JP5106905B2 - Optical fiber end face protection structure - Google Patents

Description

  The present invention relates to a protective structure for a light emitting end of an optical fiber.

  Optical fiber widely used as an optical transmission medium is stable because it tends to reduce transmission loss due to dust and dirt adhering to the output end face of the optical fiber and damage the end face due to seizure of deposits when transmitting high output light. There is a problem of lowering the beam quality and beam quality. In particular, when transmitting short wavelength light having a high energy density of 450 nm or less, the emission end face is easily contaminated.

  Further, when light is guided to the optical fiber, a part of the guided light is reflected at the light emitting end face, and so-called return light is generated that travels backward in the optical fiber. Since this return light increases in proportion to the power of the incident light, when high output incident light is used, the optical fiber itself and the connection are connected even if special treatment for antireflection is applied to the light exit end face. It is also known to adversely affect optical devices that have been used.

  In particular, in the case of a fiber bundle or the like that collectively emits light from a plurality of light sources using a plurality of optical fibers, the power of the plurality of light sources is collected and emitted at the light emitting end surface, Contaminant deposition speed and return light power are increased. Further, in the fiber bundle, it is preferable to reduce the amount of return light as much as possible because the return light may affect and damage the adhesive used to bundle the fibers.

  Patent Document 1 discloses an optical fiber end face structure in which a coreless fiber is fusion-bonded to an output end face of an optical fiber, and a coating material having a refractive index higher than that of the coreless fiber is provided around the coreless fiber. Yes. In Patent Document 1, end face damage can be prevented by the coreless fiber, and by controlling the length of the coreless fiber, the coreless fiber is effectively returned from the coating material portion having a refractive index higher than the refractive index of the coreless fiber. It is described that light can be emitted to prevent retrograde return light in the optical fiber.

Patent Document 2 discloses an optical fiber terminal in which one end face of a coreless fiber made of a material having substantially the same refractive index as the core is joined to the end face of an optical fiber having a core-clad structure. An optical fiber terminal is disclosed in which the optical path length of the coreless fiber is set so that the light incident on the fiber is emitted with a beam diameter within the outer diameter of the exit end of the coreless fiber. It is described that with such a configuration, the light emitted from the optical fiber can be effectively spread and emitted, and the return loss can be reduced by increasing the reflection loss.
JP 2005-303166 A International Publication No. 2004/053547 Pamphlet

  In the optical fiber end face structure of Patent Document 1 and the optical fiber terminal of Patent Document 2, both end face protection members (coreless fibers) attached to the output end of the optical fiber are bonded by fusion or the like. When the optical fiber and the end face protection member are bonded together by fusion, the difference in aperture is limited. If the aperture difference between the optical fiber to be fused and the end face protection member is large, the difference between the heat capacities of both is large, and thus the difference in softening speed becomes large. As a result, the optical fiber having a small diameter during softening of the end face protection member The dopant in the core diffuses into the cladding. When the dopant diffuses into the cladding, the optical fiber weakens the light confinement effect, increases the radiation loss, and degrades the transmission characteristics of the optical fiber itself. Therefore, in the case of bonding by fusion, the difference in aperture between the optical fiber and the end surface protection member is limited, and it is difficult to fuse the end surface protection member having a diameter of twice or more.

  In order to collectively protect the end faces of a plurality of optical fibers and the end face of the fiber bundle, the end face protecting member is fused to at least twice the diameter of each optical fiber. Therefore, it is difficult to have a configuration in which the end face protection member is bonded by fusion bonding, and neither Patent Document 1 nor Patent Document 2 has any description for the end faces of a plurality of optical fibers.

  Further, the adhesion of contaminants is a phenomenon that occurs similarly at the exit end of the end face protection member even though the exit end of the optical fiber is protected, although the contamination rate is slow. Therefore, it is preferable that the end face protection member has a structure that can be attached and detached so that maintenance can be performed.

As a connection method for connecting the light emitting end face of the optical fiber and the end face protection member without requiring a heat softening process such as a fusion technique and making the end face protection member detachable, an optical contact may be mentioned. However, the optical contact abuts when light with a high energy density, particularly light with a short wavelength of 450 nm or less, is guided, or when UV cleaning is used to remove contaminants at the exit end of the optical fiber. Since the optical fiber and the constituent material of the end face protection member (quartz, SiO _2, etc.) stick together by causing some reaction at the part, the contact surfaces are damaged at the time of attachment / detachment, so it is difficult to make a detachable structure This has been confirmed by the applicant.

  The present invention has been made in view of the above circumstances, and provides an optical fiber end face protection structure in which end faces of a plurality of optical fibers can be collectively protected and an end face protection member is detachable, and a fiber bundle having the same. It is for the purpose.

The optical fiber end face protection structure of the present invention includes a plurality of optical fibers that emit incident light from the light exit end, and
A translucent optical member having substantially the same refractive index as the core material of the plurality of optical fibers, and allowing light emitted from the light exit ends of the plurality of optical fibers to enter and exit from a light incident end;
An end face of the optical fiber having a protective medium interposed between the light exit ends of the plurality of optical fibers and the light entrance end of the light transmissive optical member, and preventing adhesion between the light exit ends and the light entrance end. A protective structure,
The light incident end face of the translucent optical member has a size equal to or larger than the light emitting end face of the plurality of optical fibers.
The plurality of optical fibers and the translucent optical member are detachable via the protective medium.

  In the present specification, the “translucent optical member” is defined as an optical member having a transmittance of 90% or more at the wavelength of light incident on the optical member.

  In addition, here, the “protective medium that prevents adhesion between the light emitting end and the light incident end” means that the light emitting end and the light incident end that are physically in contact with each other at normal temperature are in the contact portion. It means a protective medium that prevents each constituent material from causing a chemical reaction and being bonded by fusion or the like, and the light emitting end and the light incident end are brought into contact with each other with a load of 500 g, or separated from each other, or Adhered so that the deposits generated on both end surfaces of the contact portion or the surface irregularities due to the deposits are λ / 2 or less (λ is the oscillation wavelength of the incident light) when moved relatively from the contact portion. Is defined as deterring.

  In addition, “the light incident end surface of the light transmissive optical member is larger than the light emitting end surfaces of the plurality of optical fibers” means that the light incident end surfaces of the light transmissive optical member are all of the plurality of optical fibers. This means that the size is at least in contact with the light emitting end face.

  The optical fiber end face protection structure of the present invention can be detachable even when the incident light is light having a wavelength of 190 nm to 530 nm.

The protective medium preferably has a light-transmitting property with respect to the oscillation wavelength of the incident light, and the optical path length in the optical waveguide direction is preferably an integral multiple of λ / 2.
In this specification, “the protective medium has translucency with respect to the oscillation wavelength of the incident light” is defined as having a transmittance of 90% or more with respect to the oscillation wavelength of the incident light.

