Optical element with attenuation region and method for manufacturing same

Abstract

An optical element is provided which optically couples a light-receiving element and light-emitting element that functions as a light source, and which can be easily manufactured and realizes a desired attenuation rate with high precision.　This optical element is provided with an incident surface (S1) configured opposite of the light source and an exit surface (S2) configured opposite of said light-receiving element so as to optically couple the light source (L0) and the light-receiving element which receives light from the light source, wherein the light incident from the light source onto the incident surface forms a first image (L1) of the light source inside the optical element, and forms a second image (L2) of the light source after emission from the exit surface, and, near the position where said first image (L1) is formed, the optical element has an attenuation region that reduces the amount of transmitted light.

Description

[Technical field]

[0001] The present invention relates to an optical element with an attenuation region and a method for manufacturing the same. [Background technology]

[0002] In the field of optical communications, optical elements (optical modules) that optically couple a light-emitting element and a light-receiving element that function as a light source are used. When using such optical elements, there are cases where it is required to attenuate the amount of light passing through at a desired attenuation rate from the viewpoint of safety and standards. In order to attenuate the amount of light at a desired attenuation rate, optical elements that have a light attenuation film on the surface through which light passes (Patent Document 1), optical elements that have a shape that diffuses light inside (Patent Document 2), and the like have been developed.

[0003] However, the number of steps and costs required to manufacture an optical element with a film are increased. In addition, in the case of an optical element having a shape that diffuses light internally, there is a possibility that noise due to the diffused light increases. In addition, in either method, it is not easy to achieve a desired attenuation rate with high precision.

[0004] Thus, no optical element that optically couples a light-emitting element functioning as a light source with a light-receiving element, which can be easily manufactured, and which realizes a desired attenuation rate with high accuracy, and a manufacturing method thereof have been developed. Therefore, there is a need for an optical element that optically couples a light-emitting element functioning as a light source with a light-receiving element, which can be easily manufactured, and which realizes a desired attenuation rate with high accuracy, and a manufacturing method thereof. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 11-119063 [Patent Document 2] Patent Publication 2008-145678 Summary of the Invention [Problem to be solved by the invention]

[0006] The technical object of the present invention is to provide an optical element that optically couples a light-emitting element that functions as a light source and a light-receiving element, which can be easily manufactured and achieves a desired attenuation rate with high precision, and a method for manufacturing the same. [Means for solving the problem]

[0007] An optical element of a first aspect of the present invention is an optical element having an entrance surface configured to face a light source and an exit surface configured to face a light receiving element so as to optically couple the light source to a light receiving element that receives light from the light source, wherein light incident on the entrance surface from the light source forms a first image of the light source within the optical element, and after exiting from the exit surface, forms a second image of the light source, and an attenuation region is provided near the position where the first image is formed to reduce the amount of light passing through.

[0008] The optical element of this embodiment is an optical element that optically couples a light-emitting element that functions as a light source with a light-receiving element, and can be easily manufactured, while achieving a desired attenuation rate with high precision.

[0009] The optical element according to the first embodiment of the first aspect of the present invention is configured such that at least one of the entrance surface and the exit surface faces an optical fiber via a ferrule.

[0010] In the optical element of the second embodiment of the first aspect of the present invention, the optical axis is a path of a light ray passing through the center of the entrance surface and the exit surface, the design distance along the optical axis between the light source and the entrance surface is a, the distance along the optical axis between the entrance surface and the exit surface is l, the design distance along the optical axis between the exit surface and the second image is d, the focal length of the entrance surface on the light source side is f1, the focal length of the exit surface on the light receiving element side is f2, and the refractive index of the optical element is n.

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[0011] A second aspect of the present invention relates to a method for manufacturing an optical element, which comprises an entrance surface configured to face a light source and an exit surface configured to face a light receiving element that receives light from the light source so as to optically couple the light source to the light receiving element, and which comprises an attenuation region therein, the method including the steps of: manufacturing an optical element shaped so that light incident on the entrance surface from the light source forms a first image of the light source within the optical element, and forms a second image of the light source after exiting from the exit surface; and forming an attenuation region that reduces the amount of light passing through near the position where the first image is formed by irradiating laser light through the entrance surface or the exit surface.

[0012] According to the manufacturing method of the optical element of this aspect, an optical element that realizes a desired attenuation rate with high precision can be easily manufactured.

