Inspection method and inspection system

Abstract

The purpose of the present invention is to achieve a fusion splicing method in which, when an optical fiber connector having low coupling efficiency for each core is obtained, the situation can be easily known. A welding connection method (S1) includes a post-welding measurement step (S16) in which, for two multi-core optical fibers (OF1, OF2) whose end surfaces are welded to each other, the position of a mark of one multi-core optical fiber (OF1) is determined on the basis of the direction in which a predetermined first shape appears in a graph indicating the direction dependence of the transmitted light intensity of the one multi-core optical fiber (OF1), and the position of the mark of the one multi-core optical fiber (OF1) is determined on the basis of the direction in which a predetermined first shape appears in the graph indicating the direction dependence of the transmitted light intensity of the one multi-core optical fiber (OF1). And determining the position of the mark of the other multi-core fiber (OF2) on the basis of the direction when a predetermined second shape appears in a graph representing the direction dependence of the transmitted light intensity of the other multi-core fiber (OF2).

Description

Technical Field

[0001] This invention relates to a method and system for inspecting the fusion splice status of two optical fibers. Background Technology

[0002] As a method for connecting optical fibers, fusion splicing can be cited as an example. In fusion splicing, the end faces of two optical fibers are typically joined together, and the joined end faces are heated and melted. Furthermore, the two optical fibers are fused together when the end faces of the two optical fibers solidify through natural cooling. Patent Document 1 is cited as an example of a document that discloses an optical fiber fusion splicing device and a fusion splicing method.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2019 / 163150 Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] In recent years, optical fibers with anisotropic refractive index distribution in their cross-sections have been widely used. Multi-core fibers with multiple cores and PANDA (Polarization-maintaining and Absorption-reducing) fibers with polarization-maintaining functions are examples. To fusion splice such fibers, rotational alignment is required before splicing. In the rotational alignment of two multi-core fibers with markings for identifying core numbers, in addition to aligning the core positions of the two multi-core fibers, the positional relationship of the markings must also meet predetermined conditions. Similarly, in the rotational alignment of two PANDA fibers with stress-imposing sections for polarization maintenance, in addition to aligning the core positions of the two PANDA fibers, the positional relationship of the stress-imposing sections must also meet predetermined conditions.

[0008] One aspect of the present invention is made in view of the above-mentioned problems, and its object is to provide an inspection method or inspection system that can check whether the fusion connection has been properly performed after the fusion connection has been made.

[0009] (II) Technical Solution

[0010] One aspect of the inspection method of the present invention includes a post-fusion splice measurement step, in which, for two multi-core optical fibers with markings formed in the cladding and end faces fused together, the position of the marking of the one multi-core optical fiber is determined according to the direction when a predetermined first shape appears in a curve representing the direction dependence of the transmitted light intensity of one of the two multi-core optical fibers, and the position of the marking of the other multi-core optical fiber is determined according to the direction when a predetermined second shape appears in a curve representing the direction dependence of the transmitted light intensity of the other multi-core optical fiber.

[0011] An inspection system according to one aspect of the present invention comprises: a single light source or multiple light sources; a single photodetector or multiple photodetectors; and a single control unit or multiple control units, wherein the single control unit or at least one of the multiple control units performs a post-fusion splice measurement process using the single light source or at least one of the multiple light sources and the single photodetector or at least one of the multiple photodetectors. In this post-fusion splice measurement process, for two multi-core optical fibers with markings formed in the cladding and their end faces fused together, the position of the marking of the one multi-core optical fiber is determined according to the direction when a predetermined first shape appears in a curve representing the direction dependence of the transmitted light intensity of one of the two multi-core optical fibers, and the position of the marking of the other multi-core optical fiber is determined according to the direction when a predetermined second shape appears in a curve representing the direction dependence of the transmitted light intensity of the other of the two multi-core optical fibers.

[0012] (III) Beneficial Effects

[0013] According to the method of the present invention, it is possible to check whether the fusion connection was properly performed after the fusion connection is completed. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the process of a welding method according to an embodiment of the present invention.

[0015] Figure 2 It indicates that it is used for implementation. Figure 1 A block diagram of the structure of the welding device for the welding welding method shown.

[0016] Figure 3 It means to become Figure 1 The diagram shows an example of a multi-core optical fiber to which the fusion splicing method is applied. Figure 3 (a) is a side view of the multi-core optical fiber. Figure 3 (b) is a front view of one end face of the multi-core optical fiber as viewed from the E1 line of sight. Figure 3(c) is a front view of the other end face of the multi-core optical fiber as seen from the E2 line of sight.

[0017] Figure 4 This is a diagram showing the connection point of two optical fibers that are typically connected. Among them, Figure 4 (a) is a side view of the two optical fibers. Figure 4 (b) is a front view of one end face of the two optical fibers as seen from the E2 line of sight. Figure 4 (c) is a front view of the other end face of the two optical fibers as seen from the E1 line of sight.

[0018] Figure 5 This diagram shows the fusion splice connection of two optical fibers that are not normally connected. Figure 5 (a) is a side view of the two optical fibers. Figure 5 (b) is a front view of one end face of the two optical fibers as seen from the E2 line of sight. Figure 5 (c) is a front view of the other end face of the two optical fibers as seen from the E1 line of sight.

[0019] Figure 6 This diagram shows the fusion splice connection of two optical fibers that are not normally connected. Figure 6 (a) is a side view of the two optical fibers. Figure 6 (b) is a front view of one end face of the two optical fibers as seen from the E2 line of sight. Figure 6 (c) is a front view of the other end face of the two optical fibers as seen from the E1 line of sight.

[0020] Figure 7 This diagram shows the fusion splice connection of two optical fibers that are not normally connected. Figure 7 (a) is a side view of the two optical fibers. Figure 7 (b) is a front view of one end face of the two optical fibers as seen from the E2 line of sight. Figure 7 (c) is a front view of the other end face of the two optical fibers as seen from the E1 line of sight.

[0021] Figure 8 This diagram shows the fusion splice of two optical fibers in a flipped connection (a flipped connection relative to axis L1). Figure 8 (a) is a side view of the two optical fibers. Figure 8 (b) is a front view of one end face of the two optical fibers as seen from the E2 line of sight. Figure 8 (c) is a front view of the other end face of the two optical fibers as seen from the E1 line of sight.

[0022] Figure 9This diagram shows the fusion splice of two optical fibers in a flipped connection (a flipped connection relative to axis L2). Figure 9 (a) is a side view of the two optical fibers. Figure 9 (b) is a front view of one end face of the two optical fibers as seen from the E2 line of sight. Figure 9 (c) is a front view of the other end face of the two optical fibers as seen from the E1 line of sight.

[0023] Figure 10 This diagram shows the fusion splice of two optical fibers in a flip connection (a flip connection relative to axis L3). Figure 10 (a) is a side view of the two optical fibers. Figure 10 (b) is a front view of one end face of the two optical fibers as seen from the E2 line of sight. Figure 10 (c) is a front view of the other end face of the two optical fibers as seen from the E1 line of sight.

[0024] Figure 11 This diagram shows the fusion splice of two optical fibers in a flip connection (a flip connection relative to axis L4). Figure 11 (a) is a side view of the two optical fibers. Figure 11 (b) is a front view of one end face of the two optical fibers as seen from the E2 line of sight. Figure 11 (c) is a front view of the other end face of the two optical fibers as seen from the E1 line of sight.

[0025] Figure 12 (a) indicates that, Figure 4 The graph shows the direction dependence of the transmitted light intensity of two typically connected optical fibers (including multi-core fibers with low refractive index markings). Figure 12 (b) means as Figure 8 The graph shows the direction dependence of the transmitted light intensity of the two optical fibers connected by flipping as shown.

[0026] Figure 13 This is a diagram illustrating a method for estimating the coupling efficiency or connection loss of two optical fibers. Among them, Figure 13 (a) is a side view of the two optical fibers. Figure 13 (b) is a front view of one end face of the two optical fibers as seen from the E2 line of sight. Figure 13 (c) is a front view of the other end face of the two optical fibers as seen from the E1 line of sight.

[0027] Figure 14 (a) indicates that, Figure 4 The graph shows the direction dependence of the transmitted light intensity of two typically connected optical fibers (including multi-core fibers with high refractive index markings). Figure 14 (b) means as Figure 8 The graph shows the direction dependence of the transmitted light intensity of the two optical fibers connected by flipping as shown.

[0028] Figure 15 (a) indicates that, Figure 4 The graph shows the direction dependence of the transmitted light intensity of two typically connected optical fibers (including multi-core fibers with low refractive index markings surrounded by high refractive index regions). Figure 15 (b) means as Figure 8 The graph shows the direction dependence of the transmitted light intensity of the two optical fibers connected by flipping as shown.

[0029] Figure 16 (a) indicates that, Figure 4 The graph shows the direction dependence of the transmitted light intensity of the two optical fibers that are typically connected. Figure 16 (b) means as Figure 8 The graph shows the direction dependence of the transmitted light intensity of the two optical fibers connected by flipping as shown. Detailed Implementation

[0030] (Flowchart of fusion splicing method)

[0031] Reference Figure 1 and Figure 2 The flow of the fusion splicing method S1, which includes the inspection method S10 according to an embodiment of the present invention, will be described. The fusion splicing method S1 is a method of splicing two optical fibers OF1 and OF2, whose refractive index distribution in the fusion cross-section is anisotropic, using the fusion splicing device 1. The inspection method S10 is a method of checking whether proper rotational alignment has been performed. Figure 1 This is a flowchart illustrating the process of fusion splicing method S1. Figure 2 This is a perspective view showing the state of optical fibers OF1 and OF2 in each step of the fusion splicing method S1. Furthermore, in this embodiment, optical fibers OF1 and OF2 are envisioned as multi-core optical fibers having a cladding, multiple fiber cores formed inside the cladding, and a single marked fiber formed inside the cladding. Specific examples of optical fibers OF1 and OF2 will be described later with reference to the same drawing. Additionally, the fusion splicing method S1 can also be considered as a method for manufacturing an optical fiber connector obtained by fusion splicing optical fibers OF1 and OF2.

[0032] like Figure 1As shown, the welding method S1 includes a preparation step S11, a pre-welding measurement step S12, a self-aligning step S13, a butt welding step S14, a welding step S15, a post-welding measurement step S16, an inspection step S17, and an estimation step S18. The inspection method S10 consists of all these steps except for the butt welding step S14 and the welding step S15. Furthermore, in both the welding method S1 and the inspection method S10, the preparation step S11, the pre-welding measurement step S12, and the self-aligning step S13 are not essential and can be omitted.

[0033] The welding connection method S1, which includes the inspection method S10 of this embodiment, is implemented, for example, using the welding connection device 1, which includes the inspection system 10 of this embodiment. Figure 2 As shown, the welding connection device 1 includes a light source 11, a photodetector 12, a heating element 13, a self-aligning mechanism (not shown), and a control unit 15. The inspection system 10 is composed of structures other than the heating element 13. Furthermore, in Figure 2 In this example, only one combination of light source 11 and photodetector 12 is shown, but the fusion splicing device 1 can have two or more combinations of light source 11 and photodetector 12. Furthermore, in the following description, the axial direction of optical fibers OF1 and OF2 is defined as the z-axis direction, and the two directions orthogonal to the z-axis direction are defined as the x-axis direction and the y-axis direction. The x-axis direction and the y-axis direction are mutually orthogonal.

[0034] Light source 11 is a structure used to illuminate optical fibers OF1 and OF2. In this embodiment, an LED is used as light source 11. An LD (Light Diode) can also be used instead of an LED. Photodetector 12 is a structure used to detect the light transmitted through optical fibers OF1 and OF2. In this embodiment, a photodiode or photoconductor is used as photodetector 12. A camera can also be used instead of a photodiode or photoconductor as photodetector 12. Photodetector 12 is positioned in the optical path of the light illuminating and transmitting through optical fibers OF1 and OF2 from light source 11. Figure 2The example shown illustrates a configuration where the light source 11 and the photodetector 12 are positioned opposite each other across optical fibers OF1 and OF2, but this configuration is not limited to this. For example, if an optical element such as a mirror is placed between the light source 11 and the optical fibers OF1 and OF2, and / or between the photodetector 12 and the optical fibers OF1 and OF2 to bend the optical path, a configuration where the light source 11 and the photodetector 12 are not positioned opposite each other across optical fibers OF1 and OF2 may also exist. The heating element 13 is a structure used to heat the end faces of the optical fibers OF1 and OF2 that are being fused together. In this embodiment, an electrode pair consisting of two electrodes is used as the heating element 13. Alternatively, an electrode group consisting of three or more electrodes, or a laser device such as a CO2 laser, may be used instead of an electrode pair as the heating element 13. The alignment mechanism is a structure used to hold the optical fibers OF1 and OF2 and to allow the optical fibers OF1 and OF2 to translate and rotate independently, respectively. In this embodiment, an alignment mechanism including a holding member, a translation mechanism, and a rotation mechanism is used as the alignment mechanism. The retaining component is detachable relative to the self-aligning mechanism, and therefore can be considered as a component independent of the self-aligning mechanism, the fusion splicing device 1, the inspection system 10, or the fusion splicing system or inspection system described later. The retaining component is used to hold the optical fibers OF1 and OF2, and has the function of clamping or fixing the ends of the optical fibers OF1 and OF2. In this embodiment, the retaining component may, for example, consist of a plate-shaped component with V-grooves for receiving the optical fibers OF1 and OF2, and a pressing component that fixes the optical fibers OF1 and OF2 received in the V-grooves to the plate-shaped component by pressing them. The translation mechanism is a mechanism for independently moving the optical fibers OF1 and OF2 held by the retaining component in the x-axis, y-axis, and z-axis directions, respectively, when the fixing performed by the pressing component is invalidated. The rotation mechanism is a mechanism for independently rotating the optical fibers OF1 and OF2 held by the retaining component about the z-axis, respectively, when the fixing performed by the pressing component is invalidated. When the alignment performed by the translation and rotation mechanisms is completed, the pressing component activates the fixation, and optical fibers OF1 and OF2 are fixed to the holding component. This holding component, which is a necessary structure for directly transferring the aligned optical fibers OF1 and OF2 to other devices while maintaining their current state, can be omitted. Alternatively, other holding components can be used, either in the activated state during alignment or as a substitute, and in the deactivated state after alignment. In this case, the translation mechanism moves optical fibers OF1 and OF2, along with the other holding components, parallel to each other in the z-axis, y-axis, and z-axis directions. The rotation mechanism rotates optical fibers OF1 and OF2, along with the other holding components, about the z-axis.The control unit 15 is a structure used to implement the various steps included in the welding connection method S1 by controlling the light source 11, the photodetector 12, the heating unit 13, and the self-aligning mechanism. In this embodiment, a microcontroller is used as the control unit 15. Alternatively, an integrated circuit such as an IC (Integrated Circuit), an LSI (Large-scale Integrated Circuit), or an ASIC (Application Specific Integrated Circuit), or a NC (Numerical Control) device may be used as the control unit 15 instead of a microcontroller. A machine learning device may also be used as the NC device.

