Optical coupling unit and optical switch

Abstract

The purpose of the present disclosure is to provide an optical coupling unit and an optical switch, which realize stable optical characteristics with respect to external factors with low power consumption and in a more economical manner. An optical coupling unit according to the present disclosure couples optical fibers of a single core disposed in two ferrules by using a sleeve in order to achieve the abovementioned purpose. In a first ferrule of the two ferrules, a plurality of optical fibers are disposed in a bundle shape, in a fiber hole, on the same circumference centered about the ferrule center axis. At least one of the two ferrules is rotatable about the ferrule center axis. The rotation of at least the other of the two ferrules is regulated. One of the two ferrules is pressed in the direction in which end parts of the two ferrules butt to each other.

Description

Optical coupling section and optical switch

[0001] The present invention relates to an optical coupling unit used mainly for switching the path of an optical line using a single-mode optical fiber in an optical fiber network, and an optical switch using the same.

[0002] Various methods have been proposed for all-optical switches that switch the path of light while keeping it as it is, as shown in, for example, Non-Patent Document 1. Among these, optical fiber mechanical optical switches, which control the butting of optical fibers or optical connectors using a robot arm or motor, are inferior to other methods in terms of slow switching speed, but have many advantages over other methods, such as low loss, low wavelength dependency, multi-port capability, and a self-holding function that maintains the switched state even when power is lost. Typical structures include a method that translates a stage using an optical fiber V-groove, a method that translates or changes the angle of a mirror or prism to selectively couple to multiple optical fibers output from an input optical fiber, and a method that uses a robot arm to connect a jumper cable with an optical connector.

[0003] Also, a method has been proposed in which a multicore fiber is used as the optical path to be switched. For example, by combining a multicore fiber with a three-dimensional MEMS optical switch (see, for example, Non-Patent Document 2), it becomes possible to switch multiple paths simultaneously. Also, by performing switching by rotating a cylindrical ferrule into which a multicore fiber is inserted (see, for example, Patent Document 1), optical components such as lenses and prisms are not required, and the configuration can be simplified.

[0004] Japanese Patent Application Publication No. 2-82212

[0005] M. Stepanovsky, “A Comparative Review of MEMS-Based Optical Cross-Connects for All-Optical Networks From the Past to the Present Day,” IEEE Communications Surveys & Tutorials, vol. 21, no. 3, pp. 2928-2946, 2019. K. Hiruma, T. Sugawara, K. Tanaka, E. Nomoto, and Y. Lee, “Proposal of High-capacity and High-reliability Optical Switch Equipmet with Multi-core Fibers,” 18th OptoElectronics and Communications Conference held jointly with 2013 International Conference on Photonics in Switching (OECC / PS), ThT1-2, 2013. B. Jian, "The Non-Contact Connector: A New Category of Optical Fiber Connector," 2015 Optical Fiber Communications Conference and Exhibition (OFC), W2A. 1, 2015. Hajime Arao, Yoshitaka Yagabe, Fumiya Uehara, Dai Sasaki, and Takayuki Shimazu, "FlexAirConnect T: A Dust-Resistant Optical Multifiber Connector Featuring Low Loss and Low Mating Force," SEI Technical Review, No. 193, pp. 26-31, July 2018. Chisato Fukai, Yoshiteru Abe, and Kazunori Katayama, “Multi-Fiber Cylindrical Ferrule for Remote Rotary Optical Fiber Switching,” 2022 Optical Fiber Communications Conference and Exhibition (OFC), Th2A. 11, 2022.

[0006] However, the prior art described in the aforementioned Non-Patent Document 1 has problems in that it is difficult to further reduce power consumption, miniaturize, and improve cost-effectiveness. Specifically, the method of translating the aforementioned optical fiber V-groove stage or prism generally uses a motor as a drive source. However, because the mechanism linearly moves a heavy object such as a stage, the motor requires a certain amount of torque, and power consumption is required to obtain an appropriate output to maintain the required torque. Furthermore, since optical axis alignment using a single-mode optical fiber requires an accuracy of approximately 1 μm or less, a mechanism (typically a ball screw) that converts the motor's rotational motion into linear motion must convert it into linear motion in sub-μm steps. Considering that the optical fiber pitch of a typically used output optical fiber array is approximately 125 μm in cladding outer diameter or 250 μm in coating outer diameter, the larger the output optical fiber array, the longer the actual motor drive time, resulting in increased power consumption. For this reason, such optical fiber-type mechanical optical switches generally require a power of several hundred mW or more. Furthermore, the robot arm method using an optical connector has the problem that the robot arm itself, which controls the insertion and removal of the optical connector or ferrule, requires a large amount of power of several tens of watts or more.

[0007] Furthermore, in the optical path switching using a multicore fiber described in Non-Patent Document 2, the process of manufacturing the optical switch requires a collimating mechanism for coupling to the optical fiber array on the output side and a vibration isolation mechanism for obtaining stable optical characteristics against external factors such as vibration, which makes the assembly process complicated.

[0008] In the optical path switching using a cylindrical ferrule into which a multicore fiber is inserted, as described in Patent Document 1, the ferrule is tightly inserted into a sleeve to align the central axis, and there is a problem that a large amount of energy and power is required to drive the rotation due to the friction between the ferrule and the sleeve. Furthermore, in order to prevent the opposing fiber end faces from being scratched when the ferrule rotates, which would deteriorate optical characteristics such as connection loss, a mechanism is required to separate the ferrule end faces every time the ferrule rotates, which poses a problem of requiring extra energy to drive the rotation.

[0009] On the other hand, there is a method to prevent scratches on the fiber end face due to contact by providing a gap in advance in a cylindrical ferrule into which an optical fiber is inserted so that the fibers do not come into contact (for example, Non-Patent Document 3). However, in order to suppress signal degradation due to reflection caused by an air layer that is created between the fiber end faces due to the gap, a special coating to prevent reflection is required, which poses a problem of increased costs.

[0010] Another method for preventing reflection is to polish the ferrule end face at an angle (see, for example, Non-Patent Document 4). However, with a ferrule polished at an angle, there are problems such as interference between the ferrule end faces when switching by rotation, or a large gap being required, resulting in high connection loss.

[0011] In addition, in the optical path switching using a cylindrical ferrule into which multiple fibers are inserted, as described in Non-Patent Document 5, the ferrule is polished to a spherical surface, the fiber end faces are polished at an angle, and the center of the ferrule is polished flat, minimizing gaps on the fiber end faces. This makes it possible to prevent scratches on the fiber end faces due to contact, while preventing reflection and minimizing connection loss due to gaps. However, during the manufacturing process of the ferrule mold, it is difficult to control the fiber hole position with high precision, resulting in excessive axial misalignment loss due to misalignment of the fiber hole. Furthermore, it is difficult to position the fiber hole close to the center of the ferrule end face, and the fiber hole is far from the center of the ferrule end face, resulting in large rotational angle misalignment loss during switching.

