Closure

Abstract

A closure (10) is provided with: a housing (11) having an accommodation space (14) for a connection part (13) in which optical transmission paths (2, 3) are mutually connected; and a cover (12) that is configured so as to be attachable to a road surface (1), that is attached to the housing (11), and that covers the accommodation space (14) from above. The housing (11) includes a bottom wall (16) located below the accommodation space (14). The bottom wall (16) is provided with passages (17) through which the optical transmission paths (2, 3) pass through the bottom wall (16).

Description

closure

[0001] The present disclosure relates to closures installed at connection points in optical communication networks.

[0002] Closures are installed at connection points of optical access networks. The closures accommodate and protect the connection portions of the optical cables that are interconnected. Patent Document 1 discloses an optical cable closure as related art.

[0003] Japanese Patent Application Publication No. 10-170733

[0004] When working on closures installed on the road surface, workers are forced to bend over, and working in a bent over position for long periods of time places a great physical strain on the workers.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a closure that can reduce the physical burden on workers who perform various tasks on the closure.

[0006] A closure according to one aspect of the present disclosure comprises a housing having an accommodation space for a connection portion that connects optical transmission paths to each other, and a lid portion that is configured to be attachable to a road surface and covers the accommodation space from above, the housing having a bottom wall located below the accommodation space, and the bottom wall having a passage portion through which the optical transmission path passes through the bottom wall.

[0007] According to the present disclosure, a closure can be provided that allows various tasks to be performed in a posture that places a relatively light physical burden, such as a standing position.

[0008] FIG. 1 is a side view showing an example of an installation environment of a closure according to an embodiment of the present disclosure. FIG. 2 is a side cross-sectional view showing an example of a configuration of a closure according to an embodiment. FIG. 3 is a plan view showing an example of a configuration of a closure (housing) according to an embodiment. FIG. 4 is a side cross-sectional view showing another example of a configuration of a closure according to an embodiment. FIG. 5A is one of diagrams showing an example of an installation process of a closure according to an embodiment in stages. FIG. 5B is one of diagrams showing an example of an installation process of a closure according to an embodiment in stages. FIG. 5C is one of diagrams showing an example of an installation process of a closure according to an embodiment in stages. FIG. 6 is a perspective view of a tubular portion according to an embodiment. FIG. 7A is a side cross-sectional view of an example of a tubular portion. FIG. 7B is a cross-sectional view showing an example of use of the tubular portion shown in FIG. 7A. FIG. 8 is a side cross-sectional view of another example of a tubular portion.

[0009] A closure 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 convenience of description, the X direction, Y direction, and Z direction are defined. These three directions are mutually orthogonal. The Z direction is the up-down direction, and is assumed to coincide with, for example, the vertical direction. However, the Z direction is not limited to being parallel to the vertical direction. In other words, the Z direction may be inclined with respect to the vertical direction, as long as the relative positional relationship between two objects aligned in the Z direction is not reversed. The X direction and the Y direction are orthogonal to the Z direction and are also orthogonal to each other. The X direction and the Y direction are, for example, a horizontal direction.

[0010] The closure according to this embodiment is an optical relay box (optical terminal block box) for interconnecting optical cables serving as optical transmission paths. Specifically, the closure accommodates a splice section where optical fibers (optical fiber cores) serving as optical transmission paths drawn from an optical cable are connected to each other, and protects the splice section. The optical fibers connected to each other at the splice section are not limited to optical fibers drawn from the optical cable (see FIG. 2 ), but may also be relay optical fibers (e.g., optical patch cords) optically connected to the optical fibers of the optical cable via relay connectors (see FIG. 4 ). In either case, an optical transmission path leading to the splice section is constructed, and the ends of the optical cables are held by a holding section provided in the closure or the relay connector described above.

[0011] Fig. 1 is a side view showing an example of an installation environment of a closure 10 according to this embodiment. Fig. 2 is a side cross-sectional view showing an example of the configuration of the closure 10. Fig. 3 is a plan view showing an example of the configuration of the closure 10.

