Optical fiber protection structure and optical combiner structure using the same

An optical fiber protection structure has a fiber accommodation portion having a fiber accommodation groove formed therein for accommodating at least a portion of optical fibers and first resins filled in the fiber accommodation groove. The first resins are to fix a portion of the optical fibers within the fiber accommodation groove. The optical fiber protection structure has a cover member disposed above the fiber accommodation portion so as to cover the fiber accommodation groove, second resins for allowing the first resins to expand toward the cover member to reduce a stress applied to the optical fibers, and a third resin for fixing the cover member onto the fiber accommodation portion. The second resins have a Young's modulus lower than those of the first resins.

TECHNICAL FIELD

The present invention relates to an optical fiber protection structure, and more particularly to an optical fiber protection structure that accommodates at least a portion of an optical fiber therein.

BACKGROUND ART

In many cases, optical fibers are connected to each other by removing coverings of the optical fibers and fusion-splicing bare fibers of the optical fibers to each other. Such portions of the optical fibers where the coverings have been removed are vulnerable to external forces and may be broken when any impact or vibration is exerted to the optical fibers. Therefore, portions of the optical fibers where the coverings have been removed, such as a fusion splice portion, are received within a fiber accommodation portion having a high tensile strength and fixed by a resin or the like.

Furthermore, in a case of a polymer cladding fiber, an air cladding confines light at portions where a covering has been removed. If a foreign material is attached to the portions where the covering has been removed, then light in the optical fiber may leak into the attached foreign material. In a case of high-power light, the optical fiber may be burnt out. Therefore, there has been known an optical fiber protection structure in which a cover member is disposed above the aforementioned fiber accommodation portion to prevent any foreign material from being attached to a portion where the covering has been removed (see, e.g., Patent Literature 1).

FIG. 1is a front view schematically showing such a conventional optical fiber protection structure800,FIG. 2is a cross-sectional view taken along line A-A ofFIG. 1, andFIG. 3is a cross-sectional view taken along line B-B ofFIG. 2. As shown inFIGS. 1 and 2, the conventional optical fiber protection structure800has a fiber accommodation portion820, in which a groove810is formed, and a cover member830disposed on the fiber accommodation portion820. As shown inFIGS. 2 and 3, portions of two optical fibers840and840where the coverings have been removed and a fusion splice portion860are received in the groove810of the optical fiber protection structure800. The optical fibers840and840are fixed to the fiber accommodation portion820at both ends of the groove810by resins870. The cover member830is fixed onto the fiber accommodation portion820. Each of the fiber accommodation portion820and the cover member830is formed of a material having a high tensile strength.

In such a conventional optical fiber protection structure800, the rigid cover member830is placed on the resins870for fixing the optical fibers840. Therefore, if the resins870expand under a high-temperature environment or a high-humidity environment, then the expansion of the resins870is inhibited by the cover member830placed on the resins870. As a result, as indicated by arrows inFIG. 3, stresses are applied to the optical fibers840so that the optical fibers840are compressed. Thus, light propagating through the optical fibers840tends to be coupled to a higher mode so as to leak out of the optical fibers840, so that the optical loss increases. For example, when high-power light from a fiber laser propagates through the optical fibers840, such optical loss may increase the temperature of the optical fibers840and the optical fiber protection structure800.

PRIOR ART LITERATURE

Patent Literature

Patent Literature 1: JP 4776420 B

SUMMARY OF THE INVENTION

Problem(s) to be Solved by the Invention

The Present Invention has been Made in View of the Above Drawbacks. It is, therefore, a first object of the present invention, to provide an optical fiber protection structure capable of suppressing an increase of optical loss of an optical fiber under a high-temperature environment or a high-humidity environment.

Furthermore, a second object of the present invention is to provide an optical combiner structure that is unlikely to cause optical loss even under a high-temperature environment or a high-humidity environment.

Means for Solving Problem(s)

According to a first aspect of the present invention, there is provided an optical fiber protection structure capable of suppressing an increase of optical loss of an optical fiber under a high-temperature environment or a high-humidity environment. This optical fiber protection structure has a fiber accommodation portion having a fiber accommodation groove formed therein for accommodating at least a portion of at least one optical fiber and a first resin filled in the fiber accommodation groove. The first resin is to fix the at least a portion of the at least one optical fiber within the fiber accommodation groove. The optical fiber protection structure has a cover member disposed above the fiber accommodation portion so as to cover at least a portion of the fiber accommodation groove, a fixation portion for fixing the cover member above the fiber accommodation portion, and a first stress reduction portion for allowing the first resin to expand toward the cover member to reduce a stress applied to the at least one optical fiber.

