Patent Application
20250110284
The present invention relates to a capillary for, for example, holding an optical fiber and a method of manufacturing the same.
Various types of optical devices such as an optical multiplexer/demultiplexer, an optical isolator, and an optical circulator are used in an optical communication system using an optical fiber. When an optical fiber is connected to the optical device described above, a capillary is mounted to an end portion of the optical fiber so as to enhance operability.
For example, in Patent Literature 1, there is disclosed a capillary formed of a capillary tube. An end portion of the capillary is formed in an outwardly expanding tapered (flared) shape so as to allow easy insertion of the optical fiber into an inner hole of the capillary (see the paragraph [0002] of Patent Literature 1).
The tapered shape of the capillary is formed by alternately repeating a first step and a second step a plurality of times (see claim 1 and the paragraphs [0017] to [0019] of Patent Literature 1). In the first step, after a micro-diameter inner hole of a glass tube is filled with liquid (for example, water) that does not corrode a glass tube material and does not react with a corrosive liquid for the glass tube material, only one end surface of the glass tube is immersed in a corrosive liquid (etching solution containing hydrofluoric acid) for a given period of time. In the second step, the inner hole of the glass tube is cleaned after the immersion into the corrosive liquid.
The optical fiber is fixed to the capillary with an adhesive filling the inner hole of the capillary. In this case, the capillary has a problem in strength because a wall thickness of the end portion formed in a tapered shape is smaller than that of other portion. In addition, when the end portion has a microcrack, cracking originating from the microcrack may occur in the end portion as a result of expansion or shrinkage of the adhesive, which is caused by a temperature change in an environment where the optical device is used.
The present invention has been made in view of the circumstances described above, and has a technical object to prevent the occurrence of cracking in an end portion of a capillary.
According to the present invention, in order to solve the above-mentioned problems, there is provided a capillary for holding an optical fiber, the capillary comprising a capillary main body being made of glass and formed in an elongated shape, wherein the capillary main body comprises: an accommodating portion configured to accommodate a part of an optical fiber; a first end surface formed at one end portion of the capillary main body in a longitudinal direction (tube-length direction of a tube glass); and a second end surface formed at another end portion of the capillary main body in the longitudinal direction, wherein the accommodating portion comprises an opening portion, which is formed in the first end surface and is configured to allow insertion of the optical fiber, and wherein the capillary main body comprises: a compressive stress layer, which is formed on the opening portion and is observable by a two-dimensional birefringence measurement method; a tensile stress layer, which is formed at a position away from the compressive stress layer toward the second end surface and is observable by the two-dimensional birefringence measurement method; and a stress-neutral layer, which is formed between the compressive stress layer and the tensile stress layer and is observable by the two-dimensional birefringence measurement method.
With the configuration described above, a portion of the capillary main body, in which the compressive stress layer is formed, is reinforced by the presence of the compressive stress layer. Thus, the occurrence of chipping and cracking in the first end surface and the opening portion (hereinafter collectively referred to as “end portion”) of the capillary main body can be prevented.
Further, a portion of the capillary main body, in which the tensile stress layer is formed, is formed at a position away from the compressive stress layer with the stress-neutral layer being formed therebetween. As a result, a maximum value of a tensile stress can be made as small as possible. Thus, the tensile stress layer is less liable to be affected by expansion and shrinkage of an adhesive used for the capillary main body or expansion and shrinkage of the capillary main body. Further, even when a micro-scratch is formed in the capillary main body at the time of processing the capillary main body, the capillary main body is less liable to be affected by the scratch. Thus, the occurrence of cracking originating from the portion in which the tensile stress layer is formed can be prevented. In addition, with the formation of the stress-neutral layer, the portion of the capillary main body, in which the tensile stress layer is formed, is located at a position away from the first end surface by a length of the stress-neutral layer. For the capillary, the first end surface has frequent external contact. Thus, when the tensile stress layer is formed at a position away from the first end surface, the occurrence of chipping or cracking in the end portion of the capillary main body can be prevented.
In the following description of the present invention, a state of the stress layer observed by or a stress value measured by the two-dimensional birefringence measurement method is obtained at a position of a center axis of the capillary main body (tube axis of the capillary main body) when a side surface of the capillary main body is observed. Further, the stress-neutral layer refers to a layer having a compressive stress or a tensile stress of 5.0 MPa or less.
