JPH01128015A - Superconductive optical fiber - Google Patents

Abstract

PURPOSE:To provide the title fiber which is usable for communication or transmission or simultaneously for both and is simple in construction and is less bulky by forming a thin superconductive film consisting of a superconductive material of a ceramics system on the outside peripheral face of an optical fiber. CONSTITUTION:The superconductive optical fiber F is disposed in a transparent pipe 10. The superconductive optical fiber F is constituted of a core part 1, a clad part 2 and the thin superconductive film 5 consisting of an arbitrary material among the superconductive materials of the ceramics system formed on the outside peripheral face of the clad part 2. A cooling medium 11 runs in the spacing between the conductive optical fiber F and the transport pipe 10. The superconducting state of the thin superconductive film 5, i.e., the critical condition possessed by the thin superconductive film 5 can be maintained by the cooling medium 11. Large electric power can be transmitted without loss by the thin superconductive film 5 in such superconducting state. The optical communication is executed simultaneously by the core part 1 and the clad part 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a superconducting optical fiber having a superconducting thin film made of a ceramic superconducting material.

[Problems to be solved by conventional technology/inventions] Superconducting phenomenon refers to a phenomenon in which electrical resistance completely disappears below the temperature at which this phenomenon occurs (critical temperature).
differs depending on the material. Since materials with high critical temperatures can be easily cooled, the development of materials with as high critical temperatures as possible has been particularly popular recently. In addition to a high critical temperature, the upper limit of current that can be passed in a superconducting state (critical current) is also an important point for the practical application of ceramic materials. For practical use, this must be made into a wire, for example, but since the current that can be passed per unit cross-sectional area of ceramic materials is currently small, the key to practical application is how high a critical current can be obtained. This is because

Alloy-based and compound-based materials are well known as materials that cause superconductivity, and recently, the development of ceramic-based materials has been particularly advanced. The development of ceramic superconducting materials with high vA field humidity temperatures is progressing rapidly, but for practical use, it is necessary to process superconducting materials into wires, tapes, coils, etc. For example, it is necessary to process superconducting materials into wires, tapes, coils, etc. In order to make a powerful electromagnet, it must be processed into a coil.However, ceramics, which are made by sintering powdered materials, are hard and brittle, and cannot be processed like alloys by bending or winding them into coils. Therefore, in order to overcome these drawbacks and bring it closer to practical use, efforts are being made to develop not only ceramic materials but also processing methods.

One important point in the practical application of superconducting ceramic materials is how to make them into devices without deteriorating their superconducting properties, and the key to this is the production of thin films of ceramic materials. The development of thin films for ceramic superconducting materials is essential for the application of superconductors to a wide range of fields such as energy, including the field of electronic devices, and the current state of the art is that the development of thin films is becoming more and more competitive.

By the way, as is well known, in an optical fiber, a core portion with a high refractive index is wrapped in a cladding portion with a refractive index smaller than the core portion, and light is totally reflected at the interface between the core portion and the cladding portion and is confined in the core portion. It is something that is transmitted. Optical fiber is
Broadly divided into single mode fiber and multimode fiber, multimode fiber is further divided into step-index fiber, in which the refractive index changes in a step-like manner at the interface between the core and cladding, and step-index fiber, in which the refractive index changes smoothly. Graded index fiber.

Optical fiber cables that use such optical fibers are waveguides that transmit ultraviolet, visible, and infrared light, thereby transmitting information over long distances, and are generally used for long-distance communications in consideration of transmission loss. For short-distance communication, an optical fiber whose cladding part is made of polymer and whose core part is made of quartz glass or plastic (PMMA, etc.) is used. Application fields of optical fiber communication using optical fiber cables include information transmission in control and measurement systems (aircraft, ships, automobiles, trains, various measurement systems, plants,
Power systems, etc.), computer wiring, traffic control communications for road and railway networks, building and premises communications such as LAN (internal information and communications networks), public communications, submarine communications, and international communications. The development of optical fiber cables is one of the most important issues in the practical application of optical transmission lines, and efforts are being made to develop cables that can achieve high-density transmission with as low loss as possible. This is the current situation.

