Optical connector

Abstract

An optical connector (1) is provided with: a plug (10) that holds an optical fiber (11); an adapter (20) that holds an optical fiber (21) having an end surface that is to be butted against the end surface of the optical fiber (11), and holds the plug (10) to be movable in the insertion / removal direction of the plug; and an expansion material (30) that is positioned between the plug (10) and the adapter (20) in the insertion / removal direction in a state in which the plug (10) is inserted into the adapter (20), and that can be expanded by moisture.

Description

Optical Connector

[0001] The present disclosure relates to optical connectors.

[0002] Patent Document 1 discloses an optical communication line monitoring system that can identify closures that have become abnormal due to flooding. Non-Patent Document 1 proposes a small closure that can be installed on the road surface to accommodate cables laid in grooves formed in the road surface or mat.

[0003] JP 2010-212767 A

[0004] Kobayashi et al., “Fundamental Study of Planar Closure for Wiring on Road Surface,” International Wire & Cable. Symposium (IWCS), 2023, 14-4

[0005] Compared to closures for installation on roads, closures for installation on roads are smaller in size. However, existing water ingress detection modules are relatively large and difficult to fit into small closures. This means that water ingress detection is often impossible in small closures, hindering efficient optical cable maintenance.

[0006] The present disclosure aims to provide an optical connector that can detect water immersion in a device without being limited by the size of the device.

[0007] An optical connector according to one aspect of the present disclosure comprises a plug that holds a first optical fiber, an adapter that holds a second optical fiber having an end face that abuts against the end face of the first optical fiber and holds the plug so that it can move in the insertion / removal direction of the plug, and an expansion material that expands when exposed to moisture and is positioned between the plug and the adapter in the insertion / removal direction when the plug is inserted into the adapter.

[0008] According to the present disclosure, it is possible to provide an optical connector that can detect the ingress of water into a device without being limited by the dimensions of the device.

[0009] FIG. 1 is a diagram illustrating the configuration of an optical connector according to this embodiment. FIG. 2 is a top view of the optical connector shown in FIG. 1. FIG. 3 is a diagram illustrating a state in which the optical connector is submerged in water. FIG. 4 is a diagram illustrating measurement results using an OTDR. FIG. 5 is a diagram illustrating the configuration of an optical connector according to a first modified example of this embodiment. FIG. 6 is a top view of the optical connector shown in FIG. 5. FIG. 7 is a diagram illustrating a state in which the optical connector is submerged in water when a latch portion is provided. FIG. 8 is a diagram illustrating the configuration of an optical connector according to a second modified example of this embodiment. FIG. 9 is a diagram illustrating measurement results using an OTDR when a stopper portion is provided.

[0010] An optical connector 1 according to an embodiment of the present disclosure will be described below. Note that common parts in each drawing are given the same reference numerals, and redundant description will be omitted. For ease of explanation, mutually orthogonal X, Y, and Z directions are defined. The Z direction is the removal direction of the plug 10 when inserted into or removed from the adapter 20 (see FIG. 1). The Z direction is also the extension direction of the central axes of the optical fibers 11, 21 and through-hole 24 held in the optical connector 1. The Y direction is, for example, the protrusion direction (see FIG. 1) of the protrusion 13 (described below). The X direction is the width direction of the plug 10 and the adapter 20.

[0011] FIG. 1 is a diagram illustrating the configuration of an optical connector 1 according to this embodiment. FIG. 2 is a top view of the optical connector 1 shown in FIG. 1. The optical connector 1 connects an optical fiber (first optical fiber) 11 and an optical fiber (second optical fiber) 21 to each other. As will be described later, the optical connector 1 has a function for detecting water intrusion. The optical connector 1 is used, for example, in a closure (optical terminal box) for installation on a road surface. As will be described later, it is possible to determine whether the inside of the closure is flooded by measurement using an OTDR (Optical Time Domain Reflectometer).