According to the present invention, in order to solve the above-mentioned problems, there is provided a capillary for holding an optical fiber, the capillary comprising a capillary main body being made of glass and formed in an elongated shape, wherein the capillary main body comprises: an accommodating portion configured to accommodate a part of an optical fiber; a first end surface formed at one end portion of the capillary main body in a longitudinal direction; and a second end surface formed at another end portion of the capillary main body in the longitudinal direction, wherein the accommodating portion comprises an opening portion, which is formed in the first end surface and is configured to allow insertion of the optical fiber, and wherein the capillary main body comprises: a compressive stress layer, which is formed on the opening portion and is observable by a two-dimensional birefringence measurement method; and a tensile stress layer, which is formed at a position away from the compressive stress layer toward the second end surface and is observable by the two-dimensional birefringence measurement method, and wherein a length of the compressive stress layer in the longitudinal direction of the capillary main body is longer than a length of the tensile stress layer in the longitudinal direction of the capillary main body.
With the configuration described above, a range in which the tensile stress layer is formed in the capillary main body is relatively smaller than a range in which the compressive stress is formed. Thus, when an external force acts on the portion in which the tensile stress layer is formed, the occurrence of chipping or cracking in the end portion of the capillary main body can be prevented. In addition, the portion of the capillary main body, in which the tensile stress layer is formed, can be set away from the first end surface by the length of the compressive stress layer. For the capillary, the first end surface has frequent external contact. Thus, when the position of the tensile stress layer is set away from the first end surface, the occurrence of chipping or cracking in the end portion of the capillary main body can be prevented.
According to the present invention, in order to solve the above-mentioned problems, there is provided a capillary for holding an optical fiber, the capillary comprising a capillary main body being made of glass and formed in an elongated shape, wherein the capillary main body comprises: an accommodating portion configured to accommodate a part of an optical fiber; a first end surface formed at one end portion of the capillary main body in a longitudinal direction; and a second end surface formed at another end portion of the capillary main body in the longitudinal direction, wherein the accommodating portion comprises an opening portion, which is formed in the first end surface and is configured to allow insertion of the optical fiber, and wherein the capillary main body comprises: a compressive stress layer, which is formed on the opening portion and is observable by a two-dimensional birefringence measurement method; and a tensile stress layer, which is formed at a position away from the compressive stress layer toward the second end surface and is observable by the two-dimensional birefringence measurement method, and wherein the tensile stress layer extends in the longitudinal direction from a position 0.1 mm or more away from the first end surface.
With the configuration described above, the portion of the capillary main body, in which the tensile stress layer is formed, is formed at a position away from the first end surface. For the capillary, the first end surface has frequent external contact. Thus, when the position of the tensile stress layer is set away from the first end surface, the occurrence of chipping or cracking in the end portion of the capillary main body can be prevented. The above-mentioned phrase “the tensile stress layer extends from a position 0.1 mm or more away from the first end surface” means that a distance between an end portion of the tensile stress layer, which is the closest to the first end surface, and the first end surface is 0.1 mm or more.
In the capillary of the present invention, it is preferred that the maximum value of the tensile stress in the tensile stress layer, which is measured by the two-dimensional birefringence measurement method, be 20 MPa or smaller. Thus, the tensile stress layer is less liable to be affected by the expansion and shrinkage of the adhesive used for the capillary main body or the expansion and shrinkage of the capillary main body. Further, even when a micro-scratch is formed in the capillary main body at the time of processing the capillary main body, the capillary main body is less liable to be affected by the scratch. Thus, the occurrence of cracking originating from the portion in which the tensile stress layer is formed can be prevented.
In the capillary of the present invention, it is preferred that the length of the stress-neutral layer in the longitudinal direction of the capillary main body be 0.01 mm or longer. Thus, the tensile stress layer is formed at a position 0.01 mm or more away from the compressive stress layer, and hence is less liable to be affected by the expansion and shrinkage of the adhesive used for the capillary main body or the expansion and shrinkage of the capillary main body. Further, even when a micro-scratch is formed in the capillary main body at the time of processing the capillary main body, the capillary main body is less liable to be affected by the scratch.
In the capillary of the present invention, the opening portion may have an inner wall surface formed in a tapered shape. With the configuration described above, the inner wall surface allows easy insertion of the optical fiber into the accommodating portion of the capillary main body.
In the capillary of the present invention, the opening portion may be filled with an adhesive. Thus, the optical fiber can be fixed to the capillary main body.