[0012] In order to solve the above problems, an object of the present invention is to provide an optical coupling section and an optical switch that can realize stable optical characteristics against external factors with low power consumption and more economically.

[0013] The optical coupling unit according to the present disclosure is an optical coupling unit that couples single-core optical fibers arranged in two ferrules using a sleeve, wherein a first of the two ferrules has a fiber hole in which a plurality of optical fibers are arranged in a bundle on the same circumference centered on the ferrule central axis, at least one of the two ferrules is rotatable around the ferrule central axis, and the butted ends of the two ferrules have a convex spherical shape with a center point on the ferrule central axis.

[0014] The optical coupling unit and optical switch of the present disclosure may include two ferrules in which a single-core single-mode optical fiber is arranged parallel to the central axis of the ferrule and at the same distance from the central axis of the ferrule. In this case, the butted ends of the two ferrules have a convex spherical shape, and the tips of the ends of the two ferrules are butted together so that their central axes coincide, and one of the ferrules is rotated.

[0015] More specifically, the optical coupling unit according to the present disclosure comprises: a first ferrule having a convex spherical end face, in which the core centers of a plurality of single-core single-mode optical fibers are arranged in a bundle shape at the center in the ferrule cross section so that they are aligned on the same circumference; a second ferrule having a convex spherical end face, in which the core centers of one or more single-core single-mode optical fibers are arranged on a circumference of the same diameter as the circumference on which the core centers of the single-mode optical fibers in the first ferrule are arranged from the center in the ferrule cross section; and a cylindrical sleeve having a hollow portion into which the first ferrule and the second ferrule are inserted so that the central axes of the first ferrule and the second ferrule are aligned, and a predetermined gap is provided between the outer diameter of each of the first ferrule and the second ferrule and the inner diameter of the hollow portion so that the first ferrule and the second ferrule can rotate.

[0016] In this invention, the ends of two ferrules, each having a convex spherical shape, have single-mode optical fibers arranged parallel to the ferrule central axis and at the same distance from the ferrule central axis. By butting the tips of the two ferrule ends together so that their central axes coincide and rotating them around the central axis of one of the ferrules, the end faces of the opposing optical fibers do not come into contact with each other, preventing deterioration of optical characteristics such as connection loss due to scratches on the end faces of the optical fibers caused by contact. Furthermore, because the end faces of the opposing optical fibers are non-parallel to each other, the amount of light reflection can be reduced, eliminating the need for a reflective coating and providing a more economical optical coupling unit and optical switch.

[0017] Furthermore, the present invention uses an axially rotatable mechanism on either the input or output side of the optical coupling section that performs optical switching, thereby minimizing the energy required by the actuator, i.e., torque output, and enabling low power consumption. Furthermore, the amount of optical axis misalignment in directions other than the axial rotation of the input ferrule is compensated for by the sleeve in the optical coupling section, enabling low loss. In addition, the present invention does not require a collimator or special vibration isolation mechanism, and instead is composed of commonly used optical connection components such as ferrules and sleeves, making it compact and economical.

[0018] Here, a dummy fiber may be arranged inside the plurality of optical fibers arranged in a bundle on the same circumference centered on the central axis of the ferrule, and the end face of the dummy fiber may form part of the convex spherical shape.

[0019] Furthermore, the return loss of the convex spherical shape may be equal to or greater than a predetermined value. For example, in the optical coupling unit according to the present disclosure, the angle between a cross section perpendicular to the central axis of the ferrule and an end face of the single-mode optical fiber may be equal to or greater than 4.5 degrees in each of the first and second ferrules. This allows the return loss of the convex spherical shape to be equal to or greater than 40 dB.

[0020] In addition, the excess loss T due to the gap between the end faces of the two ferrules is Ｇ For example, in the optical coupling unit according to the present disclosure, a gap between an end face of the single-mode optical fiber of the first ferrule and an end face of the single-mode optical fiber of the second ferrule, the optical axis of which is aligned with that of the single-mode optical fiber, may be 22 μm or less. Ｇ can be suppressed to 0.1 dB or less.

[0021] In addition, the excess loss T due to the rotation angle misalignment of the two ferrules ＲFor example, in the optical coupling unit according to the present disclosure, the distance from the central axis of the ferrule to the core center of each of the single-mode optical fibers in the first ferrule and the second ferrule may be 250 μm or less. Ｒ can be reduced to 0.1 dB or less.

[0022] The return loss in the convex spherical shape and the excess loss T due to the gap between the butted end faces of the two ferrules Ｇ For example, in the optical coupling unit according to the present disclosure, the plurality of optical fibers may be single-mode optical fibers, and the radius of curvature of the convex spherical shape in each of the first ferrule and the second ferrule may be 0.7 mm or more and 3.2 mm or less.

[0023] Specifically, the optical switch according to the present disclosure includes: the optical coupling unit; and a rotation mechanism that rotates one of the two ferrules of the optical coupling unit around the central axis of the ferrule.

[0024] For example, the optical switch according to the present disclosure may further include an actuator that rotates the rotation mechanism at a constant angular step and stops it at any angular step, and a bearing that constitutes the rotation mechanism.

[0025] Furthermore, the optical coupling unit according to the present disclosure is an optical coupling unit that couples single-core optical fibers arranged in two ferrules using a sleeve, wherein a first of the two ferrules has a fiber hole in which a plurality of optical fibers are arranged in a bundle on the same circumference centered on the ferrule central axis, at least one of the two ferrules is rotatable around the ferrule central axis, rotation of at least the other of the two ferrules is restricted, and one of the two ferrules is pressed in a direction in which the ends of the two ferrules butt together.

[0026] This restricts the rotation of at least the other of the two ferrules, thereby suppressing degradation of optical properties at the butted ends of the ferrules due to rotational misalignment. Furthermore, because one of the ferrules is pressed in the direction in which the ends of the two ferrules butt together, the gap between the end faces of the optical fibers wired inside the ferrules can be minimized. Therefore, degradation of optical properties can be suppressed. Thus, according to the present disclosure, even when the optical switch is grounded outdoors where vibrations occur, degradation of optical properties can be suppressed, making it maintenance-free and economical.

[0027] In the optical coupling section according to the present disclosure, the ends of the two ferrules that are butted together may have a convex spherical shape with a center point on the central axis of the ferrules.

[0028] According to this, by rotating the ferrules around the central axis, the end faces of the opposing optical fibers do not come into contact with each other, which makes it possible to prevent deterioration of optical characteristics such as connection loss caused by scratches on the end faces of the optical fibers due to contact. In addition, because the end faces of the opposing optical fibers are non-parallel to each other, the amount of light reflection can be reduced, eliminating the need for a reflective coating and making it possible to provide a more economical optical coupling unit and optical switch.

[0029] In addition, the optical switch according to the present disclosure may include a presser that restricts the rotation of at least the other of the two ferrules and presses one of the two ferrules in a direction in which the ends of the two ferrules butt together.

[0030] This allows the pressing force to be applied to the ferrule suitably via the pressing device.