[0035] Furthermore, the aforementioned light source 11 can be configured as a single light source or multiple light sources, the aforementioned photodetector 12 can be configured as a single photodetector or multiple photodetectors, the aforementioned heating unit 13 can be configured as a single heating unit or multiple heating units, the aforementioned alignment mechanism can be configured as a single alignment mechanism or multiple alignment mechanisms, and the aforementioned control unit 15 can be configured as a single control unit or multiple control units. In this case, at least one of the aforementioned single control units or multiple control units uses a single light source or at least one of the aforementioned multiple light sources and a single photodetector or at least one of the aforementioned multiple photodetectors to perform the pre-welding measurement step S12 or the post-welding measurement step S16. In addition, at least one of the aforementioned single control units or multiple control units uses a single alignment mechanism or at least one of the aforementioned multiple alignment mechanisms to perform the alignment step S13 or the docking step S14. In addition, at least one of the aforementioned single control units or multiple control units uses a single heating unit or at least one of the aforementioned multiple heating units to perform the welding step S15. In addition, the aforementioned single control unit or at least one of the multiple control units performs the determination process S17 or the estimation process S18.

[0036] Preparation step S11 is the process in which the user places optical fibers OF1 and OF2 onto the fusion splice device 1. Optical fibers OF1 and OF2 are held parallel to their central axis and z-axis by the centering mechanism of the fusion splice device 1. The state of optical fibers OF1 and OF2 after preparation step S11 is shown below. Figure 2(a). Further, in the preparation process S11, cleaning discharge may also be performed. Cleaning discharge is a process of cleaning the surfaces of the optical fibers OF1 and OF2 by blowing off or melting foreign matters such as glass chips adhering to the surfaces of the optical fibers OF1 and OF2 to make them disappear. When performing cleaning discharge, it is preferable to clean the surfaces of the parts of the optical fibers OF1 and OF2 that will be the measurement objects in the pre-welding measurement process S12 described below. A confirmation operation of using the light source 11 and the optical detector 12 to confirm whether the surfaces of the optical fibers OF1 and OF2 are cleaned may also be further performed. In addition, the cleaning discharge and the confirmation operation may be repeatedly performed until it is confirmed that the surfaces of the optical fibers OF1 and OF2 are cleaned.

[0037] Thus, the operation subject of the preparation process S11 may be an operator or a device. In addition, the device may be a mechanism assembled in the welding connection device 1 (a part of the welding connection device 1) or a mechanism separated from the welding connection device 1 (such as a robot).

[0038] When the preparation process S11 is completed, the pre-welding measurement process S12 is performed. The pre-welding measurement process S12 is a process in which the welding connection device 1 measures the central position or the outer peripheral position, and the core position or the mark position of the optical fibers OF1 and OF2 before welding. In addition, the measurement of the central position or the outer peripheral position of the optical fibers OF1 and OF2 may be omitted if not necessary. In the pre-welding measurement process S12, the control unit of the welding connection device 1 uses the alignment mechanism of the welding connection device 1 to move the optical fiber OF1 in the negative z-axis direction. Thereby, the end of the optical fiber OF1 is positioned between the light source 11 and the optical detector 12. In addition, the control unit of the welding connection device 1 uses the alignment mechanism of the welding connection device 1 to move the optical fiber OF2 in the positive z-axis direction. Thereby, the end of the optical fiber OF2 is positioned between the light source 11 and the optical detector 12. As a result, the interval d between the end surfaces of the optical fiber OF1 and the optical fiber OF2 is small enough. The interval d only needs to be small enough to perform the detection process described below, for example, 0 < d ≤ 200 μm. The interval d may also be greater than 200 μm as long as the detection process described below can be performed. In the present embodiment, the interval d is set to 50 μm. In addition, the above-mentioned holding members, such as optical fiber brackets, may be pre-installed at the ends of the optical fibers OF1 and OF2. When the optical fibers OF1 and OF2 include marks, the optical fiber brackets are installed on the optical fibers OF1 and OF2 such that the position of the reference surface of the optical fiber bracket and the position of the mark of the optical fiber satisfy a specific relationship.

[0039] Then, the control unit of the fusion splicing device 1 uses the light source 11 and the photodetector 12 to measure the directional dependence of (1) the intensity I1 (hereinafter referred to as transmitted light intensity I1) of light emitted from the light source 11 and incident on the end of the fiber OF1 via the side of the fiber OF1, transmitted through the end of the fiber OF1 and emitted from the end of the fiber OF1 via the side of the fiber OF1, and (2) the intensity I2 (hereinafter referred to as transmitted light intensity I2) of light emitted from the light source 11 and incident on the end of the fiber OF2 via the side of the fiber OF2, transmitted through the end of the fiber OF2 and emitted from the end of the fiber OF2 via the side of the fiber OF2. When using a photodiode or a photoconductor as the photodetector 12, the control unit of the fusion splicing device 1 repeatedly performs the detection processing of transmitted light intensity I1 and I2 while rotating the fiber OF1 and OF2 about the z-axis, or rotating the light source 11 and the photodetector 12 about the z-axis. Thus, the control unit of the fusion splicing device 1 obtains data representing the directional dependence of the transmitted light intensity I1 of optical fiber OF1 and the directional dependence of the transmitted light intensity I2 of optical fiber OF2. Here, the data obtained through each detection process is, for example, a brightness value representing the intensity of light detected by a photodiode or photoconductor. In this case, the data representing the directional dependence of the transmitted light intensity I1 and I2 obtained by repeatedly performing the detection process becomes a one-dimensional arrangement of brightness values ​​representing the intensity of light detected by a photodiode or photoconductor. On the other hand, when using a camera as the photodetector 12, the control unit of the fusion splicing device 1 repeatedly performs image processing to capture images of the ends of optical fibers OF1 and OF2, and calculation processing (e.g., cumulative processing, average processing, or weighted average processing) to derive the transmitted light intensity I1 and I2 of optical fibers OF1 and OF2 from the images obtained through the image processing. Therefore, the control unit of the fusion splicing device 1 obtains data representing the directional dependence of the transmitted light intensity I1 of optical fiber OF1 and the directional dependence of the transmitted light intensity I2 of optical fiber OF2. Here, the data obtained through each imaging process is, for example, a two-dimensional arrangement (i.e., an image) of the brightness values ​​of the light intensity detected by each unit of the image sensor constituting the camera, and the data obtained through each arithmetic process is, for example, the cumulative value, average value, or weighted average value (hereinafter referred to as "cumulative value, etc.") of the intensity detected by each unit of the image sensor constituting the camera. In this case, the data representing the directional dependence of the transmitted light intensity I1 and I2 obtained by repeatedly performing imaging and arithmetic processes becomes a one-dimensional arrangement of the cumulative values, etc., of the intensity detected by each unit of the image sensor constituting the camera.Then, the control unit of the fusion splicing device 1 determines the center or peripheral position, and the core or mark position of the optical fiber OF1 based on the direction dependence of the transmitted light intensity I1 of the optical fiber OF1 (data representing the direction dependence). Similarly, the control unit of the fusion splicing device 1 determines the center or peripheral position, and the core or mark position of the optical fiber OF2 based on the direction dependence of the transmitted light intensity I2 of the optical fiber OF2 (data representing the direction dependence). The states of the optical fibers OF1 and OF2 during the pre-fusion splicing measurement step S12 are shown below. Figure 2 (b)

[0040] Furthermore, in the pre-fusion splicing measurement step S12, the direction of optical measurement (the aforementioned detection processing or imaging processing) can be distributed within a range of 360° or within a range less than 360°. In other words, the domain of the direction dependence of the transmitted light intensities I1 and I2 of optical fibers OF1 and OF2 (equivalent to the range of the horizontal axis when represented by a graph) can be 360° or less than 360°. When the range of the direction during optical measurement is less than 360°, in order to determine the mark position in the pre-fusion splicing measurement step S12 by optical measurement from directions within this range, in the preparation step S11, preferably, (1) after setting optical fibers OF1 and OF2 in the alignment mechanism of the fusion splicing device 1, coarse rotation alignment of optical fibers OF1 and OF2 is performed, or (2) after coarse rotation alignment of optical fibers OF1 and OF2 is performed, optical fibers OF1 and OF2 are set in the alignment mechanism of the fusion splicing device 1. In the former case, the alignment mechanism of the fusion splicing device 1 performs coarse rotation alignment. In the latter case, the operator or a device other than the fusion splicing connection device 1 performs coarse rotation alignment. In any case, the time required to determine the marking positions of optical fibers OF1 and OF2 can be shortened in the pre-fusion splicing measurement step S12.

[0041] When the pre-fusion splicing measurement step S12 is completed, the alignment step S13 is performed. The alignment step S13 is the process by which the fusion splicing device 1 aligns with the optical fibers OF1 and OF2. In the alignment step S13, the control unit of the fusion splicing device 1 uses the alignment mechanism of the fusion splicing device 1 to move the optical fibers OF1 and OF2 in the x-axis direction and / or y-axis direction, respectively, so that the center position or outer periphery position of the optical fibers OF1 and OF2 determined in the pre-fusion splicing measurement step S12 is consistent. Furthermore, the control unit of the fusion splicing device 1 uses the alignment mechanism of the fusion splicing device 1 to rotate the optical fibers OF1 and OF2 about the z-axis, respectively, so that the core positions of the optical fibers OF1 and OF2 determined in the pre-fusion splicing measurement step S12 are consistent, or that the marked positions of the optical fibers OF1 and OF2 determined in the pre-fusion splicing measurement step S12 satisfy a predetermined relationship. The order in which movement is performed along the x-axis and / or y-axis, and rotation about the z-axis, is arbitrary. Movement along the x-axis and / or y-axis can be performed before rotation about the z-axis, or vice versa. Figure 2 (c) indicates the state of optical fibers OF1 and OF2 during the alignment process S13.

[0042] Furthermore, in this embodiment, a structure is adopted in which a self-aligning process S13 is performed after a pre-welding measurement process S12, but the present invention is not limited to this. For example, a structure can also be adopted in which the self-aligning operation is advanced in stages by alternately and repeatedly performing the pre-welding measurement process S12 and the self-aligning process S13.

[0043] When the alignment process S13 is completed, the docking process S14 is performed. The docking process S14 is the process by which the end face of fiber OF1 is aligned with the end face of fiber OF2 using the fusion splicing device 1. In the docking process S14, the control unit of the fusion splicing device 1 uses the alignment mechanism of the fusion splicing device 1 to move fiber OF1 in the negative z-axis direction by d / 2 (approximately 5 μm in this embodiment). Additionally, the control unit of the fusion splicing device 1 uses the alignment mechanism of the fusion splicing device 1 to move fiber OF2 in the positive z-axis direction by d / 2 (approximately 5 μm in this embodiment). The states of fiber OF1 and OF2 after the docking process S14 are shown below. Figure 2In (d). Further, in the docking process S14, pre-discharge (Japanese: 前放電) can also be carried out. Pre-discharge is a process for softening the front ends of the optical fibers OF1 and OF2. By docking the front ends of the optical fibers OF1 and OF2 on the basis of carrying out pre-discharge, the front ends of the optical fibers OF1 and OF2 can be reliably adhered. In this case, it is preferable to set the movement amount of the optical fibers OF1 and OF2 to d / 2 + ε. ε is an additional movement amount for overlapping the front ends of the optical fibers OF1 and OF2, for example, 10 μm. Thereby, the front ends of the optical fibers OF1 and OF2 can be more reliably adhered.

[0044] When the docking process S14 is completed, a fusion splicing process S15 is carried out. The fusion splicing process S15 is a process in which the fusion splicing device 1 fuses the optical fiber OF1 and the optical fiber OF2. In the fusion splicing process S15, the control unit of the fusion splicing device 1 uses the heating unit 13 (for example, generates arc discharge using an electrode pair) to heat and melt the ends of the optical fiber OF1 and the optical fiber OF2. When the ends of the heated and melted optical fiber OF1 and optical fiber OF2 are solidified by natural cooling, the optical fiber OF1 and the optical fiber OF2 are fused. The state of the optical fibers OF1 and OF2 after carrying out the fusion splicing process S15 is shown in Figure 2 of (e).

[0045] Hereinafter, the part in the optical fibers OF1 and OF2 where the refractive index distribution changes due to heating in the fusion splicing process S15 is called the "heating affected part". In Figure 2 of (e), the heating affected part is indicated by shading. The heating affected part extends about 0.3 mm or more and 2 mm or less in the positive z-axis direction and the negative z-axis direction from the center of the heating unit 13 (in this embodiment, the electrode pair).

[0046] When the fusion splicing process S15 is completed, the post-fusion measurement process S16 is performed. The post-fusion measurement process S16 is a process in which the fusion splicing device 1 measures the core position or mark position of the fused optical fibers OF1 and OF2. In the post-fusion measurement process S16, the control unit of the fusion splicing device 1 measures the directional dependence of the transmitted light intensity I1 of optical fiber OF1 and the transmitted light intensity I2 of optical fiber OF2. When using a photodiode or photoconductor as the photodetector 12, the control unit of the fusion splicing device 1 repeatedly performs the detection processing of the transmitted light intensity I1 and I2 while rotating optical fibers OF1 and OF2 about the z-axis, or while rotating the light source 11 and the photodetector 12 about the z-axis. Thus, the control unit of the fusion splicing device 1 obtains data representing the directional dependence of the transmitted light intensity I1 of optical fiber OF1 and the directional dependence of the transmitted light intensity I2 of optical fiber OF2. In this case, the data representing the direction dependence of the transmitted light intensity I1 and I2, for example, is a one-dimensional arrangement of brightness values ​​representing the intensity of light detected by the photodiode or photoconductor, similar to the pre-fusion splicing measurement process S12. On the other hand, when using a camera as the photodetector 12, the control unit of the fusion splicing device 1 repeatedly performs image processing (capturing images of the ends of the optical fibers OF1 and OF2) and calculation processing (deriving the transmitted light intensity I1 and I2 of the optical fibers OF1 and OF2 from the images obtained through this image processing) while rotating the optical fibers OF1 and OF2 about the z-axis, or rotating the light source 11 and the photodetector 12 about the z-axis. Thus, the control unit of the fusion splicing device 1 obtains data representing the direction dependence of the transmitted light intensity I1 of the optical fiber OF1 and the direction dependence of the transmitted light intensity I2 of the optical fiber OF2. In this case, the data representing the direction dependence of the transmitted light intensity I1 and I2 obtained through repeated image processing and calculation processing is, for example, a one-dimensional arrangement of the cumulative values ​​of the intensity detected by each unit of the image sensor constituting the camera, similar to the pre-fusion splicing measurement process S12. Then, the control unit of the fusion splicing device 1 determines the core position or mark position of the optical fiber OF1 based on the direction dependence of the transmitted light intensity I1 of the optical fiber OF1 (data representing the direction dependence). Additionally, the control unit of the fusion splicing device 1 determines the core position or mark position of the optical fiber OF2 based on the direction dependence of the transmitted light intensity I2 of the optical fiber OF2 (data representing the direction dependence).

