JPH0498206A - Optical fiber terminal optical connector - Google Patents

Abstract

PURPOSE:To mutually connect optical fibers with low loss and low reflection by fusion splicing plural quartz group signal mode optical fibers having respectively different core diameters or specific refractive index differences, locally heating the vicinity of the connection part so as to diffuse a doping agent and obtaining an optical fiber terminal aligning the part other than the heat diffusion part as an aligned end face. CONSTITUTION:In order to obtain the optical fiber terminal, the optical fibers 1, 2 having respectively different diameters of cores 1A, 2A or specific refractive index differences are fusion-splices at first. Then, the vicinity of the fused part 3 is locally heated in a temperature range capable of suppressing the melting of the optical fibers but diffusing the doping agent contained in the cores 1A, 2A or clads 1B, 2B to form the doping agent diffusing part 4. After cutting off the optical fiber on a part separated from the diffusing part 4 on the optical fiber (2) side, a ferrule 5 is stuck and connected to the fibers 1, 2 and the fibers 1, 2 are ground together with a ferrule end face 5A as an aligned end face to obtain the optical fiber terminal 13. An optical connector 14 can be obtained by clamping the optical fiber terminals 13, 13' provided with connector housings 6, 6' by an adaptor 8 and butting the fibers 2, 2' on the ferrule end face 5A. Thus, both the optical fibers 1, 7 can be connected.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is an optical fiber terminal for connecting silica-based single mode optical fibers with different core diameters or relative refractive index differences between the core and cladding with low loss and low reflection. and optical connectors.

(Prior art) In the case of silica-based single mode optical fibers (hereinafter referred to as optical fibers), there are various types depending on the purpose of use, such as high relative index difference optical fibers, low relative refractive index difference optical fibers, dispersion shifted optical fibers, and rare earth-doped optical fibers. Materials with various core diameters and relative refractive index differences are in practical use. As optical communications become more sophisticated and have larger capacity, it is expected that the number of cases in which these different types of optical fibers will be interconnected will increase in the future.

When connecting silica-based single-mode optical fibers with different core diameters or relative refractive index differences, two methods are available: one is to directly butt the end faces of the optical fibers, and the other is to convert the field distribution of light propagating through the core of the optical fiber using a lens, etc. There is a way to connect.

FIG. 6 is a sectional view showing an example of the structure of an optical connector in which the end face of an optical fiber is brought into direct contact with the optical connector. In the figure, 1 and 7 are optical fibers with different core diameters or relative refractive index differences,
IA and 7A are the cores of the optical fibers 1.7, 5 and 5' are ferrules, and 6 and 6' are connector housings, respectively, housing bodies 6A, 6-A, fastening parts 6B and 6-B,
It is composed of pressing springs 6C and 6''C. 8 is an adapter, and 9 is a split sleeve. The optical fibers 1 and 7 are each adhesively fixed to the center part of a cylindrical ferrule 5.5'.
Its end face is polished together with the ferrule end face 5A to form a well-formed end face. The ferrules 5, 5' are each equipped with a connector housing 6.6', and the optical fibers 1, 7 are optically connected by abutting their smooth end surfaces including the ferrule end surface 5A via an adapter 8 equipped with a split sleeve 9. has been done.

FIG. 7 is a sectional view showing an example of the structure of an optical connector that connects optical fibers by converting the field distribution of light propagating through the core of an optical fiber using a lens. In the figure, the same components as those in FIG. 6 are denoted by the same reference numerals, and the explanation thereof will be omitted. In the figure, 10 and 10- are rod lenses, and optical fibers 1 and 7
After being adhered or fused to the ferrule 5.5', the end face is polished. The collimated light 11 or 12 emitted from the optical fiber 1 or 7 is transmitted to each rod lens 10. The field distribution is transformed by ICI,
As in the case of FIG. 6, they are optically connected at the ferrule end face 5A.

(Problem to be solved by the invention) The conventional example described above had the following problems.

