KR101207001B1 - Optical cable connecting apparatus suitable for junction box of a train communication system - Google Patents

Abstract

PURPOSE: An optical cable connecting apparatus is provided to fix an optical cable using a stopper or a fixing protrusion and to easily observe the inner side by using a housing of transparent plastic material. CONSTITUTION: An optical cable connecting apparatus comprises a first connecting member. The first connecting member comprises a housing(100), an optical cable connecting part, a fixing wedge inserting part, and a sliding part. The optical cable connecting part is installed to be extended from one side of the housing to the other side. A part of the housing comprises an opening. The fixing wedge inserting part penetrates the upper side and the lower side of the housing. A fixing wedge is inserted on the fixing wedge inserting part in order to be slid in a longitudinal direction. The sliding part is formed at one side of a slider and comprises a stopper. The stopper is inserted into the opening and fixes an optical cable. A combining means unites the first connecting member and a second connecting member.

Description

OPTICAL CABLE CONNECTING APPARATUS SUITABLE FOR JUNCTION BOX OF A TRAIN COMMUNICATION SYSTEM}

The present invention relates to an optical cable connection device, and more particularly, to an optical cable connection device suitable for use in a junction box of a train communication system.

The train communication system refers to a system that transmits and receives various data necessary for operating a train, either inside or outside a train or between passenger cars of a train. Recently, the amount of electronic devices and data used in train communication systems such as cameras, DVRs, NVRs, display devices, and AP devices has increased significantly.

Accordingly, the selection of the data transmission medium of the train communication system is becoming increasingly important. The train is resistant to vibrations and external shocks due to its characteristics, and is used by a large number of users, which has advantages in security, and is easy to install and maintain. It is appropriate to be used.

Since trains are connected to each other, it is necessary to transmit signals between parking lots and subordinate cars. Conventional communication lines were used to transmit signals between trains, but there was a problem because the reference voltages were significantly different between the vehicles. In particular, in the case of an electric railway vehicle, the power level for each vehicle that is drawn in and converted from the feeder line is very different, and thus it is difficult to transmit and receive signals in inter-vehicle communication.

In order to solve this problem, there is an example of introducing optical fiber to vehicle-to-vehicle communication. However, since the optical fiber is made of glass, the parts connected by the connector at the connection part between the cars often cause cracks due to the vibration of the car, which causes communication failure.

The connector technology used for the connection of a general optical cable is known as described in Korean Utility Model 20-0314299.

An object of the present invention is to provide an optical cable connecting device that is resistant to vibration and external shock.

Furthermore, an object of the present invention is to provide an optical cable connecting device that can be easily coupled and separated.

Furthermore, it aims at providing the optical cable connection device which is easy to install and maintain.

According to one aspect of the present invention, a train communication system is constructed using a plastic optical fiber. Plastic optical fiber is resistant to vibrations, so it is also resistant to vibrations at the connections between trains.

According to another aspect of the present invention, there is provided an optical cable connecting device for use in an inter-vehicle connection in a train communication system using a plastic optical fiber. An optical cable connecting apparatus according to an aspect includes a first connecting member and a second connecting member having a structure symmetrical to each other, the first connecting member and the second connecting member is installed extending from one side of the housing, the other side of the housing to the other side And a portion thereof includes an opening.

According to another aspect, the first connecting member and the second connecting member are provided in the optical cable connecting portion for providing a passage through which the optical cable is inserted, connected to the fixing chain insertion hole formed through the upper and lower surfaces of the housing, the sliding in the longitudinal direction to the fixing chain insertion opening It is inserted so as to be narrowed from the top to the lower end of the fixed taper, installed in contact with the fixed collar inside the housing, the slider sliding in the transverse direction as the fixed chain slides in the longitudinal direction, the inner peripheral surface of the housing Sliding guide which is installed, guides the sliding of the slider, formed on one side of the slider, a sliding portion including a stopper is inserted into the opening to secure the optical cable as the slider is sliding, the first connecting member and the second connection Engaging means for engaging the member.

In addition, the coupling means has a portion inserted and bonded to the optical cable connecting portion of the first connecting member, the remaining portion is inserted into the optical cable connecting portion of the second connecting member to couple the first connecting member and the second connecting member, and inserted into the optical cable connecting portion Ferrules to align the fiber optics can be used.