By the way, if a current flows through a conductor such as a wire or cable,
It is known that a magnetic field is generated concentrically around a conductor, but in order to prevent the magnetic field from affecting the outside of the cable, for example, in the case of cable communication, noise occurs in the transmission frequency or the frequency changes. , it is necessary to sufficiently shield the generated magnetic field. Since the strength of the magnetic field is proportional to the size of the current, a considerably high magnetic field is generated, especially in power cables that transmit large currents. It is necessary to shield this high magnetic field or make it unaffected by the magnetic field, but advantageously, the aforementioned optical fibers, especially optical fibers made of quartz glass, are shielded from the magnetic field because silica glass is a ceramic. It has the advantage of not being easily affected.

In order to perform optical communication using optical fibers and power transmission using electric cables, it is usually necessary to install the optical fiber cable and the electric cable separately, so if optical communication and power transmission are to be carried out at the same time, both must be installed. The installation requires a lot of space, and the installation work is troublesome and the construction costs are high.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an optical fiber that can be used for communication, power transmission, or both at the same time, has a simple structure, and is not bulky.

[Means for solving problems]

The above object is achieved by a superconducting optical fiber characterized in that a superconducting thin film made of a ceramic superconducting material is formed on the outer peripheral surface of the optical fiber.

A feature of the superconducting optical fiber of the present invention is that a superconducting thin film made of a ceramic superconducting material is formed on the outer peripheral surface of the optical fiber, that is, the outer peripheral surface of the cladding part. Optical fibers can perform optical communications, and can be used for power transmission or communication, or both at the same time.

In the present invention, this is the basic structure, and a modified example is one in which a thermal buffer layer is interposed between the outer circumferential surface of the optical fiber and the superconducting thin film, that is, both the thermal buffer layer and the superconducting thin film are provided on the outer circumferential surface of the optical fiber. Furthermore, in order to maintain the superconducting state of the superconducting thin film more efficiently, the above-mentioned superconducting optical fibers may be arranged in a hollow transport pipe through which a cooling medium is passed, or a plurality of superconducting optical fibers may be installed. One example is one in which a bundle of superconducting optical fibers is placed in a hollow transport pipe through which a cooling medium is passed.

In the superconducting optical fiber of the present invention, there is no particular restriction on the optical fiber on which the superconducting ix thin film is formed, and any ordinary optical fiber may be used. As mentioned above (in general, optical fibers with polymer cladding and quartz glass core or plastic optical fibers are used for medium-range communications, and silica glass optical fibers are used for long-distance communications, but the outer periphery of the optical fiber Considering that a superconducting thin film made of ceramic material is formed on a surface, plastic and superconducting thin films have different thermal properties based on the difference between organic and inorganic materials. Therefore, it is preferable to use a silica glass optical fiber because of its compatibility with ceramic materials and transmission loss especially in long-distance communications. In other words, quartz glass and superconducting thin film are ceramic materials, and thermal expansion Since the coefficients are similar, there is not much difference in the thermal expansion of the two materials due to temperature changes, so there is no problem such as the two materials peeling off from each other's interface. When used for wiring, etc., it is sufficient to use plastic optical fibers because the distance is short and there is no need to take transmission loss into consideration.

In the superconducting optical fiber of the present invention, the ceramic superconducting material that is the material of the superconducting thin film formed on the outer circumferential surface of the optical fiber (the outer circumferential surface of the cladding part) is not particularly limited, and the oxide contains especially heavy rare earth elements (lanthanum). , ytterbium, dysprosium, holsium, erbium, thulium, yttrium, strontium, etc.). Such a material may be an existing material, but for example, barium or yttrium may be used as a component of the material.・Ceramics whose compositions include copper/oxygen, barium/lanthanum/copper/oxygen, strontium/lanthanum/copper/oxygen, barium/scandium/copper/oxygen, calcium/lanthanum/copper/oxygen, etc. are preferably ceramic materials. It is a material consisting of barium, yttrium, copper, and oxygen, which is a yttrium-based material that is becoming mainstream. Further, as an example, when using this yttrium-based superconducting material, the preferred blending ratio is Ba: Y: Cu: O = 2: 1:
3:6-7.

In the present invention, a ceramic material having such a composition is used. The method for producing the material may be any conventionally known method and is not particularly limited. For example, raw material powder (for example, in the case of the yttrium-based superconducting material of barium, yttrium, copper, and oxygen, barium carbonate,
In the present invention, barium carbonate, yttrium oxide, copper oxide, etc. may be manufactured by a solid-state process including mixing of yttrium oxide, yttrium oxide, steel oxide, etc. → sintering → re-powdering of the sintered body. Mixtures of raw powders can also be used.

