WO2024111122A1

WO2024111122A1 - Light branching rate adjustment method and light branching rate adjustment device

Info

Publication number: WO2024111122A1
Application number: PCT/JP2022/043611
Authority: WO
Inventors: 卓威植松; 一貴納戸; 裕之飯田; 和典片山
Original assignee: 日本電信電話株式会社
Priority date: 2022-11-25
Filing date: 2022-11-25
Publication date: 2024-05-30

Abstract

This light branching rate adjustment method includes: measuring the intensity of test light (80) having passed through an optical fiber (20) in a state where a polished surface (14) formed on a side surface (15) of an optical fiber (10) and a polished surface (24) formed on a side surface (25) of the optical fiber (20) are in contact with each other so as to be slidable; and moving one of the polished surface (14) and the polished surface (24) relative to the other such that the difference between the intensity of the test light (80) and a prescribed reference value is reduced.

Description

Optical branching ratio adjusting method and optical branching ratio adjusting device

This disclosure relates to an optical branching ratio adjustment method and an optical branching ratio adjustment device.

Optical fibers laid outdoors may be temporarily cut due to changes in the optical fiber route associated with various construction works such as road widening. However, cutting the optical fiber temporarily stops communication services, so there is a demand for technology that can branch the route of the optical fiber or merge it with another route without cutting the optical fiber. Non-patent documents 1 and 2 are related documents of this technology and discuss a side polishing method for optical fibers.

After constructing an optical fiber branch, the optical branching ratio of the optical fiber branch may change due to factors such as changes in the external environment. However, conventional technology was unable to detect changes in the optical branching ratio. Even if it was possible to detect changes in the optical branching ratio, it was also unable to restore the optical branching ratio to its original value.

This disclosure has been made in consideration of the above circumstances, and aims to provide an optical branching ratio adjustment method and optical branching ratio adjustment device that can return the optical branching ratio in an optical fiber branch to its original value even if the optical branching ratio changes.

A method for adjusting an optical branching ratio according to one aspect of the present disclosure includes measuring the intensity of test light passing through a second optical fiber while a first polished surface formed on a side of a first optical fiber and a second polished surface formed on a side of a second optical fiber are in slidable contact with each other, and moving one of the first polished surface and the second polished surface relative to the other so that the difference between the intensity and a predetermined reference value is reduced.

An optical branching rate adjustment device according to one aspect of the present disclosure includes a first holding part that holds the first optical fiber and a second holding part that holds the second optical fiber, with a first polished surface formed on the side of the first optical fiber and a second polished surface formed on the side of the second optical fiber in slidable contact with each other, a light source that generates test light that is incident on the second optical fiber, a light intensity measurement part that includes a light receiving part that measures the intensity of the test light that has passed through the second optical fiber, and a position adjustment part that moves one of the first holding part and the second holding part relative to the other so that the difference between the intensity and a predetermined reference value is reduced.

According to the present disclosure, it is possible to provide an optical branching ratio adjustment method and an optical branching ratio adjustment device that can return the optical branching ratio to its original value even if the optical branching ratio in an optical fiber branch changes.

FIG. 1 is a cross-sectional view illustrating an example optical fiber branch according to an embodiment of the present disclosure. FIG. 2A is a perspective view showing an example of a polishing apparatus. FIG. 2B is a cross-sectional view of the holding portion shown in FIG. 2A. FIG. 3A is a block diagram showing an example of the configuration of an optical branching ratio adjusting device according to this embodiment. FIG. 3B is a block diagram showing the configuration of the control unit shown in FIG. 3A. FIG. 3C is a perspective view showing an example of the configuration of the optical branching ratio adjustment device according to the present embodiment. FIG. 4 is a flowchart illustrating an example of a process of an optical branching ratio adjustment method according to an embodiment of the present disclosure. FIG. 5 is a cross-sectional view showing two polishing surfaces and their surroundings according to this embodiment. FIG. 6 is a perspective view showing the configuration of a light branching ratio adjustment device according to a modified example of this embodiment.

Below, an optical branching ratio adjustment method and an optical branching ratio adjustment device according to an embodiment of the present disclosure will be described. Note that common parts in each figure are given the same reference numerals, and duplicated explanations will be omitted.