In addition, the ferrule is formed on the inner circumferential surface of the ferrule, and may include a locking step for aligning the optical cable.

In addition, the fixing wedge is installed in the lower portion of the fixing wedge, it may include a wedge fixing hook for fixing the fixing wedge to the housing.

In addition, the optical cable connecting portion is formed on the inner peripheral surface of the optical cable connecting portion, it may include an optical cable fixing projection for preventing the optical cable is drawn out.

As plastic optical cables are applied to train communication systems, power savings can be achieved compared to conventional UTP-like lines. In addition, plastics are eco-friendly materials, which significantly reduce carbon dioxide emissions compared to UTP cables. In addition, plastic optical cable has advantages of being more durable, reliable communication, and light weight than other conventional cables.

According to the optical cable connecting device according to the present invention, the optical cable can be firmly fixed by using the stopper and the fixing projection, and thus, the optical cable is secured against vibration and external shock.

In addition, it can be quickly separated by the coupling means, it is convenient to install or maintain.

1 is a diagram schematically illustrating a train optical communication system according to an exemplary embodiment.
FIG. 2 is a schematic cross-sectional view of an optical cable connecting apparatus according to the exemplary embodiment of FIG. 1.
3 is a perspective view of an optical cable connecting apparatus according to the embodiment of FIG. 1.
4 is a front view of the optical cable connecting apparatus according to the embodiment of FIG. 1.
5 is a diagram illustrating a coupling relationship between an optical cable connecting portion and a slider according to the exemplary embodiment of FIG. 1.
6 is a side view of the optical cable connecting apparatus according to the embodiment of FIG. 1.
FIG. 7 is a diagram illustrating a state in which the slider is slid so as to contact the optical cable connection part according to the exemplary embodiment of FIG. 1.

The foregoing and further aspects of the present invention are described in detail through the embodiments described with reference to the accompanying drawings.

Plastic optical cable is generally characterized by having a large core diameter, strong bending, good mobility and flexibility, strong vibration and external shock, and easy installation and maintenance.

On the other hand, the plastic optical cables of the train communication system are interconnected through the optical cable connection device. As described above, trains are frequently subjected to vibrations or external shocks, and each passenger car can be separated when necessary due to periodic inspections, etc., and therefore, a commonly used optical cable connecting device as described in Korean Utility Model No. 20-0314299 There is a difficulty in using it as it is. Therefore, the countermeasure against this should be considered.

Since the train is composed of a plurality of passenger cars that are separated from each other, an optical cable connection box is installed for each passenger car to connect each passenger car with an optical cable. More specifically, the optical cables are interconnected using an optical cable connecting device provided inside the optical cable contact enclosure.

However, as described above, the vibration and external shocks are frequent, and due to the characteristics of the train in which the passenger car is often separated, it is difficult to use a conventional optical cable connecting device as it is.

1 is a diagram schematically illustrating a train optical communication system according to an exemplary embodiment. As shown, a train optical communication system according to an embodiment includes a parking amount including a wireless transceiver for transmitting and receiving data wirelessly from the outside, and network equipment for transmitting a signal received from the wireless transceiver to each vehicle through a plastic optical cable; The vehicle may include a variance vehicle including a switch for distributing a parking amount and a signal transmitted / received to a train surveillance camera and an imaging device.

In one embodiment, the wireless transceiver that may be installed in the main vehicle may be a device that transmits and receives a packet to and from the access point in a wireless Internet, for example, WIFI. The network equipment included in the parking amount and transmitting and receiving data signals to each vehicle may be, for example, optical switch equipment. In one embodiment, an information display device that can be viewed, for example, by a train driver, may be connected to the optical switch equipment of the parking amount. The network equipment that can be installed in the slave vehicle can be an optical switch equipment, for example. Equipment connected to network equipment in a slave vehicle may include, for example, a surveillance camera for train security, a digital video recorder for storing surveillance camera images on-site, and an information display device for displaying broadcast or advertising images transmitted from the outside. Can be.

Signal transmission between the main vehicle and the slave vehicle is via a plastic optical cable. All signal cables of each vehicle are integrated in the junction box. In addition to the communication line in this embodiment, the connection enclosure may integrate other communication lines or power lines. In one embodiment, the signal transmission between the trains can be enabled by connecting the connection devices exposed to the junction box of both trains via a connection cable.

