JP7145630B2 - OPTICAL FIBER BREAK DETECTION SYSTEM AND OPTICAL FIBER BREAK DETECTION METHOD - Google Patents

Description

The present invention relates to an optical fiber breakage detection system and an optical fiber breakage detection method.

Optical fibers are used in communication, measuring equipment, medical equipment, and the like, and their importance has been increasing in recent years. Among them, in medical equipment, until now, it has been mainly used as a probe for illuminating endoscopes and for image transmission by fiber bundles. The introduction of laser ablation probes is increasing.

In the recent medical technology, less invasive medical procedures using catheters have come to be preferred over highly invasive surgical operations. For example, rather than removing the diseased part by surgical incision, there is a growing practice of cauterizing the diseased tissue by inserting a catheter into the diseased part and cauterizing the diseased tissue with a high-frequency probe or an optical fiber laser irradiation probe housed in the catheter. . Furthermore, optical fiber probes that use light are expected to become more popular in place of electric or ultrasonic probes due to their thinness, flexibility, and biocompatibility.

Here, especially in the use of optical fibers in medical equipment, it is important to accurately detect breaks in the optical fiber in order to avoid incomplete or inappropriate treatment.

Patent document 1 has an optical fiber into which first light and second light having mutually different wavelengths are incident, a detection unit that detects the second light, and a reflection unit that reflects the second light. Then, an optical fiber device that detects an abnormality of the optical fiber by detecting the reflected light of the second light from the reflecting portion is described. Patent Literature 2 describes a laser treatment apparatus having an optical fiber for guiding a treatment laser beam and return light detection means for detecting the output of return light from the optical fiber on the laser incident end side of the optical fiber. there is Patent Document 3 discloses a condensing optical system for condensing a reflected laser beam reflected by a laser emission end face of an optical fiber and emitted again from an incident end face, and light of the reflected laser light condensed by the condensing optical system. A fiber break detection system is described which consists of a photodetector placed on the road. Patent Document 4 has a wavelength swept light source and at least one FBG (fiber Bragg grating) element on an optical path from the wavelength swept light source to an imaging core at the tip of the probe, and the FBG element receives measurement light. A diagnostic imaging apparatus is described for determining whether or not has reached.

JP 2016-71040 A Japanese Patent Application Laid-Open No. 2002-291764 Japanese Patent No. 1489731 JP 2015-66056 A

For example, with an electrical probe, it is possible to detect the failure of the probe by monitoring the electrical resistance. was difficult. In the methods described in Patent Documents 1 to 4, the variation in the detection signal is large due to large fluctuations in the light amount of the reflected light from the laser light emission end side. rice field.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a system and method for accurately detecting an optical fiber breakage.

A system for detecting breakage of an optical fiber, comprising: a first laser device; a first optical fiber into which laser light emitted from the first laser device is incident; a second optical fiber from which the laser light is emitted; a first reflecting portion that reflects single-mode light on the output end side of the second optical fiber; A third optical fiber into which the single-mode light emitted from the incident end and reflected by the first reflecting portion is incident, and the first optical fiber and the third optical fiber are coupled to form a second a first multiplexer connected to the optical fiber of the second optical fiber, the second optical fiber having a first core and a first clad around the first core; and the first cladding have a refractive index difference that allows total internal reflection of the single-mode light, the system is further coupled to the third optical fiber and reflected at the first reflector an optical fiber characterized by comprising a monitor for detecting fluctuations in the amount of light of said single-mode light, and detecting breakage of said second optical fiber from fluctuations in the amount of light of said single-mode light detected by said monitor. A fold detection system is provided.

According to another aspect of the present invention, there is provided a method for detecting breakage of an optical fiber using the above-mentioned optical fiber breakage detection system, based on fluctuations in the light intensity of the single-mode light detected by the monitor.

ADVANTAGE OF THE INVENTION According to this invention, the system and method which detect an optical fiber breakage accurately can be provided.

FIG. 1 is a schematic diagram showing an optical fiber break detection system according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of the second optical fiber according to the first embodiment of the invention. FIG. 3 is a schematic diagram showing an optical fiber break detection system according to a second embodiment of the present invention. FIG. 4 is a schematic diagram showing an optical fiber break detection system according to a third embodiment of the present invention. FIG. 5 is a schematic diagram showing an optical fiber break detection system according to an example of a modified embodiment of the present invention. FIG. 6 is a schematic diagram showing how laser light is guided in an optical fiber breakage detection system according to an example of a modified embodiment of the present invention. FIG. 7 is a schematic diagram showing a light guiding mode of laser light in Example 5. FIG. FIG. 8 is a cross-sectional view for explaining the structure of the second optical fiber.

