WO2025022649A1 - 光結合部及び光スイッチ - Google Patents

光結合部及び光スイッチ Download PDF

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Publication number
WO2025022649A1
WO2025022649A1 PCT/JP2023/027583 JP2023027583W WO2025022649A1 WO 2025022649 A1 WO2025022649 A1 WO 2025022649A1 JP 2023027583 W JP2023027583 W JP 2023027583W WO 2025022649 A1 WO2025022649 A1 WO 2025022649A1
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Prior art keywords
ferrule
ferrules
optical
fiber
input
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PCT/JP2023/027583
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English (en)
French (fr)
Japanese (ja)
Inventor
千里 深井
幾太郎 大串
和典 片山
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NTT Inc
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Nippon Telegraph and Telephone Corp
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Priority to PCT/JP2023/027583 priority Critical patent/WO2025022649A1/ja
Priority to JP2025535532A priority patent/JPWO2025022649A1/ja
Publication of WO2025022649A1 publication Critical patent/WO2025022649A1/ja
Anticipated expiration legal-status Critical
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means

Definitions

  • the present invention relates to an optical coupling unit used primarily to switch the path of an optical line using a single-mode optical fiber in an optical fiber network, and an optical switch using the same.
  • Non-Patent Document 1 Various methods have been proposed for all-optical switches that switch paths while keeping light as it is, as shown in Non-Patent Document 1, for example.
  • optical fiber-type mechanical optical switches which use a robot arm or motor to control the butting of optical fibers or optical connectors, are inferior to other methods in that they have a slow switching speed, but they 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 when power is lost.
  • Representative structures include a method in which a stage using an optical fiber V-groove is translated, a method in which a mirror or prism is translated or angle-changed to selectively couple to multiple optical fibers emitting from an input optical fiber, and a method in which a robot arm is used to connect a jumper cable with an optical connector.
  • a method has also been proposed in which a multicore fiber is used as the optical path for switching.
  • a multicore fiber is used as the optical path for switching.
  • a multicore fiber with a three-dimensional MEMS optical switch (see, for example, Non-Patent Document 2)
  • a cylindrical ferrule into which the multicore fiber is inserted see, for example, Patent Document 1
  • optical components such as lenses and prisms are not required, making it possible to simplify the configuration.
  • Non-Patent Document 1 has a problem that it is difficult to further reduce power consumption, miniaturize, and make it economical.
  • a motor is generally used as a drive source, but since it is a mechanism for linearly moving a heavy object such as a stage, a certain amount of torque is required for the motor, and power consumption is required to obtain an appropriate output to maintain the required torque.
  • the robot arm method using optical connectors 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, over several tens of watts.
  • Non-Patent Document 2 Furthermore, in the optical path switching using the multicore fiber described in Non-Patent Document 2, a collimation 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 are separately required in the process of manufacturing the optical switch, which causes the assembly process to become complicated.
  • Non-Patent Document 3 there is a method to prevent scratches on the fiber end surface due to contact by providing a gap in advance in a cylindrical ferrule into which an optical fiber is inserted, and using a connection configuration that does not involve fiber contact.
  • a connection configuration that does not involve fiber contact.
  • a special coating to prevent reflection is required, which creates the problem of increased costs.
  • Non-Patent Document 4 Another method for preventing reflections is to polish the ferrule end faces at an angle (for example, Non-Patent Document 4).
  • problems such as interference at the ferrule end faces when switching by rotation, or a large gap being required, resulting in large connection loss.
  • the ferrule is polished to a spherical surface, the fiber end face is polished at an angle, and the center of the ferrule is polished flat to minimize the gap that occurs on the fiber end face, so it is possible to prevent reflection while preventing scratches on the fiber end face due to contact and to keep connection loss due to gaps low.
  • the manufacturing process of the ferrule mold it is difficult to control the fiber hole position with high precision, and there is a problem that axial misalignment loss due to fiber hole position misalignment occurs as excess loss.
  • the present invention aims to provide an optical coupling section and an optical switch that can achieve stable optical characteristics against external factors with low power consumption and in a more economical manner.
  • the optical coupling unit includes: An optical coupling unit that couples single-core optical fibers arranged in two ferrules using a sleeve, A first ferrule of the two ferrules has a plurality of optical fibers arranged in a fiber hole in a bundle shape on the same circumference centered on a central axis of the ferrule, At least one of the two ferrules is rotatable about the ferrule central axis, The ends of the two ferrules that are butted together have a convex spherical shape having a center point on the central axis of the ferrule.
  • the optical coupling unit and optical switch disclosed herein may include two ferrules in which a single-core single-mode optical fiber is arranged parallel to and at the same distance from the central axis of the ferrule.
