Patent Publication Number: US-2023136582-A1

Title: Optical fiber module and manufacturing method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority to Taiwan Patent Application No. 110140441, filed on Oct. 29, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an optical fiber structure, and more particularly, to a multifunctional optical fiber module and a manufacturing method thereof. 
     2. Description of Related Art 
     In recent years, lasers have been widely used in various processing operations. As the demand for processing diversification and processing thickness increases, the power of lasers has become higher and higher. One of the ways to increase laser power is to combine multiple laser beams with an optical-fiber light-collecting element, and then output them from a single optical fiber. This method can achieve the light collection effect and ensure that the lasers from different sources are coaxial. 
     The general direct diode laser (DDL) type configuration is to connect multiple optical fiber lasers to an output beam coupler by optical fibers, and the output beam coupler outputs the laser light by one transmission optical fiber. 
     When processing objects, it is most feared that the reflected light will be reflected back to the original optical path system along the laser optical axis. This situation is likely to cause damage to the laser system, especially the excitation source at the input end is most likely to be damaged by the reflected light, and the cost of the excitation source usually accounts for more than 50% of the overall cost of the laser machine. 
     However, in general laser machines, the light-collecting element can only be used to combine laser sources from multiple sources on a single optical fiber axis for transmission. Therefore, the output beam coupler can only be used for light combining. An additional optical system (such as a reflected light detection optical path or an optical-fiber filter element) is required to perform the operation of determining the reflected light, so as to detect the reflected power at the laser output end, as a mechanism to protect the laser source. 
     However, the general method of adding optical elements will reduce the transmission efficiency of the laser, increase the cost of the laser, and cannot accurately determine the magnitude of the reflected light power actually reflected back to the emission source, resulting in misjudgment of the monitoring. Therefore, how to overcome the various problems of the prior art has become a problem that the industry urgently needs to overcome. 
     SUMMARY 
     In view of the above-mentioned problems of the prior art, the present disclosure provides an optical fiber module, which comprises: a plurality of first optical fibers collectively arranged to form at least one optical fiber bundle with a tapered end; a second optical fiber connected to the tapered end of the optical fiber bundle to converge the optical fiber bundle to the second optical fiber; a housing accommodating the optical fiber bundle with the tapered end and the second optical fiber and having a light-absorbing area corresponding to an end of the second optical fiber, wherein the second optical fiber is located between the optical fiber bundle and the light-absorbing area, and the light-absorbing area absorbs scattering signals escaped and scattered when signals are transmitted from the plurality of first optical fibers to the second optical fiber; and a photoelectric sensor configured corresponding to the optical fiber bundle with the tapered end and arranged in the housing, wherein the photoelectric sensor receives target signals escaped and refracted when the signals are transmitted from the second optical fiber to the plurality of first optical fibers. 
     The present disclosure further provides a manufacturing method of an optical fiber module, the manufacturing method comprises: performing a pre-cleaning discharge modulation operation to clean up surfaces of a plurality of first optical fibers; performing step discharge to swing and taper the plurality of first optical fibers to form at least one optical fiber bundle with a tapered end; performing periodic discharge to increase structural strength of the optical fiber bundle after tapering; and connecting a second optical fiber to the tapered end of the optical fiber bundle. 
     It can be seen from the above that the optical fiber module according to the present disclosure and the manufacturing method thereof integrate a photoelectric sensor and an optical fiber structure (i.e., an optical fiber bundle and a second optical fiber) into a housing to form a laser light-collecting element (i.e., the optical fiber module) with a built-in reflected power detection function (i.e., the photoelectric sensor). As compared with the prior art, the present disclosure not only has the efficiency of multi-beam laser combining light, but also can simultaneously capture and detect the reflected power signal inside it. 
     BRIEF DESCRIOPTION OF THE DRAWINGS 
       FIG.  1 A- 1    is a schematic configuration view of a general direct diode laser type. 
       FIG.  1 A- 2    is a schematic configuration view of an additional optical system of  FIG.  1 A- 1   . 
       FIG.  1 A- 3    is another schematic configuration view of an additional optical system of  FIG.  1 A- 1   . 