For ease of explanation, optical fibers that have already been installed in a network are sometimes called current optical fibers. Current optical fibers are installed in facilities that build a network, such as utility tunnels and overhead lines. They may be installed either indoors or outdoors. Current optical fibers may already be used for optical communications in the network, or may be installed and unused. Optical fibers that are newly connected to current optical fibers are sometimes called branch fibers. Branch fibers are optical fibers that branch off from a route (transmission route) built by the current optical fiber, or that build a route that merges into that route.

For ease of explanation, the X, Y, and Z directions are defined as being orthogonal to each other. The X and Z directions are the directions in which one of the two

holding parts

41, 42 according to this embodiment moves relative to the other. The Y direction is the arrangement direction of the two

holding parts

41, 42. The Z direction is also the extension direction of the two

optical fibers

10, 20 and the extension direction of the V-groove 34 formed in each holding part 41 (42).

First, the optical fiber branch 1 according to this embodiment will be described. The optical fiber branch 1 is a so-called optical fiber coupler that branches light propagating through one optical fiber into two optical fibers, or merges light propagating through two optical fibers into one optical fiber. FIG. 1 is a cross-sectional view of the optical fiber branch 1. As shown in FIG. 1, the optical fiber branch 1 includes an optical fiber (first optical fiber) 10 and an optical fiber (second optical fiber) 20. The cross-sectional view shown in FIG. 1 includes the central axis 10a of the optical fiber 10 and the central axis 20a of the optical fiber 20.

The optical fiber 10 is, for example, the above-mentioned currently used optical fiber, and has already been laid in a network (not shown). The optical fiber 10 has a core (first core) 11, a cladding (first cladding) 12, and a coating (first coating) 13. The optical fiber 10 is a single-mode optical fiber or a multimode optical fiber.

The optical fiber 20 is, for example, the branch fiber described above, and is newly connected to the optical fiber 10 as an additional path of a network (not shown). The optical fiber 20 has a core (second core) 21, a cladding (second cladding) 22, and a coating (second coating) 23. The optical fiber 20 is also a single-mode optical fiber or a multimode optical fiber.

The optical fiber 10 has a polished surface (first polished surface) 14 on a side surface 15. The polished surface 14 is formed by polishing the side surface 15. This polishing process can be performed, for example, by a polishing device 30 (see FIGS. 2A and 2B ) described below. By this polishing process, the coating 13 is removed from the polished surface 14, and a part of the cladding 12 remains. Here, the minimum thickness of the cladding 12 from the polished surface 14 to the core 11 is defined as the remaining cladding thickness (first remaining cladding thickness) d _lv (see FIG. 5 ).

Like the optical fiber 10, the optical fiber 20 has a polished surface (second polished surface) 24 on a side surface 25. The polished surface 24 is formed by polishing the side surface 25. This polishing process can also be performed by, for example, a polishing device 30 described below. By this polishing process, the coating 23 is removed from the polished surface 24, and a part of the cladding 22 remains. Here, the minimum value of the thickness of the cladding 22 from the polished surface 24 to the core 21 is defined as the remaining cladding thickness (second remaining cladding thickness) d _br .

The optical fiber 10 extends in the Z direction while being bent with a radius of curvature (first radius of curvature) R _lv at least in a portion including the polished surface 14. The polished surface 14 is formed by polishing a side surface 15 of the optical fiber 10 placed in a state in which the optical fiber 10 is bent with the radius of curvature R _lv . Therefore, when the optical fiber 10 is bent with the radius of curvature R _lv , the polished surface 14 forms an elliptical plane extending in the longitudinal direction of the optical fiber 10.

The optical fiber 20 extends in the Z direction while being bent with a radius of curvature (second radius of curvature) R _br at least in a portion including the polished surface 24. The polished surface 24 is formed by polishing a side surface 25 of the optical fiber 20 placed in a state in which the optical fiber 20 is bent with the radius of curvature R _br . Therefore, when the optical fiber 20 is bent with the radius of curvature R _br , the polished surface 24 forms an elliptical plane extending in the longitudinal direction of the optical fiber 20.

