and the fiber transmission angle do not meet the total internal reflection condition. They overflow from the core into the cladding. This type of laser and pump light will also pass through the high-reflectivity grating in the core, forming backlighting. (4) When cutting high-reflectivity materials, some laser light will return to the resonant cavity along the core, forming backlighting.

[0062] However, in traditional lasers, a red light diode is typically placed at the front end of the laser. The red light signal generated by the red light diode is emitted together with the laser light generated after the pump light excites the gain fiber, serving as an indicator light. Therefore, in the four cases mentioned above, the reflected light will be reflected back to the red light diode along the optical path, causing damage to the red light diode.

[0063] To reduce the risk of damage to red light diodes caused by reflected light, this embodiment provides a laser resistant to high reflected light, such as... Figure 1 and Figure 2 As shown, the system includes: a laser unit 1, a red light unit 2, a main optical fiber 3, and a red light optical fiber 4. The output end of the red light unit 2 is coupled to one end of the red light optical fiber 4, and the other end of the red light optical fiber 4 is coupled to the side of the main optical fiber 3. The output end of the main optical fiber 3 is coupled to the input end of the laser unit 1. The red light unit 2 emits a red light signal, and the red light optical fiber 4 receives the red light signal and transmits it to the main optical fiber 3. The refractive index of the red light optical fiber 4 is lower than that of the main optical fiber 3, so that the reflected light from the output end of the main optical fiber 3 is transmitted in the reverse direction along the main optical fiber 3. In one embodiment, the red light optical fiber 4 can be the pigtail of the red light unit 2, directly coupled to the main optical fiber 3. Alternatively, the red light optical fiber 4 can be a single optical fiber, with one end first coupled to the side of the main optical fiber 3, and the other end then coupled to the output optical fiber 22 of the red light unit 2 (e.g., ...). Figure 3(As shown in the diagram) coupling. Correspondingly, for ease of description, the main optical fiber 3 can either be coupled as a separate optical fiber to the red optical fiber 4 and then coupled to the input end of the laser unit 1 (described below), or it can be directly coupled to the red optical fiber 4 as part of the laser unit 1. In this embodiment, both the red optical fiber 4 and the main optical fiber 3 are separate optical fibers. It is worth noting that the coupling here can be achieved by fusion splicing the optical fibers. Specific fusion splicing techniques include side splicing and end splicing, which will not be discussed in detail in this embodiment.

[0064] To combat high backlighting, this embodiment employs a red light unit 2, a red light fiber 4, and a main fiber 3. The red light unit 2 generates a red light signal, and the red light fiber 4 receives and transmits the red light signal to the main fiber 3. By setting the refractive index of the red light fiber 4 to be lower than that of the main fiber 3, backlighting from the output of the main fiber 3 will be transmitted in the reverse direction along the main fiber 3, instead of being reflected back to the red light unit 2 via the red light fiber 4. This reduces the risk of damage to the red light diode 20 in the red light unit 2.

[0065] To transmit the red light signal generated by the red light unit 2 to the main optical fiber 3, in one embodiment, the red light optical fiber 4 can be a graded-index transition fiber, meaning that the refractive index of the core of the red light optical fiber 4 gradually decreases as its core radius increases until it matches the refractive index of its cladding. Since the divergence angle of the red light signal is large, in multimode fiber, the light signal propagates at multiple different incident angles, which depend on the wavefront shape of the red light signal. Due to the variation in the core refractive index of the red light optical fiber 4, red light signals at different incident angles will have different transmission paths and speeds. This difference leads to different transmission times for the red light signal in the red light optical fiber 4, thus causing modal dispersion. Graded-index fiber, by making its core refractive index decrease with increasing radius, slows down the rate of change of refractive index, reduces modal dispersion, and thus improves the transmission quality of the red light signal, enabling better transmission of the red light signal to the main optical fiber 3.

[0066] The specific structures of the red light unit 2 and the laser unit 1 will be described next.

[0067] In one embodiment, such as Figure 3As shown, the red light unit 2 includes a red light diode 20, a stripper 21, and an output optical fiber 22 coupled sequentially along the optical path. The output optical fiber 22 is fused to one end of the red light optical fiber 4. The red light diode 20 is used to generate the red light signal. The stripper 21 is used to perform mode field adaptation and mode stripping on the optical fiber through which the red light signal flows, so as to perform mode matching with the output optical fiber 22. The output optical fiber 22 is used to transmit the red light signal to the red light optical fiber 4.