  • the ends of the two ferrules that are butted together 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.
  • the optical coupling unit comprises: a first ferrule having a convex spherical end face, the first ferrule including a plurality of single-core single-mode optical fibers arranged in a bundle shape such that the core centers of the single-core single-mode optical fibers are aligned on the same circumference in a central portion of the ferrule cross section; 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 having 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 a 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 coincide, and a predetermined gap is provided between the outer diameters of the
  • the ends of two ferrules in which single-mode optical fibers are arranged parallel to and at the same distance from the central axis of the ferrule, have a convex spherical shape, and by butting the tips of the ends of the two ferrules 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 caused by scratches on the end faces of the optical fibers due to contact.
  • the end faces of the opposing optical fibers are non-parallel to each other, the amount of light reflection can be reduced, making it possible to provide a more economical optical coupling unit and optical switch without the need for a reflective coating.
  • one of the input and output sides of the optical coupling section that performs optical switching is made into an axially rotatable mechanism, so it is possible to minimize the energy required by the actuator, i.e., the torque output, and to reduce power consumption. Also, the amount of optical axis deviation in directions other than the axial rotation of the input ferrule is guaranteed by the sleeve in the optical coupling section, making it possible to reduce loss.
  • the present invention does not include a collimator or special vibration isolation mechanism, and is composed of commonly used optical connection parts such as ferrules and sleeves, making it small and economical.
  • a dummy fiber may be arranged inside the 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.
  • the return loss in the convex spherical shape may be equal to or greater than a predetermined value.
  • the angle between a cross section perpendicular to the central axis of the ferrule and the end face of the single mode optical fiber may be equal to or greater than 4.5 degrees in each of the first ferrule and the second ferrule. This allows the return loss in the convex spherical shape to be equal to or greater than 40 dB.
  • excess loss T G due to a gap between the butted end faces of the two ferrules may be suppressed.
  • 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 coincides with that of the single mode optical fiber may be 22 ⁇ m or less. This makes it possible to suppress excess loss T G due to the gap to 0.1 dB or less.
  • excess loss TR due to rotation angle misalignment of the two ferrules may be suppressed.
  • the distance from the central axis of the ferrule to the core center of each single mode optical fiber in the first ferrule and the second ferrule may be 250 ⁇ m or less. This makes it possible to suppress excess loss TR due to rotation angle misalignment to 0.1 dB or less.
  • the optical coupling unit according to the present disclosure may satisfy the conditions of the return loss in the convex spherical shape and the excess loss T G due to a gap between the end faces of the two ferrules where the end faces are butted together.
  • the optical fibers may be single mode optical fibers, and a radius of curvature in 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.
  • the optical switch according to the present disclosure comprises: The optical coupling portion; and a rotation mechanism that rotates one of the two ferrules of the optical coupling portion about a central axis of the ferrule.
  • an optical switch may include: an actuator that rotates the rotation mechanism at a constant angular step and stops the rotation mechanism at an arbitrary angular step;
  • a bearing constituting the rotation mechanism; may further comprise:
  • the optical coupling unit has An optical coupling unit that couples single-core optical fibers arranged in two ferrules using a sleeve, comprising: A first ferrule of the two ferrules has a plurality of optical fibers arranged in a fiber hole in a bundle shape on the same circumference centered on a central axis of the ferrule, At least one of the two ferrules is rotatable about the ferrule central axis, Rotation of at least the other of the two ferrules is restricted, Either of the two ferrules is pressed in a direction such that the ends of the two ferrules butt against each other.
  • the rotation of at least the other of the two ferrules is restricted, suppressing the degradation of optical properties at the butted ends of the ferrules caused by rotational misalignment.
  • one of the ferrules is pressed in the direction in which the ends of the two ferrules butt together, so the gap between the end faces of the optical fibers wired inside the ferrules can be kept to a necessary minimum. This makes it possible to suppress degradation of optical properties. In this way, according to the present disclosure, even when the optical switch is grounded outdoors where vibrations occur, it is possible to suppress degradation of optical properties, making it maintenance-free and economical.
  • optical coupling section may have a convex spherical shape with a center point on the central axis of the ferrules at the ends where the two ferrules are butted together.
  • the end faces of the opposing optical fibers do not come into contact with each other, preventing deterioration of optical properties such as connection loss caused by scratches on the end faces of the optical fibers due to contact.
  • the end faces of the opposing optical fibers are non-parallel to each other, the amount of light reflection can be reduced, making it possible to provide a more economical optical coupling unit and optical switch without the need for a reflective coating.
  • the optical switch according to the present disclosure may also include a presser that 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.
  • the pressure device is fixed to the housing via a stopper, which allows the rotation of the ferrule to be restricted and pressure to be applied to the end face of the ferrule, resulting in low power consumption and economical use.