First, in the method shown in Fig. 6, in which the end faces of optical fibers are connected by directly abutting each other, the field distribution of the propagating light mode differs depending on the difference in core diameter or relative refractive index difference. ) The mismatch in field distribution is not absorbed at all at the end face 5A of the 7-work rule, resulting in a large connection loss.

On the other hand, in the method of connecting optical fibers with different core diameters or relative refractive index differences by converting the field distribution of light propagating through the core of the optical fiber using a lens shown in Fig. 7, the ferrule end face, which is the fiber connecting surface, 5A absorbs field distribution mismatch, reducing splice loss. However, if the field distributions of optical fiber 1 and optical fiber 7 are significantly different, the lens constant and pitch of lens 10.1CI should be adjusted to suit each light beam. It must be selected according to the fiber.

Therefore, when manufacturing a connecting element such as an optical connector, the lens portion is limited by the optical fiber used, and the lens pitch must be adjusted with high precision, which poses problems in productivity and economy.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an optical fiber terminal and an optical connector that connect silica-based single mode optical fibers having different core diameters or relative refractive index differences with each other with low loss and low reflection.

(Means for Solving the Problems) In order to solve the above problems, in the optical fiber terminal of claim (1), the core or cladding is doped with a doping agent, and the core diameter or relative refractive index difference between the core and the cladding is fused and spliced silica-based single mode optical fibers with different values, and locally heated the vicinity of the fusion spliced part in a non-melting temperature range of the optical fiber to diffuse the doping agent in the vicinity of the fusion spliced part. The optical fiber has a smooth end surface in a portion of the optical fiber other than the heating diffusion portion of the doping agent. In the optical fiber terminal of claim (2), silica-based single mode optical fibers whose cores or claddings are doped with a doping agent and whose core diameters or relative refractive index differences between the core and the cladding are different are fusion-spliced,
The optical fiber has an optical fiber in which the vicinity of the fusion splice is locally heated in a non-melting temperature range of the optical fiber to diffuse the doping agent in the vicinity of the fusion splice, and the doping agent is heated and diffused in the optical fiber. The section or the fusion spliced section was made into a regular end surface. In claim (3), claim (1) or (2)
) has a ferrule around the outer periphery of the optical fiber, and the smoothed end surface includes the end surface of the ferrule. In claim (4), claim (1) or (2)
The described optical fiber terminals are of the same type and form a pair of connectors. In claim (5), the optical fiber terminal according to claim (1) and the optical fiber terminal according to claim (2) form a pair of connectors.

(Function) According to claims (1) and (3), since the position of the end face of the optical fiber terminal is the part where the doping agent is not heated and diffused, it is determined by the core diameter and relative refractive index difference of one optical fiber. The signal light that propagates with a fixed regular field distribution undergoes asymptotically transforming the field distribution in the doping agent diffusion area near the fusion part, and then reaches the other optical fiber, where the doping agent is diffused. In the process of reaching the part where the optical fiber is not located, the field converges and propagates into a regular field distribution determined by the core diameter and relative refractive index difference of the other optical fiber. As a result, at the optical fiber terminal, the signal light propagates through optical fibers with different core diameters or relative refractive index differences with low loss and low reflection because the mismatch in field distribution is suppressed due to the doping agent diffusion part. I can do things.

According to claims (2) and (3), since the position of the smoothed end surface is the heat-diffused part or the fusion splicing part of the doping agent, the core of the part that has not been heat-diffused is adjusted by the core diameter and the relative refractive index difference. When the signal light propagating with a fixed regular field distribution reaches the vicinity of the well-aligned surface, that is, the area where the doping agent is diffused, the field distribution is asymptotically expanded to low loss and low reflection, and the signal light is fused. The field distribution almost matches that of the diffusion section of the other fiber, resulting in a well-aligned end surface.

The effects of claims (4) and (5) will be described under the following definitions.

