JP2002277554A - Optical fiber and optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, at a low cost, a scintillation optical fiber and a scintillation optical fiber cable having small optical transmission loss and used for a detection means required for composing a radiation leakage monitoring system. SOLUTION: This optical fiber 10 has a light guiding property, and is provided with a core 12 extending along one direction, a first clad layer 14 covering the entire circumferential surface of the core for closing the light transmitted through the inside of the core in the inside thereof, and a second clad layer 16 covering the entire circumferential surface of the first clad layer. Scintillators 20 for emitting light by a radioactive ray are scattered in the second clad layer, and at least part of the light emitted by irradiating the radioactive ray on the scintillators is transmitted through the inside of the core.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber for transmitting light and an optical fiber cable having the optical fiber therein.

[0002]

2. Description of the Related Art Conventionally, in a facility or the like that handles (uses) radiation, radiation leakage causes a great deal of damage to the body. Therefore, various measures have been taken to minimize the occurrence of radiation leakage. A detection system for quickly and reliably detecting the occurrence of such a phenomenon has been developed and is being put to practical use.

For example, a system in which a radiation monitoring device such as a well-known scintillation counter is installed in all places where radiation leakage is likely to occur, and the radiation leakage is constantly monitored by this monitoring device. Built,
It has been put to practical use.

Further, Japanese Patent Application Laid-Open Nos. 9-90047 and 20
A radiation monitoring device using a scintillation fiber as a sensor for radiation detection, as shown in JP-A-00-137122, is installed.
A system for monitoring radiation leaks has been constructed and put to practical use.

[0005]

However, in a conventional radiation monitoring system using a scintillation counter, the scintillation counter must be installed at each detection point, but is expensive. For this reason, construction of such a monitoring system is very expensive. Therefore, within a limited budget, it is difficult to construct a monitoring system in which monitoring devices are installed in all places where the equipment is to be installed. Has become difficult, and improvements have been demanded.

Also, Japanese Patent Application Laid-Open Nos. 9-90047 and 20
In a conventional radiation detection system using a scintillation fiber as disclosed in JP-A-00-137122, the scintillation fiber has a structure in which a core member, which is an optical waveguide of an optical fiber, is replaced with a scintillator material. Optical transmission loss is large, and transmission over several tens of meters is difficult. Therefore, scintillation fibers must be installed at each of the radiation detection points, and a complex monitoring system is required to construct a large-scale monitoring system in which the transmission distance is several hundred meters or more and the monitoring points do not leak. Equipment is needed and improvements are being sought.

[0007] That is, there is an urgent need for a new development of a detector that can easily and inexpensively construct a detection system for detecting radiation leakage.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide an inexpensive and simple optical fiber and optical fiber cable necessary for constructing a radiation leakage monitoring system. It is to provide.

[0009]

Means for Solving the Problems The above-mentioned problems are solved,
To achieve the object, the optical fiber according to the present invention is:
According to the description of claim 1, a core having an optical waveguide property and extending in one direction, and a light which is entirely coated on the outer peripheral surface of the core and transmitted through the core is used as the core. A first clad layer confined in, and a second clad layer that covers the entire outer peripheral surface of the first clad layer,
In the second cladding layer, a scintillator emitting light by radiation is dispersed, and at least a part of light emitted by irradiation of the scintillator with radiation is
The transmission is performed in the core.

According to a second aspect of the present invention, there is provided an optical fiber having optical waveguide properties, a core extending in one direction, and an outer peripheral surface of the core being entirely covered. A cladding layer for confining light transmitted through the core in the core, the cladding layer including an inner layer and an outer layer, and a scintillator emitting light by radiation is dispersed in the outer layer. The scintillator is characterized in that at least a part of the light emitted by irradiating the scintillator is transmitted through the core.

According to a third aspect of the optical fiber according to the present invention, the scintillator is an inorganic scintillator.

According to a fourth aspect of the present invention, in the optical fiber according to the fourth aspect, the radiation includes X-rays, α-rays, β-rays,
The scintillator emits light by any of the X-rays, α-rays, β-rays, and γ-rays.