  • the optical switch according to the present disclosure is 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;
  • a stopper that fixes the pressing device to the housing, The pressing device may restrict rotation of at least the other of the two ferrules relative to the housing via a stopper, and may press at least the other of the two ferrules via the flange.
  • the optical switch according to the present disclosure is a fixing jig that receives at least one of the two ferrules and is engageable with the housing;
  • the fixture further includes a protrusion that engages with the housing,
  • the housing may be positioned relative to the fixing jig by the projection engaging with a locking piece of the housing.
  • the optical switch according to the present disclosure is a rotation mechanism that rotates at least one of the two ferrules about a central axis of the ferrule; an actuator that rotates the rotation mechanism at a constant angular step and stops the rotation mechanism at an arbitrary angular step;
  • the rotating mechanism may further include a bearing.
  • This disclosure makes it possible to provide an optical coupling section and optical switch that can achieve stable optical characteristics against external factors with low power consumption and in a more economical manner.
  • FIG. 1 shows an example of a schematic configuration of the present invention.
  • FIG. 2 is a front view of the end of the output ferrule.
  • FIG. 2 is a front view of the end of the input ferrule.
  • 1 is a diagram showing an optical coupling portion in a longitudinal direction.
  • FIG. 1 shows an example of the relationship between the excess loss and the clearance between the outer diameter of the ferrule and the inner diameter of the sleeve.
  • 3 shows the vicinity of an end of a ferrule in an optical coupling portion of the present invention.
  • 1 shows an example of the relationship between the angle between a cross section perpendicular to the central axis of the ferrule and the end face of a single mode optical fiber and the return loss.
  • 1 shows an example of the relationship of excess loss to the gap of an optical fiber.
  • 1 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.
  • 1 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.
  • 1 shows an example of the relationship between the core arrangement radius and excess loss due to a rotation angle deviation.
  • 3 shows a coupling form of the optical coupling portion of the present invention according to the first embodiment.
  • 13 illustrates a coupling form of an optical coupling portion of the present invention according to a second embodiment.
  • 13 illustrates a cross section of an input ferrule of an optical coupling portion of the present invention according to a second embodiment.
  • 13 illustrates a cross section of an input ferrule of an optical coupling portion of the present invention according to a second embodiment.
  • 3 shows a side view of the output side flange of the present invention in accordance with embodiment 1.
  • 13 illustrates a coupling form of an optical coupling portion of the present invention according to a third embodiment.
  • FIG. 1 is a diagram showing an example of an embodiment of the present invention.
  • the present invention makes it possible to switch the input side optical fiber S01 connected to the front-stage optical switch configuration section S00 to a specific port of the inter-optical switch optical fiber S02 in the front-stage optical switch configuration section S00, and to switch the port of the inter-optical switch optical fiber S02 to a desired output side optical fiber S04 in the rear-stage optical switch configuration section S03.
  • the present invention is an optical switch corresponding to the front-stage optical switch configuration section S00 and the rear-stage optical switch configuration section S03.
  • the front-stage optical switch configuration section S00 will be abbreviated as the optical switch S00
  • the rear-stage optical switch configuration section S03 will be abbreviated as the optical switch S03.
  • the optical switch S00 and the optical switch S03 are in a left-right inversion relationship and have the same configuration, so the detailed configuration will be shown below using the optical switch S00.
  • FIG. 2 is a block diagram showing a configuration according to an embodiment of the present invention.
  • the optical coupling unit S8 of the optical switch S00 is 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 a 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 having 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 a cross section of the ferrule; 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, and a predetermined gap is provided between the outer diameters of the first ferrule and the second ferrule and the inner diameter of the hollow portion so that the first ferrule and the second ferrul
  • the input optical fiber S1 is configured to be one single-core single-mode optical fiber, and the input ferrule S6 is the second ferrule.
  • the output optical fiber S9 is configured to be multiple single-core single-mode optical fibers, and the output ferrule S7 is 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.
  • the optical switch S00 shown in FIG. 2 has an optical coupling section S8 consisting 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 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 in the output ferrule S7.
  • the output ferrule S7 When light is incident from the input optical fiber S1, the output ferrule S7 is fixed and the input ferrule S6 is rotated to connect the input optical fiber S1 to any one of the output optical fibers S9, and the incident light can be output from one of the output optical fibers S9.
  • This optical switch S00 can be used as a 1xN relay type optical switch.
  • the output side ferrule S7 is fixed and the input side ferrule S6 is rotated, but as long as either the input side ferrule S6 or the output side ferrule S7 is fixed and the opposing fiber can be switched by rotating the opposing side, 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.
  • the optical switch S00 which fixes the output ferrule S7 and rotates the input ferrule S6.