First, the optical fiber on the end face side of the optical fiber terminal whose end face is not heated and diffused is called the γ fiber, and the optical fiber end whose end face is fused to the γ fiber is the α fiber is called the A terminal. An optical fiber terminal in which the optical fiber fused to the fiber is a β fiber is referred to as an A' terminal. On the other hand, an optical fiber terminal in which α and β fibers are fused and the end surface is at the heated and diffused position near the fused part, and the one containing the α fiber is the B terminal, and the one containing the β fiber is the optical fiber terminal. Let be terminal B'. In addition, α,
It is assumed that the β and γ fibers are optical fibers having different core diameters or relative refractive index differences.

As a result, there are four types of combinations for connecting different types of optical fibers using the above-mentioned optical connector in which the trimmed surfaces of the optical fiber terminals are brought into contact with each other, and the function of each of them will be described below.

First, in the case of the A terminal and the A-terminal, there is no mismatch in the optical field distribution because the signal light propagates uniformly through the same γ fiber at the abutting portion of the optical fiber terminal. Therefore, the α fiber and β fiber can be connected with low loss and low reflection. In addition, in the case of the B terminal and B-terminal, since the α fiber and the β fiber are fused and heated and diffused when the terminal is made, there is no mismatch in the field distribution of the signal light on the terminal abutting surface, resulting in low loss. In addition, α fiber and β fiber can be connected with low reflection. In the case of A terminal and B' terminal or A' terminal and B terminal, the field distribution of the signal light in the γ fiber of A terminal or A' terminal and the α or β fiber of B' terminal or B terminal. In a state where there is no mismatch in the field distribution in the diffusion section, the α fiber and the β fiber are connected with low loss and low reflection.

(Example 1) A first example of the present invention will be described using FIGS. 1 to 3.

FIG. 1 is a cross-sectional view showing the structure of an embodiment of an optical fiber terminal according to the present invention, FIG. 2 is a cross-sectional view showing the structure of an optical connector according to the present invention, and FIG. It is a figure which shows the manufacturing process of the optical fiber terminal used for an Example.

In the figure, 1, 2゜2' and 7 are respectively core IA,
2A, 2=A, 7A optical fibers with different diameters or relative refractive index differences, 3 and 3' are fusion parts, 4 and 4' are core doping agent diffusion parts, 5 and 5' are ferrules, 6 and 6 ' is a connector housing, each housing body 6A.

It is composed of a 6'A1 fastening portion 6B and a 6'B1 pressing spring 6C16'C. 8 is an adapter, 9 is a split sleeve, 1
3 is an optical fiber terminal, and 14 is an optical connector.

First, the manufacturing process of the optical fiber terminal used in this example will be explained using FIGS. 3(A) and 3(B). First, the third
As shown in Figure (A), optical fibers 1°2 having different diameters of diameters IA and 2A or relative refractive index differences are fusion spliced. Thereafter, the vicinity of the fused portion 3 of the optical fibers 1 and 2 is heated by a burner, laser, heater, or electric discharge at a temperature range in which the optical fiber does not melt but the doping agent contained in the core IA, 2A or the cladding IB, 2B diffuses. By heating locally, a doping agent diffusion region 4 is created.

After cutting the optical fiber manufactured as described above at a portion away from the doping agent diffusion part 4 of the two optical fibers, the ferrule 5 is attached to the optical fibers 1 and 2 at a position where the end surface thereof slightly protrudes from the end surface of the ferrule 5. The optical fiber terminal 13 shown in FIG. 1 is obtained by adhesively fixing it and polishing it together with the ferrule end face 5A to form a well-formed end surface.

