JP5082073B2 - Method for adjusting fiber Bragg grating, method for manufacturing optical component having fiber Bragg grating, and apparatus for manufacturing the same - Google Patents

Description

  The present invention relates to a method for erasing a fiber Bragg grating, a method for adjusting a fiber Bragg grating, a method for manufacturing an optical component equipped with a fiber Bragg grating, and a manufacturing apparatus for the optical component.

  In recent years, an optical component composed of an optical fiber in which a fiber Bragg grating (hereinafter simply referred to as “FBG”) is formed is used as a kind of strain sensor.

  The FBG is a diffraction grating (grating) formed by alternately arranging a portion having a high refractive index and a portion having a low refractive index at a certain interval in the longitudinal direction in a part of the core of the optical fiber, When light is incident on the optical fiber on which the FBG is formed, reflected light based on the diffraction conditions in the diffraction grating is generated.

Here, when the pitch of the high refractive index portion and the low refractive index portion of the FBG that are alternately continuous is Λ, and the effective refractive index of the FBG portion is n _eff , the FBG has λ _B = 2 × n _eff × Λ. When an optical component composed of an optical fiber having such an FBG is used as a strain sensor, a portion having a high refractive index is refracted by the strain generated in the FBG portion. The wavelength of the reflected light fluctuates due to the change in the pitch of the low rate part, and the amount of distortion is measured from the fluctuation amount of this wavelength.

  When an FBG is formed on an optical fiber, a phase mask is usually disposed along the optical fiber, and the optical fiber core is irradiated with ultraviolet laser light through the phase mask to thereby adjust the refractive index of the optical fiber core. Different regions are formed at predetermined intervals.

  Here, the optical fiber is an optical fiber having a so-called photorefractive effect (photoexcitation refractive index change) in which the refractive index of the core is changed by irradiation with ultraviolet light, or a photosensitive effect, and is generally germanium in the core portion. Optical fibers doped with atoms are often used.

  Also, the phase mask is provided with a plurality of slits in the longitudinal direction of the optical fiber on the surface facing the optical fiber at a pitch twice the pitch Λ of the high refractive index portion and the low refractive index portion formed on the FBG. It is a filter.

In the phase mask, when an ultraviolet laser beam is incident, the ultraviolet laser beam is diffracted and applied to an optical fiber, and an interference fringe having a pitch Λ is generated in the optical fiber to form an FBG (for example, (See Patent Document 1).
JP 2005-127744 A

  However, the FBG formed on the optical fiber is likely to have a large deviation from the desired characteristics due to manufacturing variations. For example, when used as a strain sensor, sufficient detection accuracy may not be obtained.

  In view of such a current situation, the present inventors have conducted research and development to provide an optical component having an FBG with high manufacturing accuracy, and have achieved the present invention.

The FBG adjustment method of the present invention is a method for adjusting a fiber Bragg grating formed by irradiating an optical fiber capable of adjusting the refractive index of a core by irradiation of ultraviolet light with interference light of ultraviolet laser light, A nitrogen substitution step of replacing the inside of the container containing the optical fiber on which the fiber Bragg grating is formed with nitrogen , and the fiber Bragg grating is irradiated with ultraviolet light having a wavelength of 146 nm in the container purged with nitrogen in the nitrogen substitution step. The step of erasing the grating, the step of irradiating the optical fiber from which the fiber Bragg grating has been erased in the erasing step with the interference light of the ultraviolet laser beam having a wavelength of 248 nm to re-form the fiber Bragg grating, and the inspection of the optical fiber Incident light Adjusting the fiber Bragg grating by irradiating the fiber Bragg grating with ultraviolet light having a wavelength of 146 nm while measuring the wavelength of the light reflected by the Bragg grating, and adjusting the erase and re-forming steps According to the steps, the refractive index of the fiber Bragg grating was adjusted .

Further, in the container is reduced to below atmospheric pressure in the adjustment Sources step, characterized in that ultraviolet light in a vacuum state, moreover, the optical fiber is an optical fiber doped with germanium atoms in the core It forms a FBG is irradiated with ultraviolet laser light having a wavelength of 248 nm, the adjustment Sources steps, and it has the characteristics to be irradiated with ultraviolet light having a wavelength of 146nm to FBG portion.

