WO2005057260A1

WO2005057260A1 - Optical fiber coupler and process and device for producing the same

Info

Publication number: WO2005057260A1
Application number: PCT/JP2004/017148
Authority: WO
Inventors: Shunji Hirayama; Yoshiaki Takeuchi; Fuyuki Miura; Shigeru Uzawa; Katsuo Mabuchi
Original assignee: Osaki Electric Co., Ltd.
Priority date: 2003-12-09
Filing date: 2004-11-18
Publication date: 2005-06-23
Also published as: TW200527020A; CN1890589A; JP2005172972A; TWI344556B; JP3974106B2; CN100392451C

Abstract

A conventional optical fiber coupler requires a preprocessing process or different optical fibers having strictly uniform characteristics. The inventive optical fiber coupler is a 1×2 wide band optical fiber coupler for branching or coupling propagating lights between an optical fiber (1a) and an optical fiber (1b). Both optical fibers (1a, 1b) are identical single-mode optical fibers available on the market as a standard type. An optical coupling part (21) of the optical fiber coupler is formed by fusing and elongating the optical fibers (1a, 1b) with a part of the optical fiber (1b) kept wound around the optical fiber (1a). Winding amount of the optical fiber (1b) with respect to the optical fiber (1a) is adjusted such that the difference in length between both optical fibers (1a, 1b) at the optical coupling part (21) is equal to the minimum possible length required for substantially equalizing the degrees of coupling of propagating lights at the optical fibers (1a, 1b).

Description

Specification

Optical fiber force bra and method for manufacturing the same

Technical field

The present invention relates to an optical fiber force bra used for branching / coupling / multiplexing of an optical signal in an optical communication system, an optical sensor system or the like, a method of manufacturing the same, and an apparatus for manufacturing the same. It relates to a power bra type optical coupler (optical fiber splitter).

Background art

In an optical communication system, in order to perform large-capacity communication, a wavelength division multiplex communication system in which transmission and reception are performed using light of a plurality of wavelengths has been proposed. In an optical communication system using a wavelength division multiplexing communication method, optical signals of a plurality of respective wavelengths are equally branched in an optical fiber power bra used for monitoring and distributing optical signals, that is, light of each wavelength is It is considered as an important factor in system construction that the branching ratio 'coupling ratio (hereinafter referred to as the optical coupling degree) does not change. An optical fiber force bra having such a flat wavelength characteristic is a component suitable for application to an optical sensor system or the like whose application range is wide apart from optical communication systems. Therefore, various optical fiber power bras with low wavelength dependence have been proposed for use in such optical communication systems.

[0003] For example, in the case of a 2-branch broadband optical fiber coupler (1 x 2 optical fiber coupler or 2 x 2 optical fiber coupler), the wavelength dependence is reduced by making the propagation constant different between the optical fibers. That is done (see Patent Document 1). If the propagation constants of the two optical coupling parts are different from each other, the optical coupling is incomplete and the maximum coupling degree is 100% or less. Therefore, by controlling the difference in the propagation constants, it is possible to control the maximum degree of coupling in the optical coupling section to 50% or less, and as a result, it is possible to realize a wide band and nearly uniform branching ratio. In order to make the transmission constants different, it is necessary that the outer diameter of each optical fiber, the core diameter, the relative refractive index difference (cutoff), etc. be mutually different in the optical coupling portion.

[0004] As a specific method of wide band communication, the force to differentiate the propagation constant at the optical coupling portion by the same optical fiber by the pretreatment becomes the force of either using a different optical fiber. In the former example, one optical fiber of the same two optical fibers is heated and drawn to form a small diameter portion having a tapered portion, and then the small diameter portion of one heated optical fiber is formed. In the pre-stretching method (see Patent Document 2 and Patent Document 3) in which both optical fibers are fused and drawn (see Patent Document 2 and Patent Document 3), the dopant is thermally diffused in the core of one of the two optical fibers. There is a core diffusion method (refer to Patent Document 4) in which both optical fibers are fused and drawn after adjusting the refractive index distribution, an etching method, a polishing method and the like. As an example of the latter, it has been proposed to use an optical fiber in which the outer diameter, the core diameter, the relative refractive index difference (cutoff), etc. are different beforehand. Furthermore, there is also a method in which the former method and the latter method are combined in which a part of two optical fibers having different relative refractive index differences in advance are fusion-drawn (see Patent Document 5).

[0005] Since these methods can change the branching ratio by controlling the asymmetry between the optical fibers, it is possible to use only 50:50 equal-branch optical fiber couplers and to obtain an uneven branch light such as 90:10. A fiber force bra can be created and applied to the creation of a tap force bra or the like.

[0006] In addition, in the case of a 50: 50 equal-branch optical fiber power bra, it is not necessary to make a difference in the propagation constants for wide band communication. For example, by aligning and fusing three optical fibers in parallel, and stretching it, 1 X 2 broadband 'equal-branch optical fiber with the central optical fiber as the input terminal and the two optical fibers at both ends as the output terminal Power bra can be realized.

[0007] This configuration is also applicable to multi-branch and equal-branch optical fiber force bra {1 XN (N> 2)}, and one N input optical fibers are surrounded by N other output optical fibers. By symmetrically aligning and fusion drawing, it is possible to create a 1 × N broadband 'equal-branch optical fiber force bra. Thus, in this configuration, (N + 1) optical fibers are used. Also, in this case, it is theoretically impossible to slightly increase the excess loss depending on the wavelength.