  The protective medium is a film body composed of a single layer film or a multilayer film in which a plurality of films are laminated, and the surface of the light emitting end of the plurality of optical fibers and / or the light incident end of the translucent optical member. Are formed.

The protective medium preferably includes a fluoride, and includes at least one fluoride selected from the group consisting of YF ₃ , LiF, MgF ₂ , NaF, LaF ₃ , BaF ₂ , CaF _2, and AlF _3. It is more preferable.

  In the optical fiber end face protection structure of the present invention, the plurality of optical fibers emits the light from the optical fibers so that the plurality of optical fibers accumulate and emit the plurality of lights incident on the plurality of optical fibers. The present invention can be preferably applied to a fiber bundle that is arranged and bundled on the end side.

  The fiber bundle of the present invention has the optical fiber end face protection structure of the present invention.

As a preferred aspect of the fiber bundle of the present invention, the plurality of optical fibers are arranged on the emission end side of the optical fibers so that the plurality of incident lights individually incident on the plurality of optical fibers are integrated and emitted. Integrated functional fiber bundle part bundled together,
A first fiber bundle having a uniform functional fiber part that uniformizes and emits light emitted from the integrated functional fiber bundle part;
A fiber bundle comprising a second fiber bundle in which the first fiber bundle is arranged and bundled on the emission end side of the first fiber bundle so that a plurality of the first fiber bundles are integrated and emitted. The uniform functional fiber part is composed of an optical fiber having a core part larger than a light emitting region in a light emitting end face of the integrated functional fiber bundle part at least at a light incident end face of the uniform functional fiber part,
The light emitting end of the integrated functional fiber bundle part and the light incident end of the uniform functional fiber part are in contact with each other,
Examples thereof include a fiber bundle in which the integrated functional fiber bundle part and the uniform functional fiber part are detachable.

Further, as another preferred aspect of the fiber bundle of the present invention, it is individually incident on a plurality of optical fibers at a light incident end of at least one of the plurality of optical fibers constituting the integrated functional fiber bundle portion. The light output end of the second integrated functional fiber bundle unit in which the plurality of optical fibers are arranged and bundled on the output end side of the optical fiber so as to integrate and emit the plurality of incident lights thus generated is the light. Abutting via a protective medium that suppresses adhesion between the light emitting end and the light incident end;
The at least one optical fiber has a core portion larger than a light emitting region in a light emitting end surface of the second integrated function fiber bundle portion at a light incident end surface of the optical fiber,
Examples thereof include a fiber bundle in which the at least one optical fiber and the second integrated function fiber bundle part are detachable.

  The optical fiber end face protection structure of the present invention has a structure in which the light emitting ends of a plurality of optical fibers and the light incident ends of the translucent optical member are in contact with each other via a protective medium that suppresses adhesion. The translucent optical member that is the end face protection member is detachable. In such a configuration, the plurality of optical fiber light emitting end faces can be collectively protected and contacted via a protective medium that suppresses adhesion between the translucent optical member and the light emitting end faces of the plurality of optical fibers. Therefore, even when light with a short wavelength of 450 nm or less or light with high energy density, which is easily damaged by attaching and detaching when attaching and detaching, is used, or when UV cleaning is performed on the end face, The translucent optical member can be attached and detached without being damaged. Therefore, according to the present invention, it is possible to provide an optical fiber end face protection structure in which the light emitting end faces of a plurality of optical fibers can be collectively protected and the end face protection member can be attached and detached.

"Optical fiber end face protection structure, fiber bundle"
With reference to drawings, the optical fiber end surface protection structure and fiber bundle of one Embodiment of this invention are demonstrated. FIG. 1 is a sectional view in the optical waveguide direction of the optical fiber end face protection structure 1 of the present embodiment. In the present specification, in order to make the drawings easy to see, the scale of the constituent elements is appropriately changed from the actual one.

  As shown in FIG. 1, an optical fiber end face protection structure 1 is an end face protection structure of a fiber bundle (a plurality of optical fibers) 2, and includes a fiber bundle 2, a translucent optical member 3, and a sleeve (holding member). 4 and the like, and the light emitting end face of the fiber bundle 2 is protected by the translucent optical member 3.

  The light emitting end 21 side of the fiber bundle 2 is inserted into the ferrule 2a, and the light emitting end surface 21a is polished and processed. The end face shape of the light emitting end face 21a is not particularly limited as long as the connection loss is reduced, and may be processed into a hemispherical shape, a flat shape, or the like. A protective film (protective medium) 10 is formed on the light incident end face 31 a of the translucent optical member 3, and the light exit end 21 of the fiber bundle 2 and the light of the translucent optical member 3 are in the sleeve 4. The incident end 31 is in contact with the optical contact through the protective film 10. The contact pressure at the contact portion is preferably about 4.9N to 11.8N. Since the fiber bundle 2 and the translucent optical member 3 are in contact with each other by an optical contact, the fiber bundle 2 and the translucent optical member 3 can be attached to and detached from the optical fiber end face protection structure 1.

  The light L1 guided through the fiber bundle 2 is emitted from the light emitting end 21 of the fiber bundle 2 and is incident on the light transmissive optical member 3 from the light incident end 31 through the protective film 10. 32 (L2).

The material in particular of the fiber bundle 2 is not restrict | limited, What is necessary is just to select a suitable material according to the wavelength of the light to guide. For example, when guiding ultraviolet light, the optical fiber constituting the fiber bundle 2 is preferably a glass-based optical fiber mainly composed of SiO ₂ or quartz.

  The material of the translucent optical member 3 may be any material that has substantially the same refractive index as the core material of the fiber bundle 2, and a suitable material is selected according to the wavelength of the light to be guided in the same manner as the fiber bundle 2. can do.

The protective film 10 is a film body formed on the light incident end face 31 a and suppresses adhesion between the light emitting end 21 of the fiber bundle 2 and the light incident end 31 of the translucent optical member 3. The protective film 10 may be formed directly on the light incident end face 31a or may be formed through an assist film. When glass optical members such as SiO ₂ and quartz are brought into contact with each other by optical contact, the light to be guided is light with high energy density or ultraviolet light, for example, light having an oscillation wavelength of 190 nm to 530 nm, or a contact surface When the UV cleaning process is applied to the contact portion, the oxide on both contact surfaces causes some reaction in the contact portion, and the reaction portion is integrated and attached, and then the portion attached when separated from the contact portion is attached. It has been confirmed by the present applicant that the optical loss is increased due to breakage and becomes unusable as follows.