[0031] By fixing the pressing device to the housing via a stopper, it is possible to restrict the rotation of the ferrule and apply a pressing force to the end face of the ferrule, which is economical and consumes less power.

[0032] Moreover, the optical switch according to the present disclosure may further include: a housing that accommodates at least the other of the two ferrules, a flange that presses the at least the other of the two ferrules, and the presser in the order of the presser, the flange, and the at least the other of the two ferrules; and a stopper that fixes the presser to the housing, wherein the presser restricts rotation of the at least the other of the two ferrules relative to the housing via the stopper, and presses the at least the other of the two ferrules via the flange.

[0033] In addition, the optical switch according to the present disclosure may further include a fixing jig that accommodates at least one of the two ferrules and can be mated with the housing, and the fixing jig may further include a protrusion that engages with the housing, and the housing may be positioned relative to the fixing jig by the protrusion mating with a locking piece of the housing.

[0034] This allows the housing to be positioned relative to the fixture using a simple method.

[0035] In addition, the optical switch according to the present disclosure may further include a rotation mechanism that rotates at least one of the two ferrules around the central axis of the ferrule, an actuator that rotates the rotation mechanism in fixed angular steps and stops it at any angular step, and a bearing that constitutes the rotation mechanism.

[0036] The above inventions can be combined as much as possible.

[0037] According to the present disclosure, it is possible to provide an optical coupling section and an optical switch that can achieve stable optical characteristics against external factors with low power consumption and more economically.

[0038] 1 shows an example of a usage form of the present invention. 2 shows an example of a schematic configuration of the present invention. 3 shows a front view of the end of an output ferrule. 4 shows a front view of the end of an input ferrule. 5 shows a view of an optical coupling unit shown in a longitudinal plane. 6 shows an example of the relationship between excess loss and the clearance between the ferrule outer diameter and the sleeve inner diameter. 7 shows the vicinity of the end of a ferrule in an optical coupling unit of the present invention. 8 shows an example of the relationship between the angle between a cross section perpendicular to the ferrule central axis and the end face of a single-mode optical fiber and the return loss. 9 shows an example of the relationship between excess loss and the gap between the optical fibers. 10 shows an example of the relationship between the radius of curvature of a convex spherical ferrule end face and the angle between a cross section perpendicular to the central axis and the end face of a single-mode optical fiber. 11 shows an example of the relationship between the radius of curvature of a convex spherical ferrule end face and the distance from the tip of the ferrule to the end face of a single-mode optical fiber. 12 shows an example of the relationship between excess loss due to rotation angle deviation and the core arrangement radius. 13 shows an engagement form of an optical coupling unit of the present invention according to embodiment 1. 14 shows an engagement form of an optical coupling unit of the present invention according to embodiment 2. 15 shows a cross section of an input ferrule in an optical coupling unit of the present invention according to embodiment 2. 10 shows a cross section of an input side ferrule of an optical coupling portion of the present invention according to embodiment 2. FIG. 11 shows a side view of an output side flange of the present invention according to embodiment 1. FIG. 12 shows a mating form of an optical coupling portion of the present invention according to embodiment 3.

[0039] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0040] (Embodiment 1) FIG. 1 is a diagram showing an example of an embodiment of the present invention. In this embodiment, a configuration is described in which light is input through an input-side optical fiber S01 and output through an output-side optical fiber S04, but the direction of light may be reversed. The present invention makes it possible to switch the input-side optical fiber S01 connected to a front-stage optical switch component S00 to a specific port of an inter-optical switch optical fiber S02 in the front-stage optical switch component S00, and to switch the port of the inter-optical switch optical fiber S02 to a desired output-side optical fiber S04 in a rear-stage optical switch component S03. The present invention is an optical switch corresponding to the front-stage optical switch component S00 and the rear-stage optical switch component S03. Hereinafter, the front-stage optical switch component S00 will be abbreviated as the optical switch S00, and the rear-stage optical switch component S03 will be abbreviated as the optical switch S03. The optical switch S00 and the optical switch S03 are in a left-right mirror image relationship and have the same configuration, so the detailed configuration will be described below using the optical switch S00.

[0041] 2 is a block diagram showing an embodiment of the present invention. The optical coupling unit S8 of the optical switch S00 according to the present embodiment includes: a first ferrule in which the core centers of a plurality of single-mode optical fibers are arranged on the same circumference from the center in the cross section of the ferrule; a second ferrule in which the core centers of one or more single-mode optical fibers are arranged on a circumference of the same diameter from the center in the cross section of the ferrule as the circumference on which the core centers of the single-mode optical fibers in the first ferrule are arranged; and a cylindrical sleeve S17 having a hollow portion into which the first ferrule and the second ferrule are inserted so that the central axes of the first ferrule and the second ferrule are aligned, with a predetermined gap provided between the outer diameter of the first ferrule and the inner diameter of the hollow portion so that the first ferrule and the second ferrule can rotate.

[0042] 2, the input optical fiber S1 is configured to consist of one single-core single-mode optical fiber, and the input ferrule S6 is configured to be the second ferrule. The output optical fiber S9 is configured to consist of multiple single-core single-mode optical fibers, and the output ferrule S7 is configured to be the first ferrule. The input optical fiber S1 corresponds to the input optical fiber S01 in FIG. 1, and the output optical fiber S9 corresponds to the inter-optical-switch optical fiber S02 in FIG. 1.

[0043] 2 has an optical coupling section S8 composed of an input ferrule S6 into which an input optical fiber S1 is inserted, and an output ferrule S7 into which an output optical fiber S9 is inserted. The input optical fiber S1 is fixed using an adhesive or the like at a predetermined position in a fiber hole provided in the input ferrule S6. The output optical fiber S9 is fixed using an adhesive or the like at a predetermined position in a fiber hole provided in the output ferrule S7.

[0044] When light is incident from the input optical fiber S1, the optical switch S00 can connect the input optical fiber S1 to any one of the output optical fibers S9 by fixing the output ferrule S7 and rotating the input ferrule S6, and output the incident light from one of the output optical fibers S9. This optical switch S00 can be used as a 1xN relay-type optical switch. Conversely, light can also be incident from the output optical fiber S9. For example, light can be incident on multiple single-mode optical fibers among the output optical fibers S9, and then, by fixing the output ferrule S7 and rotating the input ferrule S6, any one of the output optical fibers S9 can be connected to the input optical fiber S1, and only one light selected from the multiple incident light beams can be output from the input optical fiber S1. Furthermore, as shown in FIG. 1, an NxN optical switch can be configured by combining multiple optical switches. Here, the output-side ferrule S7 is fixed and the input-side ferrule S6 is rotated, but any configuration is possible as long as either the input-side ferrule S6 or the output-side ferrule S7 is fixed and the opposing fiber is rotated to enable switching between the opposing fibers, so the input-side ferrule S6 may be fixed and the output-side ferrule S7 may be rotated. Also, although one input-side ferrule S6 is used, it is also possible to arrange multiple optical fibers.

