JPH08211232A - Air tight optical adapter - Google Patents

Abstract

PURPOSE: To provide an air tight adapter which allows the penetration of a signal mode optical fiber into a hermetic container without intervention of a lens system. CONSTITUTION: An air tight adapter 10 has a flange part 34, the single mode optical fiber 38 and a seal ring 40. The flange part 34 is formed to a disk shape larger than the outside diameter of a through-hole 27 and is provided with plural mounting holes 42 of bolts 41 of the outer peripheral side thereof. The flange part 34 is bored with an insertion hole 43 axially penetrating the central part thereof. The optical fiber 38 is coated with a metallic film 46. Brazable metallic materials, such as copper, nickel, gold and silver, are selected for the metallic film 46. The optical fiber 38 is inserted into the insertion hole 43 and is fixed by melting, filling and solidifying the brazing filler metal, such as solder or silver solder, between the metallic film 46 and the inner peripheral surface of the insertion hole 43.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an airtight optical adapter, and more particularly to an optical adapter in which a single-mode optical fiber is installed through a hermetically sealed container.

[0002]

2. Description of the Related Art A method of measuring a current utilizing the Faraday effect in which the plane of polarization of light is rotated by the action of a magnetic field is known, and an optical current transformer of the circular integration type based on such a measurement principle is known. Practical application has been studied for measuring current in a gas-insulated switchgear (GIS) housed in a closed container. This kind of optical current transformer has the advantages that it is not affected by electromagnetic noise and that it can be electrically insulated easily.It forms an optical path on the outer circumference of the conductor through which the current to be measured flows. The linearly polarized light will pass through.

As a means for constructing an optical path, a structure using an optical fiber as a current sensor has recently been developed, which can achieve miniaturization and weight reduction. One example thereof is JP-A-62-1.
It is disclosed in Japanese Patent No. 61059. By the way, if an optical current transformer with such a configuration is adopted in a gas-insulated switchgear, the light between the light source or receiving circuit installed outside the closed container and the current sensor installed inside the closed container will be affected. Therefore, it is necessary to transmit light through the wall of the closed container.

In this case, the performance required for the penetrating portion is that the airtightness of the closed container is ensured, the light coupling is stable, and the light transmission loss is small. As a light penetrating means satisfying such requirements, for example, in "Shimadzu Kenron", Vol. 48, No. 4, published by Shimadzu Corporation in 1991, a structure using a plurality of lenses, glass plates and a plurality of O-rings was used. Airtight adapters have been proposed.

[0005]

However, the airtight adapter disclosed in the above-mentioned publicly known document is composed of a combination of a plurality of lenses, a glass plate and a plurality of O-rings, and therefore has a complicated structure. It was Further, since the airtight adapter shown in this known document is intended for coupling of multimode optical fibers, a lens system is used for the coupling portion.

However, for example, the current measuring sensor in the gas-insulated switchgear as described above uses a single mode optical fiber because it has to maintain the plane of polarization. When a lens system is used in the coupling portion when coupling optical fibers, the core diameter of the single-mode optical fiber is very small, which makes alignment of the optical axis with the lens system difficult and very time-consuming.

Moreover, even if such optical axis alignment can be performed sufficiently, the function of the current sensor will be impaired if the optical axis is slightly displaced due to changes in surrounding environmental conditions. There was also a problem with durability over time.
The present invention has been made in view of such conventional problems, and an object thereof is to easily install a single mode optical fiber through a hermetically sealed container without using a lens system. It is to provide an airtight adapter capable of Also, as another purpose, there is little transmission loss,
It is to provide an airtight adapter having excellent durability.

[0008]

To achieve the above object, the present invention provides a single mode optical fiber coated with a metal film, and a flange portion having a through hole for the single mode optical fiber. Having the single-mode optical fiber in the insertion hole, sealingly fixing the metal film and the flange portion, and the single-mode optical fiber in a through hole provided in the wall surface of the hermetic container. The flange portion is fixedly provided via a sealing material so as to cover the through hole in a state where the flange portion is inserted. The sealing and fixing can be a brazing fixing such as solder or silver brazing. Further, the brazing and fixing is performed by melting the brazing material such as solder or silver brazing in a state where the single mode optical fiber is inserted into the insertion hole, and the inner peripheral surface of the insertion hole and the metal film. It can be done by filling between the outer peripheral surface of the The airtight container is for a gas-insulated switchgear in which SF ₆ is sealed, and is provided so as to circulate one end of the single mode optical fiber around the outer circumference of the conductor in the airtight container. It can be connected to an optical sensor made of a single mode optical fiber.