  FIG. 2 shows a contact surface of the optical fiber 100 when the optical fiber and the glass are UV-cleaned, and the cross section of the optical fiber is brought into contact with the glass with a weight of about 500 [g] and left for about 100 hours. 101 is a clad and 102 is a core. Reference numeral 103 denotes a portion where the optical fiber 100 and glass (not shown) are brought into contact with each other and bonded to each other so that quartz or oxide contained in the glass reacts with each other. Is an integrated part. When the reaction sites are integrated as described above, the reaction sites are greatly damaged when the optical fiber 100 and the glass are separated from each other, or the reaction sites are attached to the cross section of the optical fiber 100 or the glass. Note that the surface roughness of the fiber before contact is Ra = 2 [nm]. Such a phenomenon has occurred even when the optical fiber is brought into contact with the optical contact. In addition, the above phenomenon is likely to occur when the surface roughness is Ra <5 [nm] or less, and also when light having a short wavelength with higher energy density is guided.

Since the protective film 10 is for preventing the above phenomenon, the protective film 10 has translucency with respect to the oscillation wavelength λ of the incident light L1, and the fiber bundle 2 and the translucent optical member 3 are made of SiO ₂ or In the case of a glass material mainly composed of quartz or the like, it is preferable that adhesion between the light emitting end 21 and the light incident end 31 is suppressed when these are physically brought into contact with each other at room temperature. Accordingly, the protective film 10 is preferably one that does not easily react with SiO ₂ or quartz contained in the fiber bundle 2 and the light-transmitting optical member 3 and is inert to light having a wavelength of 190 nm to 530 nm, and contains fluoride. Things. As the fluoride, those not containing oxygen (O) are preferable, and at least one fluoride selected from the group consisting of YF ₃ , LiF, MgF ₂ , NaF, LaF _3, BaF ₂ , CaF ₂ and AlF ₃ is used. More preferred. These fluorides are inactive with respect to light having a wavelength of 190 nm to 410 nm, and their activity is low even with respect to wavelengths of 410 nm to 530 nm. In addition, since the energy density decreases as the wavelength increases, the protective film 10 suitable for light having a wavelength of 410 nm or more can be formed.

  The protective film 10 may be a single layer film or a multilayer film. In the case of a multilayer film, it is desirable that the uppermost layer of the protective film 10 contains the above material, and the lower layer film other than the uppermost film preferably contains an oxide not containing Si.

Furthermore, since it is preferable that the light loss due to the presence of the protective film 10 is smaller, it is preferable to use a material that absorbs less light with respect to the wavelength of light to be guided. FIG. 3 shows the relationship between the absorption coefficient of various fluoride films and oxide films and the damage threshold when a pulse laser with a wavelength of 248 nm is used ("High damage threshold fluoride UV mirrors made by Ion"). (Quoted from “Beam Sputtering”, J. Dijion, et., Al., SPIE Vol. 3244, pp406-418, 1998 ”). From this graph, fluoride films have a higher damage threshold for ultraviolet light, and therefore light From the standpoint of absorption, it can be seen that fluoride is preferable as the material of the protective film 10. Further, when the guided light is ultraviolet light, YF ₃ or LiF is damaged in the fluoride film as shown in the graph. A threshold is high and more preferable.

  By setting it as the protective film 10 of the above structures, the chemical reaction in the contact part of the fiber bundle 2 and the translucent optical member 3 can be prevented, and damage to a contact part can be suppressed. For example, the fiber bundle 2 and the translucent optical member 3 can be reused even if they are separated after being pressed with a load of 50 g weight or more and 1 kg weight or less (more preferably 500 g weight or less) with respect to the contact portion. That is, it can be made detachable.

  In the contact portion, the light incident end surface 31a is equal to or larger than the light emitting end surface 21a so that all the light emitted from the light emitting end 21 of the fiber bundle 2 is incident on the light incident end 31 of the translucent optical member 3. It has a size. FIG. 4 shows a case where the translucent optical member 3 has a rod shape, and the fiber bundle 2 is bundled by arranging a plurality of optical fibers in a line shape (one-dimensional shape) at the emission end (FIG. 4A). )) And concentric (two-dimensional) bundles (FIG. 4B) as an example, a cross section of the light emitting end face 21a and the light incident end face 31a is shown. In FIG. 4, the light emitting area on the light emitting end face 21a and the light incident area on the light incident end face 31a are indicated by hatching. The light emitting end face 21a only needs to have a larger area than the hatched portion of the light incident end face 31a. However, when the translucent optical member 3 has a rod shape, the light incident end face 31a has a circular shape. As shown in the figure, it has a size equal to or larger than the circumscribed circle of the light emitting end 21a including the entire light emitting region.

  It is preferable that the translucent optical member 3 can emit all the incident light L1 from the light emitting end 32. Since the spread of light increases as the thickness in the waveguide direction increases, the size of the light exit end face 32a is preferably determined in consideration of the numerical aperture and thickness of the fiber bundle 2.

  When the light exit end face 21 of the fiber bundle 2 is protected by the translucent optical member 3, dust and dirt hardly adhere to the exit end face 21a. Instead, the light exit end face 32a adheres to dirt and dirt. It becomes a surface. Since dust and dirt are less likely to adhere as the light power density is lower, the light power is higher when the thickness of the light-transmitting optical member 3 in the waveguide direction is larger and the light emitting end face 32a is larger. It can be dispersed to slow down the contamination rate. Therefore, it is preferable that the light emitting end face 32a is large.

  The shape of the translucent optical member 3 is not particularly limited as long as it has the light emitting end surface 32a as described above, but as the shape of the versatile and inexpensive optical member, the light incident end surface 31a and the light emitting end surface Examples thereof include rod-shaped optical members having the same 32a. In the case of the rod shape, if the light emitting end face 32a is to be enlarged, the light incident end face 31a also becomes large.

  As described in the background art, the size of the light incident end face of the end face protection member is limited when fused, but the optical fiber end face protection structure 1 of the present embodiment is a translucent light that is an end face protection member. The optical optical member 3 and the fiber bundle 2 are not fused, but are in contact with each other to be detachable. Therefore, there is no limitation on the size of the light incident end face 31a of the translucent optical member 3 that is an end face protecting member. For example, in FIG. 4, the diameter of the circumscribed circle of the light emitting area on the light emitting end face 21a of the fiber bundle 2 It is also possible to abut the translucent optical member 3 having a diameter twice or more. Therefore, an optical fiber end face protection structure that collectively protects a plurality of fibers such as the fiber bundle 2 can be achieved, but the light incident end face 31a is further enlarged to reduce the contamination rate of the light exit end face 32a. The translucent optical member 3 can be designed so that it can be sufficiently lowered.