With this configuration, even if the first resin for fixing at least a portion of the optical fiber within the fiber accommodation groove expands under a high-temperature environment or a high-humidity environment, the first stress reduction portion allows the first resin to expand toward the cover member. Thus, a stress applied to the optical fiber by the first resin is reduced. Therefore, an increase of optical loss of the optical fiber due to a stress applied to the optical fiber can effectively be suppressed.

The first stress reduction portion may be formed by a second resin formed between the first resin and the cover member which has a Young's modulus lower than that of the first resin. Alternatively, the first stress reduction portion may be formed by a gap defined between the first resin and the cover member.

The fixation portion may be formed by a third resin formed between an upper surface of the fiber accommodation portion and the cover member. In this case, the third resin may preferably have a Young's modulus higher than that of the second resin. When the cover member is fixed onto the fiber accommodation portion by the third resin having a Young's modulus higher than the second resin, a stress applied to the optical fiber can be reduced by the second resin having a lower Young's modulus (more likely to deform) while the cover member can firmly be fixed onto the fiber accommodation portion by the third resin having a higher Young's modulus (less likely to deform).

Furthermore, the first stress reduction portion and the fixation portion may be formed by a second resin formed between the first resin and the cover member and between an upper surface of the fiber accommodation portion and the cover member. The second resin may have a Young's modulus lower than that of the first resin. With this configuration, the stress reduction portion and the fixation portion can be implemented by the same resin. Therefore, the manufacturing process can be simplified, and the manufacturing cost can also be reduced.

The optical fiber protection structure may also have a fourth resin provided within the fiber accommodation groove so as to cover at least a portion of the at least one optical fiber within the fiber accommodation groove and a second stress reduction portion for allowing the fourth resin to expand toward the cover member to reduce a stress applied to the at least one optical fiber. In this case, the fourth resin may be formed of a material having a refractive index lower than that of a cladding of the optical fiber. With this configuration, light propagating through the bare fiber exposure portion is prevented from leaking out of the bare fiber exposure portion. Alternatively, the fourth resin may be formed of a material having a refractive index higher than that of a cladding of the optical fiber. In this case, unnecessary light propagating through the cladding of the optical fiber can be removed while the influence of heat generated by such unnecessary light on the optical fiber can be reduced.

The second stress reduction portion may be formed by a fifth resin formed between the fourth resin and the cover member. The fifth resin may have a Young's modulus lower than that of the fourth resin. Alternatively, the second stress reduction portion may be formed by a gap defined between the fourth resin and the cover member. With this configuration, since the fourth resin is allowed to expand toward the cover member, a stress applied to the optical fiber is reduced.

According to a second aspect of the present invention, there is provided an optical combiner structure that is unlikely to cause optical loss even under a high-temperature environment or a high-humidity environment. This optical combiner structure includes the optical fiber protection structure as described above and an optical combiner including a first optical fiber, a second optical fiber, and a fusion splice portion in which the first optical fiber and the second optical fiber are connected to each other by fusion splicing. At least a portion of the first optical fiber, at least a portion of the second optical fiber, and the fusion splice portion are accommodated within the fiber accommodation groove of the fiber accommodation portion in the optical fiber protection structure.

Advantageous Effects of the Invention

According to the present invention, even if a first resin for fixing at least a portion of an optical fiber within a fiber accommodation groove expands under a high-temperature environment or a high-humidity environment, a first stress reduction portion allows the first resin to expand toward a cover member. Thus, a stress applied to the optical fiber by the first resin is reduced. Therefore, an increase of optical loss of the optical fiber due to a stress applied to the optical fiber can effectively be suppressed.

MODE(S) FOR CARRYING OUT THE INVENTION

Embodiments of an optical fiber protection structure and an optical combiner structure using such an optical fiber protection structure according to the present invention will be described in detail below with reference toFIGS. 4 to 19. InFIGS. 4 to 19, the same or corresponding components are denoted by the same or corresponding reference numerals and will not be described below repetitively. Furthermore, inFIGS. 4 to 19, the scales or dimensions of components may be exaggerated, or some components may be omitted.