Further, according to a fifth aspect of the optical fiber according to the present invention, the outer peripheral surface of the second clad layer is coated with a protective layer.

According to a sixth aspect of the present invention, in the optical fiber according to the present invention, an outer peripheral surface of the cladding layer has
It is characterized in that the protective layer is covered.

According to a seventh aspect of the optical fiber according to the present invention, the core is formed of quartz glass.

According to the optical fiber of the present invention, the first clad layer and the second clad layer are formed of a transparent polymer synthetic resin. I have.

According to a ninth aspect of the optical fiber according to the present invention, the cladding layer is made of a transparent polymer synthetic resin.

According to a tenth aspect of the optical fiber according to the present invention, the first clad layer and the second clad layer are formed of the same material.

According to the eleventh aspect of the optical fiber according to the present invention, the first clad layer and the second clad layer are formed of materials having the same refractive index. And

According to a twelfth aspect of the optical fiber according to the present invention, the scintillator is dispersed in the second cladding layer by doping.

According to a thirteenth aspect of the optical fiber according to the present invention, the scintillator is dispersed in the outer layer by doping.

According to a fourteenth aspect of the present invention, there is provided an optical fiber cable having an optical waveguide property, a core extending in one direction, and an outer peripheral surface of the core entirely. A first cladding layer for coating and confining light transmitted through the core in the core, a second cladding layer for covering the entire outer peripheral surface of the first cladding layer, A protective layer that covers the outer peripheral surface of the clad layer, wherein the second clad layer is dispersed with a scintillator emitting light by radiation, and at least light emitted by irradiation of the scintillator with radiation. A part is characterized by comprising an optical fiber transmitted through the core and a reinforcing layer coated on the outer peripheral surface of the protective layer.

According to the fifteenth aspect, the optical fiber cable according to the present invention has an optical waveguide, a core extending in one direction, and an entire outer peripheral surface of the core. A clad layer that covers and confine the light transmitted through the core within the core, and a protective layer that covers the outer peripheral surface of the clad layer, the clad layer includes an inner layer and an outer layer, In the outer layer, a scintillator emitting light by radiation is dispersed, and at least a part of light emitted by irradiation of the scintillator with radiation is
An optical fiber transmitted through the core and a reinforcing layer coated on the outer peripheral surface of the protective layer are provided.

Further, according to the optical fiber cable according to the present invention, the reinforcing layer is provided with a bundle of reinforcing fibers extending along the one direction.

In the optical fiber cable according to the present invention, the reinforcing fiber bundle is fixed to the outer periphery of the optical fiber by winding the outer periphery of the bundle with a tape. It is characterized by having.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

{First Embodiment} An optical fiber according to the present invention and a configuration of an optical fiber cable provided with the optical fiber according to an embodiment will be described in detail with reference to FIG.

As shown in FIG. 1, an optical fiber 10 according to this embodiment has a core 12 made of pure silica glass having optical waveguide properties and extending in one direction, and a core 1 made of pure silica glass.
2 and a second cladding layer 16 for covering the outer peripheral surface of the first clad layer 14 in a state of being completely adhered thereto.
And a protective layer 18 that covers the entire outer peripheral surface of the second clad layer 16 to protect the second clad layer 16.

Here, since the core 12 has a well-known structure, the description thereof will be omitted. However, in the present invention, the core 12 is not limited to being made of pure silica glass, and may be, for example, an optical waveguide. Needless to say, it may be made of transparent plastics as long as its properties are ensured and durability (life) is ensured.

On the other hand, the first cladding layer 14 described above
Polymer synthetic resins, for example, UV acrylate and Pyrocoat (trade name: Lucent Specialty Fiber Technology, Inc., Connecticut, USA) are used.

Further, the above-mentioned second cladding layer 16
Polymer synthetic resins, for example, UV acrylate and Pyrocoat (trade name: Lucent Specialty Fiber Technology, Inc., Connecticut, USA) are used.