  In the background art, when transmitting high-power light, the optical fiber is connected to the optical fiber itself by generating a so-called return light that reflects part of the guided light at the light exit end face and travels backward in the optical fiber. He also mentioned that it could have an adverse effect on existing optical devices. Therefore, it is preferable that the light emission end face 32a is subjected to a special treatment for preventing reflection. However, if the power of the light increases, the amount of returned light will exceed the range where the influence on the optical fiber etc. can be ignored even if special processing for antireflection is performed. It is preferable that the light can be emitted from the end face protection member to the outside without being incident. As described above, if it is possible to increase the aperture of the translucent optical member 3 that is an end face protection member, more reflected light is effectively removed from the end face protection member without being incident again on the optical fiber. Therefore, according to the present embodiment, the influence of the return light can be reduced.

  In this embodiment, the protective film 10 is formed on the light incident end face 31a of the translucent optical member 3, but may be formed on the light emitting end face 21a of the fiber bundle 2, or the light incident end face 31a. Further, the film may be formed on both the light emitting end face 21a.

  The protective film 10 is preferably not peeled off from the end face formed when the translucent optical member 3 and the fiber bundle 2 are attached and detached. Therefore, when the protective film 10 is formed on either the light emitting end face 21a or the light incident end face 31a, the adhesion between the end face on which the protective film 10 is formed and the protective film 10 is protected. It is preferable that the adhesiveness between the end surface on which the film 10 is not formed and the protective film 10 is higher. Moreover, when it forms into a film on both end surfaces, the one where the adhesiveness of the end surface in which the protective film 10 is formed and the protective film 10 is higher than the adhesiveness of the film | membrane formed into a film on both end surfaces is preferable . Furthermore, when the protective film 10 is a multilayer film, it is preferable that the films constituting the multilayer film have high adhesion as well.

  The optical loss due to the presence of the protective film 10 is influenced by the film thickness in addition to the material of the protective film 10 described above. Therefore, it is preferable that the protective film 10 has a thickness that does not affect the optical loss. Factors of light loss in the protective film 10 include loss due to reflection and loss due to absorption. Therefore, the thickness of the protective film 10 is preferably determined in consideration of the influence on the optical loss due to reflection and absorption.

In order to minimize the loss due to reflection, it is preferable that the protective film 10 has a thickness that does not affect the optical loss. When the protective film 10 is formed on either the light incident end face 31a or the light emitting end face 21a of the fiber bundle 2, the optical path length of the protective film 10 in the optical waveguide direction (d × N, where d is optical It is preferable that the film thickness in the wave direction, N is the refractive index of the protective film 10) and the wavelength λ of the light to be guided satisfy the following formula (1).
d × N = (λ / 2) × n (1)
(Where n is an integer greater than or equal to 1)

When the protective film 10 is formed on both the light incident end face 31a or the light emitting end face 21a of the fiber bundle 2, when the protective film 10 formed on both has the same refractive index, (1) In the equation, d may be the total film thickness of the protective film 10. However, when the film is formed on both, the protective film 10 formed on each end face is at least on the outermost surface so that the protective films formed on both end faces do not cause reaction or integration due to contact. It is preferable that a certain uppermost layer is made of a different material. In this case, the film thickness of the protective film 10 formed on the light emitting end 21a of the fiber bundle 2 is d _f and the refractive index is N _f, and the film is formed on the light incident end 31a of the translucent optical member 3. When the thickness of the protective film 10 formed is d _g and the refractive index is N _g , it is preferable that these satisfy the following formula (2).
(D _f × N _f ) + (d _g × N _g ) = (λ / 2) × n (2)
(Where n is an integer greater than or equal to 1)

  In order to reduce the loss due to absorption, the protective film 10 is preferably thin. Since the light energy absorption of the film increases as the film thickness increases, the protective film 10 is thermally deteriorated due to the absorbed energy, and is likely to cause discoloration, cracks, and the like. Therefore, n is preferably 1 in the above formulas (1) and (2). However, depending on the degree of the influence of absorption on the loss, the influence of absorption is greater than the influence of reflection. In that case, in the above formulas (1) and (2), the optical loss can be further reduced at a film thickness thinner than that when n = 1.

  In order to investigate a suitable film thickness of the protective film 10, the optical device 110 shown in FIG. 5 was manufactured, and the temporal change in the light output of the emitted light when the protective film 10 having a different film thickness was used was measured. As shown in the figure, the optical device 110 includes optical fibers 111a and 111b, ferrules 112a and 112b, sleeves 113, and the like, and the optical fibers 111a and 111b inserted into the ferrules in the sleeve 113 are membranes. Contact is made through a protective film 10 having a thickness d. The end portion of the ferrule on the contact surface is polished into a hemispherical shape, and the protective film 10 is formed on the end surface on the optical fiber 111a side.

  Using the optical device 110 with the protective film 10 having a film thickness d of λ / 2, λ / 4, and λ / 6, a laser beam having a wavelength of 405 nm and an output of 160 mW is output from the optical fiber 91b. The change with time of the light output of the incident light was measured. A vapor deposition method was used as a method for forming the protective film 10. FIG. 6 is a diagram showing the measurement results, and the vertical axis shows the ratio of the output value of the emitted light to the output value of the incident light. At this time, the laser light passes through an area of each film having a diameter of about 60 μm.

  As shown in FIG. 6, the smaller the film thickness d, the smaller the decrease in the light output of the emitted light (that is, the smaller the optical loss). Further, when each protective film 10 after the experiment was observed with a microscope, almost no change in the appearance of the film with d = λ / 6 was observed, but the films with d = λ / 4 and λ / 2 passed the laser beam. Discoloration of the area considered to be a part was confirmed. Further, the film of d = λ / 2 was confirmed to have cracks around the discolored portion. The discoloration observed in the films with d = λ / 2 and d = λ / 4 is considered to be because the film was melted by the heat of the laser beam (thermal degradation). From this result, it is considered that as the film thickness d is larger, the energy absorption of the laser beam by the film is larger, the film quality is changed by this absorption, and the light loss increases.

The 7, the thickness of the protective film 10, and MgF ₂ film of d = λ / 6 and lambda / 12, shows the results of measuring the change with time of optical loss values in the same manner as the measurement . The protective film 10 was formed by an ion assist method. As shown in FIG. 7, in the films of d = λ / 6 and d = λ / 12, the way of changing the light output is almost the same, and the decrease rate of the light output of the emitted light after 1000 hours is almost the same. Is less than 10%.

From these results, when the protective film 10 is an MgF ₂ film and the incident light is a laser beam having a wavelength of 405 nm and an output of 160 mW, the influence on the optical loss is more influenced by the absorption than the influence by the reflection. If the thickness d of the protective film 10 is λ / 6 or less, the reduction rate of the light output of the emitted light after 1000 hours can be suppressed to less than 10%, which is considered preferable.