In addition, a refractive index matching agent (not shown) is interposed between polished surface 14 and polished surface 24. The refractive index matching agent may be a viscous liquid or a deformable solid. The refractive index of the refractive index matching agent is smaller than the refractive indexes of cladding 12 and cladding 22. This prevents an increase in insertion loss.

The polished surface 14 and the polished surface 24 are in contact with each other via a refractive index matching material (not shown). Therefore, the cores 11 and 21 are positioned with a core distance d (see FIG. 5 ). The core distance d is the distance between the cores 11 and 21, and its minimum value is the sum of the remaining cladding thickness d _lv of the cladding 12, the remaining cladding thickness d _br of the cladding 22, and the thickness of the refractive index matching material (not shown).

By making the core spacing d sufficiently small, evanescent coupling between core 11 and core 21 is obtained. That is, core 11 and core 21 are optically coupled, enabling the multiplexing or demultiplexing of light, which is the function of optical fiber branch 1. Note that the coupling efficiency between core 11 and core 21 depends on the core spacing d. Furthermore, the core spacing d at which 100% coupling efficiency is obtained depends on the wavelength of light. For example, when the wavelength of light is 1260 nm, the core spacing d at which 100% coupling efficiency is obtained is 2.6 μm or less.

Next, a method for forming the polishing surface 14 (24) will be described. FIG. 2A is a perspective view showing an example of a polishing device 30 used to form the polishing surface 14 (24). FIG. 2B is a cross-sectional view of the holding part 32 shown in FIG. 2A. As shown in FIG. 2A, the polishing device 30 includes a polishing table 31 and a holding part 32. Below, the formation of the polishing surface 14 will be described as an example.

The polishing table 31 has a flat upper surface 31a, on which a polishing sheet 33 is placed. The holding part 32 has a flat surface 32a facing the upper surface 31a of the polishing table 31, and a V-shaped groove 34 curved with a radius R is formed on the flat surface 32a. The radius R is slightly smaller than the radius of curvature _Rlv . The material of the polishing table 31 and the holding part 32 is, for example, glass.

As shown in Fig. 2A, the V-groove 34 is formed so that its depth from the plane 32a is shallowest near the center of the plane 32a. Also, as shown in Fig. 2B, the minimum depth of the V-groove 34 is set to a value that allows the cladding 12 to have a remaining cladding thickness d _lv .

The polishing process of the optical fiber 10 using the polishing device 30 is performed at the site where the optical fiber 20 is connected to the optical fiber 10. First, as a preparation step before polishing, a state is prepared for measuring the leaked light from the optical fiber 10. Specifically, the optical fiber 10 is bent while laser light (for convenience, referred to as propagating light) is propagating through the optical fiber 10, and the intensity of the laser light (for convenience, referred to as leaked light) leaking from the bent portion is measured with a light intensity meter (not shown).

As described above, the optical fiber 10 is an optical fiber in use. Therefore, the light propagating through the optical fiber 10 is either communication light 81 propagating through the network or pseudo communication light introduced using a specified light source. In either case, a bend that causes a loss that does not affect communication is imparted to the optical fiber 10, and the intensity of the leaked light from the bent portion is measured until polishing is completed.

Next, adhesive 35 (see FIG. 5) is filled into the V-groove 34 of the holding portion 32, and the optical fiber 10 is fixed in the V-groove 34. When the adhesive 35 hardens and the optical fiber 10 is fixed in the V-groove 34, a part of the side surface 15 of the optical fiber 10 is exposed from the flat surface 32a of the holding portion 32 (see FIG. 2B).

Next, with a portion of the side surface 15 exposed from the flat surface 32a of the holding portion 32, the flat surface 32a of the holding portion 32 is opposed to the polishing sheet 33 placed on the polishing table 31. After that, the side surface 15 of the optical fiber 10 exposed from the flat surface 32a of the holding portion 32 is pressed against the polishing sheet 33 and polished.

The polishing of the side surface 15 is performed while monitoring the intensity of the leaking communication light 81. As the polishing progresses, the polished surface approaches the core 11 (i.e., the remaining cladding thickness d _lv decreases), and the intensity of the leaked light being measured gradually decreases. Then, when the intensity of the leaked light reaches a predetermined value, the polishing is stopped and the bend is released. Through this series of steps, the formation of the polished surface 14 is completed.