The above-mentioned first cladding layer 14 and second cladding layer 16 are formed so that photons emitted by a scintillator 20 described later are introduced into the core 12 without loss. It is desirable to use the above-mentioned polymer synthetic resin so that (refractive index of) = (refractive index of the second cladding layer 16).

The second cladding layer 16 has an X-ray,
A scintillator 20 that emits light by any of α-rays, β-rays, and γ-rays is dispersed by doping or the like. here,
The scintillator 20 is a well-known one, and a detailed description thereof is omitted. In this embodiment, NaI (Tl) or Cs
An inorganic scintillator such as I (Tl) is employed.

The scintillator 20 that emits X-rays includes CaF2 (E1) in addition to Nal (T1) described above.
u), YAP (Ce) and the like are known, and as the scintillator 20 that emits light with α rays, the above-described CsI (Tl)
In addition, BaF2 and the like are known, and as the scintillator 20 that emits light with β rays, the above-described CaF2 (Eu) or B
aF2 and the like are known, and examples of the scintillator 20 that emits γ-rays include NaI (Tl) and CsI (T
l) Other than BaF2, CeF3, B4G3O12, Cd
WO4 and the like are known.

The protective layer 18 is made of a synthetic resin having a predetermined mechanical strength, for example, Tefzel (trade name:
Lucent Specialty Fiber Technology, Inc. (Connecticut, USA).
Note that the protective layer 18 is not an essential component of the optical fiber 10, and the optical fiber 10 is configured even when it is omitted.

Since the optical fiber 10 is configured as described above, when the optical fiber 10 is irradiated with radiation such as α-rays, β-rays, and gamma rays, the optical fiber 10 is dispersed on the second cladding layer 16 by the radiation. The energy absorbed by the scintillator 20 is used for excitation together with ionization of atoms (or molecules) constituting the scintillator 20. Then, when the excited atoms return to the original ground state, or when the electron-ion pairs generated as a result of ionization recombine through some process, photons are emitted. This emission of photons is defined as a phenomenon of luminescence due to radiation.

As described above, the scintillator 20 emits light in response to the irradiation of the radiation, and this light is transmitted through the interface between the first cladding layer 14 and the second cladding layer 16 to the first cladding layer. 14 and further into the core 12 through the interface between the first cladding layer 14 and the core 12.

As described above, the light introduced into the core 12 repeats refraction at the interface between the core 12 and the first cladding layer 14 and is transmitted through the core 12 along the extending direction.

As a feature of the present invention, the core 12
Since the above-described scintillator 20 is not dispersed in the first cladding layer 14 that covers the entire surface of the first cladding layer 14, the light introduced into the core 12 Core 12 without loss at the interface
Are transmitted along the extension direction.

As described above, the interface between the core 12 and the cladding layer 14 is important for the first cladding layer 14, and the thickness of the first cladding layer 14 is to reduce the weight of the optical fiber. In order to maintain flexibility, there is no problem even if it is as thin as possible.

Here, the above-mentioned optical fiber 10 is used specifically in the form of an optical fiber cable described below, because the optical fiber 10 itself has insufficient mechanical strength.

Next, the configuration of the optical fiber cable 22 using the optical fiber 10 configured as described above will be described in detail with reference to FIG.

As shown in FIG. 2, the optical fiber cable 22 includes an optical fiber having the same configuration as the above-described optical fiber 10 as an optical fiber core. The optical fiber cable 22 has a reinforcing layer 24 for reinforcing the optical fiber 10 on the outer peripheral surface thereof.
The reinforcing layer 24 includes a bundle 24A of reinforcing fibers extending in one direction, which is the direction in which the core 12 extends, and a tape 24B that spirally winds the outer periphery of the bundle 24A of reinforcing fibers across the front surface, The bundle 24A of the reinforcing fibers is fixed to the outer periphery of the optical fiber 10 by the tape 24B.

On the outer periphery of the reinforcing layer 24, an outer skin layer 26, which is the outermost layer, is disposed so as to cover the entire periphery. The outer skin layer 26 is formed of a hard synthetic resin so as to function as an outer jacket.