In the following description, the system and method for detecting fiber optic breaks as an ablation probe is used as an example, but the application of the present invention is not limited to this, and can be used to detect fiber optic breaks in any other application. It can also be applied in detection.

[First embodiment]
An optical fiber breakage detection system according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

First, the configuration of the optical fiber breakage detection system according to this embodiment will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a schematic diagram showing an optical fiber break detection system according to this embodiment. FIG. 2 is a cross-sectional view showing the structure of the second optical fiber 113 according to this embodiment.

The optical fiber breakage detection system 110 according to this embodiment includes a first laser device 111 for oscillating a cauterizing laser, and a first optical fiber into which a laser beam 226 oscillated from the first laser device 111 is incident. 112. The optical fiber breakage detection system 110 also includes a second optical fiber 113 connected to the first optical fiber 112 and from which the laser beam 226 is emitted. and a first reflecting portion 114 that reflects the mode light 225 . The single-mode light 225 reflected by the first reflecting section 114 is light used for detecting breakage of the second optical fiber 113 by a mechanism described later.

The optical fiber break detection system 110 also includes a third optical fiber 116 into which the single-mode light 225 reflected from the first reflector 114 exits from the incident end of the second optical fiber 113; and a first multiplexer 117 that couples the first optical fiber 112 and the third optical fiber 116 and connects to the second optical fiber 113 . The optical fiber breakage detection system 110 further includes a monitor 115 connected to the third optical fiber and detecting variations in the amount of the single-mode light 225 reflected by the first reflector 114 .

The optical fiber breakage detection system 110 according to this embodiment includes a second laser device 118 that oscillates the single-mode light 225, and a fourth optical fiber that receives the single-mode light 225 oscillated from the second laser device 118. 119 and a second multiplexer 120 connecting the fourth optical fiber 119 to the third optical fiber 116 .

The optical fiber break detection system 110 also includes a third laser device 121 that oscillates a visible laser beam that is used to visually determine a position to be cauterized when the second optical fiber 113 is used as an ablation probe. and a fifth optical fiber 122 into which visible laser light emitted from the third laser device 121 enters.

In this embodiment, the first multiplexer 117 connects the first optical fiber 112 and the third optical fiber 116 together with the fifth optical fiber 122 to the second optical fiber 113 . The first multiplexer 117 and the second multiplexer 120 are each configured by, for example, a TFB (Tapered Fiber Bundle).

The wavelength of the laser light 226 oscillated from the first laser device 111 is not particularly limited, and the wavelength can be appropriately adjusted to the application. For example, the wavelengths of the laser light 226 emitted from the first laser device 111 can be 915 nm, 980 nm and 1450 nm, which are absorption peaks of moisture. Further, by setting the wavelength of the laser light 226 oscillated from the first laser device 111 to 1260 nm, which is the absorption peak of fat, it is possible to cauterize only fat while suppressing the temperature rise of water. Furthermore, by using a laser beam 226 of 1500 nm, which is the absorption peak of collagen, it is possible to raise the temperature of collagen and use it for treatment.

The configuration of the first optical fiber 112 is not particularly limited as long as it can efficiently guide the laser light 226 emitted from the first laser device 111 . For example, one having a core made of silica glass having a different refractive index, a clad around the core, and a coating layer around the clad to protect the core and the clad is preferably used. As a material for forming the coating layer, for example, a resin such as an ultraviolet curable resin can be used.

The second optical fiber 113 will be explained using FIG.

The second optical fiber 113 in this embodiment has a first core 221 and a first clad 222 around the first core 221 . The first core 221 and the first clad 222 have a refractive index difference that allows total reflection of single-mode light 225, which is light used to detect optical fiber breaks.

The second optical fiber 113 according to this embodiment further has a second clad 223 around the outer circumference of the first clad 222 and a coating layer 224 around the outer circumference of the second clad 223 . The first clad 222 and the second clad 223 have a refractive index difference that enables total reflection of the laser light 226 emitted from the first laser device 111 .

The first core 221, the first clad 222, and the second clad 223 can each be made of, for example, silica glass, and the material constituting the coating layer can be, for example, an ultraviolet curable resin. Resin can be used.

The laser light 226 emitted from the first laser device 111 may be either single-mode light or multi-mode light, but multi-mode light will be described in this embodiment. As shown in FIG. 2, the single-mode light 225 travels through the first core 221 while being totally reflected at the interface between the first core 221 and the first clad 222 . Also, since the laser light 226 oscillated from the first laser device 111 is multimode light, the first clad 222 and the second clad 223 pass through the first core 221 and the first clad 222 . It advances while undergoing total internal reflection on the boundary surface. That is, the first core 221 and the first clad 222 serve as so-called cores for the laser light 226 emitted from the first laser device 111 .

A laser beam traveling through an optical fiber generally causes bending loss by bending the optical fiber. The angle at which the laser beam is incident on the boundary between the core and the cladding changes according to the curvature of the optical fiber. loss occurs. If the refractive index difference between the core and the clad is large, the critical angle is also small, and bending loss is less likely to occur even if the curvature is increased.

In the present invention, optical fiber breakage is detected by detecting variations in the amount of single-mode light 225 passing through the first core 221 with the monitor 115 as will be described later. Therefore, the bending loss of the single-mode light 225 causes deterioration in the accuracy of detecting folding. For this reason, it is preferable that the difference in refractive index between the first core 221 and the first clad 222 is large. When the refractive index difference between the first core 221 and the first clad 222 is sufficiently large, the curvature that causes bending loss is large, so that when the optical fiber is used, the amount of light detected by the monitor 115 fluctuates. 0 above. Therefore, it is preferable to set the refractive index difference between the first core 221 and the first clad 222 to a certain value or more. Specifically, the refractive index difference between the first core 221 and the first clad 222 is preferably 1% or more, more preferably 1.25% or more.

As long as the first reflecting section 114 can selectively and efficiently reflect the single-mode light 225, the first reflecting section 114 may have any reflecting mechanism. fiber Bragg grating) element.

The position of the first reflecting portion 114 in the second optical fiber 113 may be any position on the light guide line of the second optical fiber 113, and there is no particular limitation. From the viewpoint of detecting a wider range of bends in the optical fiber 113, the first reflecting portion 114 is preferably positioned closer to the output end face of the second optical fiber 113, and most preferably positioned at the output end face.

The reflectance of the single-mode light 225 in the first reflecting section 114 is preferably as high as possible from the viewpoint of increasing the accuracy of optical fiber breakage detection in the monitor 115, and is most preferably total reflection.

The monitor 115 is a device that detects fluctuations in the amount of single-mode light 225 reflected by the first reflector 114 . The breakage of the second optical fiber 113 is detected by the monitor 115 as a change in the amount of single-mode light 225 .

The third optical fiber 116 has a second core (not shown) and at least one cladding (not shown) around the second core, and has a second core and a third core adjacent to the core. The cladding (not shown) has a refractive index difference at their interfaces that allows total reflection of single mode light 225 . From the viewpoint of suppressing bending loss in the third optical fiber 116, the larger the difference in refractive index between the second core and the third clad, the better. Specifically, the refractive index difference between the second core and the third clad is preferably 1% or more, more preferably 1.25% or more.

The third optical fiber 116 preferably has a coating layer around the outermost clad to protect the core and clad. As a material for forming the coating layer, for example, a resin such as an ultraviolet curable resin can be used. The third optical fiber 116 may have the same configuration as the second optical fiber 113 or may have a different configuration, but from the viewpoint of ease of manufacture, it is preferable that the optical fibers have the same configuration.

The configuration of the fourth optical fiber 119 is the same as that of the third optical fiber 116, and may be the same as or different from that of the second optical fiber 113 and/or the third optical fiber 116. can be For ease of manufacture, it is preferable that the second optical fiber 113, the third optical fiber 116 and the fourth optical fiber 119 are all optical fibers having the same configuration.

The configuration of the fifth optical fiber 122 into which the visible laser light is incident is the same as that of the first optical fiber 112 except that the wavelength of the guided laser light is different.

The third laser device 121 and the fifth optical fiber 122 are not essential components, and when other means for specifying the position to be cauterized are provided, or particularly means for specifying the position to be cauterized are provided. If there is no need, there is no particular need to provide it.

Thus, the optical fiber breakage detection system 110 according to this embodiment is configured.

In the optical fiber breakage detection system 110 according to this embodiment, an example is shown in which four first laser devices 111, one second laser device 118, and one third laser device 121 are provided. There is no particular limitation on the number of laser devices, and the number may be one or two or more as appropriate so that a sufficient amount of light for the application of the laser light emitted from each laser device can be obtained.

Any known laser device can be used as the laser device used in the present embodiment as long as it can oscillate a laser beam suitable for the application. From this point of view, a laser device having a semiconductor laser element is preferable.

Further, in the optical fiber breakage detection system 110 according to the present embodiment, an example in which the first reflecting section 114 is provided only at one place on the output end surface of the second optical fiber 113 is shown, but the same as the first reflecting section 114 A plurality of reflecting portions may be provided at any position on the light guide line of the second optical fiber 113 . For example, a laser device similar to the second laser device 118 that oscillates single-mode light beams with different wavelengths is provided, and a plurality of reflection portions similar to the first reflection portion 114 that reflects the respective single-mode light beams are provided. It is possible to identify the position of the optical fiber breakage by providing the two optical fibers 113 at different positions on the light guide line and independently monitoring the single-mode light.

During the operation of the optical fiber breakage detection system 110 according to the present embodiment, the cauterization laser light 226 emitted from the first laser device 111 enters the first optical fiber 112 and passes through the first multiplexer 117. It enters a second optical fiber 113 used as an ablation probe. Thereafter, a cauterization laser beam 226 is emitted from the output end of the second optical fiber 113 to cauterize the affected area.

On the other hand, the visible laser light emitted from the third laser device 121 enters the fifth optical fiber 122 and enters the second optical fiber 113 through the first multiplexer 117 . After that, it is emitted from the emission end of the second optical fiber 113 and used to visually specify the cauterization position of the affected area.

Further, the single-mode light 225 oscillated from the second laser device 118 enters the fourth optical fiber 119 and then enters the third optical fiber 116 through the second multiplexer 120 . The single-mode light 225 further enters the second optical fiber 113 through the first multiplexer 117 and is reflected by the first reflector 114 located on the output end side of the second optical fiber 113 . The single-mode light 225 reflected by the first reflector 114 is guided from the second optical fiber 113 to the third optical fiber 116 by the first multiplexer 117 and passes through the second multiplexer 120. is detected by the monitor 115 .

When the second optical fiber 113 used as an ablation probe is broken, the reflectance of the single-mode light 225 at the position where the break occurs is very small, so the single-mode light detected by the monitor 115 is The amount of light at 225 is greatly reduced, and it is detected as a fold.

When the laser light for detecting optical fiber breakage is multimode light, even a slight bend in the second optical fiber 113 used as the cauterization probe causes the light amount of the laser light detected by the monitor 115 to fluctuate greatly. However, it is difficult to detect folds with high accuracy. In the optical fiber breakage detection system 110 according to this embodiment, as described above, the laser light for detecting breakage detected by the monitor 115 is a single-mode laser light. Therefore, the fluctuation of the light intensity of the laser beam detected by the monitor 115 due to the bending of the second optical fiber 113 used as the cauterization probe is very small, so that it is possible to accurately detect the breakage of the optical fiber. .

[Second embodiment]
An optical fiber breakage detection system 310 according to a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram showing an optical fiber break detection system according to a second embodiment of the present invention. Components similar to those of the optical fiber breakage detection system according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted or simplified.

The configuration of the optical fiber breakage detection system 310 according to the second embodiment does not have the second laser device 118 and the fourth optical fiber 119, except that the second optical fiber 113 is replaced with the second optical fiber 313. are similar to the optical fiber breakage detection system 110 according to the first embodiment.

The second optical fiber 313 differs from the second optical fiber 113 of the optical fiber break detection system 110 according to the first embodiment in that the first core 221 has an element serving as an optical amplification medium.

The element contained in the first core 221 of the second optical fiber 313 is excited by the laser light 226 emitted from the first laser device 111 and emits light. Of the spontaneous emission light generated by light emission, light of a specific wavelength becomes single-mode light 225 and is guided within the second optical fiber 313 .

That is, in the optical fiber breakage detection system 310 according to the second embodiment, the element serving as an optical amplification medium in the first core 221 of the second optical fiber 313 is used for oscillation of the single-mode light 225 . Therefore, the second laser device 118 and the fourth optical fiber 119 in the optical fiber breakage detection system 110 according to the first embodiment can be omitted from the configuration.

If the element that becomes the optical amplification medium in the first core of the second optical fiber 313 is an element that is excited by the laser light 226 oscillated from the first laser device 111 and emits light at a wavelength that becomes single-mode light. , any element can be used. For example, when the wavelengths of the laser light 226 oscillated from the first laser device 111 are 915 nm and 980 nm, which are absorption peaks of moisture, Yb emitted by the laser light 226 at wavelengths in the vicinity of 1070 nm to 1100 nm and 1500 nm to 1600 nm are emitted. Er, which emits light at nearby wavelengths, can be preferably used. Further, when the wavelength of the laser light 226 oscillated from the first laser device 111 is 1450 nm, which is the absorption peak of moisture, Er, which emits light with a wavelength of around 1550 nm by the laser light 226, can be preferably used.

[Third Embodiment]
An optical fiber break detection system 410 according to a third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic diagram showing an optical fiber break detection system according to a third embodiment of the present invention. Components similar to those of the optical fiber breakage detection system according to the first and second embodiments are denoted by the same reference numerals, and descriptions thereof are omitted or simplified.

The configuration of the optical fiber breakage detection system 410 according to the third embodiment is the same as the optical fiber breakage detection system 310 according to the second embodiment, except that it further includes a second reflector 411 .

The second reflecting portion 411 has a reflectance that is not total internal reflection with respect to the single mode light 225 . By having the second reflecting section 411 , a resonator can be configured with the first reflecting section 114 . As a result, the amount of single-mode light 225 detected by the monitor 115 can be increased, and the optical fiber breakage can be detected with higher accuracy.

The reflectance of the second reflecting portion 411 with respect to the single-mode light 225 is preferably in the range of 30% to 70% from the viewpoint of constructing a resonator structure capable of laser oscillation.

In this embodiment, an example in which the second reflector 411 is provided in the vicinity of the connection end of the third optical fiber 116 with the monitor 115 is shown. The second reflecting portion 411 may be provided at any position as long as it is a position where the light can be reflected. For example, the first optical fiber 112 , the third optical fiber 116 , or the second optical fiber 313 can have the second reflecting section 411 closer to the incident end than the first reflecting section 114 .

[Modified embodiment]
The present invention is not limited to the above embodiments, and various modifications are possible.

An optical fiber break detection system 510 according to an example of a modified embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. FIG. 5 is a schematic diagram showing an optical fiber break detection system according to an example of a modified embodiment of the present invention. FIG. 6 is a schematic diagram showing how laser light is guided in an optical fiber breakage detection system according to an example of a modified embodiment of the present invention.

The configuration of the optical fiber breakage detection system 510 according to one example of the modified embodiment is such that the second optical fiber 113 is replaced with the second optical fiber 313, and the second reflector 411, the third reflector 511 and the fourth reflector are provided. It is the same as the optical fiber breakage detection system 110 according to the first embodiment except that it further has a section 512 .

The first laser device 111 oscillates laser light 226 for cauterization, and the second laser device 118 oscillates single-mode light 612. In this respect, the optical fiber breakage detection system 510 according to the example of the modified embodiment is the second embodiment. It is similar to the optical fiber break detection system 310 by form. In addition, the second optical fiber 313 has an element serving as an optical amplification medium in the first core, and the element is excited by the laser light 226 oscillated from the first laser device 111 and emits light to produce a specific is the same as the optical fiber breakage detection system 310 according to the second embodiment in that the light with the wavelength of . . .

As shown in FIG. 6, the single-mode light 612 and the single-mode light 613 have different wavelengths, and both are wavelength-division-multiplexed within the first core 221 of the second optical fiber 313 . The single mode light 612 is reflected by the third reflector 511 and detected by the monitor 115 . Also, the single-mode light 613 is reflected by the first reflector 114 and detected by the monitor 115 .

An optical fiber breakage detection system 510 according to an example of a modified embodiment has a third reflector 511 at a position other than the output end face of the second optical fiber 313 . Further, the point that the first reflector 114 is provided on the output end face of the second optical fiber 313 is the same as the optical fiber breakage detection system 110 according to the first embodiment. Both the third reflecting portion 511 and the first reflecting portion 114 may have any reflecting mechanism as long as they can selectively and efficiently reflect the single-mode lights 612 and 613. For example, a multilayer film It can be a reflective filter, such as a filter, or an FBG (Fiber Bragg Grating) element.

The fourth reflector 512 is similar to the second reflector 411 , but the second reflector 411 is for single-mode light 612 and the fourth reflector 512 is for single-mode light 613 . each have a reflectance that is not total internal reflection. The first reflecting portion 114 and the fourth reflecting portion 512, and the third reflecting portion 511 and the second reflecting portion 411 respectively constitute resonators. This embodiment shows an example in which the second reflecting portion 411 and the fourth reflecting portion 512 are provided on the incident end side of the second optical fiber 313, but the second reflecting portion 411 is the third reflecting portion. 511 and the fourth reflecting portion 512 and the first reflecting portion 114 can form a resonator, respectively, the second reflecting portion 411 and the second reflecting portion 411 and the second reflecting portion 411 are placed at any position. It may have four reflecting portions 512 .

An optical fiber breakage detection system 510 according to an example of a modified embodiment has a third reflector 511 at a position other than the output end face of the second optical fiber 313 . Therefore, by independently detecting the single-mode light 612 and the single-mode light 613 on the monitor 115, the position of the optical fiber breakage can also be specified. For example, in the monitor 115, while there is no change in the light amount of the single-mode light 612, if there is a change in the light amount of the single-mode light 613, the first reflector 114 and the third reflector 511 It can be seen that the optical fiber breakage occurred between

As described above, the optical fiber breakage detection system 510 according to the example of the modified embodiment can accurately detect the breakage of the optical fiber and can also specify the position of the breakage.

Various modifications to the embodiments of the present invention are not limited to the examples of the modified embodiments described above, and can take various configurations. for example. The second optical fiber 313 in one example of the modified embodiment described above may have two or more types of elements serving as optical amplification media in the first core, or may include the third reflecting section 511 and the third reflecting section 511 . A plurality of reflecting portions similar to the reflecting portion 512 of No. 4 may be provided.

<Example>
In each of the embodiments shown below, the first optical fiber 112, the second optical fiber 113, the third optical fiber 116, the fourth optical fiber 119 and the fifth optical fiber 122 are all the same optical fiber. , and has the configuration shown in FIG.

[Example 1]
As an example of the above-described first embodiment, an optical fiber breakage detection system was constructed under the following conditions to detect an optical fiber breakage.

The diameter of the first core 221 is 9 μm, the outer diameter of the first clad 222 is 105 μm, and the outer diameter of the second clad 223 is 125 μm. The NA (numerical aperture) of the laser light 226 of this optical fiber is designed to be 0.23. The interface between the first core 221 and the first clad 222 has a unimodal refractive index distribution, the refractive index difference between the first core 221 and the first clad 222 is 0.35%, and the cutoff wavelength is 1280 nm. That is, a long wavelength of 1280 nm or longer results in single mode transmission.

As the first reflector 114, an FBG element is formed in a portion 1 cm from the output end face of the second optical fiber 113, and the 3 dB reflection wavelength band is designed to be 1310 nm±1 nm. The write length of the FBG element is 1 cm.

When a laser beam of 1280 to 1310 nm was used as the single-mode light 225 and the second optical fiber 113 was bent 180 degrees with a bending radius of 10 mm, the bending loss was 5 dB or less.

Also, a 1310 nm laser beam was used as the single mode light 225, and the second optical fiber 113 was passed through the bend tube, and the minimum bending radius was 10 mm and the length was 10 cm. As a result, the light amount fluctuation of the single-mode light 225 on the monitor 115 was 5 dB or less. As the laser light 226, multimode light with a wavelength of 915 nm was used.

Furthermore, the second optical fiber 113 was caused to break by rapidly moving the second optical fiber 113 in and out of the tube from the state in which the second optical fiber 113 was passed through the curved tube. At this time, the light intensity of the single-mode light 225 on the monitor 115 decreased by 10 dB or more.

As described above, the fluctuation of the light amount of the single-mode light 225 on the monitor 115 is greater when the second optical fiber 113 is broken (10 dB or more) than when the second optical fiber 113 is not broken ( 5 dB or less), and the optical fiber break detection system of this embodiment was able to detect that the second optical fiber 113 was broken.

[Example 2]
As an example of the above-described first embodiment, an optical fiber breakage detection system was constructed under the following conditions to detect an optical fiber breakage.

The diameter of the first core 221 is 5.5 μm, the outer diameter of the first clad 222 is 105 μm, and the outer diameter of the second clad 223 is 125 μm. The NA (numerical aperture) of the laser light 226 of this optical fiber is designed to be 0.23. The interface between the first core 221 and the first clad 222 has a unimodal refractive index distribution, the refractive index difference between the first core 221 and the first clad 222 is 1.5%, and the cutoff wavelength is 1400 nm. That is, a long wavelength of 1400 nm or longer results in single mode transmission.

As the first reflector 114, an FBG element is formed in a portion 1 cm from the output end face of the second optical fiber 113, and the 3 dB reflection wavelength band is designed to be 1480 nm±1 nm. The write length of the FBG element is 1 cm.

When a laser beam of 1400 to 1600 nm was used as the single mode light 225 and the second optical fiber 113 was bent 180 degrees with a bending radius of 10 mm, the bending loss was 0.1 dB or less.

A laser beam of 1480 nm was used as the single-mode light 225, and the second optical fiber 113 was passed through the bending tube with a minimum bending radius of 10 mm and a length of 10 cm. As a result, the light intensity fluctuation of the single-mode light 225 on the monitor 115 was 0.1 dB or less. As the laser light 226, multimode light with wavelengths of 915 nm and 980 nm was used.