The polished surface 24 of the optical fiber 20 having the remaining cladding thickness d _br is also formed through the same process as described above. However, the polished surface 24 is formed using a holding part 32 in which a V-groove 34 having a radius R slightly smaller than the radius of curvature R _br is formed. The polished surface 24 may be formed in advance at a remote location such as a factory. In this case, more precise processing is possible than on-site processing.

Next, the optical branching rate adjustment device 40 according to this embodiment will be described. For ease of explanation, the optical branching rate adjustment device 40 will be simply referred to as the adjustment device 40.

FIG. 3A is a block diagram showing an example of the configuration of the adjustment device 40 according to this embodiment. FIG. 3B is a block diagram showing the configuration of the control unit 50 shown in FIG. 3A. FIG. 3C is a perspective view showing an example of the configuration of the adjustment device 40. As shown in FIG. 3A, the adjustment device 40 includes a holding unit (first holding unit) 41, a holding unit (second holding unit) 42, a light source 43, a light intensity measuring unit 44, and a position adjustment unit (position adjustment device) 45.

3C , the holding portion 41 is the same as the holding portion 32 that holds the optical fiber 10. Similarly, the holding portion 42 is the same as the holding portion 32 that holds the optical fiber 20. That is, the holding portion 41 is the holding portion 32 in which the V groove 34 having a radius R slightly smaller than the radius of curvature _Rlv is formed, and the holding portion 42 is the holding portion 32 in which the V groove 34 having a radius R slightly smaller than the radius of curvature _Rbr is formed.

The holding part 41 holds the optical fiber 10 after the above-mentioned polishing process has been completed. That is, the holding part 41 holds the optical fiber 10 with the polished surface 14 exposed on the plane 41a. The plane 41a is parallel to the XZ plane. Similarly, the holding part 42 holds the optical fiber 10 with the polished surface 24 exposed on the plane 42a. The plane 42a is also parallel to the XZ plane. The holding part 41 and the holding part 42 hold the corresponding optical fiber with the polished surface 14 and the polished surface 24 in slidable contact with each other. In other words, the holding part 41 and the holding part 42 are lined up in the Y direction with their

respective planes

41a, 42a in slidable contact with each other. For example, when the Y direction is parallel to the direction of gravity, the holding part 41 is stacked on the holding part 42.

The light source 43 is a laser light source having a known configuration, and generates test light 80 to be incident on the optical fiber 20. The test light 80 may be incident on either end of the optical fiber 20. For example, if the optical fiber 10 is an active optical fiber, the light source 43 is connected to the end of the optical fiber 20 (i.e., the branch fiber) located on the opposite side of the optical fiber branch 1 from the optical network unit (ONU) on the telecommunications carrier side that connects to the optical fiber 10. As shown by the dotted line in Figure 3A, the light source 43 may be controlled by the control unit 50.

Also, the optical line terminal on the subscriber side may be used as the light source 43. The optical line terminal is usually installed indoors and operates by receiving power from a commercial power source. When this optical line terminal is used as the light source 43, there is no need to prepare a separate dedicated light source. In other words, the optical branching rate adjustment device 40 can be made smaller.

The light intensity measuring unit 44 is a so-called light intensity meter, and includes a light receiving unit 46 that receives the test light 80 that has passed through the optical fiber 20. The light intensity measuring unit 44 measures (calculates) the intensity of the test light 80 received by the light receiving unit 46, and outputs the measurement result to the control unit 50.

The light receiving unit 46 may be configured with a photoelectric conversion element that converts the test light 80 into electricity. In this case, the light intensity measurement unit 44 includes a power storage unit 47 such as a supercapacitor, and the power storage unit 47 stores the power output from the light receiving unit 46. Furthermore, the light intensity measurement unit 44 supplies the power stored in the power storage unit 47 to the position adjustment unit 45. This power supply makes it possible to operate the position adjustment unit 45 without receiving power from a commercial power source, and the adjustment device 40 can be installed in an environment where it is difficult to supply power, such as outdoors.