The ratio of the influence of reflection and the influence of absorption on the optical loss varies depending on the output and wavelength of the laser light and the material of the protective film 10, and is preferably a film thickness satisfying the formula (1) or the formula (2). In some cases, the film thickness d is preferably λ / 6 or less. However, since light having a wavelength of 190 nm to 530 nm has a high energy density, it is considered that the thickness d of the protective film 10 is preferably λ / 6 or less, depending on the output. When the protective film 10 is formed on both the light incident end face and the light outgoing end face in the contact portion, the film thickness is the sum of the film thicknesses of the protective film 10 formed on both (d = D _f + d _g ).

  The method for forming the protective film 10 is not limited, but in order to reduce light loss at the interface between the protective film 10 and the end face where the protective film 10 is formed, the film forming surface can be cleaned before the film formation. The method is preferred. In addition, the higher the density of the film, the less the change in film quality due to the absorption of light energy of the protective film 10 when light having a high light energy density is guided, so that a denser film can be formed. A film forming method is preferred. Cleaning the deposition surface before film formation As a deposition method that can clean the deposition surface before film formation and can form a highly dense film, ion assist method, ion plating Method, sputtering method and the like.

  Cleaning the deposition surface before film formation As a deposition method that can clean the deposition surface before film formation and can form a highly dense film, ion assist method, ion plating Method, sputtering method and the like.

FIG. 8 shows how the optical loss value changes with time using the protective film 10 (MgF ₂ film) having a film thickness of λ / 6 formed by the vapor deposition method and the ion assist method. The measurement results are shown. As shown in FIG. 8, it can be seen that it is preferable to use the protective film 10 formed by the ion assist method, rather than the vapor deposition method, with less decrease in light output.

  In the fiber bundle 2, the number of optical fibers 20 to be bundled and the arrangement pattern in the bundle part are not particularly limited. Examples of the arrangement of the bundle portions include a one-dimensional shape (line shape), a two-dimensional shape (including concentric circle shapes), and the like, and may be arranged according to a required emission pattern. Examples of arrangement patterns are shown in FIGS.

  A preferred embodiment of the fiber bundle 2 is a fiber bundle 4 shown in FIG. The fiber bundle 4 will be described with reference to FIG. FIG. 10 is a schematic cross-sectional view of the fiber bundle 4 in the optical waveguide direction.

  The fiber bundle 4 is an integrated functional fiber in which a plurality of optical fibers 50 are arranged and bundled on the light emitting end 52 side so that a plurality of incident lights L1 individually incident on the plurality of optical fibers 50 are accumulated and emitted. A first fiber bundle portion 7 having a bundle portion 5, a uniform functional fiber portion 6 including an optical fiber 60 for uniformly emitting light emitted from the integrated functional fiber bundle portion 5, and a plurality of first fiber bundle portions 7. The second fiber bundle portion 8 in which the uniform functional fiber portions 7 of the plurality of first fiber bundle portions are arranged and bundled on the light emission end 82 side so that the emitted light from the fiber bundle portion 7 is integrated and emitted. It is equipped with.

  In FIG. 10, the light emitting end 52 of the integrated functional fiber bundle portion 5 and the light incident end 61 of the uniform functional fiber portion 6 are inserted into ferrules 60a and 70a (not shown in FIG. 10), respectively, and a sleeve 80 (holding). Member) is contacted by an optical contact through a protective film 10. Therefore, the integrated functional fiber bundle part 5 and the uniform functional fiber part 6 are detachable.

  Both end surfaces inserted into the ferrules 50a and 60a are polished, and the end surface shape is not particularly limited as long as the connection loss is reduced, and examples thereof include a hemispherical shape and a planar shape. When an SC ferrule is used as the ferrules 50a and 60a, an SC connector can be used as the sleeve 80.

  11 is an enlarged cross-sectional view of a contact portion between the light emitting end 52 of the integrated functional fiber bundle portion 5 of FIG. 10 and the light incident end 61 of the uniform functional fiber portion 6, and FIG. 12 is an integrated functional fiber bundle portion 5 of FIG. It is the schematic of the light emission end surface 52a of this, and the light-incidence end 61a of the uniform function fiber part 6. FIG. As shown in FIG. 12, the optical fiber 60 of the uniform function fiber portion 6 has a core at least equal to or larger than the light emitting area 52r of the light exit end surface 52a of the integrated function fiber bundle portion 5 at the light incident end face 61a. It has a portion 61r. By adopting such a configuration, the uniform function fiber unit 6 can receive all the emitted light from the integrated function fiber bundle unit 5 and make it uniform and emit it.

The material system of the plurality of optical fibers 50 is not particularly limited, and examples thereof include glass-based optical fibers mainly composed of SiO ₂ or quartz, and a suitable material can be selected depending on the wavelength of the incident light L1. The type of optical fiber is not particularly limited, but a multimode optical fiber is preferable when considering use for a light source or the like.

  Since the plurality of optical fibers 50 constitute the integrated functional fiber bundle unit 5, the fiber diameter is preferably smaller so that the fibers can be integrated with higher density. However, the thinner the optical fiber, the more difficult it becomes to handle, and the degree of freedom in design is limited, such as the length of the fiber being difficult to handle and the production yield. End up. Further, as described in the background art, a fiber bundle in which very small diameter optical fibers are integrated at a high density is very difficult to process as a cable. Therefore, it is preferable that the integrated structure can be formed by an optical fiber having a diameter as large as possible. The fiber bundle 5 has a two-stage integrated structure in which uniform function fiber parts 6 for uniforming and emitting the light emitted from the integrated function fiber bundle part 5 are further bundled and integrated. Therefore, when the required amount of light is determined, such a two-stage integrated structure requires fewer optical fibers to be integrated at a time than an ordinary single integrated structure. That is, it is possible to form the integrated functional fiber bundle portion 5 with an optical fiber having a larger diameter than that of a single integrated structure. For example, in the case of a single integrated structure, when optical fibers having an outer diameter of about 50 μm are integrated, the configuration shown in FIG. 10 can have an outer diameter of about 80 μm. If it has such a fiber diameter, the fiber length can be set to about 50 cm to 1 m, which is easy to handle.

  In addition, when the number of optical fibers to be integrated is large, for example, when it exceeds 20, for example, the handleability is not easy, and unevenness in the amount of the adhesive used when the fibers are bundled easily occurs. When polishing the light exit end face of the bundle, there is a possibility that the polishing state will be unstable. As described above, the fiber bundle 4 can reduce the number of optical fibers to be integrated in the integrated functional fiber bundle unit 5, so that it is possible to make it difficult to cause uneven adhesion. Furthermore, to meet the demand for higher integration density, the integration function fiber bundle part as described later has a multi-stage structure, so that the integration degree can be maintained while maintaining the number of integrations that are easy to handle. It can be increased.