Since the optical fiber cable 22 is configured as described above,
When irradiated with radiation such as rays, β rays, and gamma rays, the radiation enters the second cladding layer 16 of the optical fiber 10,
The dispersed scintillator 20 emits light as described above. Then, the emitted light passes through the first cladding layer 14 without loss, and is further transmitted in the core 12 of the optical fiber 10.

It is needless to say that the present invention is not limited to the configuration of the first embodiment described above, but can be variously modified without departing from the gist of the present invention. For example,
In the first embodiment described above, the clad layer has been described as having a two-layer structure of the first clad layer and the second clad layer. However, without being limited to such a configuration, at least these Needless to say, a multilayer structure of three or more layers including two layers may be employed.

Second Embodiment Next, the configuration of another embodiment of the optical fiber according to the present invention and the optical fiber cable provided with the same will be described in detail with reference to FIG.

As shown in FIG. 3, an optical fiber 30 according to this embodiment has a core 32 made of pure silica glass having optical waveguide properties and extending in one direction, and a core 32 made of pure silica glass.
2, a cladding layer 34 covering the outer peripheral surface of the cladding layer 34 in a state of being completely adhered thereto, and a protective layer 36 covering the entire outer peripheral surface of the cladding layer 34 to protect the cladding layer 34,
It is schematically configured.

Here, since the core 32 has a well-known structure, the description thereof will be omitted. However, in the present invention, the core 32 is not limited to being made of pure silica glass. Needless to say, it may be made of transparent plastics as long as its properties are ensured and durability (life) is ensured.

On the other hand, the above-mentioned cladding layer 34 is made of a polymer synthetic resin such as UV acrylate or Pyrocoat (trade name: Lucent Specialty Fiber Fiber Co., Ltd.).
Technology, Inc. (Connecticut, U.S.A.).

Here, the cladding layer 34 is formed of an inner layer 34A.
And the outer layer 34B.

The outer layer 34B of the cladding layer 34 has
A scintillator 38 that emits light by any of X-rays, α-rays, β-rays, and γ-rays is dispersed by doping or the like. Here, the scintillator 38 is a well-known one, and detailed description thereof will be omitted. In this embodiment, NaI (Tl)
And an inorganic scintillator such as CsI (Tl).

The scintillator 38 that emits X-rays includes Nal (Tl) and CaF2 (E
u), YAP (Ce) and the like are known, and as the scintillator 38 that emits light with α rays, the above-described CsI (Tl)
In addition, BaF2 and the like are known, and as the scintillator 38 that emits light with β rays, the above-described CaF2 (Eu) or B
aF2 and the like are known, and examples of the scintillator 38 that emits gamma rays include NaI (Tl) and CsI (T
l) Other than BaF2, CeF3, B4G3O12, Cd
WO4 and the like are known.

The protective layer 36 is made of a synthetic resin having a predetermined mechanical strength, for example, Tefzel (trade name:
Lucent Specialty Fiber Technology, Inc. (Connecticut, USA).
Note that the protective layer 36 is not an essential component of the optical fiber 30, and the optical fiber 30 is configured even when this is omitted.

Since the optical fiber 30 is configured as described above, when the optical fiber 30 is irradiated with radiation such as α-rays, β-rays, and gamma rays, the optical fiber 30 is dispersed to the outer layer 34 B of the cladding layer 34 by the radiation. Scintillator 38
The energy absorbed by the element is used for excitation together with ionization of atoms (or molecules) constituting the scintillator 38. Then, when the excited atoms return to the original ground state, or when the electron-ion pairs generated as a result of ionization recombine through some process, photons are emitted. This emission of photons is defined as a phenomenon of luminescence due to radiation.

As described above, the scintillator 38 emits light due to the irradiation of the radiation, and this light is introduced into the core 32 through the boundary between the cladding layer 34 and the core 32.

As described above, the light introduced into the core 32 repeats refraction at the boundary surface between the core 32 and the cladding layer 34, and is transmitted inside the core 32 along the extending direction.