[0012] First, the installation environment of the closure 10 will be described. As shown in Fig. 1, the closure 10 is installed at a connection point (branch point) of an optical access network, and interconnects optical cables 4 and 5 under a road surface 1. Specifically, the closure 10 is installed in a connection box 53 provided on the road surface 1 as a connection point (branch point). Note that the number of optical cables interconnected by the closure 10 may be more than the two illustrated.

[0013] The optical cable 4 includes a plurality of optical fibers (optical fiber cores) 6 covered by an outer jacket (sheath). The optical cable 4 (each optical fiber 6) constitutes at least a portion of the optical transmission path 2 leading to the connection part 13. The optical cable 5 includes a plurality of optical fibers (optical fiber cores) 7 covered by an outer jacket (sheath). The optical cable 5 (each optical fiber 7) constitutes at least a portion of the optical transmission path 3 leading to the connection part 13. For ease of explanation, each of the plurality of optical fibers 6, 7 is shown by a single line in each drawing.

[0014] The road surface 1 is the surface of the foundation structure on which the optical cables 4 and 5 are laid. For example, the road surface 1 is the surface of a road on which people and / or vehicles pass, the bottom of a street drain, the floor of a communication facility or utility conduit, etc. In any case, the road surface 1 is located at a position sufficiently lower than the reach of a worker in a standing position, such as at the feet of a worker.

[0015] Cable ducts 50 and 51 are buried in the road surface 1. An optical cable 4 is laid in the cable duct 50, and an optical cable 5 is laid in the cable duct 51. A connecting box 53 is provided between the cable duct 50 and the cable duct 51.

[0016] The connecting box 53 is a vertical hole formed in the road surface 1. The connecting box 53 is formed, for example, during the construction of the road surface 1 or by excavating (digging) the road surface 1 after construction. The inner peripheral surface 53a of the connecting box 53 is formed in a cylindrical shape extending downward from the road surface 1, and a cylindrical internal space 54 is formed inside the connecting box 53. The ends of the cable ducts 50, 51 open at the inner peripheral surface 53a. The excess lengths 4a, 5a of the optical cables 4, 5 pulled out from the cable ducts 50, 51 are accommodated in the internal space 54 in a wound state.

[0017] The dimensions (volume) of the internal space 54 are set to a value that can accommodate the closure 10 and the excess lengths 4 a, 5 a of the optical cables 4, 5 without causing bending loss. The shape of the internal space 54 as viewed from the Z direction is, for example, circular. That is, the internal space 54 is formed in a cylindrical shape extending in the Z direction. However, as long as the internal space 54 having the above-mentioned volume is formed, the cross-sectional shape may be any shape, and may be, for example, rectangular.

[0018] The opening 9 is formed on the road surface 1. The internal space 54 of the connecting box 53 is connected to the external space on the road surface 1 through the opening 9. As described below, the lid portion 12 of the closure 10 is placed on the opening 9. When viewed from the Z direction, the opening 9 has a cross-sectional shape complementary to that of the lid portion 12 of the closure 10. The depth of the opening 9 along the Z direction is equal to or slightly deeper than the thickness of the lid portion 12 along the Z direction. Therefore, when the lid portion 12 is placed on the opening 9, the upper surface 12a of the lid portion 12 is positioned approximately flush with the road surface 1.

[0019] The closure 10 is installed in the connecting manhole 53. For example, with the housing 11 of the closure 10 positioned in the internal space 54 of the connecting manhole 53, the lid portion 12 of the closure 10 is attached to the opening 9 in the road surface 1. The lid portion 12 attached to the opening 9 covers (closes) the internal space 54 of the connecting manhole 53 from above.

[0020] As shown in Figure 2, the closure 10 comprises a housing 11 and a lid 12. The lid 12 is attached to the housing 11 and is a plate-like member that covers the storage space 14 from above. The lid 12 is configured to be attachable to the road surface 1. For example, the lid 12 is attached to the opening 9 and fixed to the road surface 1 by fixing parts such as screws or a well-known locking mechanism. The thickness of the lid 12 is approximately the same as the depth of the opening 9.