The position adjustment unit 45 includes an operation unit 48 and a control unit 50 that controls the operation unit 48. The position adjustment unit 45 moves one of the holding unit 41 (i.e., the polished surface 14) and the holding unit 42 (i.e., the polished surface 24) relative to _the other so that the difference between the intensity of the test light 80 and a predetermined reference value P _{rf decreases. Here, the predetermined reference value P rf} is the intensity of the test light 80 measured by the light intensity measurement unit 44 when the optical branching ratio set in the optical fiber branch 1 is obtained.

The operation unit 48 operates the position of the holding unit 41 or the holding unit 42. For example, as shown in FIG. 3C, the operation unit 48 includes a linear actuator 58 and a stage 59 operated by the linear actuator 58. The linear actuator 58 is composed of, for example, a motor and a micrometer head, and moves the stage 59 along the X direction under the control of the control unit 50.

The upper surface 59a of the stage 59 is parallel to the XZ plane. The holding part 41 or the holding part 42 is placed on this upper surface 59a. For example, as shown in FIG. 3C, the holding part 42 is placed on the stage 59 and fixed to the stage 59 using a holding means such as a clamp (not shown) or an adhesive. In this case, the holding part 41 is placed on the holding part 42. However, the movement of the holding part 41 in all directions is restricted by a stopper (not shown).

The control unit 50 is, for example, a general-purpose computer as shown in FIG. 3B. The computer serving as the control unit 50 comprises a CPU (Central Processing Unit, processor) 51, memory 52, storage 53 (HDD: Hard Disk Drive, SSD: Solid State Drive), a communication unit 54, an input unit 55, and an output unit 56. The memory 52 and storage 53 are storage devices. In this computer, the CPU 51 executes a specific program loaded onto the memory 52, thereby realizing the various functions of the adjustment device 40, such as measuring the intensity of the test light 80 and controlling the operation unit 48.

The programs executed by the control unit 50 may be stored in a computer-readable recording medium such as a Universal Serial Bus (USB) memory, a Compact Disc (CD), or a Digital Versatile Disc (DVD), and may be distributed to the control unit 50 via a network. The computer-readable recording medium is, for example, a non-transitory recording medium.

When the object of operation of the position adjustment unit 45 is the holding unit 42, the storage 53 stores the relative position of the holding unit 42 (i.e., the polishing surface 24) with respect to the holding unit 41 (i.e., the polishing surface 14) when a predetermined reference value P _rf of the test light 80 is obtained by constructing the optical fiber branch 1. The storage 53 also stores the tendency of change (increase or decrease) in the test light 80 when the holding unit 42 is moved along the X direction based on the relative position (for example, a set of the coordinates of the holding unit 42 and the intensity P _th of the test light 80). The above-mentioned information stored in the storage 53 is the same when the object of operation of the position adjustment unit 45 is the holding unit 41.

These relative positions are used as information for the control unit 50 to determine in which direction and by how much the operation target should be moved along the X direction when the intensity _Pth of the test light 80 measured by the light intensity measuring unit 44 is less than the reference value _Prf or exceeds the reference value _Prf .

Next, a method for adjusting the optical branching ratio by the adjustment device 40 will be described.
Fig. 4 is a flow chart showing an example of a process of the optical branching ratio adjusting method according to the present embodiment. Fig. 5 is a cross-sectional view showing the polished surface 14, the polished surface 24 and their surroundings.

The following describes an example in which the object of operation of the position adjustment unit 45 is the holding unit 42. Therefore, the holding unit 42 is placed on the stage 59, and the holding unit 41 is placed on the holding unit 42. The holding unit 42 moves in the X direction by operating the stage 59 with the operation unit 48. Meanwhile, the movement of the holding unit 41 is restricted by a stopper (not shown). In other words, the holding unit 41 is stationary.

When evaluating the optical branching ratio of the optical fiber branch 1, communication light 81 (see FIG. 3C) may or may not be propagating through the optical fiber 10. Meanwhile, test light 80 having a preset intensity P _in is input to the optical fiber 20. The test light 80 propagates through the optical fiber 20 and is input to the light receiving unit 46 of the light intensity measuring unit 44. The light intensity measuring unit 44 measures the intensity P _th of the test light 80 input to the light receiving unit 46, and outputs the intensity P _th to the control unit 50. The optical branching ratio can be estimated from the results of using a formula expressed as 1-(P _th /P _in ).