[0013] In the method for manufacturing an optical element of the first embodiment of the second aspect of the present invention, at least one of the incident surface and the exit surface is configured to face an optical fiber via a ferrule, and in the step of forming the attenuation region, the laser light is irradiated via the ferrule and the incident surface or the exit surface.

[0014] According to this embodiment, in the step of forming the attenuation region, the irradiation position of the laser light can be positioned with high accuracy by the ferrule.

[0015] In the method for manufacturing an optical element according to the second embodiment of the second aspect of the present invention, the optical element is a receiving optical element, and in the step of forming an attenuation region, a fiber laser is placed at the position of the optical fiber during operation and the laser light is irradiated through the incident surface.

[0016] According to this embodiment, in the step of forming the attenuation region, a fiber laser is placed at the position of the optical fiber during operation and laser light is irradiated through the incident surface, so that the attenuation region can be formed approximately at the position of the first image.

[0017] In the manufacturing method of an optical element of the third embodiment of the second aspect of the present invention, the optical element is a transmitting optical element, and in the step of forming an attenuation region, a fiber laser is placed at approximately the position of the second image during operation and the laser light is irradiated via the exit surface.

[0018] According to this embodiment, in the step of forming the attenuation region, a fiber laser is placed at approximately the position of the second image during operation and the laser light is irradiated through the exit surface, so that the attenuation region can be formed at approximately the position of the first image. [Brief description of the drawings]

[0019] [Figure 1] 1 is a perspective view showing an optical element according to an embodiment of the present invention; [Diagram 2] 1 is a perspective view showing an optical element, an optical fiber, and a ferrule used to optically connect the optical element and the optical fiber according to an embodiment of the present invention. [Diagram 3] 1 is a plan view of an optical element, an optical fiber, and a ferrule used to optically connect the optical element and the optical fiber according to an embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view of the section AA in FIG. [Diagram 5] FIG. 4 is a cross-sectional view of FIG. [Figure 6] FIG. 5 is an enlarged view of part C in FIG. [Figure 7] FIG. 6 is an enlarged view of a portion D in FIG. 5. [Figure 8] FIG. 2 is a diagram showing a paraxial imaging optical system model of an optical system of the optical element of the present invention. [Figure 9] 4 is a diagram showing the paths of light rays during operation of the optical element of Example 1. FIG. [Figure 10]4 is a diagram showing a light path when an attenuation region is formed in the optical element of Example 1. FIG. [Figure 11] 1 is a diagram showing an example of a cross section including a light path when an attenuation region is formed in an optical element having a reflecting surface similar to the first embodiment. FIG. [Figure 12] 13 is a diagram showing another example of a cross section including a light path when an attenuation region is formed in an optical element having a reflecting surface similar to the first embodiment. FIG. [Figure 13] FIG. 11 is a diagram showing the paths of light rays during operation of the optical element of the second embodiment. [Figure 14] 11 is a diagram showing an example of a cross section including a light path during operation of an optical element not including a reflecting surface, similar to the second embodiment. FIG. [Figure 15] FIG. 11 is a diagram showing a light path when an attenuation region is formed in the optical element of Example 2. [Figure 16] FIG. 11 is a diagram showing an example of a cross section including a light path when an attenuation region is formed in an optical element not provided with a reflecting surface, similarly to the second embodiment. [Figure 17] 1 is a flow chart illustrating a method for manufacturing an optical element having an entrance surface configured to face a light source and an exit surface configured to face a light receiving element to optically couple the light source and the light receiving element that receives light from the light source, the optical element having an attenuation region that reduces the amount of light passing therethrough. [Figure 18] FIG. 2 is a diagram showing an optical system when an optical element is in operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] FIG. 1 is a perspective view showing an optical element 100 according to one embodiment of the present invention.

[0021] FIG. 2 is a perspective view showing an optical element 100, an optical fiber 210, and a ferrule 220 used to optically connect the optical element 100 and the optical fiber 210 according to one embodiment of the present invention.

[0022] FIG. 3 is a plan view of the optical element 100, the optical fiber 210, and the ferrule 220 used to optically connect the optical element 100 and the optical fiber 210 shown in FIG.

[0023] FIG. 4 is a cross-sectional view taken along line AA of FIG.

[0024] FIG. 5 is a cross-sectional view taken along line BB in FIG.