[0009]

According to the airtight adapter of the above construction, the single mode optical fiber coated with the metal film and the flange portion having the insertion hole for the single mode optical fiber in the central portion are provided. Insert the single-mode optical fiber into the inside, seal the metal coating and the flange portion tightly, and insert the one-sided end of the single-mode optical fiber into the through-hole provided in the hermetically sealed container. Since the flange part is fixedly provided so as to cover it with the sealing material, the airtightness between the metal film and the flange part is ensured by the sealing and fixing such as brazing, and the sealing material forms the flange part and the closed container wall surface. The airtightness between the two is ensured, and furthermore, the optical fiber can be passed through the closed container without using a lens system. Further, according to the airtight adapter of the present invention, since the single-mode optical fiber is directly passed through the hermetically sealed container, the troublesome optical axis alignment as in the case of using the lens system is not necessary. It is also possible to avoid an increase in transmission loss at.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 1 to 3 show an embodiment of an airtight adapter according to the present invention. An airtight adapter 10 shown in the figure shows a case where the present invention is applied to a gas insulated switchgear (GIS). The gas-insulated switchgear (GIS) has a hollow cylindrical hermetic container 12 in which SF ₆ gas is sealed, and a conductor 14 through which an electric current flows is provided therein.

The airtight adapter 10 constitutes a part of the optical current transformer 16 for measuring the current flowing through the conductor 14, and the optical current transformer 16 is arranged so as to circulate around the outer circumference of the conductor 14. And a current sensor 18 composed of a single mode optical fiber arranged along the inner peripheral surface of the closed container 12,
An optical junction box 20 installed at the end of the current sensor 18
And an electronic circuit section 22 installed outside the closed container 12.

A hollow cylindrical flange 24 is integrally projectingly provided on one end of the outer peripheral wall surface of the hermetically sealed container 12, and an opening end of the flange 24 is a disk fixedly secured to the flange 24 by fastening a bolt nut. The lid plate 26 is closed by a lid plate 26, and a through hole 27 is formed at the center of the lid plate 26. The optical junction box 20 contains optical system components such as a polarizer, an analyzer, a lens, and a prism, which are components of the optical current transformer 16, and the optical junction box 20 has an interior of the sealed container 12. It is installed in the flange 24 communicating with.

The electronic circuit section 22 includes, for example, two light receiving elements 28, which are photodiodes, and a light source 30, which is a semiconductor laser, a super luminescent diode, or the like.
And the signal processing circuit 3 electrically connected to the light receiving element 28.
2 and. The airtight adapter 10 is shown in FIG.
As shown in more detail in this embodiment, this embodiment has a flange portion 34, two multimode optical fibers 36, one single mode optical fiber 38, and a seal ring 40. The flange portion 34 has a disc shape larger than the outer diameter of the through hole 27 formed through the cover plate 26,
A plurality of mounting holes 42 for the bolts 41 are provided on the outer peripheral side thereof, and a plurality of screw holes 26 a are provided in the cover plate 26 corresponding to the mounting holes 42.

Further, the flange portion 34 is provided with three insertion holes 43 penetrating in the axial direction of the central portion thereof, and the inner diameter of the insertion hole 43 is larger than the outer diameters of the optical fibers 36 and 38. It is getting bigger. At the open end of each insertion hole 43, a counterbore portion 43a is formed, which is open to the outside, so that the work of fixing the extremely fragile optical fibers 36 and 38 can be facilitated.

The seal ring 40 is, for example, an O-ring and is arranged on the inner peripheral side of the mounting hole 42. The single mode optical fiber 38 introduces the light emitted from the light source 30 of the electronic circuit section 22 to one end of the current sensor 18 via the polarizer in the optical junction box 20, and It is connected in the vicinity via the optical connector 44.

The multimode optical fiber 36 circulates the light passing through the current sensor 18 so that the light passes through the optical junction box 2.
It is led out to the light receiving element 28 via an analyzer or prism inside 0, and is connected via an optical connector 44 in the vicinity of the airtight adapter 10. The connection between the optical fibers 36 and 38 is not limited to the connection by the optical connector 44, and for example, the end portions may be mirror-finished and fusion-bonded.

Each optical fiber 36, 38 is coated with a metal film 46, as shown in a partially enlarged view of FIG. The metal film 46 is, for example, an ultraviolet curable resin film 48 provided on the outer circumferences of the optical fibers 36 and 38.
Alternatively, the resin film 48 may be partially removed to directly coat the outer circumference of the optical fibers 36 and 38.

More practically, the resin film 48 is partially removed and the outer circumference of the optical fibers 36 and 38 is set to several μm or less by an electroless plating method, a vacuum deposition method, a sputtering method, an ion plating method or the like. A thin film of a certain degree is formed, and a metal film having a predetermined thickness is formed on the thin film by electroplating. For the metal film 46, for example, a brazable metal material such as copper, nickel, gold, or silver is selected, and the length of the metal film 46 portion is about twice the thickness of the flange portion 34 in this embodiment. Has become the length of.

The optical fibers 36 and 38 coated with the metal coating 46 are inserted into the respective insertion holes 43, and solder or metal is inserted between the metal coating 46 of each optical fiber 36 or 38 and the inner peripheral surface of the insertion hole 43. By melting, filling, and solidifying a brazing material such as silver brazing, the optical fibers 36 and 38 and the flange portion 34 are fixed to each other. The flange portion 34, to which the optical fibers 36 and 38 are fixed by brazing, allows one end side of the optical fibers 36 and 38 to be inserted into the through hole 27 provided in the lid plate 26, and one of the optical connectors 44 is used. The optical fibers 36 and 38 are connected to each other, the seal ring 40 is interposed between the front surface of the cover plate 26 and the rear surface of the flange portion 34, and the bolt 42 is screwed into the screw hole 26a to be tightened, whereby the flange The portion 34 is fixed to the lid plate 26.

