JP2873099B2 - Optical star coupler and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical star coupler used for an optical fiber communication system, an optical fiber sensor, an optical measurement and the like, and a method for manufacturing the same. The present invention relates to an optical star coupler and a method for manufacturing the same.

[0002]

2. Description of the Related Art Hitherto, in an optical communication system or the like, an optical star coupler for splitting transmission light into a plurality of ports or merging light incident from a plurality of ports has been used. . In particular, as shown in JP-A-61-65204 and JP-A-61-113008, an optical star coupler manufactured by fusing and stretching a plurality of optical fibers at a time has a low loss and is difficult to use in an optical transmission line. It attracts attention because of its good compatibility with certain optical fibers and its ease of fabrication. However, in this type of optical star coupler, the distribution characteristics are apt to vary, and not only the yield is poor, but also various optical characteristics (branch ratio, excess loss, etc.) have wavelength dependence, so that wavelength multiplexing using a plurality of wavelengths is required. It could not be used in communication systems.

[0003] In recent years, studies have been conducted on fiber-fused optical fiber couplers with reduced wavelength dependence. This type of optical fiber coupler can be used in a wide band due to its reduced wavelength dependence. Also called a coupler. A method for reducing the wavelength dependence is disclosed in US Pat.
It is well known that this can be realized by providing a difference between the propagation constants of a plurality of optical fibers as disclosed in US Pat. In general, as disclosed in US Pat. No. 4,798,438, one optical fiber is drawn in advance and then fused and drawn with the other optical fiber to provide a difference in the propagation constant between the two optical fibers. The stretching method is used.

[0004] However, a wide-band optical star coupler using such a propagation constant difference has a principle of 4 ports (2 ×).
It is difficult to realize only in 2). To configure an optical star coupler using this, for example, 8 ports (4 ×
When configuring the optical star coupler of 4), as shown in FIG.
A coupling portion must be formed continuously from the optical fibers 1, 2, 3, and 4, or four broadband optical fiber couplers must be prepared in advance and the ports of each coupler must be fused and connected. However, this has the drawback that the configuration of the device is complicated and large, and the excess loss of the entire device is increased due to the loss due to fusion splicing. FIG. 5 shows a state in which each connecting portion is stored and fixed in the storage member 30.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an optical star coupler having a small size and low wavelength dependence of various optical characteristics and a method of manufacturing the same.

[0006]

According to the present invention, in order to solve the above-mentioned problems, a part of any two of a plurality of optical fibers is fused and drawn to sequentially form a joint. In this optical star coupler, each of the optical fibers is an optical star coupler in which a coupling portion is formed by sequentially fusing and extending an optical fiber arranged adjacent and parallel in a horizontal position and a vertical position.

Further, each of the optical fibers is an optical star coupler which is an optical fiber having a different refractive index distribution from the optical fibers arranged adjacent and parallel at the horizontal position and the vertical position. In addition, the sequentially formed connecting portions are held by one fixing member or storage member.

In the method of manufacturing an optical star coupler according to the present invention, a step of arranging four optical fibers in two stages of upper and lower two adjacent and parallel to other optical fibers at a horizontal position and a vertical position, respectively. Forming a first coupling portion by fusing and extending one of the two sets of optical fibers that are adjacent and parallel in the horizontal position and the vertical position, and the other in the adjacent parallel relationship. A step of fusing and stretching each of the two sets of optical fibers at a position separated by a predetermined distance from the first coupling portion to form a second coupling portion.

Further, in the above-mentioned manufacturing method of the present invention, in the step of forming the first coupling portion, one pair of the optical fibers which are adjacent to each other at the horizontal position and the vertical position are fused. In the step of pre-drawing the other pair of optical fibers in the adjacent and parallel relationship at the fusion drawing position before being drawn and drawn, and the step of forming the second joint portion, Before the other two sets of optical fibers having the following relationship are fused and drawn at positions separated by a predetermined distance from the first coupling portion, the one set of optical fibers having the adjacent parallel relation is The manufacturing method includes a step of stretching in advance at a position separated by the predetermined interval.