  • the output ferrule S7 is fixed by a rotation stop mechanism (not shown) so that it does not rotate about its axis.
  • the actuator S3 rotates at any angle in response to a signal from the control circuit S4.
  • the input ferrule S6 rotates when the output of the actuator S3 is transmitted via the rotation mechanism S5.
  • the input ferrule S6 is provided with a certain amount of 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 by an axial misalignment adjustment mechanism (not shown) and to avoid excess loss due to axial misalignment.
  • the optical coupling unit S8 of the optical switch S00 is
  • the input side ferrule S6 and the output side ferrule S7 are A convex spherical end portion is provided in the direction of the central axis.
  • the tip of the input ferrule S6 and the tip of the output ferrule S7 are butted against each other.
  • FIG. 3 is a schematic diagram showing the end of the output side ferrule S7 according to an embodiment of the present invention from the front.
  • a plurality of optical fibers are bundled together and arranged inside a fiber hole S11 of diameter S21 provided in the center of the output side ferrule S7, and the core center of each of the output side optical fibers S9 is arranged on the circumference of a circle with a core arrangement radius Rcore relative to the center of the output side ferrule S7.
  • a dummy fiber S10 is arranged at the center and a total of six output side optical fibers S9 are arranged, but this is not limited as long as the core centers of the plurality of output side optical fibers S9 are arranged on the circumference of a circle having a core arrangement radius Rcore.
  • the dummy fiber S10 may be an optical fiber having the same strength and outer diameter as the output side optical fiber S9, and may be a fiber without a core, that is, a fiber that does not transmit light.
  • FIG. 4 is a schematic diagram showing the end of the input side ferrule S6 according to an embodiment of the present invention 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 side ferrule S6, and the core center of the input side optical fiber S1 is arranged on the circumference of a circle with a core arrangement radius Rcore relative to the center of the input side ferrule S6.
  • FIG. 4 is a schematic diagram showing the end of the input side ferrule S6 according to an embodiment of the present invention 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 side ferrule S6, and the core center of the input side optical fiber S1 is arranged on the circumference of a circle with a core arrangement radius Rcore relative to the center of the input side ferrule S6.
  • FIG. 4 is a schematic diagram showing the end of the input
  • the dummy fiber S10 may be any optical fiber that has the same strength and outer diameter as the input optical fiber S1, and may be a fiber that does not have a core, i.e., a fiber that does not transmit light.
  • 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 output optical fiber S9 and the input optical fiber S1.
  • the outer diameter of the dummy fiber S10 arranged at the center larger than 125 ⁇ m, it becomes possible to arrange six or more output optical fibers S9 on the circumference of a circle with a core arrangement radius Rcore.
  • each core of the output optical fiber S9 it is important to minimize the transmission loss of the optical coupling section S8, and it is desirable for each core of the output optical fiber S9 to have the same optical characteristics as the core of the input optical fiber S1 in that it has a mode field diameter similar to that of the core of the input optical fiber S1. It is also important to minimize excess loss due to axial misalignment, and it is desirable for the ferrule outer diameter S15 of the output ferrule S7 to be approximately the same as the ferrule outer diameter S15 of the input ferrule S6.
  • 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 and any optical fiber capable of communicating signal light in the communication wavelength band may be used.
  • FIG. 5 is a schematic diagram showing an optical coupling section S8 according to an embodiment of the present invention, viewed from 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 with a cylindrical sleeve S17 having a hollow portion with an inner diameter S16 that is approximately sub- ⁇ m larger than the outer diameter S15 of the ferrules, and a slight clearance C of approximately sub- ⁇ m is provided for the input ferrule S6 and the output ferrule S7 to control the axial misalignment within a certain tolerance range and not to interfere with the axial rotation of the input ferrule S6.
  • FIG. 6 is a diagram showing an example of the relationship between the excess loss T C and 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.
  • the axial misalignment of the fiber cores is a cause of excess loss. Since an increase in excess loss limits the total length of the optical path, it is necessary to reduce the axial misalignment of the fiber cores.
  • ⁇ 1 and ⁇ 2 are the mode field radii (unit: ⁇ m) of the input and output optical fiber S9 cores, respectively, and Fig. 6 is a diagram showing the loss when the mode field diameters of the input optical fiber S1 and the output optical fiber S9 cores are both 9 ⁇ m.
  • FIG. 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 has a convex spherical shape having a center point on the ferrule central axis AC .
  • the output side ferrule S7 of this embodiment has a dummy fiber S10 arranged at the center of the fiber hole S11, and the output side optical fiber S9 arranged around the dummy fiber S10.
  • the end faces of the output side optical fiber S9 and the dummy fiber S10 arranged in the output side ferrule S7 form the convex spherical shape of the end of the output side ferrule S7.