[0021] The shape of the lid portion 12 is arbitrary as long as it covers the entire housing 11 when viewed from the Z direction. As an example, the lid portion 12 may be formed in a disk shape (see FIG. 3). In this case, the opening 9 is also formed in a circular shape. When viewed from the Z direction, the circular lid portion 12 covers the entire internal space 54 of the connecting manifold 53. Therefore, forming the lid portion 12 in a circular shape can prevent the closure 10 from falling into the internal space 54. The lid portion 12 may be formed integrally with the housing 11. In this case, the flange portion 24 described below is omitted. Instead, the lid portion 12 is provided with an access window (not shown) that communicates with the external space and the storage space 14.

[0022] The housing 11 is a hollow box that is open at the top and has an interior space 14 for accommodating a connection portion 13 that connects the optical fibers 6 and 7 (optical transmission paths 2 and 3). The housing 11 has, for example, a substantially rectangular parallelepiped shape. However, the three-dimensional shape of the housing 11 is not limited to a rectangular parallelepiped.

[0023] The housing 11 includes a sidewall 15 that surrounds the storage space 14. The sidewall 15 is, for example, a flat plate parallel to the Z direction. When viewed from the Z direction, the sidewall 15 may be rectangular (see FIG. 3) or circular (see FIG. 6). A flange 24 is provided on an upper portion 15a of the sidewall 15. The flange 24 protrudes outward from the sidewall 15 along a plane perpendicular to the Z direction (i.e., the XY plane) and functions as a mounting surface for the lid 12.

[0024] The housing 11 is located below the accommodation space 14 and has a bottom wall (bottom surface) 16 that is continuously connected to the lower portion 15b of the side wall 15 (i.e., formed integrally with the side wall 15). The bottom wall 16 is, for example, a flat plate that is perpendicular to the Z direction. The bottom wall 16 is provided with a passage 17 through which the optical transmission paths 2 and 3 pass. For example, as shown in FIG. 2 , optical cables 4 and 5 serving as the optical transmission paths 2 and 3 are inserted from below the housing 11 into the accommodation space 14. In this case, the passage 17 is composed of a plurality of insertion portions 18 and 19.

[0025] The insertion portion 18 includes a through-hole 20 having a hole diameter large enough to allow the optical cable 4 to be inserted therethrough, and a holding portion 22 that holds the end portion 4b of the optical cable 4. The end portion 4b of the optical cable 4 is inserted into the through-hole 20 from below the bottom wall 16 and is exposed to the accommodation space 14. The holding portion 22 is provided on the bottom wall 16 and clamps the end portion 4b exposed in the accommodation space 14, thereby holding the end portion 4b. This prevents the optical cable 4 from falling off (disconnecting) from the housing 11.

[0026] The insertion portion 19 includes a through-hole 21 having a hole diameter large enough to allow the optical cable 5 to be inserted therethrough, and a holding portion 23 that holds the end portion 5b of the optical cable 5. The end portion 5b of the optical cable 5 is inserted into the through-hole 21 from below the bottom wall 16 and is exposed to the accommodation space 14. The holding portion 23 is provided on the bottom wall 16 and clamps the end portion 5b exposed in the accommodation space 14, thereby holding the end portion 5b. This prevents the optical cable 5 from falling off (disconnecting) from the housing 11.

[0027] A plurality of optical fibers 6 are exposed from the end 4b of the optical cable 4 by removing the jacket of the optical cable 4. Similarly, a plurality of optical fibers 7 are exposed from the end 5b of the optical cable 5 by removing the jacket of the optical cable 5. The optical fibers 6 are connected to corresponding optical fibers 7 at connecting portions 13. The optical fibers may be connected by any of fusion splicing, mechanical splicing, and connector connection.

[0028] The connection portion 13 is placed on, for example, a tray 25 supported by the housing 11. In this case, the tray 25 has a structure (not shown) for holding the connection portion 13. Alternatively, the tray 25 may function as a base (stage), and the connection portion 13 may be fixed to the tray 25 with fixing parts such as screws. Note that the closure 10 may include a plurality of connection portions 13 and trays 25 for the connection portions 13. In this case, the plurality of trays 25 are stacked in the Z direction.