FIG. 4is a front view showing an optical combiner structure1according to a first embodiment of the present invention, andFIG. 5is a cross-sectional view taken along line C-C ofFIG. 4. As shown inFIGS. 4 and 5, the optical combiner structure1includes an optical combiner10having optical fibers11and12connected to each other by fusion splicing and an optical fiber protection structure20that protects a fusion splice portion19between the optical fibers11and12. The optical combiner10has a first optical fiber11, a second optical fiber12, and a fusion splice portion19at which the first optical fiber11and the second optical fiber12are connected to each other by fusion splicing. The optical fiber protection structure20serves to protect the optical fibers11and12and the fusion splice portion19from external forces, impact, and vibration.

FIG. 6is a cross-sectional view taken along line D-D ofFIG. 5,FIG. 7is a cross-sectional view taken along line E-E ofFIG. 5, andFIG. 8is a cross-sectional view taken along line F-F ofFIG. 5. The optical fiber protection structure20has a fiber accommodation portion22having an upper surface22A in which a fiber accommodation groove21is formed along the X-direction and a cover member24disposed on the fiber accommodation portion22. The fiber accommodation portion22has a shape of a generally rectangular parallelepiped with a longitudinal direction along the X-direction. The cover member24is configured to have substantially the same dimension as the fiber accommodation portion22in the plan view.

As shown inFIGS. 5 and 8, a covering13of the first optical fiber11is removed over a predetermined distance from an end of the first optical fiber11. Thus, a bare fiber exposure portion17in which a bare fiber15is exposed is formed. Furthermore, a covering14of the second optical fiber12is removed over a predetermined distance from an end of the second optical fiber12. Thus, a bare fiber exposure portion18in which a bare fiber16is exposed is formed. The bare fiber exposure portion17of the first optical fiber11and the bare fiber exposure portion18of the second optical fiber12are connected to each other at the fusion splice portion19by fusion splicing.

The bare fiber exposure portion17of the first optical fiber11and the bare fiber exposure portion18of the second optical fiber12are disposed within the fiber accommodation groove21of the fiber accommodation portion22in a state in which the bare fiber exposure portion17and the bare fiber exposure portion18are connected to each other at the fusion splice portion19by fusion splicing. Since the fiber accommodation groove21of the fiber accommodation portion22is covered with the cover member24, the fusion splice portion19and the bare fiber exposure portions17and18are surrounded by the fiber accommodation portion22and the cover member24and are thus protected from external forces, impact, and vibration. For example, the fiber accommodation portion22and the cover member24may be formed of a glass material such as Neoceram (trademark) or quartz.

In the present embodiment, the first optical fiber11is formed by a single fiber having a core11A (seeFIG. 6), and the second optical fiber12is formed by a bundle fiber into which a plurality of optical fibers (seven optical fibers in the illustrated example) each having a core12A are bundled (seeFIG. 7). Thus, the optical combiner10of the present embodiment is formed as a 7×1 optical combiner. As a matter of course, the number of the core11A of the first optical fiber11and the number of the cores12A of the second optical fiber12may be changed in an appropriate manner.

As shown inFIGS. 5 and 6, the first optical fiber11is fixed within the fiber accommodation groove21by a first resin40A, which is filled into a first end of the fiber accommodation groove21along the X-direction. As shown inFIG. 6, this first resin40A surrounds the whole circumference of the covering13of the first optical fiber11. Similarly, as shown inFIGS. 5 and 7, the second optical fiber12is fixed within the fiber accommodation groove21by a first resin40B, which is filled into a second end of the fiber accommodation groove21along the X-direction. As shown inFIG. 7, this first resin40B surrounds the whole circumference of the covering14of the second optical fiber12.

As shown inFIGS. 5 and 6, a second resin42A is formed between the first resin40A and the cover member24. This second resin42A connects the first resin40A and the cover member24to each other. Similarly, as shown inFIGS. 5 and 7, a second resin42B is formed between the first resin40B and the cover member24. This second resin42B connects the first resin40B and the cover member24to each other. The second resins42A and42B are formed of a material having a Young's modulus lower than those of the first resins40A and40B.