       FIG.  1 B  is a schematic configuration view of a general optical fiber laser type. 
       FIG.  2 A  is a schematic side perspective view of an optical fiber module according to the present disclosure. 
       FIG.  2 B- 1    is a schematic three-dimensional view of an optical fiber structure of an optical fiber module according to the present disclosure. 
       FIG.  2 B- 2    is a schematic cross-sectional view of an optical fiber bundle of  FIG.  2 B- 1    at a connection point. 
       FIG.  2 B- 3    is a schematic cross-sectional view of a second optical fiber of  FIG.  2 B- 1    at the connection point. 
       FIG.  2 C  is a schematic partial view of  FIG.  2 A . 
       FIG.  2 D  is a schematic partial view of  FIG.  2 C . 
       FIG.  3    is a schematic side perspective view of an optical fiber module according to the present disclosure in operation. 
       FIG.  4    is a schematic diagram of a thermal response of a manufacturing method of an optical fiber module according to the present disclosure during the production of the optical fiber bundle. 
    
    
     DETAILED DESCRIPTIONS 
     The following describes the implementation of the present disclosure with examples. Those familiar with the art can easily understand the other advantages and effects of the present disclosure from the content disclosed in this specification. 
     It should be understood that, the structures, ratios, sizes, and the like in the accompanying figures are used to illustrate the content disclosed in the present disclosure for one skilled in the art to read and understand, rather than to limit the conditions for practicing the present disclosure. Any modification of the structure, alteration of the ratio relationship, or adjustment of the size without affecting the possible effects and achievable proposes should still fall in the range compressed by the technical content disclosed in the present disclosure. Meanwhile, terms such as “upper,” “first,” “second” and the like used herein are merely used for clear explanation rather than limiting practical range by the present disclosure, and thus, the alteration or adjustment of relative relationship thereof without altering the technical content should be considered in the practical scope of the present disclosure. 
     As shown in  FIG.  1 A- 1   , a general direct diode laser (DDL) type configuration is to connect a plurality of optical fiber lasers  10  to an output beam coupler  11  by optical fibers  100 , and the output beam coupler  11  outputs the laser light through a transmission optical fiber  110  (e.g., transmission direction X shown in  FIG.  1 A- 1   ). 
     Alternatively, as shown in  FIG.  1 B , a general optical fiber laser type configuration is to connect a plurality of pump diodes  12  to a first pump coupler  13   a  and a second pump coupler  13   b  via optical fibers  120 , respectively, and the first pump coupler  13   a  is connected to the second pump coupler  13   b  by an active optical fiber  130 , so that the second pump coupler  13   b  outputs the laser light through an output optical fiber  14  (e.g., transmission direction Y shown in  FIG.  1 B ). 
     When processing objects, it is most feared that the reflected light will be reflected back to the original optical path system along the laser optical axis. This situation is likely to cause damage to the laser system, especially the excitation source at the input end is most likely to be damaged by the reflected light, and the cost of the excitation source usually accounts for more than 50% of the overall cost of the laser machine. 
     However, in general laser machines, the light-collecting element can only be used to combine laser sources from multiple sources on a single optical fiber axis for transmission. Therefore, the output beam coupler  11  (or the first pump coupler  13   a  and the second pump coupler  13   b ) can only be used for light combining. An additional optical system (such as a reflected light detection optical path or an optical-fiber filter element) is required to perform the operation of determining the reflected light, so as to detect the reflected power at the laser output end, as a mechanism to protect the laser source. 
     As shown in  FIG.  1 A- 2   , in a general direct diode laser (DDL) type configuration, a cladding power stripper  15  and a splitter  16  are connected in sequence between the output beam coupler  11  and a laser head la by a transmission optical fiber  110 , so as to partially split the reflected light by the splitter  16  (e.g., splitting path Z shown in  FIG.  1 A- 2   ), and then to perform detection by a power meter  17 . 