[0029] The housing 11 may be provided with a seal member 26 that ensures watertightness of the storage space 14. For example, as shown in FIG. 2 , a groove 24b may be formed in the upper surface 24a of the flange 24, and an O-ring 27 serving as the seal member 26 may be attached to this groove 24b. In this case, the groove 24b is formed around the entire circumference of the flange 24 and opens toward the lid 12. The O-ring 27 is sandwiched between the inner surface of the groove 24b and the lid 12. Note that the above-mentioned groove may also be formed in the lid 12. In this case, the upper surface 24a of the flange 24 is a flat surface without a groove.

[0030] 2, the insertion portion 18 (19) may include a bushing 28 (29) as a sealing member 26 attached to the through-hole 20 (21). In this case, the bushing 28 (29) adheres closely to the outer sheath of the optical cable 4 (5) inserted into the bushing 28 (29) and to the inner circumferential surface of the through-hole 20 (21).

[0031] The sealing member 26 may be formed of a filler such as a sealant. In this case, the filler is filled between the outer jacket of the optical cable 4 (5) inserted into the through hole 20 (21) and the inner circumferential surface of the through hole 20 (21), and hardens while maintaining its elasticity. In either case, the above-mentioned sealing member ensures watertightness of the storage space 14 and prevents water from entering the housing 11.

[0032] 4 is a side cross-sectional view showing another example of the configuration of the closure according to the embodiment. As shown in Fig. 4, the passing portion 17 may be formed of relay connectors 30, 31 attached to the bottom wall 16 and relaying the optical transmission lines 2, 3. That is, in this case, the relay connectors 30, 31 are attached to the bottom wall 16 instead of the insertion portions 18, 19.

[0033] When the relay connector 30 (31) is attached to the bottom wall 16, the optical connector 32 (33) attached to the optical cable 4 (5) is connected to the relay connector 30 (31). When the optical connector 32 (33) is connected to the relay connector 30 (31), the optical connector 32 (33) is locked to the relay connector 30 (31) by a well-known locking mechanism. This prevents the optical cable 4 (5) from falling off (disconnecting) from the housing 11.

[0034] The optical transmission paths 2, 3 from the relay connectors 30, 31 to the connection section 13 are constructed by optical patch cords. The optical patch cords are, for example, pre-connected to each relay connector 30 (31) and integrated with the connector. Therefore, for the optical cables 4, 5, the worker only needs to connect the optical cables 4, 5 to the closure 10. In other words, the work of guiding the ends 4b, 5b of the optical cables 4, 5 into the housing space 14 is omitted, and the worker can concentrate on connecting the optical patch cords.

[0035] 5A to 5C are diagrams illustrating an example of a step-by-step installation process for the closure 10. In this process, the optical fiber 6 of the optical cable 4 and the optical fiber 7 of the optical cable 5 are connected in the closure 10, and then the closure 10 is installed in the opening 9 in the road surface 1.

[0036] Figure 5A shows an example of the initial state. As shown in Figure 5A, an opening 9 and a connecting box 53 are formed in the road surface 1. Cable ducts 50 and 51 are buried under the road surface 1. Furthermore, optical cables 4 and 5 are laid in the cable ducts 50 and 51, respectively.

[0037] The excess lengths 4a, 5a of the optical cables 4, 5 are exposed from the cable ducts 50, 51 and are placed in the internal space 54 of the connection box 53. The closure 10 is temporarily placed at a position sufficiently high above the road surface 1, i.e., at a location such as a workbench (not shown) where a worker can perform the connection work of the optical fibers 6 and 7 while standing.

[0038] First, the worker removes the excess lengths 4a and 5a from the connecting manhole 53 and inserts the ends 4b and 5b of the optical cables 4 and 5 into the passage sections 17 (insertion sections 18 and 19) of the housing 11. Next, the jacket of the end section 4b is removed to expose the optical fiber 6. Similarly, the jacket of the end section 5b is removed to expose the optical fiber 7.