[0008] In order to avoid this, it is necessary to introduce asymmetry between the optical fibers even in the 1 × N broadband 'equal branch optical fiber power bra. For this reason, as in the case of the two-branch broadband 'unequal-branch optical fiber bac- ter, a small diameter portion having a taper portion is formed in one optical fiber of the same plurality of optical fibers. A pre-stretching method (see Patent Document 6) prepared by fusion drawing with another identical optical fiber not having a diameter portion (see Patent Document 6), or by mutually winding a plurality of optical fibers while applying uniform tension. A method (see Patent Document 7) is proposed in which stretching is performed and the taper of the fusion stretching portion of the optical fiber force bra is made asymmetric. Patent Document 1: Patent No. 2711351

Patent Document 2: Japanese Patent Publication No. 6-040167

Patent Document 3: Patent No. 2645458

Patent Document 4: Patent No. 2958179

Patent Document 5: Patent No. 2848832

Patent Document 6: US Patent No. 5,751,873

Patent Document 7: US Patent No. 5883992

[0009] In the case where the propagation constant is differentiated by the pretreatment with the same optical fiber as in the method of broadening the bandwidth shown in Patent Literature 1 and Patent Literature 4, however, the number of pretreatment steps is increased. Good controllability in this pre-treatment process can be a fatal cause of yield reduction. That is, the wide band characteristics of the branching ratio are very sensitive to the amount of pretreatment (taper shape, etching amount, polishing amount, etc.), and this can not be corrected after fusion and drawing.

Further, as described in Patent Document 5 etc., in the wide band method using an optical fiber having different outer diameter, core diameter, relative refractive index difference (cutoff), etc., characteristics are strictly aligned. There is a problem with the economics because it is necessary to customize each optical fiber. Also, even if an optical fiber with exactly the same characteristics can be obtained, it is difficult to exactly align the parameters in the longitudinal direction of the optical fiber. Therefore, this method of broadening the bandwidth can cause deterioration of the characteristics of the optical fiber force bra and a decrease in yield when producing the optical fiber force bra.

[0011] Further, as in the case of the broadband signal method of Patent Document 6, in the case of producing a 1 XN broadband optical fiber force bra using N optical fibers, stretching processing is performed on several optical fibers as pre-processing. Need to be In addition, in the method of using one N + 1 optical fiber as a 1 × N optical fiber coupler, the wavelength dependence of the excess loss is theoretically increased as described above. In addition, since the branching ratio is limited to equal branching, there is a disadvantage that an unequally branched optical fiber force bra can not be created. Furthermore, in the method of introducing an asymmetric taper with a 1 X N optical fiber force bra, as in the wide band method of Patent Document 7, it is necessary to make the taper length longer than necessary, and the total length of the optical fiber cab In addition to having a defect, the controllability of the asymmetric taper shape becomes a problem, which causes a decrease in yield.

Disclosure of the invention The present invention has been made to solve such a problem, and an optical fiber power bra provided with an optical coupling portion that couples propagation light of one optical fiber to one or more other optical fibers. The length of one optical fiber and the other one or more optical fibers in the optical coupling portion are different from each other, and the length of the optical coupling portion is different for each optical fiber at at least two specific wavelengths. It is characterized in that it has a minimum length such that the degree of optical coupling of the propagating light of the beam is approximately equal.

According to such a configuration, for example, in a part or all of the optical coupling portion, one optical fiber is disposed linearly or substantially linearly, and the other one or more optical fibers are meandered. Asymmetry can be introduced between the optical fibers in the optical coupling portion by making the lengths of the optical fibers in the optical coupling portion different from each other by means such as

For this reason, it is possible to introduce asymmetry which is necessary to perform the pre-processing accurately to differentiate the propagation constants of the same optical fiber in advance. Further, asymmetry is controlled by the length of each optical fiber at the optical coupling portion, it can be corrected at the time of fusion and drawing of each optical fiber at the optical coupling portion. Therefore, the yield can be increased compared to the conventional optical fiber force bra, which is sensitive to the amount of pre-processing and can not correct the propagation constant at the time of fusional fusion drawing.

[0015] In addition, since it is not necessary to prepare different optical fibers having exactly the same characteristics, the economy is excellent. In addition, since it is not necessary to exactly align the parameters in the length direction of the optical fiber, the characteristics of the optical fiber force bra may not be deteriorated during production, nor will it cause a decrease in yield or yield. .

Also, by controlling the difference in length of each optical fiber at the optical coupling portion, it is possible to obtain an arbitrary branching ratio that is not limited to the 50: 50 equal division ratio. Therefore, the present invention is also applicable to a general 1 XN unequally-branched optical fiber force bra, which is only divided by the IX 2 unequally-branched fiber optic power bra. Furthermore, there is no problem that the wavelength dependence of the excess loss becomes large in principle, as in the conventional broadband 匕 method using N + 1 optical fibers to obtain a 1 × N broadband 'etc. branched optical fiber power bra. . Furthermore, since one optical fiber can be used for input and output of signal light, it is possible to obtain a 1 XN wide-band optical fiber power bra using N less optical fibers. Also, to avoid this problem, as in the case of introducing asymmetry by using an asymmetry taper to a 1 X N broadband 'isobranch optical fiber force bra The controllability of the tapered shape is a problem, and the yield does not decrease. In addition, as in the case of introducing asymmetry using an asymmetric taper, it is possible to obtain an optical fiber force bra having a wide branch ratio that does not increase the taper length more than necessary.

Furthermore, the present invention is characterized in that one optical fiber and one or more other optical fibers have the same optical fiber power.

According to this configuration, even when the same optical fiber is used, by making the lengths of the respective optical fibers at the optical coupling portion different from each other, the propagation constants differ among the respective optical fibers. Asymmetry can be introduced into the light coupling portion easily without putting it on.

Therefore, even when the same optical fiber is used, it is possible to easily obtain the above-mentioned optical fiber force bra having a wide branching ratio.

The present invention also includes an alignment step of aligning a plurality of optical fibers with one another, and a fusion drawing step of fusion bonding and drawing each optical fiber aligned by this alignment step to form an optical coupling part. In the method of manufacturing an optical fiber force bra including the step of arranging, at least one optical fiber is arranged in a straight line or a substantially straight line, and an aligning step is a brazing step in which one or more other optical fibers are wound around it. And the like.

According to such a configuration, the difference in length of each optical fiber at the optical coupling portion can be obtained by changing the amount of adhesion of the other optical fiber to the linear or almost linear optical fiber. It can be adjusted.

For this reason, by changing the amount of brazing of the other optical fiber to the linear or nearly linear optical fiber, the asymmetry between each optical fiber is controlled, and the wide band region with a desired branching ratio is obtained. An optical fiber force bra having the characteristics can be easily obtained.

Furthermore, the present invention is characterized in that the tension applied to the optical fiber disposed in a straight line or substantially in a straight line is greater than the tension applied to the other optical fibers wound around the optical fiber. Do.

[0024] According to such a configuration, the tension of a larger tensioned linear or nearly linear optical fiber is used, and another optical fiber having a small tension is provided around the optical fiber. Wrapping allows straight or nearly straight optical fiber forces to minimize bending due to forces from other optical fibers that wrap around it. It becomes.

Therefore, when winding another optical fiber around a linear or nearly linear optical fiber, the linear or nearly linear optical fiber is bent and the amount of bending of the other optical fiber is increased. It is prevented that it is not constant. In other words, the amount by which the other optical fiber is wound around the linear or nearly linear optical fiber becomes constant, and it becomes possible to easily realize the reproducible wedge state. Therefore, it is possible to easily manufacture an optical fiber force bra having a wide range of branch ratio characteristics, and the yield is increased.

Further, according to the present invention, an alignment mechanism for aligning a plurality of optical fibers with each other, and a fusion / stretching mechanism for fusion-stretching each optical fiber aligned by this alignment mechanism to form an optical coupling portion In a manufacturing apparatus for an optical fiber force bra having a and a winding mechanism for winding one or more other optical fibers around at least one optical fiber arranged in a straight line or a substantially straight line, and a straight line And a tension applying mechanism for keeping the tension applied to the optical fiber arranged in a substantially or substantially straight shape larger than the tension applied to the optical fiber wound around the optical fiber.

According to such a configuration, the brazing mechanism winds another optical fiber around the linear or nearly linear optical fiber. During this winding, a predetermined tension is applied to each optical fiber by the tensioning mechanism so that the straight or nearly straight optical fiber is not bent by the force received from the other optical fino wrapped around it. The amount by which the optical fiber wraps around a straight or nearly straight optical fiber is constant.

For this reason, an apparatus for manufacturing a fiber optic force bra is provided which can easily control the asymmetry between the optical fibers in the optical coupling portion by the difference in their lengths.

According to the present invention, as described above, it is necessary to accurately pre-treat the difference in the propagation constant of the same optical fiber in advance. By introducing asymmetry to the optical coupling portion of the optical fiber power bra that does not prepare the fiber, it is possible to obtain a reliable broadband optical fiber power bra with low wavelength dependency of the optical branching ratio at low cost. It becomes possible. In addition, a 1 x N optical fiber force coupler with an arbitrary branching ratio can be realized with N optical fibers.

In addition, each light beam can be changed by changing the amount of brazing of the other optical fiber to one optical fiber. Provided are a method of manufacturing an optical fiber power bra and an apparatus for manufacturing the same, by which asymmetry between fibers can be controlled and an optical fiber power bra having branch characteristics having a desired wide band characteristic can be manufactured with high productivity.

Brief description of the drawings

FIG. 1 is a perspective view showing an outline of a configuration around an optical coupling portion of an optical fiber force bra according to an embodiment of the present invention.

FIG. 2 is a side view showing an optical fiber brazed state prior to fusion drawing of the optical fiber force bra of FIG.

FIG. 3 is a graph showing the relationship between the wavelength of the optical fiber force bra shown in FIG. 1 and the insertion loss.

FIG. 4 is a plan view and a side view showing an outline of the configuration of a fiber holding mechanism and a heating mechanism of an optical fiber force bra manufacturing apparatus according to an embodiment of the present invention.

[FIG. 5] A perspective view showing an outline of a fiber rotating mechanism constituting the optical fiber force bra manufacturing apparatus shown in FIG. 4 before and at the time of brazing.

FIG. 6 is a graph showing the relationship between the fusion drawing time of the optical coupling part of the optical fiber force bra shown in FIG. 1 and the optical coupling degree of each optical fiber.

FIG. 7 is a perspective view showing an outline of a configuration around an optical coupling portion of a fiber optic force bra according to another embodiment of the present invention.

[FIG. 8] A side view showing a brazing state of the optical fiber before fusion drawing of the optical fiber power bra shown in FIG.

FIG. 9 is a cross-sectional view of the optical coupling portion of the optical fiber force bra shown in FIG. 7 before heating and drawing.

FIG. 10 is a graph showing the relationship between the wavelength of the optical fiber force bra shown in FIG. 7 and the insertion loss. BEST MODE FOR CARRYING OUT THE INVENTION

Next, the best mode for carrying out the present invention will be described.

FIG. 1 is a perspective view of an optical fiber force bra light coupling part periphery 2 a according to a first embodiment of the present invention.

This optical fiber coupler is a fused and drawn IX2 broadband optical fiber power bra that splits or couples propagating light between the optical fiber la and the optical fiber lb. Both optical fibers la and lb are identical single-mode optical fibers that are commercially available, respectively. Both optical fibers The la and lb have different outer diameters and waveguide parameters, and they are not pretreated to introduce anisotropy such as prestretching or etching. In each of the optical fibers la and lb, signal light of a plurality of wavelengths such as a wavelength of 1.31 m and a wavelength of 1.55 m propagate, for example, and wavelength division multiplexing communication is performed.

This optical fiber coupler comprises an optical coupling portion 21 for branching or coupling the propagating light between the optical fiber la and the optical fiber lb. As shown in FIG. 2, the optical coupling portion 21 is fused in a serpentine state in which a part of the optical fiber lb is wound around the linear or almost linear optical fiber la. It is configured to be stretched. Therefore, the lengths of the optical fibers la and lb at the light coupling portion 21 are different from each other. The amount of optical fiber lb applied to the optical fiber la is the difference between the lengths of both optical fibers la and lb at the optical coupling portion 21. Two specific wavelengths used in wavelength division multiplexing communication: 1.31 m and 1 At 55 m, the degree of coupling of the propagation light of each optical fiber la, 1 b is adjusted to be approximately equal.

FIG. 3 is a graph showing the wavelength characteristics of the optical fiber force bra, and the horizontal axis of the graph represents the wavelength of the signal light [/ z mL vertical axis represents the insertion loss [dB] of the signal path. The characteristic line A represents the output wavelength characteristic of the optical fiber la when the optical signal is input from the optical fiber la, and the characteristic line B represents the output wavelength characteristic of the optical fiber lb. As shown in the graph, the fiber optic force bra has a branching ratio of approximately 50:50 with an insertion loss of approximately 3 dB at both wavelengths of 1. 31 111 and 1.5 5 m, and it is used at both of these wavelengths A possible, wideband equal-branching feature is provided. The branching ratio can be controlled by changing the amount of wire bonding of the optical fiber lb to the optical fiber la, and it is possible to control the branching ratio other than the equal branch optical fiber power bra, for example, the wavelength 1. 31 It is also possible to easily make an IX 2 unequally branched optical fiber Bragg bra (5% tap force bra) with a branching ratio of 95: 5 that can be used at both wavelengths of / zm and 1.55 m.

Next, an optical fiber force bra manufacturing apparatus for manufacturing the optical fiber force bra will be described.

FIGS. 4 (a) and 4 (b) are a plan view and a side view of a fiber holding mechanism and a heating mechanism 3 of the optical fiber force bra manufacturing apparatus.

The fiber holding mechanism and the heating mechanism 3 of the optical fiber force bra manufacturing apparatus are provided with a pair of drawing stages 4a and 4b, and the microtorch 5 is placed between the drawing stages 4a and 4b. A torch stage 6 is provided. The microtorch 5 is for heating the light coupling portion 21 of the optical fibers la and 1b, and can be moved between the drawing stages 4a and 4b by the torch stage 6. The drawing stages 4a and 4b are for drawing the heated and melted optical fibers la and lb, and are structured so as to be able to move back and forth on a predetermined linear trajectory. The drawing stages 4a and 4b form, together with the microtorch 5, the optical drawing section 21 by fusion-bonding and drawing the optical fiber la and the optical fiber lb wound around the optical fiber la. Ru.

Further, an optical fiber clamp 7 for gripping one end of each of the optical fibers la and lb is provided at an end on the drawing stage 4a, and an optical fiber clamp 7 is provided on both the drawing stages 4a and 4b. Iber holders 8a and 8b and fiber rotation mechanisms 9a and 9b for winding the optical fiber lb around the optical fiber la are provided. In addition, optical fiber guides 10a and 10b are provided on the drawing stage 4b. The optical fiber guides 10a and 10b are configured so as to have roller forces rotatably provided on the drawing stage 4b for each of the optical fibers la and lb. Furthermore, on the right side of the extension stage 4b, an optical fiber supporting cylinder 11a, l ib is provided in a pair with the optical fiber guides 10a, 10b, and supported by the optical fiber supporting cylinder 11a, l ib Weights 12a and 12b are fixed to the optical fibers la and lb.

In the present embodiment, the weight of the weight 12a is 30 g, and the weight of the weight 12b is 25 g. The weights 12a and 12b, together with the optical fiber clamp 7 described above, maintain the tension applied to the linearly or almost linearly disposed optical fiber la more than the tension applied to the optical fiber lb wound around the optical fiber la. Are configured.

The tension generated by the weights 12a and 12b is smoothly transmitted from the optical fiber clamp 7 to the optical fiber la and lb located on the right side. The optical fiber supporting cylinders 11a and lib change the direction of tension by the weights 12a and 12b to smoothly transmit the tension to the optical fibers la and lb, and also constitute a roller force which does not cause excessive bending of the optical fibers la and lb. ing. The optical fiber clamp 7, the optical fiber support 10a and 10b, and the optical fiber support cylinders 11a and 1b constitute an alignment mechanism for aligning the optical fibers la and lb with each other on the extension stages 4a and 4b.

The optical fiber holders 8a and 8b are for holding the optical fibers la and lb during the fusion drawing operation of the optical fibers la and lb, and are provided on the center side of the drawing stages 4a and 4b. The There is.

The fiber rotation mechanism 9a is provided substantially at the center of the drawing stage 4a. The fiber rotating mechanism 9b is provided substantially at the center of the drawing stage 4b. As shown in FIGS. 5 (a) and 5 (b), the fiber rotating mechanisms 9a and 9b respectively have a pair of substrates 91 and a pair of cylindrical rotating members rotatably held by the respective substrates 91. And 92. The rotating bodies 92 arranged in the opposite direction are rotated in opposite directions to each other by a rotational driving mechanism (not shown). As shown in the figure, the rotor 92 has a reference hole 93 through which the optical fiber la is inserted at a position coinciding with the axial center which is the center of rotational movement, and is separated from the axial center by a predetermined distance. A rotational insertion hole 94 is formed at the position where the optical fiber lb opened along the axial center is inserted.

The optical fiber holders 8a and 8b and the fiber rotation mechanisms 9a and 9b described above constitute a brazing mechanism for winding another optical fiber lb around the optical fiber 1a.

Next, a method of manufacturing an optical fiber force bra using this manufacturing apparatus will be described.

First, the coating of the optical fibers la and lb to be the optical coupling portion 21 is removed, and the portion is disposed at the center of the drawing stages 4a and 4b, and one end of the optical fibers la and lb is as it is. With the fiber optic clamp 7. Next, as shown in FIG. 5 (a), one optical fiber la is inserted into the reference through hole 93 of the rotating body 92 constituting the fiber rotating mechanism 9a, 9b, and the other optical fiber lb is rotated Pass through the 92 holes of through hole 94. Then, the optical fiber la and lb are supported on the drawing stages 4a and 4b by the optical fiber support bases 10a and 10b and the optical fiber support cylinders 11a and 1b. As a result, as shown in FIG. 4, two optical fibers la and lb are aligned on the extension stages 4a and 4b. At this time, the optical fiber holders 8a and 8b are opened so that tension transmitted from the weights 12a and 12b is applied to the optical fibers la and lb located on the right side of the optical fiber clamp 7.

[0048] After that, weights 12a and 12b are attached to the other ends of the optical fibers la and lb, respectively. When the weights 12a and 12b are attached, the tension by the weights 12a and 12b is smoothly transmitted to the respective optical fibers la and lb through the rollers constituting the optical fiber guides 10a and 10b and the optical fiber supporting cylinders 11a and l ib. Different tensions are applied to each optical fiber la and lb.

[0049] In this state, the rotating bodies 92 of both the fiber rotating mechanisms 9a, 9b are You rotate only one. Since the optical fiber la inserted into the reference through hole 93 of the rotary body 92 is disposed at the center of the rotation axis of the rotary body 92, it does not revolve even when the rotary body 92 is rotated. On the other hand, the optical fiber lb inserted into the rotary through hole 94 rotates around the axial center of the rotary 92 as the rotary 92 rotates. Along with this rotation, as shown in FIG. 5 (b), the coating removal portion of the optical fiber lb of the optical coupling portion 21 located between the two fiber rotating mechanisms 9a and 9b is disposed linearly or almost linearly. It is wound around the coating removal part of the optical fiber 1 a of the light coupling part 21. At this time, since the tension applied to the optical fiber la is larger than the tension applied to the optical fiber lb, the revolution of the optical fiber lb does not bend the optical fiber la.

In the present embodiment, the rotator 92 of the fiber rotation mechanism 9b is rotated about 260 degrees. This rotation amount is a value obtained from the relationship between the maximum coupling degree of the propagation light of the optical fiber la and lb and the rotation angle, and this value is the type of the optical fiber and the structure of the manufacturing apparatus. This is a relative value that largely depends on the structure and mounting position of the optical fiber, the torch structure, etc.) and the preparation conditions (tension applied to the optical fiber, degree of fusion, etc.), not absolute values. In the present embodiment, the force of rotating only the fiber rotation mechanism 9b may rotate both of the fiber rotation mechanisms 9a and 9b in the opposite direction, particularly when the amount of rotation is large.

Subsequently, each of the optical fibers la and lb is held and held by the optical fiber holders 8a and 8b. Then, after the microtorch 5 is ignited, the microtorch 5 is moved to a predetermined position by the torch stage 6 and the sheath removing portions of the optical coupling portion 21 are heated and fused to each other, and then the drawing stages 4a and 4b are performed. The film was heated and drawn while gently pulling it apart from side to side, and the heating and drawing was stopped at a predetermined position to form a light coupling part 21. Next, after fixing both sides of the optical coupling portion 21 to the substrate, the whole was removed from the manufacturing apparatus, and no cage was performed to complete an optical fiber force bra.

[0052] FIG. 6 shows the heating and drawing time of the optical fiber la and lb (horizontal axis) and the respective optical couplings for the signal lights of the wavelengths 1.31 m and 1.55 m input from the optical fiber la. It is a graph showing the relationship with degrees (vertical axis). In the present embodiment, the heating and drawing are stopped at the time when the characteristics at the point where the degree of optical coupling at both wavelengths first agrees (point A in the figure) is obtained. Therefore, the difference in lengths of the two optical fibers la and 1b at the light coupling part 21 formed by the fusion drawing in this way is the two specific wavelengths 1.31 m and 1. 55 At / zm, it is set to the minimum length such that the coupling degree of the propagation light of each of the optical fibers la and lb is substantially equal.

According to the optical fiber power bra according to the present embodiment described above, the optical fiber lb is wound around the linear or substantially linear optical fiber la, and each optical fiber la at the optical coupling portion 21 is wound. , and lb can be made to have asymmetry between the optical fibers 1a and 1b at the light coupling portion 21 simply by making the lengths of Lb and Lb different from each other.

For this reason, it becomes possible to introduce asymmetry which is necessary to perform in advance a pretreatment for differentiating the propagation constant of the same optical fiber in advance as in the prior art. Further, the asymmetry is controlled by the length of each optical fiber la, 1b at the optical coupling portion 21, so that it can be corrected at the time of fusion and drawing of each optical fiber la, 1b at the optical coupling portion 21. . Therefore, compared with the conventional optical fiber camber which is sensitive to the amount of pretreatment and can not correct the propagation constant at the time of fusion / drawing, the optical fiber power bra according to the present embodiment makes the yield higher. Can do.

Further, the optical fiber power bra according to the present embodiment is excellent in economic efficiency because it is not necessary to prepare different optical fibers having exactly the same characteristics as in the conventional case. In addition, since it is not necessary to exactly align the parameters in the length direction of the optical fibers la and 1b, the characteristics of the optical fiber bra does not deteriorate during production, and the yield may be lowered. Absent.

Also, by changing the amount of brazing of the optical fiber lb relative to the optical fiber la, by controlling the difference in length of each optical fiber la and lb at the optical coupling portion 21, 50: 50 equal branching It is possible to obtain an optical fiber force bra of any branching ratio that is not limited to the ratio. In addition, it is possible to produce a general 1 X N unequal branch optical fiber power bra, which is only divided by the IX 2 unequal branch optical fiber power bra, in the same manner. Also, as with the conventional broadband method using N + 1 optical fibers to obtain a 1 × N broadband 'isobranch optical fiber coupler, there is also a problem that the wavelength dependence of excess loss becomes theoretically large. It is possible to obtain an IXN broadband optical fiber power bra using only one N optical fiber. Also, in order to avoid this problem, controllability of the asymmetric taper shape becomes a problem as in the case of introducing asymmetry to the 1 × N broadband 'equal branch optical fiber force bra using an asymmetric taper, which is a factor of yield reduction. It will never be. Also, in the optical fiber power bra according to the present embodiment, as in the case of introducing asymmetry using an asymmetric taper to a 1 × N broadband ′ equal-branch optical fiber coupler, it is possible to use a broadband ratio of branching ratio. Increasing the length does not become a factor of falling yield. Therefore, it is possible to obtain an optical fiber power bra having a branching ratio that does not increase the taper length more than necessary.

Further, in the present embodiment, the force described in the case where the optical fiber force bra is composed of the same optical fibers la and lb is the optical fiber power using the different optical fibers which need not necessarily be composed of the same optical fiber. A bra may be configured. That is, when using the same optical fibers la and 1b and different optical fibers, by making the lengths of the respective optical fibers in the optical coupling portion 21 different from each other, the propagation constant can be calculated between the respective optical fibers. Asymmetry can be introduced into the light coupling portion 21 easily without making a difference. For this reason, even when different optical fibers are used, it is possible to easily obtain the above-mentioned optical fiber QB with a wide branching ratio.

Further, in the method of manufacturing the optical fiber force bra according to the present embodiment, as described above, the alignment step of aligning the optical fibers la and lb with each other is linear or substantially linear for one optical fiber la. The other optical fiber lb same as that of the optical fiber la is placed around it, and the optical fiber la and lb at the optical coupling portion 21 have a brazing step to make the lengths of the optical fibers la and lb different from each other. There is. Therefore, by adjusting the weight of the weight 12a, 12b attached to the optical fiber la, lb and the amount of rotation of the rotator 92 constituting the fiber rotation mechanism 9a, 9b, the amount of brazing of the optical fiber lb relative to the optical fiber la By changing it, the difference in length of each optical fiber la and lb at the optical coupling portion 21 can be adjusted. Therefore, the asymmetry between each optical fiber la and lb is controlled by changing the amount of bias of the optical fiber lb with respect to the optical fiber la, and an optical fiber power bra having a desired wide band characteristic of the branching ratio is obtained. It can be easily obtained.

Further, in the method of manufacturing the optical fiber force bra according to the present embodiment, as described above, the optical fiber is wound around the optical fiber la, which is disposed linearly or almost linearly with the welding process. This is done by applying a tension greater than the tension applied to the fiber lb. Therefore, by using the tension of the large tensioned optical fiber la and winding the small tensioned optical fiber lb around the optical fiber la, the optical fiber la can be wound around it. Fiber to wrap lb Force does not bend under stress. For this reason, when the optical fiber lb is wound around the optical fiber la, the optical fiber la is prevented from being bent and the brazing amount of the optical fiber lb is not constant. That is, the amount by which the optical fiber 1b is wound around the optical fiber la becomes constant, and it becomes possible to easily realize a reproducible wrinkle state. Therefore, it is possible to easily manufacture an optical fiber force bra having a wide band characteristic of the branching ratio and to increase the yield.

In addition, as described above, the apparatus for manufacturing an optical fiber force bra according to the present embodiment has the same optical fiber as the optical fiber la, which is disposed around the linear or almost linear optical fiber la. The apparatus includes a bending mechanism for winding Iber lb and a tension applying mechanism for keeping tension applied to the optical fiber la larger than tension applied to the optical fiber lb wound on the optical fiber la. Therefore, when the optical fiber lb is wound around the optical fiber la by the brazing mechanism, the optical fiber la is wound around the optical fiber la by applying a predetermined tension to the optical fibers la and lb by the tensioning mechanism. The amount by which the optical fiber lb wraps around the optical fiber la is constant without bending due to the force received from the fiber lb. For this reason, an apparatus for manufacturing an optical fiber force bra is provided which can easily control the asymmetry between the optical fibers la and lb at the optical coupling portion 21 by the difference in their lengths.

Next, a second embodiment of the optical fiber force bra according to the present invention will be described.

[0063] FIG. 7 is a perspective view of a fusion drawing type 1 × 4 wide band optical fiber power bra light coupling part periphery 2b according to the present embodiment.

[0064] The optical fiber force bra around the optical coupling section 2b is an input / output dual-purpose optical fiber that is a straight optical fiber la located at the center, and the other optical fiber lb, lc, Id is an output that is spirally wound on it It is a dedicated optical fiber. Each of these optical fibers la-Id is also the same single mode optical fiber that is commercially available as a standard, as in the first embodiment. Also in the second embodiment, the optical fiber force bra may be configured using different optical fibers that are not identical. The optical fiber force bra coupler 22 is, as shown in FIG. 8, a part of the other three optical fibers lb, lc, and Id with respect to the linear or nearly linear optical fiber la. It is constructed by fusion drawing in a state of tightness. Therefore, the lengths of the optical fiber la and the other optical fiber lc1 Id at the optical coupling portion 22 are different from each other. Optical fiber for optical fiber la The application amount of the fiber lb, lc, Id is the difference in length between the optical fiber la and the other optical fiber lc 1 Id at the optical coupling part 22. Two specific wavelengths used in wavelength multiplexing communication 1. 31 m and 1 are adjusted so that the coupling degree of the propagation light of each optical fiber la, lb, lc, Id is almost equal.

The apparatus for manufacturing the optical fiber force bra has a configuration substantially similar to that of the optical fiber force bra manufacturing apparatus according to the first embodiment. In addition to the through hole 93, three rotational through holes 94 are opened symmetrically at the center of rotation, and the optical fibers la, lb, lc, Id pass through each of a total of four holes. . Also, as a mechanism for applying tension to the optical fiber la-Id, four mechanisms (fiber guide 10a-10d, optical fiber supporting cylinder 11a-id) independent of each other are provided, and in addition to the weight 12a, 3 Two weights 12b-12d force mounted on the end of each optical fiber la, lb, lc, Id. In this case, the weight of the weight 12a added to the optical fiber la is, for example, about 35 g, and the weight of the weights 12b to 12d added to the other optical fiber lb-Id is, for example, about 20 g. As described above, since the tension applied to the optical fiber la is larger than the tension applied to the other three optical fibers lb, lc, and Id, even in the present embodiment, the rectilinearity of the optical fiber la is ensured with a good yield. .

While such a tension is applied, the optical fibers lb, lc, and Id are helically wound around the optical fiber la as shown in FIG. 8, but in the present embodiment, the optical fiber rotation mechanism 9a , 9b were wound in opposite directions by 270 degrees. As in the case of the first embodiment, the amount of rotation can also be determined from the relationship between the rotation angle of each optical fiber la, lb, lc, and Id and the maximum coupling degree. The degree of optical coupling of the propagating light of lc and Id is almost equal. This value is also a relative value that largely depends on the type of optical fiber, the structure of the manufacturing apparatus, the preparation conditions, and the like, and is not an absolute value. Also, the optimum value of the rotation angle is a value that largely depends on the number of branches, and it is natural that the rotation conditions are completely different in the case of, for example, an I x 8 optical fiber power bra. In addition, the rotation amounts of the optical fiber rotation mechanisms 9a and 9b need to be the same, and only the rotation mechanism 9a or the rotation mechanism 9b may be rotated.

FIG. 9 is a view showing the cross-sectional structure of the light coupling portion of the optical fiber force bra.

In the figure, the position of the output-only optical fiber lb, lc, Id is the input-output combined optical fiber la. Forces arranged symmetrically with respect to each other If the tension given to all the optical fibers la, lb, lc, and Id is constant, a slight deviation of the relative position between the output-only optical fibers lb, lc, and Id will result. It causes the meandering of the centrally located optical fiber la. Therefore, in this case, it is difficult to obtain wide-band branching characteristics with high yield due to the non-symmetry of the light coupling portion 22 which makes it difficult to control the asymmetry of the structure in the light coupling portion 22 with high accuracy.

On the other hand, in the present embodiment, since the tension applied to the optical fiber la is larger than the tension applied to the other optical fibers lb, lc, Id, by the revolution of the optical fibers lb, lc, Id, The optical fiber la does not meander. Thus, as a method of winding the optical fiber lb, lc, Id, a plurality of optical Fino la, lb, lc, Id [weights 12a, 12b, 12c, 12d of different weights are attached, and a heavy weight 12a Light fiber 12b, 12c, 12d is attached by using tension of the attached optical fiber la and the light fiber 12b, 12c, 12d is twisted by twisting the optical fiber lb, lc, Id Optical fiber with the heavy weight 12a attached The winding method using the principle of winding around la makes it possible to easily realize a reproducible wrinkle state and to easily reproduce the branching ratio. As described above, by increasing the tension applied to the optical fiber la placed at the center, the bonding amount of the optical fiber lb, lc, Id becomes constant, the yield is improved, and the reproducibility becomes rich.

The cross-sectional structure of the optical coupling portion of the optical fiber power bra shown in FIG. 9 is the configuration of a 1 × 4 optical fiber power bra that is broadened by an asymmetric taper as disclosed in Patent Document 7 Similar to 1). The tension applied to the four optical fibers is the same as described in column 55, line 57 of column 4 and column 61, line 63 of the same document. Although not specified in the literature, the central optical fiber is likely to meander along its length. That is, as shown in FIG. 8, the probability that the central optical fiber la is kept in a straight line is considered to be greatly reduced. Therefore, in this case, the asymmetry between the optical fiber la and the optical fiber lb-Id is not guaranteed. Therefore, in the optical fiber fabric of the same document, asymmetry is introduced in the taper to secure a wide band of characteristics. The optical fiber rotation mechanism shown in the same document is used only to simply contact the four optical fibers to each other to form a taper, and in the same document, different tensions are applied between the optical fibers. The intention to introduce and introduce asymmetry is not fulfilled.

FIG. 10 shows the wavelength characteristics of the optical fiber force bra after the package manufactured according to the present embodiment. The horizontal axis of the graph represents the wavelength of the signal light [/ z mL, and the vertical axis represents insertion loss [dB] of the signal path. The characteristic line A represents the output wavelength characteristic of the optical fiber la, and the characteristic lines B, C, and D represent the output wavelength characteristics of the optical fibers lb, lc, and Id, respectively. As shown in the graph, the optical fiber coupler 2b has a branching ratio at both wavelengths of 1.3 m and 1.55 m and is approximately equal branched with an insertion loss of about 6 dB. A possible, wideband equal-branching feature is provided. This branching ratio can be controlled with high yield by changing the amount of polarization of the optical fiber lb-Id to the optical fiber la, and the desired branching ratio of 1 X 4 unequally branched optical fiber force bra is obtained. It is easy to make

Therefore, even with the optical fiber force bra according to the present embodiment, pretreatment such as pre-stretching and etching to introduce asymmetry, and a plurality of types of as in the conventional fusion stretch-type optical fiber camber, Using the same optical fiber By using four identical optical fibers la, lb, lc, and Id and introducing an asymmetric arrangement when forming the optical coupling part 22, broadband equal branch characteristics can be obtained. .

[0073] As described above, even with the optical fiber coupler created in this manner, a wide band equal-branching characteristic that can be used at both wavelengths of 1.31 μm and 1.55 m can be obtained, and an optical fiber can be obtained It is possible to control the branching ratio with a good yield by changing the amount of brazing of lb.

In the above embodiments, the weights 12a-12d are used to apply a load to the optical fiber la-Id, but other panel forces, magnetic forces, etc. may be used. In addition, although micro torch 5 was used as a heating source, electric heaters using ceramics etc., discharge, CO laser etc.

A heating method of 2 may be used.

Industrial applicability

In the above embodiment, the force described in the case where the optical fiber force bra according to the present invention is applied to 1 × 2 optical fiber force bra and IX 4 optical fiber force bra, for example, IX 3 optical fiber force plastic, 1 × It is also possible to apply the invention to other common 1 XN fiber optic force bras, such as 8-fiber couplers. Even when the present invention is applied to such an optical fiber force bra, the same function and effect as the above embodiment can be obtained.

Claims

The scope of the claims

[1] In an optical fiber coupler provided with an optical coupling portion for coupling the propagation light of one optical fiber to one or more other optical fibers,

The lengths of the one optical fiber and the one or more other optical fibers in the optical coupling portion are different from each other, and the lengths of the optical coupling portion are at least at two specific wavelengths. A fiber optic power bra characterized in that it has a minimum length such that the degree of optical coupling of the propagating light of the fiber is approximately equal.

[2] The optical fiber power bra according to claim 1, wherein the one optical fiber and the one or more other optical fibers are made of the same optical fino.

[3] In the optical coupling portion, the one optical fiber is disposed linearly or substantially linearly, and the one or more other optical fibers meander with respect to the one optical fiber. The optical fiber power bra according to claim 1 or 2, characterized in that:

[4] In the optical coupling portion, the one or more other optical fibers are arranged linearly or substantially linearly, and the one optical fiber is meandered relative to the one or more other optical fibers. The optical fiber power bra according to claim 1 or 2, characterized in that:

[5] An optical fiber comprising: an alignment step of aligning a plurality of optical fibers with each other; and a fusion drawing step of fusion-bonding and drawing the respective optical fibers aligned in the alignment step to form a light coupling portion. According to the manufacturing method of stupidity,

In the alignment step, at the light coupling portion, at least one optical fiber is arranged in a straight line or a substantially straight line, and a winding step is provided around the one or more other optical fibers. A method of manufacturing an optical fiber force bra characterized by the present invention.

[6] In the brazing step, the tension applied to the optical fiber disposed linearly or substantially linearly is larger than the tension applied to another optical fiber wound around the optical fiber. The method of manufacturing an optical fiber power bra according to claim 1.

[7] An optical fiber comprising: an alignment mechanism for aligning a plurality of optical fibers with each other; and a fusion drawing mechanism for fusion-stretching each optical fiber aligned by the alignment mechanism to form an optical coupling part. In the manufacturing equipment of

Other light around at least one optical fiber arranged in a straight or nearly straight line It has a bending mechanism that winds one or more fibers, and a tensioning mechanism that keeps the tension applied to the optical fiber arranged linearly or almost linearly larger than the tension applied to the optical fiber wound on the optical fiber. An optical fiber force bra manufacturing apparatus characterized by