When the optical fibers 36 and 38 are connected to each other by the other optical connector 44, the installation of the optical current transformer 16 is completed, and the Faraday rotation of the light passing through the current sensor 18 flows through the conductor 14. The current is measured.
In this case, in the airtight adapter 10 of this embodiment, the single mode optical fiber 38 coated with the metal film 46 is used.
And a flange portion 34 in which the insertion hole 43 of the single mode optical fiber 38 is formed in the central portion, and the single mode optical fiber 38 is inserted into the insertion hole 43 to form the metal film 34 and the flange portion 34. And brazing and fixing, and the lid plate 2 of the closed container 12
In the through hole 27 provided in the single mode optical fiber 3
Since the flange portion 34 is fixedly mounted via the seal ring 40 so as to cover the through hole 27 in a state where the one end side of 8 is inserted, the airtightness between the metal film 46 and the flange portion 26 is obtained by brazing and fixing. Secured and seal ring 40
Thereby, the airtightness between the flange portion 34 and the closed container 12 is secured, and furthermore, the optical fiber can be penetrated through the closed container 12 without using a lens system.

In the case of this embodiment, the optical fiber 3
Since the outer peripheral surface of the metal coating 46 of Nos. 6 and 38 and the inner peripheral surface of the insertion hole 43 are brazed and fixed, the axial length of the flange portion 34 and the entire peripheral direction are hermetically fixed. Therefore, sufficient airtightness can be obtained, and the optical fibers 36 and 38 can be firmly held by the flange portion 34.

Further, according to the airtight adapter 10 of the present invention, the single-mode optical fiber 38 is directly penetrated through the hermetically sealed container 12, so that a troublesome optical axis alignment as in the case where a lens system is used is performed. It becomes unnecessary and it is possible to avoid an increase in transmission loss in this portion. In the above embodiment, the closed container 12 is provided with the flange 24, and the airtight adapter 10 is attached to the cover plate 26 that closes the flange 24. However, the embodiment of the present invention is not limited to this. Instead, for example, a through hole is formed in the wall surface of the closed container 12, and the airtight adapter 10 is formed by closing the hole.
Can also be attached directly.

Further, in the above embodiment, the case where the present invention is used for the closed container 12 of the gas insulated switchgear (GIS) in which SF ₆ gas is sealed is illustrated, but the present invention is not limited to this. Of course, it can also be used for other closed containers. Further, in the above embodiment, the case where the single mode optical fibers 36 and 38 are brazed and fixed to the flange portion 34 is illustrated, but this method can be applied to an optical fiber that propagates light of a plurality or a large number of modes. Of course, it is possible and effective.

[0024]

As described above in detail in the embodiments,
According to the airtight adapter according to the present invention, the single-mode optical fiber can be passed through the sealed container without the interposition of the lens system, so that very troublesome optical axis alignment with the lens system is unnecessary. become. Further, since this optical axis alignment becomes unnecessary, there is no fear that the function of the current sensor will be impaired due to changes in surrounding environmental conditions and the like, and it has durability over time.

[Brief description of drawings]

FIG. 1 is an overall layout explanatory view showing a usage example of an airtight adapter according to the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a side view of an essential part of an optical fiber used in the airtight adapter of the present invention.

[Explanation of symbols]

 10 Airtight Adapter 12 Airtight Container 16 Optical Current Transformer 34 Flange 36 Multimode Optical Fiber 38 Single Mode Optical Fiber 40 Seal Ring 43 Insertion Hole 46 Metallic Film

Claims (4)

[Claims] 1. A single mode optical fiber coated with a metal film, and a flange portion having an insertion hole for the single mode optical fiber, wherein the single mode optical fiber is provided in the insertion hole. Insert it,
The metal film and the flange portion are hermetically fixed to each other, with one end side of the single mode optical fiber being inserted into the through hole provided in the hermetically sealed container, with a sealing material interposed so as to cover the through hole. An airtight optical adapter, wherein the flange portion is fixedly provided. 2. The hermetically sealed optical adapter according to claim 1, wherein the hermetically sealed fixing is a brazing fixing of solder or silver brazing. 3. In the brazing and fixing, the brazing material such as solder or silver brazing is melted in a state where the single mode optical fiber is inserted into the insertion hole to fix the inner peripheral surface of the insertion hole. The airtight adapter according to claim 2, wherein the airtight adapter is filled with the outer peripheral surface of the metal film. 4. The closed container is for a gas-insulated switchgear in which SF ₆ is sealed, and one end of the single mode optical fiber is wound around the outer circumference of a conductor in the closed container. The airtight adapter according to any one of claims 1 to 3, wherein the airtight adapter is connected to an optical sensor made of a single mode optical fiber provided in the.