[0039] The optical fibers 6 and 7 are spliced ​​together through a splicing process using a splicing tool such as a fusion splicer and housed within the splicing section 13. After all splicing processes are completed, the cover 12 is attached to the housing 11 from above, as shown in FIG. 5B . In this manner, the operations from inserting the optical cables 4 and 5 into the housing 11 to attaching the cover 12 to the housing 11 can be performed on a workbench (not shown). In other words, various operations on the closure 10, such as interconnecting the optical fibers 6 and 7, can be performed in a relatively physically light position, such as standing. Furthermore, the optical cables 4 and 5 are inserted through or connected to the underside of the closure 10 (i.e., the bottom wall 16 of the housing 11). Therefore, compared to conventional closures in which optical cables are inserted through or connected horizontally, the horizontal expansion of the space required to accommodate the excess length can be suppressed.

[0040] After the various operations on the closure 10 are completed, the lid portion 12 is attached to the opening 9 with the housing 11 facing the connecting box 53, as shown in Figure 5C. As a result, the housing 11 and the excess length portions 4a, 5a are housed in the internal space 54 of the connecting box 53. The thickness of the lid portion 12 may be approximately the same as the depth of the opening 9. In this case, the lid portion 12 does not excessively protrude from the road surface 1, nor is it excessively recessed. In other words, it is possible to prevent interference with moving objects such as people and vehicles moving on the road surface 1.

[0041] FIG. 6 is a perspective view of the tubular portion 35 according to the embodiment. As shown in FIG. 6, the closure 10 according to the embodiment may further include the tubular portion 35. The tubular portion 35 is formed in a hollow cylindrical shape extending in the Z direction. For example, the tubular portion 35 has a hollow, tubular side wall 36 and is attached to the lower part of the housing 11. As shown in FIG. 5C, when the closure 10 is installed on the road surface 1, the tubular portion 35 is located below the internal space 54 and surrounds the excess portions 4a, 5a of the optical cables 4, 5 serving as optical transmission paths placed below the housing 11.

[0042] 6 , slits 38, 39 may be formed in the side wall 36 that constitutes the tubular portion 35. The slits 38, 39 allow the optical cables 4, 5 to be inserted from the outside to the inside of the side wall 36. For example, the excess length 4 a of the optical cable 4 pulled out from the cable duct 50 can be placed inside the side wall 36 through the slit 38. Similarly, the excess length 5 a of the optical cable 5 pulled out from the cable duct 51 can be placed inside the side wall 36 through the slit 39.

[0043] The cylindrical portion 35 expands and contracts in the Z direction (up and down direction) depending on the position of the housing 11. In other words, the length (total length) of the side wall 36 along the Z direction changes depending on the position of the housing 11. The maximum length of the side wall 36 along the Z direction is set to a value that at least reaches from the bottom wall 16 of the housing 11 to the bottom wall 16 of the connecting box 53 (see FIG. 7B ) when the housing 11 is placed on a workbench (not shown).

[0044] To achieve a change in the length of the tubular portion 35 along the Z direction, the sidewalls 36 may be made of, for example, a flexible fabric or resin sheet. Alternatively, the sidewalls 36 may be made of a stretchable material. Such a material is, for example, a polymer material such as silicone rubber. To maintain the drooping state of the tubular portion 35, a weight (not shown) may be attached to the bottom edge of the tubular portion 35.

[0045] During the connection of the optical cables 4, 5, the cylindrical portion 35 surrounds the excess lengths 4a, 5a (see FIG. 7B ) and protects the excess lengths 4a, 5a from raindrops and other water droplets and dust. For example, when the connection of the optical cables 4, 5 is being performed in rainy weather, adhesion of water droplets to the excess lengths 4a, 5a can be suppressed, eliminating unnecessary work such as removing the water droplets.

[0046] The cylindrical portion 35 hangs down due to its own weight, and its lower end remains within the connecting box 53. For example, the lower portion of the cylindrical portion 35 (e.g., cylindrical piece 42A described below) contacts the bottom surface of the connecting box 53 regardless of the position of the closure 10. Therefore, a space (space 45 shown in FIG. 7B) surrounding the excess length portions 4a, 5a can be secured without providing an external device for expanding or contracting the cylindrical portion 35.