  • the output side ferrule S6 of this embodiment has a dummy fiber S10 arranged at the center of the fiber hole S11, and the input side optical fiber S1 and the dummy fiber S10 arranged around the dummy fiber S10.
  • the end faces of the input side optical fiber S1 and the dummy fiber S10 disposed in the output side ferrule S6 constitute the convex spherical shape of the end of the input side ferrule S6.
  • the dummy fibers S10 arranged in the input ferrule S6 and the output ferrule S7 are butted at their respective tips.
  • the input fiber S1 and the output fiber S9 are arranged at the position of the core arrangement radius Rcore from the ferrule central axis A C in the ferrule cross section.
  • the end faces of the input fiber S1 and the output fiber S9 are set back from their tips to prevent the end faces from coming into contact and being damaged when switching by rotation.
  • the angle ⁇ between the cross section perpendicular to the ferrule central axis A C and the end face of the single-core optical fiber is controlled at the end faces of the input fiber S1 and the output fiber S9 to suppress deterioration of signal characteristics due to reflection.
  • a convex spherical shape can be produced by using a polishing technique used in the production of general optical connectors.
  • the end faces of the dummy fibers S10 arranged on the respective ferrule central axes are butted against each other, but the arrangement is not limited thereto as long as the end faces of the input fiber S1 and the output fiber S9 do not come into contact with each other.
  • the amount of fiber retraction may be increased so that the end faces of the input side fiber S1 and the output side fiber S9 do not come into contact with each other when the input side ferrule S6 and the output side ferrule S7 are butted together.
  • Fig. 8 is a diagram showing 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 R.
  • 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, the signal characteristics will be deteriorated by reflection.
  • Equation 2 The relationship between the angle ⁇ (unit: degree) between the cross section perpendicular to the ferrule central axis A C and the end face of a single mode optical fiber and the return loss R (unit: dB) can be expressed by Equation 2.
  • n1 , ⁇ 1 , and ⁇ are the refractive index of the optical fiber, the mode field radius of the optical fiber core (unit: ⁇ m), and the wavelength of the propagating light in a vacuum (unit: ⁇ m), respectively.
  • R0 is the return loss at the flat end face, which can be expressed by the following equation 3.
  • n2 is the refractive index of the light receiving medium, that is, the refractive index of air.
  • the return loss R0 at the flat end face is 14.7 dB, and for example, by making the angle ⁇ between the cross section perpendicular to the ferrule central axis A C and the end face of the single mode optical fiber 4.5 degrees or more, a return loss R of 40 dB or more can be maintained. Furthermore, it is possible to further improve the reflection characteristics by processing a reflective coating on the fiber end face.
  • FIG. 9 is a diagram showing an example of the relationship of excess loss T G to gap G.
  • the relationship between the gap G (unit: ⁇ m) and excess loss T G (unit: dB) can be expressed by Equation 4.
  • ⁇ , n clad , ⁇ 1 , and ⁇ 2 are the wavelength of the propagating light in a vacuum (unit: ⁇ m), the refractive index of the cladding of the optical fiber, i.e., pure quartz, and the mode field radius of the cores of the input side optical fiber S1 and the output side optical fiber S9 (unit: ⁇ m), and Fig. 9 is a diagram showing the loss when the mode field diameters of the cores of the input side optical fiber S1 and the output side optical fiber S9 are both 9 ⁇ m.
  • the excess loss can be suppressed to 0.1 dB or less.
  • FIG. 10 is a diagram showing an example of the relationship between the radius of curvature Rcur of the convex spherical ferrule end face and the angle ⁇ between a cross section perpendicular to the ferrule central axis A C and the end face of a single mode optical fiber.
  • the relationship between the radius of curvature Rcur (unit: mm) of the convex spherical ferrule end face and the angle ⁇ (unit: degrees) between a cross section perpendicular to the ferrule central axis A C and the end face of a single mode optical fiber can be expressed by Equation 5 using the core arrangement radius Rcore (unit: ⁇ m).
  • FIG. 10 is a diagram showing the relationship between the angle ⁇ and the radius of curvature Rcur when the core arrangement radius Rcore is 125, 150, 200, and 250 ⁇ m. From Fig. 8, it can be seen that the angle ⁇ capable of maintaining a return loss R of 40 dB or more is 4.5 degrees or more, and a radius of curvature Rcur with an angle ⁇ of 4.5 degrees or more can be realized at a core arrangement radius Rcore of 250 ⁇ m or less.
  • the radius of curvature Rcur is adjusted to 1.5 mm or less, 1.9 mm or less, 2.5 mm or less, and 3.2 mm or less, respectively, so that the angle ⁇ becomes 4.5 degrees or more and a return loss R of 40 dB or more can be maintained.