[0047] Furthermore, in the post-fusion splicing measurement step S16, the transmitted light intensities I1 and I2 of the heated portions of optical fibers OF1 and OF2 can be measured, as well as the transmitted light intensities I1 and I2 of the unheated portions of optical fibers OF1 and OF2. The state of optical fibers OF1 and OF2 in the post-fusion splicing measurement step S16, where the former is performed, is shown below. Figure 2(f) shows the status of optical fibers OF1 and OF2 in the post-fusion splicing measurement process S16 of the latter. Figure 2 (g) and (h). In the post-fusion splicing measurement step S16, the transmitted light intensities I1 and I2 of the heated areas of optical fibers OF1 and OF2, as well as the transmitted light intensities I1 and I2 of the unheated areas of optical fibers OF1 and OF2, can both be measured. Furthermore, in the post-fusion splicing measurement step S16, the transmitted light intensities I1 and I2 of the ends of optical fibers OF1 and OF2 can be measured, as well as the transmitted light intensities I1 and I2 of areas other than the ends of optical fibers OF1 and OF2. However, if the fiber core is helical, the core position may change significantly depending on the measurement location; or if the marking is helical, the marking position may change significantly depending on the measurement location. Therefore, it is preferable to measure the transmitted light intensities I1 and I2 of the ends of optical fibers OF1 and OF2. Alternatively, a visual inspection can be performed after the fusion splicing step S15 and before starting the post-fusion splicing measurement step S16. Visual inspection is a process that determines whether the welding is successful based on the presence of bubbles, foreign objects, and the positional offset of the cladding.

[0048] In implementation Figure 2 In the case of the post-fusion splicing measurement process S16 shown in (g) and (h), the control unit (process 1) of the fusion splicing device 1 uses the alignment mechanism to move the optical fibers OF1 and OF2 in the negative z-axis direction, and (process 2) uses the light source 11 and the photodetector 12 as shown in (g) and (h) respectively. Figure 2 As shown in (g), the transmitted light intensity I1 of fiber OF1 is detected. (Process 3) Fiber OF1 and OF2 are moved in the positive z-axis direction using a centering mechanism. (Process 4) Light source 11 and photodetector 12 are used as shown in (g). Figure 2 The transmitted light intensity I1 of optical fiber OF1 is detected as shown in (h). Here, the movement amount of optical fibers OF1 and OF2 in process 1 is preferably 0.3 mm or more, more preferably 0.5 mm or more. In addition, the movement amount of optical fibers OF1 and OF2 in process 3 is preferably twice the movement amount of optical fibers OF1 and OF2 in process 1. When a camera capable of simultaneously including the heated affected portion and the non-heated affected portions on both sides of the heated affected portion of optical fibers OF1 and OF2 in the field of view is used as the photodetector 12, processes 1 and 3 can be omitted, and processes 2 and 3 (simultaneously measuring the transmitted light intensity I1 of optical fiber OF1 and the transmitted light intensity I2 of optical fiber OF2) can be performed simultaneously.

[0049] When the post-fusion splicing measurement step S16 is completed, the judgment step S17 is performed. Judgment step S17 determines whether the fusion splicing device 1 has correctly spliced ​​optical fibers OF1 and OF2. In judgment step S17, the control unit of the fusion splicing device 1 determines whether the core positions of optical fibers OF1 and OF2, as determined in the post-fusion splicing measurement step S16, are consistent, or whether the marking positions of optical fibers OF1 and OF2, as determined in the post-fusion splicing measurement step S16, meet a predetermined relationship. Here, the judgment result indicating successful splicing is when the core positions of optical fibers OF1 and OF2 are consistent and the marking positions of optical fibers OF1 and OF2 meet the predetermined relationship. On the other hand, the judgment result indicating failed splicing is when the core positions of optical fibers OF1 and OF2 are inconsistent, or the marking positions of optical fibers OF1 and OF2 do not meet the predetermined relationship. This judgment result may or may not be notified to the user. When the judgment result is notified to the user, the method of notification is not particularly limited. For example, when the core positions of optical fibers OF1 and OF2 are inconsistent, or when the marking positions of optical fibers OF1 and OF2 do not meet the predetermined relationship, methods such as turning on a light, sounding a buzzer, outputting image messages from a display, or outputting sound messages from a speaker can be given.

[0050] Furthermore, it is also possible to determine whether the core positions of optical fibers OF1 and OF2 are consistent by checking whether the overlap between the peak corresponding to the fiber core in the curve representing the direction dependence of transmitted light intensity I1 and the peak corresponding to the fiber core in the curve representing the direction dependence of transmitted light intensity I2 is above a predetermined threshold. Additionally, it is also possible to determine whether the marking positions of optical fibers OF1 and OF2 are consistent by checking whether the overlap between the peak corresponding to the mark in the curve representing the direction dependence of transmitted light intensity I1 and the peak corresponding to the mark in the curve representing the direction dependence of transmitted light intensity I2 is above a predetermined threshold.

[0051] Furthermore, it is also possible to determine whether the core positions of optical fibers OF1 and OF2 are consistent by checking whether the difference between the direction (angle) of the peak corresponding to the fiber core in the curve representing the direction dependence of transmitted light intensity I1 and the direction (angle) of the peak corresponding to the fiber core in the curve representing the direction dependence of transmitted light intensity I2 is within a predetermined range. Additionally, it is also possible to determine whether the mark positions of optical fibers OF1 and OF2 satisfy a predetermined relationship by checking whether the difference between the direction (angle) of the peak corresponding to the mark in the curve representing the direction dependence of transmitted light intensity I1 and the direction (angle) of the peak corresponding to the mark in the curve representing the direction dependence of transmitted light intensity I2 is within a predetermined range.

[0052] When the judgment step S17 is completed, the estimation step S18 is performed. The estimation step S18 is the step of estimating the coupling efficiency or connection loss of optical fibers OF1 and OF2. In the estimation step S18, the control unit of the fusion splicing device 1 estimates the coupling efficiency or connection loss of optical fibers OF1 and OF2 based on the core positions of optical fibers OF1 and OF2 determined in the post-fusion measurement step S16. Furthermore, the control unit of the fusion splicing device 1 may or may not notify the user of the estimation result obtained in the estimation step S18. When the estimation result is notified to the user, the method of notification is not particularly limited. For example, the following methods can be used: lighting up a light or sounding a buzzer when the estimated coupling efficiency is lower than a predetermined threshold, or when the estimated connection loss exceeds a predetermined threshold; outputting the estimated coupling efficiency or connection loss as an image from a display; or outputting the estimated coupling efficiency or connection loss as sound from a speaker. By notifying users of the estimated results, it is possible to inform users of the coupling efficiency or connection loss of optical fibers OF1 and OF2.

[0053] Furthermore, the core number is an identification number assigned to each core of a multi-core optical fiber, for example, based on its distance from a marker. As an example, when multiple cores are arranged on a circumference, the core number of each core can be set as follows: First, the core number of the core closest to the marker is set to "1". Next, the core number of the second closest core to the marker is set to "2". Then, when tracing the circumference in sequence, passing the core closest to the marker and the second closest core to the marker, the core number of the third core passed is set to "3", the core number of the fourth core passed is set to "4", ..., and the core number of the nth core passed is set to "n". Alternatively, instead of referencing the marker, the core number can be set by referring to markings (e.g., symbols, text, etc.) formed on the surface of the cladding. Furthermore, when the cladding is covered by a cover layer, the core number can also be set by referring to markings formed on the surface of the cover layer. Furthermore, when connectors are installed at the ends of the multi-core optical fiber, the fiber core structure can be set by referring to the keys (e.g., protrusions) formed on the connector. Additionally, for example, when a flat portion is provided on the side of the cladding to make the cross-sectional shape of the cladding anisotropic (e.g., D-shaped), the fiber core number can be set by referring to this flat portion. Furthermore, when a cutout is provided on the side of the cladding, the iron fiber core number can be set by referring to this cutout. Additionally, when the multi-core optical fiber is connected to a transceiver, the fiber core number of each fiber can be set by referring to the port number of the transceiver connected to that fiber core.

[0054] Furthermore, in the estimation step S18, at least one of the following estimations can be made based on, or instead of, the estimation of the coupling efficiency or connection loss of optical fibers OF1 and OF2 (hereinafter also referred to as "first estimation"). That is, the correspondence between the core number of each core of optical fiber OF1 and the core number of the core of optical fiber OF2 optically coupled to that core can be estimated based on the core position and marking position of optical fiber OF1 determined in the post-fusion splicing measurement step S16. This estimation will also be referred to as "second estimation". In addition, based on the marking position of optical fiber OF1 determined in the post-fusion splicing measurement step S16, it can be estimated which region among the multiple regions obtained by splitting the cladding of optical fiber OF1 contains the marking of optical fiber OF1 (hereinafter also referred to as "third estimation"). Additionally, based on the marking position of fiber OF2 determined in the post-fusion splicing measurement step S16, it can be estimated which of the multiple regions obtained by splitting the cladding of fiber OF2 contains the marking of fiber OF2. These estimations will be referred to as "third estimations" below. Furthermore, based on the marking positions of fiber OF1 and OF2 determined in the post-fusion splicing measurement step S16, it can be estimated whether one or both of the overlap and offset between the markings of fiber OF1 and fiber OF2 are present. This estimation will also be referred to as "fourth estimation" below. Here, the overlap of the markings can be, for example, the area of ​​the region where the markings of fiber OF1 and fiber OF2 overlap, or the ratio of the area of ​​that region to the area of ​​the markings of fiber OF1 or fiber OF2. Furthermore, the offset of the markings can be, for example, the difference (distance) between the marking positions related to the radial and / or circumferential directions of the cladding. Alternatively, the angle (difference) between the direction (angle) of the mark on fiber OF1 observed from the center of the cladding and the direction (angle) of the mark on fiber OF2 observed from the center of the cladding can be considered as the mark offset. Furthermore, based on the fiber core positions of fiber OF1 and OF2 determined in the post-fusion splicing measurement step S16, one or both of the overlap and offset of each fiber core of fiber OF1 and the fiber core of fiber OF2 optically coupled to that fiber core can be estimated. This estimation will also be referred to as the "fifth estimation." Here, the overlap of the fiber cores can be, for example, the area of ​​the overlapping region between the fiber cores of fiber OF1 and fiber cores of fiber OF2, or the ratio of the area of ​​that region to the area of ​​the fiber cores of fiber OF1 or fiber OF2. The offset of the fiber cores can be, for example, the difference (distance) between the fiber core positions related to the radial and / or circumferential directions of the cladding. Alternatively, the angle (difference) between the direction (angle) of the fiber core of optical fiber OF1 observed from the center of the cladding and the direction (angle) of the fiber core of optical fiber OF2 connected to that fiber core observed from the center of the cladding can be regarded as the offset of the fiber core.Additionally, the polarity of optical fibers OF1 and OF2 (whether the end face of the fusion splice is end face σ1 or end face σ2, as described later) can be estimated based on the core positions and markings of optical fibers OF1 and OF2 determined in the post-fusion splicing measurement process S16. This estimation will also be referred to as the "sixth estimation" below. Furthermore, the control unit of the fusion splicing device 1 may or may not notify the user of these estimation results. When these estimation results are notified to the user, the method of notification is not particularly limited. For example, methods such as outputting these estimation results as an image from a display or as sound from a speaker can be used. By notifying the user of these estimation results, the user can become aware of these estimation results.

[0055] As described above, the inspection method S10 in this embodiment includes: a fusion splicing process S15, which splices optical fibers OF1 and OF2, whose cross-sections have anisotropic refractive index distributions; and a post-fusion measurement process S16, which, after performing the fusion splicing process S15, determines the core position or marking position of optical fiber OF1 based on the spatial distribution or direction dependence of the transmitted light intensity I1 of optical fiber OF1, and determines the core position or marking position of optical fiber OF2 based on the spatial distribution or direction dependence of the transmitted light intensity I2 of optical fiber OF2. Therefore, according to the inspection method S10 of this embodiment, it is possible to determine whether the fusion connection is successful based on the measurement results of the post-fusion measurement process S16. In addition, at least a portion of the foreign matter attached to the surfaces of optical fibers OF1 and OF2 before performing the fusion splicing process S15 can be eliminated by performing the fusion splicing process S15. As a result, the data obtained in the post-fusion measurement process S16 is less noisy than the data obtained in the pre-fusion measurement process S12, which is caused by foreign matter attached to the surfaces of optical fibers OF1 and OF2. Furthermore, in the post-fusion splicing measurement step S16, where optical fibers OF1 and OF2 have already been spliced, the pre-fusion splicing measurement step S12, where optical fibers OF1 and OF2 have not yet been spliced, is less prone to twisting. Therefore, the data obtained in the post-fusion splicing measurement step S16 contains less noise due to twisting of optical fibers OF1 and OF2 compared to the data obtained in the pre-fusion splicing measurement step S12. Thus, even if the core position or marker position cannot be accurately determined due to foreign objects in the pre-fusion splicing measurement step S12, the likelihood of accurately determining the core position and marker position in the post-fusion splicing measurement step S16 is high.

[0056] Furthermore, determining the success of a fusion splice after it has the following significance. Here, consider a method for manufacturing an optical fiber connector containing three optical fibers. This method consists of a first connection step of fusion splicing a first optical fiber to a second optical fiber and a second connection step of fusion splicing either the first or second optical fiber to a third optical fiber. If the fusion splicing method S1 of this embodiment is used in the first connection step, it is possible to know whether the fusion splicing of the first and second optical fibers is successful before performing the second connection step. Therefore, if the fusion splicing of the first and second optical fibers fails, it is possible to re-sponsor the first and second optical fibers before performing the second connection step. This avoids the need for the second connection step to be performed unnecessarily, thus enabling a manufacturing method that avoids waste. The same principle applies to a method for manufacturing an optical fiber connector containing four or more optical fibers.