2 is a schematic sectional view schematically showing an optical cable connecting apparatus according to an embodiment which may be applied to such a connection enclosure. 3 is a perspective view of an optical cable connecting apparatus according to the embodiment of FIG. 1. 4 is a front view of the optical cable connecting apparatus according to the embodiment of FIG. 1. 5 is a diagram illustrating a coupling relationship between an optical cable connecting portion and a slider according to the exemplary embodiment of FIG. 1. 6 is a side view of the optical cable connecting apparatus according to the embodiment of FIG. 1. FIG. 7 is a diagram illustrating a state in which the slider is slid so as to contact the optical cable connection part according to the exemplary embodiment of FIG. 1.

The optical cable contact device according to an embodiment of the present invention includes a first connecting member and a second connecting member having a structure symmetrical to each other, the first connecting member and the second connecting member is the housing, the other side from one side of the housing An optical cable connecting portion which extends to and is provided with an opening having a portion thereof, and provides a passage through which the optical cable is inserted and connected, a fixing chain insertion slot formed through the upper and lower surfaces of the housing, and a longitudinal direction to the fixing chain insertion slot Inserted so as to slide, tapered fixed wedge to narrow the width from the top to the bottom, installed in contact with the fixed wedge inside the housing, slider sliding in the horizontal direction as the fixed wedge slides in the longitudinal direction, the inner peripheral surface of the housing Slider guide, which is installed in the guide to guide the sliding of the slider, formed on one side of the slider He said, as the slider is sliding comprises coupling means for coupling the sliding portion, the first connecting member and the second coupling member comprises a stopper for fixing an optical cable is inserted into the opening.

The optical cable connection device 10 according to an embodiment is formed by combining the first connection member 20 and the second connection member 30 as shown in FIGS. 2 and 3. The first connection member 20 and the second connection member 30 are symmetrical to each other and include the same components therein. Therefore, hereinafter, the first coupling member 20 and the second coupling member 30 will be described together with respect to the first connection member 20.

The first connection member 20 may include a housing 100, an optical cable connection part 200, a fixing chain inserting port 400, a fixing chain 500, a sliding part 600, and the like as one of the connecting members of the optical cable connecting device. Can be.

As shown in FIG. 2, the housing 100 serves as a case in which various components are fixedly installed therein. The housing 100 may be made of, for example, plastic, and in particular, may be made of a transparent plastic material to check whether there is an abnormality inside the apparatus without separating the housing 100. However, the present invention is not limited thereto, and the housing 100 may be manufactured using various materials other than plastic.

The optical cable connection part 200 is a passage through which the plastic optical cable 300 is inserted and connected to each other. As shown in FIG. 2, the optical cable connection part 200 extends from one side of the housing 100 to the other side of the housing 100. Is installed. In addition, as shown in FIG. 4, one or more fixing parts 210 may be formed on the outer circumferential surface of the optical cable connection part 200 and attached and fixed to the inner circumferential surface of the housing 100.

In the optical cable connecting device 10 according to an embodiment, as shown in FIG. 2, two optical cable connecting parts 200 disposed in parallel to each other are installed in the housing 100, but the present invention is not limited thereto. The optical cable connection part 200 can be installed freely according to a user's needs.

The optical cable connection part 200 may include various elements as necessary. For example, the optical cable connection part 200 may include an optical cable inlet 220, an opening 230, and a ferrule insertion groove 240.

The optical cable inlet 220 is an inlet through which the plastic optical cable 300 is inserted, and is formed at one end of the optical cable connection part 200 as illustrated in FIG. 2. In addition, the optical cable inlet is formed to be tapered so that the diameter of the front end portion is large and the diameter of the rear end portion is small, so that the plastic optical cable 300 can be smoothly drawn in.

The opening 620 is a passage through which the stopper 630 to be described later is inserted, and is formed by opening a portion of the optical cable connection part 610 as shown in FIG. 5.

The ferrule insertion groove 240 is a groove into which the ferrule 700 to be described later is inserted, and is formed at the other end of the optical cable inlet 220 as shown in FIG. 2 and has a step corresponding to the shape of the ferrule 700. It may have a shape.

In the train optical communication system according to an embodiment, since the trains are frequently vibrated or externally impacted and the passenger cars may be separated from time to time, the characteristics of these trains should be considered when manufacturing the optical cable connection device.