[0012] As shown in Figure 1, the optical connector 1 includes a plug 10, an adapter 20, and an expansion material 30. The plug 10 is a housing that holds an optical fiber 11. A ferrule 12 is attached to the plug 10. The ferrule 12 holds the optical fiber 11 with an end face 11a (see Figure 3) of the optical fiber 11 exposed toward the adapter 20. The cross-sectional shape of the plug 10 perpendicular to the Z direction may be rectangular, circular, or another shape.

[0013] A protrusion 13 is provided on the side surface 10a of the plug 10. The protrusion 13 protrudes in the Y direction (i.e., toward the inner surface 23b of the housing 23) and forms a front surface 13a and a rear surface 13b. The front surface 13a faces the inner bottom surface 23a of the housing 23. Meanwhile, the rear surface 13b is located on the opposite side of the body of the protrusion 13 from the front surface 13a. As shown in FIG. 2 , the width W1 of the protrusion 13 along the X direction is less than the width W2 between the inner surfaces 23b of the housing 23 along the X direction (i.e., the width of the space formed by the housing 23). For example, if the width W1 is smaller than the width W2, a space (passage) leading to the expansive material is formed between the inner surface 23b and the protrusion 13 in the X direction. Adjusting the width of this space allows for adjustment of the ease of water penetration into the expansive material 30. Therefore, for example, it is possible to avoid a situation where, even though the closure housing the optical connector 1 is submerged in water, water does not enter the optical connector 1, and the OTDR measurement described below determines that the closure is not submerged in water.

[0014] The adapter 20 is a housing that holds the optical fiber 21 and accommodates the plug 10. The adapter 20 has an accommodating portion 23 for the plug 10. The accommodating portion 23 holds the plug 10 movably in the Z direction and the opposite direction (i.e., the insertion / removal direction). The accommodating portion 23 has a cross-sectional shape complementary to that of the plug 10 and opens in the Z direction. When the plug 10 is inserted into the accommodating portion 23, at least a portion of the inner bottom surface 23a of the accommodating portion 23 faces the tip surface (tip portion) 10b of the plug 10. The inner bottom surface 23a is provided with a through-hole 24 extending in the Z direction. A ferrule 22 is attached to the through-hole 24. The ferrule 22 holds the optical fiber 11 with the end surface 21a (of the optical fiber) of the optical fiber 21 (see FIG. 3) exposed toward the plug 10.

[0015] A tapered surface 25 is formed around the through hole 24 on the inner bottom surface 23a. The tapered surface 25 is formed, for example, as a conical surface whose diameter decreases as it approaches the ferrule 22. In this case, the central axis of the conical surface coincides with the central axis of the through hole 24. When the plug 10 is inserted into the accommodating portion 23, a space 31 is formed between the tapered surface 25 and the front end surface 10b of the plug 10. The expansion material 30 is filled in this space 31 in advance. The tapered surface 25 may have the function of guiding the ferrule 12 into the through hole 24 when the plug 10 is inserted into the accommodating portion 23.

[0016] By inserting the plug 10 into the housing portion 23, the ferrule 12 is inserted into the through hole 24. The ferrule 12 abuts against the ferrule 22 in the through hole 24, whereby the end face 11a of the optical fiber 11 is butted against the end face 21a of the optical fiber 21, resulting in optical connection. The end face of the ferrule 12, together with the end face 11a of the optical fiber 11, is polished into a convex curved surface (so-called PC polishing) or polished into a convex curved surface inclined at a predetermined angle with respect to the central axis of the optical fiber 11 (so-called APC polishing).

[0017] For ease of explanation, the portion where the end face 11 a of the optical fiber 11 and the end face 21 a of the optical fiber 21 are butted together will be referred to as the connection portion 26. The connection portion 26 may be filled (immersed) in a hydrophobic refractive index matching agent (so-called matching oil) as a waterproofing material, thereby preventing liquids such as water from entering between the end faces 11 a and 21 a.