     Alternatively, as shown in  FIG.  1 A- 3   , in a general direct diode laser (DDL) type configuration, a first fiber-shell power filter  15   a  and a second fiber-shell power filter  15   b  are connected in sequence between the output beam coupler  11  and the laser head la by a transmission optical fiber  110 . The pump light will escape from the first fiber-shell power filter  15   a , and the second fiber-shell power filter  15   b  is used to capture the reflected light escaping to the fiber shell, and then the power meter  17  performs detection. 
     However, the general method of adding optical elements will reduce the transmission efficiency of the laser, increase the cost of the laser, and cannot accurately determine the amount of reflected light power actually reflected back to the emission source, resulting in misjudgment of the monitoring. For example, the addition of the fiber-shell power filter  15  and the beam splitter  16  shown in  FIG.  1 A- 2    will cause part of the laser loss, and the alignment steps for adjusting the path are very complicated, which requires additional material costs and labor costs. Further, the addition of the first fiber-shell power filter  15   a  and the second fiber-shell power filter  15   b  shown in  FIG.  1 A- 3    requires the provision of multiple filters and additional costs, and the proportion of light leakage will vary with the angle of the reflected light, which is likely to cause misjudgment. 
       FIGS.  2 A to  2 D  are schematic views of an optical fiber module  2  according to the present disclosure. As shown in  FIGS.  2 A to  2 B- 1   , the optical fiber module  2  includes a plurality of first optical fibers  210 , a second optical fiber  22 , a housing  20  and a photoelectric sensor  23 . 
     As shown in  FIG.  2 B- 1   , the plurality of first optical fibers  210  are collectively configured to form at least one optical fiber bundle  21  having a tapered end  21   a . It should be noted that the tapered end  21   a  shown in  FIGS.  2 A to  2 D  is a schematic outline, and the tapered end  21   a  is a mask for covering the first optical fibers  210 , and as the manufacturing method described later, the plurality of first optical fibers  210  use a fusion tapering method to form the optical fiber bundle  21  having the tapered end  21   a.    
     In an embodiment, the plurality of first optical fibers  210  are used to receive a laser light source, and the first optical fibers  210  have opposite first ports  210   a  and second ports  210   b , so that the first ports  210   a  of the plurality of first optical fibers  210  serve as the tapered top surface T of the tapered end  21   a  of the optical fiber bundle  21 , and the second ports  210   b  are connected to a signal source like a laser source (not shown). 
     The second optical fiber  22  is connected to the tapered end  21   a  of the optical fiber bundle  21 , and the optical fiber bundle  21  is converged to the second optical fiber  22  to form an optical fiber structure including the optical fiber bundle  21  and the second optical fiber  22 . 
     In an embodiment, a first cross-sectional area A 1  (as shown in  FIG.  2 A ) of the tapered top surface T of the tapered end  21   a  of the optical fiber bundle  21  (as shown in  FIG.  2 B- 2   ) and a second cross-sectional area A 2  (as shown in  FIG.  2 A ) of the cross section  22   c  of the second optical fiber  22  (as shown in  FIG.  2 B- 3   ) are equal. 
     Furthermore, a ratio D of the Mode Field Diameter (MFD) of the connection (or fusion splice) between a mode field diameter d 1  of the tapered top surface T of the tapered end  21   a  of the optical fiber bundle  21  and a mode field diameter d 2  of the second optical fiber  22  is 1±0.1, which is between 0.9 and 1.1 (such as 0.9&lt;D&lt;1.1). As shown in  FIG.  2 C , the ratio D of the mode field diameter d 1  of the tapered top surface T of the tapered end  21   a  of the optical fiber bundle  21  to the mode field diameter d 2  of the second optical fiber  22  is d 1 /d 2 . 
     Please refer to  FIG.  2 D . A taper angle α of the optical fiber bundle  21  is referred to as the taper angle of the tapered end  21   a  (that is, the extension and intersection point of a tapered peripheral surface  21   c ), which is less than twice the light incident acceptable angle of the second optical fiber  22 , which satisfies the following formula: 
       0&lt;α&lt;2×[90°−θ c ]
 
     where θ c =sin −1  (1/n), which represents the critical angle of light incident that satisfies the total reflection condition, and n is expressed as a refractive index of the first optical fiber  210  (which is the same as the refractive index of the second optical fiber  22 ), and where a critical angle of light incidence θ c  is a total reflection angle of light transmitted in the second optical fiber  22 , and the acceptable angle is determined by the refractive index n of the first optical fiber  210  (that is, different refractive index n will have different acceptable angles). 