First, the control unit 50 compares the intensity _Pth of the test light 80 measured by the light intensity measurement unit 44 with a predetermined reference value _Prf (step S1). If the intensity _Pth is equal to the reference value _Prf (YES in step S1), it is determined that the desired light branching ratio is maintained, and the process ends.

On the other hand, if the intensity _Pth is different from the reference value _Prf even when the measurement error is taken into consideration (NO in step S1), the control unit 50 judges whether the intensity _Pth is greater than the reference value _Prf (step S2). In this case, the control unit 50 may judge whether the intensity _Pth is smaller than the reference value _Prf .

If the intensity _Pth is greater than the reference value _Prf (YES in step S2), the optical branching ratio has decreased from the initial value. In other words, the core spacing d (see FIG. 5) has increased from the initial value. Therefore, the control unit 50 controls the position adjustment unit 45 so that the core spacing d decreases (step S4). Specifically, the position adjustment unit 45 moves the holding unit 42 (i.e., the polishing surface 24) closer to the holding unit 41 (i.e., the polishing surface 14).

While the position adjustment unit 45 is adjusting the position of the holding unit 42, the control unit 50 compares the intensity _Pth with the reference value _Prf (step S5). If the intensity _Pth is equal to the reference value _Prf (YES in step S5), the control unit 50 stops the control of the position adjustment unit 45 (i.e., the position adjustment of the holding unit 42) and ends the process. On the other hand, if the intensity _Pth has not reached the reference value _Prf (NO in step S5), the control unit 50 continues to control the position adjustment unit 45 to reduce the core interval d (step S6). After that, the process returns to step S5, and the processes of steps S5 and S6 are repeated until the intensity _Pth reaches the reference value _Prf .

On the other hand, if the intensity _Pth is smaller than the reference value _Prf (NO in step S2), the optical branching ratio has increased from the initial value. In other words, the core spacing d has decreased from the initial value. Therefore, the control unit 50 controls the position adjustment unit 45 so as to increase the core spacing d (step S3). That is, the position adjustment unit 45 moves the holding unit 42 (i.e., the polishing surface 24) away from the holding unit 41 (i.e., the polishing surface 14).

While the position adjustment unit 45 is adjusting the position of the holding unit 42, the control unit 50 compares the intensity _Pth with the reference value _Prf (step S5). If the intensity _Pth is equal to the reference value _Prf (YES in step S5), the control unit 50 stops the control of the position adjustment unit 45 (i.e., the position adjustment of the holding unit 42) and ends the process. On the other hand, if the intensity _Pth has not reached the reference value _Prf (NO in step S5), the control unit 50 continues to control the position adjustment unit 45 to increase the core interval d (step S6). After that, the process returns to step S5, and the processes of steps S5 and S6 are repeated until the intensity _Pth reaches the reference value _Prf .

By periodically repeating this series of processes, even if the optical branching ratio in optical fiber branch 1 changes, the optical branching ratio can be restored to its original value.

Next, a modification of this embodiment will be described.
6 is a perspective view showing the configuration of a light branching rate adjustment device according to a modified example of this embodiment. As shown in FIG. 6, the operation unit 48 of the position adjustment unit 45 may further include a linear actuator 60 and a stage 61 operated by the linear actuator 60. The linear actuator 60 is, for example, composed of a motor and a micrometer head, and moves the stage 61 along the Z direction under the control of the control unit 50. In other words, the operation unit 48 according to the modified example includes a two-axis stage capable of moving the holding unit 41 or the holding unit 42 in the X direction and the Z direction. Hereinafter, a case where the operation target of the position adjustment unit 45 is the holding unit 42 will be described as an example.

Changes in the optical branching ratio in optical fiber branch 1 occur both when there is a relative axial misalignment between core 11 and core 21 along the X direction, and when there is a relative axial misalignment between core 11 and core 21 along the Z direction. However, as shown in Non-Patent Document 2, changes in the optical branching ratio are more dependent on the relative axial misalignment along the X direction than on the relative axial misalignment along the Z direction. In other words, the optical branching ratio changes more rapidly with an axial misalignment along the X direction than with an axial misalignment along the Z direction. Therefore, although it depends on the movement resolution of the operation unit 48, it may be difficult to fine-tune the optical branching ratio by simply adjusting the position of the holding unit 42 along the X direction.