[0047] 6, the cylindrical portion 35 may include a guide portion 40. The guide portion 40 is a cylindrical member extending in the Z direction. The guide portion 40 is configured to be expandable and contractible in the Z direction, for example, by using the same configuration or material as the side wall 36.

[0048] The guide portion 40 is surrounded by the side wall 36. Therefore, the outer peripheral surface 41 of the guide portion 40, together with the side wall 36, forms a double-wall structure, with the excess portions 4a, 5a housed between them. The guide portion 40 maintains the radius of curvature of the excess portions 4a, 5a surrounded by the side wall 36 at a value equal to or greater than the minimum bending radius specified for the optical cables 4, 5. To maintain this value of the radius of curvature, for example, the radius of curvature of the guide portion 40 is set to a value equal to or greater than the minimum bending radius described above.

[0049] When the cylindrical portion 35 includes the guide portion 40, the excess portions 4 a, 5 a are housed between the side wall 36 and the outer peripheral surface 41 of the guide portion 40. Because the radius of curvature of the outer peripheral surface 41 is set to the above-mentioned value, even if the excess portions 4 a, 5 a are bent, the radius of curvature of the excess portions 4 a, 5 a remains equal to or greater than the specified minimum bending radius. Therefore, an increase in bending loss of the excess portions 4 a, 5 a within the cylindrical portion 35 can be suppressed.

[0050] 7A is a side cross-sectional view of an example of the tubular portion 35. As shown in FIG. 7A, the tubular portion 35 (i.e., the side wall 36 of the tubular portion 35) may be composed of multiple tubular pieces 42 that are relatively movable in the Z direction. Each tubular piece 42 is made of, for example, a resin sheet. The multiple tubular pieces 42 are formed into a hollow cylindrical shape and arranged concentrically. For convenience of explanation, it is assumed that the tubular portion 35 is composed of five tubular pieces 42. The tubular pieces 42 are designated 42A, 42B, 42C, 42D, and 42E in order from the innermost tubular piece 42 to the outermost tubular piece 42.

[0051] 7A shows the state when the length of the tubular portion 35 along the Z direction is at its minimum. Each tubular piece 42 has a tubular main body 42a, an outer flange 42b, and an inner flange 42c. Slits 38, 39 (see FIG. 6) are formed in each tubular piece 42. As shown in FIG. 7A, the innermost tubular piece 42A does not necessarily have to have the inner flange 42c.

[0052] The length of the main body 42a along the Z direction is approximately the same for all of the multiple cylindrical pieces 42. However, the diameter D1 of the main body 42a varies from one cylindrical piece 42 to another. Therefore, the cylindrical pieces 42 can be arranged concentrically so that the cylindrical pieces 42 with larger diameters D1 are located on the outside.

[0053] The outer flange 42b is an annular plate provided on the upper edge 42d of the main body 42a and perpendicular to the Z direction. The outer flange 42b is located outside the main body 42a. In other words, the outer flange 42b has a predetermined thickness and extends radially outward from the upper edge 42d of the main body 42a. As shown in FIG. 7A, the outer diameter (maximum diameter) of the outer flange 42b is D2.

[0054] The inner flange 42c is an annular plate provided on the lower edge 42e of the main body 42a and perpendicular to the Z direction. The inner flange 42c is located inside the main body 42a. In other words, the inner flange 42c has a predetermined thickness and extends radially inward from the lower edge 42e of the main body 42a. As shown in FIG. 7A, the inner diameter (minimum diameter) of the inner flange 42c is D3.

[0055] The outer diameter D2 of the outer flange 42b of one tubular piece 42 is smaller than the diameter D1 of the main body 42a of the outer tubular piece 42, and is larger than the inner diameter D3 of the inner flange 42c of the outer tubular piece 42. For example, as shown in Fig. 7A, the outer diameter D2 of the outer flange 42b of tubular piece 42B is smaller than the diameter D1 of the main body 42a of the outer tubular piece 42C, and is larger than the inner diameter D3 of the inner flange 42c of tubular piece 42C.