[0068] In one embodiment, the red optical fiber 4 and the output optical fiber 22 are different optical fibers, and the output optical fiber 22 is coupled to the red optical fiber 4. In other embodiments, the output optical fiber 22 may be omitted, and the red optical fiber 4 may be directly coupled to the stripper 21, depending on the actual situation.

[0069] Generally, the stripper 21 is subjected to texturing and etching operations. When the red light signal is output from the red light diode 20, it is easy for the red light signal to escape from the stripper 21. To solve this problem, in one embodiment, such as Figure 3 As shown, the stripper 21 includes a mode field adapter 210 and a red light stripper 211 coupled in sequence; the mode field adapter 210 is used to perform mode matching between the output pigtail of the red light diode 20 and the output optical fiber 22, and the red light stripper 211 is used to set the stripping area in the mode matching area to reduce the transmission loss of the red light signal.

[0070] Specifically, the mode field adapter 210 functions to perform mode matching between the output pigtail of the red light diode 20 and the output optical fiber 22 (or red optical fiber 4). The design of the mode field adapter 210 is to ensure that the optical mode of the red light signal output from the red light diode 20 can be adapted to the mode of the output optical fiber 22, thereby reducing the loss and modal dispersion of the red light signal at the connection point. In one embodiment, the mode field adapter 210 is typically implemented using components such as lenses or fiber couplers; more specific details are not provided in this embodiment.

[0071] The purpose of the red light mode stripper 211 is to position the stripping region within the mode-matching area selected by the mode field adapter 210. This is done to reduce transmission loss due to optical mode mismatch during the stripping process. The red light mode stripper 211 is used to cut a portion of the optical fiber to reduce reflection and echo of the red light signal, thereby improving system performance. By positioning the stripping region of the red light mode stripper 211 within the mode-matching area, it is ensured that the red light mode stripper 211 will not damage the optical mode during the stripping process, thus reducing the transmission loss of the red light signal.

[0072] In one embodiment, such as Figure 4As shown, the laser unit 1 includes a forward combiner 10, a high-reflection grating 11, a gain fiber 12, a low-reflection grating 13, a reverse combiner 14, and an output head 15, sequentially coupled along the forward transmission direction of the red light signal. At least one forward pump diode 16 is connected to the forward combiner 10, and at least one reverse pump diode 17 is connected to the reverse combiner 14. The forward combiner 10 couples the first pump light emitted by the forward pump diode 16 into the gain fiber 12. The reverse combiner 14 couples the second pump light output by the reverse pump diode 17 into the gain fiber 12. The gain fiber 12 obtains gain through the excitation of the first and second pump lights, and forms a resonant structure through the grating pair composed of the high-reflection grating 11 and the low-reflection grating 13 to achieve laser oscillation amplification and output excitation light. The excitation light outputs forward excitation light through the low-reflection grating 13, and the forward excitation light is output through the output head 15.

[0073] The forward combiner 10 couples the first pump light emitted by the forward pump diode 16 into the gain fiber 12. This first pump light excites the gain fiber 12, which contains rare-earth-doped fibers. These elements absorb the energy of the pump light and convert it into laser beam energy. The length and doping concentration of the gain fiber 12 determine the laser's gain characteristics and wavelength, but are not specifically limited in this embodiment. The forward combiner 10 typically includes fiber couplers, lenses, or other optical elements to ensure efficient coupling of the first pump light. The reverse combiner 14 couples the second pump light output from the reverse pump diode 17 into the gain fiber 12. This structure allows for the simultaneous use of pump light from two directions to improve the laser's efficiency and gain.

[0074] The high-reflectivity grating 11 reflects most of the laser beam, with only a small portion being transmitted. Thus, the laser beam is reflected back and forth within the gain fiber 12, amplified each time it passes through. The high-reflectivity grating 11 is typically tightly coupled to the end of the gain fiber 12 to form a resonant cavity. The low-reflectivity grating 13 is typically located at the laser's output end, allowing a portion of the laser beam to exit from the resonant cavity. The low-reflectivity grating 13 has a lower reflectivity than the high-reflectivity grating 11, therefore it reflects only a small portion of the beam while allowing most of it to pass through.