  In the integrated functional fiber bundle unit 5, the arrangement pattern of the plurality of optical fibers 50 is not particularly limited, but is an arrangement in which the optical fiber 50 is bundled closely in a concentric shape (two-dimensional shape) as shown in FIGS. 13 (a) and 13 (b). This is preferable because it is easy to bundle meridian optical fibers. Since the final emission pattern is determined by the arrangement pattern of the uniform function fiber portions 6 at the light emission end 82 of the second fiber bundle portion 8, the fiber bundle 4 can be bundled in a concentric arrangement that is easy to integrate. It is.

  The uniform function fiber unit 6 is composed of one multimode optical fiber 60, and the material system thereof is not particularly limited, but the light emitted from the integrated function fiber bundle unit 5 in which a plurality of optical fibers 50 are bundled is made uniform. Therefore, it is preferable that the optical fiber is made of the same material system as the plurality of optical fibers 50.

  As described above, since the integrated functional fiber bundle unit 5 is an assembly of meridian fibers, the fiber length cannot be made too long due to the difficulty of handling when integrated at a high density. The uniform functional fiber unit 6 is configured to uniformly emit light emitted from the integrated functional fiber bundle unit 5 composed of a plurality of lights by light interference, interaction between modes, etc. that are generated while guiding the optical fiber 60 composed of a multimode fiber. Therefore, it is preferable that the length of the optical fiber 60 is long. Therefore, the entire length of the fiber bundle can be adjusted by the uniform function fiber portion 6. Considering the light loss during light guide, the length of the optical fiber 60 is preferably 10 cm or more and 5 m or less, and more preferably 1 m or more and 5 m or less.

  The emitted light from the uniform functional fiber portion 6 has high uniformity even if its intensity distribution is measured by the near field pattern. In FIG. 14, four silica-based multimode optical fibers having a core diameter of 60 μm and an outer diameter of 80 μm are used as the plurality of optical fibers 50 constituting the integrated functional fiber bundle section 5, and the core diameter is used as the optical fiber 60 of the uniform function fiber section 6. This is a near-field pattern of emitted light when light is incident on a first fiber bundle portion 7 manufactured using a silica-based multimode optical fiber having a diameter of 230 μm and an outer diameter of 250 μm. In FIG. 14, the vertical axis indicates the intensity ratio with respect to the maximum value of the output light at each position where the maximum value of the emitted light is 1.0. As shown in FIG. 14, the emitted light pattern from the first fiber bundle portion 7 has a substantially uniform intensity distribution in the core portion. Therefore, even when only the first fiber bundle portion 7 is configured, it is possible to provide a fiber bundle with high uniformity of emitted light.

  The light exit end of the fiber bundle 4 is the light exit end 82 of the second fiber bundle portion 8. Therefore, the output pattern of the output light L2 from the fiber bundle 4 can be changed by the arrangement of the optical fibers 60 of the uniform function fiber portion 6 at the light output end 82 (see FIGS. 9A to 9D). ).

For example, when used as a light source for irradiating the entire long square mirror, the optical fibers 60 may be arranged in a one-dimensional close arrangement pattern as shown in FIG. 9 (a) or (b). When trying to integrate the pattern shown in FIG. 9A or 9B with only a thin fiber, it is likely to be an emission pattern with many invalid areas due to the difficulty in handling, resulting in poor uniformity. It is easy to become a light source. As described above, the fiber bundle 4 of the present embodiment has the concentric circular array that is easy to be integrated in the integrated functional fiber bundle portion 5, and the optical fiber 60 of the uniform functional fiber portion 6 having a large aperture that is easy to handle. Since the emission pattern can be formed by bundling in a desired arrangement, it is possible to emit light that is easy to manufacture and has good uniformity.
Further, as shown in FIG. 9D, when a plurality of lights are emitted from the separated emission positions, light with high uniformity can be emitted at each emission point.

  The fiber bundle 4 is configured such that the integrated functional fiber bundle portion 5 and the uniform functional fiber portion 6 are in contact with each other by an optical contact. Therefore, the integrated functional fiber bundle portion 5 and the uniform functional fiber portion 6 can be easily attached and detached. In the case of a conventional single integrated structure, etc., if one of the multiple optical fibers that make up the fiber bundle fails or degrades in function, or if the specifications as the light source are changed, the fiber bundle must be replaced. Therefore, it is necessary to redo the alignment with the optical element or the like that makes the light emitted from the fiber bundle incident. Since the fiber bundle 4 of the present embodiment can be attached and removed by replacing only the integrated functional fiber bundle portion 5, maintenance can be performed without moving the uniform functional fiber portion 6 side that is aligned with the optical element or the like. can do.

  For example, as shown in FIG. 9 (d), when it is desired to set the emitted light intensity, the wavelength, etc. for each point, as in the case where two points are simultaneously illuminated and each is incident on another optical system, Since only the integrated function fiber bundle portion 5 of the first fiber bundle portion 7 connected to each point needs to be changed to the specification, the position adjustment of each point to the optical system is not performed each time. Furthermore, it is possible to freely change the characteristics of light emitted from each point.

  As shown in FIG. 15, the fiber bundle 4 includes a plurality of optical fibers at a light incident end 51 of at least one optical fiber 50 among the plurality of optical fibers 50 constituting the integrated functional fiber bundle portion 5 of the fiber bundle 4. A second integrated functional fiber bundle unit 9 in which a plurality of optical fibers 90 are arranged and bundled on the emission end 92 side of the optical fiber 90 so that the plurality of incident lights L1 individually incident on the 90 are integrated and emitted. The light emitting end 92 of the optical fiber can be abutted (FIG. 16), and the integrated functional fiber bundle portion can be multistaged. FIG. 15 shows an example in which the integrated functional fiber bundle part has a two-stage structure. At this time, at least one optical fiber 50 has a core portion 51r larger than the light emission region 92r in the light emission end surface 92a of the second integrated function fiber bundle portion 9 at the light incident end surface 51a of the optical fiber 50. (See FIG. 12).

  The second integrated fiber bundle unit 9 has the same configuration as that of the integrated function fiber bundle unit 5 of the fiber bundle 4, and the configuration of the abutting portion when multi-staged is the same as that of the fiber bundle 4. Therefore, it can be attached and detached in the same manner as the fiber bundle 4, and furthermore, since the integrated functional fiber bundle portion is multistaged, it is possible to integrate light at a higher density. Although FIG. 15 shows the case where the integrated functional fiber bundle part has a two-stage structure, it is possible to increase the number of integrated functional fiber bundle parts and increase the number of stages with the same configuration.