[0045] The following describes an optical switch S00 in which the output ferrule S7 is fixed and the input ferrule S6 is rotated. The output ferrule S7 is fixed to prevent axial rotation by a rotation stop mechanism (not shown). The actuator S3 rotates the ferrule S6 by any angle in response to a signal from a control circuit S4. The input ferrule S6 rotates when the output of the actuator S3 is transmitted via a rotation mechanism S5. The input ferrule S6 is provided with a certain excess length S2 to allow for twisting of the input optical fiber S1. The optical coupling section S8 is configured to suppress axial misalignment of the ferrule central axis using an axial misalignment adjustment mechanism (not shown) to avoid excessive loss due to axial misalignment.

[0046] In the optical coupling section S8 of the optical switch S00 according to this embodiment, the input side ferrule S6 and the output side ferrule S7 each have a convex spherical end in the central axis direction, and the tip of the input side ferrule S6 and the tip of the output side ferrule S7 are butted together.

[0047] FIG. 3 is a schematic diagram showing the end of an output ferrule S7 according to an embodiment of the present invention, viewed from the front. As shown in the figure, a plurality of optical fibers are bundled together and arranged inside a fiber hole S11 having a diameter S21 formed in the center of the output ferrule S7. The core centers of the output optical fibers S9 are arranged on the circumference of a circle having a core arrangement radius Rcore relative to the center of the output ferrule S7. While FIG. 3 illustrates an example in which a dummy fiber S10 is arranged at the center and a total of six output optical fibers S9 are arranged, this is not limiting, as long as the core centers of the plurality of output optical fibers S9 are arranged on the circumference of a circle having the core arrangement radius Rcore. The dummy fiber S10 may be any optical fiber having the same strength and outer diameter as the output optical fiber S9, and may be a fiber without a core, i.e., a fiber that does not transmit light.

[0048] Fig. 4 is a schematic diagram showing the end of an input ferrule S6 according to an embodiment of the present invention, viewed from the front. As shown in Fig. 4, a plurality of optical fibers are bundled together and arranged inside a fiber hole S11 provided in the center of the input ferrule S6, and the core center of the input optical fiber S1 is arranged on the circumference of a circle having a core arrangement radius Rcore relative to the center of the input ferrule S6. Fig. 4 illustrates an example in which one input optical fiber S1 is arranged on the y-axis (x = 0) and arranged at the center of the input ferrule S6 together with six other dummy fibers S10. However, this is not limiting, as long as the core center of the input optical fiber S1 is arranged on the circumference of a circle having a core arrangement radius Rcore. For example, one or more fiber holes capable of accommodating one optical fiber may be provided on the circumference of a circle having a core arrangement radius Rcore relative to the central axis of the input ferrule S6, and the input optical fiber S1 may be arranged in one of the fiber holes. The dummy fiber S10 may be any optical fiber having the same strength and outer diameter as the input optical fiber S1, and may be a fiber without a core, that is, a fiber that does not transmit light.

[0049] The outer diameter of the dummy fiber S10 arranged at the center of the output ferrule S7 and the input ferrule S6 may be different from the outer diameter of the output optical fiber S9 and the input optical fiber S1. For example, by making the outer diameter of the dummy fiber S10 arranged at the center larger than 125 μm, it becomes possible to arrange six or more output optical fibers S9 on the circumference of a circle with a core arrangement radius Rcore.

[0050] However, it is important to minimize the transmission loss of the optical coupling portion S8, and it is desirable that each core of the output optical fiber S9 has the same optical characteristics as the core of the input optical fiber S1 in that it has a mode field diameter that is approximately the same as that of the core of the input optical fiber S1. It is also important to minimize the excess loss due to axial misalignment, and it is desirable that the ferrule outer diameter S15 of the output ferrule S7 is approximately the same as the ferrule outer diameter S15 of the input ferrule S6.

[0051] In this embodiment, the input side ferrule S6 and the output side ferrule S7 are made of zirconia, and the input side optical fiber S1 and the output side optical fiber S9 are made of quartz glass, but this is not limited to this and any optical fiber capable of communicating signal light in the communication wavelength band may be used.

[0052] 5 is a schematic diagram of an optical coupling unit S8 according to an embodiment of the present invention, shown on a longitudinal surface. An input ferrule S6, into which an input optical fiber S1 is inserted, and an output ferrule S7, into which an output optical fiber S9 is inserted, are aligned in a cylindrical sleeve S17 having a hollow portion with an inner diameter S16 that is slightly larger than the outer diameter S15 of the ferrules, by about a sub-micron. A slight clearance C, on the order of sub-micron, is provided between the input ferrule S6 and the output ferrule S7 to control axial misalignment within a certain tolerance range and to prevent interference with the axial rotation of the input ferrule S6.

[0053] FIG. 6 shows the excess loss T for the clearance C between the ferrule outer diameter S15 and the sleeve inner diameter S16 of the input side ferrule S6 and the output side ferrule S7. Ｃ 1 is a diagram showing an example of the relationship between the axial misalignment of the fiber core and the excess loss T. In optical coupling between optical fibers, the axial misalignment of the fiber core is a factor in causing excess loss. Since an increase in excess loss limits the overall length of the optical path, it is necessary to reduce the axial misalignment of the fiber core. Here, the clearance C between the ferrule outer diameter S15 and the sleeve inner diameter S16 corresponds to the axial misalignment of the fiber core, so the clearance C (unit: μm) between the ferrule outer diameter S15 and the sleeve inner diameter S16 and the excess loss T Ｃ The relationship (unit: dB) can be expressed by Equation 1. where ω １ and ω ２are the mode field radii (unit: μm) of the cores of the input and output optical fibers S9, respectively, and Figure 6 shows the loss when the mode field diameters of the cores of the input optical fiber S1 and output optical fiber S9 are both 9 μm. For example, if the ferrule outer diameter S15 and the sleeve inner diameter S16 are processed so that the clearance C is 0.7 μm or less, the maximum excess loss can be suppressed to approximately 0.1 dB or less. Furthermore, if the maximum excess loss is set to 0.2 dB, it is necessary to process the ferrule outer diameter S15 and the sleeve inner diameter S16 so that the clearance C is 1 μm or less.

[0054] 7 is a schematic diagram showing in more detail the vicinity of the end of the ferrule of the optical coupling unit S8 according to the embodiment of the present invention. The end of the input side ferrule S6 and the output side ferrule S7 are aligned along the ferrule central axis A. Ｃ The output ferrule S7 of this embodiment has a convex spherical shape with a center point on the top. Specifically, as shown in FIG. 3, the output ferrule S7 has a dummy fiber S10 arranged at the center of the fiber hole S11, and the output optical fiber S9 arranged around the dummy fiber S10. The end faces of the output optical fiber S9 and the dummy fiber S10 arranged in the output ferrule S7 form the convex spherical shape of the end of the output ferrule S7. As shown in FIG. 4, the output ferrule S6 of this embodiment has a dummy fiber S10 arranged at the center of the fiber hole S11, and the input optical fiber S1 and the dummy fiber S10 arranged around the dummy fiber S10. The end faces of the input optical fiber S1 and the dummy fiber S10 arranged in the output ferrule S6 form the convex spherical shape of the end of the input ferrule S6.