[0075] The output head 15 is the output section of the laser, which typically includes fiber couplers and other optical components to ensure that the laser beam can be efficiently output from the laser and transmitted to the desired location. The entire laser unit 1 is designed to gain gain through the excitation of pump light and to amplify and output the laser beam using a resonant structure composed of grating pairs. This structure can generate optical signals with specific wavelengths and intensities, making it suitable for various applications.

[0076] In one embodiment, a large reflected light ratio may affect other components in the laser, causing damage. Therefore, as... Figure 5 As shown, a laser mode stripper 30 is located at the rear end of the fusion splice between the red optical fiber 4 and the main optical fiber 3 on the main optical fiber 3. The laser mode stripper 30 is used to guide the reflected light into a corresponding heat dissipation device. Here, the rear end of the fusion splice refers to... Figure 5 Left side of the weld joint.

[0077] Specifically, the laser stripper 30 can be a through-core stripper (i.e., the etching depth penetrates from the cladding of the main optical fiber 3 to the core of the main optical fiber 3). With this design, the laser stripper 30 can guide the reflected light from the output end of the main optical fiber 3 through the device housing into the corresponding heat dissipation device for heat dissipation, thereby preventing other devices from being damaged by the reflected light. The heat dissipation device can be a water-cooled plate.

[0078] In this embodiment, the red light unit 2 and the laser unit 1 are coupled through the red light fiber 4 and the main fiber 3. The red light fiber 4 is a graded-index fiber, which allows the red light signal to be transmitted to the main fiber 3 and forward along the laser unit 1 through the graded-index design. The refractive index of the red light fiber 4 is set to be less than that of the main fiber 3. Due to the difference in refractive index between the red light fiber 4 and the main fiber 3, the reflected light will undergo total internal reflection at the coupling point between the main fiber 3 and the red light fiber 4, thus being effectively confined within the main fiber 3. This allows the reflected light to be transmitted in the reverse direction along the main fiber 3, reducing the risk of the reflected light damaging the red light diode 20 in the red light unit 2.

[0079] Example 2:

[0080] In Example 1, a laser resistant to high backlighting was proposed. In this example, a method for fabricating a laser resistant to high backlighting will be proposed, such as... Figure 6 As shown, the manufacturing method includes:

[0081] Step 101: Couple the output end of the red light unit 2 to one end of the red light optical fiber 4.

[0082] The red light unit 2 includes a red light diode 20, a stripper 21, and an output optical fiber 22 coupled sequentially along the optical path. The output optical fiber 22 is fused to one end of the red light optical fiber 4. The red light diode 20 is used to generate the red light signal. The stripper 21 is used to perform mode field adaptation and mode stripping on the optical fiber through which the red light signal flows, so as to perform mode matching with the output optical fiber 22. The output optical fiber 22 is used to transmit the red light signal to the red light optical fiber 4.

[0083] In one embodiment, the output end of the red light unit 2 is the output optical fiber 22. One end of the output optical fiber 22 is fused to one end of the red light optical fiber 4. The fusion splicing of the optical fibers is performed using an optical fiber fusion splicer. Before splicing, various parameters of the fusion splicer should be set, including discharge voltage, discharge time, and splicing temperature. Typically, the factory-set parameters are used. During splicing, the diced optical fiber is gently placed into the V-groove of the fusion splicer. The optical fiber must not come into contact with any object during the process from being removed from the dicer to being placed into the V-groove, and it should not be left exposed to air for an extended period. The length of the optical fiber placed in the V-groove should not exceed the center line of the electrode. The two optical fibers should be kept 1-3 mm apart. The protective cover should be closed, and the AUTO button on the fusion splicer should be pressed to start the automatic splicing program.