According to the present invention, in order to solve the above-mentioned problems, there is provided a method of manufacturing a capillary for holding an optical fiber, the capillary comprising a capillary main body being made of glass and formed in an elongated shape, the capillary main body comprising: an accommodating portion configured to accommodate a part of an optical fiber; a first end surface formed at one end portion of the capillary main body in a longitudinal direction; and a second end surface formed at another end portion of the capillary main body in the longitudinal direction, the accommodating portion comprising an opening portion, which is formed in the first end surface and is configured to allow insertion of the optical fiber, the method comprising: a preparation step of preparing the capillary main body; and a heating step of heating the first end surface and the opening portion of the capillary main body, wherein, in the heating step, the first end surface and the opening portion are irradiated with a laser beam having a beam diameter larger than the first end surface, and wherein, in the heating step, the first end surface and the opening portion are heated to form a compressive stress layer observable by a two-dimensional birefringence measurement method on the opening portion, a tensile stress layer observable by the two-dimensional birefringence measurement method at a position away from the compressive stress layer toward the second end surface, and a stress-neutral layer observable by the two-dimensional birefringence measurement method between the compressive stress layer and the tensile stress layer.
With the configuration described above, the portion of the capillary main body, in which the compressive stress layer is formed through the heating step, is reinforced by the presence of the compressive stress layer. As a result, the occurrence of chipping or cracking in the end portion of the capillary main body can be prevented.
Further, when the portion of the capillary main body, in which the tensile stress layer is formed through the heating step, is formed at a position away from the compressive stress layer with the stress-neutral layer being formed therebetween, the maximum value of the tensile stress can be made as small as possible. As a result, the tensile stress layer is less liable to be affected by the expansion and shrinkage of the adhesive used for the capillary main body or the expansion and shrinkage of the capillary main body. Further, even when a micro-scratch is formed in the capillary main body at the time of processing the capillary main body, the capillary main body is less liable to be affected by the scratch. Thus, the occurrence of cracking originating from the portion in which the tensile stress layer is formed can be prevented.
Further, the portion of the capillary main body, in which the tensile stress layer is formed, is located at a position away from the compressive stress layer with the stress-neutral layer being formed therebetween. The maximum value of the tensile stress can be made as small as possible. As a result, the tensile stress layer is less liable to be affected by the expansion and shrinkage of the adhesive used for the capillary main body or the expansion and shrinkage of the capillary main body. Further, even when a micro-scratch is formed in the capillary main body at the time of processing the capillary main body, the capillary main body is less liable to be affected by the scratch. Thus, the occurrence of cracking originating from the portion in which the tensile stress layer is formed can be prevented. In addition, when the stress-neutral layer is formed, the portion of the capillary main body, in which the tensile stress layer is formed, is located at a position away from the first end surface by the length of the stress-neutral layer. For the capillary, the first end surface has frequent external contact. Thus, when the position of the tensile stress layer is set away from the first end surface, the occurrence of chipping or cracking in the end portion of the capillary main body can be prevented.
According to the present invention, in order to solve the above-mentioned problems, there is provided a method of manufacturing a capillary for holding an optical fiber, the capillary comprising a capillary main body being made of glass and formed in an elongated shape, the capillary main body comprising: an accommodating portion configured to accommodate a part of an optical fiber; a first end surface formed at one end portion of the capillary main body in a longitudinal direction; and a second end surface formed at another end portion of the capillary main body in the longitudinal direction, the accommodating portion comprising an opening portion, which is formed in the first end surface and is configured to allow insertion of the optical fiber, the method comprising: a preparation step of preparing the capillary main body; and a heating step of heating the first end surface and the opening portion of the capillary main body, wherein, in the heating step, the first end surface and the opening portion are irradiated with a laser beam having a beam diameter larger than the first end surface, wherein, in the heating step, the first end surface and the opening portion are heated to form a compressive stress layer observable by a two-dimensional birefringence measurement method on the opening portion and a tensile stress layer observable by the two-dimensional birefringence measurement method at a position away from the compressive stress layer toward the second end surface, and wherein a length of the compressive stress layer in the longitudinal direction of the capillary main body is longer than a length of the tensile stress layer in the longitudinal direction of the capillary main body.
With the configuration described above, a range in which the tensile stress layer is formed in the capillary main body is relatively smaller than a range in which the compressive stress is formed. Thus, when an external force acts on the portion in which the tensile stress layer is formed, the occurrence of chipping or cracking in the end portion of the capillary main body can be prevented. In addition, the portion of the capillary main body, in which the tensile stress layer is formed, can be set away from the first end surface by the length of the compressive stress layer. For the capillary, the first end surface has frequent external contact. Thus, when the position of the tensile stress layer is set away from the first end surface, the occurrence of chipping or cracking in the end portion of the capillary main body can be prevented.