[0018] The expansion material 30 is a so-called water-absorbing material that expands upon absorbing moisture. The expansion material 30 is formed, for example, from a polymer material that is water-absorbent and expandable. When the plug 10 is inserted into the adapter 20, the expansion material 30 is positioned between the plug 10 and the adapter 20 in the Z direction. For example, the expansion material 30 is installed in at least one of the space 31 formed by the tapered surface 25 and the space 32 between the inner bottom surface 23a of the housing portion 23 and the front surface 13a of the protrusion 13. The amount of expansion material 30 is adjusted to a value that allows the plug 10 to move in the Z direction, taking into account its expansion rate.

[0019] However, the mounting position of the expansion material 30 is arbitrary as long as the expansion material 30 can move the plug 10 in the Z direction by its expansion when the optical fibers 11, 21 are butted against each other. For example, the tapered surface 25 and the protruding portion 13 may be omitted, and the expansion material 30 may be mounted in the space formed between the inner bottom surface 23 a of the housing portion 23 and the tip surface 10 b of the plug 10.

[0020] 3 is a diagram illustrating a state in which the optical connector 1 is submerged in water. When the optical connector 1 is submerged in water, water penetrates into the tip of the plug 10 through the gap between the plug 10 and the housing portion 23 of the adapter 20. The water that penetrates into the tip of the plug 10 is absorbed by the expansion material 30, causing the expansion material 30 to expand. If water penetration continues, the expansion material 30 continues to expand, occupying the space in which the expansion material 30 is provided, and then pressing the plug 10 in the Z direction. When the pressure caused by the expansion of the expansion material 30 exceeds the frictional force between the plug 10 and the adapter 20, the plug 10 shifts in the Z direction. As a result, the end face 11a of the optical fiber 11 and the end face 21a of the optical fiber 21 move away from each other in the Z direction.

[0021] 4 is a diagram showing changes in the measurement results obtained by the OTDR. As an example, it is assumed that the optical connector 1 is connecting optical fibers 11 and 21 together in a closure (not shown) installed in the middle of an optical communication network.

[0022] In order to check the connection status between the optical fibers 11 and 21, an inspection is performed using an OTDR. The OTDR propagates probe light through the optical fiber in which the optical connector 1 is used and measures the intensity of the reflected light. The wavelength of the probe light may be shorter than the wavelength of light in the communication wavelength band. In this case, the inspection can be performed without affecting communication. Furthermore, since the connection loss of the optical fiber increases as the wavelength becomes shorter, it becomes easier to check for abnormal connection loss. In other words, sensitivity to abnormal connection loss increases.

[0023] When the conditions inside the closure are normal, i.e., when the optical connector 1 is not submerged in water, the probe light passes normally between the optical fibers 11 and 21. Therefore, as shown by the solid line in Figure 4, the OTDR shows normal reflection and attenuation due to connection loss at the position of the optical connector 1.

[0024] On the other hand, if the inside of the closure is submerged in water and water enters the optical connector 1, as described above, the expansion material 30 expands, causing the end face 11a to move away from the end face 21a. Therefore, as shown by the dashed line in Figure 4, the OTDR shows an increase in loss at the position of the optical connector 1. This allows the user of the OTDR to confirm that the closure has been submerged in water.

[0025] The optical connector 1 according to this embodiment has the same dimensions as conventional optical connectors. Therefore, it occupies a small amount of space and can be applied to, for example, small closures to which conventional water ingress detection modules cannot be applied. In other words, this embodiment provides an optical connector that can detect water ingress in a device without being limited by the device's dimensions. Furthermore, water ingress detection is possible without opening the closure, enabling efficient maintenance.