  Also in the fiber bundle 4, when the light to be guided is light having a short wavelength with a high light energy density, the phenomenon of damaging the end face at the time of attachment / detachment at the contact portion similarly occurs. Therefore, in that case, it is preferable to interpose the protective film 10 at the contact portion.

When the integrated structure is multi-staged like the fiber bundle 4, the influence of the return light is generated on each integrated part, so that there are many affected parts. Therefore, the optical fiber end face protection structure 1 can be suitably used for the fiber bundle 4.
The optical fiber end face protection structure 1 is configured as described above.

  The optical fiber end face protection structure 1 is such that a light emitting end 21 of a fiber bundle (a plurality of optical fibers) 2 and a light incident end 31 of a translucent optical member 3 are brought into contact with each other via a protective medium 10 that prevents adhesion. The translucent optical member 3 which is an end surface protection member is detachable. In such a configuration, the light emitting end face 21a of the fiber bundle 2 can be collectively protected, and the light emitting end face 21a is brought into contact with the light emitting end face 21a via the protective medium 10 that suppresses adhesion between the light transmitting end face 21a. Therefore, the end faces are damaged even when light with a short wavelength of 450 nm or less or light with high energy density, which is easily damaged by attaching and detaching when attaching and detaching, or when UV cleaning treatment is applied to the end faces. The translucent optical member 3 can be attached and detached without doing so. Therefore, according to the present invention, it is possible to provide the optical fiber end face protection structure 1 that can collectively protect the light emitting end face 21a of the fiber bundle 2 and that the end face protection member is removable.

(Design changes)
In the present embodiment, a fiber bundle has been described as an example of the plurality of optical fibers 2, but the present invention can also be applied to other than the fiber bundle, for example, a fiber array.
Moreover, although the case where the protective medium 10 is a film body was demonstrated, it is not limited to a film body.

Embodiments according to the present invention will be described.
Example 1
The optical fiber end face protection structure shown in FIG. 1 was produced as follows.
First, a fiber bundle having a two-stage integrated structure shown in FIG. 10 was produced. As the optical fiber of the integrated functional fiber bundle part, 12 silica-based multimode glass optical fibers having a fiber length of 1 m, a core diameter of 60 μm, and an outer diameter of 80 μm are prepared, and four optical fibers are bundled at one end to bundle them. Thus, three integrated function fiber bundle portions were produced. As shown in FIG. 9A, bundling was performed by bundling four optical fibers so as to be closely arranged two-dimensionally, and then fixing with an adhesive.

Next, three silica-based multimode optical fibers having a core diameter of 205 μm and an outer diameter of 250 μm were prepared as optical fibers in the uniform functional fiber portion, and similarly, one end of the three optical fibers was bundled into a bundle. Unlike the integrated function fiber bundle part, the arrangement in bundling was arranged in close contact with the line shape (one-dimensional shape) shown in FIG. 13, and an FC ferrule was attached to the emission end. A protective film made of MgF ₂ was formed on the light incident end face of each uniform function fiber portion.

  After inserting the SC ferrule into the light incident end and the light exit end of the integrated functional fiber bundle part and the light incident end of the uniform functional fiber part, the light exit end of the integrated functional fiber bundle part and the light incident end of the uniform functional fiber part are A fiber bundle with a total of 12 channels was obtained by abutting with an SC connector.

Next, a quartz glass rod having a diameter of 6.5 mm and a length of 10 mm is prepared, an antireflection film is provided on one end face, and a protective film made of MgF ₂ film is formed on the other end face to form an end face protection member. The optical fiber end face protection structure was produced by bringing the light emitting end face of the fiber bundle into contact with the face on which the protective film of the end face protection member was formed in the sleeve. FIG. 17 is an observation of the exit end face of the fiber bundle on the contact surface from the exit end side of the optical fiber end face protection structure in the obtained optical fiber end face protection structure.

  Laser light having a wavelength of 405 nm and an output of 100 mW was incident on the 12 light incident ends of the obtained fiber bundle having the optical fiber end face protection structure, and the change with time in the output light power was measured (total input power 1.2 W).

(Example 2)
A fiber bundle is similarly manufactured using an optical fiber having a larger core diameter than that of the first embodiment (core diameter 230 μm, outer diameter 250 μm) as the optical fiber of the uniform function fiber portion, and the optical fiber end face is protected by the same end face protection member A structure was made. The time-dependent change of the emitted light power was measured in the same manner as in Example 1.

(Example 3)
Using the same optical fiber end face protection structure as in Example 1, the total input power of incident light was set to 4.13 W, and the change with time of the output light power was measured in the same manner.

(Comparative Example 1)
In the same fiber bundle as in Example 1, the change with time of the emitted light power was measured in the same manner as in Example 1 for the fiber bundle without the optical fiber end face protection structure.

(Evaluation)
FIG. 18 shows the change with time of the emitted light power in Example 1 and Comparative Example 1. In FIG. 18, the vertical axis indicates the intensity ratio with respect to the maximum value of the output light at each position where the maximum value of the emitted light is 1.0. In Example 2, the uniform functional fiber part having a larger diameter than that of Example 1 was used as the fiber bundle, and the results were almost the same as those of Example 1, and thus the illustration was omitted. As shown in the figure, the optical fiber end face protection structure of Example 1 has almost no change in the output optical power after 300 hours, but Comparative Example 1 does not have the optical fiber end face protection structure. Then, the output is unstable immediately after that, and the output light power decreases with time. From these results, it was confirmed that the output end face of the fiber bundle was protected by the optical fiber end face protection structure, and the output light power drop due to end face contamination was effectively delayed. Further, since almost no decrease in output is observed in Example 1, it is considered that the deterioration of the fiber bundle due to the return light can be effectively suppressed by the optical fiber end face protection structure.

FIG. 19 shows the change with time of the emitted light power in the third embodiment. FIG. 19 differs from FIG. 18 in that the vertical axis indicates the output value of the emitted light. Also in FIG. 19, the drop of the emitted light power is hardly observed even after 600 hours. Even when the total input power exceeds 4.0 W, it has been confirmed that the optical fiber end face protection structure effectively delays the reduction of the emitted light power due to end face contamination.
From the above results, the usefulness of the optical fiber end face protection structure of the present invention was confirmed.

  The optical fiber end face protection structure of the present invention can be preferably used particularly as an end face protection structure for optical fibers and fiber bundles for ultraviolet light.