According to the present invention, in order to solve the above-mentioned problems, there is provided a method of manufacturing a capillary for holding an optical fiber, the capillary comprising a capillary main body being made of glass and formed in an elongated shape, the capillary main body comprising: an accommodating portion configured to accommodate a part of an optical fiber; a first end surface formed at one end portion of the capillary main body in a longitudinal direction; and a second end surface formed at another end portion of the capillary main body in the longitudinal direction, the accommodating portion comprising an opening portion, which is formed in the first end surface and is configured to allow insertion of the optical fiber, the method comprising: a preparation step of preparing the capillary main body; and a heating step of heating the first end surface and the opening portion of the capillary main body, wherein, in the heating step, the first end surface and the opening portion are irradiated with a laser beam having a beam diameter larger than the first end surface, and wherein, in the heating step, the first end surface and the opening portion are heated to form a compressive stress layer observable by a two-dimensional birefringence measurement method on the opening portion, a tensile stress layer observable by the two-dimensional birefringence measurement method at a position away from the compressive stress layer toward the second end surface, and wherein the tensile stress layer extends in the longitudinal direction from a position 0.1 mm or more away from the first end surface.
With the configuration described above, the portion of the capillary main body, in which the tensile stress layer is formed, is formed at a position away from the first end surface. For the capillary, the first end surface has frequent external contact. Thus, when the position of the tensile stress layer is set away from the first end surface, the occurrence of chipping or cracking in the end portion of the capillary main body can be prevented. The above-mentioned phrase “the tensile stress layer extends from a position 0.1 mm or more away from the first end surface” means that a distance between an end portion of the tensile stress layer, which is the closest to the first end surface, and the first end surface is 0.1 mm or more.
According to the present invention, the method of manufacturing a capillary may comprise a cooling step of cooling the first end surface and the opening portion at a cooling rate of 100° C./second or lower. Thus, the maximum value of the tensile stress in the tensile stress layer formed in the capillary main body can be reduced as much as possible.
In the method of manufacturing a capillary according to the present invention, the laser beam may be a CO2 laser beam.
According to the present invention, the occurrence of cracking in the end portion of the capillary can be prevented.
Embodiments of the present invention are described below with reference to the drawings.
In
The optical fibers 2a to 2c comprise a first optical fiber 2a, a second optical fiber 2b, and a third optical fiber 2c. The first optical fiber 2a and the second optical fiber 2b are held by the first capillary 3a. The third optical fiber 2c is held by the second capillary 3b. Each of the optical fibers 2a to 2c comprises a clad 7 and a coating portion 8 that coats the clad 7. At a distal end portion of each of the optical fibers 2a to 2c, the clad 7 is exposed from the coating portion 8.
As illustrated in
The capillary main body 9 is formed of a capillary tube having a cylindrical shape. However, a shape of the capillary main body 9 is not limited to that described in this embodiment. It is preferred that a length dimension L1 (see FIG. 2) of the capillary main body 9 be from 3 mm to 15 mm. It is preferred that an outer diameter of the capillary main body 9 be from 0.5 mm to 3 mm.
As illustrated in
The first accommodating portion 10 comprises an opening portion (in a tapered shape) 11 and a through hole 12. The clads 7 of the first optical fiber 2a and the second optical fiber 2b can be inserted into the opening portion 11. The clad 7 of the first optical fiber 2a and the clad 7 of the second optical fiber 2b can be accommodated in the through hole 12.
In this embodiment, the clad 7 of the first optical fiber 2a and the clad 7 of the second optical fiber 2b are inserted into one through hole 12 of the first accommodating portion 10. The through hole 12 can be formed in various shapes such as a circular or rectangular sectional shape. When an outer diameter of the clad 7 of the first optical fiber 2a and an outer diameter of the clad 7 of the second optical fiber 2b are different from each other, the through hole 12 may have concavely curved surfaces with different radii of curvature so as to hold outer surfaces of the clads 7. It is preferred that a hole diameter of the through hole 12 be from 0.05 mm to 1.0 mm.
A configuration of the through hole is not limited to that described above. For example, the first accommodating portion 10 may have a plurality of (may be three or more) through holes so that clads of a plurality of (may be three or more) optical fibers are individually inserted into the through holes, respectively.
The opening portion 11 serves as a guide portion configured to allow easy insertion of the clad 7 of the first optical fiber 2a and the clad 7 of the second optical fiber 2b into the through hole 12. The opening portion 11 is formed on the first end surface 9a side of the capillary main body 9. When the capillary main body 9 has a plurality of through holes 12, it is preferred that the opening portion 11 be formed so as to communicate with all the through holes 12.
The opening portion 11 has an inner wall surface 11a formed in a tapered shape. The inner wall surface 11a is a surface gradually radially expanding from the second end surface 9b side toward the first end surface 9a of the capillary main body 9.