In the method of manufacturing an optical component including the FBG according to the present invention, a fiber Bragg grating formed by irradiating interference light of ultraviolet laser light is provided on an optical fiber capable of adjusting the refractive index of the core by irradiation of ultraviolet light. A method of manufacturing an optical component comprising: a nitrogen replacement step in which a container containing an optical component on which a fiber Bragg grating is formed is replaced with nitrogen; and a wavelength in the fiber Bragg grating in a container in which nitrogen replacement is performed in the nitrogen replacement step. Irradiating 146 nm ultraviolet light to erase the fiber Bragg grating, and irradiating the optical component from which the fiber Bragg grating was erased in the erasing step with interference light of an ultraviolet laser beam having a wavelength of 248 nm Reshaping and testing the optical fiber Adjusting the fiber Bragg grating by irradiating the fiber Bragg grating with ultraviolet light having a wavelength of 146 nm while measuring the wavelength of the light that is incident and reflected by the fiber Bragg grating. The refractive index of the fiber Bragg grating was adjusted by the forming step and the adjusting step .

Further, the optical component manufacturing apparatus including the FBG of the present invention includes a fiber Bragg grating formed by irradiating the interference light of the ultraviolet laser light on the optical fiber capable of adjusting the refractive index of the core by the irradiation of the ultraviolet light. a container for accommodating the optical components were, a nitrogen cylinder for introducing nitrogen into the container, the fiber Bragg grating formed in the accommodating light component in the container, the first light source that shines ultraviolet light having a wavelength of 146nm irradiation If, comprising a second light source to the optical component that the interference light of ultraviolet laser light having a wavelength of 248nm irradiation shine, and after clearing the fiber Bragg grating by irradiation of ultraviolet light from the first light source, second light source The fiber Bragg grating is re-formed on the optical component by irradiating the interference light of the ultraviolet laser light from, and then the re-formed fiber Bragg grating The refractive index of the grayed was be adjusted by the irradiation of ultraviolet light from the first light source.

  In the present invention, in an optical component composed of an optical fiber, the FBG formed at a predetermined position of the optical fiber is irradiated with ultraviolet light to adjust the refractive index of the FBG portion. By adjusting after the formation, it is possible to manufacture an optical component including the FBG with suppressed characteristic variation.

  In particular, the FBG can be erased by making the refractive index of the FBG uniform by adjusting the irradiation amount of ultraviolet light applied to the FBG, and the FBG can be formed again after the FBG is erased.

  Moreover, when irradiating ultraviolet light to adjust the refractive index of the FBG portion, the inside of the container containing the optical fiber equipped with the FBG is depressurized to atmospheric pressure or lower, and irradiated with ultraviolet light in a reduced pressure state, The fluctuation of the transmission attenuation factor of the FBG at the time of change can be suppressed, and an FBG that is resistant to temperature changes can be manufactured.

  In the present invention, when an optical fiber on which a fiber Bragg grating (hereinafter simply referred to as “FBG”) is irradiated with ultraviolet light, the refractive index of the portion having a high refractive index and a portion having a low refractive index in the FBG. By utilizing the fact that the refractive index fluctuation rate is larger in the low refractive index portion than in the high refractive index portion, the refractive index of the low refractive index portion is changed to be larger than the refractive index of the high refractive index portion. The effective refractive index of the portion is adjusted.

  As described above, the optical component composed of the optical fiber in which the FBG is formed can adjust the characteristics of the FBG by irradiation with ultraviolet light, and can provide an optical component in which manufacturing variation is suppressed. .

  In particular, when the optical fiber is an optical fiber having a core doped with germanium atoms and an FBG is formed by irradiating the optical fiber with an ultraviolet laser beam having a wavelength of 248 nm through a phase mask, the FBG portion has a wavelength of, for example, 146 nm. The refractive index can be adjusted with high accuracy by irradiating the ultraviolet light, and the FBG can be erased by adjusting the irradiation time to make the refractive index of the FBG portion uniform.

  When adjusting the refractive index of the FBG portion by irradiating the FBG portion of the optical fiber with the ultraviolet light, the FBG portion is housed in a nitrogen-substituted container and irradiated with the ultraviolet light, so that the refractive index of the FBG portion is increased. Can be adjusted stably.

  Moreover, the inside of the container is depressurized to an atmospheric pressure or lower and irradiated with ultraviolet light in a depressurized state, whereby fluctuations in the attenuation rate at the time of temperature change can be suppressed, and an FBG that is resistant to temperature change can be formed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of an optical component manufacturing apparatus including the FBG according to the present embodiment.