[0084] During the fusion splicing process, the splicing status can be observed on the fusion splicer's screen, which simultaneously displays the X-axis and Y-axis alignment status. During fiber alignment, it's crucial to promptly check the flatness of the end faces of the two fiber cores. If any defective end faces are found, the splicing operation should be immediately terminated, and the end faces remade. During the splicing process, carefully observe the arc discharge for defects such as excessive thinness, excessive thickness, incomplete melting, separation, or air bubbles. Also, carefully review the estimated loss test results after splicing. The estimated loss value should be less than 0.3dB; otherwise, the end faces and splicing must be remade. After fiber fusion splicing, since the fiber coating has been stripped, reducing its mechanical strength, the joint must be protected using a heat shrink tubing. The heat shrink tubing must be inserted before end face preparation; it is forbidden to insert it after fiber cutting. Adjust the position of the heat shrink tubing to the center of the fiber joint and place it in the heater for heating. The heat shrink tubing will then tightly fit onto the spliced ​​fiber, securing the heat shrink tubing and protecting the fiber joint.

[0085] Step 102: Process the red optical fiber 4 so that the refractive index of the red optical fiber 4 is lower than that of the main optical fiber 3, and couple the other end of the red optical fiber 4 to the side of the main optical fiber 3.

[0086] In one embodiment, such as Figure 7 As shown, step 102 specifically includes:

[0087] Step 1021: Perform heat treatment on the red optical fiber 4 so that the numerical aperture of the red optical fiber 4 is lower than that of the main optical fiber 3.

[0088] Heat treatment is a method to alter the physical properties of optical fiber materials. According to Example 1, the red optical fiber 4 is a graded-index fiber. The red optical fiber 4 is heated to change its refractive index distribution, thereby reducing its numerical aperture. Numerical aperture is a key characteristic of optical fibers, related to their coupling efficiency and modal dispersion. By reducing the numerical aperture of the red optical fiber 4, modal mismatch during coupling with the main optical fiber 3 can be reduced, thus improving coupling efficiency.

[0089] Because the refractive index of the core of a graded-index fiber varies, the light-gathering ability differs at different points on the core endface. Therefore, the concept of local numerical aperture (NA) is introduced in graded-index fibers. NA specifically refers to the numerical aperture at a point on the fiber endface, characterizing the light-gathering ability at that point. The formula for calculating the numerical aperture (NA) of an optical fiber is:

[0090]

[0091] Where n1 is the refractive index of the fiber core and n2 is the refractive index of the fiber cladding. The local numerical aperture is related to the refractive index at that point; the larger the refractive index at that point, the larger the local numerical aperture.

[0092] Step 1022: Remove the coating layer of the red optical fiber 4 to expose its cladding, and cut the end of the red optical fiber 4 flat.

[0093] To better fuse with the cladding of the main fiber 3 and ensure good mechanical and optical contact, the outer coating material of the red fiber 4 is removed, exposing its cladding. The end of the red fiber 4 is then cut flat to provide better coupling in subsequent operations.

[0094] Step 1023: Expand the core of the red optical fiber 4 to make its refractive index lower than that of the main optical fiber 3, and then heat and melt tape the red optical fiber 4.

[0095] Core expansion refers to increasing the diameter of the core of the red fiber 4, which is usually achieved by heating and stretching the fiber. This reduces the refractive index of the core of the red fiber 4, thereby reducing mode mismatch with the main fiber 3. Heated fusion taper is an optical fiber processing technique that melts the fiber by heating and then stretching it into a slender tapered shape, thereby increasing the contact area with the cladding of the main fiber 3 and improving the transmission efficiency of the red light signal.

[0096] Step 1024: Remove the coating layer of the main optical fiber 3, and fuse the heated and fused tapered red optical fiber 4 with the cladding of the main optical fiber 3 to couple the red optical fiber 4 onto the main optical fiber 3.

[0097] Specifically, step 1024 proposes a side-splicing technique, in which the red light signal is injected from the side of the main fiber 3 via the red fiber 4, rather than from the end face. The heated fusion taper-treated red fiber 4 is fused together with the cladding of the main fiber 3. The fusion splicing is typically performed in a fusion splicer, which precisely aligns and fuses the ends of the fibers to ensure a good optical connection. After fusion splicing, the red fiber 4 is coupled to the main fiber 3.

[0098] Step 103: Couple the output end of the main optical fiber 3 to the input end of the laser unit 1.

[0099] In one embodiment, when the main fiber 3 and the laser unit 1 are integrated, the entire laser fabrication can be completed by coupling the red fiber 4 into the main fiber 3 as mentioned in step 102. For ease of description, the main fiber 3 is a single fiber. Therefore, after coupling the red fiber 4 to the side of the main fiber 3, it is also necessary to connect the output end of the main fiber 3 to the input end of the laser unit 1 (i.e.,...). Figure 4 The left port of the positive-direction combiner 10 is fused together.