Next, the functions of the optical fiber terminal 13 will be explained using FIG. In the figure, the optical fiber terminal is provided with a connector housing 6 consisting of a housing body 6A, a fastening portion 6B, and a pressing spring 6C so as to be used for the optical connector 14 in FIG. First, the signal light propagates from the optical fiber 1 side with a regular field distribution determined by the relative refractive index difference between the core IA and the cladding IB, and the field distribution becomes asymptotically in the doping agent diffusion part 4 near the fusion part 3. After being coupled to the optical fiber 2 while being converted, the core 2A and cladding 2B of the optical fiber 2 reach the portion where the doping agent is not diffused.
It converges to a regular field distribution determined by the relative refractive index difference, and reaches a well-formed end surface including the ferrule end surface 5A. As a result, the signal light at the optical fiber terminal 13 can be propagated through the optical fibers 1 and 2 having different core diameters with low loss and low reflection because the mismatch in field distribution is suppressed by the doping agent diffusion section 4. can.

Furthermore, the effect when the optical fiber terminal 13 is used as the optical connector 14 will be explained using FIG. In the figure, the optical fiber terminal 13 equipped with the connector housing 6 and the optical fiber terminal 13- equipped with the connector housing 6- are fastened to the adapter 8, and the ferrules 5, 5- of the optical fiber terminal 13.13- are connected to the adapter 8. The optical fibers 2 and 2' adhesively fixed to the ferrule 5.degree. 5' are aligned by the split ribs 9 in the ferrule 8, so that the optical fibers 2 and 2' are butted against each other at the ferrule end face 5A. Furthermore, optical fiber terminal 1
Optical fibers 1 and 7 of 3.13' have different core diameters or relative refractive index differences, and optical fibers 2 and 2' have the same core diameter and the same relative refractive index difference. First, the optical signal propagated from the optical fiber 1 is as explained in Fig. 1.
It reaches the optical fiber 2 with low loss and low reflection. Since the same optical fibers 2 and 2' are abutted against the ferrule end face 5A, there is no mismatch in the field distribution of propagating light, so that optical connection can be achieved with low loss and low reflection.

Further, the signal light propagates from the optical fiber 2' of the optical fiber terminal 13' to the optical fiber 7 with low loss and low reflection for the same reason as the optical fiber terminal 13. As a result, by using the optical connector 14, even if the optical fibers 1 and 7 have different core diameters or relative refractive index differences, optical connection can be achieved with low loss and low reflection. Note that the effect is the same even if the propagation direction of the optical signal is from 7 to 1.

The optical fiber terminal and optical connector in this embodiment have the following features.

The first point is that if only optical components such as light receiving or light emitting elements with lens systems compatible with the optical fiber 2 are prepared, the optical fiber terminal 13 can be used regardless of the core diameter of the optical fiber 1.
Therefore, it is possible to significantly reduce the cost of lens system components and assembly of optical components connected to the optical fiber terminal 13.

Second, in the optical fiber terminal 13, the optical fiber is cut and trimmed at a portion other than the doping agent diffusion section 4, so the optical fiber terminal can be created without being constrained by the position of the doping agent diffusion section. Therefore, the process is easy, and it is economical and mass-producible.

Furthermore, the third point is that in the optical connector 14, the optical fibers 2 to be butted are of the same type, and the smooth end surfaces including the ferrule end surfaces of the optical connectors are butted against each other in a state where the field distribution of the optical fibers 2 is converged, resulting in low loss and low loss. This means that optical fibers 1 and 7 having different core diameters or relative refractive index differences can be connected with low reflection.

In this example, the fibers 1.7 may be the same type of optical fibers, the optical fiber terminals may be trimmed by polishing or stress breaking the end face without a ferrule, and the optical connectors may be of the same type. It goes without saying that 14 may have multiple cores, and that the smooth end surface including the ferrule end surface 5A of the optical fiber terminal 13 may be polished into a convex spherical shape or inclined at a certain angle with respect to the optical axis. do not have.

(Example 2) A second embodiment of the present invention will be described based on FIG.

In the figure, optical fiber terminals 15, 15' and optical connectors 17 are created and constructed as follows. First, the optical fiber 1 and the optical fiber 7 having different core diameters or relative refractive index differences are fused and heated and diffused in the same manner as described in FIG. After cutting at the fused portion, each optical fiber is adhesively fixed to the ferrules 5, 5' and the end surfaces are polished to obtain a well-formed end surface, and the plug housing 16. 16' are respectively attached to form optical fiber terminals 15 and 15'.