To this end, the optical cable connecting device 10 according to an embodiment is provided with a plastic optical cable inserted into the optical cable connecting device 10 by installing a fixing chain inserting port 400, a fixing chain 500, a sliding unit 600, and the like ( 300).

The fixing chain insertion hole 510 is a passage into which the fixing chain 700 to be described later is inserted, and as shown in FIG. 6, the fixing chain 700 of the housing 500 may pass between the optical cable connecting portions 610. It is formed through the upper and lower surfaces.

In the optical cable connecting device 10 according to an exemplary embodiment, since two optical cable connecting parts 200 are installed, the fixing cable 500 is formed by the optical cable connecting parts 200 by forming the fixing chain inserting holes 400 between the optical cable connecting parts 200. 200) can be applied to all.

The fixing chain 500 is a member for sliding and supporting the slider 610 to be described later, as shown in Figure 6 is inserted to be slidable in the longitudinal direction along the fixing chain insertion opening 400. In addition, the fixing chain 500 has the shape of a square pillar, the width of the top and bottom is the same when viewed from the front, but can be manufactured in a tapered shape so that the width of the top is larger than the bottom when viewed from the side.

In addition, steps may be formed at both ends of the fixing chain 500 to prevent the fixing chain 500 from being separated to the outside.

The sliding part 600 is a member for fixing the plastic optical cable inserted into the optical cable connection part 200, and may include a slider 610, a slider guide 620, and a stopper 630.

The slider 610 corresponds to the body of the sliding part 600, and is installed inside the housing 100 to contact the fixing chain 500 as shown in FIG. 6. Two sliders 610 may be installed in the slider 610, one between the fixing chain 500 and each optical cable connection part 200, but is not limited thereto.

Looking at the sliding process of the slider 610 in more detail as follows.

As shown in FIG. 7, when the fixing chain 500 is slid downward, the contact surface of the slider 610 which is in contact with the fixing chain 500 is connected to the optical cable connecting unit 200 by the tapered inclined surface of the fixing chain 500. Force is transmitted in the direction. Accordingly, the slider is slid in the direction of the optical cable connection part 200 to be in contact with the optical cable connection part 200.

When the fixed chain 500 is slid upward, the fixed chain 500 and the slider 610 are no longer in contact with each other and are separated from each other. On the other hand, if a compression spring (not shown) is provided between the two sliders 610, even if the fixed chain 500 is sliding upward, the fixed chain 500 and the slider 610 by the elastic force of the compression spring is It is effective because it can maintain the contact state not to be separated from each other.

In addition, in order to increase the contact surface between the slider 610 and the fixing chain 500 as much as possible, as shown in FIG. 6, one side of the slide 610 in contact with the fixing chain 500 is inclined surface of the fixing chain 500. It may be formed as a tapered inclined surface to correspond to.

In addition, in order to increase the contact surface between the slider 610 and the optical cable connection part 200 as much as possible, as shown in FIG. 6, one side of the slider 610 contacting the optical cable connection part 200 is formed on the outer circumferential surface of the optical cable connection part 200. It may be formed as a curved surface corresponding to.

The slide guide 620 guides the movement of the slider 610 so that the slider 610 can be stably slid, and as shown in FIG. 6, the inner circumferential surface of the housing 100 is in contact with the upper and lower ends of the slider 610. Fixed to

The stopper 630 is a member for fixing the plastic optical cable 300 introduced into the optical cable connecting portion 200 and is formed on one side of the slider 810 in contact with the optical cable connecting portion 610. The stopper 630 may be formed in various shapes and numbers as necessary. For example, as shown in FIG. 5, the stopper 630 is formed in two rows of teeth having a vertical shape on the curved surface formed on the slider 610. Can be.

When the slider 610 is slid, the stopper 630 is inserted into the optical cable connecting portion 200 as shown in FIGS. 6 and 7 through the opening 220 to press and fix the plastic optical cable 300 from the side. .

That is, the optical cable connecting device 10 according to an embodiment fixes the plastic optical cable 300 through the slider 610 and the stopper 630, the fixing chain 500 is the slider 610 and the stopper 630 Hold firmly to prevent flow. As a result, the plastic optical cable 300 is prevented from being drawn out to the outside even when vibration or external shock or external force is applied to the train.