[0100] Due to the size limitations of the laser housing, the red light stripper 211 and the laser stripper 30 can be integrated to reduce the number of device housings, freeing up space for heat dissipation and other processing. In one embodiment, the fabrication method further includes: etching or etching the surface of the red optical fiber 4 until the cladding at a predetermined position on the red optical fiber 4 is removed to form the red light stripper 211; wherein, the red optical fiber 4 can be treated by CO2 etching, hydrofluoric acid etching, or abrasive paste with corrosive properties, and the predetermined position can be determined according to the actual situation, for example, red light strippers 211 can be fabricated on both sides of the core of the red optical fiber 4, and each side of the red light stripper 211 includes at least one removal area with a triangular cross-section (e.g., Figure 8 (As shown).

[0101] The process begins with etching or etching the surface of the main optical fiber 3 until the fiber core at a predetermined position on the main optical fiber 3 is removed to form a laser stripper 30. The main optical fiber 3 can be treated with CO2 etching, hydrofluoric acid etching, or abrasive paste with corrosive properties. The predetermined position can be determined according to the actual situation. For example, the laser stripper 30 can be made at the end of the main optical fiber 3 away from the laser unit 1.

[0102] During the fabrication of the red light stripper 211, the cladding at the preset position is etched or etched away without corroding or etching the core of the red light fiber 4. During the fabrication of the laser stripper 30, the core at the preset position is etched or etched away.

[0103] like Figure 8 As shown, a red fiber stripper 211 is fabricated in the red fiber 4 using a CO2 laser etching machine, hydrofluoric acid etching, or a special abrasive paste etching method. The CO2 laser etching machine precisely removes the fiber material using a laser beam, hydrofluoric acid etching uses a chemical reaction to remove material, and the abrasive paste removes material through mechanical abrasion. The etching time and depth are controlled to ensure that the red fiber stripper 211 is etched to the cladding of the red fiber 4 but does not touch its core, thus obtaining the red fiber stripper 211.

[0104] Reference Figure 8 The laser stripper 30 is fabricated in the main optical fiber 3. CO2 laser etching, hydrofluoric acid etching, or abrasive paste etching can be used to control the etching time and the etching depth, so that the etching can be carried out from the cladding of the main optical fiber 3 to the core, so as to obtain the laser stripper 30 in the main optical fiber 3.

[0105] like Figure 9 As shown, the portion of the red fiber 4 containing the red mode stripper 211 and the portion of the main fiber 3 containing the laser mode stripper 30 are integrated into a device housing to form an integrated device. The red etched region of the red mode stripper 211 and the laser etched region of the laser mode stripper 30 are integrated into a single device housing to form a cladding mode stripper (CMS), thus saving space in the laser. Figure 10 The image shows the position of the combined CMS within the entire laser.

[0106] This invention provides a low-cost method to attenuate reflected light, reducing the risk of damage to the red diode 20 in a high-power laser caused by reflected light. Simultaneously, the all-fiber structure offers higher reliability. The specific structure of the laser resistant to high reflected light is described in Embodiment 1 and will not be repeated here.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laser resistant to high backlighting, characterized in that, include: The laser unit (1), the red light unit (2), the main optical fiber (3) and the red light optical fiber (4) are provided. The output end of the red light unit (2) is coupled to one end of the red light optical fiber (4), and the other end of the red light optical fiber (4) is coupled to the side of the main optical fiber (3). The output end of the main optical fiber (3) is coupled to the input end of the laser unit (1). The red light unit (2) is used to emit red light signals, and the red light optical fiber (4) is used to receive the red light signals and transmit the red light signals to the main optical fiber (3); The refractive index of the red optical fiber (4) is lower than that of the main optical fiber (3). When the return light from the output end of the main optical fiber (3) is transmitted in the reverse direction along the main optical fiber (3), total internal reflection occurs at the coupling point between the main optical fiber (3) and the red optical fiber (4), so that the return light from the output end of the main optical fiber (3) is transmitted in the reverse direction along the main optical fiber (3). The refractive index of the core of the red optical fiber (4) gradually decreases as its core radius increases until it matches the refractive index of its cladding. The red light unit (2) includes a red light diode (20), a stripper (21) and an output optical fiber (22) coupled sequentially along the optical path. The output optical fiber (22) is fused to one end of the red light optical fiber (4). The stripper (21) includes a mode field adapter (210) and a red light stripper (211) coupled in sequence. The mode field adapter (210) is used to perform mode matching between the output pigtail of the red light diode (20) and the output optical fiber (22), and the red light mode stripper (211) is used to set the stripping area in the mode matching area to reduce the transmission loss of the red light signal.