  In the optical component manufacturing apparatus, a container 11 that houses an optical component A equipped with an FBG, and a measuring instrument 13 that measures the wavelength of light that is incident on the optical component A in the container 11 and reflected by the FBG. , And a light source 14 for irradiating the FBG portion with ultraviolet light. In FIG. 1, 15 is a nitrogen cylinder that stores nitrogen introduced into the container 11 to replace the inside of the container 11 with nitrogen, and 16 is an inspection light for making the inspection light incident on the optical component A accommodated in the container 11. Light source.

  The optical component A is an optical fiber having a core doped with germanium atoms, and an FBG is formed by irradiating a predetermined position with an ultraviolet laser beam having a wavelength of 248 nm through a phase mask.

  In this embodiment, the container 11 includes a cylindrical storage portion 11a in which the optical component A is stored, and a cylindrical optical path along the irradiation light path of the ultraviolet light that irradiates the optical component A stored in the storage portion 11a. It consists of part 11b. The container 11 is made of stainless steel.

  Both ends of the accommodating portion 11a are closed by a closing plate 11a-1 having a connector C to which an optical fiber is connected, and the closing plate 11a-1 is detachable from the receiving portion 11a. The optical component A is installed between the closing plates 11a-1 via the connector C, and after the optical component A is installed between the closing plates 11a-1, the closing plate 11a-1 is attached to the accommodating portion 11a, and the optical component A is mounted. A can be accommodated in the accommodating portion 11a.

  When the optical component A is installed between the blocking plates 11a-1, the FBG portion of the optical component A is installed on the irradiation light path of ultraviolet light.

  The accommodating portion 11a is not limited to the above-described form as long as the accommodated optical component A can be maintained in a nitrogen atmosphere, and the optical component A may be arranged in the accommodating portion 11a in an appropriate form.

  One closing plate 11a-1 is connected to the inspection light source 16 via the connecting optical fiber f1, and the other closing plate 11a-1 is connected to the measuring instrument 13 via the connecting optical fiber f2. doing. Note that both ends of the optical fiber may be drawn out from the optical component A in the housing portion 11a and directly connected to the light source for inspection 16 and the measuring instrument 13, respectively.

  In this embodiment, the inspection light source 16 uses the ASE (Amplified Spontaneous Emission) light source to make predetermined light incident on the optical component A.

  The measuring instrument 13 uses the optical spectrum analyzer in this embodiment, and measures the wavelength of the reflected light by detecting the decrease in the intensity of the reflected light portion due to the reflection by the FBG in the optical component A by the measuring instrument 13. .

  The end portion of the optical path portion 11b that protrudes from the housing portion 11a is connected to the light source 14 through an atmosphere adjustment tube 17 that is provided to adjust the atmosphere in the container 11.

  In this embodiment, the light source 14 uses a krypton excimer lamp that can irradiate ultraviolet light having a wavelength of 146 nm, and can irradiate the FBG portion of the optical component A of the container 11 with ultraviolet light having a wavelength of 146 nm.

  The atmosphere adjusting pipe 17 is provided with a first connecting pipe 17a on the upper end side, a second connecting pipe 17b on the lower end side, and connected to a nitrogen cylinder 15 on the second connecting pipe 17b. Nitrogen is introduced into the container 11 to create a nitrogen atmosphere. Although nitrogen is naturally released from the first connecting pipe 17a as nitrogen is introduced into the container 11 by the nitrogen cylinder 15, an appropriate intake pump is provided so that the nitrogen in the container 11 can be replaced smoothly. Alternatively, the inside of the container 11 may be in a reduced pressure state, and if possible, it is desirable to reduce the pressure below the atmospheric pressure as will be described later. Although not shown, the second connecting pipe 17b is provided with an appropriate flow rate adjusting valve to adjust the supply amount of nitrogen.

  In the optical component manufacturing apparatus configured as described above, the FBG of the optical component A is adjusted as follows.

  First, the optical component A on which the FBG is formed is installed between the closing plates 11 a-1, the closing plate 11 a-1 is mounted on the storage portion 11 a, and the optical component A is stored in the container 11.

  Next, the light source for inspection 16 and the measuring instrument 13 are connected to the optical component A using the optical fibers f1 and f2 for connection, and nitrogen is fed from the nitrogen cylinder 15 into the container 11 so that the inside of the container 11 is filled with nitrogen. Has been replaced.