Furthermore, the second optical fiber 113 was caused to break by rapidly moving the second optical fiber 113 in and out of the tube from the state in which the second optical fiber 113 was passed through the curved tube. At this time, the light intensity of the single-mode light 225 on the monitor 115 decreased by 10 dB or more.

In this embodiment, the difference in light intensity fluctuation between when the second optical fiber 113 is broken (10 dB or more) and when the second optical fiber 113 is not broken (0.1 dB or less) is measured. It was larger than Example 1, and it was possible to detect the breakage of the second optical fiber 113 more clearly than Example 1.

[Example 3]
As an example of the above-described second embodiment, an optical fiber breakage detection system was configured under the following conditions to detect an optical fiber breakage.

The optical fiber used in this example is the same as the optical fiber used in Example 2, but the first core 221 has Er as an element that serves as an optical amplification medium.

As the first reflector 114, an FBG element is formed in a portion 1 cm from the output end face of the second optical fiber 113, and the 3 dB reflection wavelength band is designed to be 1550 nm±1 nm. The write length of the FBG element is 1 cm.

As the laser light 226, multimode light with a wavelength of 980 nm was used. Light of 1550 nm excited by laser light 226 and generated by light emission of Er was used as single-mode light 225 . The second optical fiber 113 was passed through the bent pipe, and was inserted and withdrawn with a minimum bending radius of 10 mm and a length of 10 cm with a 180 degree twist. As a result, the light intensity fluctuation of the single-mode light 225 on the monitor 115 was 0.1 dB or less.

Furthermore, the second optical fiber 113 was caused to break by rapidly moving the second optical fiber 113 in and out of the tube from the state in which the second optical fiber 113 was passed through the curved tube. At this time, the light intensity of the single-mode light 225 on the monitor 115 decreased by 15 dB or more.

In this embodiment, the difference in light intensity fluctuation between when the second optical fiber 113 is broken (15 dB or more) and when the second optical fiber 113 is not broken (0.1 dB or less) is measured. It was larger than Examples 1 and 2, and it was possible to detect the breakage of the second optical fiber 113 more clearly than Examples 1 and 2. This is because the second optical fiber 113 is bent, so that the area where single-mode light 225 is generated by Er emission is narrowed, and the amount of light reflected by the bent surface is also reduced. This is an effect of the cycle that when the amount of reflected light decreases, the amount of single-mode light 225 generated by excitation of Er by the reflected light also decreases.

[Example 4]
As an example of the above-described third embodiment, an optical fiber breakage detection system was configured under the following conditions to detect an optical fiber breakage.

The optical fiber breakage detection system of this embodiment is the same as that of the third embodiment except that it has a second reflector 411 .

As the second reflecting portion 411, an FBG is formed in a portion 1 cm from the end face of the third optical fiber 116 connected to the monitor 115, and is designed to have a reflectance of 80% at 1550 nm±1 nm. The write length of the FBG is 1 cm.

The second optical fiber 113 was passed through the bent pipe, and was inserted and withdrawn with a minimum bending radius of 10 mm and a length of 10 cm with a 180 degree twist. As a result, the light intensity fluctuation of the single-mode light 225 on the monitor 115 was 0.1 dB or less.

Furthermore, the second optical fiber 113 was caused to break by rapidly moving the second optical fiber 113 in and out of the tube from the state in which the second optical fiber 113 was passed through the curved tube. At this time, the light intensity of the single-mode light 225 on the monitor 115 decreased by 25 dB or more.

In this embodiment, the difference in light intensity fluctuation between when the second optical fiber 113 is broken (25 dB or more) and when the second optical fiber 113 is not broken (0.1 dB or less) is measured. It was larger than Example 3. This is because a resonator is formed before the second optical fiber 113 is broken, but when the second optical fiber 113 is broken, the reflectance of the broken surface is 5% or less at maximum. As a result, the efficiency of the resonator becomes very poor. As a result, a change in the amount of light corresponding to turning on and off of the laser can be obtained substantially by folding. As described above, in this embodiment, it was possible to detect the breakage of the second optical fiber 113 more clearly than in the third embodiment.

[Example 5]
As an example of the above-described first embodiment, an optical fiber breakage detection system was constructed under the following conditions to detect an optical fiber breakage.

The diameter of the first core 221 is 5.3 μm, the outer diameter of the first clad 222 is 105 μm, and the outer diameter of the second clad 223 is 125 μm. The NA (numerical aperture) of the laser light 226 of this optical fiber is designed to be 0.23. The interface between the first core 221 and the first clad 222 has a unimodal refractive index distribution, the refractive index difference between the first core 221 and the first clad 222 is 1.3%, and the cutoff wavelength is 1200 nm. That is, single-mode transmission occurs at long wavelengths of 1200 nm or longer.