[0055] The dummy fibers S10 disposed in the input ferrule S6 and the output ferrule S7 are butted together at their respective ends. As described above, the input fiber S1 and the output fiber S9 are aligned along the ferrule central axis A in the cross section of the ferrules. ＣThe input fiber S1 and the output fiber S9 are arranged at a position of a core arrangement radius Rcore from the ferrule center axis A. The end faces of the input fiber S1 and the output fiber S9 are set back from the tip to prevent the end faces from coming into contact and being damaged when switching by rotation. Also, the end faces of the input fiber S1 and the output fiber S9 are set back from the ferrule center axis A to prevent deterioration of signal characteristics due to reflection. Ｃ The angle θ between the cross section perpendicular to the ferrule S6 and the end face of the single-core optical fiber is controlled. For example, a convex spherical shape can be fabricated by using a polishing technique used in the fabrication of general optical connectors. In FIG. 7 , the end faces of the dummy fibers S10 arranged along the central axes of the ferrules are butted together. However, this is not limiting, and any arrangement may be adopted as long as the end faces of the input fiber S1 and the output fiber S9 do not contact each other. For example, when polishing the ferrule end faces, the amount of fiber retraction may be increased to prevent the end faces of the input fiber S1 and the output fiber S9 from contacting each other when the input ferrule S6 and the output ferrule S7 are butted together.

[0056] Fig. 8 is a diagram showing an example of the relationship between the angle θ between a cross section perpendicular to the ferrule central axis and the end face of a single-mode optical fiber and the return loss R. In the optical coupling section S8, if there is an area with a different refractive index between the end face of the input optical fiber S1 and the end face of the output optical fiber S9, reflection will cause deterioration of the signal characteristics. In the configuration of the present invention shown in Fig. 7, there is a gap G between the end face of the input optical fiber S1 and the end face of the output optical fiber S9, and since silica glass and air have different refractive indices, some measure to reduce reflection is required. In the present invention, reflection is reduced by controlling the angle θ. Ferrule central axis A Ｃ The relationship between the angle θ (unit: degrees) formed by the cross section perpendicular to the surface and the end face of the single mode optical fiber and the return loss R (unit: dB) can be expressed by Equation 2. where n １ , ω １ , λ are the refractive index of the optical fiber, the mode field radius of the optical fiber core (unit: μm), and the wavelength of the propagating light in a vacuum (unit: μm), respectively. ０is the return loss at the flat end face, which can be expressed by Equation 3. where n ２ is the refractive index of the light receiving medium, that is, the refractive index of air. In this embodiment, the wavelength λ is 1310 nm and the mode field radius ω １ When the reflection loss R ０ is 14.7 dB, and for example, the ferrule central axis A Ｃ By making the angle θ between the cross section perpendicular to the fiber and the end face of the single-mode optical fiber 4.5 degrees or more, it is possible to maintain a return loss R of 40 dB or more. Furthermore, by processing a reflective coating on the end face of the fiber, it is possible to further improve the reflection characteristics.

[0057] Figure 9 shows the excess loss T Ｇ In the optical coupling between the input optical fiber S1 and the output optical fiber S9, if a gap G exists between the end face of the input optical fiber S1 and the end face of the output optical fiber S9, the distribution of the output light from the input optical fiber S1 will be broadened, and the coupling efficiency with the core of the output optical fiber S9 will decrease, which will cause excess loss. Ｇ The relationship (unit: dB) can be expressed by Equation 4. where λ, n ｃｌａｄ , ω １ , ω ２ are the wavelength of the propagating light in a vacuum (unit: μm), the refractive index of the optical fiber cladding, i.e., pure silica, and the mode field radius of the cores of the input optical fiber S1 and the output optical fiber S9 (unit: μm), respectively. Figure 9 shows the loss when the mode field diameters of the cores of the input optical fiber S1 and the output optical fiber S9 are both 9 μm. For example, by adjusting the gap G between the end face of the input optical fiber S1 and the end face of the output optical fiber S9 to be 22 μm or less, the excess loss can be suppressed to 0.1 dB or less.

[0058] FIG. 10 shows the relationship between the radius of curvature Rcur of the convex spherical ferrule end face and the ferrule central axis A. Ｃ1 is a diagram showing an example of the relationship between the radius of curvature Rcur (unit: mm) of the convex spherical ferrule end face and the ferrule central axis A. Ｃ The relationship between the angle θ (unit: degrees) formed by the cross section perpendicular to the plane and the end face of the single mode optical fiber can be expressed by Equation 5 using the core arrangement radius Rcore (unit: μm). 10 is a diagram showing the relationship between the angle θ and the radius of curvature Rcur when the core arrangement radius Rcore is 125, 150, 200, and 250 μm. From FIG. 8, it can be seen that the angle θ that can maintain a return loss R of 40 dB or more is 4.5 degrees or more, and that a radius of curvature Rcur that achieves an angle θ of 4.5 degrees or more can be achieved for a core arrangement radius Rcore of 250 μm or less. For example, when the core arrangement radius Rcore is 125 μm, 150 μm, 200 μm, and 250 μm, by adjusting the radius of curvature Rcur to 1.5 mm or less, 1.9 mm or less, 2.5 mm or less, and 3.2 mm or less, respectively, the angle θ becomes 4.5 degrees or more, and a return loss R of 40 dB or more can be maintained. The outer diameter of a typical single-mode optical fiber is 125 μm. When the single-mode optical fiber is arranged in a bundle as shown in FIG. 3, the ferrule end face is polished to have a radius of curvature Rcur of 1.5 mm or less, thereby achieving a ferrule central axis A Ｃ The angle θ formed by the cross section perpendicular to the surface and the end face of the single mode optical fiber is 4.5 degrees or more, and a return loss R of 40 dB or more can be achieved.

[0059] 11 is a diagram showing an example of the relationship between the radius of curvature Rcur of the convex spherical ferrule end face and the distance D from the ferrule tip to the end face of the single-mode optical fiber. The distance D from the ferrule tip to the end face of the single-mode optical fiber corresponds to half the gap G between the end face of the input optical fiber S1 and the end face of the output optical fiber S9, and the radius of curvature Rcur (unit: mm) of the convex spherical ferrule end face and the ferrule central axis A Ｃ This can be expressed by Equation 6 using the angle θ (unit: degrees) formed by the cross section perpendicular to the plane and the end face of the single mode optical fiber.