  When the inside of the container 11 is replaced with nitrogen, the inspection light is incident on the optical component A from the light source 16 for inspection, and the wavelength of the reflected light from the FBG of the optical component A is measured by the measuring device 13 while the wavelength from the light source 14 is measured. Irradiation of 146 nm ultraviolet light is started.

In the FBG of the optical component A, the effective refractive index of the FBG portion changes, for example, from the effective refractive index n ₁ before irradiation with ultraviolet light to the effective refractive index n ₂ (> n ₁ ) after irradiation with irradiation with ultraviolet light. As a result, the wavelength of the reflected wave at the FBG is changed from λ ₁ = 2 × n ₁ × Λ before irradiation with ultraviolet light to λ ₂ = 2 × n ₂ × Λ before irradiation with ultraviolet light. As shown in FIG. 2, the bottom wavelength of the equivalent loss measured by the measuring instrument 13 is shifted.

  FIG. 3 is a graph showing the relationship between the irradiation time of ultraviolet light having a wavelength of 146 nm and the center wavelength of the reflected wave by the FBG.

  FIG. 4 is a graph showing the relationship between the irradiation time and the center wavelength of the reflected wave by the FBG when irradiation with ultraviolet light having a wavelength of 172 nm is performed using a xenon excimer lamp as a light source.

  As shown in FIGS. 3 and 4, it can be seen that the wavelength of the reflected wave by the FBG can be adjusted by irradiation with ultraviolet light, and in particular, it can be adjusted by the irradiation time. In the optical component manufacturing apparatus, when the value detected by the measuring instrument 13 reaches a preset value, the irradiation of ultraviolet light is stopped to finish the adjustment of the FBG, and the optical component A is taken out from the container 11.

As shown in FIGS. 3 and 4, the shift amount of each reflected wave is about 1.6 pm / min when the wavelength is 172 nm, and is about 0.8 pm / min when the wavelength is 146 nm. Although it seems that the wavelength of the reflected wave can be shifted more efficiently, the xenon excimer lamp irradiated with ultraviolet light with a wavelength of 172 nm is 15 mW / cm ² , whereas krypton irradiated with ultraviolet light with a wavelength of 146 nm is used. because excimer lamp is a 1.8 mW / cm ^2, amount of shift per minute at a light intensity of 1.0 mW / cm ² in the case of wavelength 172nm is about 0.1 pm / min, when the wavelength 146nm Is about 0.4 pm / min, and it can be seen that it is more efficient to use ultraviolet light having a wavelength of 146 nm.

  Furthermore, the graph which showed the time fluctuation of the wavelength of the reflected wave by FBG after completion | finish of irradiation of the ultraviolet light of wavelength 146nm shown in FIG. 5, and the reflection wave of FBG after completion | finish of irradiation of the ultraviolet light of wavelength 172nm shown in FIG. As shown in the graph showing the time variation of the wavelength, when the wavelength of 172 nm is used, a large variation occurs after the irradiation of the ultraviolet light, whereas when the wavelength of 146 nm is used, the irradiation of the ultraviolet light is completed. It can be seen that the FBG can be adjusted reliably without a large fluctuation occurring later.

  As described above, in the optical fiber in which the FBG is formed, the wavelength of the reflected wave in the FBG can be adjusted by irradiating the ultraviolet light, and in particular, a portion having a high refractive index and a low refractive index in the core of the optical fiber. In the FBG formed by alternately and continuously with a portion having a predetermined pitch Λ, the refractive index of the portion having a low refractive index fluctuates more greatly than the portion having a high refractive index due to irradiation with ultraviolet light. By irradiating with time, the difference in refractive index can be reduced and the FBG can be erased.

  Therefore, for example, as shown in FIG. 7, in the accommodating portion 11a ′ that accommodates the optical component A ′ composed of an optical fiber, the optical component A ′ in the accommodating portion 11a ′ is irradiated with ultraviolet light for adjusting the FBG. A first optical path portion 11b ′ along the irradiation optical path for performing the second optical path A for irradiating the optical component A ′ in the housing portion 11a ′ with the ultraviolet laser beam for forming the FBG. An optical path portion 11c ′ is provided, and a predetermined ultraviolet light is irradiated to the FBG portion of the optical component A ′ in the accommodating portion 11a ′ to erase the FBG. Then, the phase is transferred from the second optical path portion 11c ′ to the optical component A ′. The FBG may be re-formed by irradiating an ultraviolet laser beam having a wavelength of 248 nm through the mask D. Further, the wavelength of the reflected wave may be adjusted by irradiating the reformed FBG with ultraviolet light.