Sectional drawing which shows the structure of the optical fiber end surface protection structure of embodiment which concerns on this invention Sectional view of the abutment part of the optical fiber where the abutment part is joined The figure which shows the relationship between the absorption coefficient of the pulse laser beam of wavelength 248nm of an oxide film and a fluoride film, and a damage threshold value Light exit end face of fiber bundle and light incident end face of translucent optical member Schematic sectional view of the main part of the optical device used for evaluating the light output characteristics of the emitted light due to the difference in the protective film The figure which shows the time-dependent change of the optical output of the emitted light when the film thickness of a protective film is set to (lambda) / 2, (lambda) / 4, and (lambda) / 6. The figure which shows the time-dependent change of the optical output of the emitted light when the film thickness of a protective film is set to (lambda) / 6 and (lambda) / 12. The figure which shows the time-dependent change of the optical output of the emitted light when the film-forming method of a protective film is made into a vapor deposition method and an ion assist method (A)-(d) is a figure which shows the arrangement | sequence of the uniform function fiber part in the light-projection end surface of a fiber bundle Sectional drawing which shows the structure of the fiber bundle of the suitable aspect in the optical fiber end surface protection structure of embodiment which concerns on this invention FIG. 10 is an enlarged cross-sectional view of the contact portion between the light emitting end of the integrated functional fiber bundle portion and the light incident end of the uniform functional fiber portion shown in FIG. Schematic diagram of the light exit end face of the integrated function fiber bundle portion of the fiber bundle shown in FIG. 10 and the light entrance end face of the uniform function fiber portion. (A) And (b) is a figure which shows the arrangement | sequence in the light-projection end surface of an integrated function fiber bundle part. Intensity distribution of near-field pattern of light emitted from uniform functional fiber Sectional drawing which shows the structure at the time of making the integrated function fiber bundle part of the fiber bundle of FIG. 10 into a multistage structure The expanded sectional view in the contact part of the light emission end of the 2nd integrated function fiber bundle part of the fiber bundle shown in FIG. 15, and the light incident end of an integrated function fiber bundle part, The exit end face of the fiber bundle at the contact surface observed from the light exit end side of the optical fiber end face protecting structure of Example 1 The figure which shows the time-dependent change of the emitted light power in Example 1 and Comparative Example 1. The figure which shows the time-dependent change of the emitted light power in Example 3.

Explanation of symbols

1 Optical fiber end face protection structure 10 Protective film (protective member)
2 Fiber bundle (multiple optical fibers)
21 Light exit end of fiber bundle (plural optical fibers) 21a Light exit end surface of fiber bundle (plural optical fibers) 3 Translucent optical member 31 Light incident end of translucent optical member 31a Light of translucent optical member Incident end face 4 Fiber bundle 5 Integrated functional fiber bundle part 50, 60, 90 Optical fiber 51, 91 Light incident end 51r, 61r Core part
52 Light Output End (Light Output End of Integrated Function Fiber Bundle)
52a Light exit end face of integrated functional fiber bundle part 52r Light exit region of integrated function fiber bundle part 6 Uniform functional fiber part 61 Light incident end of uniform function fiber part 62 Light exit end of uniform function fiber part 61a Light of uniform function fiber part Incident end face 7 First fiber bundle portion 8 Second fiber bundle portion 82 Light exit end of second fiber bundle portion 82a Light exit end surface of second fiber bundle portion 9 Second integrated functional fiber bundle portion 92 Second Light exit end 92r of the second integrated function fiber bundle portion Light exit area L1 of the second integrated function fiber bundle portion

Claims (11)

A plurality of optical fibers that emit incident light from the light exit end;
A translucent optical member having substantially the same refractive index as the core material of the plurality of optical fibers, and allowing light emitted from the light exit ends of the plurality of optical fibers to enter and exit from a light incident end;
An end face of the optical fiber having a protective medium interposed between the light exit ends of the plurality of optical fibers and the light entrance end of the light transmissive optical member, and preventing adhesion between the light exit ends and the light entrance end. A protective structure,
The light incident end face of the translucent optical member has a size equal to or larger than the light emitting end face of the plurality of optical fibers.
The light is light having a wavelength of 190 nm to 530 nm;
The core material and the translucent optical member contain quartz or SiO ₂ ,
The optical path length of the protective medium in the optical waveguide direction is λ / 6 or less (where λ is the oscillation wavelength of the incident light),
The optical fiber end face protection structure, wherein the plurality of optical fibers and the translucent optical member are detachable via the protective medium.   The translucent optical member is capable of emitting all the light incident on the light incident end surface and a light incident end surface having a size capable of entering all the light emitted from the light emitting ends of the plurality of optical fibers. The optical fiber end face protection structure according to claim 1, further comprising a light emitting end face having a size.   Even if the protective medium is separated after the light emitting ends of the plurality of optical fibers contact the light incident ends of the translucent optical member with a load of 500 g, the light emitting ends and the light incident The optical fiber end face protection structure according to claim 1 or 2, wherein adhesion is suppressed so that the end can be reused. The optical fiber end face structure according to any one of claims 1 to 3, wherein a surface roughness Ra of the light incident end face and the light emitting end face is less than 5 nm.   The optical fiber end face protection structure according to any one of claims 1 to 4, wherein the protection medium has translucency with respect to an oscillation wavelength of the incident light.   The protective medium is a film body composed of a single layer film or a multilayer film in which a plurality of films are laminated, and is formed on the surface of the light emitting end of the plurality of optical fibers and / or the light incident end of the translucent optical member. The optical fiber end face protection structure according to claim 1, wherein the optical fiber end face protection structure is formed. The optical fiber end face protection structure according to any one of claims 1 to 6 , wherein the protection medium contains a fluoride. Wherein the protective _{medium, YF 3, LiF, MgF 2} , NaF, in claim 7, characterized in that contains at least one fluoride selected from the group consisting of LaF _3, BaF _2, CaF 2 and AlF ₃ The optical fiber end face protection structure described. A fiber bundle in which the plurality of optical fibers are arranged and bundled on the emission end side of the optical fibers so that the plurality of optical fibers integrate and emit the plurality of lights incident on the plurality of optical fibers. The optical fiber end face protection structure according to claim 1 , wherein the optical fiber end face protection structure is provided. A fiber bundle having the optical fiber end face protection structure according to claim 9 . An integrated functional fiber bundle part in which the plurality of optical fibers are arranged and bundled on the emission end side of the optical fibers so as to integrate and emit a plurality of incident lights individually incident on the plurality of optical fibers;
A first fiber bundle having a uniform functional fiber part that uniformizes and emits light emitted from the integrated functional fiber bundle part;
A fiber bundle comprising a second fiber bundle in which the first fiber bundle is arranged and bundled on the exit end side of the first fiber bundle so that the plurality of first fiber bundles are integrated and emitted. Because
The integrated functional fiber bundle part is the plurality of optical fibers;
The core part of the uniform function fiber part is the translucent optical member,
The light emitting end of the integrated functional fiber bundle part and the light incident end of the uniform functional fiber part are in contact with each other via the protective medium,
The fiber bundle according to claim 10 , wherein the integrated functional fiber bundle part and the uniform functional fiber part are detachable fiber bundles.