The obtained ceramic superconducting material powder or a mixture of its raw material powders is used to form a superconducting thin film on the outer peripheral surface of an optical fiber.

The thermal buffer layer interposed between the cladding part of the optical fiber and the superconducting thin film, which is Example B of the present invention, is the same material as the superconducting thin film, which is easily compatible with either the cladding member of the optical fiber or the superconducting thin film material. There is no problem if it is a ceramic material of the [(14 series), or Cu
-0 series material may be used. Note that it is not necessary to provide only one thermal buffer layer between the cladding part and the superconducting thin film;
There is no problem even in an embodiment in which another thermal buffer layer is provided between the thermal buffer layer and the superconducting thin film to form a plurality of layers.

Furthermore, the transport tube for arranging the superconducting optical fiber may be made of materials such as aluminum, copper, or stainless steel, as long as it exhibits corrosion resistance, cold resistance, magnetism resistance, etc. to the cooling medium introduced into the tube. . Furthermore, the cooling medium passed through the transport pipe is used to maintain the superconducting state of the superconducting thin film, and is used due to the critical temperature of the superconducting thin film, that is, the ceramic superconducting material from which it is made. Although the medium is different, Heriram,
Nitrogen, carbon dioxide, etc., and helium has a cooling temperature of 4
For K and nitrogen, the cooling temperature is about 77 K, and for carbon dioxide, the cooling temperature is about 196 K. Depending on the cooling temperature of these cooling media, a ceramic superconducting material that becomes superconducting with that temperature as the critical temperature should be selected appropriately. is essential.

〔Example〕

Hereinafter, the superconducting optical fiber of the present invention will be explained in more detail based on Examples.

FIG. 1 shows one embodiment of the present invention, in which a superconducting optical fiber F is placed inside a transport pipe 10.

The superconducting optical fiber F is composed of a core portion 1, a cladding portion 2, and a superconducting thin film 5 formed on the outer peripheral surface of the cladding portion 2 and made of any material among the ceramic superconducting materials described above. Here, to give an example of the size of the superconducting optical fiber F, the diameter of the superconducting optical fiber is approximately 190 mm.
p=, of which the diameter of the core part 1 is about 50P-, the diameter of the cladding part 2 is about 125P, and the thickness of the superconducting thin film 5 is about 3P.
0-, the diameter of the transport pipe 10 is approximately 8 ms, and the inner diameter is approximately 6
It is mm. A cooling medium 1) communicates with the gap between the superconducting optical fiber F and the transport pipe 10. The superconducting thin film 5 can maintain its superconducting state, that is, the critical conditions of the superconducting thin film 5, by the cooling medium 1), and the superconducting thin film 5 in this superconducting state
This makes it possible to transmit large amounts of power without loss,
At the same time, optical fiber communication can be performed between the core part 1 and the cladding part 2. The overall structure of the superconducting optical fiber, which has an extremely thin superconducting thin film on the outer circumferential surface of the optical fiber, is very simple and, as described below, easy to manufacture. If used, it becomes possible not only to perform optical communication using optical fibers, but also to transmit large amounts of power at the same time.Since there is no heat generated during power transmission, there is no need to take special measures for cable heat dissipation. Since the fiber is unaffected, there is no problem with optical fiber communication.In addition, since the optical fiber remains a thin wire, the cable itself is small and requires only a small space for installation, which is revolutionary. It is.

FIG. 2 shows another embodiment, in which a superconducting optical fiber F is disposed within the transport pipe 10 as in FIG.

In the superconducting optical fiber F, a thermal buffer layer 7 made of, for example, copper oxide is formed on the outer peripheral surface of the cladding portion 2, and a superconducting thin film 5 made of a ceramic superconducting material is formed on the thermal buffer layer 7. A cooling medium 1) communicates with the gap between the transport pipe 10 and the superconducting optical fiber F. In this example, the thermal buffer layer 7 is interposed between the cladding part 2 and the superconducting thin film 5, so that the optical fiber member and the superconducting thin film member are well compatible with each other, and the superconducting thin film does not peel off even during cooling. As an optical fiber, it is more preferable than the one shown in FIG.