[0056] Therefore, for example, when tubular piece 42C is pulled up, inner flange 42c of tubular piece 42C comes into contact with outer flange 42b of tubular piece 42B from below. If tubular piece 42C is pulled up further from this state, tubular piece 42B is also pulled up. In other words, the multiple tubular pieces 42 are configured to move in stages along the Z direction (up and down direction).

[0057] Fig. 7B is a cross-sectional view showing an example of use of the cylindrical portion 35 shown in Fig. 7A. As shown by the dotted line in Fig. 7B, in the initial state, the closure 10 is positioned so that the excess portions 4a and 5a are housed inside the cylindrical piece 42A, and is placed at or near the opening 9.

[0058] Of the multiple cylindrical pieces 42, only cylindrical piece 42E, which is located on the outermost side, is attached to the housing 11. Furthermore, cylindrical piece 42A rests on the bottom surface of connecting box 53 due to its own weight. When the housing 11 is pulled up, cylindrical piece 42E moves upward first. Then, depending on the position of the housing 11, cylindrical pieces 42D, 42C, and 42B move upward in this order.

[0059] Most of the excess length portions 4a, 5a, i.e., the portions that are pulled up during the connection work, are surrounded by the multiple tubular pieces 42 that make up the tubular portion 35. Furthermore, the space 45 (see FIG. 7B ) surrounded by these pieces is substantially isolated from the space outside the tubular portion 35, regardless of the expansion or contraction of the tubular portion 35. In other words, the excess length portions 4a, 5a can be protected from water droplets such as rainwater and dust.

[0060] Fig. 8 is a side cross-sectional view of another example of the tubular portion 35. As shown in Fig. 8, the tubular portion 35 may have a bellows structure 43. For example, the bellows structure 43 is configured by a foldable tubular sheet 44 that extends in the Z direction. The sheet 44 may be made of resin or cloth. In either case, the sheet 44 may be partially cut out to provide slits 38, 39 (see Fig. 6).

[0061] The present disclosure is not limited to the above-described embodiments, but is defined by the claims, and includes all modifications within the meaning and scope equivalent to the claims.

[0062] DESCRIPTION OF SYMBOLS 1 Road surface 2, 3 Optical transmission path 4, 5 Optical cable 4a, 5a Excess length 6, 7 Optical fiber (optical fiber core) 9 Opening 10 Closure 11 Housing 12 Lid 13 Connection portion 14 Storage space 15 Side wall 16 Bottom wall 17 Passing portion 18, 19 Insertion portion 20, 21 Through hole 30, 31 Relay connector 32, 33 Optical connector 35 Cylindrical portion 36 Side wall 38, 39 Slit 40 Guide portion 42 Cylindrical piece 43 Bellows structure 50, 51 Cable duct 53 Connection box 54 Internal space

Claims

1. A closure comprising: a housing having an accommodation space for a connection portion that connects optical transmission lines to each other; and a lid configured to be mountable to a road surface and covering said accommodation space from above, said housing having a bottom wall located below said accommodation space, and said bottom wall having a passage portion through which said optical transmission lines pass through said bottom wall.

2. The closure according to claim 1, further comprising a cylindrical section which surrounds the excess length of the optical transmission line placed below the housing and which expands and contracts in the vertical direction according to the position of the housing.

3. The closure according to claim 2, wherein the cylindrical portion is formed with a slit that allows the optical transmission path to be inserted into the cylindrical portion.

4. A closure as claimed in claim 2 or 3, wherein the cylindrical portion includes a guide portion that maintains the radius of curvature of the optical transmission path surrounded by the cylindrical portion at a value equal to or greater than the minimum bending radius specified for the optical transmission path.

5. A closure as set forth in claim 2, wherein said tubular portion is composed of a plurality of tubular pieces capable of relative movement in the up and down direction.

6. The closure according to claim 2, wherein the cylindrical portion has a bellows structure.

7. The closure according to claim 1, wherein the lid portion is formed in a disk shape.