As shown inFIGS. 5 to 7, a third resin44is formed between the fiber accommodation portion22and the cover member24along edges of the fiber accommodation portion22except for the area where the second resins42A and42B are formed. The fiber accommodation portion22and the cover member24are fixed to each other primarily by the third resin44. Therefore, in the present embodiment, the third resin44serves as a fixation portion for fixing the cover member24onto the fiber accommodation portion22. For example, a room temperature vulcanizing (RTV) resin and the like may be used for the third resin44.

In this manner, the second resins42A and42B and the third resin44are formed all around the edges of the upper surface22A of the fiber accommodation portion22. The cover member24is placed on those resins. Therefore, the cover member24can be fixed in a state in which the cover member24is brought into intimate contact with the fiber accommodation portion22via the resins. Thus, a hermetically sealed space S, which is substantially hermetically sealed from an external space, can be formed within the fiber accommodation portion22. In the present embodiment, air within the hermetically sealed space S forms an air cladding to the bare fiber exposure portions17and18of the optical fibers11and12.

As described above, the bare fiber exposure portions17and18and the fusion splice portion19of the optical fibers11and12are received within the fiber accommodation groove21of the fiber accommodation portion22and surrounded by the fiber accommodation portion22and the cover member24. Therefore, the bare fiber exposure portions17and18and the fusion splice portion19of the optical fibers11and12, which are particularly vulnerable to external forces, are protected from external forces, impact, and vibration. Furthermore, since the bare fiber exposure portions17and18of the optical fibers11and12are disposed in the hermetically sealed space S, any foreign material such as dust is prevented from being attached to the bare fiber exposure portions17and18. Accordingly, light in the optical fibers11and12is prevented from leaking into an attached foreign material to cause the burnout of the optical fibers.

When the optical combiner structure1as configured above is under a high-temperature environment or a high-humidity environment, the first resins40A and40B that fix the optical fibers11and12to the fiber accommodation groove21expand as shown inFIG. 9. In the present embodiment, the second resins42A and42B, which have a Young's modulus lower than the first resins40A and40B (i.e., more likely to deform), are formed between the first resins40A,40B and the cover member24. Therefore, even if the first resins40A and40B expand under a high-temperature environment or a high-humidity environment, the second resins42A and42B deform to allow the first resins40A and40B to expand toward the cover member24. Thus, stresses applied to the optical fibers11and12by the first resins40A and40B is reduced to suppress an increase of the optical loss of the optical fibers11and12. In this manner, the second resins42A and42B of the present embodiment serve as a stress reduction portion for allowing the first resins40A and40B to expand toward the cover member24to reduce stresses applied to the optical fibers11and12.

In this case, the third resin44, which serves as a fixation portion for fixing the cover member24onto the fiber accommodation portion22, may preferably have a Young's modulus that is higher than the Young's modulus of the second resins42A and42B. When the cover member24is fixed onto the fiber accommodation portion22by the third resin44having a Young's modulus higher than the Young's modulus of the second resins42A and42B, stresses applied to the optical fibers11and12can be reduced by the second resins42A and42B having a lower Young's modulus (more likely to deform) while the cover member24can firmly be fixed onto the fiber accommodation portion22by the third resin having a higher Young's modulus (less likely to deform).

In the present embodiment, the first resins40A,40B and the second resins42A,42B are formed on both ends of the fiber accommodation groove21. Nevertheless, the first resins40A,40B and the second resins42A,42B may be formed at positions deviated from both ends of the fiber accommodation groove21toward the center of the fiber accommodation groove21in the X-direction. The number of locations where the first resins40A,40B and the second resins42A,42B are formed is not limited two and may be one, or otherwise three or more.

FIGS. 10 and 11are cross-sectional views showing an optical combiner structure101according to a second embodiment of the present invention.FIG. 10corresponds to the cross-sectional view ofFIG. 5, andFIG. 11corresponds to the cross-sectional view ofFIG. 6. In the aforementioned first embodiment, the width of the second resins42A and42B as measured along the Y-direction is substantially the same as the width of the first resins40A and40B as measured along the Y-direction. In the second embodiment, however, the width of the second resins142A and142B as measured along the Y-direction is greater than the width of the first resins40A and40B as measured along the Y-direction. In the illustrated example, the second resins142A and142B are formed over the overall width of the fiber accommodation portion22along the Y-direction. With such a configuration, the area of the second resins142A and142B that allow expansion of the first resins40A and40B is increased as compared to the first embodiment. Therefore, stresses applied to the optical fibers11and12can more effectively be reduced.