In the above embodiment, one superconducting optical fiber is arranged inside the transport pipe, but a case where a plurality of superconducting optical fibers F are bundled and arranged inside the transport pipe 10 is shown in Fig. 3. is for cooling multiple superconducting optical fibers F at once, and the bundled superconducting optical fibers F and transport pipe 1
The cooling medium 1) occupies not only the gap with 0° but also the gap between the superconducting optical fibers F, and cooling is performed efficiently. As in this example, if multiple superconducting optical fibers are used in a bundle, even larger amounts of power can be transmitted, and moreover, multiple superconducting optical fibers can be cooled at once by the cooling medium in the transport pipe, and the superconducting thin film Cooling costs to maintain the superconducting state can also be kept low.

There are no particular limitations on the method of manufacturing a superconducting optical fiber having the structure described above. For example, the main method for manufacturing the optical fiber itself is to form a tube with a cladding section containing B or F inside a quartz rod that serves as the core. Approximately 1900 after covering
The rod-in-tube method involves drawing and spinning at a high temperature of °C. The external CVD method involves growing a core containing Ge on the rod that becomes the core, and then growing the cladding containing B and F. Gas is added to the inside of the Si0g tube. Filled CD method (MCVD method) in which a Si0g film containing Ge, P, ^l, etc. is grown to form a core part, and then stretched and spun.Ge, AI is grown in the axial direction using the tip of a quartz rod as a seed. There is a vapor phase axial attachment method (VAD method) for growing 5iOJ containing 5iOJ, and superconducting Fi! made of ceramic material is grown on the outer circumferential surface of the optical fiber rod obtained by these methods, that is, on the outer circumferential surface of the cladding part.
A base material is prepared by sputtering a film or sintering after coating, and this is spun in steps to produce a superconducting optical fiber. In addition to this, other manufacturing methods can be considered, such as applying it to the optical fiber and then sintering it when drawing the optical fiber.

The thickness of the superconducting thin film formed on the outer peripheral surface of the optical fiber varies depending on the type of optical fiber and its material, but for example, for an optical fiber with a diameter of 250 mm or less,
~100 p-1 Preferably about 10-50 p-1, 50-200 for those with a diameter of about 250-1000 p-1
s-1 preferably about 80 to 150-, diameter 1ff1
) 100 to 300 pm, preferably about 150 to 200 pm.

〔Effect of the invention〕

As explained above, according to the superconducting optical fiber of the present invention, since a superconducting thin film made of a ceramic superconducting material is formed on the outer peripheral surface of the optical fiber, a large amount of power can be transmitted without loss of ti by the superconducting thin film, and at the same time, the optical fiber This is an epoch-making technology that enables optical fiber communication to be carried out at will, allowing one or both of power transmission and communication to be carried out efficiently at the same time without being affected by the magnetic field generated during power transmission. If adopted for optical fiber cables, the cable itself will not need to be thick, cable installation work will be done underground, and construction costs will be lower than when installing ordinary optical fiber and cable separately, making it extremely A compact power transmission communication line will be realized.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of one embodiment of the superconducting optical fiber of the present invention, FIG. 2 is a partially cutaway perspective view of another embodiment, and FIG.
The figure is a partially cutaway perspective view of yet another embodiment. F: Superconducting optical fiber 1: Core section 2: Clad section 5: Superconducting thin film 7: Thermal buffer layer 10.10゛: Transport pipe 1): Refrigerant patent applicant Mitsubishi Cable Industries, Ltd., 1, -

Claims (7)

[Claims] (1) A superconducting optical fiber characterized in that a superconducting thin film made of a ceramic superconducting material is formed on the outer peripheral surface of the optical fiber. (2) The superconducting optical fiber according to claim (1), characterized in that a thermal buffer layer is interposed between the outer peripheral surface of the optical fiber and the superconducting thin film. (3) The superconducting optical fiber according to claim (2), wherein the thermal buffer layer is made of a ceramic material. (4) The superconducting optical fiber according to claim (2), wherein the thermal buffer layer is made of a Cu-O based material. (5) The superconducting optical fiber according to any one of claims (1) to (4), wherein the optical fiber is made of silica glass. (6) The superconducting optical fiber is arranged in a hollow transport pipe through which a cooling medium is passed. Superconducting optical fiber. (7) A plurality of the superconducting optical fibers are arranged in a bundle in a hollow transport pipe through which a cooling medium is passed. The superconducting optical fiber according to any one of the items.