Furthermore, when the optical fiber terminal 15, 15- is fastened to the attack 8, the smooth end surfaces including the ferrule end surfaces 5A of the fers 5, 5- are butted together in the split sleeve 9, and the optical connector 1
7, the optical fiber 1 and the optical fiber 7 are connected.

Next, the effect when the optical connector terminal 15, 15- is used as the optical connector 17 will be explained.

First, the signal light propagates from the optical fiber 1 side with a regular field distribution determined by the relative refractive index difference between the core and the cladding, and the field distribution is asymptotically converted and expanded in the doping agent diffusion section 4 of the optical fiber terminal 15. As the ferrule ends, it reaches a well-formed end surface including the ferrule end surface 5A.

On the finished end surface, the part that is fused and heated and diffused during the terminal fabrication is cut and trimmed, so there is no mismatch in field distribution, so the signal light is transmitted to the optical fiber terminal 15 with low loss and low reflection. It propagates to the diffusion section 4 of. Furthermore, in the process of propagating the signal light from the diffusion part 4 of the terminal 15' to the undiffused part, the field distribution is asymptotically transformed and reduced to a linear shape determined by the relative refractive index of the core and cladding of the optical fiber 7. converges to a field distribution. As a result, in the optical connector 17 using the optical fiber terminal 15.15= which cut the heated and diffused fused portion and trimmed the end, it is possible to use optical fibers μ1, 7 with different core diameters or relative refractive index differences with low loss and low reflection. can be connected. Note that the effect is the same even if the propagation direction of the optical signal is from 7 to 1.

The optical connector in this embodiment has the following features.

First, since the fused portion of different types of optical fibers is heated to diffuse the doping agent and then cut again to form a connector as a terminal, there is no mismatch in the field distribution of the signal light, so the core diameter or Optical fibers with different relative refractive index differences can be connected with low loss and low reflection.

The second point is that the field distribution is expanded due to the heating diffusion effect of the doping agent on the finished end face including the ferrule end face 5A of the optical fiber terminal, so the axis misalignment due to the loss of the optical fibers 1 and 7 occurs when connecting with the optical connector. The tolerance is relaxed compared to the optical fiber before heating and diffusion. Therefore, the accuracy of parts such as ferrules is relaxed, and it is excellent in economy and mass production.

Note that the optical fiber terminal 15 or 15 in this embodiment
'' means that it may be fitted with the optical fiber terminal 13 or 13- shown in the first embodiment to form an optical connector, and that the optical fiber terminal may be trimmed by polishing or stress breaking the end face without a ferrule. What you can do,
The optical connector 17 may have multiple fibers, and the smooth end surface of the optical fiber terminal 15 or 15', including the ferrule end surface 5A, may be polished into a convex spherical shape or tilted at a certain angle with respect to the optical axis. Needless to say.

(Example 3) A third example of the present invention will be described based on FIG. 5. FIG. 5 is a diagram showing the structure of an optical wiring board in which an optical circuit 20 using an optical waveguide or the like is mounted on a substrate 21, and input/output lines of the optical circuit 20 are wired using optical fibers. FIG. 5(A) shows a wiring board constructed using the optical connector 17 according to the present invention, and FIG. 5(B) shows a wiring board constructed using the conventional optical connector 30. In the figure, 1 is a low delta fiber with a small relative refractive index difference between the core and cladding, and 7 is a high delta fiber with a large relative refractive index difference. It is also assumed that the optical connectors 17 and 30 are fixed on the board 21.

The effects of this embodiment will be explained below. Currently, low delta fibers 1 are commonly used as optical fibers for optical transmission lines connecting devices or remote locations. However, this low Δ fiber 1 has a weak signal light confinement effect, and when the radius of curvature of the optical fiber is made small, the loss increases significantly. Therefore, Fig. 5 (B
), the wiring of the optical circuit 20 on the substrate 21 has a low Δ
If the fiber 1 is used, the fiber bending radius R must be increased, which limits the packaging density of the optical circuit 20 on the substrate 21. On the other hand, in the case of the high Δ fiber 7, since the light confinement effect is strong, the bending radius of the fiber can be made smaller than that of the low Δ fiber. Therefore, the fifth
As shown in Figure (A), an optical connector 17 according to the present invention is used to connect a low Δ fiber 1 on the transmission line side and a high Δ
By connecting the fiber 7 with low loss and low reflection, the fiber bending radius r in the wiring board can be made smaller than when using the low Δ fiber 1, so the density of the actual device 9 of the optical circuit 20 can be greatly improved. be able to.

- As explained above, in this embodiment, the optical connector 1
7 to connect optical fibers with different relative refractive index differences with low loss and low reflection, it is possible to increase the packaging density of optical circuits on the substrate and downsize the entire device.

In this embodiment, it goes without saying that the optical connector 17 may be replaced by the optical connector 14.

(Effects of the Invention) As explained above, according to claims (1) to (5), it is possible to connect silica-based single mode optical fibers with different core diameters or relative refractive index differences with low loss and low reflection, and has excellent mass productivity. We can provide optical fiber terminals and optical connectors.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of a first embodiment of an optical fiber terminal according to the present invention, FIG. 2 is a cross-sectional view showing the structure of a first embodiment of an optical connector according to the present invention, and FIG. 4 is a sectional view showing the structure of the optical fiber terminal according to the second embodiment of the present invention, and FIG. 5 is a diagram showing the structure of the optical fiber terminal according to the first and second embodiments of the present invention. FIG. 6 is a cross-sectional view showing the structure of the second embodiment of the optical connector according to the invention, FIG. 6 is a structural diagram showing the structure of the third embodiment of the optical connector according to the invention, and FIGS. It is a sectional view for explanation. In the figure, 1, 2.2-. 7... Optical fiber, 3... Fusion part, 4,4-... Doping agent diffusion part, 5.5'.
...Ferrule, 6,616.16-...Connector housing, 8...Adapter, 9...Split sleeve, 1
0.10-...Lens, 11.12...Collimated light, 13.11, 15.15=...Optical fiber terminal,
14.17.30... Optical connector, 20... Optical circuit, 21... Board. Patent applicant Nippon Telegraph and Telephone Corporation Representative Patent attorney Yoshi 1) Takashi Sei

Claims (5)

[Claims] (1) Silica-based single mode optical fibers whose cores or claddings are doped with a doping agent and whose core diameters or relative refractive index differences between the core and the cladding are different are fusion spliced, and the vicinity of the fusion spliced portion is connected to the optical fibers. The optical fiber has an optical fiber that is locally heated in a non-melting temperature range to diffuse the doping agent near the fusion spliced portion, and a portion of the optical fiber other than the heated diffusion portion of the doping agent is formed into a smooth end surface. An optical fiber terminal characterized by: (2) Fusion-splicing silica-based single-mode optical fibers whose cores or claddings are doped with a doping agent and having different core diameters or relative refractive index differences between the core and cladding, and connecting the vicinity of the fusion-spliced portion to the optical fiber. The optical fiber has an optical fiber which is locally heated in a non-melting temperature range to diffuse the doping agent near the fusion spliced part, and the part where the doping agent is heated and diffused or the fusion spliced part of the optical fiber is formed as a smooth end surface. An optical fiber terminal characterized by: (3) The optical fiber terminal according to claim (1) or (2), wherein a ferrule is provided on the outer periphery of the optical fiber, and the end face includes an end face of the ferrule. (4) An optical connector characterized in that the optical fiber terminals according to claim (1) or (2) are of the same type and form a pair of connectors. (5) The optical fiber terminal described in claim (1) and claim (2)
) An optical connector characterized in that the optical fiber terminals described in ) form a pair of connectors.