     Referring to  FIG.  2 A , the housing  20  accommodates the plurality of first optical fibers  210  and the second optical fiber  22 , and has a light-absorbing area B corresponding to the end of the second optical fiber  22 , so that the second optical fiber  22  is located between the optical fiber bundle  21  and the light-absorbing area B, so that the light-absorbing area B absorbs a scattering signal F 1  escaped and scattered when signals are transmitted from the plurality of first optical fibers  210  to the second optical fiber  22  (as shown in  FIG.  3   ). 
     In an embodiment, the light-absorbing area B is made of black material, such as black anode aluminum, to facilitate the absorption of the scattering signal F 1 . For example, the light-absorbing area B is arranged on the housing  20  in front of the end of the second optical fiber  22  and extends to the housing  20  around the end to present a mask shape. 
     The photoelectric sensor  23  is configured corresponding to the plurality of first optical fibers  210  and is provided in the housing  20  to receive a target signal F 2  escaped and refracted when the signals are transmitted from the second optical fiber  22  to the plurality of first optical fibers  210  (as shown in  FIG.  3   ). 
     In an embodiment, the photoelectric sensor  23  is arranged corresponding to a tapered bottom  21   b  of the optical fiber bundle  21 . For example, the photoelectric sensor  23  is arranged outside the tapered bottom  21   b  of the optical fiber bundle  21  (such as the oblique rear of the tapered top surface T, which is roughly along the tapered peripheral surface  21   c  toward the direction of the tapered bottom  21   b  and intersects with the extended imaginary line of the tapered peripheral surface  21   c ), and its position relative to the optical fiber bundle  21  satisfies the following formula: 
       0&lt;β&lt;2×[90°−(αa/2)]
 
     where, as shown in  FIG.  2 D , β is expressed as an angle between the tapered top surface T of the tapered end  21   a  (e.g., extended dashed line as shown in  FIG.  2 D ) and the tapered peripheral surface  21   c , so that an extended imaginary line of the tapered peripheral surface  21   c  passes through the photoelectric sensor  23 . 
     Please also refer to  FIG.  3    together. During the operation of the optical fiber module  2 , an optical signal S (such as a laser signal) enters the second optical fiber  22  from the second ports  210   b  of the first optical fibers  210  through the first port  210   a , so as to be transmitted to the required place by the second optical fiber  22 . 
     In an embodiment, since the plurality of first optical fibers  210  form the optical fiber bundle  21  having the tapered end  21   a , the optical signals S will enter the second optical fiber  22  at various incident angles. For instance, a light incident angle θ 1  of the first optical fiber  210  satisfies a critical light incident angle θ c  of the total reflection condition (for example, the transmission path S 3  of the incident light is free from being parallel to the tapered peripheral surface  21   c ), and the light incident angle θ 1  is an angle between the transmission path S 3  of the incident light and a normal line L 3 , that is, θ 1 =θ c , and the transmitted optical signal F 3  will be completely transmitted (along the surface of the second optical fiber  22 ) without escaping the second optical fiber  22 . In addition, when a light incident angle θ 2  of the first optical fiber  210  is less than the critical light incident angle θ c  (for example, the transmission path S 1  of the incident light is parallel to the tapered peripheral surface  21   c ), and the light incident angle θ 2  is an angle between the transmission path S 1  of the incident light and the normal line L 1 , the transmitted light signal will generate a scattering signal Fl at the second optical fiber  22  due to refraction (such as the normal line L 1  of the surface of the second optical fiber  22 ), and the scattering signal F 1  is absorbed by the light-absorbing area B. 