It is preferred that a length dimension L2 (see FIG. 2) of the opening portion 11 in the longitudinal direction of the capillary main body 9 be from 0.5 mm to 7 mm. It is preferred that a maximum opening diameter of the opening portion 11 be from 0.5 mm to 1.5 mm. It is preferred that a minimum opening diameter of the opening portion 11 be from 0.3 mm to 1.3 mm.
An adhesive 13 fills the opening portion 11 so as to fix a part of the first optical fiber 2a and a part of the second optical fiber 2b, which are accommodated in the first accommodating portion 10. Specifically, a space defined by the inner wall surface 11a of the opening portion 11 functions as a filled portion to be filled with the adhesive 13. The adhesive 13 filling the opening portion 11 is present between the first optical fiber 2a and the second optical fiber 2b and the inner wall surface 11a to thereby fix each of the optical fibers 2a and 2b to the first capillary 3a. Although not shown, the adhesive 13 also fills the through hole 12 (between an inner surface of the through hole 12 and outer surfaces of the clads 7).
As the adhesive 13, for example, an epoxy-based adhesive is used. However, the adhesive 13 is not limited to the epoxy-based adhesive. For example, a silicone-based or acrylic adhesive or a photocurable adhesive (for example, a UV-curable adhesive) may be used. A thermal expansion coefficient of the adhesive 13 is set to fall within a range of from 10×10−6/° C. to 100×10−6/° C.
The first end surface 9a of the capillary main body 9 is a surface formed so as to be orthogonal to the longitudinal direction of the capillary main body 9. The second end surface 9b of the capillary main body 9 is a surface inclined with respect to a direction orthogonal to the longitudinal direction of the capillary main body 9. It is preferred that an inclination angle θ (see
Distal end portions of the clads 7 of the first optical fiber 2a and the second optical fiber 2b, which are inserted into the through hole 12, have inclined surfaces so as to be flush with the second end surface 9b.
As illustrated in
In
Observation of a direction of a stress and measurement of a value of the stress in each of the compressive stress layer CSL, the tensile stress layer TSL, and the stress-neutral layer NSL are executed by a two-dimensional birefringence measurement method. In
The measurement device MD comprises a stage S, a light source LS, a polarizing member P, and a measurement unit H. The capillary main body 9 being a target to be measured is placed on the stage S. The light source LS is provided below the stage S. The polarizing member P is provided between the light source LS and the stage S. The measurement unit H is provided above the stage S. Besides, the measurement device MD comprises an arithmetic device and a display device. The arithmetic device is configured to perform an arithmetic process on data measured by the measurement unit H. The display device is configured to display the result of measurement.
The stage S has an opening portion Sa. Light emitted from the light source LS is allowed to pass upward through the opening portion Sa. The capillary main body 9 is placed on the stage S so as to overlap the opening portion Sa of the stage S. The capillary main body 9 is placed on the stage S so that a side surface of the capillary main body 9 is brought into contact with the stage S, specifically, a center axis O of the capillary main body 9 becomes parallel to a placement surface of the stage S.
The measurement unit H is formed of, for example, a polarization imaging camera. The measurement unit H comprises, for example, an objective lens, a polarization array, and a CCD device. The polarization array is configured to pick up an image formed through the objective lens.
After being transmitted through the polarizing member P, the light emitted from the light source LS is radiated onto the capillary main body 9. After that, the light is transmitted through the capillary main body 9 and reaches the measurement unit H. In this case, after being transmitted through a lower part 9c of the capillary main body 9 and passing through the opening portion 11 being a hollow portion, the light is transmitted through an upper part 9d of the capillary main body 9.
The arithmetic device performs a predetermined arithmetic process on data about polarized light measured by the measurement unit H to thereby calculate a retardation of the polarized light. Further, the arithmetic device calculates a stress value of the capillary main body 9 based on the retardation. A relationship between the retardation and the stress is expressed by the following Expression (1).
δ=β×F×d (1)
where δ represents a retardation (nm), β represents an optical elastic constant (10−2/Pa), F represents a stress (105 Pa), and “d” represents a wall thickness (cm) of the capillary main body 9.