[0010]

The optical star coupler of the present invention is compact because each optical fiber is sequentially fused and stretched with the optical fibers arranged adjacent and parallel at the horizontal position and the vertical position to form a joint. If each of the optical fibers is an optical fiber having a different refractive index distribution from the optical fibers arranged adjacent and parallel in the horizontal position and the vertical position, respectively, a difference in propagation constant occurs, and each coupling portion has low loss and various optical characteristics. Can be reduced in wavelength dependence. Further, by holding the joints formed by successive fusion stretching with a single fixing member or a storage member, the structure is simple, small, and extremely reliable.

Further, according to the manufacturing method of the present invention, for example, 4 × 4 × 4 input ports and 4 output ports using four optical fibers.
Optical star couplers can be manufactured in a series of steps. Further, following the manufacturing process of the 4 × 4 optical star coupler,
If four new optical fibers are combined with each of the four optical fibers at the output port of the optical star coupler, and the manufacturing method of the present invention is used, a 4 × 16 optical star coupler can be easily formed by a series of manufacturing steps. Therefore, according to the manufacturing method of the present invention, a 4 × 4 ⁿ optical star coupler (n ≧ 1) can be constituted by a series of manufacturing steps.

Further, since one of the optical fibers is pre-drawn before the fusion-drawing at the portion where the joint is formed in the manufacturing process, there is provided a difference in the propagation constant between the two optical fibers to be fusion-drawn. An optical star coupler with reduced wavelength dependence can be formed by a series of manufacturing steps.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical star coupler according to the present invention will be described below with reference to FIGS. FIG. 1A shows an embodiment of a 4 × 4 optical star coupler having four input ports and four output ports as a basic configuration of the present invention. Reference numerals 1 to 4 denote the optical fibers from which the coating has been removed. The upper stage comprises two optical fibers 1 and 2 and the lower stage comprises two optical fibers 3 and 4. The optical fibers 1 and 2 and 3 and 4 are fused and drawn, respectively. First coupling portions 10 and 10 are formed, and second coupling portions 20 and 20 are formed by fusing and stretching optical fibers 1 and 3 and 2 and 4 respectively at portions separated from the first coupling portion by a predetermined distance. doing. As a result, the optical signal incident from the optical fiber 1 is divided into two by the first coupling part 10 and further divided into two by the second coupling parts 20 and 20 and distributed to four ports on the emission side.

Next, FIG. 1 (B) shows an input 4 port of the present invention,
In the embodiment of the 4 × 16 optical star coupler having 16 output ports,
Each of the optical fibers 1, 2, 3, and 4 of the output side port has a 4 × 4 optical star coupler as a basic configuration.
4 × 16 optical star due to the construction of × 4 optical star coupler
A coupler has been realized. That is, the optical fiber 1 of the output side port of the 4 × 4 optical star coupler and the new optical fibers 5, 6, 7 are arranged in the upper stage and the lower stage in the same manner as described above, and the joining portions are sequentially formed by fusing and stretching. Thus, a 4 × 4 optical star coupler is realized, and the other optical fibers 2, 3, and 4 are similarly configured as 4 × 4 optical star couplers, thereby realizing a 4 × 16 optical star coupler.

Thus, for example, a 4 × 4 ⁿ optical star coupler with n = 3 is a 4 × 4 optical star coupler for each of the 16 optical fibers at the output port of the 4 × 16 optical star coupler. It can be realized by configuring. . Furthermore, n ≧
The 3 × 4 ⁿ optical star coupler can be easily realized by configuring a 4 × 4 optical star coupler in the same manner as described above for each optical fiber of the output port of the coupler.

As described above, according to the present invention, a 4 × 4 optical star coupler is centered, and a 4 × 4 optical star coupler is sequentially fused and drawn for each optical fiber at the output port thereof to form a coupling portion. 4 × 4 ⁿ optical star coupler (n
≧ 1) can be realized.

As shown in FIGS. 2A and 2B,
By forming adjacent optical fibers as optical fibers a and b having different refractive index distributions and forming bonding portions under appropriate fusion-stretching conditions, it is possible to reduce the wavelength dependence of each bonding portion. A star coupler can be configured.