     After the light is outputted from the second optical fiber  22 , it hits a highly reflective material (for example, a metal material/optical fiber material, but not limited to this), and thus reflects back to the second optical fiber  22  to generate reflected light R 2 , R 4 . Therefore, the reflected light R 2 , R 4  will be refracted when passing through the optical fiber bundle  21 , so as to escape from the different parts of the tapered peripheral surface  21   c  of the optical fiber bundle  21 . The reflected light R 2 , R 4  may be located on different first optical fibers  210 , as the target signals F 2 , F 4  shown in  FIG.  3   , so that the photoelectric sensor  23  receives the target signals F 2 , F 4 . It should be understood that the reflected light R 2 , R 4  escape to the outside of the first optical fibers  210  according to the refractive index n of the first optical fibers  210 , where tube walls of the first optical fibers  210  define normal lines L 2 , L 4 , to present the linear path of the reflected light R 2 , R 4  in the optical fiber bundle  21  (such as a refraction manner). 
     Therefore, the optical fiber bundle  21  according to the present disclosure can be used to change the taper angle of the tapered end  21   a , so that the scattering signal F 1  of the incident light has an independent propagation direction. 
     Furthermore, the geometric structure mismatch of the optical fiber bundle  21  is used to make the target signals F 2 , F 4  of the reflected light R 2 , R 4  have independent propagation directions, and the photoelectric sensor  23  is arranged on the scattering path thereof to detect the target signals F 2 , F 4 . In one embodiment, the photoelectric sensor  23  is located on an extended tangent line of the tapered peripheral surface  21   c , and the surface of the photoelectric sensor  23  intersects the extended imaginary line. 
     Furthermore, the light-absorbing area B is arranged on the scattering path of the scattering signal F 1  of the incident light, so as to facilitate the absorption of the scattering signal F 1  generated by the optical signal S. 
       FIG.  4    is a schematic diagram of a thermal response of the manufacturing method of the optical fiber module  2  according to the present disclosure when the optical fiber bundle  21  is made. In an embodiment, the optical fiber is made of glass material, and the optical fiber bundle  21  adopts a special asymmetric heating method to control the taper angle of the first optical fibers  210  for merging, and the optical fiber bundle  21  is fused to a second optical fiber  22  as an output. As shown in  FIG.  4   , the horizontal axis represents the heating time (in seconds), and the vertical axis represents the surface heating intensity (that is, heat flux or heat flow rate), and its unit is watts per square meter (W/m 2 ). 
     First, the plurality of first optical fibers  210  are bundled, and then the optical fiber fusion splicer is used to perform the pre-cleaning discharge modulation operation to clean the surface of the plurality of first optical fibers  210  (such as glass dust), as a first time period T 1  shown in  FIG.  4   , so as to clean up through different heating intensities. 
     In an embodiment, the glass dust on the surface of the first optical fiber  210  can be slowly (a first cleaning time course t 1  shown in  FIG.  4   ) cleaned with a weaker heating intensity (a cleaning energy e 1  shown in  FIG.  4   ), and then the glass dust can be quickly hit (a second cleaning time course t 2  shown in  FIG.  4   , the second cleaning time course t 2  is less than the first cleaning time course t 1 , and the second cleaning time course t 2  is a short pulse) on a local surface of the first optical fiber  210  with a stronger heating intensity (a cleaning energy e 2  shown in  FIG.  4   ). It should be understood that the main material of the optical fiber is glass, but the required materials can be added as required to form a variety of composite materials. Therefore, when performing the pre-cleaning discharge modulation operation, the required heating intensity and cleaning time course are coordinated with the structure adjustment of the composite material, and are not limited to the relative relationship in  FIG.  4   . 
     Next, a medium energy is used to perform high and low discharge operations to generate step discharge (a second time period T 2  as shown in  FIG.  4   ), which softens the glass material and melts the plurality of first optical fibers  210 , and then swings and tapers the fused plurality of first optical fibers  210  to stabilize the passive first optical fibers  210  in the process, whereby the fused plurality of first optical fibers  210  are tapered and swung to form an optical fiber bundle  21  having a tapered end  21   a.    