Therefore, focusing on the fact that the change in the optical branching ratio due to the axial misalignment along the Z direction is gradual, in this modified example, the position adjustment of the holding part 42 by the linear actuator 58 is regarded as a rough adjustment, and the position adjustment of the holding part 42 by the linear actuator 60 is regarded as a fine adjustment, and these adjustments are used in combination. For example, the position adjustment of the holding part 42 along the X direction is performed using the linear actuator 58, and the intensity _Pth is brought closer to the reference value _Prf . Then, the position adjustment of the holding part 42 along the Z direction is performed using the linear actuator 60 until the intensity _Pth reaches the reference value _Prf . By performing such an operation, even if the movement resolution of the

linear actuators

58, 60 and the

stages

59, 61 is relatively large, the intensity _Pth can be matched to the reference value _Prf with high accuracy. That is, high-precision adjustment until a desired optical branching ratio is obtained is possible.

In order to use the linear actuator 58 and the linear actuator 60 in combination, the storage 53 stores a tendency of change (increase or decrease) in the test light 80 when the holder 42 is moved along the Z direction based on the relative position of the holder 42 (i.e., the polishing surface 24) with respect to the holder 41 (i.e., the polishing surface 14) (for example, a set of the coordinates of the holder 42 and the intensity _Pth of the test light 80). The above-mentioned information stored in the storage 53 is also the same when the object to be operated by the position adjustment unit 45 is the holder 41.

These relative positions are used as information by the control unit 50 to determine in which direction and by how much the object to be operated (i.e., the holding unit 41 or the holding unit 42) should be moved along the Z direction when the intensity _Pth of the test light 80 measured by the light intensity measuring unit 44 is less than _the reference value _Prf or exceeds the reference value Prf.

Note that this disclosure is not limited to the above-described embodiments, but is set forth in the claims, and includes all modifications within the meaning and scope equivalent to the claims.

1 Optical fiber branch 10 Optical fiber (first optical fiber)
11 core (first core)
12 Clad (first clad)
13 Coating (first coating)
14 Polishing surface (first polishing surface)
15 Side surface 20 Optical fiber (second optical fiber)
21 core (second core)
22 Clad (second clad)
23 Coating (second coating)
24 Polishing surface (second polishing surface)
25 Side surface 30 Polishing device 32 Holding portion 34 V-groove 35 Adhesive 40 Optical branching rate adjustment device (adjustment device)
41 Holding portion (first holding portion)
42 holding portion (second holding portion)
43 Light source 44 Light intensity measuring unit 45 Position adjustment unit (position adjustment device)
46 Light receiving unit 47 Power storage unit 48 Operation unit 50 Control unit 58 Linear actuator 59 Stage 60 Linear actuator 61 Stage

Claims

measuring an intensity of a test light passing through the second optical fiber while a first polished surface formed on a side surface of the first optical fiber and a second polished surface formed on a side surface of the second optical fiber are in slidable contact with each other;
A method for adjusting a light branching ratio, comprising moving one of the first polishing surface and the second polishing surface relative to the other so that a difference between the intensity and a predetermined reference value is reduced.
converting the test light passing through the second optical fiber into electrical power;
The method for adjusting a light branching ratio according to claim 1 , wherein the power is supplied to a position adjustment device that moves the one of the first polishing surface and the second polishing surface.
3. The method for adjusting an optical branching ratio according to claim 1, wherein the test light is generated by an optical line terminal connected to the second optical fiber.
a first holding part that holds the first optical fiber and a second holding part that holds the second optical fiber in a state in which a first polished surface formed on a side surface of the first optical fiber and a second polished surface formed on a side surface of the second optical fiber are in slidable contact with each other;
a light source that generates test light that is incident on the second optical fiber;
a light intensity measuring unit including a light receiving unit that receives the test light that has passed through the second optical fiber and measures the intensity of the test light;
a position adjustment unit that moves one of the first holding unit and the second holding unit relative to the other so that a difference between the intensity and a predetermined reference value is reduced.
the light receiving unit is a photoelectric conversion element that converts the test light that has passed through the second optical fiber into electric power,
The optical branching ratio adjusting device according to claim 4 , wherein the position adjusting section is operated by power generated by the light receiving section.