It is desirable that the measurement of a stress by the measurement device MD described above be performed only on the lower part 9c or the upper part 9d of the capillary main body 9. With the structure of the measurement device MD and the shape of the capillary main body 9 described above, however, it is difficult to perform such a measurement. Thus, the polarized light, which has been transmitted through the lower part 9c and the upper part 9d of the capillary main body 9 placed on the stage S, is measured from above the capillary main body 9 by the measurement unit H. Specifically, the measurement unit H is located above the capillary main body 9 and measures an area in which the lower part 9c and the upper part 9d overlap each other. Thus, in this embodiment, the retardation δ is calculated by using a sum of a wall thickness of the lower part 9c and a wall thickness of the upper part 9d, specifically, a value (2d) two times larger than the wall thickness “d” of the capillary main body 9, as the wall thickness “d” of the capillary main body in Expression (1) given above. In other words, the wall thickness “d” of the capillary main body 9 can be calculated from a difference between an outer diameter and an inner diameter of the capillary main body 9. In a strict sense, when the inner wall surface 11a of the opening portion 11 is formed in a tapered shape, the wall thickness “d” of the capillary main body 9 changes each time in accordance with a measured portion. However, it is complicated to set a value of the wall thickness “d” again in accordance with the measured portion. Thus, for convenience, in the present invention, the value of the wall thickness is fixed with a value of the outer diameter and a value of the inner diameter of the capillary main body 9 on the first end surface 9a to calculate the retardation δ.
The arithmetic processing device enables display of an image for showing a distribution state of a stress in the capillary main body 9 (hereinafter referred to as “stress state image”) on the display device. Lengths L3 to L5 of the stress layers CSL, TSL, and NSL in the longitudinal direction of the capillary main body 9 can be measured based on the stress state image displayed on the display device, respectively.
The compressive stress layer CSL is formed so as to include the first end surface 9a of the capillary main body 9 and a surface layer portion thereof. Further, the compressive stress layer CSL is formed in an edge portion (boundary portion between the inner wall surface 11a and the first end surface 9a) of the opening portion 11 and a part of the inner wall surface 11a of the opening portion 11 in the vicinity of the first end surface 9a. The compressive stress layer CSL may be located at such a position that its end portion (end portion on the first end surface 9a side) is away from the first end surface 9a. In this case, it is preferred that a distance between the first end surface 9a and the end portion of the compressive stress layer CSL be set to from 0 mm to 0.5 mm, more preferably from 0 mm to 0.1 mm.
The length (width) dimension L3 (see
The tensile stress layer TSL is formed in a region (inside the capillary main body 9) between the inner wall surface 11a of the opening portion 11 and an outer surface of the capillary main body 9, which is away from the compressive stress layer CSL toward the second end surface 9b.
The length (width) dimension L4 (see
The stress-neutral layer NSL is a layer between the compressive stress layer CSL and the tensile stress layer TSL, which has a compressive stress or a tensile stress of 5 MPa or less.
A length (width) dimension L5 (see
Before the optical fibers 2a to 2c are fixed, the second end surface 9b of the capillary main body 9 is formed as a flat surface being orthogonal to the longitudinal direction of the capillary main body 9 as indicated by a solid line in
The lenses 4a and 4b comprise a first lens 4a and a second lens 4b. The first lens 4a is arranged between the first capillary 3a and the optical filter 5. The second lens 4b is arranged between the second capillary 3b and the optical filter 5. Each of the lenses 4a and 4b is formed of, for example, a columnar lens (so-called C lens) with a uniform refractive index, which has a partially spherical lens surface at one end portion, or a graded-index columnar lens (so-called GRIN lens). However, the lenses are not limited to those described above. Various types of lenses including, for example, a uniform refractive index lens having two partially spherical lens surfaces with the same curvature center at both ends (so-called drum lens) may be used.
As illustrated in
The optical filter 5 is formed of, for example, a WDM filter. The optical filter 5 is not limited to the WDM filter and may be other optical elements. The optical filter 5 is arranged between the first lens 4a and the second lens 4b inside the accommodating member 6. The optical filter 5 is fixed to one end portion of the first lens 4a with an adhesive (not shown).
The accommodating member 6 is formed in a cylindrical shape. However, a shape of the accommodating member 6 is not limited to the cylindrical shape. The accommodating member 6 accommodates the first lens 4a, the second lens 4b, the optical filter 5, the first support member 15a, the second support member 15b, the first capillary 3a, and the second capillary 3b.
The optical device 1 having the above-mentioned configuration has two modes of use. A first mode of use is a demultiplexing mode in which, when, for example, multiple light beams having two wavelengths are emitted from the first optical fiber 2a, a light beam having one wavelength is reflected by one end surface of the optical filter 5 and is incident on the second optical fiber 2b and a light beam having another wavelength is transmitted through the optical filter 5 and is incident on the third optical fiber 2c. A second mode of use is a multiplexing mode in which, when single light beams having different wavelengths are emitted from the first optical fiber 2a and the third optical fiber 2c, respectively, those two kinds of single light beams are both incident on the second optical fiber 2b.