2. The laser with high backlight resistance according to claim 1, characterized in that, The laser unit (1) includes a forward combiner (10), a high-reflection grating (11), a gain fiber (12), a low-reflection grating (13), a reverse combiner (14), and an output head (15) sequentially coupled along the forward transmission direction of the red light signal; at least one forward pump diode (16) is connected to the forward combiner (10), and at least one reverse pump diode (17) is connected to the reverse combiner (14). The forward combiner (10) is used to couple the first pump light emitted by the forward pump diode (16) into the gain fiber (12); the reverse combiner (14) is used to couple the second pump light output by the reverse pump diode (17) into the gain fiber (12). The gain fiber (12) is used to obtain gain through the excitation of the first pump light and the second pump light, and forms a resonant structure through the grating pair composed of the high-reflection grating (11) and the low-reflection grating (13) to realize the oscillation amplification of the laser to output the excitation light; The excitation light is output through the low-reflection grating (13) to produce a positive excitation light, which is then output through the output head (15).

3. The laser with high backlight resistance according to claim 1, characterized in that, A laser stripper (30) is provided at the rear end of the fusion splice between the red optical fiber (4) and the main optical fiber (3) on the main optical fiber (3). The laser stripper (30) is used to guide the returned light into the corresponding heat dissipation device.

4. A method for manufacturing a laser resistant to high backlighting, characterized in that, For fabricating a laser resistant to high backlighting as described in any one of claims 1-3, comprising: The output end of the red light unit (2) is coupled to one end of the red light optical fiber (4); The red optical fiber (4) is processed so that the refractive index of the red optical fiber (4) is lower than that of the main optical fiber (3), and the other end of the red optical fiber (4) is coupled to the side of the main optical fiber (3). The output end of the main optical fiber (3) is coupled to the input end of the laser unit (1).

5. The method for manufacturing a laser resistant to high backlighting according to claim 4, characterized in that, Making the refractive index of the red optical fiber (4) lower than that of the main optical fiber (3), and coupling the other end of the red optical fiber (4) to the side of the main optical fiber (3) includes: The red optical fiber (4) is heat-treated so that the numerical aperture of the red optical fiber (4) is lower than that of the main optical fiber (3). The coating layer of the red optical fiber (4) is stripped off to expose its cladding, and the end of the red optical fiber (4) is cut flat. The core of the red optical fiber (4) is expanded to make its refractive index lower than that of the main optical fiber (3), and the red optical fiber (4) is heated, melted and tapered. The coating layer of the main optical fiber (3) is stripped off, and the red optical fiber (4) after heating and melting tapering is fused with the cladding of the main optical fiber (3) to couple the red optical fiber (4) onto the main optical fiber (3).

6. The method for manufacturing a laser resistant to high backlighting according to claim 5, characterized in that, The formula for calculating the numerical aperture (NA) of an optical fiber is: Where n1 is the refractive index of the fiber core and n2 is the refractive index of the fiber cladding.

7. The method for manufacturing a laser resistant to high backlighting according to claim 4, characterized in that, A red light mode stripper (211) is coupled into the red light unit (2), and a laser mode stripper (30) is coupled into the main optical fiber (3). The fabrication method further includes: The process begins with etching or etching the surface of the red optical fiber (4) until the cladding at a preset position on the red optical fiber (4) is removed to form a red mode stripper (211). The etching or etching process is carried out from the surface of the main optical fiber (3) until the fiber core at a preset position on the main optical fiber (3) is removed to form a laser stripper (30). The portion of the red optical fiber (4) containing the red optical mode stripper (211) and the portion of the main optical fiber (3) containing the laser mode stripper (30) are integrated into the device housing.

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