FIG. 12is a diagram showing an optical combiner structure201according to a third embodiment of the present invention and corresponds to the cross-sectional view ofFIG. 6. In contrast to the second embodiment, the width of the second resins242A and242B as measured along the Y-direction is less than the width of the first resins40A and40B as measured along the Y-direction in the present embodiment. With this configuration, the area of the third resin244that fixes the fiber accommodation portion22and the cover member24to each other is increased as compared to the first embodiment. Therefore, the fiber accommodation portion22and the cover member24can more firmly be fixed to each other.

FIGS. 13 and 14are cross-sectional views showing an optical combiner structure301according to a fourth embodiment of the present invention.FIG. 13corresponds to the cross-sectional view ofFIG. 5, andFIG. 14corresponds to the cross-sectional view ofFIG. 6. As shown inFIGS. 13 and 14, in the present embodiment, a second resin342formed of a material having a Young's modulus lower than those of the first resins40A and40B is provided between the first resins40A,40B and the cover member24. The second resin342is formed not only between the first resins40A,40B and the cover member24, but also along the edges of the fiber accommodation portion22. Thus, the second resin342of the present embodiment serves not only as a stress reduction portion for allowing the first resins40A and40B to expand toward the cover member24to reduce stresses applied to the optical fibers11and12, but also as a fixation portion for fixing the cover member24onto the fiber accommodation portion22. According to the present embodiment, the stress reduction portion and the fixation portion can be implemented by the same resin. Therefore, the manufacturing process can be simplified, and the manufacturing cost can also be reduced.

FIG. 15is a cross-sectional view showing an optical combiner structure401according to a fifth embodiment of the present invention and corresponds to the cross-sectional view ofFIG. 6. As shown inFIG. 15, according to the present embodiment, a gap G is formed between the first resin40A and the cover member24. If the optical combiner structure401thus configured is under a high-temperature environment or a high-humidity environment, the first resin40A expands as shown inFIG. 16. Since the gap G is formed between the first resin40A and the cover member24, the first resin40A is allowed to expand toward the cover member24. Accordingly, stresses applied to the optical fiber11by the first resin40A is reduced to suppress an increase of the optical loss of the optical fiber11. In other words, the gap G formed between the first resin40A and the cover member24of the present embodiment serves as a stress reduction portion for allowing the first resin40A to expand toward the cover member24to reduce stresses applied to the optical fiber11.

FIG. 17is a cross-sectional view showing an optical combiner structure501according to a sixth embodiment of the present invention and corresponding to the cross-sectional view ofFIG. 8.FIG. 18is a cross-sectional view taken along line G-G ofFIG. 17. In the aforementioned first to fifth embodiments, an air cladding is formed by the air within the hermetically sealed space S in order to prevent light from leaking out of the bare fiber exposure portions17and18. In the present embodiment, however, the hermetically sealed space S is filled with a resin.

As shown inFIG. 17, first resins40A and40B are formed on both ends of the fiber accommodation groove21of the optical combiner structure501in the X-direction. As with the first embodiment, the second resins42A and42B are formed between the first resins40A,40B and the cover member24. As shown inFIGS. 17 and 18, in the fiber accommodation groove21, a fourth resin546is formed so as to surround the whole circumferences of the optical fibers11and12except portions where the first resins40A and40B are formed. The fourth resin546is formed of a material having a refractive index lower than those of the claddings of the bare fibers15and16. A gap T is formed between the fourth resin546and the cover member24.

In this manner, the optical fibers11and12within the optical combiner structure501are covered with the fourth resin546having a refractive index lower than those of the claddings of the bare fibers15and16. Therefore, light propagating through the bare fiber exposure portions17and18is prevented from leaking out of the bare fiber exposure portions17and18. Furthermore, the gap T is formed between the fourth resin546and the cover member24. Accordingly, even if the fourth resin546expands under a high-temperature environment or a high-humidity environment, the gap T allows the fourth resin546to expand toward the cover member24to thereby reduce stresses applied to the optical fibers11and12. In other words, the gap T serves as a stress reduction portion for allowing the fourth resin546to expand toward the cover member24to reduce stresses applied to the optical fibers11and12. Therefore, an increase of the optical loss of the optical fibers11and12is suppressed under a high-temperature environment or a high-humidity environment.