As the first reflector 114, an FBG is formed in a portion 1 cm from the output end face of the second optical fiber 113, and the 3 dB reflection wavelength band is designed to be 1260 nm±1 nm. The write length of the FBG is 1 cm.

When a laser beam of 1310 nm was used as the single mode light 225 and the second optical fiber 113 was bent 180 degrees with a bending radius of 10 mm, the bending loss was 0.1 dB or less.

Further, in this embodiment, single-mode light with a wavelength of 1260 nm is used as the laser light 226 . Since the laser beam 226 is single-mode light, it is guided through the first core while being totally reflected at the interface between the first core and the first clad, as shown in FIG. A laser beam of 1310 nm was used as the single-mode light 225 used for detecting the breakage of the second optical fiber. The laser light 226 was wavelength-multiplexed and guided to the first core together with the single-mode light 225 used for detecting the breakage of the second optical fiber.

The second optical fiber 113 was passed through the bent pipe, and was inserted and withdrawn with a minimum bending radius of 10 mm and a length of 10 cm with a 180 degree twist. As a result, the light intensity fluctuation of the single-mode light 225 on the monitor 115 was 0.1 dB or less.

Furthermore, the second optical fiber 113 was caused to break by rapidly moving the second optical fiber 113 in and out of the tube from the state in which the second optical fiber 113 was passed through the curved tube. At this time, the light intensity of the single-mode light 225 on the monitor 115 decreased by 10 dB or more.

In this embodiment, the difference in light intensity fluctuation between when the second optical fiber 113 is broken (10 dB or more) and when the second optical fiber 113 is not broken (0.1 dB or less) is It was as large as in the second embodiment, and it was possible to clearly detect the breakage of the second optical fiber 113 as in the second embodiment.

In this embodiment, the optical fiber having the structure shown in FIG. 2 is used. However, when the laser light 226 is single-mode light, an optical fiber without the second clad is used as shown in FIG. may

110, 310, 410, 510... Optical fiber break detection system 113, 313... Second optical fiber 114... First reflector 115... Monitor 225... Single mode light 226... Laser light 221... First core 222... Second 1 clad 223... second clad 411... second reflective part

Claims (7)

A system for detecting a break in an optical fiber for use in an ablation probe, the system comprising:
a first laser device;
a second laser device that oscillates single-mode light; a first optical fiber into which the laser light oscillated from the first laser device is incident;
a second optical fiber connected to the first optical fiber and emitting the laser light from an emission end ;
a first reflector arranged on the output end side of the second optical fiber and selectively reflecting the single-mode light incident on the second optical fiber ;
a third optical fiber into which the single-mode light emitted from the incident end of the second optical fiber and reflected by the first reflecting portion is incident;
a first multiplexer that couples the first optical fiber and the third optical fiber and connects to the second optical fiber;
The laser light is multimode light having a wavelength different from that of the single mode light,
The second optical fiber has a first core, a first clad around the first core, and a second clad around the first clad,
the first core and the first clad have a refractive index difference that enables total reflection of the single-mode light;
The first clad and the second clad have a refractive index difference that enables total reflection of the laser light,
in the second optical fiber, the laser light propagates through the first core and the first clad, and the single-mode light propagates through the first core;
The system further comprises a monitor connected to the third optical fiber for detecting variations in the amount of the single-mode light reflected by the first reflector,
An optical fiber breakage detection system, wherein the breakage of the second optical fiber is detected when the quantity of the single-mode light detected by the monitor decreases . 2. The optical fiber break detection system according to claim 1, wherein said refractive index difference is 1% or more. 3. The optical fiber break detection system according to claim 1, wherein said refractive index difference is 1.25% or more. a fourth optical fiber into which the single-mode light oscillated from the second laser device is incident;
a second multiplexer that connects the fourth optical fiber to the third optical fiber;
The optical fiber break detection system according to any one of claims 1 to 3, further comprising: The optical fiber break detection system according to any one of claims 1 to 4, wherein the first core has an element serving as an optical amplification medium. having a reflectance that is not total reflection with respect to the single-mode light on the incident end side of the first reflecting portion of the first optical fiber, the third optical fiber, or the second optical fiber; The optical fiber break detection system according to any one of claims 1 to 5, comprising a second reflector. A method for detecting breakage of an optical fiber, wherein the optical fiber breakage detection system according to any one of claims 1 to 6 is used, and the light amount of the single-mode light detected by the monitor is reduced. A method of detecting fiber breaks.

Images