[0060] 11 shows the relationship between the radius of curvature Rcur and the distance D from the ferrule tip to the fiber end face when the core arrangement radius Rcore is 125, 150, 200, and 250 μm. For example, when the core arrangement radius Rcore is 125 μm, 150 μm, 200 μm, and 250 μm, by adjusting the radius of curvature Rcur to 0.7 mm or more, 1.0 mm or more, 1.8 mm or more, and 2.8 mm or more, respectively, the distance D from the ferrule tip to the fiber end face becomes 11 μm or less, that is, the gap G becomes 22 μm or less, and the excess loss T due to the gap as shown in FIG. Ｇ The outer diameter of a typical single-mode optical fiber is 125 μm, and when the single-mode optical fiber is arranged in a bundle as shown in FIG. 3, by polishing the ferrule end face so that the radius of curvature R is 0.7 mm or more and 1.5 mm or less, a return loss R of 40 dB or more and an excess loss T of 0.1 dB or less can be achieved. Ｇ This can be achieved.

[0061] In the optical coupling section S8 of the optical switch S00 according to this embodiment, in order to obtain a return loss of 40 dB or more and an excess loss due to a gap of 0.1 dB or less, the radius of curvature of the convex spherical shape of each of the input side ferrule S6 and the output side ferrule S7 may be 0.7 mm or more and 3.2 mm or less.

[0062] Next, the requirements for the actuator S3 in FIG. 2, the output-side ferrule S7 described in FIG. 3, and the input-side ferrule S6 described in FIG. 4 will be described. The actuator S3 is a drive mechanism that rotates at any angle step in response to a pulse signal from the control circuit S4 and has a constant static torque for each angle step, and a stepping motor, for example, is used. Note that other methods may also be used for the actuator S3 as long as the drive mechanism rotates at any angle step in response to a pulse signal from the control circuit S4 and has a constant static torque for each angle step. The rotation speed and rotation angle are determined by the period and number of pulses of the pulse signal from the control circuit S4, and the angle step and static torque may be adjusted via a reduction gear. Note that, as described above, the input-side ferrule S6 in the optical coupling unit S8 is rotated along the ferrule central axis A. Ｃ Since the input ferrule S6 is designed to rotate around the center of gravity, the static torque required to maintain the rotation angle of the input ferrule S6 is applied by the actuator S3.

[0063] This provides a self-holding function that does not require power when stationary after switching, and it is possible to minimize the driving energy required when switching optical paths, making it possible to provide a low-power optical switch.

[0064] Here, in a stepping motor, if the number of angle steps at which the angle position is maintained when the power supply is stopped is defined as the static angle step number, the static angle step number is a natural number multiple of the number of cores having the same core arrangement radius Rcore in the output side optical fiber S9.

[0065] In addition, the excess loss due to the rotation angle deviation in the optical coupling section S8 is expressed as T Ｒ (unit: dB), the rotation angle deviation related to the static angle accuracy of the stepping motor is Φ (unit: °), and the core arrangement radius Rcore (unit: μm), the relationship between these can be expressed by Equation 7. Excess loss T due to rotation angle deviation from core placement radius Rcore ＲAn example of the relationship between the core arrangement radius Rcore and the excess loss T due to the rotation angle misalignment when the rotation angle misalignment Φ is 0.1 degrees, 0.15 degrees, 0.2 degrees, and 0.3 degrees is shown in FIG. Ｒ The larger the core arrangement radius Rcore, the larger the excess loss. １ and ω ２ When the MFD is 4.5 μm (MFD=9 μm), the excess loss T due to the rotation angle misalignment is 0.15 degrees even when the core placement radius is 250 μm or less. Ｒ When single-mode optical fibers with a fiber outer diameter of 125 μm are arranged in a bundle as shown in FIG. 3, the core arrangement radius R is 125 μm. Therefore, as shown in FIG. 12, even with a rotation angle misalignment of 0.3 degrees, the excess loss T due to the rotation angle misalignment Ｒ It is possible to keep the noise level at 0.1 dB or less.

[0066] 13 is a schematic diagram showing an example of the mating configuration of the optical coupling unit S8 according to the first embodiment of the present invention. The output ferrule S7 is attached to the output flange S19, which is attached to a fixture S27 with a set screw S25, thereby fixing the axial direction and the axial rotation direction. The input ferrule S6 is attached to a rotating flange S29, which is provided with a bearing S26, which is also attached to the fixture S27 with a set screw S25, thereby fixing the axial direction. A sleeve S17 is built into the fixture S27, and the input ferrule S6 and the output ferrule S7 are inserted into the sleeve S17 to align the ferrule central axes. The output ferrule S7 is fixed, and the input ferrule S6 rotates within the sleeve S17 by a rotation mechanism S5 of the bearing S26, around the center of the ferrule cylinder. As a result, the core of the input optical fiber S1 inserted into the input ferrule S6 rotates, switching the core of the output optical fiber S9 facing the input optical fiber S1. While the bearing S26 is made of, for example, zirconia, other materials may also be used as long as they can be manufactured with high dimensional accuracy. Furthermore, by using a low-rigidity hollow metal frame for the fixing jig S27, for example, it is possible to reduce axial misalignment of the input ferrule S6 due to axial wobble during rotation of the actuator S3.

[0067] 17 shows a side view of the output flange S19 attached to the output ferrule S7. As shown in FIG. 17, the capillary S23 is aligned with the fiber hole S30 of the output ferrule S7 attached to the output flange S19 and the ferrule central axis A. ＣBy arranging the capillary S23 at a position where the ends of the capillary S23 and the input ferrule S6 are aligned, tapering the capillary S23 in the longitudinal direction and bringing the diameter of its tip closer to the diameter of the fiber hole S30 of the output ferrule S7, it is possible to prevent the output optical fiber S9 from getting caught on a step when inserting it into the output ferrule S7, and further to prevent the optical fiber from breaking. The same applies to the rotating flange S29 attached to the input ferrule S6. In this embodiment, an example is shown in which a capillary tapered in the longitudinal direction is inserted inside the flange, but the shape of the inside of the flange is not limited to this as long as it allows the optical fiber to be inserted into the fiber hole and protects the optical fiber when the optical coupling unit is fabricated.

[0068] In this invention, the ends of two ferrules, each having a single-mode optical fiber arranged parallel to the central axis and at the same distance from the central axis, are convex, and by butting the tips of the ends of the two ferrules together so that their central axes coincide, and rotating one of the ferrules around its central axis, the end faces of the opposing optical fibers do not come into contact with each other, preventing deterioration of optical characteristics such as connection loss due to scratches on the end faces of the optical fibers caused by contact.In addition, by making the end faces of the opposing optical fibers non-parallel to each other, the amount of light reflection can be reduced, eliminating the need for a reflective coating, and providing a more economical optical coupling unit and optical switch.

[0069] Furthermore, in the present invention, one of the input and output sides of the optical coupling unit S8 that performs optical switching is an axially rotatable mechanism, which makes it possible to minimize the energy required by the actuator S3, i.e., the torque output, and thereby reduce power consumption. Furthermore, the amount of optical axis misalignment in directions other than the axial rotation of the input ferrule S6 is compensated for by the sleeve S17 in the optical coupling unit S8, thereby enabling low loss. In addition, the present invention does not include a collimator or special vibration isolation mechanism, and is instead composed of commonly used optical connection components such as ferrules and sleeves, making it compact and economical.