  When forming the FBG, the phase mask D is preferably arranged as close as possible to the optical fiber constituting the optical component A ′. However, if the phase mask D is always arranged close to the optical fiber, , The ultraviolet light irradiated for adjusting the FBG may be reflected by the phase mask D to cause unevenness in the refractive index of the core of the optical fiber.

  Therefore, when irradiating ultraviolet light for adjusting the FBG, it is desirable to keep the phase mask D away from the optical fiber. As shown in FIG. 7, the irradiation direction L1 of the ultraviolet light used for adjusting the FBG is The phase mask D is moved in parallel to the rear side of the optical fiber in the irradiation direction L1 of the ultraviolet light used for adjusting the FBG by arranging the irradiation direction L2 of the ultraviolet laser beam used for forming the FBG in an intersecting state. By retracting, it is possible to prevent the reflected wave from the phase mask D from hitting the optical fiber, and to prevent the refractive index of the core of the optical fiber from becoming uneven.

  When forming the FBG, the FBG can be formed by moving the phase mask D so that the ultraviolet laser light can be irradiated through the phase mask D. In this case, there is no change in the distance of the phase mask D from the optical fiber before the phase mask D is saved and after the phase mask D is restored, and the phase mask D can be arranged at an appropriate position.

  The formation of the FBG is not limited to the case where it is performed using the phase mask D, and may be performed, for example, by a two-beam interference method.

  In the embodiment described above, the inside of the container 11 is only replaced with nitrogen, but after the inside of the container 11 is replaced with nitrogen, by irradiating the adjustment ultraviolet light while reducing the pressure inside the container 11 to the atmospheric pressure or lower, An FBG having a small variation in the transmission attenuation factor of the FBG when the temperature changes can be formed.

  That is, as shown in FIG. 8, when an FBG is formed by irradiating an optical fiber with an ultraviolet laser beam having a wavelength of 248 nm, not only does the reflected wavelength of the FBG shift to the longer wavelength side as the temperature increases, The transmission attenuation amount of the FBG is to be reduced.

  In contrast, after irradiating an optical fiber with an ultraviolet laser beam having a wavelength of 248 nm to form an FBG, the optical fiber is irradiated with ultraviolet light having a wavelength of 172 nm using a xenon excimer lamp in a nitrogen atmosphere at atmospheric pressure or lower. When performed, as shown in FIG. 9, the reflection wavelength of the FBG shifts to the longer wavelength side as the temperature increases, but the decrease in the transmission attenuation amount of the FBG could be suppressed.

  FIG. 10 shows a comparison of the change in transmission attenuation with respect to temperature according to the presence or absence of ultraviolet light irradiation in a reduced pressure state. When ultraviolet light is irradiated in a reduced pressure state, the phenomenon of transmission attenuation is observed up to 130 ° C. It was confirmed that it was resistant to temperature changes. Therefore, an FBG that can be used in a harsh temperature environment can be formed by irradiating the FBG produced only by the irradiation of the ultraviolet laser light with the ultraviolet light in a reduced pressure state.

  The decompressed state may be a state below atmospheric pressure, and it is desirable to reduce the pressure as much as possible, preferably 100 Pa or less. By reducing the pressure inside the container containing the optical fiber, the loss of the irradiated ultraviolet light can be reduced, and the generation of heat due to the irradiation of the ultraviolet light can be suppressed, and the quality can be stabilized. .

  The irradiation time of the ultraviolet light is determined in consideration of the intensity of the ultraviolet light to be irradiated, and is at least more than the extent that the reflected wavelength of the FBG is shifted to the long wavelength side due to the irradiation of the ultraviolet light, The longer it is, the better. Therefore, when forming the FBG, it is desirable to form the FBG in consideration of adjusting the refractive index of the FBG by irradiation with ultraviolet light, and by adjusting the refractive index of the FBG by irradiation with ultraviolet light, In addition, it is possible to improve the resistance against the temperature change of the FBG.

  Note that the ultraviolet light irradiated for the purpose of improving the resistance of the FBG to the temperature change and the ultraviolet light irradiated for the purpose of adjusting the refractive index of the FBG need not be the same. After performing an ultraviolet light irradiation process for the purpose of improvement, an ultraviolet light irradiation process for adjusting the refractive index of the FBG may be performed.