Now, a method of manufacturing the capillary main body 9 having the configuration described above is described. As illustrated in
The preparation step S1 is a step of preparing the capillary main body 9. As illustrated in
In the forming step S11, a glass tube (capillary tube) is formed by, for example, a redraw method. With the redraw method, a glass preform is heated so that a part thereof is stretched to thereby form a glass tube having a desired diameter. In the cutting step S12, the glass tube formed through the forming step S11 is cut to have a predetermined length. After that, a plurality of glass tubes obtained by cutting are bundled together, and the bundle of the glass tubes is cut shorter.
In the polishing step S13, each of the end surfaces of the glass tube in the longitudinal direction, which are formed in the cutting step S12, is polished with a polisher such as a grindstone. Thus, for example, a crack formed in an end surface of the glass tube in the cutting step S12 can be eliminated. When a crack in the end surface of the glass tube is small, the polishing step S13 can be omitted.
In the processing step S14, a plurality of glass tubes G are held with a holding member 16 such as a banding band as illustrated in
Through the process described above, the capillary main body 9 having the first end surface 9a with the opening portion 11 is prepared.
In the processing step S14, a method of forming the opening portion 11 (inner wall surface 11a) in one end portion of the glass tube G is not limited to the above-mentioned etching and may also be machining (for example, grinding with a drill or the like).
Next, in the heating step S2, the first end surface 9a and the opening portion 11 of the capillary main body 9 are irradiated with a laser beam L to thereby heat the first end surface 9a and the opening portion 11.
Specifically, as illustrated in
In the heating step S2, it is preferred that an output of the laser irradiation device 18 be set to 3 W to 50 W. It is preferred that irradiation time of the laser beam L be set to 1 second to 10 seconds. As illustrated in
The above-mentioned irradiation with the laser beam L softens the entire first end surface 9a to eliminate microcracks, which have remained in the first end surface 9a and the opening portion 11. Further, the irradiation with the laser beam L softens a peripheral edge portion of the first end surface 9a (boundary portion between the first end surface 9a and an outer peripheral surface), the edge portion of the opening portion 11, and a part of the inner wall surface 11a. Those softened portions are subjected to chamfering.
After completion of the spot irradiation with the laser beam L to the first end surface 9a of the capillary main body 9, the laser irradiation device 18 stops the irradiation with the laser beam L. After that, the laser irradiation device 18 and the support device 17 are moved relative to each other so that the next capillary main body 9 is arranged below the laser irradiation device 18 as indicated by two-dot-dash lines in FIG. 11. After that, the spot irradiation with the laser beam L is performed on the first end surface 9a of the next capillary main body 9 while the laser irradiation device 18 is in a stopped state. Thus, the laser irradiation device 18 repeatedly carries out the heating step S2 for each of the plurality of capillary main bodies 9 supported on the support device 17 while being in an immobile and stopped state.
This method enables the formation of the compressive stress layer CSL, the tensile stress layer TSL, and the stress-neutral layer NSL in the capillary main body 9 through the heating step S2 and the cooling step S3 described later.
It is preferred that the capillary maim body 9 be annealed in the cooling step S3 so as to form the compressive stress layer CSL, the tensile stress layer TSL, and the stress-neutral layer NSL in the capillary main body 9. A cooling rate for the annealing of the capillary main body 9 is preferably from 10° C./second to 100° C./second, more preferably from 20° C./second to 80° C./second, further preferably from 30° C./second to 70° C./second. When an upper limit of the cooling rate falls within the above-mentioned range, the stress-neutral layer NSL can be formed between the compressive stress layer CSL and the tensile stress layer TSL. Further, a maximum value of the tensile stress in the tensile stress layer TSL can be set to 20 MPa or smaller. Further, a length of the stress-neutral layer NSL can be set to 0.01 mm or larger. Further, when a lower limit of the cooling rate falls within the above-mentioned range, a reduction in production efficiency can be prevented. When a method of irradiating with the laser beam L is spot irradiation, the cooling rate can be controlled to fall within the above-mentioned range. Here, the cooling rate refers to a cooling rate within a temperature range from a temperature at which the entire surface of the first end surface 9a is softened through heating to a temperature at which the entire surface of the first end surface 9a reaches its strain point as a result of cooling. It is preferred that the cooling step S3 be carried out in a temperature-controlled space. The cooling step S3 can also be carried out by gradually reducing an output of the laser beam L.
With the above-mentioned capillary main body 9 and the method of manufacturing the capillary main body according to this embodiment, the compressive stress layer CSL is formed in the capillary main body 9 through the heating step S2 and the cooling step S3. As a result, the first end surface 9a and the opening portion 11 of the capillary main body 9 can be reinforced with the compressive stress layer CSL. As a result, occurrence of chipping or cracking in the end portion (the first end surface 9a and the opening portion 11) of the capillary main body 9 can be prevented.