In addition, the plastic optical cable 300 can be easily connected and dismantled by sliding the fixing chain 500 without performing complicated connection and dismantling operations, which facilitates installation or maintenance.

Meanwhile, as described above, the second connection member 30 has a shape that is symmetrical with the first connection member 20 and includes the same components as the first connection member 20 therein. Since the optical cable connecting device 10 according to an embodiment is formed by coupling the first connection member 20 and the second connection member 30 to each other through a connection member coupling means, the first connection member ( 20 and the coupling relationship between the second connection member 30 will be described.

The connecting member coupling means is a means for coupling the first connecting member 20 and the second connecting member 30 to each other, and is installed on the first connecting member 20 and the second connecting member 30, respectively. The coupling member coupling means is not particularly limited in kind, but for example, the ferrule 700 may be used as the coupling member coupling means.

The ferrule 700 is a cylindrical member, as shown in FIG. 4, a portion of the ferrule 700 is inserted into the ferrule insertion groove 240 of the first connection member 20 and the second connection member 30, respectively. 20 and the second connection member 30 is coupled. In addition, the plastic optical cable 300 to be introduced into both ends is also performed to align the plastic optical cable 300 so that it can be stably connected. The material of the ferrule 700 is not particularly limited, but may be made of, for example, stainless steel, polymo, ceramic, and the like.

Looking at the coupling relationship between the ferrule 700, the first connection member 20 and the second connection member 30 in detail as follows. First, as shown in FIG. 2, an adhesive is applied to a portion of the ferrule 700, and then fixed and inserted into and adhered to the ferrule insertion groove 240 of the first connection member 20.

Next, the remaining portion of the ferrule 700 exposed to the outside of the first connection member 20 is inserted into the ferrule insertion groove 240 of the second connection member 30 without the use of an adhesive. As a result, the first connection member 20 and the second connection member 30 may be combined.

In addition, the ferrule insertion groove 240 is manufactured to be somewhat smaller than the diameter of the ferrule 700 to prevent the ferrule 700 and the ferrule insertion groove 240 to be easily separated, thereby improving the durability and stability of the optical cable connection device 10. Can be improved.

On the other hand, when separating the first connecting member 60 and the second connecting member 70 by applying a tensile force to the first connecting member and the second connecting member to pull each other, the ferrule insertion groove of the second connecting member 70 At 650 the ferrule can be removed and separated.

In this way, by using the ferrule as the joining means of the first connecting member and the second connecting member, the optical cable connecting device can be quickly and conveniently separated and coupled, which is convenient for installation and maintenance.

Meanwhile, in the optical cable connecting device according to another embodiment, the ferrule may be formed on the inner circumferential surface of the ferrule, and may include a locking step for aligning the optical cables.

As described above, the plastic optical cables 300 introduced into the optical cable connecting portion 200 are interconnected inside the ferrule 700. In this case, when the plastic optical cables 300 are in physical contact, the ends of the plastic optical cables 300 may be damaged. On the contrary, when the plastic optical cables 300 are excessively spaced apart from each other, light scattering may occur and transmission loss may occur. As such, measures should be taken into account.

For example, as shown in FIG. 4, a locking step 710 having a diameter smaller than that of the plastic optical cable 300 and larger than an optical fiber line (not shown) of the plastic optical cable 300 is formed on the inner circumferential surface of the ferrule 700. can do.

Accordingly, the plastic optical cables 300 are aligned so as to maintain a certain distance without being in contact with each other or being excessively spaced apart from each other about the locking jaw 710. In addition, the diameter of the latching jaw 710 is manufactured to be larger than the diameter of the optical core to prevent the scattering of the optical signal by the hooking jaw 710, the plastic optical cable 300 is aligned so as to exactly face each other. As a result, the loss occurring when the plastic optical cable 300 is connected can be minimized.

On the other hand, in the optical cable connecting apparatus according to another embodiment, the fixing wedge is installed in the lower portion of the fixing wedge, it may include a wedge fixing hook for fixing the fixing wedge to the housing.

In order to prevent the plastic optical cable 300 from being drawn out of the optical cable connecting device 10 in spite of the vibration of the train or the external shock or other external shock, the fixing press 500 supporting the stopper 630 is used. A method of firmly fixing to improve the fixing force of the stopper 630 may be considered.

For example, as shown in FIG. 4, after the groove having a predetermined size is formed in the lower portion of the fixing chain 500, the fixing chain hook 510 may be installed in the groove.