Further, by fixing each coupling portion to the same fixed substrate or storing it in the same storage body, each coupling portion can be protected, and a compact and highly reliable optical star coupler can be realized.

FIG. 3 is a process chart showing the first method of manufacturing the above 4 × 4 ⁿ optical star coupler for each of the steps a), b) and c). () Is a top view of four aligned optical fibers, and (b) is a side view thereof.

First, a method of manufacturing a 4 × 4 optical star coupler which is a basic configuration of the present invention will be described. First, the four optical fibers 1, 2, 3, and 4 are aligned in two stages, namely, the optical fibers 1 and 2 in the upper stage and the optical fibers 3 and 4 in the lower stage (FIG. 3).
I)). After the alignment, arbitrary adjacent optical fibers 1 and 2 and 3 and 4 are fused and drawn using a heating means such as an oxyhydrogen burner to form first joints 10 and 10 (FIG. 3B)). . Further, the optical fibers 1 and 3 and 2 and 4 adjacent to each other, which are different in combination with the first coupling portions 10 and 10, are respectively fused and stretched at predetermined intervals from the first coupling portions 10 and 10 to form the second optical fibers. The joints 20 are formed and completed (FIG. 3B).

Next, the method of manufacturing a 4 × 4 ⁿ optical star coupler with n ≧ 2 is based on the above 4 × 4 optical star coupler, and three new optical fibers are individually connected to each of the optical fibers at the output port. An optical fiber may be added to form a 4 × 4 optical star coupler in the order shown in FIGS.

In the case of this manufacturing method, it is possible to reduce the wavelength dependence of each joint by forming the joints under appropriate fusion-stretching conditions while varying the refractive index distribution of the adjacent optical fibers. Thus, a wideband optical star coupler can be formed.

FIG. 4 is a process chart showing the second method of manufacturing the optical star coupler according to the present invention in each of the steps a), b), d) and e). (a) is a top view of four aligned optical fibers, and (b) is a side view thereof.

First, a method of manufacturing a 4 × 4 optical star coupler, which is a basic configuration of the present invention as described above, will be described. First, four optical fibers 1, 2, 3, and 4 of the same quality are aligned in two stages of optical fibers 1 and 2 in the upper stage and optical fibers 3 and 4 in the lower stage (FIG. 4A)). After the alignment, any two adjacent optical fibers 1 and 3 are simultaneously pre-stretched using a heating means such as an oxyhydrogen burner (FIG. 4B). The fibers 1 and 2, 3 and 4 are simultaneously fused and drawn to form first joints 10 and 10 (FIG. 4C)). Next, arbitrary combinations 1 and 2 of the combinations of the optical fibers 1 and 2, 3 and 4 that have been fusion-stretched are simultaneously pre-drawn at a predetermined distance from the first coupling portion 10 in the same manner as above. (FIG. 4D)), the pre-stretched portions are simultaneously fused and drawn with different combinations of adjacent optical fibers 1, 3, 2, and 4, respectively, to complete the second joint portions 20, 20. (FIG. 4E)).

Further, the method of manufacturing a 4 × 4 ⁿ optical star coupler with n ≧ 2 is based on the above 4 × 4 optical star coupler, and three new optical fibers are provided for each optical fiber at the output port of the coupler. A 4 × 4 optical star coupler may be sequentially formed by the steps of FIGS. As described above, according to the second manufacturing method of the present invention, since the pre-drawing method is used, a 4 × 4 ⁿ optical star coupler with a reduced wavelength dependency can be easily formed from optical fibers of the same quality.

The size of the package in which the 4 × 4 optical star coupler constructed in the manner described above is housed and fixed in one housing member is φ5 × 65 mm, which is almost the same as the size of the conventional 2 × 2 optical fiber coupler. In terms of size, its optical characteristics also have an excess loss of 0.5 dB or less, and a branching ratio variation of ± 5.
%, And the wavelength dependency can be easily configured by controlling the type of fiber, the conditions of pre-stretching, and the like.

In the above example, the 4 × ⁴ⁿ optical star coupler is used in consideration of the case where all four optical fibers on the incident side are used. However, one or two of the four optical fibers on the incident side are used.
1 × 4 ⁿ or 2 × 4 using only books as input ports
Naturally, it can be used as an ^n- star coupler.
In this case, the first coupling portion 10 can be constituted by only one.

[0028]

The optical star coupler of the present invention is small in size since each optical fiber is sequentially fused and stretched with the optical fiber arranged adjacent and parallel at the horizontal position and the vertical position to form a joint. Furthermore, if each optical fiber is an optical fiber having a different refractive index distribution from the optical fiber arranged adjacent and parallel in each of the horizontal position and the vertical position, a difference in propagation constant occurs, and each coupling portion has low loss and various optical fibers. A broadband optical star coupler with reduced wavelength dependence of characteristics is obtained. Further, by holding the joints formed by successive fusion stretching with a single fixing member or a storage member, the structure is simple, small, and extremely reliable.

Further, according to the manufacturing method of the present invention, the optical star coupler of the present invention can be manufactured very easily and with good yield in a series of manufacturing steps. Furthermore, since it is possible to use the pre-stretching method in the manufacturing process, a wide-band optical star coupler with reduced wavelength dependency can be produced with a very easy yield in a series of manufacturing processes using optical fibers of the same quality. Can be reliably manufactured. Therefore, according to the present invention, an optical star coupler having a small size, a simple configuration, and extremely high reliability can be provided at low cost.

[Brief description of the drawings]

FIGS. 1A and 1B are perspective views each showing an embodiment of an optical star coupler of the present invention.

FIGS. 2A and 2B are cross-sectional views of an optical star coupler according to another embodiment of the present invention.

FIGS. 3A and 3B are process diagrams showing a first method for manufacturing an optical star coupler according to the present invention, and in each process diagram of FIGS. Fiber top view,
(B) is a side view thereof.

FIGS. 4 (a) to 4 (e) are process diagrams showing a second method for producing the optical star coupler of the present invention, and (a) is aligned in each of the process diagrams (a) to (e). FIG. 4B is a top view of the four optical fibers, and FIG.

FIG. 5 is a conceptual diagram of a conventional 4 × 4 optical star coupler.

[Explanation of symbols]

 1,2,3,4,5,6,7 Optical fiber 10,10 First coupling part 20,20 Second coupling part

Claims (5)

(57) [Claims] 1. An optical star coupler in which a part of any two optical fibers of a plurality of optical fibers is fusion-stretched to form a coupling portion in order, each of the optical fibers being located in a horizontal position and a vertical position. Wherein the optical fiber is sequentially fused and drawn with the optical fibers arranged adjacently in parallel to form a coupling portion. 2. The optical star coupler according to claim 1, wherein each of the optical fibers is an optical fiber having a different refractive index distribution from the optical fibers arranged adjacent and parallel at the horizontal position and the vertical position. . 3. The optical star coupler according to claim 1, wherein the sequentially formed coupling portions are held by one fixing member or a storage member. 4. A step of arranging four optical fibers in two stages of upper and lower two adjacent and parallel to another optical fiber at a horizontal position and a vertical position, respectively, and adjacent at the horizontal position and the vertical position. A step of fusing and stretching each of the two sets of optical fibers in a parallel relationship to form a first coupling portion; and the other two sets of optical fibers in the adjacent parallel relationship being the first pair. Forming a second joint portion by fusing and stretching each at a position separated by a predetermined distance from the joint portion. 5. In the step of forming the first coupling portion according to claim 4, one of the two sets of optical fibers that are adjacent and parallel to each other at the horizontal position and the vertical position are fusion-spread, respectively. Before, a step of pre-drawing the other pair of optical fibers in the adjacent parallel relationship at the fusion-spreading position;
In the step of forming the second coupling portion, before the other two sets of optical fibers in the adjacent parallel relationship are fused and drawn at positions separated by a predetermined distance from the first coupling portion, respectively. 5. The method for manufacturing an optical star coupler according to claim 4, further comprising the step of pre-drawing the one set of optical fibers having the adjacent parallel relationship at a position separated by the predetermined distance.