[0057] Furthermore, the inspection method S10 of this embodiment includes a structure that further includes a determination step S17, which determines whether the fusion splicing is successful based on the fiber core positions or mark positions of optical fibers OF1 and OF2 determined in the post-fusion measurement step S16. Therefore, according to the fusion splicing method S1 of this embodiment, the success of the fusion splicing connection can be automatically determined. Thus, compared to the case where the user determines whether the fusion splicing connection is successful, it is easier for the user to know whether the fusion splicing connection is successful. In particular, when the user determines whether the fusion splicing connection is successful, there is a tendency for misjudgments to occur if the determination criteria are complex or changed; however, with automatic determination of the success of the fusion splicing connection, such misjudgments are less likely to occur.

[0058] Furthermore, in the inspection method S10 of this embodiment, the following structure is adopted: optical fibers OF1 and OF2 are marked optical fibers. In the determination step S17, if the mark positions of optical fibers OF1 and OF2 determined in the post-fusion splicing measurement step S16 meet a predetermined relationship, the fusion is determined to be successful; otherwise, if the mark positions of optical fibers OF1 and OF2 determined in the post-fusion splicing measurement step S16 do not meet the predetermined relationship, the fusion is determined to be unsuccessful. Therefore, according to the inspection method S10 of this embodiment, it is possible to automatically determine whether the fusion connection is successful in a suitable manner.

[0059] Furthermore, in the inspection method S10 of this embodiment, the following structure is adopted: in the pre-fusion splicing measurement step S12, the marking position of optical fiber OF1 is determined based on the spatial distribution or direction dependence of the transmitted light intensity I1 of optical fiber OF1, and the marking position of optical fiber OF2 is determined based on the direction dependence of the transmitted light intensity I2 of optical fiber OF2. Therefore, according to the inspection method S10 of this embodiment, the light source 11 and photodetector 12 used in the post-fusion splicing measurement step S16 can be used to perform the pre-fusion splicing measurement step S12 in the same way as the post-fusion splicing measurement step S16.

[0060] In addition, the inspection method S10 in this embodiment adopts the following structure: it also includes an estimation process, in which, based on one or both of the fiber core positions and marking positions of optical fibers OF1 and OF2 determined in the post-fusion measurement process S16, at least one of the following items (1) to (6) is estimated: (1) the coupling efficiency or connection loss of optical fibers OF1 and OF2, (2) the correspondence between the fiber core number of each fiber core of optical fiber OF1 and the fiber core number of optical fiber OF2 optically coupled to that fiber core, (3) (3) Which region among the multiple regions obtained by dividing the cladding of the optical fiber OF1 into multiple regions contains the mark of optical fiber OF1, and which region among the multiple regions obtained by dividing the cladding of optical fiber OF2 into multiple regions contains the mark of optical fiber OF2; (4) The amount of overlap or offset between the mark of optical fiber OF1 and the mark of optical fiber OF2; (5) The amount of overlap or offset between each core of optical fiber OF1 and the core of optical fiber OF2 optically coupled to that core; and (6) The polarity of optical fiber OF1 and OF2. Therefore, according to the inspection method S10 in this embodiment, various estimated values ​​can be automatically derived. Therefore, compared with the case where the user derives various estimated values, the user can easily know the various estimated values.

[0061] Furthermore, in this embodiment, the pre-fusion splicing measurement step S12 and the post-fusion splicing measurement step S16 employ a structure that uses the same light source 11 and the same photodetector 12 to measure the direction dependence of the transmitted light intensity I1 of optical fiber OF1 and the direction dependence of the transmitted light intensity I2 of optical fiber OF2. However, the present invention is not limited to this. For example, in the pre-fusion splicing measurement step S12 and the post-fusion splicing measurement step S16, a structure that uses a different light source and photodetector than those used to measure the direction dependence of the transmitted light intensity I1 of optical fiber OF1 can also be employed to measure the direction dependence of the transmitted light intensity I2 of optical fiber OF2.

[0062] Furthermore, in this embodiment, a structure is adopted in which the directional dependence of the transmitted light intensity I1 of optical fiber OF1 and the directional dependence of the transmitted light intensity I2 of optical fiber OF2 are measured simultaneously in the pre-fusion splicing measurement step S12 and the post-fusion splicing measurement step S16 (when the heated area is taken as the measurement object). However, the present invention is not limited to this. For example, the following structure may also be adopted: in the pre-fusion splicing measurement step S12 and the post-fusion splicing measurement step S16 (when the heated area is taken as the measurement object), after measuring the directional dependence of the transmitted light intensity I1 of optical fiber OF1, the directional dependence of the transmitted light intensity I1 of optical fiber OF2 is measured, or conversely, after measuring the directional dependence of the transmitted light intensity I2 of optical fiber OF2, the directional dependence of the transmitted light intensity I2 of optical fiber OF1 is measured.

[0063] Furthermore, in this embodiment, in the pre-fusion splicing measurement step S12 and the post-fusion splicing measurement step S16, a structure is used to measure the direction dependence of the transmitted light intensities I1 and I2 of optical fibers OF1 and OF2 by repeatedly performing detection processing (using a photodiode or photoconductor as the photodetector 12) or imaging processing (using a camera as the photodetector 12) while rotating optical fibers OF1 and OF2 about the z-axis, thereby measuring the direction dependence of the transmitted light intensities I1 and I2 of optical fibers OF1 and OF2 (also called "side-view scanning"). However, the present invention is not limited to this. For example, a structure can also be used (also called "side-view imaging") where a camera is used as the photodetector 12 to photograph the side of optical fibers OF1 and OF2 from a specific direction, thereby measuring the spatial distribution of the transmitted light intensities of optical fibers OF1 and OF2. In this case, instead of relying on data representing the directional dependence of the transmitted light intensities I1 and I2 of optical fibers OF1 and OF2, the control unit of the fusion splicing device 1 determines the core position or mark position of optical fibers OF1 and OF2 based on image data (a two-dimensional arrangement of brightness values) representing the spatial distribution of the transmitted light intensities I1 and I2 of optical fibers OF1 and OF2. Furthermore, in the pre-fusion splicing measurement step S12, as described above, in addition to determining the core position or mark position, the center position or peripheral position can also be determined; however, if not necessary, the determination of the center position and peripheral position can be omitted.

[0064] Furthermore, in the pre-fusion splicing measurement process S12, a structure can be adopted to determine the core position or mark position of optical fibers OF1 and OF2 by end-view shooting instead of side-view scanning or side-view shooting. Here, end-view shooting refers to the method of determining the core position or mark position of optical fibers OF1 and OF2 by using a camera as a photodetector 12 and obtaining an image by shooting the end face of the optical fiber from a specific direction. When the center position or peripheral position of optical fibers OF1 and OF2, as well as the core position or mark position, are determined by end-view shooting, the control unit of the fusion splicing device 1 in the pre-fusion splicing measurement process S12 (1) moves the photodetector 12 between optical fibers OF1 and OF2, (2) shoots the end face of optical fiber OF1 with the photodetector 12 facing the end face of optical fiber OF1, (3) reshoots the end face of optical fiber OF2 with the photodetector 12 facing the end face of optical fiber OF2, and (4) moves the photodetector 12 away from between optical fibers OF1 and OF2. Alternatively, (1) insert a mirror between optical fibers OF1 and OF2 with the reflective surface of the mirror at a 45-degree angle to the optical axis of optical fiber OF1 and facing the end face of optical fiber OF1; (2) use photodetector 12 to photograph the end face of optical fiber OF1 reflected on the mirror; (3) change the orientation of the mirror with the reflective surface of the mirror at a 45-degree angle to the optical axis of optical fiber OF2 and facing the end face of optical fiber OF2; (4) use photodetector 12 to photograph the end face of optical fiber OF2 reflected on the mirror; and (5) retract the mirror from between optical fibers OF1 and OF2. Furthermore, in the pre-fusion splicing measurement step S12, as described above, in addition to determining the core position or the mark position, the center position or the peripheral position can also be determined, but if not necessary, the determination of the center position and the peripheral position can be omitted.

[0065] In side-view scanning or side-view imaging, it has the advantage of shortening the time required for the pre-fusion splicing measurement step S12 and the post-fusion splicing measurement step S16. On the other hand, in end-view imaging, it has the advantage of being able to determine the center position or peripheral position, or core position or marking position of optical fibers OF1 and OF2 with high precision in the pre-fusion splicing measurement step S12.

[0066] Furthermore, this embodiment employs a structure that determines whether the fusion splice connection is successful by performing a determination step S17, but it is not limited to this. For example, instead of performing the determination step S17, other determination processes for determining whether the fusion splice connection is successful may be performed in the estimation step S18 based on the estimation result. Additionally, if the estimation result is notified to the user in the estimation step S18, the user can determine whether the fusion splice connection is successful based on the estimation result. Alternatively, if the estimation result is notified to other devices in the estimation step S18, other devices can also determine whether the fusion splice connection is successful based on the estimation result. For example, if the first estimation is performed in the estimation step S18, if the connection loss of optical fibers OF1 and OF2 is below a predetermined first threshold, or if the coupling efficiency of optical fibers OF1 and OF2 is above a predetermined second threshold, the fusion splice connection can be determined to be successful. If the connection loss of optical fibers OF1 and OF2 exceeds the first threshold, or if the coupling efficiency of optical fibers OF1 and OF2 is less than the predetermined second threshold, the fusion splice connection can be determined to be unsuccessful. In this situation, the fusion splicing device 1 can determine whether the fusion connection is successful based on the value of coupling efficiency or connection loss. Furthermore, the fusion splicing device 1 can determine whether the fusion connection is successful without actually measuring the value of coupling efficiency or connection loss. Additionally, if the second estimation described above is performed in the estimation step S18, and the correspondence between the fiber core numbers of optical fibers OF1 and OF2 matches the predetermined correspondence, the fusion connection can be determined to be successful; if the correspondence between the fiber core numbers of optical fibers OF1 and OF2 does not match the predetermined correspondence, the fusion connection can be determined to be unsuccessful. In this situation, the fusion splicing device 1 can determine whether the fusion connection is successful based on the correspondence between the fiber core numbers. Furthermore, the fusion splicing device 1 can determine whether the fusion connection is successful without actually measuring the value of coupling efficiency or connection loss. Furthermore, if the third estimation is performed in estimation step S18, the fusion splice is considered successful if the marked areas in optical fibers OF1 and OF2 are consistent, and it is considered a failed fusion splice if the marked areas in optical fibers OF1 and OF2 are inconsistent. In this case, the fusion splicing device 1 can determine whether the fusion splice is successful based on the marked areas. Additionally, the fusion splicing device 1 can determine whether the fusion splice is successful without actually measuring the coupling efficiency or connection loss. Furthermore, if the fourth estimation is performed in estimation step S18, the fusion splice is considered successful if the overlap of the marks in optical fibers OF1 and OF2 is above a predetermined threshold, and it is considered a failed fusion splice if the overlap of the marks is below the predetermined threshold.Alternatively, if the offset of each mark in optical fibers OF1 and OF2 is below a predetermined threshold, the fusion splice can be determined to be successful; if the offset of each mark exceeds the predetermined threshold, the fusion splice can be determined to be unsuccessful. In this case, the fusion splicing device 1 can determine whether the fusion splice is successful based on the overlap and offset of each mark. Furthermore, the fusion splicing device 1 can determine whether the fusion splice is successful without actually measuring the coupling efficiency or connection loss. Additionally, if the fifth estimation described above is performed in estimation step S18, if the overlap of each fiber core in optical fibers OF1 and OF2 is above the predetermined threshold, the fusion splice can be determined to be successful; if the overlap of the fiber cores is less than the predetermined threshold, the fusion splice can be determined to be unsuccessful. Alternatively, if the offset of each fiber core in optical fibers OF1 and OF2 is below the predetermined threshold, the fusion splice can be determined to be successful; if the offset of the fiber cores exceeds the predetermined threshold, the fusion splice can be determined to be unsuccessful. In this situation, the fusion splicing device 1 can determine whether the fusion connection is successful based on the overlap and offset of the fiber cores. Furthermore, the fusion splicing device 1 can determine whether the fusion connection is successful without actually measuring the coupling efficiency or connection loss. Additionally, if the sixth estimation is performed in the estimation step S18, the fusion connection is considered successful if the polarity of optical fibers OF1 and OF2 is the predetermined polarity, and considered unsuccessful if the polarity of optical fibers OF1 and OF2 is not the predetermined polarity. In this case, the fusion splicing device 1 can determine whether the fusion connection is successful based on the polarity of optical fibers OF1 and OF2. Furthermore, the fusion splicing device 1 can determine whether the fusion connection is successful without actually measuring the coupling efficiency or connection loss. Moreover, if the estimation result is notified to the user in the estimation step S18, the determination step S17 can be omitted. Conversely, if the determination step S17 is performed, the estimation step S18 can also be omitted. In either case, the user can know whether the fusion connection is successful.

[0067] Furthermore, in this embodiment, multi-core optical fibers with markings are envisioned as optical fibers OF1 and OF2, serving as the measurement target in the post-fusion splicing measurement step S16 (the "specific structure" in the claims), utilizing both the fiber core and the markings, but this is not a limitation. For example, multi-core optical fibers with a flat portion provided on the side of the cladding in a D-shaped cladding cross-section are envisioned as optical fibers OF1 and OF2, serving as the measurement target in the post-fusion splicing measurement step S16 (the "specific structure" in the claims), also utilizing both the fiber core and the flat portion. Multi-core optical fibers with cutouts in the cladding are envisioned as optical fibers OF1 and OF2, serving as the measurement target in the post-fusion splicing measurement step S16 (the "specific structure" in the claims), also utilizing both the fiber core and the cutouts. In these cases, the markings can be omitted. Additionally, optical fibers other than multi-core optical fibers, such as PANDA optical fibers with stress-inducing portions or photonic crystal fibers with fine structures, can also be the objects of inspection according to this invention. In PANDA optical fibers, the stress-inducing portion can be a specific structure replacing the markings. Furthermore, in photonic crystal fibers, microstructures can serve as specific constructions that replace markings. In this case, the aforementioned effect remains unchanged. Alternatively, it can be stated that an anisotropic refractive index distribution in the cross-section is a fiber whose refractive index distribution in the cross-section lacks rotational symmetry.

[0068] (Specific examples of optical fibers)

[0069] Reference Figure 3 Specific examples of optical fibers OF1 and OF2 will be provided. In this specific example, optical fibers OF1 and OF2 are multi-core optical fibers (MF). Figure 3 In the image, (a) is a side view of the multi-core fiber MF, (b) is a front view of one end face σ1 of the multi-core fiber MF viewed from the direction of line of sight E1, and (c) is a front view of the other end face σ2 of the multi-core fiber MF viewed from the direction of line of sight E2.