Instead of the gap T or in addition to the gap T, a fifth resin (not shown) having a Young's modulus lower than that of the fourth resin546may be formed as a stress reduction portion between the fourth resin546and the cover member24. When the Young's modulus of the second resins42A and42B is lower than the Young's modulus of the fourth resin, the second resins42A and42B may be used as the fifth resin.

Furthermore, the fourth resin546may be formed of a material having a refractive index lower than those of the coverings13and14in order to reduce the leakage of light from the coverings13and14. Additionally, the first resins40A,40B and the fourth resin546may be formed of the same material in order to suppress an increase of the manufacturing costs. Moreover, the fourth resin546may be provided so as to cover only a portion of the bare fiber exposure portions17and18.

Furthermore, in the aforementioned sixth embodiment, the fourth resin546is formed of a material having a refractive index lower than those of the claddings of the bare fibers15and16. In a case where optical fibers each having a core and at least one cladding are connected to each other, however, the fourth resin may be formed of a material having a refractive index higher than those of the claddings and disposed near the fusion splice portion19. With such a configuration, unnecessary light propagating through the claddings of the optical fibers11and12can be removed while the influence of heat generated by such unnecessary light on the optical fibers11and12can be reduced.

In the aforementioned embodiments, the fiber accommodation portion22and the cover member24have the same dimension in the plan view, and the cover member24is disposed on the fiber accommodation portion22so as to cover the overall length of the fiber accommodation groove21. However, the cover member24may not cover the overall length of the fiber accommodation groove21. Thus, the cover member24may be configured to cover at least a portion of the fiber accommodation groove21.

In the aforementioned embodiments, a resin is used as the fixation portion for fixing the cover member24onto the fiber accommodation portion22. However, various ways are possible to implement such a fixation portion. For example, a mechanical means such as a bolt may be used to fix the fiber accommodation portion22and the cover member24to each other. A magnetic force may be used to fix the fiber accommodation portion22and the cover member24to each other. Alternatively, the weight of the cover member24may be made greater than the weight of the fiber accommodation portion22so that a large frictional force is applied between the fiber accommodation portion22and the cover member24.

Moreover, the aforementioned embodiments have described examples of an optical combiner structure using an optical fiber protection structure according to the present invention. As a matter of course, however, an optical fiber protection structure according to the present invention is applicable to any optical element other than an optical combiner.

EXAMPLES

The inventors carried out the following experiments in order to examine the performance of an optical fiber protection structure according to the present invention. Specifically, an optical fiber protection structure as shown inFIGS. 10 and 11was used for an example of an optical fiber protection structure according to the present invention. The optical fiber structure was placed at temperatures from 25° C. to 70° C. The light transmittance of the optical fibers was measured. Furthermore, for a comparative example, the same experiment was carried out with an RTV resin having a Young's modulus higher than the Young's modulus of the first resin40A instead of the second resin342in the optical fiber protection structure shown inFIGS. 13 and 14, and the light transmittance of the optical fibers was measured.

FIG. 19is a graph showing a rate of change in light transmittance at varied temperatures while the light transmittance at 25° C. is defined as1. InFIG. 19, the light transmittance for the example of the optical fiber protection structure according to the present invention is indicated by a solid line whereas the light transmittance for the comparative example is indicated by a dashed line. As shown inFIG. 19, in the example of the optical fiber protection structure according to the present invention, the light transmittance hardly changed for the temperature variation from 25° C. to 70° C. With regard to the comparative example, it can be seen that the light transmittance significantly decreased at 70° C. This reveals that the light transmittance is less likely to decrease under a high-temperature environment in the optical fiber protection structure according to the present invention as compared to the optical fiber protection structure of the comparative example.

Although some preferred embodiments of the present invention have been described, the present invention is not limited to the aforementioned embodiments. It should be understood that various different forms may be applied to the present invention within the technical idea thereof. The terms “down,” “up,” “upper,” “lower,” “left,” “right,” “leftward,” and “rightward,” and other positional terms described herein are used in connection with the illustrated embodiments and may be varied depending on the relative positional relationship between components of the apparatus.

INDUSTRIAL APPLICABILITY

The present invention is suitably used for an optical combiner having an optical fiber protection structure that accommodates at least a portion of an optical fiber therein.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS