JP2005181899A - Optical fiber coupler and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem in which there is an optical fiber coupler which has improper adhesion specifications and is low in reliability. <P>SOLUTION: An optical fiber coupler is constituted by fusing and drawing core parts 1 and 2 of a plurality of optical fibers 10 and 20 having their coatings removed and joining them on a substrate 5 with adhesives 6 and 7. Tensile shearing adhesive strength of the adhesives is ≥5 MPa and their total coating volume is 0.36 to 5.6 mm<SP>3</SP>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fusion-stretching optical fiber coupler that branches or combines light of a single wavelength or a plurality of wavelengths, or combines or demultiplexes light of a plurality of wavelengths, and a method for manufacturing the same.

  In recent years, with the progress of optical communication systems and optical transmission technologies, fabrication methods are easy, and high-productivity fusion-stretching optical fiber couplers or fusion-stretching optical multiplexers / demultiplexers are used in various optical communication systems, It is used in measurement systems. Here, an optical fiber coupler is for branching or coupling light of a single wavelength or multiple wavelengths, and an optical multiplexer / demultiplexer is for multiplexing or demultiplexing light of multiple wavelengths. In the invention, both are collectively referred to as an optical fiber coupler.

  The fusion-stretching optical fiber coupler has a structure as shown in FIG. 1. First, the coating of the end portions of the optical fibers 10 and 20 is removed, and the core portions 1 and 2 are washed with alcohol or the like. Next, the core portions 1 and 2 are aligned, and the optical fibers 10 and 20 are stretched left and right in the longitudinal direction while heating the central portion with a burner such as oxygen-propane or hydrogen. The fusion extending part 3 is formed in the center part. The coupler body 4 composed of the optical fibers 10 and 20 and the fusion stretched part 3 thus manufactured is placed on a substrate 5 such as quartz glass, and is cured by energy rays such as ultraviolet rays and visible rays. Join through.

  The joint portion is generally at both end portions A of the substrate 5, but the core wire portions 1 and 2 and the substrate 5 are also joined at both end portions B of the fusion stretched portion 3. Although not shown, an optical fiber coupler is formed by covering the substrate 5 with a substrate such as quartz glass, which is the same material as the substrate 5, and further covering with a cylindrical body such as metal, ceramic, or glass. This completes the reinforcement structure.

  By the way, with the increase in the number of optical fiber couplers used in recent years, there are not a few problems such as characteristic fluctuations and disconnection failures. One of the causes is that the application state of the adhesive greatly affects.

  Therefore, in Patent Document 1, as shown in FIG. 3, the substrate 5 is provided with a concave groove 5a, the coupler main body 4 is accommodated in the concave groove 5a, and the coupler main body 4 and the substrate 5 are bonded and fixed. In fixing, first, the coupler main body 4 and the inner wall of the substrate 5 are temporarily fixed using an adhesive 7 having a high viscosity. The adhesive 7 is a core wire portion at both ends of the bonding portion where the coupler main body 4 and the substrate 5 are finally bonded by another adhesive 8 used in a later step, that is, at both ends of the substrate 5 as shown in FIG. It is applied and cured so as to cover the boundary between the coating parts 1 and 2 and the optical fibers 10 and 20.

  The adhesive 7 used here has a viscosity of about 1000 to 500,000 cps and has a short curing time so that it can sufficiently enter the gap between the inner walls of the substrate 5. Applied and joined.

  Further, the coupler main body 4 and the inner wall of the substrate 5 are already temporarily fixed with the high-viscosity adhesive 7 of about 1000 to 500,000 cps. For this reason, the adhesive 7 serves as a dam, and then the low-viscosity adhesive 8 Glue. As a result, it is proposed that the adhesive portion used for temporary fixing can be used to limit the bonding location to a predetermined position in advance, the range of selection of the adhesive 8 used for the main bonding can be expanded, and the environmental resistance characteristics of the optical fiber coupler can be improved. Has been. (See Patent Document 1).

Further, in Patent Document 2, as shown in FIG. 4, after bonding with a bonding agent 7 in a spot shape so as to cover the boundary portion between the fusion stretched portion 3 and the core wire portions 1 and 2 of the coupler main body 4, adhesion is performed. The adhesive 7 is covered, and another adhesive 8 having a low Young's modulus is provided in the concave groove 5a of the substrate 5, and only a part of the boundary portion is formed in a spot shape with the adhesive 7, and only a part thereof is formed. It is firmly fixed and can improve protection. And since the other part is filled with the other adhesive 8 to the whole board | substrate 5, the fluctuation | variation of a polarization characteristic can be reduced. The other adhesive 8 has a Young's modulus of less than 200 N / mm ² , and the target polarization characteristic can be obtained without breaking the coupler body 4 even when the optical fibers 10 and 20 are pulled. It is possible to provide an optical fiber coupler having the same. (See Patent Document 2).
JP-A-9-26519 JP 2003-167154 A

  However, in the proposal of Patent Document 1, it may be possible to secure a certain degree of reliability if an adhesive having an appropriate characteristic such as a linear expansion coefficient is selected. However, in a harsh environment or a severe reliability test of Telcodia. It is very difficult to pass.

  First, the coupler body 4 is bonded and fixed to the substrate 5 by the adhesives 7 and 8. However, when the adhesives 7 and 8 having different properties are joined, stress due to contraction and expansion difference occurs at the boundary surface, and the coupler The stress propagates also to the main body 4, and in the worst case, there is a problem that disconnection occurs and high reliability cannot be secured.

Second, although the bonding location can be limited to a predetermined position in advance by the adhesive 7 used for temporary fixing, since the other adhesive 8 is applied between the adhesives 7 to perform the main bonding, The coating volume tends to be large, and larger shrinkage and expansion are likely to occur, and stress is generated in the coupler body 4 and high reliability cannot be ensured. In this case, the coating volume is increased to about 9.6 to 11.2 mm ^3, and the viscosity is set to a low viscosity of about 1000 cps in order to widen the width of the adhesive 8 used for the main adhesion. There is a problem in that it leaks into the center of the coupler body 4 due to a capillary phenomenon, causing problems such as a change in branching ratio and an increase in excess loss.

  Further, Patent Document 2 is a proposal in which only the surface of tensile strength is taken into consideration, and such an adhesive application method passes a harsh environment and a severe reliability test of Telcodia as in the proposal of Patent Document 1. It is very difficult to do.

  First, since the coupler main body 4 is in contact with both the adhesive 7 and the other adhesive 8, as in the case of Patent Document 1, when the adhesives having basically different properties are joined together, the boundary surface As a result, stress due to the difference between contraction and expansion occurs, and the stress propagates to the coupler main body 4 as well, so that high reliability cannot be secured.

  Secondly, the adhesive volume is increased because the adhesives 7 and 8 are applied to all except the fusion stretched part 3 due to the idea that the tensile strength improves as the application amount of the adhesive 7 increases. In other words, the coupler body 4 is stressed by a larger shrinkage and expansion, and high reliability cannot be ensured.

An optical fiber coupler of the present invention is an optical fiber coupler obtained by fusing and stretching the core portions of a plurality of optical fibers from which the coating has been removed, and bonding them onto a substrate via an adhesive. The tensile shear bond strength is 5 MPa or more, and the total application volume is 0.36 to 5.6 mm ³ .

In the optical fiber coupler of the present invention, the adhesive is applied to both end portions of the substrate and both end portions of the fusion stretched portion, and the coating volume per one boundary portion of the optical fiber is 0.16. It is -1.6mm < ³ >, The application | coating volume per location of the both ends of a melt | fusion extension part is 0.02-1.2mm < ³ >, It is characterized by the above-mentioned.

  In the optical fiber coupler of the present invention, the adhesive at both ends of the substrate is applied so as to cover the entire peripheral surface of the optical fiber in the range of 2 to 4 mm from the end surface of the substrate in the longitudinal direction of the optical fiber. The boundary between the fiber coating portion and the core wire portion is located at the center of the adhesive.

  Furthermore, the optical fiber coupler of the present invention is such that the adhesive at both ends of the fusion stretched portion is within the range of ± 0.5 to ± 1.5 mm in the longitudinal direction from the base point of the fusion stretched portion. It is applied so as to cover the surface.

  Further, in the method for producing an optical fiber coupler of the present invention, an optical fiber is disposed on the substrate, and the adhesive is applied to a predetermined position in a state where the viscosity is 50000 mPa · s to 200000 mPa · s, and then the viscosity is 30000 mPa · s. In the above state, curing is started and bonding is performed.

According to the optical fiber coupler of the present invention, an optical fiber coupler in which the core portions of a plurality of optical fibers from which the coating has been removed is fused and stretched, and bonded onto a substrate via an adhesive, Since the tensile shear bond strength of the agent is 5 MPa or more and the total application volume is 0.36 to 5.6 mm ³ , stress due to environmental changes after bonding can be minimized, and high strength reinforcement Since it can be structured and residual stress after curing can be extremely reduced, there is almost no stress such as stress applied to the coupler body, preventing deterioration of the optical fiber coupler over time, and under severe conditions In addition, a highly reliable optical fiber coupler can be provided.

Further, according to the optical fiber coupler of the present invention, the adhesive is applied to both ends of the substrate and both ends of the fusion stretched portion, and the coating volume per one point of the boundary portion of the optical fiber is 0. .16 to 1.6 mm ³ , an appropriate holding force can be obtained between the optical fiber and the substrate, and the coating volume per one end of both ends of the fusion stretched part is 0.02 to 1. Since it is .2 mm ³ , both ends of the fusion-stretched portion that is weak in strength are reinforced with appropriate strength.

  Furthermore, according to the optical fiber coupler of the present invention, the adhesive at both ends of the substrate is applied so as to cover the entire peripheral surface of the optical fiber in the range of 2 to 4 mm from the end surface of the substrate in the longitudinal direction of the optical fiber, In addition, since the boundary between the coating portion of the optical fiber and the core wire portion is located at the central portion of the adhesive, a stronger holding force can be obtained between the optical fiber and the substrate.

  Furthermore, the optical fiber coupler of the present invention is such that the adhesive at both ends of the fusion stretched portion is within the range of ± 0.5 to ± 1.5 mm in the longitudinal direction from the base point of the fusion stretched portion. Since it was applied so as to cover the surface, both ends of the fusion-stretched portion that is weak in strength are further reinforced with appropriate strength, and the reinforcement is excellent in environmental resistance.

  Further, in the method for producing an optical fiber coupler of the present invention, an optical fiber is disposed on the substrate, and the adhesive is applied to a predetermined position in a state where the viscosity is 50000 mPa · s to 200000 mPa · s, and then the viscosity is 30000 mPa · s. Since curing is started in the above-described state and bonding can be performed by using one type of adhesive to adjust the bonding location and the coating volume, it is possible to obtain a highly reliable optical fiber coupler. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  With the development of optical communication systems and optical transmission technologies, various optical communication systems and optical measurement systems, such as fusion-stretching type optical fiber couplers or fusion-stretching type optical multiplexer / demultiplexers, which are easy to manufacture and have high productivity Etc. are used. An optical fiber coupler is for branching or coupling light of a single wavelength or multiple wavelengths, and an optical multiplexer / demultiplexer is for multiplexing or demultiplexing light of multiple wavelengths. Collectively called an optical fiber coupler.

  The optical fiber coupler of the present invention has a structure as shown in FIG. 1, removes the coated portions of the coated optical fibers 10 and 20, and cleans the exposed core portions 1 and 2 with alcohol or the like. Thereafter, the core parts 1 and 2 are closely aligned by paralleling or crossing with an alignment jig or the like, and the optical fibers 10 and 20 are stretched left and right in the longitudinal direction while being heated by a burner such as oxygen-propane or hydrogen. A tapered fusion-stretching portion 3 is formed. The coupler body 4 obtained in this way is placed on a concave groove 5a provided in a substrate 5 such as quartz glass, and bonded via an adhesive 6 that is cured by energy rays such as ultraviolet rays and visible rays. To do.

  According to such an optical fiber coupler, in order to obtain high reliability, the coating specification of the adhesive 6 becomes important. Since the adhesive also expands and contracts due to changes in the use environment of the optical fiber coupler, the optical fiber coupler body is also susceptible to expansion and contraction. Therefore, various conditions such as various characteristics of the adhesive, application amount, application position, and curing state are important.

Here, in the optical fiber coupler of the present invention, the adhesive 6 has a tensile shear adhesive strength of 5 MPa or more and a total coating volume of 0.36 to 5.6 mm ³ .

By setting the tensile shear adhesive strength of the adhesive 6 to 5 MPa or more, the holding power between the coupler body 4 and the substrate 5 becomes high, and an optical fiber coupler having a high tensile strength can be obtained. When the tensile shear bond strength is less than 5 MPa, the holding force between the coupler body 4 and the substrate 5 is reduced, and there is a possibility that the optical fiber coupler may be broken when tension is applied. At the same time, by setting the total application volume to 0.36 to 5.6 mm ³ , an optical fiber coupler having an optimum environment resistance and an optimum application amount of the adhesive can be obtained. When the total coating volume is less than 0.36 mm ³ , the adhesive force between the coupler body 4 and the substrate 5 is small, and the adhesive 6 is removed from the substrate 5 when a load such as pulling the optical fibers 10 and 20 in the longitudinal direction is applied. The coupler main body 4 is destroyed due to peeling. In particular, the coupler main body 4 often catches the optical fibers 10 and 20 accidentally in the field and is often subjected to a strong tensile stress. In that case, if the coating volume is too small, the coupler body 4 is easily destroyed. On the other hand, if it exceeds 5.6 mm ³ , the adhesive expands and contracts due to temperature changes in the usage environment, so that the coupler body 4 is also easily affected by expansion and contraction, and the stress increases as the coating volume increases. If the coating volume is too large, the stress is so great that the coupler body 4 is destroyed. In particular, the coating volume is more preferably 0.8 to ⁴ mm ³ . Here, the coupler main body 4 that satisfies both the tensile strength and the environmental resistance can be obtained by simultaneously specifying the tensile shear adhesive strength and the total application volume of the adhesive 6.

  The tensile shear adhesive strength of the adhesive 6 is determined according to the method specified in JIS K 6850. The specified portion is bonded between test pieces of the same material whose dimensions are specified, and measured by a tensile tester. Is.

  The substrate 5 is preferably made of quartz glass having a linear expansion coefficient equivalent to that of the optical fibers 10 and 20, but metal, crystallized glass, or ceramics may be used.

  The total application volume of the adhesive 6 is measured by comparing the weight before and after the application of the adhesive 6 with a high-performance weight scale.

  As described above, the application volume of the adhesive 6 can be adjusted by adjusting the viscosity of the adhesive 6 and applying and bonding the adhesive 6 as will be described in detail later.

Further, the adhesive 6 is applied to both end portions A of the substrate 5 and both end portions B of the fusion stretched portion 3 as shown in FIG. a 0.16～1.6Mm ^3, the coating volume per one place the ends B of the fused and extended portion 3 is preferably a 0.02～1.2Mm ^3.

  The coupler body 4 is generally joined to the substrate 5 only at both ends A of the substrate 5. Further, the core portions 1 and 2 of the optical fibers 10 and 20 and the substrate at both ends B of the fusion stretched portion 3. By joining 5, it is possible to reinforce a weakly strong boundary portion where the core wire portions 1 and 2 are branched and joined.

Here, the both ends A of the substrate 5 are intended to join the boundary between the core portions 1 and 2 of the optical fibers 10 and 20 and the covering portion and the substrate 5. By setting the coating volume per location to 0.16 to 1.6 mm ³ , an appropriate holding force can be obtained between the coupler body 4 and the substrate 5, and heat can be generated between the coupler body 4 and the substrate 5. Even when stress due to expansion or thermal contraction occurs, the holding force can be in an appropriate range, so that it is possible to effectively prevent the coupler body 4 from being disconnected due to the stress applied. When the coating volume is less than 0.16 mm ^3, the holding force between the coupler body 4 and the substrate 5 is reduced. On the other hand, when it exceeds 1.6 mm ³ , the amount of the adhesive 6 is excessively increased, so that the expansion / contraction stress May increase and stress may be applied to the coupler body 4 to cause disconnection.

Further, by coating volume per one place the ends B of the fused and extended portion 3 is to 0.02～1.2Mm ^3, both end portions B of the strength weak fused and extended portion 3 at an appropriate strength Can be reinforced.

If the coating volume is less than 0.02 mm ³ , reinforcement may be insufficient and disconnection may occur. On the other hand, when the thickness exceeds 1.2 mm ³ , the amount of the adhesive 6 is increased and the expansion and contraction stress is increased, so that stress is applied to the coupler body 4 and the reliability is lowered.

  In addition, the application volume of the adhesive 6 in each part is measured by comparing the weight before and after the application of the adhesive 6 with a high-performance weighing scale as described above. Moreover, in order to adjust the application volume of the adhesive 6, it can obtain by adjusting the viscosity of the adhesive 6 and apply | coating and joining so that a detail may mention later.

  Further, as shown in FIG. 2A, the adhesive 6 at both ends A of the substrate 5 is in the range of 2 to 4 mm from the end surface of the substrate 5 in the longitudinal direction of the optical fibers 10, 20, It is preferably applied so as to cover the entire peripheral surfaces of the core wire portions 1 and 2, and the boundary between the coated portions of the optical fibers 10 and 20 and the core wire portions 1 and 2 is preferably located at the center of the adhesive 6.

  As shown in FIG. 2 (a), the application length of the adhesive 6 from the end face of the substrate 5 is set in the range of 2 to 4 mm. Here, the longitudinal direction of the optical fibers 10 and 20 is the long side of the substrate. The direction parallel to is shown.

  By setting the application area of the adhesive 6 to 2 to 4 mm, the holding force between the coupler body 4 and the substrate 5 is increased, and an optical fiber coupler having a high tensile strength can be obtained. When the application area of the adhesive 6 is less than 2 mm, the adhesive strength is small, and when it exceeds 4 mm, the adhesive 6 is too much and is easily affected by expansion and contraction. Furthermore, it is more preferable to set it as 2.5-3.5 mm.

  At the same time, since the boundaries 1a and 2a of the coated portions of the optical fibers 10 and 20 and the core wire portions 1 and 2 are located at the center of the adhesive 6, the adhesive force between the coupler body 4 and the substrate 5 can be increased. The holding power between the coupler main body 4 and the substrate 5 is very high, and an optical fiber coupler with higher tensile strength can be obtained. The central portion of the adhesive 6 is ± 10% from the center of the length in the direction of the axis C of the adhesive 6 when the optical fiber coupler is viewed from the side facing the main surface of the substrate 5, and is orthogonal to the axis C. The range of ± 10% from the center in the direction of

  The adhesive strength between the coupler body 4 and the substrate 5 is greatly influenced by the adhesion specifications of the both ends A of the substrate 5, and the covering portions of the optical fibers 10 and 20 are often made of an acrylate resin. When there is only this covering portion at both end portions A and there are no core wire portions 1 and 2, slippage occurs at the boundary between the adhesive 6 and the covering portion, and the adhesive force is reduced. On the contrary, when the covering portion is outside the substrate 5, the edge portion of the end portion of the substrate 5 such as quartz glass may come into contact with the core wire portions 1 and 2 and break. For example, when the application area of the adhesive 6 is 2 mm, the boundary between the core wire parts 1 and 2 and the covering part is preferably in the range of 1 mm ± 0.5 mm from the end face of the substrate 5.

  Further, the adhesive 6 at both ends B of the fusion stretched portion 3 is ± 0.5 to ± 0.5 in the longitudinal direction from the base point 3a of the fusion stretched portion 3, that is, in the direction of the axis C, as shown in FIG. It is preferably coated so as to cover the entire circumference of the optical fibers 1 and 2 within a range of 1.5 mm.

  Here, the base point 3a of the fusion stretched portion 3 is a cross section in the direction perpendicular to the axis C around the boundary between the fusion stretched portion 3 of the coupler body 4 and the core wire portions 1 and 2, and the cross section is In the cases as shown in (1) to (3), the core line portions 1 and 2 of the optical fibers 10 and 20 are not overlapped, and the position (2) having no gap is defined as the base point 3a of the fusion stretched portion 3.

  Since the adhesive 6 is applied so as to cover the entire circumference of the optical fibers 1 and 2 within a range of ± 0.5 to ± 1.5 mm from the base point 3a of the fusion stretched portion 3, the base point weak in strength. 3a can be reinforced with appropriate strength. If the coating area is less than ± 0.5 mm, the reinforcement of the base point 3a is insufficient and there is a risk of disconnection. On the other hand, if it exceeds ± 1.5 mm, the amount of the adhesive 6 is increased and the expansion and contraction stress is increased, so that stress is applied to the coupler body 4 and the reliability is lowered.

  In addition, in order to adjust the application | coating range of the adhesive agent 6, it can obtain by adjusting the viscosity of the adhesive agent 6 and apply | coating and joining.

  Here, a method for variously adjusting the application condition of the adhesive 6 as described above will be described.

  First, the coupler body 4 is disposed in the concave groove 5 a of the substrate 5. At this time, it arrange | positions carefully so that it may become left-right symmetric from the center of the board | substrate 5. FIG.

  And the adhesive agent 6 is apply | coated to a predetermined position in the state whose viscosity is 50000-200000 mPa * s. In order to apply the adhesive 6 to a predetermined position, control can be easily performed by using a high-viscosity dispenser for extruding the adhesive by air pressure and a trace amount dispenser.

  When the viscosity of the adhesive 6 at the time of application is less than 50000 mPa · s, the viscosity is low, the sagging of the adhesive 6 in the direction of the axis C of the substrate 5 is increased, and the application area to the coupler body 4 is increased. Be susceptible to shrinkage. On the other hand, when the viscosity of the adhesive 6 exceeds 200,000 mPa · s, the viscosity becomes too high, so that the adhesive 6 and the substrate 5 are less likely to be wetted and the adhesive force may be reduced. Management becomes very difficult, and the coating amount becomes a factor of variation characteristic variation.

  The adhesive 6 used here is mainly an epoxy-based or acrylate-based visible light curable resin, ultraviolet curable resin, etc., and when the storage temperature is low, the viscosity is high and the storage temperature is high. In some cases, the viscosity is low. Therefore, the viscosity of the adhesive 6 can be adjusted to a desired value by adjusting the temperature.

  Since the time required for the application work elapses from the start of application of the adhesive 6 to the start of curing, the viscosity of the adhesive 6 tends to be affected by the room temperature or the like and becomes lower with the passage of time.

  Therefore, it is preferable to start curing in a state where the viscosity is 30000 mPa · s or more, and the sagging of the adhesive 6 to the substrate 5 is reduced, and the application position of the adhesive 6 can be managed. When the viscosity of the applied adhesive 6 is less than 30000 mPa · s, the sagging increases and the contact area of the adhesive 6 with the core wire portions 1 and 2 increases, and the influence of expansion and contraction increases.

  In the case of the adhesive 6 in which the viscosity does not change even at a low temperature or at a normal temperature, temperature management of the adhesive 6 is not necessary.

  Thus, the adhesive 6 is applied in a state where the viscosity of the adhesive 6 is 50000 mPa · s to 200000 mPa · s, and considering that the viscosity decreases with the passage of time, the adhesive 6 in a viscosity state of 30000 mPa · s or more. By starting curing, a predetermined amount of the adhesive 6 can be applied to a predetermined location, and the sagging of the adhesive 6 is preferably 1 mm or less in comparison between immediately after application of the adhesive 6 and after curing.

  In addition, when applying the adhesive 6 to the base point 3a of the fusion stretched part 3, it is very difficult to find it even by observing the optical fiber coupler. The base point 3a is almost reproducible as long as the optical fiber coupler can be manufactured with a constant fusion-stretching condition, and displacement hardly occurs. In particular, since it is greatly influenced by the stretch length, even if the stretch length changes, the base point 3a at that time is disassembled in advance, and the correct boundary point is determined by grasping the positional relationship between the stretch length and the base point 3a. You can always figure out.

The adhesive 6 preferably has a Young's modulus of 1000 to 6000 MPa, a curing shrinkage of 1% or less, and a linear expansion coefficient of 1 × 10 ⁻⁵ / ° C. or less at the glass transition temperature or lower. When the Young's modulus is less than 1000 MPa, the adhesive 6 is too soft and weak against tensile stress, and when it exceeds 6000 MPa, it is too hard and tends to be brittle during vibration and impact. When the curing shrinkage rate exceeds 1%, the shrinkage during curing is large, and tensile stress is applied to the optical fiber coupler, causing damage. Further, when the linear expansion coefficient is below the glass transition temperature and exceeds 1 × 10 ⁻⁵ / ° C., when the temperature changes in the use environment, stress is applied due to expansion and contraction, which causes destruction.

  Next, examples of the present invention will be described.

  Optical fiber coupler samples as shown in FIG. 1 were prepared by changing the adhesive application volume in various ways.

  First, a coupler body was manufactured with a wavelength band of 1550 nm, a branching ratio of 50 ± 3%, and an excess loss of 0.1 dB or less.

  First, an adhesive having a tensile shear adhesive strength of 3 to 9 MPa was prepared by changing the epoxy component of the adhesive. Then, the coupler main body is placed on the concave groove of the substrate made of quartz and the temperature of each adhesive is adjusted so that the viscosity is variously adjusted as shown in Table 1, and both ends A of the substrate and both ends of the fusion stretched portion are formed. It joined by changing and changing the application | coating volume of the part B variously.

Also, the adhesive application position at both end portions A of the substrate is 2 to 4 mm from the end surface of the substrate, and is adjusted and bonded so that the boundary between the coated portion of the optical fiber and the core portion comes to the central portion of the adhesive. It adjusted and joined so that it might become the range of +/- 0.5-1.5mm centering on the end surface of a stretched part.

  In addition, the tensile shear adhesive strength measured the application | coating volume with the high precision weight scale according to JISK6850.

  Then, a tensile test of 230 g for 1 minute was performed on the obtained optical fiber coupler sample.

Here, only the presence or absence of disconnection was confirmed.

  In addition, as a thermal shock test, samples that were not disconnected in the tensile test were kept at 85 ° C. for 30 minutes, kept at −40 ° C. for 30 minutes, and the temperature was changed for 5 minutes. Then, the maximum fluctuation amount of the insertion loss before and after the experiment was measured.

The results were as shown in Table 1.

From the results of Table 1, using an adhesive having a tensile shear adhesive strength of 5 MPa or more, the viscosity is applied at 50000-200000 mPa · s, cured at 30000 mPa · s and bonded, and the total applied volume is 0.36-5 In the samples (Nos. 5, ⁶ , 8 to 20) of .6 mm ³ , disconnection did not occur in the tensile test, and the variation in insertion loss could be reduced to 0.21 dB or less.

In particular, the coating volume per location on both ends A of the substrate is 0.16 to 1.6 mm ³ , and the coating volume per location on both ends B of the fusion stretched portion is 0.02 to 1.2 mm ^3. The samples (Nos. 5, 6, 8, 9, 11, 12, 14-17, and 19) were not disconnected in the tensile test, and the variation in insertion loss was 0.08 dB or less. .

On the other hand, the samples (Nos. 1, 2, and 3) using an adhesive having a tensile shear adhesive strength of less than 5 MPa were broken in the tensile test. Samples (Nos. ⁴ and 7) having a total coating volume of 0.3 mm ³ had a large insertion loss fluctuation.

In addition, the samples (No. 21, 22) having a total application volume exceeding 5.6 mm ³ also had large insertion loss fluctuations.

It is a top view which shows the structure of an optical fiber coupler. (A) is an expansion explanatory view of Drawing 1A part of the present invention. (B) is an enlarged explanatory view of FIG. 1B part of the present invention. It is a top view which shows the structure of the conventional optical fiber coupler. It is a top view which shows the structure of the conventional optical fiber coupler.

Explanation of symbols

1, 2: Core wire part 3: Fusion stretch part 4: Coupler body 5: Substrate 5a: Groove 6: Adhesive 7: Adhesive 8: Other adhesive 10, 20: Optical fiber A, B: Adhesive position

Claims (5)

An optical fiber coupler in which the core portions of a plurality of optical fibers from which the coating has been removed are fused and stretched, and bonded onto a substrate via an adhesive, wherein the adhesive has a tensile shear adhesive strength of 5 MPa or more. An optical fiber coupler having a total coating volume of 0.36 to 5.6 mm ³ . The adhesive is applied to both end portions of the substrate and both end portions of the fusion stretched portion, and the coating volume per location at both end portions of the substrate is 0.16 to 1.6 mm ^3. 2. The optical fiber coupler according to claim 1, wherein a coating volume per one portion of both ends of the portion is 0.02 to 1.2 mm ³ . The adhesive at both ends of the substrate is applied so as to cover the entire circumference of the optical fiber in the range of 2 to 4 mm in the longitudinal direction of the optical fiber from the end surface of the substrate, and the boundary between the coated portion of the optical fiber and the core portion is The optical fiber coupler according to claim 2, wherein the optical fiber coupler is located at a central portion of the adhesive. The adhesive at both ends of the fusion stretched part is applied so as to cover the entire circumference of the optical fiber in the range of ± 0.5 to ± 1.5 mm in the longitudinal direction from the base point of the fusion stretched part. An optical fiber coupler according to claim 2 or 3. 5. The method of manufacturing an optical fiber coupler according to claim 1, wherein an optical fiber is disposed on the substrate, and the adhesive is placed at a predetermined position in a state where the viscosity is 50000 mPa · s to 200000 mPa · s. A method of manufacturing an optical fiber coupler, comprising: applying and then bonding in a state where the viscosity is 30000 mPa · s or more after coating.

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