[0026] Fig. 5 is a diagram illustrating the configuration of an optical connector 1 according to a first modified example of this embodiment. Fig. 6 is a top view of the optical connector 1 shown in Fig. 5. As shown in Fig. 5, the optical connector 1 may further include a latch portion 15. For example, as shown in Fig. 6, the latch portion 15 is provided between two protrusions 13 in the X direction. The latch portion 15 maintains the inserted state of the plug 10 in the adapter 20.

[0027] The latch portion 15 includes an elastically deformable arm portion 16 that includes a claw portion 17, and a protrusion 18 that engages with the claw portion 17. The arm portion 16 is provided on one of the side surface 10a of the plug 10 and the inner surface 23b of the adapter 20, and the protrusion 18 is provided on the other of the side surface 10a of the plug 10 and the inner surface 23b of the adapter 20. In the example shown in FIG. 5 , the arm portion 16 is provided on the side surface 10a of the plug 10, and the protrusion 18 is provided on the inner surface 23b of the adapter 20.

[0028] Arm portion 16 is configured to be flexible toward a structure that supports arm portion 16. Claw portion 17 protrudes in a direction opposite to the direction of bending of arm portion 16. Protrusion 18 protrudes from the structure that supports protrusion 18.

[0029] When the plug 10 is inserted into the housing 23, the claw 17 comes into contact with the protrusion 18. As the plug 10 is further inserted, the arm 16 bends, causing the claw 17 to climb over the protrusion 18. When the claw 17 climbs over the protrusion 18, the arm 16 is released from its bending and returns to its original shape. The claw 17 and the protrusion 18 each have a flat surface that is approximately perpendicular to the Z direction, and after the claw 17 climbs over the protrusion, these flat surfaces face each other. This restricts movement of the plug 10 in the Z direction. In other words, the inserted state of the plug 10 in the adapter 20 is maintained. In this inserted state, the end face 11a abuts against the end face 21a.

[0030] 7 is a diagram illustrating a state in which the optical connector 1 equipped with the latch portion 15 is submerged in water. As described above, when water enters the optical connector 1, the expansion material 30 expands. At this time, the expanded expansion material 30 presses the arm portion 16 of the latch portion 15 toward the structure supporting the arm portion 16. In the example shown in FIG. 7, the expanded expansion material 30 presses the arm portion 16 toward the plug 10.

[0031] The pressure of the expansion material 30 causes the arm portion 16 to bend toward the plug 10. As the expansion material 30 continues to expand and the amount of bending of the arm portion 16 increases, the engagement between the claw portion 17 and the protrusion portion 18 is released, and the plug 10 becomes movable in the Z direction. In other words, the inserted state of the plug 10 maintained by the latch portion 15 is released by the pressure of the expanded expansion material 30.

[0032] Under normal conditions when the optical connector 1 is not submerged in water, the latch portion 15 prevents the plug 10 from being removed. Therefore, under normal conditions, even if unexpected vibrations or the like occur, the butt joint between the end faces 11a, 21a, i.e., the optical coupling between the optical fibers 11, 21, is maintained. On the other hand, if the optical connector 1 is submerged in water, the latch portion 15 releases the inserted state of the plug 10, and the plug 10 moves in the Z direction. Therefore, an abnormal increase in connection loss can be confirmed by an OTDR or the like, and repairs of the closure or the like can be recommended.

[0033] FIG. 8 illustrates the configuration of an optical connector 1 according to a second modification of this embodiment. FIG. 9 illustrates changes in OTDR measurement results when a stopper portion 19 is provided. As shown in FIG. 8 , the optical connector 1 may further include a stopper portion 19. The stopper portion 19 limits the distance between the end face 11 a of the optical fiber 11 and the end face 21 a of the optical fiber 21 to a range of connection loss that allows cascade connection. However, the stopper portion 19 also allows movement of the plug 10, which increases connection loss when submerged in water. In other words, the stopper portion 19 limits the Z-direction movement distance of the plug 10 relative to the adapter 20 to a distance that allows detection of attenuation of the probe light in the optical connector 1 and maintains the intensity of the probe light at a value that can be used in other downstream optical connectors.

[0034] The stopper portion 19 is located at a position overlapping the protrusion 13 of the plug 10 when viewed from the Z direction. For example, the stopper portion 19 is provided so as to face a part of the rear surface 13b of the protrusion 13. As long as this condition is met, the shape of the stopper portion 19 is arbitrary. For example, the stopper portion 19 may be a small piece extending in the X and Y directions, or a pin extending in the Y direction.

[0035] The stopper portion 19 may be attached to the adapter 20 later (see FIG. 8 ), or may be formed integrally with the adapter 20. In the latter case, for example, the stopper portion 19 has a dimension that allows it to elastically deform in a direction parallel to the Z direction, and allows the plug 10 to be inserted into the accommodating portion 23 while restricting excessive movement of the plug 10 by the expansion material 30.

[0036] As described above, even when the expansion material 30 expands due to water infiltration, the movement distance of the plug 10 along the Z direction remains within the above-mentioned range. Therefore, excessive increase in the gap between the end faces 11a and 21a is suppressed, and the probe light can be introduced to other optical connectors located downstream of the optical fiber 11 in the propagation direction of the probe light (i.e., cascade-connected). Therefore, as shown in FIG. 9 , the OTDR can be used to determine the water infiltration status of closures, etc., in other optical connectors 100. For example, as shown in FIG. 9 , even if the connection loss of the optical connector 1 increases due to water infiltration, the increase can be suppressed to a certain level. Therefore, the probe light can be introduced to the downstream optical connector 100. FIG. 9 indicates that the optical connector 100 is normal, i.e., the closures, etc. are not submerged in water.

[0037] REFERENCE SIGNS LIST 1 optical connector 10 plug 10a side surface 10b tip surface 11 optical fiber (first optical fiber) 11a end surface 12 ferrule 13 protrusion 13a front surface 13b rear surface 15 latch portion 16 arm portion 17 claw portion 18 convex portion 19 stopper portion 20 adapter 21 optical fiber (second optical fiber) 21a end surface 22 ferrule 23 storage portion 23a inner bottom surface 23b inner surface 24 through hole 25 tapered surface 26 connection portion 30 expansion material 31 space 32 space 100 optical connector

Claims

1. An optical connector comprising: a plug that holds a first optical fiber; an adapter that holds a second optical fiber having an end face that butts against the end face of the first optical fiber and holds the plug so that it can move in the insertion / removal direction of the plug; and an expansion material that expands when exposed to moisture and is located between the plug and the adapter in the insertion / removal direction when the plug is inserted into the adapter.

2. The optical connector according to claim 1, further comprising a stopper portion that keeps the distance between the end face of the first optical fiber and the end face of the second optical fiber within a range of connection loss that allows cascade connection.

3. The optical connector according to claim 1, wherein the portion where the end face of the first optical fiber and the end face of the second optical fiber are butted together is filled with a waterproof material.

4. An optical connector as described in claim 1, wherein the adapter includes a receiving section into which the plug is inserted, the receiving section including an inner bottom surface facing the tip of the plug, the inner bottom surface having a through hole into which a ferrule that holds the second optical fiber is attached, a tapered surface is formed around the through hole on the inner bottom surface, and the expansion material is mounted in at least the space formed by the tapered surface.

5. An optical connector according to claim 1, wherein the adapter includes a receiving portion into which the plug is inserted, the plug includes a protrusion that protrudes from a side surface of the plug onto the inner surface of the receiving portion, and the width of the protrusion in a direction perpendicular to the insertion / removal direction is smaller than the width of the space formed by the receiving portion.

6. An optical connector according to any one of claims 1 to 5, further comprising a latch portion that maintains the plug inserted into the adapter, and the inserted state maintained by the latch portion is released by the pressure of the expanded expansion material.

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