The wedge fixing hook 510 may have a lower end hinged to the fixing wedge 50 and rotate at an angle, and an upper end thereof may be fixed to the fixing of the housing 100 as shown in FIG. 4. In addition, a groove corresponding to the wedge fixing hook 510 may be formed on the bottom surface of the housing 100.

Accordingly, since the fixing force of the stopper 630 can be improved, the plastic optical cables 300 can be prevented from being drawn out to the outside despite the vibration of the train or the external impact or other external force.

On the other hand, in the optical cable connecting device according to another embodiment, the optical cable connecting portion is formed on the inner peripheral surface of the optical cable connecting portion, it may include an optical cable fixing projection for preventing the optical cable is drawn out.

In order to prevent the plastic optical cable 300 from being drawn out by vibration or external impact or other external force in the optical cable connecting device 10, a method of increasing friction between the optical cables 300 and the inner circumferential surface of the optical cable connecting part 200 may be considered. Can be.

For example, as shown in FIG. 4, a plurality of hemispherical optical cable fixing protrusions 250 may be formed on the inner circumferential surface of the optical cable connecting portion 200, but the present invention is not limited thereto. Can be.

As such, by forming the optical cable fixing protrusion 250, the frictional force between the plastic optical cable 300 and the optical cable connecting portion 200 is increased to prevent the plastic optical cable 300 from being drawn out.

The present invention has been described above with reference to the embodiments described with reference to the accompanying drawings, but is not limited thereto, and encompasses obvious modifications derivable therefrom. The appended claims are intended to cover such obvious variations.

10: optical cable connection device 20: first coupling member
30: second coupling member 40: train optical communication system
100: Housing
200: optical cable connection portion 210: fixing portion
220: optical cable inlet 230: opening
240: ferrule insertion groove 250: optical cable fixing projection
300: plastic optical cable
400: fixed chain insertion hole
500: fixed wedge 510: wedge fixed hook
600: sliding part 610: slider
620: Slider Guide 630: Stopper
700: ferrule 710: jam jaw

Claims (5)

Parking amount including a wireless transceiver for transmitting and receiving data wirelessly from the outside, and network equipment for transmitting the signal received by the wireless transceiver to each vehicle via a plastic optical cable, and a camera for transmitting and receiving a signal transmitted and received with the parking amount And an optical cable connecting device for connecting plastic optical cables between vehicles in a connection box for connecting a communication line between vehicle types including a switch distributed to an imaging device, wherein the optical cable connecting devices have a symmetrical structure. And a second connecting member, wherein the first connecting member and the second connecting member include:
housing;
An optical cable connection part extending from one side of the housing to the other side, the optical cable connecting part including an opening having a part thereof opened and providing a passage through which the optical cable is inserted and connected;
A fixed chain insertion hole formed through the upper and lower surfaces of the housing;
A fixed taper inserted into the fixed slot insert so as to slide in a longitudinal direction and tapered so that the width thereof becomes narrower from the top to the bottom;
A slider installed in contact with the fixing wedge inside the housing, the slider sliding in the horizontal direction as the fixed wedge slides in the longitudinal direction, and a slider guide installed on an inner circumferential surface of the housing to guide sliding of the slider; A sliding part formed on one side of the slider and including a stopper inserted into the opening as the slider slides to fix the optical cable;
Coupling means for coupling the first connection member and the second connection member;
Optical cable connection device comprising a. The method of claim 1,
The coupling means is:
A portion is inserted into and bonded to the optical cable connecting portion of the first connecting member, and the remaining portion is inserted into the optical cable connecting portion of the second connecting member to couple the first connecting member and the second connecting member to the optical cable connecting portion; And a ferrule for aligning the optical cable inserted into the optical cable. The method of claim 2,
The ferrule is:
It is formed on the inner circumferential surface of the ferrule, characterized in that it comprises a locking step for aligning the optical cable. 4. The method according to any one of claims 1 to 3,
The fixed chain is:
The optical cable connecting device is installed in the lower portion of the fixing chain, characterized in that it comprises a wedge fixing hook for fixing the fixing chain to the housing. 4. The method according to any one of claims 1 to 3,
And an optical cable fixing protrusion formed on an inner circumferential surface of the optical cable connecting portion to prevent the optical cable from being drawn out to the outside.

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