     In an embodiment, the step discharge includes a first energy E 1  and a second energy E 2 . As shown in  FIG.  4   , the second energy E 2  is greater than the first energy E 1 , and the occurrence time of the first energy E 1  is earlier than the occurrence time of the second energy E 2 , wherein the first energy E 1  and the second energy E 2  are continuous. For example, the first energy E 1  is greater than the cleaning energies e 1 , e 2  of the first time period T 1 . It should be understood that there are many types of composite materials of the optical fiber, so the relative relationship (strong or weak) between the first energy E 1  and the cleaning energy in the first time period T 1  is not limited to the above. 
     Next, a high-energy system is used to perform phased discharge to generate periodic discharge (a third time period T 3  as shown in  FIG.  4   ) to improve or strengthen the structural strength of the tapered optical fiber bundle  21 , especially for the structure of thinner parts. 
     In an embodiment, the heating manner of the third time period T 3  adopts a heating and cooling alternate manner, such as annealing, to strengthen the structural strength of the optical fiber bundle  21 . For example, the third time period T 3  is divided into four heating courses h and three cooling courses c, and the heating intensity of the heating course h is defined as a third energy E 3 , which is less than the first energy E 1 . It should be understood that there are many types of composite materials for the optical fiber, so the heating intensity and heating and cooling time courses required for the third time period T 3  can be coordinated with the structure adjustment of the composite material, and are not limited to the relative relationship and the number of heating and cooling times in  FIG.  4   , and the relative relationship (strong or weak) between the third energy E 3  and the energy of the second time period T 2  is not limited to the above. 
     Furthermore, a cleave manner is used to remove excess parts of the plurality of first optical fibers  210 , so as to obtain the optical fiber bundle  21 . 
     After that, the second optical fiber  22  is connected to the tapered end  21   a  of the optical fiber bundle  21  in a splice manner such as fusion, and then the optical fiber bundle  21  and the second optical fiber  22  are housed/accommodated together in a housing  20 , and the light-absorbing area B and the photoelectric sensor  23  are arranged in the housing  20 . 
     Therefore, the manufacturing method of the optical fiber module according to the present disclosure is to weld the second optical fiber  22  and the optical fiber bundle  21  by heating to form an asymmetrical shape (tapered optical fiber bundle  21  and single second optical fiber  22 ) by the asymmetry of the intensity of the discharge and the time course (as shown in  FIG.  4   , the cleaning energy e 1  of the first cleaning time course t 1  is different from the cleaning energy e 2  of the second cleaning time course t 2 ). The mismatch and angle change of the opposite sides of the optical fiber geometry structure at the welded location make the scattering signal F 1  of the incident light and the target signals F 2 , F 4  of the reflected light have a specific propagation direction, and the photoelectric sensor  23  is arranged on the transmission path of the reverse scattering signals (that is, the target signals F 2 , F 4 ) to detect the reflected power. It should be understood that the asymmetric heating manner is to bring a plurality of first optical fibers  210  together in a molten state to be tapered, and close the first optical fibers  210  to expand the propagation field toward the second optical fiber  22 , so that an effective power coupling occurs in the region of the extremely short tapered end  21   a.    
     In summary, the optical fiber module  2  according to the present disclosure and manufacturing method thereof are achieved by integrating the photoelectric sensor  23  and the optical fiber structure (that is, the optical fiber bundle  21  and the second optical fiber  22 ) in a housing  20 , to form a laser light-collecting element (that is, the optical fiber module  2 ) with a built-in reflected power detection function (that is, the photoelectric sensor  23 ). As such, the optical fiber module  2  according to the present disclosure not only has the performance of multi-beam laser light combining, but also can simultaneously capture and detect the reflected power signal inside. Therefore, the optical fiber module  2  according to the present disclosure can be installed at the laser source of a laser machine to directly detect the value of the reflected power, so that the value of the reflected power encountered by the laser source can be accurately determined, which can be used as a protection mechanism for the laser source to distinguish, so as to achieve the purpose of a single optical element (that is, the optical fiber nodule  2 ) with the laser beam combining performance and the reflected power detection function. 
     The foregoing embodiments are used for the purpose of illustrating the principles and effects only rather than limiting the present disclosure. Anyone skilled in the art can modify and alter the above embodiments without departing from the spirit and scope of the present disclosure. Therefore, the range claimed by the present disclosure should be as described by the accompanying claims listed below.