[0025] 6 is an enlarged view of part C in FIG. 4. According to FIG. 6, the light receiving side lens 110 of the optical element 100 is disposed so as to face the optical fiber 210, and the emission side lens 120 of the optical element 100 is disposed so as to face the light receiving element 300. The light emitted from the optical fiber 210 and incident on the light receiving side lens 110 is reflected by the total reflection surface R, and is collected by the emission side lens 120 in the vicinity of the light receiving surface of the light receiving element 300. The light receiving side lens 110 and the emission side lens 120 form a light receiving side lens array and an emission side lens array, respectively. Light from one of the multiple optical fibers passes through one light receiving side lens facing the optical fiber and one emission side lens corresponding to the light receiving side lens, and reaches one light receiving element facing the emission side lens. One light receiving side lens and one emission side lens are also referred to as the entrance surface and the exit surface, respectively, of the optical element.

[0026] Fig. 7 is an enlarged view of part D in Fig. 5. According to Fig. 7, the optical element 100 and the ferrule 220 are aligned and fixed by fitting the ferrule fitting pin 105 of the optical element 100 into the hole of the ferrule 220. As a result, the optical fiber 210 and the incident surface 110 are aligned with high accuracy.

[0027] In general, the optical element 100 of the present invention is configured to optically couple a light source and a light receiving element. When the optical element 100 is used for transmission, the light source is a semiconductor optical element such as a VCSEL (Vertical Cavity Surface Emitting LASER), The light receiving element is an optical fiber.When the optical device 100 is used for reception, the light source is an optical fiber and the light receiving element is a semiconductor optical element such as a photodiode.

[0028] The optical element described with reference to FIGS. 1-6 is a receiving optical element. When used for such purposes, the incident surface faces the semiconductor optical element such as a VCSEL, which is the light source, and the output surface faces the semiconductor optical element such as a VCSEL. The light-receiving surface faces the end face of an optical fiber, which is a light-receiving element.

[0029] The features of the optical system of the optical element of the present invention will be described using a paraxial imaging optical system model. As described above, the entrance surface of the optical element faces the light source, and the exit surface of the optical element faces the light receiving element.

[0030] Fig. 8 is a diagram showing a paraxial imaging optical system model of the optical system of the optical element of the present invention. The optical system of the optical element is configured to form a first image L1 of the light source L0 inside the optical element, and a second image L2 of the light source L0 outside the optical element. Here, the path of the light ray passing through the centers of the light source L0, the entrance surface S1, and the exit surface S2 is defined as the optical axis of the optical system. Note that Fig. 8 shows only the part of the light source and its image above or below the optical axis.

[0031] In order to form a first image L1 of the light source L0 inside the optical element and a second image L2 of the light source L0 outside the optical element, the optical system must satisfy the following conditions.

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[0032] Next, let us consider the conditions for the light beam to be contained within the exit surface S2. In order for the light beam to be contained within the exit surface S2, the optical system must satisfy the following conditions.

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[0033] Moreover, when the condition for the light beam to be contained within the emission surface S2 is considered only with respect to the chief ray, the following formula is obtained.

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[0034] Next, let us consider the conditions for the light beam to fit within the fiber end face, assuming that the light receiving element is an optical fiber. If we assume that the second image L2 of the light source L0 is formed on the end face of the optical fiber, the optical system must satisfy the following conditions for the light beam to fit within the fiber core.

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[0035] From equations (4) and (6), in order for the light beam to be contained within the exit surface and the fiber core, the following condition must be satisfied:

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[0036] Furthermore, if the angle that the chief ray at the maximum image height makes with the optical axis is denoted as α, the following relationship holds from FIG. 8:

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[0037] An embodiment of the present invention will be described below. In the embodiment, the shape of the lens surface is defined by the following formula.

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[0038] Example 1 9 is a diagram showing the path of light rays when the optical element of the first embodiment is in operation. The optical element of the first embodiment has an entrance surface S1 configured to face the light source L0 and an exit surface S2 configured to face the light receiving element so as to optically couple the light source L0 and the light receiving element. The optical element of the first embodiment is a transmitting optical element, the light source is a VCSEL, and the light receiving element is an optical fiber. The optical element of the first embodiment has a reflecting surface R inside. The light emitted from the VCSEL is reflected by the optical element. After forming an image (first image) L1 of the light source within the element, it is totally reflected by the reflecting surface R, passes through the exit surface S2, and then forms an image (second image) L2 of the light source L0 near the end face of the optical fiber. In the optical system shown in Figure 9, the light source L0 and the second image L2 are in a conjugate relationship. In Figure 9, the solid line indicates the light beam emitted from the center of the light source, and the dotted line indicates the light beam emitted from a point 5 μm high from the center of the light source.

[0039] Table 1 shows data used in equations (1)-(8) of the optical system of Example 1. In Table 1, the unit of length is millimeters. In addition, since a paraxial imaging optical system model is used, sine The value of (sin θ0) is approximately equal to the value of the angle (θ0) expressed in radians. [Table 1]

[0040] According to Table 1, equations (1)-(3), (7) and (8) are satisfied.

[0041] Table 2 shows the shape of each surface, the distance between the surfaces, and the material and refractive index of the lens in the first embodiment. [Table 2]

[0042] In Table 2 and Table 4 below, PEI stands for polyetherimide.

[0043] Next, a method for forming an attenuation region in an optical element will be described. When forming an attenuation region, high-intensity laser light such as a fiber laser is irradiated from the emission surface S2 of the transmitting optical element during operation via a ferrule. Since the emission surface S2 of the transmitting optical element during operation is configured to be connected to an optical fiber via a ferrule during operation, the ferrule used during operation can be used as is for the fiber laser when forming the attenuation region. Therefore, the alignment of the light source of high-intensity laser light such as a fiber laser with respect to the optical element can be performed with high accuracy.

[0044] Fig. 10 is a diagram showing the ray path when the attenuation region of the optical element of the first embodiment is formed. In the optical system of Fig. 10, a light source L0' such as a fiber laser is located approximately at the position of the second image of the optical system of Fig. 9. As described above, in the optical system shown in Fig. 9, the light source and the second image are in a conjugate relationship, so that in the optical system of Fig. 10, a high-intensity laser beam is also emitted approximately at the position of the first image of the optical system of Fig. 9. Image of light source L 1 ’As a result, the refractive index or transmittance of the resin (plastic) at the position where the image of the high-intensity laser light source is formed changes, creating an attenuation region. In Figure 10, the solid line indicates the light beam emitted from the center of the light source, and the dotted line indicates the light beam emitted from a point 5 μm high from the center of the light source.

[0045] Fig. 11 is a diagram showing an example of a cross section including a light path when an attenuation region is formed in an optical element having a reflecting surface similar to Example 1. In Fig. 11, the intensity of laser light emitted from fiber laser 211 and passed through optical element 100 is measured by photodiode 310.

[0046] Fig. 12 is a diagram showing another example of a cross section including a light path when an attenuation region is formed in an optical element having a reflecting surface similar to Example 1. In Fig. 12, the intensity of the laser light emitted from fiber laser 211 and passed through optical element 100 is measured by power meter 320.

[0047] As shown in Figures 11 and 12, an attenuation region with a desired attenuation rate can be created by adjusting at least one of the intensity and irradiation time of the fiber laser 211 while measuring the intensity of the laser light emitted from the fiber laser 211 and passed through the optical element 100.

[0048] If the first image of the optical element of the first embodiment is located near the reflecting surface R, the path of the light beam may pass through the attenuation region twice, resulting in excessive light attenuation. In addition, if the light beam diameter at the reflecting surface R is small, the optical performance may be significantly degraded due to local shape errors in the light beam position at the reflecting surface R. Therefore, it is preferable that the first image of the optical element is located on the optical axis at least the height h1 of the first image L1 away from the reflecting surface R.

[0049] Example 2 13 is a diagram showing the path of light rays during operation of the optical element of Example 2. The optical element of Example 2 has an entrance surface S1 configured to face the light source L0 and an exit surface S2 configured to face the light receiving element so as to optically couple the light source L0 and the light receiving element. The optical element of Example 2 is a transmitting optical element, the light source is a VCSEL, and the light receiving element is an optical fiber. The optical element of the second embodiment does not have a reflective surface inside. The light emitted from the VCSEL is After an image (first image) L1 of the light source L0 is formed within the optical element, it passes through the exit surface S2 and then forms an image (second image) L2 of the light source near the end face of the optical fiber. In the optical system shown in Figure 13, the light source L0 and the second image L2 are in a conjugate relationship. In Figure 13, the solid line indicates the light beam emitted from the center of the light source, and the dotted line indicates the light beam emitted from a point 5 μm high from the center of the light source.

[0050] 14 is a diagram showing an example of a cross section including a light path during operation of an optical element that does not have a reflecting surface, similar to the second embodiment. The incident surface S1 faces a VCSEL indicated as LD, and the exit surface S2 faces an optical fiber. It faces Iba 210.

[0051] Table 3 shows the data used in the formulas (1)-(8) of the optical system of Example 2. In Table 3, the unit of length is millimeters. In addition, since a paraxial imaging optical system model is used, sine The value of (sin θ0) is approximately equal to the value of the angle (θ0) expressed in radians. [Table 3]

[0052] According to Table 3, equations (1)-(3), (7) and (8) are satisfied.

[0053] Table 4 shows the shape of each surface, the distance between the surfaces, and the material and refractive index of the lens in the second embodiment. [Table 4]

[0054] Next, a method for forming an attenuation region in the optical element of the second embodiment will be described. When forming an attenuation region, high-intensity laser light such as a fiber laser is irradiated from the emission surface S2 during operation via a ferrule. Since the emission surface S2 during operation of the transmitting optical element is configured to be connected to an optical fiber via a ferrule during operation, the ferrule used during operation can be used as is for the fiber laser when forming the attenuation region. Therefore, the alignment of the light source of high-intensity laser light such as a fiber laser with respect to the optical element can be performed with high accuracy.

[0055] FIG. 15 is a diagram showing the ray path when the attenuation region of the optical element of the second embodiment is formed. In the optical system of FIG. 15, a light source L0' such as a fiber laser is located at approximately the position of the second image of the optical system of FIG. 13. As described above, in the optical system shown in FIG. 13, the light source and the second image are in a conjugate relationship, so that in the optical system of FIG. 15, an image L1' of the light source of high-intensity laser light is formed at approximately the position of the first image of the optical system of FIG. 13. Therefore, the refractive index or transmittance of the resin (plastic) at the position where the image of the light source of high-intensity laser light is formed changes, and an attenuation region is created. In FIG. 15, the solid line indicates the light ray emitted from the center of the light source, and the dotted line indicates the light ray emitted from a point 5 μm high from the center of the light source.

[0056] 16 is a diagram showing an example of a cross section including a light path when an attenuation region is formed in an optical element that does not have a reflecting surface, similar to Example 2. An incident surface S1 of the transmitting optical element 100 faces a light receiving surface for monitoring the light amount of the power meter 320, and an exit surface S2 of the transmitting optical element 100 faces a fiber laser 211 that is a light source.

[0057] Method for manufacturing an optical element with an attenuation region that reduces the amount of light passing therethrough - Patents.com FIG. 17 is a flow chart illustrating a method for manufacturing an optical element having an entrance surface configured to face a light source and an exit surface configured to face a light receiving element to optically couple the light source and the light receiving element that receives light from the light source, the optical element having an attenuation region that reduces the amount of light passing therethrough.

[0058] In step S1010 of Figure 17, an optical element is manufactured having a shape determined so that light incident from a light source on the entrance surface forms a first image of the light source within the optical element, and after exiting from the exit surface, forms a second image of the light source externally.

[0059] By determining the shape of the optical element so as to satisfy the formulas (1) to (3), In an optical system consisting of a light source and a light receiving element, light incident on the entrance surface from a light source can be made to form a first image of the light source inside the optical element, and after emerging from the exit surface, form a second image of the light source outside. Furthermore, by satisfying formula (7), the light flux is contained within the exit surface and the light receiving surface of the light receiving element. Furthermore, when the light receiving element is an optical fiber, there is no light loss in the optical fiber if formula (8) is satisfied.

[0060] In step S1020 of Fig. 17, an attenuation region for reducing the amount of light passing through is formed around the position where the first image is formed by irradiating the laser light from the entrance surface or the exit surface. It is preferable to use a fiber laser as a light source of the laser light, and irradiate the laser light through one of the entrance surface and the exit surface that faces the optical fiber during operation. The ferrule used during operation can be used to determine the irradiation position of the fiber laser with high accuracy.

[0061] In the case of a transmitting optical element, a fiber laser is provided on the output side where an optical fiber is provided during operation when the attenuation region is formed, to form the attenuation region. By disposing the fiber laser at approximately the position of the second image, the attenuation region can be formed in the vicinity of the first image. In the case of a receiving optical element, a fiber laser is provided on the input side where an optical fiber is provided during operation when the attenuation region is formed, to form the attenuation region. By disposing the fiber laser at the position where an optical fiber is provided during operation, the attenuation region can be formed in the vicinity of the first image.

[0062] As an example, fiber laser power ranges from 20kw to 70kw.

[0063] In general, the material of the optical element is preferably a resin (plastic) such as PEI (polyetherimide), PI (polyimide) and PESU (PES) (polyethersulfone). The optical element can be manufactured integrally by injection molding using the above materials.

[0064] By using the above method, it is possible to form an attenuation region with any attenuation rate in the range of 0% to 100%. In general, the attenuation rate in a communication optical system is in the range of 90% to 25.5% (-0.5 dB to -6.0 dB).

[0065] Here, the relationship between the position of the second image of the light source and the position of the light receiving surface during operation will be described.

[0066] FIG. 18 is a diagram showing the optical system of the optical element during operation. As described above, the optical system of the optical element during operation is configured so that the second image L2 of the light source L0 is formed on the light receiving surface of the light receiving element or the end face of the optical fiber. In FIG. 18, the position of the second image is indicated by A. In the case of a transmitting optical element, when the end face of the optical fiber is placed at A, the light source and the end face of the optical fiber are in a conjugate relationship. Therefore, in the case of a transmitting optical element, a fiber laser is placed at A when forming an attenuation region, and the light beam of the fiber laser is focused at the position of the first image during operation to form an attenuation region.

[0067] 18, the position at which the diameter of the light beam emerging from the optical element is smallest is indicated by B. It is also possible to position the light receiving surface or the end face of the optical fiber at B. In this case, the allowable accuracy of aligning the light receiving surface or the end face of the optical fiber becomes larger.

[0068] In the case of a transmitting optical element, if a fiber laser is installed at B when forming the attenuation region, the attenuation efficiency during operation decreases because the fiber laser light beam cannot be focused at the position of the first image during operation to form the attenuation region. Therefore, some ingenuity, such as an adapter, is required to install the fiber laser at A when forming the attenuation region.

[0069] In the case of a receiving optical element, the fiber laser is placed at the position of the optical fiber during operation when the attenuation region is formed, so the above problem does not occur in the case of a transmitting optical element. Therefore, the position of the light receiving surface of the light receiving element can be determined so that the diameter of the light beam is smaller than the diameter of the light receiving surface.

[0070] With respect to the location of the attenuation region, "near the location of the first image" means that the distance along the optical axis of each point of the attenuation region from the location of the first image on the optical axis is within + / - 15% of the distance along the optical axis from the entrance surface to the exit surface of the optical element. More preferably, the distance along the optical axis from the position of the image on the optical axis is within + / - 5% of the distance along the optical axis from the entrance surface to the exit surface of the optical element.

[0071] During operation, "forming a second image of the light source near the light receiving surface" means forming a second image of the light source at a position on the optical axis such that the light receiving surface of the light receiving element can receive a sufficient amount of light from the light beam.

Claims

1. 1. A method for manufacturing an optical element having an entrance surface configured to face a light source and an exit surface configured to face a light receiving element that receives light from the light source so as to optically couple the light source and the light receiving element, the optical element having an attenuation region therein, the method comprising the steps of: manufacturing an optical element shaped such that light incident on the entrance surface from the light source forms a first image of the light source within the optical element and forms a second image of the light source after exiting from the exit surface; and forming an attenuation region that reduces the amount of light passing through in the vicinity of a position where the first image is formed by irradiating laser light through the incident surface or the exit surface.

2. 2. The method for manufacturing an optical element according to claim 1, wherein at least one of the incident surface and the exit surface is configured to face an optical fiber via a ferrule, and in the step of forming the attenuation region, the laser light is irradiated via the ferrule and the incident surface or the exit surface.

3. 3. The method for manufacturing an optical element according to claim 1, wherein the optical element is a receiving optical element, and in the step of forming the attenuation region, a fiber laser is disposed at the position of the optical fiber during operation and the laser light is irradiated through the incident surface.

4. 3. The method for manufacturing an optical element according to claim 1, wherein the optical element is a transmitting optical element, and in the step of forming an attenuation region, a fiber laser is positioned approximately at the position of the second image during operation and the laser light is irradiated through the exit surface.

5. A method for manufacturing an optical element as described in claim 1, wherein the attenuation rate of the attenuation region is set to a desired value by irradiating the laser light while observing the intensity after passing through the optical element.

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