As a feature of the present invention, the core 32
In the cladding layer 34 which covers the entire surface of the core 32, the light introduced into the core 32 is not transmitted because the inner layer 34A in which the above-mentioned scintillator 38 is not dispersed exists.
The transmission is performed along the extending direction of the core 32 without receiving the loss at the boundary surface between the core 32 and the inner layer 34 </ b> A of the cladding layer 34.

As described above, the inner layer 34A of the cladding layer 34
It is important that the interface between the core 12 and the inner layer 34A of the cladding layer 34 is important. The thickness of the inner layer 34A can be as thin as possible without any problem.

Here, the above-described optical fiber 30 is not specifically used in the form of an optical fiber cable described below, since the optical fiber 30 itself has insufficient mechanical strength.

Next, the configuration of the optical fiber cable 40 using the optical fiber 30 configured as described above will be described in detail with reference to FIG.

As shown in FIG. 4, the optical fiber cable 40 has an optical fiber having the same configuration as the above-described optical fiber 30 as an optical fiber core. The optical fiber cable 40 has a reinforcing layer 42 for reinforcing the outer peripheral surface of the optical fiber 30.
The reinforcing layer 42 includes a bundle 42A of reinforcing fibers extending along one direction that is the direction in which the core 32 extends, and a tape 42B that spirally winds the outer periphery of the bundle 42A of reinforcing fibers across the front surface, With this tape 42B, the bundle 42A of the reinforcing fibers is fixed to the outer periphery of the optical fiber 30.

On the outer periphery of the reinforcing layer 42, an outer skin layer 44, which is the outermost layer, is provided so as to cover the entire periphery. The outer skin layer 44 is formed of a hard synthetic resin so as to function as an outer jacket.

Since the optical fiber cable 40 is configured as described above,
When radiation such as X-rays, β-rays, and gamma rays are applied, the radiation enters the cladding layer 34 of the optical fiber 30 and is dispersed in the outer layer 34B of the cladding layer 34.
8 will emit light as described above. The emitted light is transmitted to the core 32 of the optical fiber 30 without loss.
Will be transmitted inside.

It is needless to say that the present invention is not limited to the configuration of the above-described second embodiment, but can be variously modified without departing from the gist of the present invention. For example,
In the second embodiment described above, the clad layer is described as including the inner layer and the outer layer, but is not limited to such a configuration, and includes at least the inner layer and the outer layer, for example, sandwiched between the inner layer and the outer layer. Needless to say, a material having an intermediate layer may be used.

As described above, by using the optical fiber cable 22 and the optical fiber cable 40 as detectors of the radioactivity detection system, for example, in a nuclear power plant, a radiation treatment laboratory, a factory, or a clinic, radiation leakage may occur. Is quickly detected, and radiation exposure accidents are prevented beforehand.

Further, the optical fiber cable 22 and the optical fiber cable 40 are the same as the conventional optical fiber cable in that the scintillator material is not dispersed in the core which is the optical waveguide and the cladding layer which forms an interface with the core. And has the same optical transmission performance as the conventional optical fiber cable. This is optimal as a detector for a large-scale monitoring system in which the transmission distance is several hundred meters or more and no leakage occurs at the monitoring location.

Moreover, the optical fiber cable 22 and the optical fiber cable 40 acting as such a detecting device
Is very inexpensive to manufacture, and even if this optical fiber cable is stretched over all parts where there is a risk of radiation leakage, the cost will not be expensive, and a fixed budget Within this, it is possible to construct a radiation detection system very effectively, and security is ensured at a high level.

As described in detail above, according to the present invention,
An optical fiber and an optical fiber cable serving as a detector required for constructing a radiation leak monitoring system are provided at low cost.

[0070]

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a first embodiment of an optical fiber according to the present invention.

FIG. 2 is a perspective view showing the configuration of the first embodiment of the optical fiber cable according to the present invention in a partially broken state.

FIG. 3 is a sectional view showing a configuration of an optical fiber according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing a configuration of an optical fiber cable according to a second embodiment of the present invention in a partially broken state.