  • a typical single mode optical fiber has an outer fiber diameter of 125 ⁇ m.
  • FIG. 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 can be expressed by Equation 6 using the radius of curvature Rcur (unit: mm) of the convex spherical ferrule end face and the angle ⁇ (unit: degrees) between a cross section perpendicular to the ferrule central axis AC and the end face of the single mode optical fiber.
  • the radius of curvature Rcur is adjusted to be 0.7 mm or more, 1.0 mm or more, 1.8 mm or more, and 2.8 mm or more, respectively, so that the distance D from the ferrule tip to the fiber end face is 11 ⁇ m or less, that is, the gap G is 22 ⁇ m or less, and the excess loss T G due to the gap can be suppressed to 0.1 dB or less as shown in FIG.
  • a typical single mode optical fiber has an outer fiber diameter of 125 ⁇ m.
  • a return loss R of 40 dB or more and an excess loss T of 0.1 dB or less can be achieved 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.
  • the optical coupling portion S8 of the optical switch S00 has 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 may be 0.7 mm or more and 3.2 mm or less.
  • the actuator S3 is a drive mechanism that rotates at any angle step by a pulse signal from the control circuit S4 and has a constant static torque for each angle step, and for example, a stepping motor is used. Note that the actuator S3 may use other methods as long as it rotates at any angle step by 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 pulse number of the pulse signal from the control circuit S4, and the angle step and static torque may be adjusted via a reduction gear.
  • the input side ferrule S6 in the optical coupling unit S8 is designed to rotate around the ferrule central axis A C , and therefore has a feature that the static torque required to hold the rotation angle of the input side ferrule S6 is applied by the actuator S3.
  • the static angular step number is characterized by being a natural number multiple of the number of cores having the same core arrangement radius Rcore in the output side optical fiber S9.
  • Equation 7 An example of the relationship of excess loss TR due to rotation angle misalignment with respect to core arrangement radius Rcore is shown in FIG. 12.
  • FIG. 12 is a diagram showing the relationship between core arrangement radius Rcore and excess loss TR due to rotation angle misalignment when the rotation angle misalignment ⁇ is 0.1 degrees, 0.15 degrees, 0.2 degrees, and 0.3 degrees.
  • the core arrangement radius Rcore is 125 ⁇ m, so according to FIG. 12, even with a rotation angle misalignment of 0.3 degrees, the excess loss TR due to rotation angle misalignment can be maintained at 0.1 dB or less.
  • a sleeve S17 is built into the inside of the fixing jig S27, and the input side ferrule S6 and the output side ferrule S7 are inserted into the sleeve S17 to align the ferrule central axes.
  • the output side ferrule S7 is fixed, and the input side ferrule S6 rotates within the sleeve S17 by the rotation mechanism S5 of the bearing S26 around the center of the ferrule cylinder as an axis. This rotates the core of the input optical fiber S1 inserted into the input ferrule S6, and switches the core of the output optical fiber S9 facing the input optical fiber S1.
  • the bearing S26 is made of, for example, zirconia, but other materials can be used as long as they can be manufactured with high dimensional accuracy.
  • the fixing jig S27 into, for example, a frame made of a hollow metal with low rigidity, it is possible to reduce the axial deviation of the input ferrule S6 caused by the axial wobble when the actuator S3 rotates.
  • FIG. 17 A side view of the output side flange S19 attached to the output side ferrule S7 is shown in Fig. 17.
  • the capillary S23 is arranged at a position where the fiber hole S30 of the output side ferrule S7 attached to the output side flange S19 and the ferrule central axis A C coincide with each other, and the capillary S23 is tapered in the longitudinal direction and the diameter of the tip is made close to the diameter of the fiber hole S30 of the output side ferrule S7, thereby preventing the output side optical fiber S9 from being caught by a step when being inserted into the output side ferrule S7, and further preventing the optical fiber from being broken.
  • the rotating flange S29 attached to the input side ferrule S6 is shown, but the shape of the inside of the flange is not limited to this as long as it is a shape that allows the optical fiber to be inserted into the fiber hole and a shape that allows the optical fiber to be protected when the optical coupling part is made.
  • the ends of two ferrules in which single-mode optical fibers are arranged parallel to and at the same distance from the central axis, are convex, 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 around its central axis, so that 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 caused by scratches on the end faces of the optical fibers due to contact.
  • the end faces of the opposing optical fibers are non-parallel to each other, the amount of light reflection can be reduced, making it possible to provide a more economical optical coupling unit and optical switch without the need for a reflective coating.