[0070] Therefore, the present invention makes it possible to provide an optical coupling unit and an optical switch that can achieve stable optical characteristics against external factors such as temperature and vibration with low power consumption and more economically. As a result, the optical coupling unit and the optical switch can be used as an optical switch that switches paths in optical lines using single-mode optical fibers in optical fiber networks, regardless of location, in any facility.

[0071] (Embodiment 2) The configuration and operation of the optical switch S00 according to this embodiment will be specifically described below with reference to Figures 14 and 15. In the optical switch S00 of this embodiment, the input ferrule S6 of the optical coupling section S8 is attached to the input flange S18 instead of the rotating flange S29, and the position at which the bearing S26 is provided differs from that of the optical switch S00 of embodiment 1. The rotation mechanism of the input ferrule S6 will be described below. Note that the contents other than those described below are the same as those of embodiment 1.

[0072] 14 is a schematic diagram showing the mating configuration of the optical coupling unit S8 according to this embodiment. As in the first embodiment, the output ferrule S7 is attached to the output flange S19, and the output flange S19 is attached to a fixing jig S27 with fixing screws S25, so that the axial direction and the axial rotation direction are fixed.

[0073] The input ferrule S6 is attached to the input flange S18. The input flange S18 is attached to a fixing jig S27 with removable fixing screws S25, and the axial direction and axial rotation direction are fixed. Loosening the fixing screws S25 allows the input flange S18 to rotate, which in turn allows the input ferrule S6 attached to the input flange S18 to rotate. The input flange S18 may also have a structure shown in FIG. 15, as described below. In this case, a separate fixing screw (not shown) may be provided to fix the axial direction. The input ferrule S6 has a ferrule outer diameter S15 smaller than that of the output ferrule S7, is attached to a bearing S26, and is rotated by a rotation mechanism S5 of the bearing S26. In other words, with the output ferrule S7 fixed and the input flange S18 rotatable, the input ferrule S6 rotates within the sleeve S17 around the center of the ferrule cylinder by the rotation mechanism S5 of the bearing S26. As a result, the core of the input optical fiber S1 inserted into the input ferrule S6 rotates, and the core of the output optical fiber S9 opposite to the input optical fiber S1 is switched.

[0074] Fig. 15 is a schematic diagram showing a cross section of the input ferrule S6 of the optical coupling unit S8 according to this embodiment. A bearing S26 is attached around the input ferrule S6, allowing the input ferrule S6 to rotate freely within the sleeve S17. Fig. 15 also shows an example in which a fixing spring S28 is used as a method for fixing the input flange S18. A groove as shown in Fig. 15 is provided in advance in the input flange S18, and the tip of the fixing spring S28 is clamped into the groove to fix the input flange S18 and the input ferrule S6 fixed thereto. The fixing spring S28 is urged in the direction of the arrow D ＳBy applying a force to the input ferrule S6, the input ferrule S6 is released from the fixed position and becomes rotatable. For example, by linking the fixing and releasing of this fixing spring S28 with a control circuit S4 (not shown) that controls the actuator S3, it is possible to control the optical fiber switching in a unified manner. Also, as shown in FIG. 16, by forming the outer periphery of the input flange S18 into a shape in which multiple gears are arranged so that the grooves are offset along the longitudinal direction of the input ferrule S6, it is possible to perform more precise control of the rotation angle. Furthermore, instead of using the fixing spring S28, a magnet or a solenoid may be used as a method for fixing and releasing the input flange S18.

[0075] (Embodiment 3) The configuration and operation of an optical switch S00 according to this embodiment will be specifically described below with reference to FIG. 18 . In the optical switch S00 according to this embodiment, the output ferrule S7 of the optical coupling section S8 is not provided with an output flange S19, but rather with a pressing force-applying flange S31 to which a pressing device S32 is attached. The pressing device S32 applies a pressing force in the longitudinal direction of the ferrule, in the direction in which the end faces of the input ferrule S6 and the output ferrule S7 abut against each other. The pressing device S32 holds the output ferrule S7 via the pressing force-applying flange S31. The pressing device S32 is also attached to the housing S33 by a stopper S34. A method for fixing the output ferrule S7 will be described below. Note that the details other than those described below are the same as those of embodiment 1.

[0076] Specifically, the optical coupling unit S8 is an optical coupling unit that couples single-core optical fibers S1 and S9 arranged in two ferrules S6 and S7 using a sleeve S17, and is characterized in that the output ferrule S7 has a fiber hole in which multiple optical fibers are arranged in a bundle on the same circumference centered on the ferrule central axis, the input ferrule S6 is rotatable around the ferrule central axis, the rotation of the output ferrule S7 is restricted, and the output ferrule S7 is pressed in a direction in which the ends of the two ferrules butt together.

[0077] The optical switch S00 is also characterized in that it includes a presser S32 in the optical coupling section S8 that restricts the rotation of the output ferrule S7 and presses the output ferrule S7 in a direction in which the ends of the two ferrules butt together.

[0078] FIG. 18 is a schematic diagram showing the mating configuration of the optical coupling unit S8 according to this embodiment. As in the first embodiment, the input ferrule S6 is attached to a rotating flange S29, a bearing S26 is provided on the rotating flange S29, and the input ferrule S6 is attached to a fixing jig S27 with a fixing screw S25, thereby fixing the axial direction. However, the configuration of the input side of the optical coupling unit S8 according to this embodiment is not limited to this. As in the second embodiment, the input ferrule S6 is attached to an input flange S18, and the input flange S18 is attached to a fixing jig S27 with a removable fixing screw S25, thereby fixing the axial direction and the axial rotation direction. By loosening the fixing screw S25, the input flange S18 becomes rotatable, and accordingly the input ferrule S6 attached to the input flange S18 can rotate. Alternatively, the input ferrule S6 may have a ferrule outer diameter S15 smaller than that of the output ferrule S7, and a bearing S26 may be attached to the input ferrule S6, which may be rotated by a rotation mechanism S5 of the bearing S26.

[0079] A pressing force applying flange S31 is attached to the output ferrule S7. A pressing device S32 is attached to the pressing force applying flange S31 in the longitudinal direction of the input ferrule S6 and the output ferrule S7, applying a pressing force in a direction in which the end faces of the input ferrule S6 and the output ferrule S7 abut against each other. Specifically, the pressing device S32 presses the pressing force applying flange S31 to the left in FIG. 18 . As the pressing force applying flange S31 is pressed to the left, the output ferrule S7 to which the pressing force applying flange S31 is attached is also pressed to the left. The pressing device S32 is attached to a stopper S34 and fixed in the rotational direction. The stopper S34 is attached to the housing S33, thereby fixing the pressing device S32 in the rotational direction relative to the housing S33. The front end of the pressing device S32 is fixed to the rear end of the pressing force applying flange S31. As a result, the output side ferrule S7 attached to the pressing force applying flange S32 is fixed in the rotational direction relative to the housing S33.