[Explanation of symbols]

 Reference Signs List 10 optical fiber 12 core 14 first cladding layer 16 second cladding layer 18 protective layer 20 scintillator 22 optical fiber cable 24 reinforcing layer 24A reinforcing fiber bundle 24B tape 26 jacket layer 30 optical fiber 32 core 34 cladding layer 34A inner layer 34B Outer layer 36 Protective layer 38 Scintillator 40 Optical fiber cable 42 Reinforcing layer 42A Bundle of reinforcing fibers 42B Tape 44 Outer layer

Claims (17)

[Claims] 1. A core having an optical waveguide property and extending in one direction, and a core for covering the entire outer peripheral surface of the core and confining light transmitted through the core in the core. One clad layer, and a second clad layer that covers the entire outer peripheral surface of the first clad layer, and a scintillator that emits light by radiation is dispersed in the second clad layer Is, at least a part of the light emitted by irradiating the scintillator with radiation,
An optical fiber transmitted in the core. 2. A core having an optical waveguide property and extending in one direction, and a clad for covering the entire outer peripheral surface of the core and confining light transmitted through the core in the core. The cladding layer comprises an inner layer and an outer layer, wherein the outer layer has a scintillator that emits light by radiation dispersed therein, and at least light emitted by irradiation of the scintillator with radiation. An optical fiber, a part of which is transmitted in the core. 3. The optical fiber according to claim 1, wherein the scintillator is an inorganic scintillator. 4. The radiation includes at least one of X-rays, α-rays, β-rays and γ-rays, and the scintillator
The optical fiber according to claim 1, wherein the optical fiber emits light by any one of a ray, an α ray, a β ray, and a γ ray. 5. The optical fiber according to claim 1, wherein a protective layer is coated on an outer peripheral surface of said second clad layer. 6. The optical fiber according to claim 2, wherein a protective layer is coated on an outer peripheral surface of said clad layer. 7. The optical fiber according to claim 1, wherein said core is made of quartz glass. 8. The optical fiber according to claim 1, wherein said first cladding layer and said second cladding layer are formed of a transparent polymer synthetic resin. 9. The optical fiber according to claim 2, wherein said cladding layer is formed of a transparent polymer synthetic resin. 10. The optical fiber according to claim 1, wherein said first cladding layer and said second cladding layer are formed of the same material. 11. The optical fiber according to claim 1, wherein said first cladding layer and said second cladding layer are formed of materials having the same refractive index. 12. The optical fiber according to claim 1, wherein said scintillator is dispersed in said second cladding layer by doping. 13. The optical fiber according to claim 2, wherein said scintillator is dispersed in said outer layer by doping. 14. A core having an optical waveguide property and extending in one direction, and a core for entirely covering an outer peripheral surface of the core and confining light transmitted in the core in the core. One clad layer, a second clad layer that covers the entire outer peripheral surface of the first clad layer, and a protective layer that covers the outer peripheral surface of the second clad layer, In the second cladding layer, a scintillator emitting light by radiation is dispersed, and at least a part of light emitted by irradiation of the scintillator with radiation is transmitted through the core. An optical fiber cable, comprising: a reinforcing layer coated on an outer peripheral surface of the protective layer. 15. A core having an optical waveguide property and extending in one direction, and a clad for covering the entire outer peripheral surface of the core and confining the light transmitted through the core in the core. And a protective layer that covers the outer peripheral surface of the cladding layer, the cladding layer has an inner layer and an outer layer, and a scintillator that emits light by radiation is dispersed in the outer layer. At least a part of light emitted by irradiation with radiation is provided with an optical fiber characterized by being transmitted in the core, and a reinforcing layer coated on the outer peripheral surface of the protective layer. An optical fiber cable characterized by the above. 16. The method according to claim 1, wherein the reinforcing layer comprises a bundle of reinforcing fibers extending along the one direction.
16. The optical fiber cable according to 4 or 15. 17. The optical fiber cable according to claim 16, wherein the reinforcing fiber bundle is fixed to the outer periphery of the optical fiber by winding the outer periphery of the bundle with a tape.