[0070] A multi-core optical fiber (MF) has n cores (n is a natural number greater than or equal to 2) a1 to an and a cladding b. Cladding b is a cylindrical component. Cladding b is, for example, made of quartz glass. Each core ai (i is a natural number greater than or equal to 1 and less than n) is a cylindrical region located inside cladding b, with a higher refractive index than cladding b, extending in the same direction as cladding b. Each core ai is, for example, made of quartz glass with added ascending dopants such as germanium. Furthermore, cladding b only needs to be cylindrical; its cross-sectional shape is arbitrary. The cross-sectional shape of cladding b can be, for example, a quadrilateral, a hexagon, or a polygon, or a barrel shape.

[0071] In end faces σ1 and σ2, fiber cores a1~an are symmetrically arranged with respect to axis L1, which is orthogonal to the central axis L0 of the multi-core fiber MF. Furthermore, in end faces σ1 and σ2, fiber cores a1~an are arranged to avoid axis L1. In other words, in end faces σ1 and σ2, fiber cores a1~an are located outside of axis L1.

[0072] Multi-core optical fibers (MF) also possess a marker c. Marker c is a columnar region located inside the cladding b, with a different refractive index than cladding b, extending in the same direction as cladding b. The cross-sectional shape of marker c is arbitrary, such as circular, triangular, or quadrilateral. Marker c can be made of, for example, quartz glass with down-doping agents such as fluorine or boron. In this case, the refractive index of marker c is lower than that of cladding b. Marker c can also be made of quartz glass with up-doping agents such as germanium, aluminum, phosphorus, or chlorine. In this case, the refractive index of marker c is higher than that of cladding b. Marker c can be formed using methods such as aperture methods, stacking and pulling methods. The outer diameter of marker c is typically smaller than the outer diameter of the fiber core ai.

[0073] In end faces σ1 and σ2, the center of mark c is positioned to avoid axis L1. In other words, in end faces σ1 and σ2, the center (geometric center) of mark c is located outside axis L1. Furthermore, mark c only needs to be positioned so that its center avoids axis L1; a portion of mark c may also overlap with axis L1.

[0074] also, Figure 3 The cores a1 to a4 of the illustrated multi-core fiber MF can also be considered as symmetrically arranged with respect to axis L2, axis L3, and axis L4. Here, axis L2 is an axis orthogonal to both the central axis L0 and axis L1. Furthermore, axes L3 and L4 are axes orthogonal to the central axis L0 and forming an angle of 45 degrees with axis L1. However, the core arrangement in a multi-core fiber MF is not limited to this arrangement. Figure 3 The example illustrates a four-axis symmetry configuration. If the core configuration is linearly symmetric with respect to at least one of these four axes, then the conventional connection and the flip connection described later can be achieved.

[0075] In addition to the cores a1~an used for communication, multi-core optical fiber (MF) can also have dummy cores (Japanese: ダミーコア) that are not used for communication. Figure 3(Not shown in the figure). In this case, regarding the fiber cores whose positions are determined in the pre-welding measurement step S12 and the post-welding measurement step S16, (1) can be only fiber cores a1~an used for communication, (2) can be only dummy fiber cores not used for communication, or (3) can be both fiber cores a1~an used for communication and dummy fiber cores not used for communication.

[0076] (Specific examples of fiber optic connection points)

[0077] Reference Figures 4-6 Specific examples of the connection points for optical fibers OF1 and OF2 will be explained. Here, the connection method of optical fibers OF1 and OF2 when they are multi-core optical fibers (MF) will be explained.

[0078] The connection methods for optical fiber OF1 and OF2 include normal connection, non-normal connection, and reverse connection.

[0079] Figure 4 This diagram illustrates the connection points for typical connections. (a) is a side view of optical fibers OF1 and OF2, (b) is a front view of the end face σ2 of optical fiber OF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ1 of optical fiber OF2 viewed from the direction of line of sight E1. The connection points for typical connections are either the connection points that connect the end face σ2 of optical fiber OF1 to the end face σ1 of optical fiber OF2, or the connection points that connect the end face σ1 of optical fiber OF1 to the end face σ2 of optical fiber OF2. Figure 4 (This refers to the former case). The connection points typically meet the following conditions.

[0080] Condition 1: The cores a1~an of the end face σ1 of optical fiber OF2 overlap with any one of the cores a1~an of the end face σ2 of optical fiber OF1. Specifically, (1) the core a1 of the end face σ1 of optical fiber OF2 overlaps with the core a1 of the end face σ2 of optical fiber OF1, (2) the core a2 of the end face σ1 of optical fiber OF2 overlaps with the core a2 of the end face σ2 of optical fiber OF1, (3) the core a3 of the end face σ1 of optical fiber OF2 overlaps with the core a3 of the end face σ2 of optical fiber OF1, (4) the core a4 of the end face σ1 of optical fiber OF2 overlaps with the core a4 of the end face σ2 of optical fiber OF1.

[0081] Condition 2a: Mark c on end face σ1 of optical fiber OF2 overlaps with mark c on end face σ2 of optical fiber OF2.

[0082] In short, the connection is usually an optical coupling of fiber cores a1~an and a connection marked c is connected.

[0083] Furthermore, in optical fibers OF1 and OF2 are Figure 3In the exemplified case of multi-core fiber MF, in addition to the usual connection method of connecting the end face σ2 of fiber OF1 to the end face σ1 of fiber OF2, other methods are also considered. Figure 5 The connection method shown Figure 6 The connection method shown Figure 7 The connection method shown.

[0084] Figure 5 This indicates the connection method between fiber core a1 of optical fiber OF1 and fiber core a2 of optical fiber OF2. Figure 5 In the image, (a) is a side view of optical fibers OF1 and OF2, (b) is a front view of the end face σ2 of optical fiber OF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ1 of optical fiber OF2 viewed from the direction of line of sight E1.

[0085] Figure 6 This indicates the connection method between fiber core a1 of optical fiber OF1 and fiber core a3 of optical fiber OF2. Figure 6 In the image, (a) is a side view of optical fibers OF1 and OF2, (b) is a front view of the end face σ2 of optical fiber OF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ1 of optical fiber OF2 viewed from the direction of line of sight E1.

[0086] Figure 7 This indicates the connection method between fiber core a1 of optical fiber OF1 and fiber core a4 of optical fiber OF2. Figure 7 In the image, (a) is a side view of optical fibers OF1 and OF2, (b) is a front view of the end face σ2 of optical fiber OF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ1 of optical fiber OF2 viewed from the direction of line of sight E1.

[0087] Figures 5-7 The connection shown satisfies condition 1, but not condition 2a. Therefore, Figures 5-7 The connection method shown is not called a normal connection, but a non-normal connection.

[0088] Figure 8 This diagram illustrates the connection points of a flipped connection. (a) is a side view of optical fibers OF1 and OF2, (b) is a front view of the end face σ2 of optical fiber OF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ2 of optical fiber OF2 viewed from the direction of line of sight E1. The connection point of a flipped connection is the connection point that connects the end face σ2 of optical fiber OF1 to the end face σ2 of optical fiber OF2, or the connection point that connects the end face σ1 of optical fiber OF1 to the end face σ1 of optical fiber OF2. Figure 5 (This refers to the former case). The connection parts of the flip connection meet the following conditions.

[0089] Condition 1: The cores a1~an of the end face σ1 of optical fiber OF2 overlap with any one of the cores a1~an of the end face σ2 of optical fiber OF1. Specifically, (1) the core a1 of the end face σ2 of optical fiber OF2 overlaps with the core a4 of the end face σ2 of optical fiber OF1, (2) the core a2 of the end face σ2 of optical fiber OF2 overlaps with the core a3 of the end face σ2 of optical fiber OF1, (3) the core a3 of the end face σ2 of optical fiber OF2 overlaps with the core a2 of the end face σ2 of optical fiber OF1, (4) the core a4 of the end face σ2 of optical fiber OF2 overlaps with the core a1 of the end face σ2 of optical fiber OF1.

[0090] Condition 2b: The mark c on the end face σ2 of fiber OF2 overlaps with the position x on the end face σ2 of fiber OF1 that is symmetrical with respect to axis L1 and the mark c line of fiber OF1.

[0091] In short, a flip connection refers to a connection method in which the fiber cores a1~an are optically coupled and the marker c is not connected.

[0092] Furthermore, in optical fibers OF1 and OF2 are Figure 3 In the exemplified case of multi-core fiber MF, as a connection method for connecting the end face σ2 of fiber OF1 to the end face σ2 of fiber OF2, besides Figure 8 In addition to the flip connection shown, also consider Figure 9 The connection method shown Figure 10 The connection method shown Figure 11 The connection method shown.

[0093] Figure 9 This indicates the connection method between fiber core a1 of optical fiber OF1 and fiber core a3 of optical fiber OF2. Figure 9 In the image, (a) is a side view of optical fibers OF1 and OF2, (b) is a front view of the end face σ2 of optical fiber OF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ1 of optical fiber OF2 viewed from the direction of line of sight E1. Figure 9 The connection shown satisfies condition 1, and also satisfies condition 2b when axis L1 is replaced with axis L3. Therefore, Figure 9 The connection shown is called a flip connection relative to axis L3.

[0094] Figure 10 This indicates the connection method between fiber core a1 of optical fiber OF1 and fiber core a2 of optical fiber OF2. Figure 10 In the image, (a) is a side view of optical fibers OF1 and OF2, (b) is a front view of the end face σ2 of optical fiber OF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ1 of optical fiber OF2 viewed from the direction of line of sight E1. Figure 10 The connection shown satisfies condition 1, and also satisfies condition 2b when axis L1 is replaced with axis L2. Therefore, Figure 10 The connection shown is called a flip connection relative to axis L2.

[0095] Figure 11 This indicates the connection method between fiber core a1 of optical fiber OF1 and fiber core a1 of optical fiber OF2. Figure 11 In the image, (a) is a side view of optical fibers OF1 and OF2, (b) is a front view of the end face σ2 of optical fiber OF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ1 of optical fiber OF2 viewed from the direction of line of sight E1. Figure 11 The connection shown satisfies condition 1, and also satisfies condition 2b when axis L1 is replaced with axis L4. Therefore, Figure 11 The connection shown is called a flip connection relative to axis L4.

[0096] (Pre-arranged relationship)

[0097] As described above, in the alignment process S13, the control unit of the fusion splicing device 1 aligns the optical fibers OF1 and OF2 to ensure that the marking positions of the optical fibers OF1 and OF2 satisfy a "predetermined relationship". Furthermore, in the determination process S17, the control unit of the fusion splicing device 1 determines whether the marking positions of the optical fibers OF1 and OF2 satisfy the "predetermined relationship". This "predetermined relationship" refers to the positional relationship between the marking c of optical fiber OF1 and the marking c of optical fiber OF2 when, in the case where optical fibers OF1 and OF2 are multi-core optical fibers (MF), the cores a1 to an of optical fiber OF1 are optically coupled to any one of the cores a1 to an of optical fiber OF2.

[0098] In optical fibers OF1 and OF2 are Figure 3 In the case of the multi-core fiber MF illustrated, the following eight positional relationships are considered as "predetermined relationships".

[0099] Relationship 1: In Figure 4 The positional relationship between marker c of fiber OF1 and marker c of fiber OF2 generated in the connection method (normal connection) shown.

[0100] Relationship 2: In Figure 5 The positional relationship between marker c of fiber OF1 and marker c of fiber OF2 generated in the connection method shown (non-normal connection).

[0101] Relationship 3: In Figure 6 The positional relationship between marker c of fiber OF1 and marker c of fiber OF2 generated in the connection method shown (non-normal connection).

[0102] Relationship 4: In Figure 7 The positional relationship between marker c of fiber OF1 and marker c of fiber OF2 generated in the connection method shown (non-normal connection).

[0103] Relationship 5: In Figure 8 The positional relationship between the marker c of fiber OF1 and the marker c of fiber OF2 generated in the connection method shown (reversed connection relative to axis L1).

[0104] Relationship 6: In Figure 9 The positional relationship between mark c of fiber OF1 and mark c of fiber OF2 generated in the connection method shown (reversed connection relative to axis L3).

[0105] Relationship 7: In Figure 10 The positional relationship between mark c of fiber OF1 and mark c of fiber OF2 generated in the connection method shown (reversed connection relative to axis L2).

[0106] Relationship 8: In Figure 11 The positional relationship between mark c of fiber OF1 and mark c of fiber OF2 generated in the connection method shown (reversed connection relative to axis L4).

[0107] For example, when the fusion splice connection of optical fibers OF1 and OF2 is a normal connection (Relationship 1), the direction dependence of the transmitted light intensities I1 and I2 of optical fibers OF1 and OF2 obtained in the measurement process S16 after fusion splicing is as follows: Figure 12 As shown in (a). Furthermore, when the fusion splice connection of optical fibers OF1 and OF2 is a reverse connection relative to axis L1 (relationship 5), the direction dependence of the transmitted light intensities I1 and I2 of optical fibers OF1 and OF2 obtained in the measurement process S16 after fusion splicing is, for example, as... Figure 12 As shown in (b). Furthermore, Figure 12 The direction dependence of the transmitted light intensities I1 and I2 shown was obtained by using a camera as a side-view scan of the light detector 12.

[0108] In the direction dependence of transmitted light intensities I1 and I2, the direction in which the peak appears corresponds to the direction in which the fiber core ai is closer to the light source 11 in the direction in which the light source 11, fiber core ai, and photodetector 12 are arranged in a row. Similarly, in the direction dependence of transmitted light intensities I1 and I2, the direction in which the trough appears corresponds to the direction in which the mark c is closer to the light source 11 in the direction in which the light source 11, mark c, and photodetector 12 are arranged in a row. Therefore, the control unit of the fusion splicing device 1 can determine the fiber core positions of optical fibers OF1 and OF2 based on the direction of the peak in the direction dependence of transmitted light intensities I1 and I2, and can determine the mark positions of optical fibers OF1 and OF2 based on the direction of the trough in the direction dependence of transmitted light intensities I1 and I2.

[0109] The control unit of the fusion splicing device 1 selects one of the relationships 1 to 8. For example, among the relationships 1 to 8, the relationship closest to the marking positions of optical fibers OF1 and OF2 determined in the pre-fusion splicing measurement step S12 is selected (the most similar relationship). Furthermore, "the relationship closest to the marking positions of optical fibers OF1 and OF2 determined in the pre-fusion splicing measurement step S12" can be defined, for example, as follows: that is, optical fibers OF1 and OF2 are rotated and aligned in a manner that matches the core position of optical fiber OF1 with the core position of optical fiber OF2 with the smallest possible rotation. At this time, the condition is met that "the core position and marking position of optical fibers OF1 and OF2 after rotation alignment are consistent with the core position and marking position of optical fibers OF1 and OF2 that satisfy any one of the relationships 1 to 8". Alternatively, any one of relations 1 to 8 satisfies the condition that "the core position and marking position of optical fibers OF1 and OF2 after rotational alignment are consistent with the core position and marking position of optical fibers OF1 and OF2 that satisfy this relation." Among relations 1 to 8, the relation satisfying this condition is called "the relation closest to the relation of the marking positions of optical fibers OF1 and OF2 determined in the pre-fusion splicing measurement step S12." Then, in the alignment step S13, the control unit of the fusion splicing device 1 aligns optical fibers OF1 and OF2 so that the marking positions of optical fibers OF1 and OF2 satisfy the selected relation. Furthermore, in the determination step S17, the control unit of the fusion splicing device 1 determines whether the marking positions of optical fibers OF1 and OF2 satisfy the selected relation. Therefore, according to the inspection method S10 in this embodiment, it is possible to determine which of relations 1 to 8 the connection method of optical fibers OF1 and OF2 satisfies, and to fusion splice optical fibers OF1 and OF2 in the determined connection method.

[0110] Furthermore, the range of directions for measuring the transmitted light intensities I1 and I2 in the post-fusion splicing measurement process S16 can also be limited according to the selected relationship. For example, the marking positions of optical fibers OF1 and OF2 satisfy relationship 1 ( Figure 4 Relationship 2 Figure 5 Relationship 5 Figure 8 Relationship 8 Figure 11In the case where the markings c of optical fibers OF1 and OF2 are located, the direction is within 90° or less when viewed from the center of optical fibers OF1 and OF2. Therefore, in this case, the range of the direction for measuring the transmitted light intensities I1 and I2 in the post-fusion splicing measurement step S16 can be limited to, for example, 90°. As a result, the time required for side-view scanning in the post-fusion splicing measurement step S16 can be shortened. In addition, in this case, in order to further shorten the time required for side-view scanning in the post-fusion splicing measurement step S16, in the alignment step S13, it is preferable to align optical fibers OF1 and OF2 with the markings c of optical fibers OF1 and OF2 facing the light source 11.

[0111] Furthermore, when the core configuration in the cross-sections of optical fibers OF1 and OF2 has n-fold symmetry, the range of directions around the axes of optical fibers OF1 and OF2 when measuring the transmitted light intensities I1 and I2 in the post-fusion splicing measurement step S16 can be limited to a range of k×360° / n or less, where k is any natural number less than n. Alternatively, this range can be limited to a range of (3 / 2)×k×360° / n or less, where k is any natural number less than (2 / 3)×n. As an example, the range of measured transmitted light intensities I1 and I2 in the post-fusion splicing measurement step S16 can be limited to a range of 360° / n or less, or a range of (3 / 2)×360° / n or less (in the case of k=1). Alternatively, the range of measured transmitted light intensities I1 and I2 in the post-fusion splicing measurement step S16 can be limited to a range of 2×360° / n or less, or a range of (3 / 2)×2×360° / n or less (in the case of k=2). In addition, the lower limit of the above range is arbitrary, for example, it can be (k-1)×360° / n+15°.

[0112] Therefore, it is possible to determine the matching of k fiber cores (the upper limit of the above range is k×360° / n) or k+1 fiber cores (the upper limit of the above range is 1.5×k×360° / n). Furthermore, compared to rotating fibers OF1 and OF2 360° to perform side-view scanning from all directions, the time required for side-view scanning in the post-fusion splicing measurement step S16 can be shortened. The smaller k is, the shorter the time required for side-view scanning. This is because the range for side-view scanning becomes narrower. On the other hand, the larger k is, the higher the accuracy of determining fiber core matching. This is because the number of fiber cores whose positions can be measured increases.

[0113] Furthermore, in this case, when measuring the transmitted light intensities I1 and I2 in the post-fusion splicing measurement step S16, the range of the axial directions of optical fibers OF1 and OF2 is preferably a range including mark c and less than or equal to k×360° / n, where k is any natural number less than n. Alternatively, this range is preferably a range including mark c and less than or equal to (3 / 2)×k×360° / n, where k is any natural number less than or equal to (2 / 3)×n. Thus, in the post-fusion splicing measurement step S16, in addition to the matching of the fiber cores, the matching of mark c can also be determined. Furthermore, compared to the case where optical fibers OF1 and OF2 are rotated 360° and side-viewed scanning is performed from all directions, the time required for side-viewing scanning can be shortened in the post-fusion splicing measurement step S16. Alternatively, instead of setting the upper limit of the aforementioned range to (3 / 2)×k×360° / n, the upper limit of the aforementioned range can be set to k×360° / n+(the half-width of the peak corresponding to the fiber core in the curve representing the direction dependence of transmitted light intensity I1, I2). In this case, the matching of k+1 fiber cores can also be determined. Furthermore, compared to rotating optical fibers OF1 and OF2 360° and performing side-view scanning from all directions, the time required for side-view scanning in the post-fusion splicing measurement step S16 can be shortened.

[0114] Furthermore, the control unit of the fusion splicing device 1 can also be configured to select two or more relationships from the above relationships 1 to 8, and determine in the determination step S17 whether the marking positions of optical fibers OF1 and OF2 satisfy any one of the selected two or more relationships. Among the relationships 5 to 8 that conform to the flip connection, the relationship in which the markings of optical fibers OF1 and OF2 are particularly close is relationship 5, where each marking is close to the other when sandwiched between the two fiber cores. Figure 8 ), and the relationship between each mark and the fiber core is close (8). Figure 11 The range of directions for measuring transmitted light intensities I1 and I2 that satisfy a given relationship is minimized, depending on the position of marker c. Therefore, when selecting relationships that conform to normal connections and relationships that conform to reverse connections, relationship 1 is preferred. Figure 4 ) and relation 5 ( Figure 8 ), or select relation 1 ( Figure 4 ) and relation 8 ( Figure 11When any one of these options is selected, the proximity of the markers allows for a significant reduction in the directional range when measuring the transmitted light intensities I1 and I2, making marker position measurement easier. Furthermore, when relationship 5 is selected, marker c of fiber OF1 and marker c of OF2 are close together, sandwiched between two fiber cores. Therefore, even if the side-view scan range is limited to between these two fiber cores, the positions of both marker c of fiber OF1 and marker c of OF2 can be measured. On the other hand, when relationship 8 is selected, marker c of fiber OF1 and marker c of OF2 are close together, separated by one fiber core. Therefore, if the side-view scan range is limited to between this fiber core and the adjacent fiber core, only the position of one of the marker c of fiber OF1 and marker c of OF2 can be measured. Thus, when the latter option is selected, if the positions of both marker c of fiber OF1 and marker c of OF2 are to be measured, the side-view scan range needs to be expanded, resulting in a longer side-view scan time compared to the former option. Therefore, choosing relation 1 and relation 5 is preferable to choosing relation 1 and relation 8.

[0115] (Estimation of connection loss)

[0116] As mentioned above, in the determination process S17, the coupling efficiency or connection loss can also be estimated based on the core positions of optical fibers OF1 and OF2. (Refer to...) Figure 13 This supplements the estimation methods for the coupling efficiency or connection loss that can be utilized in this case. Figure 13 In the image, (a) is a side view of optical fibers OF1 and OF2, (b) is a front view of the end face σ2 of optical fiber OF1 viewed from the direction of line of sight E2, and (c) is a front view of the end face σ2 of optical fiber OF2 viewed from the direction of line of sight E1.

[0117] First, the difference Δθi between the transmitted light intensities I1 and I2 measured in the post-welding measurement process S16 and the peak direction corresponding to the fiber core ai is determined. For example... Figure 13 As shown, viewed from the center of optical fibers OF1 and OF2, the difference Δθi represents the difference between the direction of the fiber core ai of optical fiber OF1 and the direction of the fiber core ai of optical fiber OF2. Hereinafter, this difference Δθi will be recorded as the rotational offset Δθi of the fiber core ai.

[0118] Next, based on the rotational offset Δθi of fiber core ai, the position offset Δdi of fiber core ai is calculated according to the following formula (1). Here, r is a predetermined constant representing the distance from the center of optical fibers OF1 and OF2 to fiber cores a1~an.

[0119] [Number 1]

[0120] …(1)

[0121] Next, based on the position offset Δdi of the fiber core ai, the coupling efficiency ηi of the fiber core ai is calculated according to the following formula (2). Here, w1 is a predetermined constant representing the mode field radius of the fiber core ai of fiber OF1. In addition, w2 is a predetermined constant representing the mode field radius of the fiber core ai of fiber OF2.

[0122] [Number 2]

[0123] …(2)

[0124] Finally, the average coupling efficiency η is calculated by averaging the coupling efficiency ηi of each fiber core ai. Alternatively, (1) the average rotational offset Δθ is calculated by averaging the rotational offset Δθi of each fiber core ai, (2) the average positional offset Δd is calculated based on the average rotational offset Δθ, and (3) the average coupling efficiency η is calculated based on the average positional offset Δd. Or, (1) the two curves representing the direction dependence of the transmitted light intensity I1 and I2 of optical fibers OF1 and OF2 obtained in the measurement process S16 after fusion splicing (refer to...) Figure 12 When one of the curves shifts in the direction of rotation angle, the correlation coefficient of the two curves is taken as the largest offset as the average rotation offset Δθ. (2) Calculate the average position offset Δd based on the average rotation offset Δθ. (3) Calculate the average coupling efficiency η based on the average position offset Δd.

[0125] Furthermore, given the estimated connection loss, the connection loss can be calculated using a known method based on the average coupling efficiency η.

[0126] (Welding connection system and inspection system)

[0127] A welding system is a system consisting of one or more devices that perform the various steps constituting welding method S1 (excluding steps performed by the operator). Each device may be configured to perform a single step or multiple steps. When the welding system consists of a single device, it is configured in the same way as the welding device 1 described above. When the welding system consists of multiple devices, it is configured as follows, for example.

[0128] For example, a welding system may include a first device that performs a pre-welding measurement step S12, a self-aligning step S13, a butt-joining step S14, and a welding step S15, and a second device that performs a post-welding measurement step S16, a judgment step S17, and a estimation step S18. In this case, the first device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), heating unit, and control unit. In this case, the control unit of the first device can use the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), and heating unit to perform the pre-welding measurement step S12, the self-aligning step S13, the butt-joining step S14, and the welding step S15. Similarly, the second device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, etc.), and control unit. In this case, the control unit of the second device can use the aforementioned light source, photodetector, and self-aligning mechanism (rotation mechanism, etc.) to perform the post-welding measurement step S16, the judgment step S17, and the estimation step S18.

[0129] In this configuration, the fusion-spliced ​​optical fibers OF1 and OF2 are transferred from the first device to the second device while fixed to a holding member (e.g., an optical fiber support that can be detached from both the first and second devices). Alternatively, the holding member may remain in the first device, and only the fusion-spliced ​​optical fibers OF1 and OF2 are transferred from the first device to the second device. Furthermore, the measurement results of the pre-fusion measurement step S12 can be transmitted from the first device to the control unit of the second device via communication. Additionally, if a robot or similar device performs the preparation step S11, the device performing the preparation step S11 can also be included in the fusion splicing system. The mechanism performing the preparation step S11 (e.g., the aforementioned alignment mechanism) can also be built into the first device. Furthermore, the transfer of optical fibers OF1 and OF2 from the first device to the second device can be performed by an operator or by a robot or similar device. If the transfer is performed by a device, that device can also be added as a component of the fusion splicing system.

[0130] Alternatively, the welding system may be a system comprising a first device performing a pre-welding measurement step S12, and a second device performing a self-aligning step S13, a butt joint step S14, a welding step S15, a post-welding measurement step S16, a judgment step S17, and a estimation step S18. In this case, the first device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), and control unit. In this case, the control unit of the first device can use the aforementioned light source, photodetector, and self-aligning mechanism (rotation mechanism, translation mechanism, etc.) to perform the pre-welding measurement step S12. Furthermore, the second device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), heating unit, and control unit. In this case, the control unit of the second device uses the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), and heating unit to perform the self-aligning step S13, the butt joint step S14, the welding step S15, the post-welding measurement step S16, the judgment step S17, and the estimation step S18.

[0131] In this configuration, optical fibers OF1 and OF2 are transferred from the first device to the second device, respectively, while fixed to a holding component (e.g., an optical fiber support that can be detached from both the first and second devices). Furthermore, the measurement results of the pre-fusion splicing measurement step S12 are transmitted from the first device to the second device via communication. Moreover, the transfer of optical fibers OF1 and OF2 from the first device to the second device can be performed by an operator or by a device such as a robot. If the transfer is performed by a device, that device can also be incorporated into the fusion splicing system.

[0132] Alternatively, the welding system may be a system comprising a first device that performs a pre-welding measurement step S12 and a self-aligning step S13, and a second device that performs a butt welding step S14, a welding step S15, a post-welding measurement step S16, a judgment step S17, and a estimation step S18. In this case, the first device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), and control unit. In this case, the control unit of the first device can use the aforementioned light source, photodetector, and self-aligning mechanism (rotation mechanism, translation mechanism, etc.) to perform the pre-welding measurement step S12 and the self-aligning step S13. Furthermore, the second device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), heating unit, and control unit. In this case, the control unit of the second device uses the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), and heating unit to perform the butt welding step S14, the welding step S15, the post-welding measurement step S16, the judgment step S17, and the estimation step S18.

[0133] In this configuration, optical fibers OF1 and OF2 are transferred from the first device to the second device, respectively, while fixed to a holding component (e.g., an optical fiber support that can be detached from both the first and second devices). Furthermore, the measurement results of the pre-fusion splicing measurement step S12 can also be transmitted from the first device to the second device via communication. Moreover, the transfer of optical fibers OF1 and OF2 from the first device to the second device can be performed by an operator or by a device such as a robot. If the transfer is performed by a device, that device can also be incorporated into the fusion splicing system.

[0134] Alternatively, the welding system may be a system comprising a first device that performs a pre-welding measurement step S12 and a self-aligning step S13, a second device that performs a butt joint step S14 and a welding step S15, and a third device that performs a post-welding measurement step S16, a judgment step S17, and a estimation step S18. In this case, the first device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), and control unit. In this case, the control unit of the first device can use the aforementioned light source, photodetector, and self-aligning mechanism (rotation mechanism, translation mechanism, etc.) to perform the pre-welding measurement step S12 and the self-aligning step S13. Furthermore, the second device may, for example, consist of the aforementioned self-aligning mechanism (translation mechanism, etc.), a heating unit, and control unit. In this case, the control unit of the second device can use the aforementioned self-aligning mechanism (translation mechanism, etc.) and the heating unit to perform the butt joint step S14 and the welding step S15. Furthermore, the third device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, etc.), and control unit. In this case, the control unit of the third device can use the aforementioned light source, photodetector, and self-aligning mechanism (rotation mechanism, etc.) to perform the post-weld measurement process S16, the judgment process S17, and the estimation process S18.

[0135] In this configuration, the aligned optical fibers OF1 and OF2 are transferred from the first device to the second device while fixed to the retaining member (e.g., an optical fiber support that can be detached from the first, second, and third devices). Here, the positional relationship of the optical fibers OF1 and OF2 is maintained by aligning the retaining member's orientation towards the second device with its orientation towards the first device. Then, the fusion-spliced ​​optical fibers OF1 and OF2 are transferred from the second device to the third device while fixed to the retaining member. Alternatively, the retaining member can remain in the second device, and only the fusion-spliced ​​optical fibers OF1 and OF2 are transferred from the second device to the third device. Furthermore, the measurement results of the pre-fusion measurement step S12 are transmitted from the first device to the second device via communication, and, as needed, from either the first or second device to the third device via communication. Additionally, if the preparation step S11 is performed by a device such as a robot, the device performing the preparation step S11 can also be included in the fusion splicing system. The mechanism performing the preparation step S11 (e.g., the aforementioned alignment mechanism) can also be built into the first device. Furthermore, the transfer of optical fibers OF1 and OF2 from the first device to the second device can be performed by an operator or by a robot or other device. When this transfer is performed by a device, that device can also be incorporated into the fusion splicing system. Similarly, the transfer of optical fibers OF1 and OF2 from the second device to the third device can be performed by an operator or by a robot or other device. When this transfer is performed by a device, that device can also be incorporated into the fusion splicing system.

[0136] Furthermore, the inspection system is a system comprising one or more devices that implement each step of the inspection method S10 (excluding steps performed by the operator). Each device may be configured to perform a single step or multiple steps. When the inspection system is composed of a single device, it is configured similarly to the inspection system 10 described above (the structure after removing the heating part 13 from the welding connection device 1). When the inspection system is composed of multiple devices, it is configured, for example, as follows.

[0137] For example, the inspection system may be a system comprising a first device that performs a pre-welding measurement step S12 and a self-aligning step S13, and a second device that performs a post-welding measurement step S16, a judgment step S17, and a estimation step S18. In this case, the first device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), and control unit. In this case, the control unit of the first device can use the aforementioned light source, photodetector, and self-aligning mechanism (rotation mechanism, translation mechanism, etc.) to perform the pre-welding measurement step S12 and the self-aligning step S13. Similarly, the second device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, etc.), and control unit. In this case, the control unit of the second device uses the aforementioned light source, photodetector, and self-aligning mechanism (rotation mechanism, etc.) to perform the post-welding measurement step S16, the judgment step S17, and the estimation step S18.

[0138] In this configuration, the aligned optical fibers OF1 and OF2, while fixed to a holding member (e.g., an optical fiber support detachable from the first device, the fusion splicing device described later, and the second device), are transferred from the first device to the fusion splicing device (a device separate from the first and second devices that performs the docking process S14 and the fusion splicing process S15). Here, the positional relationship of the optical fibers OF1 and OF2 is maintained by ensuring that the holding member is positioned in the same way as it is positioned in the first device. Furthermore, the fusion-connected optical fibers OF1 and OF2, while fixed to the aforementioned holding member, are transferred from the fusion splicing device to the second device. Alternatively, the holding member may remain in the fusion splicing device, and only the fusion-connected optical fibers OF1 and OF2 are transferred from the fusion splicing device to the second device. Additionally, the measurement results of the pre-fusion measurement process S12 are transmitted from the first device to the fusion splicing device via communication at least once, and the measurement results of the pre-fusion measurement process S12 are transmitted from the first device or the fusion splicing device to the second device via communication as needed. Furthermore, when a robot or similar device performs the preparation step S11, the device performing the preparation step S11 can also be included in the inspection system. The mechanism performing the preparation step S11 (e.g., the aforementioned alignment mechanism) can also be built into the first device. Additionally, the transfer of optical fibers OF1 and OF2 from the first device to the fusion splicing device can be performed by an operator or by a robot or similar device. When this transfer is performed by a device, that device can also be added to the components of the inspection system. Similarly, the transfer of optical fibers OF1 and OF2 from the fusion splicing device to the second device can be performed by an operator or by a robot or similar device. When this transfer is performed by a device, that device can also be added to the components of the inspection system.

[0139] Alternatively, the inspection system may be a system comprising a first device performing a pre-welding measurement step S12, a second device performing a self-aligning step S13, and a third device performing a post-welding measurement step S16, a judgment step S17, and an estimation step S18. In this case, the first device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, translation mechanism, etc.), and control unit. In this case, the control unit of the first device can use the aforementioned light source, photodetector, and self-aligning mechanism (rotation mechanism, translation mechanism, etc.) to perform the pre-welding measurement step S12. Furthermore, the second device may, for example, consist of the aforementioned self-aligning mechanism (translation mechanism, etc.) and control unit. In this case, the control unit of the second device can use the aforementioned self-aligning mechanism (translation mechanism, etc.) to perform the self-aligning step S13. Furthermore, the third device may, for example, consist of the aforementioned light source, photodetector, self-aligning mechanism (rotation mechanism, etc.), and control unit. In this case, the control unit of the third device can use the aforementioned light source, photodetector, and self-aligning mechanism (rotation mechanism, etc.) to perform the post-weld measurement process S16, the judgment process S17, and the estimation process S18.

[0140] In this configuration, the aligned optical fibers OF1 and OF2, while fixed to the holding member (e.g., an optical fiber support that can be detached from the first device, the fusion splicing device described later, the second device, and the third device), are transferred from the first device to the second device. Here, the positional relationship of the optical fibers OF1 and OF2 is maintained by aligning the holding member's orientation toward the second device with its orientation toward the first device. Furthermore, the aligned optical fibers OF1 and OF2, while fixed to the holding member, are transferred from the second device to the fusion splicing device (a device separate from the first, second, and third devices that performs the docking process S14 and the fusion splicing process S15). Here, the positional relationship of the optical fibers OF1 and OF2 is maintained by aligning the holding member's orientation toward the fusion splicing device with its orientation toward the second device. Then, the fusion-connected optical fibers OF1 and OF2, while fixed to the aforementioned holding member, are transferred from the fusion splicing device to the third device. The retaining component can remain in the fusion splicing device, and only the fusion-bonded optical fibers OF1 and OF2 are transferred from the fusion splicing device to the third device. Furthermore, the measurement results of the pre-fusion measurement step S12 are transmitted at least from the first device to the second device via communication, and from the second device to the fusion splicing device via communication, and as needed, from the first device, the second device, or the fusion splicing device to the third device via communication. Moreover, if the preparation step S11 is performed by a device such as a robot, the device performing the preparation step S11 can also be included in the fusion splicing system. The mechanism performing the preparation step S11 (e.g., the aforementioned alignment mechanism) can also be built into the first device. Additionally, the transfer of optical fibers OF1 and OF2 from the first device to the second device can be performed by an operator or by a device such as a robot. If the transfer is performed by a device, that device can also be added as a component of the fusion splicing system. Similarly, the transfer of optical fibers OF1 and OF2 from the second device to the fusion splicing device can be performed by an operator or by a device such as a robot. When this transfer is performed by the device, the device can also be added to the components of the fusion splicing system. Similarly, the transfer of optical fibers OF1 and OF2 from the fusion splicing device to a third device can be performed by an operator or by a device such as a robot. When this transfer is performed by the device, the device can also be added to the components of the fusion splicing system.

[0141] (Modified example)

[0142] When the markings for optical fibers OF1 and OF2 are low-refractive-index markings (markings where the refractive index is lower than that of the cladding), such as Figure 12As shown, in the curve representing the direction dependence of the transmitted light intensity of optical fibers OF1 and OF2, a trough shape appears in the direction corresponding to the marked position. Here, the trough shape refers to the shape of the curve where the transmitted light intensity changes from decreasing to increasing as the direction changes. Therefore, in this embodiment, a structure is adopted to determine the marked positions of optical fibers OF1 and OF2 based on the direction in which the trough shape appears in the curve representing the direction dependence of the transmitted light intensity of optical fibers OF1 and OF2.

[0143] However, the present invention is not limited thereto. That is, in the curve representing the direction dependence of the transmitted light intensity of optical fiber OF1, if a predetermined specific shape (first shape) appears in the direction corresponding to the marked position, a structure can be adopted to determine the marked position of optical fiber OF1 based on the direction in which that shape (first shape) appears in the curve. Similarly, in the curve representing the direction dependence of the transmitted light intensity of optical fiber OF2, if a predetermined specific shape (second shape) appears in the direction corresponding to the marked position, a structure can be adopted to determine the marked position of optical fiber OF2 based on the direction in which that shape (second shape) appears in the curve. Here, the specific shape (first shape) appearing in the direction corresponding to the marked position in the curve representing the direction dependence of the transmitted light intensity of optical fiber OF1, and the specific shape (second shape) appearing in the direction corresponding to the marked position in the curve representing the direction dependence of the transmitted light intensity of optical fiber OF2, can be the same shape or different shapes.

[0144] For example, when the markings for optical fibers OF1 and OF2 are high refractive index markings (markings where the refractive index is higher than that of the cladding), such as... Figure 14 As shown, in the curve representing the direction dependence of the transmitted light intensity of optical fibers OF1 and OF2, a peak shape appears in the direction corresponding to the marked position. Here, the peak shape refers to the shape of the curve where the transmitted light intensity changes from increasing to decreasing as the direction is changed. In this case, it is sufficient to use a structure that determines the marked positions of optical fibers OF1 and OF2 based on the direction in which the peak shape appears in the curve representing the direction dependence of the transmitted light intensity of optical fibers OF1 and OF2. Furthermore, from... Figure 14 It can also be seen that in the curves representing the direction dependence of the transmitted light intensity of optical fibers OF1 and OF2, the peak shapes corresponding to the fiber core positions appear periodically. Therefore, in the curves representing the direction dependence of the transmitted light intensity of optical fibers OF1 and OF2, the fiber core position can be determined based on the direction of the periodic peak shapes, and the marker position can be determined based on the direction of other peak shapes.

[0145] also, Figure 14(a) is a graph showing the direction dependence of the transmitted light intensities I1 and I2 of optical fibers OF1 and OF2 obtained in the measurement process S16 after fusion splicing, assuming a normal splice connection (Relationship 1). Additionally, Figure 14 (b) is a graph showing the direction dependence of the transmitted light intensity I1 and I2 of optical fibers OF1 and OF2 obtained in the measurement process S16 after fusion splicing when the fusion splice connection of optical fibers OF1 and OF2 is a reverse connection relative to axis L1 (relationship 5).

[0146] Additionally, in cases where the markings for optical fibers OF1 and OF2 are low-refractive-index markings (markers with a refractive index lower than the cladding) surrounded by a high-refractive-index region (a region with a refractive index higher than the cladding), such as... Figure 15 As shown, in the curve representing the direction dependence of the transmitted light intensity of optical fibers OF1 and OF2, a sawtooth shape appears in the direction corresponding to the marked position. Here, the sawtooth shape refers to the shape of the curve where, as the direction changes, the transmitted light intensity (1) changes from increasing to decreasing, (2) changes from decreasing to increasing, (3) changes from increasing to decreasing, and (4) changes from decreasing to increasing. In this case, it is sufficient to use a structure that determines the marked positions of optical fibers OF1 and OF2 based on the direction in which the sawtooth shape appears in the curve representing the direction dependence of the transmitted light intensity of optical fibers OF1 and OF2.

[0147] also, Figure 15 (a) is a graph showing the direction dependence of the transmitted light intensities I1 and I2 of optical fibers OF1 and OF2 obtained in the measurement process S16 after fusion splicing, assuming a normal splice connection (Relationship 1). Additionally, Figure 15 (b) is a graph showing the direction dependence of the transmitted light intensity I1 and I2 of optical fibers OF1 and OF2 obtained in the measurement process S16 after fusion splicing when the fusion splice connection of optical fibers OF1 and OF2 is a reverse connection relative to axis L1 (relationship 5).

[0148] In addition, based on the refractive index distribution of the markings on optical fibers OF1 and OF2, such as Figure 16 As shown, in the curve representing the direction dependence of the transmitted light intensity of optical fibers OF1 and OF2, a top-hat shape appears in the direction corresponding to the marked position. Here, the so-called top-hat shape refers to the shape of the curve in which the transmitted light intensity (1) changes from increasing to constant, and (2) changes from constant to decreasing as the direction is changed. In this case, it is sufficient to adopt a structure that determines the marked positions of optical fibers OF1 and OF2 based on the direction in which the top-hat appears in the curve representing the direction dependence of the transmitted light intensity of optical fibers OF1 and OF2.

[0149] also, Figure 16 (a) is a graph showing the direction dependence of the transmitted light intensities I1 and I2 of optical fibers OF1 and OF2 obtained in the measurement process S16 after fusion splicing, assuming a normal splice connection (Relationship 1). Additionally, Figure 16 (b) is a graph showing the direction dependence of the transmitted light intensity I1 and I2 of optical fibers OF1 and OF2 obtained in the measurement process S16 after fusion splicing when the fusion splice connection of optical fibers OF1 and OF2 is a reverse connection relative to axis L1 (relationship 5).

[0150] Furthermore, in the curve representing the direction dependence of the transmitted light intensity of the two optical fibers, the shapes corresponding to the marked positions can also be different. For example, if one fiber in optical fibers OF1 and OF2 is marked with a low refractive index and the other fiber is marked with a high refractive index, then trough shapes and crest shapes will appear.

[0151] (Additional Notes)

[0152] This invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. Embodiments obtained by appropriately combining the various technical means disclosed in the above embodiments are also included within the technical scope of this invention.

[0153] For example, the inspection method of the present invention only needs to include at least the above-described post-fusion splicing measurement step; other steps may or may not be included. Similarly, the inspection system of the present invention only needs to include at least the structure required to perform the above-described post-fusion splicing measurement step; structures required to perform other steps may or may not be included. Furthermore, the fusion splicing method of the present invention only needs to include at least the above-described post-fusion splicing measurement step and fusion splicing step; other steps may or may not be included. Additionally, the fusion splicing system of the present invention only needs to include at least the structure required to perform the above-described post-fusion splicing measurement step and fusion splicing step; structures required to perform other steps may or may not be included. Moreover, the manufacturing method of the optical fiber connector of the present invention, like the fusion splicing method of the present invention, only needs to include at least the above-described post-fusion splicing measurement step and fusion splicing step; other steps may or may not be included.