[0080] Here, the presser S32 may be a coupling of a bellows type, a slit type, a disk type, etc. The material of the presser S32 may be a metal such as stainless steel or a polymer compound such as rubber, and is not limited to these as long as it holds the output ferrule S7 so as not to rotate and applies a pressing force in the direction in which the end faces of the two ferrules, the input ferrule and the output ferrule, butt together.

[0081] The housing S33 accommodates the output ferrule S7, the pressing force applying flange S31, and the pressing device S32, in this order: the pressing device S32, the pressing force applying flange S31, and the output ferrule S7. In this embodiment, the fixing jig S27 and the housing S33 may be mated using a mating method used for general optical connectors. That is, the housing S33 is inserted into and fixed to the fixing jig S27 by providing a mating mechanism for an optical connector plug in the optical connector in the housing S33 and a mating mechanism for an optical connector adapter in the optical connector in the fixing jig S27. That is, a protrusion S35 is provided on the inner surface of the fixing jig S27 that contacts the housing S33, and a locking piece S36 is provided on the housing S33, and the housing S33 is fixed (positioned) to the fixing jig S27 by mating the protrusion S35 with the locking piece S36.

[0082] However, the scope of the present disclosure is not limited to this. The stopper S34 may be formed integrally with the housing S33.

[0083] As described above, the stopper S34 fixes the pressing device S32 in the rotational direction relative to the housing S33, and the pressing device S32 is fixed to the fixing jig S27 via the stopper S34 and the housing S33. The output ferrule S7 attached to the pressing force-applying flange S31 fixed to the pressing device S32 is also fixed to the housing S32 and the fixing jig S27. When using a fixing screw to fix the flange, the designed fixation in the rotational direction may not be achieved depending on how the fixing screw is fastened. In contrast, in this embodiment, the stopper 34 can be used to accurately fix the pressing device S32 that presses the output ferrule S7 to the housing S33, thereby suppressing degradation of optical characteristics. Note that, although two stoppers S34 are provided in this embodiment, the scope of the present disclosure is not limited thereto. The number of stoppers S34 may be one or three or more.

[0084] At this time, the housing S33 is fixed at a predetermined position relative to the fixing jig S27, so that an appropriate pressing force is applied to the ferrule end face. That is, with the output ferrule S7, the pressing force-applying flange S31, and the pressing device S32 fixed in the rotational direction relative to the housing S33 and the fixing jig S27, the pressing device S32 contracts, applying a pressing force in the longitudinal direction of the ferrule. Specifically, as the pressing device S32 is pressed leftward, the pressing force-applying flange S31 is pressed leftward. As the pressing force-applying flange S31 is pressed leftward, the output ferrule S7, to which the pressing force-applying flange S31 is attached, is also pressed leftward. This minimizes the gap between the end faces of the optical fibers wired inside the ferrules. Therefore, it is possible to suppress degradation of optical characteristics. Note that in the present embodiment, the pressing device S32 presses the output ferrule S7, applying a pressing force to the ferrule end face, but the scope of the present disclosure is not limited thereto. A pressing device S32 may be provided on the input side, and the input side ferrule S6 may be pressed against the pressing device S32, thereby applying a pressing force to the ferrule end face.

[0085] As described above, according to this embodiment, even when the optical switch S00 is grounded outdoors where vibrations occur, deterioration of the optical characteristics can be suppressed, and the optical switch S00 is maintenance-free and economical. Furthermore, according to this embodiment, by simply providing a single member, the pressing device S32 that can be attached to the stopper S34, it is possible to restrict the rotation of the output-side ferrule S7 and apply a pressing force to the ferrule end face, which is low power consumption and economical.

[0086] In this embodiment, the output ferrule S7 is fixed in the rotational direction with its end face pressed against the end face of the input ferrule, and the input ferrule S6 rotates around the center of the ferrule cylinder within the sleeve S17. This causes the core of the input optical fiber S1 inserted into the input ferrule S6 to rotate, switching the core of the output optical fiber S9 facing the input optical fiber S1.

[0087] As described above, according to the present invention, it is possible to provide an optical coupling section and an optical switch that can realize stable optical characteristics against external factors with low power consumption and more economically.

[0088] The above inventions can be combined as much as possible.

[0089] The optical couplers and optical switches according to the present disclosure can be applied to the optical communication industry.

[0090] S00: Front-stage optical switch component S00: Optical switch S01: Input-side optical fiber S02: Optical fiber between optical switches S03: Back-stage optical switch component S03: Optical switch S04: Output-side optical fiber S1: Input-side optical fiber S2: Excess length S3: Actuator S4: Control circuit S5: Rotation mechanism S6: Input-side ferrule S7: Output-side ferrule S8: Optical coupling section S9: Output-side optical fiber S10: Dummy fiber S11: Fiber hole S15: Ferrule outer diameter S16: Sleeve inner diameter S17: Sleeve S18: Input-side flange S19: Output-side flange S21: Fiber hole diameter S23: Capillary S25: Fixing screw S26: Bearing S27: Fixing jig S28: Fixing spring S29: Rotating flange S30: Fiber hole S31: Pressing force applying flange S32: Presser S33: Housing S34: Stopper S35: Protrusion S36: Locking piece

Claims

1. An optical coupling unit that uses a sleeve to couple a single-core optical fiber arranged in two ferrules, wherein a first of the two ferrules has a fiber hole in which a plurality of optical fibers are arranged in a bundle shape on the same circumference centered on the ferrule central axis, at least one of the two ferrules is rotatable around the ferrule central axis, rotation of at least the other of the two ferrules is restricted, and one of the two ferrules is pressed in a direction in which the ends of the two ferrules butt together.

2. The optical coupling unit according to claim 1, wherein the butted ends of the two ferrules have a convex spherical shape having a center point on the central axis of the ferrules.

3. An optical switch comprising an optical coupling section as claimed in claim 1, further comprising a pressing device which restricts rotation of at least the other of the two ferrules and presses one of the two ferrules in a direction in which the ends of the two ferrules butt together.

4. The optical switch according to claim 3, further comprising: a housing that accommodates at least the other of the two ferrules, a flange that presses at least the other of the two ferrules, and the presser, in the order of the presser, the flange, and at least the other of the two ferrules; and a stopper that fixes the presser to the housing, wherein the presser restricts rotation of at least the other of the two ferrules relative to the housing via the stopper, and presses at least the other of the two ferrules via the flange.

5. The optical switch as described in claim 4, further comprising a fixing jig which accommodates at least one of the two ferrules and can be mated with the housing, the fixing jig further comprising a protrusion which engages with the housing, the housing being positioned relative to the fixing jig by the protrusion mating with a locking piece of the housing.

6. An optical switch as claimed in any one of claims 3 to 5, further comprising: a rotation mechanism which rotates at least one of the two ferrules around the central axis of the ferrule; an actuator which rotates the rotation mechanism at constant angular steps and stops it at any arbitrary angular step; and a bearing which constitutes the rotation mechanism.

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