  • one of the input and output sides of the optical coupling section S8 that performs optical switching is made into an axially rotatable mechanism, so that it is possible to minimize the energy required by the actuator S3, i.e., the torque output, and to reduce power consumption. Also, the amount of optical axis deviation in directions other than the axial rotation of the input ferrule S6 is guaranteed by the sleeve S17 in the optical coupling section S8, making it possible to reduce loss.
  • the present invention does not include a collimator or special vibration isolation mechanism, and is composed of commonly used optical connection parts such as ferrules and sleeves, making it small and economical.
  • the present invention makes it possible to provide an optical coupling section and optical switch that can achieve stable optical characteristics against external factors such as temperature and vibration with low power consumption and in a more economical manner. As a result, it 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.
  • FIG. 14 is a schematic diagram showing the mating form of the optical coupling section S8 according to this embodiment.
  • the output side ferrule S7 is attached to the output side flange S19, and the output side flange S19 is attached to the fixing jig S27 with a fixing screw S25, and the axial direction and axial rotation direction are fixed.
  • the input side ferrule S6 is attached to the input side flange S18.
  • the input side flange S18 is attached to the fixing jig S27 with a removable fixing screw S25, and the axial direction and axial rotation direction are fixed. By loosening the fixing screw S25, the input side flange S18 becomes rotatable, and the input side ferrule S6 attached to the input side flange S18 can rotate accordingly.
  • the input side flange S18 may also have the structure shown in FIG. 15, as described later. At this time, a fixing screw (not shown) for fixing the axial direction may be provided separately.
  • the input side ferrule S6 has a ferrule outer diameter S15 smaller than that of the output side ferrule S7, is attached to a bearing S26, and rotates by the rotation mechanism S5 of the bearing S26.
  • the output side ferrule S7 is fixed and the input side flange S18 becomes rotatable, and the input side ferrule S6 rotates within the sleeve S17 around the center of the ferrule cylinder by the rotation mechanism S5 of the bearing S26. 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 opposite the input optical fiber S1.
  • 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, and the input ferrule S6 can freely rotate in the sleeve S17.
  • FIG. 15 also shows an example of using a fixed spring S28 as a method of fixing the input flange S18.
  • a groove as shown in FIG. 15 is provided in advance in the input flange S18, and the input flange S18 and the input ferrule S6 fixed thereto are fixed by clamping the tip of the fixed spring S28 in the groove.
  • the fixed spring S28 releases the fixed input ferrule S6 by applying a force in the direction of the arrow D S , and the input ferrule S6 can be rotated.
  • a control circuit S4 (not shown) that controls the actuator S3
  • a magnet or a solenoid may be used in addition to the fixing spring S28.
  • the output ferrule S7 of the optical coupling section S8 is not attached to the output flange S19, but to a pressing force imparting flange S31 to which a pressing device S32 is attached, which applies a pressing force in the direction in which the end faces of the input ferrule S6 and the output ferrule S7 butt against each other in the longitudinal direction of the ferrule.
  • the pressing device S32 holds the output ferrule S7 via the pressing force imparting flange S31.
  • the pressing device S32 is attached to the housing S33 by a stopper S34. A method for fixing the output ferrule S7 will be described below. Note that the contents other than those described below are the same as those of the first embodiment.
  • the optical coupling unit S8 is An optical coupling unit that couples single-core optical fibers S1 and S9 disposed in two ferrules S6 and S7 using a sleeve S17,
  • the output side ferrule S7 has a plurality of optical fibers arranged in a bundle shape in the fiber hole on the same circumference centered on the central axis of the ferrule,
  • the input ferrule S6 is rotatable around the ferrule central axis, The rotation of the output ferrule S7 is restricted.
  • the output side ferrule S7 is characterized in that the ends of the two ferrules are pressed in a direction to butt together.
  • the optical switch S00 has In the optical coupling section S8,
  • the connector is characterized by including a pressing device S32 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.
  • FIG. 18 is a schematic diagram showing the mating form of the optical coupling unit S8 according to this embodiment.
  • the input side ferrule S6 is attached to the rotating flange S29, the rotating flange S29 is provided with a bearing S26, and the input side ferrule S6 is attached to the fixing jig S27 with a fixing screw S25, and the axial direction is fixed.
  • the input side configuration of the optical coupling unit S8 according to this embodiment is not limited to this.
  • the input side ferrule S6 is attached to the input side flange S18, and the input side flange S18 is attached to the fixing jig S27 with a removable fixing screw S25, and the axial direction and axial rotation direction are fixed.
  • the fixing screw S25 By loosening the fixing screw S25, the input side flange S18 becomes rotatable, and the input side ferrule S6 attached to the input side flange S18 can also be rotated.
  • the input side ferrule S6 may have a ferrule outer diameter S15 smaller than that of the output side ferrule S7, a bearing S26 is attached, and the input side ferrule S6 may be rotated by the rotation mechanism S5 of the bearing S26.
  • a pressing force applying flange S31 is attached to the output side ferrule S7.
  • a pressing force applying device S32 is attached to the pressing force applying flange S31 in the longitudinal direction of the input side ferrule S6 and the output side ferrule S7, which applies a pressing force in the direction in which the end faces of the input side ferrule S6 and the output side ferrule S7 butt against each other.
  • the pressing device S32 presses the pressing force applying flange S31 to the left in FIG. 18.
  • the output side ferrule S7 to which the pressing force applying flange S31 is attached is also pressed to the left.
  • the pressing device S32 is also attached to a stopper S34 and fixed in the rotational direction.
  • the stopper S34 is attached to the housing S33, and therefore the pressing device S32 is fixed 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. This fixes the output side ferrule S7 attached to the pressure applying flange S32 in the rotational direction relative to the housing S33.
  • the pressing device S32 may be a bellows-type, slit-type, disk-type coupling, or the like.
  • the material of the pressing device S32 may be a metal such as stainless steel or a polymeric compound such as rubber, and it is not limited to these as long as it holds the output ferrule S7 so that it does not rotate and applies a pressing force in the direction in which the end faces of the input ferrule and the output ferrule butt together.
  • the housing S33 accommodates the output side ferrule S7, the pressing force applying flange S31, and the pressing device S32 in the following order: pressing device S32, pressing force applying flange S31, output side ferrule S7.
  • the fixing jig S27 and the housing S33 may be mated by a mating method used for general optical connectors. That is, the housing S33 is inserted and fixed in the fixing jig S27 by providing a mating mechanism for an optical connector plug in an optical connector in the housing S33 and providing a mating mechanism for an optical connector adapter in an optical connector in the fixing jig S27.
  • a protrusion S35 is provided on the surface of the fixing jig S27 that contacts the housing S33 on the inside, 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 and the locking piece S36.
  • the stopper S34 may be formed integrally with the housing S33.
  • the presser S32 is fixed in the rotational direction relative to the housing S33 by the stopper S34, and the presser S32 is fixed to the fixing jig S27 via the stopper S34 and the housing S33.
  • the output side ferrule S7 attached to the pressing force applying flange S31 fixed to the presser S32 is also fixed to the housing S32 and the fixing jig S27.
  • the presser S32 that presses the output side ferrule S7 can be accurately fixed to the housing S33 using the stopper 34, so that it is possible to suppress deterioration of the optical characteristics.
  • two stoppers S34 are provided, but the scope of the present disclosure is not limited to this.
  • the number of stoppers S34 may be only one, or may be three or more.
  • 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.
  • the pressing device S32 contracts to apply a pressing force in the longitudinal direction of the ferrule. Specifically, as the pressing device S32 is pressed to the left, the pressing force applying flange S31 is pressed to the left.
  • the output side ferrule S7 to which the pressing force applying flange S31 is attached is also pressed to the left.
  • the pressing force is applied to the ferrule end face by pressing the output side ferrule S7 with the pressing device S32, but the scope of the present disclosure is not limited to this.
  • 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 to apply a pressing force to the ferrule end face.
  • the presser S32 that can be attached to the stopper S34, it is possible to regulate the rotation of the output side ferrule S7 and apply a pressing force to the ferrule end face, which consumes low power and is economical.
  • 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.
  • the present invention can provide an optical coupling section and optical switch that can achieve stable optical characteristics against external factors with low power consumption and in a more economical manner.
  • optical coupling section and optical switch disclosed herein can be applied to the optical communications industry.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Couplings Of Light Guides (AREA)
PCT/JP2023/027583 2023-07-27 2023-07-27 光結合部及び光スイッチ Pending WO2025022649A1 (ja)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0282212A (ja) * 1988-09-20 1990-03-22 Fujitsu Ltd 光スイッチ
JPH0291609A (ja) * 1988-09-29 1990-03-30 Fujitsu Ltd 光スイッチ
JPH0328816A (ja) * 1989-01-19 1991-02-07 Alcatel Nv 光ファイバスイッチ
WO2022018783A1 (ja) * 2020-07-20 2022-01-27 日本電信電話株式会社 光スイッチ

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0282212A (ja) * 1988-09-20 1990-03-22 Fujitsu Ltd 光スイッチ
JPH0291609A (ja) * 1988-09-29 1990-03-30 Fujitsu Ltd 光スイッチ
JPH0328816A (ja) * 1989-01-19 1991-02-07 Alcatel Nv 光ファイバスイッチ
WO2022018783A1 (ja) * 2020-07-20 2022-01-27 日本電信電話株式会社 光スイッチ

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