It is explanatory drawing of the manufacturing apparatus of the optical component concerning embodiment of this invention. It is explanatory drawing of adjustment of the fiber Bragg grating by irradiation of an ultraviolet light. It is the graph which showed the relationship between the irradiation time of the ultraviolet light of wavelength 146nm, and the center wavelength of the reflected wave by FBG. It is the graph which showed the relationship between the irradiation time at the time of irradiating the ultraviolet light of wavelength 172nm, and the center wavelength of the reflected wave by FBG. It is the graph which showed the time change of the wavelength of the reflected wave by FBG after completion | finish of irradiation of the ultraviolet light of wavelength 146nm. It is the graph which showed the time change of the wavelength of the reflected wave by FBG after completion | finish of irradiation of the ultraviolet light of wavelength 172nm. It is explanatory drawing of the manufacturing apparatus of the optical component of other embodiment. It is a graph which shows the change of the transmission attenuation amount of FBG by a temperature change. It is a graph which shows the change of the transmission attenuation amount of FBG by a temperature change. It is a graph which shows the change of the transmission attenuation amount of FBG by a temperature change.

Explanation of symbols

A Optical component C Connector
11 containers
11a containment
11a-1 Blocking plate
11b Optical path
13 Measuring instrument
14 Light source
15 Nitrogen cylinder
16 Light source for inspection light
17 Atmosphere control tube
17a First connecting pipe
17b Second connecting pipe

Claims (4)

An adjustment method of a fiber Bragg grating formed by irradiating an optical fiber capable of adjusting the refractive index of a core by irradiation of ultraviolet light and irradiating interference light of ultraviolet laser light,
A nitrogen substitution step of substituting nitrogen in a container containing the optical fiber in which the fiber Bragg grating is formed;
Irradiating the fiber Bragg grating with ultraviolet light having a wavelength of 146 nm in the container purged with nitrogen in the nitrogen substitution step, and erasing the fiber Bragg grating;
Irradiating the optical fiber from which the fiber Bragg grating is erased in the erasing step with interference light of an ultraviolet laser beam having a wavelength of 248 nm to re-form the fiber Bragg grating;
Adjusting the fiber Bragg grating by irradiating the fiber Bragg grating with ultraviolet light having a wavelength of 146 nm while measuring the wavelength of light reflected by the fiber Bragg grating by injecting inspection light into the optical fiber;
And adjusting the refractive index of the fiber Bragg grating by the erasing step, the re-forming step, and the adjusting step.   2. The fiber Bragg grating adjustment method according to claim 1, wherein, in the adjusting step, the inside of the container is depressurized to an atmospheric pressure or lower and the ultraviolet light is irradiated in a depressurized state. A method of manufacturing an optical component comprising a fiber Bragg grating formed by irradiating interference light of ultraviolet laser light to an optical fiber capable of adjusting the refractive index of the core by irradiation of ultraviolet light,
A nitrogen substitution step of substituting nitrogen in a container containing the optical component in which the fiber Bragg grating is formed;
Irradiating the fiber Bragg grating with ultraviolet light having a wavelength of 146 nm in the container purged with nitrogen in the nitrogen substitution step, and erasing the fiber Bragg grating;
Irradiating the optical component from which the fiber Bragg grating has been erased in the erasing step with interference light of an ultraviolet laser beam having a wavelength of 248 nm to re-form the fiber Bragg grating;
Adjusting the fiber Bragg grating by irradiating the fiber Bragg grating with ultraviolet light having a wavelength of 146 nm while measuring the wavelength of light reflected by the fiber Bragg grating by injecting inspection light into the optical fiber;
And adjusting the refractive index of the fiber Bragg grating by the erasing step, the re-forming step, and the adjusting step. A container that contains an optical component including a fiber Bragg grating formed by irradiating interference light of ultraviolet laser light on an optical fiber capable of adjusting the refractive index of the core by irradiation of ultraviolet light;
A nitrogen cylinder for introducing nitrogen into the container;
A fiber Bragg grating formed in the housing optical components within said container, a first light source that shines ultraviolet light having a wavelength of 146nm irradiation,
A second light source that shines the interference light of ultraviolet laser light having a wavelength of 248nm light of the prior climate component,
With
After erasing the fiber Bragg grating by irradiation with ultraviolet light from the first light source, re-forming a fiber Bragg grating on the optical component by irradiating interference light of ultraviolet laser light from the second light source, Thereafter, the refractive index of the regenerated fiber Bragg grating is adjusted by irradiation of ultraviolet light from the first light source .

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