In addition to the effects described above, the inventors of the present invention have found the following effects of the present invention as a result of intensive studies.
The adhesive 13 filling the opening portion 11 tends to expand and shrink due to a temperature change under an environment where the optical device 1 is used. In this case, the inner wall surface 11a of the opening portion 11 expands in such a way as to follow the expansion of the adhesive 13. As a result, cracking, which originates from a microcrack in the opening portion 11, may occur in the opening portion 11. In particular, when the value (maximum value) of the tensile stress in the tensile stress layer TSL is large, this phenomenon is noticeable.
In order to prevent the above-mentioned occurrence of cracking in the capillary main body 9, the tensile stress layer TSL is formed at a position away from the compressive stress layer CSL, specifically, the stress-neutral layer NSL is formed between the compressive stress layer CSL and the tensile stress layer TSL. As a result, the value (maximum value) of the tensile stress in the tensile stress layer TSL is successfully reduced as much as possible. Thus, even when the tensile stress layer TSL is formed in such a manner as to extend into the opening portion 11, the occurrence of cracking in the end portion of the capillary main body 9, which is caused by the expansion and shrinkage of the adhesive 13, can be prevented.
The inventors of the present invention conducted verification tests so as to confirm the effects of the present invention. Now, examples of the present invention are described. However, the present invention is not limited to the examples.
First, a capillary main body made of glass was manufactured through the steps of
Capillary main bodies of Examples 1 to 3 were obtained through the steps of
After that, sixteen optical fibers were inserted from the opening portion toward the through hole. Then, the opening portion was filled with an adhesive to thereby manufacture a capillary for holding optical fibers.
A temperature cycling test (twenty-four cycles of temperature changes within a range of from −40° C. to 85° C.) was performed on one thousand samples obtained in each of Examples 1 to 3 and Comparative Example. After that, the presence or absence of cracking in the end portion (the first end surface and the opening portion) was checked with use of an optical microscope.
The results of tests for Examples 1 to 3 and Comparative Example are shown in
As shown in Table 1 and illustrated in
Meanwhile, as shown in Table 1 and illustrated in
The present invention is not limited to the configurations of the above-mentioned embodiments. In addition, the action and effect of the present invention are not limited to those described above. The present invention may be modified in various forms within the range not departing from the spirit of the present invention.
In the embodiment described above, there has been described an example in which the capillary main bodies 9 were heated one by one in the heating step S2. However, the present invention is not limited to the configuration described above. In the heating step S2, a plurality of capillary main bodies 9 may be bundled so that their first end surfaces 9a are aligned with each other, and the first end surfaces 9a and the opening portions 11 of the plurality of capillary main bodies 9 may be heated with the laser beam L.
In the embodiment, the capillary main body 9 comprising the stress-neutral layer NSL has been described. However, the present invention is not limited to the embodiment described above. The end portion (boundary portion between the tensile stress layer and the compressive stress layer CSL) of the tensile stress layer TSL may be set away from the first end surface 9a by setting the length dimension L3 of the compressive stress layer CSL longer than the length dimension L4 of the tensile stress layer TSL instead of providing the stress-neutral layer NSL. In this embodiment, the length dimension L3 of the compressive stress layer CSL is preferably 1.1 times to 4 times larger than the length dimension L4 of the tensile stress layer TSL, more preferably 1.2 times to 3 times larger, further preferably 2 times to 3 times larger. Further, the length dimension L3 of the compressive stress layer CSL may be set larger than the length dimension L4 of the tensile stress layer TSL in addition to the formation of the stress-neutral layer NSL.
In the embodiment, the capillary main body 9 comprising the stress-neutral layer NSL and the length dimension L3 of the compressive stress layer CSL were set longer than the length dimension L4 of the tensile stress layer TSL have been described. However, the present invention is not limited to the embodiments described above. The end portion (end portion on the first end surface 9a side) of the tensile stress layer TSL, which corresponds to the compressive stress layer CSL, may be set 0.1 mm or more away from the first end surface 9a in the capillary main body 9 regardless of the length dimension L3 of the compressive stress layer CSL. In this embodiment, the end portion of the tensile stress layer TSL is preferably 0.1 mm or more away from the first end surface 9a, more preferably 0.5 mm or more away, further preferably 1 mm or more away. Meanwhile, a distance between the first end surface 9a and the end portion of the tensile stress layer TSL is preferably 3 mm or shorter, more preferably 2 mm or shorter.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-010925 | Jan 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/002485 | 1/26/2023 | WO |