[0154] (Summarize)

[0155] The inspection method of Method 1 includes a post-fusion splice measurement process, in which, for two multi-core optical fibers with markings formed in the cladding and their end faces fused together, the position of the marking of the one multi-core optical fiber is determined according to the direction when a predetermined first shape appears in a curve representing the direction dependence of the transmitted light intensity of one of the two multi-core optical fibers, and the position of the marking of the other multi-core optical fiber is determined according to the direction when a predetermined second shape appears in a curve representing the direction dependence of the transmitted light intensity of the other multi-core optical fiber.

[0156] The inspection method of Method 2, based on the inspection method of Method 1, further includes a judgment step. In this judgment step, the success of the fusion is determined based on the position of the core of the two multi-core optical fibers or the mark determined in the post-fusion measurement step.

[0157] In the inspection method of Method 3, if the positional relationship of the marks in the two multi-core optical fibers determined by the post-fusion measurement process is a predetermined positional relationship, the fusion is determined to be successful; otherwise, if the positional relationship of the marks in the two multi-core optical fibers determined by the post-fusion measurement process is not the predetermined positional relationship, the fusion is determined to be unsuccessful.

[0158] The inspection method of Method 4, based on the inspection method of Method 3, further includes a pre-fusion splicing measurement process. In this pre-fusion splicing measurement process, before performing the process of splicing the two multi-core optical fibers, the positional relationship of the marks in the two multi-core optical fibers is determined. The predetermined positional relationship is the positional relationship of the marks in the two multi-core optical fibers that is closest to the positional relationship of the marks in the two multi-core optical fibers determined in the pre-fusion splicing measurement process, which is the possible positional relationship of the marks in the two multi-core optical fibers when each core of one multi-core optical fiber is optically coupled to any core of the other multi-core optical fiber.

[0159] The inspection method of Method 5 is based on the inspection method of Method 4. In the cross-section of the two multi-core optical fibers, the arrangement of the fiber cores has n-fold symmetry. The range of the direction for measuring the intensity of transmitted light in the post-fusion measurement process is limited to any range below k×360° / n, where k is any natural number less than n, or limited to any range below (3 / 2)×k×360° / n, where k is any natural number greater than 1 and less than (2 / 3)×n.

[0160] The inspection method of Method 6 is based on the inspection method of any of Methods 1 to 5. In the cross-section of the two multi-core optical fibers, the arrangement of the fiber cores has n-fold symmetry. The range of the direction for measuring the intensity of transmitted light in the post-fusion measurement process is limited to any range below k×360° / n, where k is any natural number less than n. Alternatively, it is limited to any range below (3 / 2)×k×360° / n, where k is any natural number greater than 1 and less than (2 / 3)×n.

[0161] The inspection method of method 7 is based on the inspection method of method 6, but limits the range of the direction for measuring the intensity of transmitted light in the post-welding measurement process to any range of k×360° / n or less, including the mark, where k is any natural number less than n, or limits it to any range of (3 / 2)×k×360° / n or less, including the mark, where k is any natural number greater than 1 and less than (2 / 3)×n.

[0162] The inspection method of method 8, based on the inspection methods of any of methods 1 to 7, further includes an estimation step, in which, based on one or both of the positions of the cores of the two multi-core optical fibers and the positions of the marks determined in the post-fusion measurement step, at least one of the following items (1) to (6) is estimated: (1) the coupling efficiency or connection loss of the two multi-core optical fibers; (2) the correspondence between the core number of the core of one multi-core optical fiber and the core number of the core of the other multi-core optical fiber optically coupled to that core; (3) the relationship between the cladding of the one multi-core optical fiber and the core number of the other multi-core optical fiber optically coupled to that core. (3) Which region among the multiple regions obtained by dividing the cladding of the other multi-core fiber contains the mark of the one multi-core fiber, and which region among the multiple regions obtained by dividing the cladding of the other multi-core fiber into multiple regions contains the mark of the other multi-core fiber; (4) One or both of the overlap and offset between the mark of the one multi-core fiber and the mark of the other multi-core fiber; (5) One or both of the overlap and offset between the core of the one multi-core fiber and the core of the other multi-core fiber optically coupled to the core; and (6) The polarity of the two multi-core fibers.

[0163] The inspection method of Method 9, based on any of the inspection methods of Methods 1 to 8, further includes a centering process, in which the two multi-core optical fibers are rotated and centered before the process of splicing the two multi-core optical fibers, so that the mark faces the light source side used in the measurement process after splicing.

[0164] The inspection method of Method 10 is based on the inspection method of any of Methods 1 to 9, wherein the mark is a low refractive index mark with a refractive index lower than that of the cladding, and the first shape and the second shape are trough shapes.

[0165] The inspection method of mode 11 is based on the inspection method of any of modes 1 to 9, wherein the mark is a high refractive index mark with a refractive index higher than that of the cladding, and the first shape and the second shape are crest shapes.

[0166] The inspection method of Method 12 is based on the inspection method of any of Methods 1 to 9, wherein the mark is a low refractive index mark surrounded by a high refractive index region with a refractive index higher than that of the cladding, and the first shape and the second shape are serrated.

[0167] The inspection method of method 13 is based on the inspection method of any of methods 1 to 9, wherein the mark of one multi-core optical fiber is a low refractive index mark with a refractive index lower than that of the cladding, and the mark of the other multi-core optical fiber is a high refractive index mark with a refractive index higher than that of the cladding, the first shape is a trough shape, and the second shape is a crest shape.

[0168] The inspection method of Method 14 includes: a post-fusion splicing measurement process, for two multi-core optical fibers with markings formed in the cladding and their end faces fused together, determining the position of the core or marking of one multi-core optical fiber based on the spatial distribution or directional dependence of the transmitted light intensity of one of the two multi-core optical fibers, and determining the position of the core or marking of the other multi-core optical fiber based on the spatial distribution or directional dependence of the transmitted light intensity of the other multi-core optical fiber; an estimation process, based on one or both of the positions of the cores and the markings of the two multi-core optical fibers determined in the post-fusion splicing measurement process, estimating at least one of the following items (1) to (6): (1) the coupling efficiency or connection loss of the two multi-core optical fibers; (2) the coupling efficiency or connection loss of one multi-core optical fiber. The correspondence between the core number of the fiber core and the core number of the other multi-core fiber optically coupled to the fiber core; (3) which region of a plurality of regions obtained by dividing the cladding of the one multi-core fiber into a plurality of regions contains the mark of the one multi-core fiber, and which region of a plurality of regions obtained by dividing the cladding of the other multi-core fiber into a plurality of regions contains the mark of the other multi-core fiber; (4) one or both of the overlap and offset between the mark of the one multi-core fiber and the mark of the other multi-core fiber; (5) one or both of the overlap and offset between the core of the one multi-core fiber and the core of the other multi-core fiber optically coupled to the fiber core; and (6) the polarity of the two multi-core fibers.

[0169] The inspection system of method 15 includes: a single light source or multiple light sources; a single photodetector or multiple photodetectors; and a single control unit or multiple control units. The single control unit or at least one of the multiple control units performs a post-fusion splice measurement process using the single light source or at least one of the multiple light sources and the single photodetector or at least one of the multiple photodetectors. In this post-fusion splice measurement process, for two multi-core optical fibers with markings formed in the cladding and their end faces fused together, the position of the marking of the one multi-core optical fiber is determined according to the direction when a predetermined first shape appears in a curve representing the direction dependence of the transmitted light intensity of one of the two multi-core optical fibers, and the position of the marking of the other multi-core optical fiber is determined according to the direction when a predetermined second shape appears in a curve representing the direction dependence of the transmitted light intensity of the other multi-core optical fiber.

[0170] Explanation of reference numerals in the attached figures

[0171] S1 Fusion Connection Method

[0172] S10 Inspection Method

[0173] S11 Preparation process

[0174] S12 Pre-welding measurement process

[0175] S13 Self-aligning process

[0176] S14 Docking Process

[0177] S15 Welding Process

[0178] S16 Post-welding measurement process

[0179] S17 Judgment Process

Claims

1. An inspection method, characterized in that, The method includes a post-fusion splicing measurement process, in which, for two multi-core optical fibers with markings formed in the cladding and their end faces fused together, the position of the marking of one multi-core optical fiber is determined according to the direction when a predetermined first shape appears in a curve representing the direction dependence of the transmitted light intensity of one of the two multi-core optical fibers, and the position of the marking of the other multi-core optical fiber is determined according to the direction when a predetermined second shape appears in a curve representing the direction dependence of the transmitted light intensity of the other multi-core optical fiber.

2. The inspection method according to claim 1, characterized in that, It also includes a determination process, in which the success of the fusion is determined based on the position of the core of the two multi-core optical fibers or the mark determined in the post-fusion measurement process.

3. The inspection method according to claim 2, characterized in that, In the determination process, if the positional relationship of the marks in the two multi-core optical fibers determined by the post-fusion measurement process is a predetermined positional relationship, the fusion is determined to be successful; otherwise, if the positional relationship of the marks in the two multi-core optical fibers determined by the post-fusion measurement process is not the predetermined positional relationship, the fusion is determined to be unsuccessful.

4. The inspection method according to claim 3, characterized in that, It also includes a pre-fusion splicing measurement process, in which the positional relationship of the marks in the two multi-core optical fibers is determined before the process of splicing the two multi-core optical fibers is carried out. The predetermined positional relationship is the positional relationship among the possible positional relationships of the marks in the two multi-core optical fibers that are closest to the positional relationship of the marks in the two multi-core optical fibers determined in the measurement process before fusion splicing, when each core of the multi-core optical fiber is optically coupled to any core of the other multi-core optical fiber.

5. The inspection method according to claim 4, characterized in that, In the pre-fusion splicing measurement process, the position of the mark in the one multi-core optical fiber is determined based on the spatial distribution or direction dependence of the transmitted light intensity of the one multi-core optical fiber, and the position of the mark in the other multi-core optical fiber is determined based on the spatial distribution or direction dependence of the transmitted light intensity of the other multi-core optical fiber.

6. The inspection method according to any one of claims 1 to 5, characterized in that, In the cross-sections of the two multi-core optical fibers, the arrangement of the fiber cores exhibits n-fold symmetry. The range of the direction for measuring the intensity of transmitted light in the post-welding measurement process is limited to any range below k×360° / n, where k is any natural number less than n, or limited to any range below (3 / 2)×k×360° / n, where k is any natural number greater than 1 and less than (2 / 3)×n.

7. The inspection method according to claim 6, characterized in that, The range of directions for measuring the intensity of transmitted light in the post-welding measurement process is limited to any range including the marked k×360° / n or less, where k is any natural number less than n, or limited to any range including the marked (3 / 2)×k×360° / n or less, where k is any natural number greater than 1 and less than (2 / 3)×n.

8. The inspection method according to any one of claims 1 to 7, characterized in that, It also includes an estimation process, in which, based on one or both of the positions of the cores of the two multi-core optical fibers and the positions of the marks determined in the post-fusion measurement process, at least one of the following items (1) to (6) is estimated: (1) the coupling efficiency or connection loss of the two multi-core optical fibers; (2) the correspondence between the core number of the core of one multi-core optical fiber and the core number of the core of the other multi-core optical fiber optically coupled to that core; (3) which region among the multiple regions obtained by dividing the cladding of the one multi-core optical fiber into multiple regions. The domain includes the mark of the one multi-core fiber, and which region of the multiple regions obtained by dividing the cladding of the other multi-core fiber into multiple regions contains the mark of the other multi-core fiber; (4) one or both of the overlap and offset between the mark of the one multi-core fiber and the mark of the other multi-core fiber; (5) one or both of the overlap and offset between the core of the one multi-core fiber and the core of the other multi-core fiber optically coupled to the core; and (6) the polarity of the two multi-core fibers.

9. The inspection method according to any one of claims 1 to 8, characterized in that, It also includes a centering process in which the two multi-core optical fibers are rotated and centered before the process of splicing the two multi-core optical fibers, so that the mark faces the light source side used in the post-splicing measurement process.

10. The inspection method according to any one of claims 1 to 9, characterized in that, The marking is a low refractive index marking with a refractive index lower than that of the cladding. The first shape and the second shape are trough shapes.

11. The inspection method according to any one of claims 1 to 9, characterized in that, The marking is a high refractive index marking with a refractive index higher than that of the cladding. The first shape and the second shape are wave crest shapes.

12. The inspection method according to any one of claims 1 to 9, characterized in that, The marking is a low-refractive-index marking surrounded by a high-refractive-index region with a higher refractive index than the cladding, and a low-refractive-index region with a lower refractive index than the cladding. The first shape and the second shape are serrated.

13. The inspection method according to any one of claims 1 to 9, characterized in that, The marking of one multi-core optical fiber is a low refractive index marking with a refractive index lower than that of the cladding, and the marking of the other multi-core optical fiber is a high refractive index marking with a refractive index higher than that of the cladding. The first shape is a trough shape, and the second shape is a crest shape.

14. An inspection method, characterized in that, include: The post-fusion splicing measurement process involves determining the position of the core or mark of one multi-core optical fiber based on the spatial distribution or directional dependence of the transmitted light intensity of the transmitted light intensity of the other multi-core optical fiber. The estimation process, based on one or both of the positions of the cores of the two multi-core optical fibers and the positions of the marks determined in the post-fusion splicing measurement process, estimates at least one of the following items (1) to (6): (1) the coupling efficiency or connection loss of the two multi-core optical fibers; (2) the correspondence between the core number of the core of one multi-core optical fiber and the core number of the core of the other multi-core optical fiber optically coupled to that core; (3) which of the multiple regions obtained by dividing the cladding of the one multi-core optical fiber contains The marking of the one multi-core optical fiber, and which region of the plurality of regions obtained by dividing the cladding of the other multi-core optical fiber into a plurality of regions contains the marking of the other multi-core optical fiber; (4) one or both of the overlap and offset between the marking of the one multi-core optical fiber and the marking of the other multi-core optical fiber; (5) one or both of the overlap and offset between the core of the one multi-core optical fiber and the core of the other multi-core optical fiber optically coupled to the core; and (6) the polarity of the two multi-core optical fibers.

15. An inspection system, characterized in that, It features: a single light source or multiple light sources; a single photodetector or multiple photodetectors; and a single control unit or multiple control units. The single control unit or at least one of the multiple control units performs a post-fusion splicing measurement process using the single light source or at least one of the multiple light sources and the single photodetector or at least one of the multiple photodetectors. In this post-fusion splicing measurement process, for two multi-core optical fibers with markings formed in the cladding and their end faces fused together, the position of the marking of the one multi-core optical fiber is determined according to the direction when a predetermined first shape appears in a curve representing the direction dependence of the transmitted light intensity of one of the two multi-core optical fibers, and the position of the marking of the other multi-core optical fiber is determined according to the direction when a predetermined second shape appears in a curve representing the direction dependence of the transmitted light intensity of the other multi-core optical fiber.

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